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Speaker 1: Get technology with tech Stuff from dot Com. Hey there,

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Speaker 1: and welcome to tech Stuff. I am your host, Jonathan Strickland.

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Speaker 1: I'm a senior writer win how Stuff Works dot Com,

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Speaker 1: and sometimes my voice cracks for no reason. Today we're

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Speaker 1: going to continue our journey into the scary world of

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Speaker 1: weather forecasting. Uh. I say scary because weather is a

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Speaker 1: powerful thing. It can bring with it some pretty intense

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Speaker 1: uh storms and and win things like that. I mean,

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Speaker 1: obviously you can have nice weather too, but who wants

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Speaker 1: to talk about that? I mean, you're not gonna have

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Speaker 1: an emergency weather broadcast burst into your favorite viewing time

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Speaker 1: of watching ALF and say warning, things are gonna be

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Speaker 1: really nice this afternoon. So we're gonna talk about today

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Speaker 1: about some of the tools that meteorologists use in order

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Speaker 1: to get information about what's going on at this very

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Speaker 1: moment as far as the weather is concerned. In our

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Speaker 1: last episode, we covered the basics of how weather works,

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Speaker 1: so that man, it was more of a science based show,

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Speaker 1: less technology, but it was important so that we can

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Speaker 1: build the foundation to understand why meteorology is so incredibly

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Speaker 1: complicated and so process or heavy. Like when you talk

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Speaker 1: about supercomputers. One of the main uses for supercomputers these

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Speaker 1: days is to run weather models. And that's because you're

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Speaker 1: talking about an enormous amount of data that has to

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Speaker 1: be processed running you know, various types of calculations on

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Speaker 1: it in order to create the outputs that we use

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Speaker 1: for weather forecasts. And as our weather models become more

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Speaker 1: and more high resolution, more precise, using more more readings

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Speaker 1: per hour, that demand of processing power increases quite a bit.

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Speaker 1: So let's talk about just the stuff that meteorologists used

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Speaker 1: to gather that data. This isn't even about the weather models.

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Speaker 1: In our next episode, we will cover how weather models work,

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Speaker 1: because it's fascinating all in its own. Today we're gonna

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Speaker 1: focus on the stuff that meteorologists used to get the

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Speaker 1: data that feeds into those weather models. Uh So, meteorologists

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Speaker 1: do a few different things. They do make observations of

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Speaker 1: current weather conditions, so they're telling you what's happening right now,

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Speaker 1: and that's what I'm focusing on for this episode and

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Speaker 1: the next one will look more at the forecasting side.

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Speaker 1: How do they actually predict what will happen next. Observations

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Speaker 1: let you know the current conditions. They include data like

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Speaker 1: wind speed, wind direction, air pressure, temperature, humidity, u V,

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Speaker 1: radiation numbers, smog fog, all of these things and more.

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Speaker 1: Are you need observation stations throughout any given region, the

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Speaker 1: region that you are responsible for, let's say, and you

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Speaker 1: need to have a lot of them in order for

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Speaker 1: you to get a more complete picture of what is

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Speaker 1: really actually happening. If you have only a few observation points,

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Speaker 1: then you would have what we would call low resolution.

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Speaker 1: You would not have a very accurate accurate view of

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Speaker 1: what was going on within the region, unless your region

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Speaker 1: is particularly small. Let's say that you are responsible for

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Speaker 1: gathering the information across an entire county. Well, a county

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Speaker 1: could be lots of square mileage, and depending upon where

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Speaker 1: your observation stations are, you might have information that's very

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Speaker 1: relevant for a specific part of that county, but it

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Speaker 1: might not be so relevant for other parts of the county.

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Speaker 1: And yet you have to create weather forecasts based on

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Speaker 1: your observations. It means the further out you go from

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Speaker 1: those observation stations, the less reliable that data is going

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Speaker 1: to be because it may not reflect what the actual

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Speaker 1: conditions are further away from those observation stations. So having

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Speaker 1: a high density of observation stations is critical for having

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Speaker 1: very precise, whether a picture of what's going on with

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Speaker 1: the weather and thus making more accurate weather forecasts. So

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Speaker 1: it could cause a problem, right Like, you could end

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Speaker 1: up giving a weather forecast that ends up being useless

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Speaker 1: for a significant percentage of the people who are relying

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Speaker 1: upon your weather forecasts if they happen to live far

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Speaker 1: away from where your observation stations are. So let's think

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Speaker 1: of this in more concrete terms and you'll really understand

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Speaker 1: how this can become a problem. Let's say that you

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Speaker 1: have a region that includes some different areas within with

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Speaker 1: different levels of elevation. So let's say that you're at

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Speaker 1: the foothills of a mountain range. Well, we'll say this

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Speaker 1: the appal Achians. So, uh, I live in Atlanta, Georgia,

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Speaker 1: where on what is called the Piedmont it is h

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Speaker 1: hilly but not mountainous area. If I were further northeast

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Speaker 1: of here, or even just further north of here, I

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Speaker 1: would start getting into the foothills of the Appalachian Mountains.

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Speaker 1: So let's say that I'm on Just like that, I'm

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Speaker 1: looking at a region where it's covering the end of

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Speaker 1: the Piedmont into the foothills. That's several different areas of

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Speaker 1: different elevation. That means that those different areas are going

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Speaker 1: to experience different weather patterns because weather is all about

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Speaker 1: atmospheric movement and things that are going on within the atmosphere.

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Speaker 1: Atmosphere is going to move over the topographical features of

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Speaker 1: any given region, the geography, and with hills and mountains,

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Speaker 1: that means the weather is going to do different things

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Speaker 1: in those different areas. So you're going to have folks

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Speaker 1: checking the weather report and wondering why it says there's

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Speaker 1: no chance brain while they're being rained on, and it

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Speaker 1: may be because they live on the opposite side of

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Speaker 1: a mountain from where you are with your observation stations,

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Speaker 1: and at the observation stations everything's bone dry because that's

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Speaker 1: what you know, that's what you've based your forecast on,

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Speaker 1: because that was where the data was coming from. But

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Speaker 1: on the other side of the mountain, because you've had

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Speaker 1: warm air masses pushed up to higher elevations as they

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Speaker 1: moved over a mountain, They've then cooled down, water has condensed,

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Speaker 1: and precipitation has begun to fall. People on the other

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Speaker 1: side of the mountain they get rained on, and yet

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Speaker 1: they're living in that same region that's being covered by you,

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Speaker 1: because that's the county they are in, or the zip code.

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Speaker 1: This is why it gets really problematic when you start

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Speaker 1: making weather forecasts, because they depend so heavily upon the

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Speaker 1: geography of the respective regions and the geography and and

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Speaker 1: observation stations within that geography. Now, if you have observation

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Speaker 1: stations throughout your area, you can give much more precise

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Speaker 1: weather forecasts. And say, in this part of the county,

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Speaker 1: you would expect conditions to be dry, but up here

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Speaker 1: over in the mountains, you're gonna start seeing some rain.

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Speaker 1: So you start seeing where the complexity comes into play.

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Speaker 1: And this is a very small scale example of this problem.

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Speaker 1: Once you start looking at it from say a statewide

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Speaker 1: or nationwide or global perspective, you begin to realize this

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Speaker 1: is really complicated stuff, and this is a big challenge

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Speaker 1: for meteorologists. You might notice that many weather apps allow

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Speaker 1: you to search for weather forecasts by zip codes, but again,

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Speaker 1: zip codes do not necessarily conform to geography, and you

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Speaker 1: could have lots of different geographic regions within a single

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Speaker 1: zip code, and that means that the weather forecast for

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Speaker 1: one of those parts of the zip code may not

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Speaker 1: be accurate for all the other parts. So if I

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Speaker 1: check my app and it says hey, it's gonna rain,

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Speaker 1: and I step outside and it's sunny, I might think, well,

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Speaker 1: what the heck is wrong with this weather forecast app? Again,

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Speaker 1: they have to try and give you a forecast that's

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Speaker 1: going to be relevant for the entire zip code, even

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Speaker 1: if different parts of that zip code are in different

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Speaker 1: geographical regions, like different geographical features mountains or streams or

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Speaker 1: lakes or ocean or whatever it may be. So you

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Speaker 1: can't really take all that into account if your criteria

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Speaker 1: for generating a forecast is based solely upon zip codes.

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Speaker 1: That's why a lot of different weather apps and services

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Speaker 1: are now using geolocation data to give you a more

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Speaker 1: precise weather forecast for your your requests. So, if you're

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Speaker 1: carrying a mobile device and you have a weather app

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Speaker 1: on it and it's asking hey, can I have access

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Speaker 1: to your GPS or location data? If you say yes,

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Speaker 1: then the weather app can look for your location and

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Speaker 1: try and base the forecast for you closer to observation

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Speaker 1: stations that are relevant to your your actual location So

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Speaker 1: if I happen to be in a part of the

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Speaker 1: county that is not the main population center and thus

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Speaker 1: not the place that the forecast is really gonna cater to,

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Speaker 1: I might get something more personalized saying, hey, well, based

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Speaker 1: upon where you are, you're gonna be Charlie Brown and

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Speaker 1: have a little cloud follow you all day raining just

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Speaker 1: on you, which has never quite happened to me, but

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Speaker 1: some days it feels that way. It's sidesteps that zip

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Speaker 1: code problem, so that the weather forecasting system can consult

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Speaker 1: the observation stations really closest to you at that time

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Speaker 1: and to project weather based upon that. But even then

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Speaker 1: you can still run into issues. So, for example, if

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Speaker 1: you happen to be closest to an airport observation station,

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Speaker 1: I mean most really all airports have some form of

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Speaker 1: meteorological meteor logical boy man, that's gonna be a lot

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Speaker 1: of fun today. Meteorological observation stations. Almost all air airports

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Speaker 1: have at least some element of that, because clearly the

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Speaker 1: weather conditions are very important when it comes to air travel.

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Speaker 1: One problem with that is that airports have very big

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Speaker 1: runways and uh tarmax things that absorb a lot of

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Speaker 1: heat and give off a lot of heat, more so

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Speaker 1: than the surrounding area. And as we learned in our

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Speaker 1: last episode, heat is a big important factor when it

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Speaker 1: comes to impacting weather systems. So if you happen to

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Speaker 1: be close to an airport, that might end up throwing

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Speaker 1: off some of the readings that you would get because

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Speaker 1: it has this island effect right at the airport, But

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Speaker 1: that might not extend very far outside of the airport's borders.

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Speaker 1: So while you're getting observation data that's close to you,

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Speaker 1: it may still not be relevant to you. A lot

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Speaker 1: of this sounds like I'm apologizing for weather forecasts that

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Speaker 1: aren't entirely accurate, and I guess you could argue that

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Speaker 1: I kind of am. But mostly what I want to

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Speaker 1: stress is just, um, what a tough job this is.

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Speaker 1: It's an interesting and fascinating thing, and we've learned so

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Speaker 1: much about atmospheric fluid dynamics and just how weather works

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Speaker 1: in general as a result of lots and lots of

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Speaker 1: men and women putting their heads together and and making

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Speaker 1: observations and sussing all this out. But it's still really

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Speaker 1: really hard to do, which is why it's one of

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Speaker 1: the reasons why we don't do it perfectly now. Besides resolution,

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Speaker 1: as in how many observation stations you have within a

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Speaker 1: given region, you have to take those observations frequently. This

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Speaker 1: helps with precision. If you take one observation in the day,

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Speaker 1: early in the day, and that's it, then you can't

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Speaker 1: take into account any changes that happen afterward, which means

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Speaker 1: that you can never really update your forecast. And that

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Speaker 1: means that the further away you get in time from

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Speaker 1: that initial observation, the less precise and accurate your forecast

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Speaker 1: is going to be. If you continuously or at least

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Speaker 1: regularly take observations, you can then update your forecast as

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Speaker 1: a result when conditions change, and that way you can

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Speaker 1: keep your at least your immediate forecast more accurate. You

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Speaker 1: may notice that the further out you go from the

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Speaker 1: point of forecast from the current time, the less accurate

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Speaker 1: these forecasts tend to tend to be. So if you're

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Speaker 1: looking at a date that's ten days out, it might

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Speaker 1: be more or less right on the money, or maybe

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Speaker 1: way off base. Because weather is again very complicated and

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Speaker 1: constantly changing. Uh So you want to make sure that

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Speaker 1: the information you're relying on doesn't age so much as

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Speaker 1: to be irrelevant. So you need lots of observation stations.

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Speaker 1: You need to take a lot of observations per given

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Speaker 1: unit of time, and the combination of those two requirements

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Speaker 1: means that you are generating an enormous amount of data

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Speaker 1: that then has to go someplace and then be processed

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Speaker 1: for you to get forecasts. This is why you need

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Speaker 1: those hefty computers like supercomputers to process meteorological data. And

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Speaker 1: more on that in the next episode. But first let's

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Speaker 1: talk about some of the basic instruments these meteorologists are

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Speaker 1: using to gather actual weather data. Then in our next

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Speaker 1: episode will move on to how they use that to

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Speaker 1: create models for weather. And also why are there different models.

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Speaker 1: You've probably heard of various weather models. Why do we

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Speaker 1: not just have one? Why are there multiples? And why

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Speaker 1: are some quote unquote better than others in very specific scenarios.

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Speaker 1: We're going to cover that in the next episode. Now,

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Speaker 1: generally speaking, meteorological instruments fall into two broadcat gregories. You

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Speaker 1: have direct sensors also called institute sensors. They're inside the

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Speaker 1: situation like a thermometer that is left out to measure

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Speaker 1: the temperature of the air. It's institute. It is a

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Speaker 1: direct sensor. It's directly measuring the temperature of the air outside.

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Speaker 1: Then you have remote sensors that are measuring something that's

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Speaker 1: much further away. The name pretty much gives you the

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Speaker 1: indication of what it does. Now, we're going to talk

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Speaker 1: about both types in this episode. Direct sensors include lots

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Speaker 1: of stuff that you're familiar with, and we're gonna start

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Speaker 1: off with a good old, easy one to to talk

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Speaker 1: about thermometers, the noble thermometer telling us such information like dude,

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Speaker 1: it's wicked cold out that today, but on your coat,

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Speaker 1: or seriously, buddy, it's boiling out there. Let's play some

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Speaker 1: player unknowns battlegrounds in the air conditioned house. But how

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Speaker 1: do thermommeters actually work? So let's start with your basic

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Speaker 1: mercury thermometer. It's something that is still being used around

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Speaker 1: the world. It's your basic bulb thermometer. It depends upon

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Speaker 1: a simple physical principle, which is that a liquids volume

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Speaker 1: changes relative to the temperature of the liquid. So when

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Speaker 1: you heat a liquid up, it's molecules decide to do

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Speaker 1: the equivalent of the guy I'm always seated next to

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Speaker 1: on a long distance plane ride. In other words, it

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Speaker 1: spreads out well beyond its normal parameters. You know who

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Speaker 1: I'm talking about. Give me my arm rest back. But

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Speaker 1: that's what happens with liquids. You heat them up, the

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Speaker 1: molecules get more energy, they get excited, they move around more,

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Speaker 1: and they spread apart. So as a result, the liquid expands,

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Speaker 1: and if, of course you do this long enough, the

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Speaker 1: liquid will end up turning into a gas, which is

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Speaker 1: even more free form than liquid. Obvious asleep. When liquids

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Speaker 1: get cold, those molecules end up huddling together, not so

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Speaker 1: much for warmth, but because they have less energy they

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Speaker 1: don't move around so much, so the liquid actually takes

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Speaker 1: up less space than it normally would. So your basic

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Speaker 1: bulb thermometer consists of a small bulb at the base

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Speaker 1: and a narrow, long, closed tube leading up from that

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Speaker 1: bulb base. These physical proportions accentuate the change in volume

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Speaker 1: of the liquid, So you want the bulb to be

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Speaker 1: small because you want any changes in temperature in whatever

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Speaker 1: environment you are measuring to rapidly be reflected within the

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Speaker 1: thermometer itself. So, for example, if you're talking about outside.

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Speaker 1: Any drastic change in the outside temperature, you want that

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Speaker 1: to be reflected in an outside thermometer pretty quickly. Typically

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Speaker 1: those temperatures don't increase or drop that fast. But let's

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Speaker 1: say you want to go from room temperature thermometer and

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Speaker 1: you're testing someone's temperature. You want to find out they

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Speaker 1: have a fever or not. You don't want to have

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Speaker 1: to wait a very long time for that change in

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Speaker 1: temperature to UH to happen within the mercury inside that thermometer.

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Speaker 1: So that's why that bulb is small. It's just a

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Speaker 1: small amount of liquid. Doesn't change take very long for

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Speaker 1: that change in temperature to move through the liquid, and

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Speaker 1: thus the volume increases inside the the thermometer. UH. With weather,

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Speaker 1: it means you you'd want something that will remain liquid

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Speaker 1: at temperatures found across most of the planet, which is

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Speaker 1: why we use mercury. Mercury is a metal. It is

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Speaker 1: a metal that is liquid at room temperature and a

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Speaker 1: lot of temperatures that you will find on Earth. Very

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Speaker 1: useful in that sense, it's not going to boil away

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Speaker 1: rapidly at high a temperatures, nor does it freeze at

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Speaker 1: your typical low temperatures. When you get two very low,

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Speaker 1: which does happen on Earth, mercury will free So it's

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Speaker 1: not perfect, but it's reliable and it's easy to read

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Speaker 1: the differences. It's um it shows up well in a

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Speaker 1: glass thermometer, and as it turns out, uh, mercury liquid

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Speaker 1: mercury is is pretty reliable. It remains liquid at temperatures

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Speaker 1: that range from six D seventy four degrees fahrenheit, which

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Speaker 1: is three D fifty six point seventy three degrees celsius,

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Speaker 1: all the way down to its freezing point of minus

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Speaker 1: thirty eight fahrenheit or minus thirty eight point eight three celsius.

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Speaker 1: But hey, here's a fun fact. The most extreme cold

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Speaker 1: temperatures on Earth get way below minus thirty eight celsius.

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Speaker 1: In fact, in NASA released satellite data that measured the

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Speaker 1: lowest recorded temperature at minus ninety four point seven celsius,

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Speaker 1: which is minus one thirty five point eight fahrenheit. At

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Speaker 1: that temperature, mercury itself would freeze. So for very low

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Speaker 1: temperatures you cannot use a mercury thermometer. You just you're

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Speaker 1: not gonna it's gonna be as cold as it gets.

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Speaker 1: It's already frozen. It's a solid, so you actually have

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Speaker 1: to use a different kind of liquid. If you want

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Speaker 1: to use a liquid thermometer, alcohol works. Uh. They call

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Speaker 1: them spirit thermometers in the old days because you're talking

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Speaker 1: about spirits alcohol. Alcohol is a very low freezing point,

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Speaker 1: and it's boiling point, however, is much lower than mercury,

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Speaker 1: so you can't use it for very high temperature things,

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Speaker 1: you know, but it works great for low temperature applications.

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Speaker 1: And uh, this actually leads me to an interesting question

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Speaker 1: that I think is fun to tackle, even though it's

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Speaker 1: not not quite as technical. How did we come up

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Speaker 1: with the fahrenheit and celsius scales? Well, it all has

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Speaker 1: to do with the freezing and boiling points of water,

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Speaker 1: which makes sense. Water is very prevalent here on Earth.

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Speaker 1: Most of our surface of our planet is covered in water.

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Speaker 1: We depend upon water for our survival, so the temperatures

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Speaker 1: at which water will freeze or boil are obviously important

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Speaker 1: to us. So fahrenheit will start with that because that

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Speaker 1: scale was proposed first. That came from Daniel Danny Boy

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Speaker 1: fahrenheit in fourteen and as far as I know, no

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Speaker 1: one else called him Danny Boy, but I'm waiting for

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Speaker 1: it to catch On fourteen, he decided to use a

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Speaker 1: scale designed actually by a predecessor of his. It was

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Speaker 1: not it was not completely invented by Fahrenheit. He took

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Speaker 1: a scale that was made by a man named Olaus Rummer.

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Speaker 1: Rummer's thermometer listed zero as the lowest point. That was

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Speaker 1: not the freezing point, but it was as low as

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Speaker 1: the thermometer could register. Was zero and at seven point

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Speaker 1: five on Rumors scale, that's where I would melt into water,

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Speaker 1: or if you prefer where water would freeze into ice.

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Speaker 1: It is the freezing point or melting point, depending upon

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Speaker 1: your perspective. That was seven and a half on or

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Speaker 1: scale at twenty two and a half that was considered

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Speaker 1: body temperature, and sixty was the temperature for boiling water.

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Speaker 1: So it went from zero to sixty with boiling water

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Speaker 1: being at the top and freezing being at about seven

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Speaker 1: and a half fahrenheit to create a mercury thermometer, and

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Speaker 1: it was capable of making more precise measurements than the

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Speaker 1: the spirit thermometer that Rumor had been using. And because

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Speaker 1: of that precision, since you could measure smaller changes in temperature,

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Speaker 1: fair Kneit felt that there needed to be a scale

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Speaker 1: that would be broader than than Rumor's scale so that

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Speaker 1: you could easily talk about tiny changes in temperature. Right,

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Speaker 1: it's just getting an extra level of precision in there,

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Speaker 1: and it means that you don't have to subdivide those

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Speaker 1: units into further and further decimal points in order to

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Speaker 1: describe the differences of temperature changes. So Fahrenheit ended up

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Speaker 1: first taking rumor scale and he multiplied it by four. Uh.

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Speaker 1: He then adjusted the scale. He started doing some research

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Speaker 1: and realized that just multiplying it by four it meant

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Speaker 1: that it wasn't as accurate as it needed to be.

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Speaker 1: He had more levels of precision, but the accuracy was off.

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Speaker 1: Multiplying it by four it multiplied not just the scale

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Speaker 1: but also the imprecision of that original scale. So he

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Speaker 1: started to try and refine it. Fahrenheit ended up after

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Speaker 1: he passed away, people took his scale and began to

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Speaker 1: refine it more, and they began to establish the freezing

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Speaker 1: point and boiling point of water, and decided to set

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Speaker 1: the freezing point and boiling point apart by one eighty degrees,

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Speaker 1: which is important in math, but not so great for

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Speaker 1: just casual conversation, So some people would say it was

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Speaker 1: kind of an arbitrary decision to make it a one

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Speaker 1: degree difference between freezing and boiling. The temperature of freezing

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Speaker 1: water was eventually established as thirty two degrees, which means

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Speaker 1: boiling water would be two hundred twelve degrees. One benefit

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Speaker 1: of the scale was that the units would allow for

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Speaker 1: subtle descriptions of temperature changes without the need for decimals.

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Speaker 1: So if you were to describe the temperature as rising

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Speaker 1: from eighty six to eighty seven in fahrenheit, that's easy.

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Speaker 1: But if you wanted to say the same thing in celsius,

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Speaker 1: to take those same two temperatures and talk about that increase,

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Speaker 1: you'd say it went from thirty degrees celsius to thirty

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Speaker 1: point six degrees celsius, or so if you said thirty

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Speaker 1: one celsius, you're not being as precise because that's a

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Speaker 1: greater change in temperature than what you're actually referring to.

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Speaker 1: Now that being at having the temperature for freezing water

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Speaker 1: set at thirty two degrees is a bit frustrating, but

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Speaker 1: I think I have an explanation for this. This is

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Speaker 1: Jonathan's supposition corner. I kind of wish I could get

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Speaker 1: Dylan to make a musical sting for this. That just

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Speaker 1: sounds confusing. All right, here's here's my pitch. Why is

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Speaker 1: water freezing at thirty two degrees? Why is it thirty

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Speaker 1: two degrees? Why is it not zero? Why would you

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Speaker 1: not start at zero for the freezing point of water?

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Speaker 1: If water is the really important part on your scale,

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Speaker 1: it's because it can get colder than freezing here on Earth.

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Speaker 1: And so you've got fahrenheit saying, well, I want a

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Speaker 1: scale that I can measure the temperature even when it's

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Speaker 1: colder than freezing, because some days it is colder than freezing,

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Speaker 1: so I need my scale to be able to reflect that.

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Speaker 1: But how do I measure that? If I've set freezing

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Speaker 1: as zero? Where do I go from there? I mean,

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Speaker 1: I can't have the mercury go further down. I've got it.

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Speaker 1: I'll set freezing higher up on the scale, And that

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Speaker 1: way you can still describe stuff that's colder than freezing water,

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Speaker 1: but not colder than what I can measure. So, uh,

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Speaker 1: you set the bottom of your scale lower than the

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Speaker 1: temperature for freezing. In that way, every measurement you take

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Speaker 1: is a positive unit, you don't have to create negative units,

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Speaker 1: So you just set your scales based at the temperature

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Speaker 1: lower than what it tends to get down to. Right.

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Speaker 1: So Fair Knight, say as well, doesn't often get colder

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Speaker 1: than today, So today is gonna be zero, and everything

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Speaker 1: above that will be fine, because how could it get

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Speaker 1: colder than today? That's Jonathan's supposition, corner, y'all? All right,

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Speaker 1: but what about Celsius. Celsius was the brainchild of Andres

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Speaker 1: Celsius in seventy two, so a few decades after Fair

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Speaker 1: and Height, he had the clever idea of creating a

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Speaker 1: temperature scale where the freezing and boiling points of water

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Speaker 1: would be separated by one hundred degrees, making it much

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Speaker 1: easier to talk about, especially for mathematic uh purposes. So

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Speaker 1: zero to one, taking that simple decimal scale, it makes sense, uh,

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Speaker 1: Although originally he intended to make one hundred the freezing

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Speaker 1: point of water and zero the boiling point of water,

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Speaker 1: so in other words, the scale was inverted. The higher

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Speaker 1: the unit number, the lower the temperature would be. So

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Speaker 1: really he was creating a scale to measure cold, not heat.

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Speaker 1: So a one hundred degrees Celsius in the original implementation

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Speaker 1: would be freezing temperatures, whereas a zero degrees celsius in

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Speaker 1: the original implementation would be boiling water. Guests arguing that

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Speaker 1: why would you ever get hotter than boiling water? Maybe Uh,

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Speaker 1: this did not stick obviously. His contemporaries ended up deciding

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Speaker 1: that that was not logical and perhaps a bit whacka noodle,

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Speaker 1: and so they flipped it so that zero is freezing

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Speaker 1: on is boiling. Uh. Celsius did not live to see

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Speaker 1: his his his standard became a standard. It was not

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Speaker 1: a standard during his lifetime. He actually passed away only

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Speaker 1: a couple of years after proposing it, so he did

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Speaker 1: not get to see how it was adopted by almost

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Speaker 1: the entire world, with the exception of some notable places

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Speaker 1: such as the United States of America, where we still

431
00:27:39,200 --> 00:27:43,119
Speaker 1: use fahrenheit and not celsius. Although I still like fahrenheit

432
00:27:43,240 --> 00:27:46,480
Speaker 1: because it is easier to talk about more subtle changes

433
00:27:46,520 --> 00:27:50,359
Speaker 1: in temperature than it is with celsius. Also, I just

434
00:27:50,400 --> 00:27:52,320
Speaker 1: grew up with it, so at this point it's hard

435
00:27:52,320 --> 00:27:53,640
Speaker 1: for me to sit there and think, like, if someone

436
00:27:53,680 --> 00:27:57,680
Speaker 1: tells me it's twenty five degrees celsius, I have no real,

437
00:27:59,480 --> 00:28:01,879
Speaker 1: no real correlation of that in my brain. Like I

438
00:28:01,880 --> 00:28:05,160
Speaker 1: couldn't tell you how warm or cold twenty five degrees

439
00:28:05,200 --> 00:28:08,680
Speaker 1: celsius is um but if you tell me that it's

440
00:28:08,840 --> 00:28:12,280
Speaker 1: eighty nine degrees fahrenheit, I know how hot you're talking.

441
00:28:13,240 --> 00:28:16,440
Speaker 1: So you know fun times. But what if you wanted

442
00:28:16,480 --> 00:28:18,520
Speaker 1: to convert fare kneit to celsius and you don't have

443
00:28:18,600 --> 00:28:21,040
Speaker 1: access to Google, which makes it really easy to do

444
00:28:21,960 --> 00:28:24,440
Speaker 1: and how I did it whenever I needed to make conversions.

445
00:28:24,520 --> 00:28:26,679
Speaker 1: Let's say that you want to do a conversion of

446
00:28:26,720 --> 00:28:30,200
Speaker 1: fahrenheit to celsius, but you don't have access to a

447
00:28:30,200 --> 00:28:34,680
Speaker 1: temperature calculator. Well, you just follow this handy dandy guide.

448
00:28:34,800 --> 00:28:38,480
Speaker 1: You take your fahreneit temperature, you subtract thirty two from

449
00:28:38,560 --> 00:28:41,720
Speaker 1: that temperature. Then you multiply your new number by the

450
00:28:41,800 --> 00:28:45,320
Speaker 1: number five. Then you divide that new number by the

451
00:28:45,400 --> 00:28:48,320
Speaker 1: number nine. Now you know what temperature it was half

452
00:28:48,320 --> 00:28:50,160
Speaker 1: an hour ago before you had to deal with all

453
00:28:50,160 --> 00:28:54,640
Speaker 1: that math. It's a joke. I'm a liberal arts major,

454
00:28:54,880 --> 00:28:57,560
Speaker 1: so make a lot of jokes about being bad at math.

455
00:28:58,760 --> 00:29:03,720
Speaker 1: They're mostly jokes, there's some truth to them. Honestly, I

456
00:29:03,720 --> 00:29:07,080
Speaker 1: don't think anyone really knows how math works. That's also

457
00:29:07,120 --> 00:29:12,040
Speaker 1: a joke. These days, more thermometers are actually electronic. They're

458
00:29:12,080 --> 00:29:16,040
Speaker 1: not based upon some liquid moving up or down a tube.

459
00:29:16,040 --> 00:29:20,800
Speaker 1: Based on changes in temperature, they end up using thermo resistors,

460
00:29:20,960 --> 00:29:25,280
Speaker 1: or sometimes they're just called thermistors. That's also not a joke.

461
00:29:25,320 --> 00:29:28,280
Speaker 1: They really are called that. These are materials they experience

462
00:29:28,360 --> 00:29:32,240
Speaker 1: a change in electrical resistance due to temperature fluctuation. So remember,

463
00:29:32,760 --> 00:29:36,640
Speaker 1: electrical resistance is the tendency of a material to resist

464
00:29:36,840 --> 00:29:41,400
Speaker 1: or impede the flow of electrons through that material. If

465
00:29:41,480 --> 00:29:43,920
Speaker 1: you have a material that has a very low resistance

466
00:29:44,000 --> 00:29:48,000
Speaker 1: like copper, those are good conductors. Metals that have our

467
00:29:48,080 --> 00:29:51,000
Speaker 1: materials rather that have a very high resistance like rubber

468
00:29:51,160 --> 00:29:56,200
Speaker 1: are really good insulators. And temperature turns out can affect

469
00:29:56,360 --> 00:30:00,160
Speaker 1: some materials with their electrical resistance, which means that at

470
00:30:00,160 --> 00:30:03,800
Speaker 1: certain temperatures electricity may pass more easily through that material

471
00:30:04,040 --> 00:30:07,080
Speaker 1: than at other temperatures. So that is the basis for

472
00:30:07,200 --> 00:30:11,280
Speaker 1: electronic thermometers. The most common thermistors have a resistance that

473
00:30:11,480 --> 00:30:15,920
Speaker 1: decreases as temperatures increase. In other words, they become more

474
00:30:16,040 --> 00:30:20,680
Speaker 1: conductive the warmer it gets. This is called a negative

475
00:30:20,920 --> 00:30:26,760
Speaker 1: temperature coefficient or NTC thermistor because it's this uh see

476
00:30:26,800 --> 00:30:33,720
Speaker 1: saw kind of relationship, right, the temperature increases, resistance decreases.

477
00:30:34,560 --> 00:30:37,280
Speaker 1: There are also some that have a resistance that increases

478
00:30:37,320 --> 00:30:41,000
Speaker 1: with temperature. These are called positive temperature coefficient or PTC

479
00:30:41,200 --> 00:30:44,680
Speaker 1: therm mists. So with these, as the temperature goes up

480
00:30:44,720 --> 00:30:48,120
Speaker 1: in the material, so does its electrical resistance. But most

481
00:30:48,120 --> 00:30:53,480
Speaker 1: electronic thermometers use NTC therm mists. The relationship between temperature

482
00:30:53,560 --> 00:30:58,520
Speaker 1: change and variation resistance is not a constant, so you

483
00:30:58,680 --> 00:31:04,000
Speaker 1: cannot say that resistance changes by the same amount of ohms.

484
00:31:04,480 --> 00:31:07,880
Speaker 1: Those are the units we use to measure electrical resistance.

485
00:31:08,840 --> 00:31:10,800
Speaker 1: But you can't say that it's gonna change by the

486
00:31:10,880 --> 00:31:13,840
Speaker 1: same number of ohm's per degree of celsius. So if

487
00:31:13,840 --> 00:31:17,000
Speaker 1: you go from twenty three to twenty four degrees celsius

488
00:31:17,040 --> 00:31:19,320
Speaker 1: and then twenty four to twenty five degrees celsius and

489
00:31:19,320 --> 00:31:22,520
Speaker 1: twenty five to twenty six degrees celsius, the difference in

490
00:31:22,640 --> 00:31:27,239
Speaker 1: resistance by ohms is not going to be linear in

491
00:31:27,280 --> 00:31:31,720
Speaker 1: relation to those changes in temperature. Typically, thermistor resistance varies

492
00:31:31,760 --> 00:31:34,040
Speaker 1: in a nonlinear way, but in a way that you

493
00:31:34,080 --> 00:31:37,200
Speaker 1: can still factor by using a formula, So you have

494
00:31:37,240 --> 00:31:39,720
Speaker 1: to design a formula that takes all of this into

495
00:31:39,760 --> 00:31:43,480
Speaker 1: account in order for you to relay a change in

496
00:31:43,520 --> 00:31:47,320
Speaker 1: resistance as being a change in temperature. So an electronic

497
00:31:47,360 --> 00:31:52,640
Speaker 1: thermometers microprocessor detects and measures these changes in resistance, takes

498
00:31:52,680 --> 00:31:57,120
Speaker 1: that formula into account, converts those measurements into temperature units.

499
00:31:57,720 --> 00:32:00,360
Speaker 1: Their mists are also used in other applications as well,

500
00:32:00,480 --> 00:32:03,360
Speaker 1: so you might use one to protect a circuit from

501
00:32:03,480 --> 00:32:07,280
Speaker 1: electrical overload. You've got electricity running through a circuit. A

502
00:32:07,280 --> 00:32:10,080
Speaker 1: current is running through the circuit. Let's say that the

503
00:32:10,080 --> 00:32:13,080
Speaker 1: current increases uh to a point where it's going to

504
00:32:13,160 --> 00:32:16,280
Speaker 1: cause issues with the circuit if it continues on this path.

505
00:32:16,880 --> 00:32:21,520
Speaker 1: If you have a thermistor positive a PTC thermistor in

506
00:32:21,560 --> 00:32:26,440
Speaker 1: that circuit, then as it warms up, its resistance will increase.

507
00:32:27,320 --> 00:32:32,920
Speaker 1: So current runs through the thermistor that makes it generate

508
00:32:32,960 --> 00:32:36,640
Speaker 1: heat that ends up changing its electrical resistance, and eventually

509
00:32:36,720 --> 00:32:40,280
Speaker 1: it ends up becoming a barrier to current, so that

510
00:32:40,640 --> 00:32:43,320
Speaker 1: the current cannot continue to flow through the circuit, and

511
00:32:43,360 --> 00:32:46,160
Speaker 1: thus the thermistor will end up protecting the rest of

512
00:32:46,200 --> 00:32:50,400
Speaker 1: the circuit from electrical overload. So that's one potential application

513
00:32:50,400 --> 00:32:54,080
Speaker 1: of a thermistor outside of electronic thermometers. I thought it

514
00:32:54,120 --> 00:32:57,560
Speaker 1: was pretty nifty. Well, I've got more nifty things to say,

515
00:32:57,600 --> 00:32:59,840
Speaker 1: and we're going to move away from temperature. But before

516
00:32:59,840 --> 00:33:02,680
Speaker 1: I do that, let's take a quick break to thank

517
00:33:02,680 --> 00:33:13,520
Speaker 1: our sponsor. All Right, so we've covered temperature. Now let's

518
00:33:13,600 --> 00:33:19,360
Speaker 1: tackle our next sensor, the barometer. Barometers measure air pressure,

519
00:33:19,520 --> 00:33:22,360
Speaker 1: and as I mentioned in that last episode about whether

520
00:33:22,480 --> 00:33:26,400
Speaker 1: air pressure plays an enormous role in how weather behaves.

521
00:33:26,960 --> 00:33:31,080
Speaker 1: So knowing the current air pressure conditions helps meteorologists understand

522
00:33:31,120 --> 00:33:34,560
Speaker 1: what might happen next. So, for example, if your area

523
00:33:34,680 --> 00:33:37,840
Speaker 1: happens to be under high air pressure, that's an indicator

524
00:33:38,680 --> 00:33:41,600
Speaker 1: that you're not likely to see very much rain that day.

525
00:33:41,960 --> 00:33:46,560
Speaker 1: High air pressure systems tend to keep rain systems out. Typically,

526
00:33:47,160 --> 00:33:49,680
Speaker 1: if the pressure is starting to drop, so you're seeing

527
00:33:49,720 --> 00:33:52,680
Speaker 1: a change in air pressure, that could indicate that it's

528
00:33:52,680 --> 00:33:56,440
Speaker 1: going to get windy. It might possibly indicate that there's

529
00:33:56,440 --> 00:33:59,280
Speaker 1: some wet weather on the way because a low pressure

530
00:33:59,280 --> 00:34:02,600
Speaker 1: system is moving into what was a high pressure system.

531
00:34:02,640 --> 00:34:04,560
Speaker 1: But you have to have something to measure that air

532
00:34:04,600 --> 00:34:08,799
Speaker 1: pressure changes. An air pressure at any given altitude are

533
00:34:08,840 --> 00:34:12,680
Speaker 1: typically too subtle for humans to really pick up on. Right, Like,

534
00:34:13,080 --> 00:34:15,920
Speaker 1: if I'm at sea level, I'm not likely to detect

535
00:34:16,040 --> 00:34:19,280
Speaker 1: very subtle changes in air pressure, but I would notice

536
00:34:19,280 --> 00:34:21,479
Speaker 1: the difference if I were to go from say, Death

537
00:34:21,600 --> 00:34:25,399
Speaker 1: Valley to Mount Everest. Those changes in altitude are so

538
00:34:25,600 --> 00:34:29,160
Speaker 1: dramatic that the differences an air pressure would be noticeable

539
00:34:29,680 --> 00:34:33,440
Speaker 1: and actually a fatal problem. On Mount Everest, I wouldn't

540
00:34:33,480 --> 00:34:38,240
Speaker 1: be able to adjust to that remarkable drop an air pressure,

541
00:34:38,239 --> 00:34:41,960
Speaker 1: not to mention temperature, uh that rapidly. I would need

542
00:34:42,000 --> 00:34:45,239
Speaker 1: to acclimate to it to avoid getting sick and potentially

543
00:34:45,320 --> 00:34:52,040
Speaker 1: having a really fatal problems. So, yes, you can detect

544
00:34:52,040 --> 00:34:54,680
Speaker 1: differences an air pressure, but typically if you're at a

545
00:34:54,800 --> 00:34:58,600
Speaker 1: single altitude, you're not moving up or down. You're just

546
00:34:58,760 --> 00:35:03,040
Speaker 1: experiencing changes in air pressure due to pressure systems. You

547
00:35:03,280 --> 00:35:06,640
Speaker 1: probably aren't going to be conscious of that change in

548
00:35:06,719 --> 00:35:10,000
Speaker 1: air pressure because it's it tends to be fairly subtle,

549
00:35:10,520 --> 00:35:14,120
Speaker 1: even though it can mean some major changes in weather.

550
00:35:14,640 --> 00:35:19,200
Speaker 1: Barometers measure air pressure. They detect how much air is

551
00:35:19,280 --> 00:35:22,680
Speaker 1: pressing down on them, so in a way, it's kind

552
00:35:22,719 --> 00:35:26,440
Speaker 1: of like a set of scales for the atmosphere. So

553
00:35:26,520 --> 00:35:29,400
Speaker 1: how do you do that? How do you make something

554
00:35:29,440 --> 00:35:32,440
Speaker 1: that can actually detect how much air is pushing down

555
00:35:32,440 --> 00:35:36,480
Speaker 1: on them? Well, the simplest type really is called a

556
00:35:36,600 --> 00:35:43,120
Speaker 1: Tori Chilian barometer, and it's named after its inventor, Evangelista Barometer. No,

557
00:35:43,200 --> 00:35:47,080
Speaker 1: I'm sorry, wait, Evangelista Toricelli. He was an Italian physicist

558
00:35:47,160 --> 00:35:51,120
Speaker 1: and a mathematician of the seventeen century. Torchelli is one

559
00:35:51,120 --> 00:35:55,240
Speaker 1: of the mathematicians who laid the groundwork for integral calculus,

560
00:35:55,640 --> 00:35:58,319
Speaker 1: but I'm not going to hold that against him. Toward

561
00:35:58,440 --> 00:36:01,360
Speaker 1: Chelli worked with Galileo who gave tor Chelly the idea

562
00:36:01,440 --> 00:36:06,560
Speaker 1: that he should experiment with glass tubes and mercury to

563
00:36:06,920 --> 00:36:10,880
Speaker 1: study things like vacuums as well as other physical properties.

564
00:36:11,040 --> 00:36:14,680
Speaker 1: And this was in sixteen three. So tore Chelly took

565
00:36:14,719 --> 00:36:18,600
Speaker 1: a tube that was four ft long or about one

566
00:36:18,640 --> 00:36:22,239
Speaker 1: point two meters. It was sealed at one end, so

567
00:36:22,560 --> 00:36:25,880
Speaker 1: think of like a test tube. He filled it with

568
00:36:26,040 --> 00:36:30,920
Speaker 1: liquid mercury, and then he overtook, turned the tube and

569
00:36:30,960 --> 00:36:33,359
Speaker 1: put the end of it in a dish that had

570
00:36:33,480 --> 00:36:37,359
Speaker 1: raised sides. So at first mercury started to come out

571
00:36:37,360 --> 00:36:40,880
Speaker 1: of the tube and into the dish, but eventually the

572
00:36:40,960 --> 00:36:44,760
Speaker 1: mercury settled and it was at a level above the dish.

573
00:36:44,800 --> 00:36:48,319
Speaker 1: It was, you know, like several inches above where the

574
00:36:48,440 --> 00:36:51,000
Speaker 1: base of the dish was above the level of the

575
00:36:51,040 --> 00:36:54,839
Speaker 1: rest of the mercury. And he thought, uh, that's kind

576
00:36:54,880 --> 00:36:57,160
Speaker 1: of interesting. The mercury did not sink all the way

577
00:36:57,200 --> 00:36:59,920
Speaker 1: down to the level of the dish. It actually remained

578
00:37:00,120 --> 00:37:03,880
Speaker 1: up quite a bit. And the area behind the mercury

579
00:37:03,960 --> 00:37:06,600
Speaker 1: at the top of the tube, so near the sealed end,

580
00:37:07,200 --> 00:37:10,759
Speaker 1: that was a vacuum. He had created a vacuum in

581
00:37:10,800 --> 00:37:13,359
Speaker 1: this way. There was nothing, no air in that part

582
00:37:13,440 --> 00:37:18,760
Speaker 1: of the tube. Then he noted that the mercury's level

583
00:37:18,880 --> 00:37:22,800
Speaker 1: would change day to day, and some days the mercury

584
00:37:22,800 --> 00:37:25,799
Speaker 1: would actually end up being higher in the tube than

585
00:37:25,880 --> 00:37:29,239
Speaker 1: it was the day before. So this meant the mercury

586
00:37:29,480 --> 00:37:32,120
Speaker 1: wasn't just leaking out. Right. If you kept coming out

587
00:37:32,200 --> 00:37:35,239
Speaker 1: day after day and the mercury level is getting gradually

588
00:37:35,320 --> 00:37:40,440
Speaker 1: lower every single day, your conclusion might be this mercury

589
00:37:40,480 --> 00:37:43,879
Speaker 1: is very gradually leaking out of the tube into the dish.

590
00:37:43,960 --> 00:37:46,200
Speaker 1: But if you come back one day and the mercury

591
00:37:46,280 --> 00:37:48,600
Speaker 1: is actually higher up in the tube than it was

592
00:37:48,640 --> 00:37:51,200
Speaker 1: the day before, something else has to be happening. It

593
00:37:51,320 --> 00:37:54,560
Speaker 1: can't just be leaking out. So towards Shelly figured that

594
00:37:54,719 --> 00:37:58,399
Speaker 1: atmospheric pressure was the reason for the changes in the

595
00:37:58,400 --> 00:38:02,160
Speaker 1: height of the mercury in the tube. On high pressure days,

596
00:38:02,480 --> 00:38:05,560
Speaker 1: when the air is pressing down harder because there's essentially

597
00:38:05,960 --> 00:38:10,440
Speaker 1: more dense air above you, then it ends up pressing

598
00:38:10,480 --> 00:38:14,200
Speaker 1: down on the mercury in the dish, which forces mercury

599
00:38:14,280 --> 00:38:17,279
Speaker 1: up the tube. Because again, the mercury that's in the

600
00:38:17,280 --> 00:38:19,800
Speaker 1: tube with the vacuum in it, it's not being affected

601
00:38:19,840 --> 00:38:22,440
Speaker 1: by the changes in air pressure. It's only the mercury

602
00:38:22,520 --> 00:38:25,399
Speaker 1: that's in the dish that gets that effect. On low

603
00:38:25,440 --> 00:38:29,120
Speaker 1: pressure days, there's not as much air pressing down against

604
00:38:29,160 --> 00:38:31,040
Speaker 1: the mercury in the dish, and so more of it

605
00:38:31,120 --> 00:38:34,000
Speaker 1: starts to come out of the tube into the dish itself.

606
00:38:35,520 --> 00:38:39,480
Speaker 1: So he never actually published his findings on this. Despite

607
00:38:39,520 --> 00:38:42,919
Speaker 1: the fact that this was a really remarkable discovery, he

608
00:38:42,960 --> 00:38:45,719
Speaker 1: wasn't really concerned with it. He didn't think of it

609
00:38:45,760 --> 00:38:51,200
Speaker 1: as being particularly important, particularly in regards with his interest

610
00:38:51,320 --> 00:38:56,120
Speaker 1: in advancing mathematics toward Chilian barometers tend to use mercury

611
00:38:56,160 --> 00:38:59,920
Speaker 1: instead of other liquids, but it's not because of temperature.

612
00:39:00,040 --> 00:39:03,520
Speaker 1: Way thermometers are you don't necessarily worry about your barometer

613
00:39:03,719 --> 00:39:08,960
Speaker 1: overheating or freezing. It's because mercury is more dense than

614
00:39:09,040 --> 00:39:12,560
Speaker 1: water is, so you could create a barometer using water.

615
00:39:12,600 --> 00:39:15,719
Speaker 1: In fact, there were barometers that used water that predate

616
00:39:15,760 --> 00:39:18,960
Speaker 1: the tour Chilian barometers. But the problem is that water's

617
00:39:19,000 --> 00:39:21,439
Speaker 1: density is so much less that you need a much

618
00:39:21,560 --> 00:39:24,960
Speaker 1: longer tube to be able to see that the changes.

619
00:39:25,000 --> 00:39:28,319
Speaker 1: Otherwise you're gonna max out very early on because water

620
00:39:28,440 --> 00:39:31,200
Speaker 1: is less dense, right, it doesn't take as much pressure

621
00:39:31,400 --> 00:39:33,719
Speaker 1: to force water up a tube, so you have to

622
00:39:33,719 --> 00:39:36,600
Speaker 1: have much longer tube in order to be able to

623
00:39:36,600 --> 00:39:42,600
Speaker 1: to see these changes. Uh and it means that it

624
00:39:42,600 --> 00:39:45,560
Speaker 1: would be very difficult to take measurements, so mercury being

625
00:39:45,600 --> 00:39:48,520
Speaker 1: more dense made more sense. Also, it was very easy

626
00:39:48,560 --> 00:39:51,279
Speaker 1: to read it inside the barometer because again you're using

627
00:39:51,400 --> 00:39:55,200
Speaker 1: clear glass. Mercury is a silvery liquid, so it was

628
00:39:55,320 --> 00:39:59,800
Speaker 1: very easy to read the changes in the levels in

629
00:40:00,120 --> 00:40:05,879
Speaker 1: uh torre Chelian barometer. Now, at at sea level under

630
00:40:05,920 --> 00:40:10,399
Speaker 1: normal circumstances, under one atmosphere of pressure, mercury would rise

631
00:40:10,480 --> 00:40:14,040
Speaker 1: up to about the seventy six centimeter or thirty mark

632
00:40:14,239 --> 00:40:17,200
Speaker 1: in a torrey Chellian barometer, and while changes in air

633
00:40:17,239 --> 00:40:20,240
Speaker 1: pressure will be measurable with such a barometer, you wouldn't

634
00:40:20,239 --> 00:40:22,960
Speaker 1: see dramatic differences in the height of the mercury unless

635
00:40:22,960 --> 00:40:25,000
Speaker 1: you were to take the whole thing to a mountaintop

636
00:40:25,120 --> 00:40:27,880
Speaker 1: or something. So in other words, you could watch the

637
00:40:27,920 --> 00:40:30,600
Speaker 1: mercury in the barometer and it could very accurately and

638
00:40:30,640 --> 00:40:35,360
Speaker 1: with great precision, show you the changes in barometric pressure.

639
00:40:36,360 --> 00:40:41,759
Speaker 1: But those changes wouldn't necessarily be really dramatic because you're

640
00:40:41,800 --> 00:40:45,640
Speaker 1: talking about again the same altitude. Were you to take

641
00:40:45,840 --> 00:40:49,840
Speaker 1: a mercury barometer at Death Valley and then magically transport

642
00:40:49,880 --> 00:40:53,040
Speaker 1: yourself to Mount Everest, you would see a very dramatic

643
00:40:53,200 --> 00:40:57,919
Speaker 1: change in the height of the mercury in that barometer. Now,

644
00:40:57,960 --> 00:41:01,440
Speaker 1: maybe you've seen barometers that haven't entical dial that either

645
00:41:01,640 --> 00:41:05,720
Speaker 1: turns left or right along a semicircular scale that tells

646
00:41:05,719 --> 00:41:08,759
Speaker 1: you what the barometric pressure is. So how did those work? Well,

647
00:41:08,840 --> 00:41:13,120
Speaker 1: these are called aneroid barometers, and they're pretty clever. Inside

648
00:41:13,239 --> 00:41:18,200
Speaker 1: of these, there's a sealed, air tight metal box, and

649
00:41:18,239 --> 00:41:22,600
Speaker 1: attached to that metal box is a spring. Now, when

650
00:41:22,760 --> 00:41:26,640
Speaker 1: the air pressure is high, it compresses this metal box,

651
00:41:27,080 --> 00:41:29,600
Speaker 1: and that ends up pulling on the string on the

652
00:41:29,640 --> 00:41:33,359
Speaker 1: spring rather, which then creates the force necessary to move

653
00:41:33,400 --> 00:41:36,279
Speaker 1: the dial, so it indicates a high pressure system is

654
00:41:36,320 --> 00:41:40,239
Speaker 1: moved in and low pressure the little metal box. The

655
00:41:40,239 --> 00:41:44,839
Speaker 1: air type metal metal box expands and this ends up

656
00:41:44,880 --> 00:41:48,000
Speaker 1: pushing against the spring, which means that the dial will

657
00:41:48,040 --> 00:41:52,000
Speaker 1: move toward the other side, showing a low pressure uh

658
00:41:52,200 --> 00:41:56,320
Speaker 1: system has moved in. So the dial turning to the

659
00:41:56,400 --> 00:41:58,960
Speaker 1: left or right is all dependent upon whether or not

660
00:41:59,040 --> 00:42:03,200
Speaker 1: this metal box is compressed or expanded. It's actually incredibly

661
00:42:03,239 --> 00:42:05,840
Speaker 1: simple when you think about it, and thus I think

662
00:42:06,000 --> 00:42:11,640
Speaker 1: a pretty elegant way of measuring air pressure. Mercury barometers

663
00:42:11,680 --> 00:42:16,239
Speaker 1: are more accurate than aneroid barometers, but there's a disadvantage

664
00:42:16,280 --> 00:42:21,120
Speaker 1: to mercury barometers, which is that stuff's poison. Y'all, mercury

665
00:42:21,200 --> 00:42:25,040
Speaker 1: is toxic, so aneroid barometers are safer to have around.

666
00:42:25,719 --> 00:42:28,400
Speaker 1: They also are more portable, so you could put them

667
00:42:28,440 --> 00:42:30,680
Speaker 1: on stuff like sailing ships and not have to worry

668
00:42:30,719 --> 00:42:33,080
Speaker 1: about mercury spilling out all over the place because they

669
00:42:33,080 --> 00:42:36,560
Speaker 1: were mechanical didn't depend upon mercury at all. But if

670
00:42:36,560 --> 00:42:40,160
Speaker 1: you wanted something that had more precision and accuracy. You

671
00:42:40,200 --> 00:42:45,600
Speaker 1: wanted a mercury barometer, not an aneroid barometer. Uh. However,

672
00:42:45,680 --> 00:42:47,840
Speaker 1: we can go with microelectronics too. We don't have to

673
00:42:47,920 --> 00:42:52,279
Speaker 1: use mercury or anneroid, although the microelectronics version uses a

674
00:42:52,440 --> 00:42:56,400
Speaker 1: very similar approach to aneroid barometers. So we do have

675
00:42:56,440 --> 00:43:01,040
Speaker 1: barometric pressure sensors which rely on the piezo resistant of effect. Now,

676
00:43:01,080 --> 00:43:03,560
Speaker 1: this is kind of similar to what we were talking

677
00:43:03,600 --> 00:43:06,520
Speaker 1: about with thermistors, only in this case we're not talking

678
00:43:06,520 --> 00:43:13,080
Speaker 1: about temperature. We're talking about stuff that's under pressure. Do

679
00:43:13,160 --> 00:43:18,320
Speaker 1: you remember that has that same baseline as ice ice baby? Anyway,

680
00:43:18,560 --> 00:43:22,000
Speaker 1: you may have heard about the piezo electric effect, right.

681
00:43:22,120 --> 00:43:26,440
Speaker 1: Piezo electric effect refers to the tendency of certain materials

682
00:43:26,520 --> 00:43:30,359
Speaker 1: um certain types of crystals in particular like quartz, that

683
00:43:30,520 --> 00:43:35,120
Speaker 1: when you put a mechanical stress on those materials, such

684
00:43:35,200 --> 00:43:37,200
Speaker 1: as you mush mush mushed them up in some way,

685
00:43:37,640 --> 00:43:41,120
Speaker 1: these materials would generate an electric charge or there's a

686
00:43:41,160 --> 00:43:44,239
Speaker 1: reverse piece of electric effect. If you were to subject

687
00:43:44,360 --> 00:43:48,280
Speaker 1: these materials to an applied electric field, they would produce

688
00:43:48,400 --> 00:43:52,840
Speaker 1: a mechanical force like they vibrate and stuff. The crystal

689
00:43:53,120 --> 00:43:55,839
Speaker 1: courts are the quartz crystals. I guess I should say

690
00:43:56,280 --> 00:44:00,279
Speaker 1: in old watches. That's why they're used. It's has this

691
00:44:00,280 --> 00:44:05,879
Speaker 1: piezo electric effect. Piezo resistive materials are similar to that,

692
00:44:06,120 --> 00:44:10,759
Speaker 1: except that, as you would expect, their electrical resistance changes

693
00:44:11,160 --> 00:44:16,000
Speaker 1: as mechanical force applied to them changes. So typically you'd

694
00:44:16,000 --> 00:44:21,000
Speaker 1: put this piezo resistive material around a hermetically sealed cavity

695
00:44:21,400 --> 00:44:23,920
Speaker 1: similar to what you'd find in an aneroid barometer. So

696
00:44:23,960 --> 00:44:27,560
Speaker 1: you have this little area that you have hermetically sealed

697
00:44:27,640 --> 00:44:31,239
Speaker 1: and it's lined with this piezo resistive material, and as

698
00:44:31,239 --> 00:44:34,480
Speaker 1: the cavity reacts to changes in the air pressure, it

699
00:44:34,560 --> 00:44:39,640
Speaker 1: places mechanical stresses on the piezo resistive material inside, and

700
00:44:39,680 --> 00:44:44,080
Speaker 1: that again changes its electrical resistance. A microprocessor will measure

701
00:44:44,120 --> 00:44:49,040
Speaker 1: fluctuations in current passing through this piezo resistive material and

702
00:44:49,080 --> 00:44:53,360
Speaker 1: then convert those changes in current into a digital signal

703
00:44:53,400 --> 00:44:57,160
Speaker 1: that can be used to approximate pressure. All right, So

704
00:44:57,200 --> 00:45:00,200
Speaker 1: now we've got temperature and air pressure out of the way,

705
00:45:00,200 --> 00:45:02,799
Speaker 1: two of the big ones. But man, there's so much more.

706
00:45:03,200 --> 00:45:05,080
Speaker 1: So I'm gonna try and summarize some of the other

707
00:45:05,239 --> 00:45:09,520
Speaker 1: many sensors that are used by meteorological observation stations UH

708
00:45:09,640 --> 00:45:12,560
Speaker 1: today in order to gather information about the weather. But

709
00:45:12,600 --> 00:45:14,880
Speaker 1: I am going to summarize because otherwise this episode is

710
00:45:14,920 --> 00:45:19,560
Speaker 1: gonna last six hours long, and I got stuff to do, y'all.

711
00:45:20,000 --> 00:45:22,879
Speaker 1: So let's get another basic measurement out of the way,

712
00:45:23,160 --> 00:45:25,879
Speaker 1: and that would be wind, something I generate a lot

713
00:45:25,920 --> 00:45:29,080
Speaker 1: of from multiple ends. As it turns out, you want

714
00:45:29,120 --> 00:45:32,399
Speaker 1: to know where wind is coming from, and you want

715
00:45:32,400 --> 00:45:35,279
Speaker 1: to know how strong the wind is because this will

716
00:45:35,320 --> 00:45:39,560
Speaker 1: inform lots of other stuff like incoming changes to weather

717
00:45:39,920 --> 00:45:44,200
Speaker 1: such as storms, et cetera. For wind direction, we use

718
00:45:44,280 --> 00:45:46,839
Speaker 1: something that's been around for hundreds of years, weather vain.

719
00:45:48,080 --> 00:45:50,120
Speaker 1: We have lots of fancy ones today, but they all

720
00:45:50,160 --> 00:45:53,000
Speaker 1: are still working on the same general principle. I mean,

721
00:45:53,040 --> 00:45:56,800
Speaker 1: you can use more high tech ways to detect wind direction,

722
00:45:56,960 --> 00:46:01,160
Speaker 1: but it's really not necessary. So whether veins typically consist

723
00:46:01,239 --> 00:46:06,320
Speaker 1: of a counterweight on one end of a rotating UH

724
00:46:06,520 --> 00:46:09,600
Speaker 1: peace on the weather vein. On the other end, you

725
00:46:09,680 --> 00:46:14,879
Speaker 1: have some sort of thin that is covering a much

726
00:46:14,960 --> 00:46:18,240
Speaker 1: larger area than the counterweight is. So when wind blows,

727
00:46:18,280 --> 00:46:21,719
Speaker 1: it hits against the fin the weather vein because this

728
00:46:22,000 --> 00:46:26,040
Speaker 1: part of it can rotate freely along its axis. UH.

729
00:46:26,080 --> 00:46:29,920
Speaker 1: In the horizontal plane, it will rotate so that the

730
00:46:30,440 --> 00:46:32,680
Speaker 1: area being hit by the wind is facing away from

731
00:46:32,719 --> 00:46:36,880
Speaker 1: the wind. The counterweight will point into the wind. Often

732
00:46:36,920 --> 00:46:39,680
Speaker 1: the counterweight is in the form of an arrow, so

733
00:46:39,760 --> 00:46:41,279
Speaker 1: it might be the point of an arrow, and the

734
00:46:41,280 --> 00:46:45,040
Speaker 1: back may look like the fletching of an arrow, and

735
00:46:45,160 --> 00:46:48,960
Speaker 1: this tells you where the wind is coming from. So

736
00:46:49,200 --> 00:46:51,359
Speaker 1: if you have a traditional weather vein and the arrow

737
00:46:51,480 --> 00:46:55,920
Speaker 1: is pointing northeast, that tells you wind is coming from

738
00:46:56,160 --> 00:46:59,840
Speaker 1: the northeast. It is not blowing to the northeast. It

739
00:47:00,000 --> 00:47:03,120
Speaker 1: it's coming from the northeast. The counterweight is needed so

740
00:47:03,160 --> 00:47:06,719
Speaker 1: that there's equal mass on either ends of this rotating

741
00:47:06,880 --> 00:47:09,520
Speaker 1: part of the weather vein. But you also want to

742
00:47:09,520 --> 00:47:13,040
Speaker 1: make sure that there is an unequal area. In other words,

743
00:47:13,320 --> 00:47:16,400
Speaker 1: the back half of the weather vein of that rotating

744
00:47:16,440 --> 00:47:19,239
Speaker 1: piece needs to have more area to it so that

745
00:47:19,280 --> 00:47:23,000
Speaker 1: the wind pushes it in the right way. You want

746
00:47:23,000 --> 00:47:25,600
Speaker 1: more area on one side so that you can get

747
00:47:25,640 --> 00:47:27,680
Speaker 1: that into the right position, and that indicates where the

748
00:47:27,680 --> 00:47:30,640
Speaker 1: wind is coming from. UH. Once you look at where

749
00:47:30,640 --> 00:47:33,640
Speaker 1: the counterweight is, wind direction can give you a general

750
00:47:33,640 --> 00:47:35,680
Speaker 1: idea of what sort of weather you might encounter based

751
00:47:35,719 --> 00:47:40,239
Speaker 1: upon what's going on in that direction. So let's say

752
00:47:40,280 --> 00:47:43,200
Speaker 1: that you are in Georgia, the state that's where I'm in,

753
00:47:43,800 --> 00:47:48,000
Speaker 1: and you are in the winter, and you see that

754
00:47:48,120 --> 00:47:51,560
Speaker 1: the wind is coming from the northwest. You're looking at

755
00:47:51,560 --> 00:47:54,359
Speaker 1: a weather vein, it's pointing to the northwest. That's where

756
00:47:54,360 --> 00:47:57,359
Speaker 1: winds are coming from. And you happen to know that

757
00:47:57,440 --> 00:48:01,560
Speaker 1: there's a cold air mass that was moving down from

758
00:48:01,600 --> 00:48:05,040
Speaker 1: Canada through the United States. So you would say, well,

759
00:48:05,080 --> 00:48:07,880
Speaker 1: based upon the fact that wind is coming from the northwest,

760
00:48:07,920 --> 00:48:10,399
Speaker 1: that's the direction where if you were to go that way,

761
00:48:10,480 --> 00:48:14,359
Speaker 1: you hit Canada. And I happen to know that there's

762
00:48:14,400 --> 00:48:17,479
Speaker 1: a cold air mass moving down. I suspect that means

763
00:48:17,520 --> 00:48:20,080
Speaker 1: that pretty soon our temperatures are going to drop further

764
00:48:20,400 --> 00:48:23,840
Speaker 1: and we're going to get what is called the Devil's

765
00:48:23,920 --> 00:48:27,439
Speaker 1: dan droff down here in Georgia. Thank you, Saturday Night Live.

766
00:48:28,440 --> 00:48:31,239
Speaker 1: Most people know it as snow. We know it as

767
00:48:31,280 --> 00:48:35,759
Speaker 1: the stuff what shuts down our entire infrastructure at a

768
00:48:35,840 --> 00:48:42,240
Speaker 1: given heartbeat. Anyway, that's why wind direction is important, because

769
00:48:42,280 --> 00:48:44,880
Speaker 1: if you know what's going on elsewhere, then you can

770
00:48:44,960 --> 00:48:46,520
Speaker 1: and you know that the wind is coming from that

771
00:48:46,560 --> 00:48:50,080
Speaker 1: direction you, you can expect to get some of it yourself.

772
00:48:51,200 --> 00:48:54,880
Speaker 1: By the way, if you hear that winds are let's say, northeasterly,

773
00:48:55,360 --> 00:48:57,480
Speaker 1: that tells you where the winds are coming from, that

774
00:48:57,520 --> 00:49:00,520
Speaker 1: they're coming from the northeast. But if you hear the

775
00:49:00,520 --> 00:49:04,759
Speaker 1: suffix ward ended at the end of a direction, that

776
00:49:04,840 --> 00:49:08,200
Speaker 1: tells you the direction the winds are blowing toward, So

777
00:49:08,239 --> 00:49:13,520
Speaker 1: an eastward wind or eastward wind if you prefer, I

778
00:49:13,640 --> 00:49:17,680
Speaker 1: don't eastward wind that means winds are blowing to the east,

779
00:49:18,239 --> 00:49:22,680
Speaker 1: and easterly wind means winds are blowing from the east,

780
00:49:23,080 --> 00:49:26,399
Speaker 1: clear as mud, right. But wind direction is just one thing.

781
00:49:27,000 --> 00:49:31,080
Speaker 1: It's also useful to know wind speed. Now. Traditionally wind

782
00:49:31,080 --> 00:49:33,960
Speaker 1: speed was measured in knots or nautical miles per hour.

783
00:49:34,320 --> 00:49:39,120
Speaker 1: But was it not? I'll tell you, but not right now.

784
00:49:39,960 --> 00:49:42,520
Speaker 1: I'll tell you after we take another quick break to

785
00:49:42,640 --> 00:49:52,360
Speaker 1: thank our sponsors. So you want to measure wind speed

786
00:49:52,800 --> 00:49:55,680
Speaker 1: wind speed, you would measure and knots. Knots stands for

787
00:49:55,800 --> 00:49:59,200
Speaker 1: a nautical mile, although it's spelled like a knot like

788
00:49:59,280 --> 00:50:03,640
Speaker 1: you would tie and a thread. A nautical mile is

789
00:50:03,719 --> 00:50:07,040
Speaker 1: equal to one point one five miles per hour or

790
00:50:07,120 --> 00:50:10,399
Speaker 1: one point nine kilometers per hour. So if you hear

791
00:50:10,440 --> 00:50:14,359
Speaker 1: there's a northeasterly wind blowing at fifteen knots, you know

792
00:50:14,440 --> 00:50:17,520
Speaker 1: that the wind is coming from the northeast, and you

793
00:50:17,560 --> 00:50:20,440
Speaker 1: know that it's blowing at seventeen point to five miles

794
00:50:20,440 --> 00:50:23,600
Speaker 1: per hour or twenty eight and a half kilometers per hour.

795
00:50:23,840 --> 00:50:27,080
Speaker 1: But how do you determine wind speed? How do you

796
00:50:27,160 --> 00:50:31,440
Speaker 1: know how fast the wind is blowing? Well, meteorologists use

797
00:50:31,480 --> 00:50:36,240
Speaker 1: an instrument called an anemometer. The old anemometers had moving

798
00:50:36,280 --> 00:50:38,640
Speaker 1: parts in them that made them sort of look like

799
00:50:38,760 --> 00:50:42,720
Speaker 1: pin wheels. Uh. They had arms extending out from a hub,

800
00:50:43,000 --> 00:50:45,320
Speaker 1: with each arm ending in a little cup to catch

801
00:50:45,400 --> 00:50:48,800
Speaker 1: the wind, and then they would rotate along their axis

802
00:50:48,880 --> 00:50:52,719
Speaker 1: on the horizontal plane. So think of like a windmill,

803
00:50:52,760 --> 00:50:55,400
Speaker 1: but on its side, so it's the fans are not

804
00:50:55,560 --> 00:50:59,440
Speaker 1: standing up vertically, they're spread out horizontally and instead of

805
00:50:59,440 --> 00:51:02,319
Speaker 1: it being ends or fins, some some of them were,

806
00:51:02,480 --> 00:51:05,160
Speaker 1: but most of them ended with these cups that would

807
00:51:05,160 --> 00:51:07,880
Speaker 1: catch the wind. So the wind would blow and force

808
00:51:08,000 --> 00:51:11,200
Speaker 1: the hub to rotate along its axis in that horizontal plane.

809
00:51:11,680 --> 00:51:14,799
Speaker 1: And then it just depended on the type of anemometer

810
00:51:15,040 --> 00:51:17,600
Speaker 1: you're looking at. A lot of them worked in a

811
00:51:17,680 --> 00:51:21,200
Speaker 1: very similar way to an electric generator. So you might

812
00:51:21,239 --> 00:51:24,520
Speaker 1: remember this from our discussion about the history of electricity.

813
00:51:25,120 --> 00:51:28,560
Speaker 1: It's based on electro magnetism. If you have a magnet

814
00:51:29,200 --> 00:51:35,200
Speaker 1: and you turn it and it's surrounded by a conductive material,

815
00:51:35,360 --> 00:51:39,120
Speaker 1: or it's itself around a conductive material like a coil

816
00:51:39,200 --> 00:51:43,960
Speaker 1: of insulated copper wire, it will induce current to flow

817
00:51:44,280 --> 00:51:48,920
Speaker 1: through that conductor. Right. That's the basis of the electric generator.

818
00:51:49,360 --> 00:51:53,879
Speaker 1: So let's say you've got this spinning anemometer and it's

819
00:51:53,960 --> 00:51:58,560
Speaker 1: turning a magnet around a conductive material, and this creates

820
00:51:58,560 --> 00:52:01,719
Speaker 1: a current flowing through that duct of material. You have

821
00:52:02,239 --> 00:52:06,560
Speaker 1: then a electronic circuit that's specifically designed to measure how

822
00:52:06,640 --> 00:52:09,680
Speaker 1: much current has been produced and then converts that to

823
00:52:09,719 --> 00:52:13,160
Speaker 1: a digital readout that indicates wind speed. So you calibrate it.

824
00:52:13,280 --> 00:52:16,799
Speaker 1: You first have to calibrate this device so that it

825
00:52:16,920 --> 00:52:22,160
Speaker 1: quote unquote knows how much current relates to which you

826
00:52:22,200 --> 00:52:24,719
Speaker 1: know what the wind speed is. But once you've calibrated it,

827
00:52:25,160 --> 00:52:27,960
Speaker 1: that's how you can measure wind speed. You just look

828
00:52:28,000 --> 00:52:30,520
Speaker 1: at how much electric current is generated in one of

829
00:52:30,560 --> 00:52:33,799
Speaker 1: these devices. And now there are also other anemometers that

830
00:52:33,880 --> 00:52:37,640
Speaker 1: do not use this approach, they don't resemble an electric

831
00:52:37,680 --> 00:52:41,080
Speaker 1: generator in that way. They instead will count the number

832
00:52:41,080 --> 00:52:43,680
Speaker 1: of rotations of the cups within a given amount of

833
00:52:43,719 --> 00:52:46,920
Speaker 1: time in order to convert that to a wind speed.

834
00:52:47,360 --> 00:52:51,720
Speaker 1: So you might look at how many times per minute

835
00:52:52,320 --> 00:52:56,480
Speaker 1: did this rotate based upon the you know, the speed

836
00:52:56,520 --> 00:52:58,800
Speaker 1: of the wind, we're going to say that that means

837
00:52:58,840 --> 00:53:02,440
Speaker 1: it's blah blah blah. Typically these anemometers have a simple

838
00:53:02,480 --> 00:53:06,360
Speaker 1: switch that gets activated upon each rotation, and the switch

839
00:53:06,440 --> 00:53:09,520
Speaker 1: makes a notation, and you just look at the number

840
00:53:09,560 --> 00:53:13,719
Speaker 1: of notations per minute or per whatever unit of time

841
00:53:13,760 --> 00:53:16,919
Speaker 1: you're using to measure, and you convert that information over

842
00:53:17,040 --> 00:53:21,240
Speaker 1: to create the figure for miles per hour or knots

843
00:53:21,880 --> 00:53:25,400
Speaker 1: of wind speed. Or you could have a light sensor,

844
00:53:25,840 --> 00:53:28,480
Speaker 1: so imagine an anemometer. It still is one of these

845
00:53:28,520 --> 00:53:31,560
Speaker 1: pinwheel like devices. It's still spinning in the horizontal plane,

846
00:53:32,080 --> 00:53:35,640
Speaker 1: but it has a little disc that can cover up

847
00:53:36,120 --> 00:53:41,240
Speaker 1: a hole that otherwise leads down to a light sensor.

848
00:53:41,960 --> 00:53:47,560
Speaker 1: When the anemometer rotates, this disc ends up being pulled

849
00:53:47,600 --> 00:53:50,640
Speaker 1: away from the sensor so light can hit it, and

850
00:53:50,680 --> 00:53:53,880
Speaker 1: then as it continues to rotate, it covers the sensor. Again,

851
00:53:54,080 --> 00:53:56,960
Speaker 1: it just does the circular path where it is covering

852
00:53:57,000 --> 00:54:02,360
Speaker 1: and uncovering the sensor. Doing this, the sensor counts the

853
00:54:02,440 --> 00:54:06,200
Speaker 1: number of times that light is hitting the sensor. It's

854
00:54:06,320 --> 00:54:08,640
Speaker 1: very similar to that other electronic switch I was just

855
00:54:08,719 --> 00:54:11,880
Speaker 1: talking about. And again it makes a notation. And again

856
00:54:11,920 --> 00:54:14,160
Speaker 1: you just look at the number of notations per unit

857
00:54:14,200 --> 00:54:16,520
Speaker 1: of time and you use that to convert it over

858
00:54:16,600 --> 00:54:21,280
Speaker 1: two miles per hour for wind speed. But that's not all.

859
00:54:21,760 --> 00:54:25,000
Speaker 1: You don't even have to have a rotating element at

860
00:54:25,040 --> 00:54:27,920
Speaker 1: all to calculate wind speed these days, because you can

861
00:54:28,040 --> 00:54:31,799
Speaker 1: use what are called sonic anemometers. Now these are more

862
00:54:31,880 --> 00:54:35,920
Speaker 1: or less the standard for a lot of observation uh

863
00:54:36,120 --> 00:54:41,400
Speaker 1: points these days. For meteorological observations, they use ultrasonic signal

864
00:54:41,520 --> 00:54:45,279
Speaker 1: emitters and receivers mounted at right angles to each other.

865
00:54:45,360 --> 00:54:47,400
Speaker 1: So from the top it might look like a square.

866
00:54:47,480 --> 00:54:53,000
Speaker 1: You have receivers and transmitters that are mounted in a

867
00:54:53,080 --> 00:54:59,160
Speaker 1: square in relation to one another. And it's it's important

868
00:54:59,200 --> 00:55:03,600
Speaker 1: to remember sound as physical phenomenon, right. Sound is all

869
00:55:03,640 --> 00:55:08,680
Speaker 1: about molecules bashing into each other, vibrations spreading across a medium.

870
00:55:09,360 --> 00:55:14,040
Speaker 1: So when we're hearing things, we're hearing the sense of

871
00:55:14,080 --> 00:55:20,600
Speaker 1: hearing is all based upon air moving, vibrating at oscillating

872
00:55:20,680 --> 00:55:23,440
Speaker 1: at the speed of whatever caused it to move in

873
00:55:23,480 --> 00:55:28,080
Speaker 1: the first place, and it continues to make other air

874
00:55:28,120 --> 00:55:31,719
Speaker 1: molecules do this same thing until some of them end

875
00:55:31,800 --> 00:55:36,560
Speaker 1: up hitting the ear drums in our ears, which transfers

876
00:55:36,600 --> 00:55:42,040
Speaker 1: this uh this vibration to some very tiny bones in

877
00:55:42,120 --> 00:55:46,680
Speaker 1: our ears in our ears, which then transmit that vibration

878
00:55:46,719 --> 00:55:52,759
Speaker 1: to the cochlea, which ultimately interprets this as sound. That's

879
00:55:52,800 --> 00:55:56,680
Speaker 1: how how we perceive it. But that means that sound

880
00:55:56,719 --> 00:55:59,400
Speaker 1: itself is a physical thing, and you can affect it

881
00:56:00,040 --> 00:56:03,400
Speaker 1: by changing things in the air, like if wind is blowing,

882
00:56:03,600 --> 00:56:06,640
Speaker 1: it affects how sound travels. And if you've ever tried

883
00:56:06,640 --> 00:56:08,799
Speaker 1: to talk to someone on a windy day, then you've

884
00:56:08,800 --> 00:56:13,360
Speaker 1: probably experienced this at least a little bit. So the

885
00:56:13,400 --> 00:56:19,319
Speaker 1: way these ultrasonic wind anemometers work is that they transmit

886
00:56:19,520 --> 00:56:22,720
Speaker 1: signals at an ultrasonic frequency. It's too high for humans

887
00:56:22,760 --> 00:56:25,399
Speaker 1: to hear, but the receivers can pick up on it.

888
00:56:25,960 --> 00:56:29,640
Speaker 1: When wind is blowing, it's going to affect the timing

889
00:56:30,120 --> 00:56:33,520
Speaker 1: of when a transmission is sent out and when it

890
00:56:33,560 --> 00:56:38,239
Speaker 1: gets received by the other side this timing. It's super

891
00:56:38,360 --> 00:56:41,880
Speaker 1: super subtle. Uh, It's not like it's something that we

892
00:56:41,960 --> 00:56:44,719
Speaker 1: humans could detect, but these instruments can detect it, and

893
00:56:44,760 --> 00:56:48,919
Speaker 1: by detecting those changes, it can convert that into an

894
00:56:48,920 --> 00:56:52,799
Speaker 1: interpretation of how fast the wind is blowing. It's really

895
00:56:52,800 --> 00:56:55,680
Speaker 1: the difference that the it took for the sound to

896
00:56:55,760 --> 00:57:00,560
Speaker 1: get from its point of origin to its destination impaired

897
00:57:00,600 --> 00:57:04,799
Speaker 1: against what it normally would take under still conditions with

898
00:57:04,880 --> 00:57:09,000
Speaker 1: no wind present. If you ever look at technical readouts

899
00:57:09,040 --> 00:57:11,759
Speaker 1: of wind speed and direction, you might notice that there's

900
00:57:11,760 --> 00:57:15,399
Speaker 1: a lot of symbols that are used. Typically, you would

901
00:57:15,440 --> 00:57:20,240
Speaker 1: see what's called wind barbs. So first you start with

902
00:57:20,400 --> 00:57:23,560
Speaker 1: two lines representing north, south and east west in a

903
00:57:23,680 --> 00:57:27,080
Speaker 1: crosshair layout, you know, your typical north southeast west compass

904
00:57:27,160 --> 00:57:30,280
Speaker 1: rose sort of thing. And from the center, you would

905
00:57:30,360 --> 00:57:32,880
Speaker 1: have a line that would extend out towards the direction

906
00:57:33,200 --> 00:57:36,400
Speaker 1: where wind is coming from. So let's say it's coming

907
00:57:36,400 --> 00:57:39,640
Speaker 1: from the northwest. This line would extend out halfway between

908
00:57:39,640 --> 00:57:42,360
Speaker 1: north and west. If it was truly coming from the northwest.

909
00:57:43,360 --> 00:57:47,320
Speaker 1: From that line, you might notice one or more short barbs,

910
00:57:47,440 --> 00:57:49,720
Speaker 1: or even what is called a pennant. It looks like

911
00:57:49,760 --> 00:57:52,400
Speaker 1: a little flag at the end of it. Those barbs

912
00:57:52,400 --> 00:57:55,920
Speaker 1: actually represent wind speed, and the number of barbs on

913
00:57:56,000 --> 00:57:58,800
Speaker 1: there tell you how strong the wind is blowing. So

914
00:57:58,880 --> 00:58:02,840
Speaker 1: a line that has in short barb extending from it

915
00:58:02,880 --> 00:58:07,439
Speaker 1: indicates calm winds that approximately five knots. If you have

916
00:58:08,080 --> 00:58:10,360
Speaker 1: the opposite, If you have a line with has a

917
00:58:10,400 --> 00:58:13,040
Speaker 1: pennant on the end of it and two barbs extending

918
00:58:13,080 --> 00:58:15,840
Speaker 1: from it out to the side, that would indicate very

919
00:58:15,840 --> 00:58:19,360
Speaker 1: strong winds at like sixty five knots now. One of

920
00:58:19,400 --> 00:58:24,200
Speaker 1: the simpler tools in the meteorological tool kit is the

921
00:58:24,240 --> 00:58:28,440
Speaker 1: precipitation gauge. This is telling you how much precipitation has

922
00:58:28,480 --> 00:58:32,320
Speaker 1: fallen over a given amount of time. Essentially, this comes

923
00:58:32,360 --> 00:58:35,440
Speaker 1: down to a container designed to catch precipitation, so you

924
00:58:35,480 --> 00:58:38,640
Speaker 1: can see how much has fallen in that area. Now,

925
00:58:38,680 --> 00:58:43,880
Speaker 1: your basic rain gage consists of a funnel which can

926
00:58:43,920 --> 00:58:50,560
Speaker 1: capture precipitation falling precipitation. It has a measuring tube that

927
00:58:50,680 --> 00:58:55,360
Speaker 1: the funnel feeds into, and the measuring tube itself tends

928
00:58:55,360 --> 00:58:57,400
Speaker 1: to be fairly you know, not like maybe like an

929
00:58:57,400 --> 00:59:01,880
Speaker 1: inch in diameter, maybe about eight inches long. Typically, um,

930
00:59:01,920 --> 00:59:04,160
Speaker 1: it's it's a tube, it's open at the top and

931
00:59:04,200 --> 00:59:08,280
Speaker 1: close at the bottom. Then that itself is inside a

932
00:59:08,360 --> 00:59:13,040
Speaker 1: larger collecting vessel, and the collecting vessel's mouth is the

933
00:59:13,200 --> 00:59:16,200
Speaker 1: same diameter as the funnel that's at the very top,

934
00:59:16,680 --> 00:59:20,640
Speaker 1: so the funnel prevents water from falling directly into the

935
00:59:20,680 --> 00:59:26,080
Speaker 1: containment vessel. Instead it funnels the water into the tube

936
00:59:26,160 --> 00:59:30,880
Speaker 1: that's inside the collecting vessel. The tubes are calibrated to

937
00:59:31,120 --> 00:59:35,640
Speaker 1: measure the amount of rainfall based upon the diameter of

938
00:59:35,680 --> 00:59:39,280
Speaker 1: that collecting vessel's mouth, so each one is very specific

939
00:59:39,800 --> 00:59:43,439
Speaker 1: to the collecting vessel, and the scale that you will

940
00:59:43,480 --> 00:59:47,160
Speaker 1: see on these tubes has been written out to reflect

941
00:59:47,360 --> 00:59:50,760
Speaker 1: that collecting vessel. That's why if you pick up one

942
00:59:50,760 --> 00:59:53,240
Speaker 1: of these measuring tubes that's using the big funnels, and

943
00:59:53,320 --> 00:59:55,480
Speaker 1: you look on it and it looks like there's maybe

944
00:59:55,560 --> 00:59:58,760
Speaker 1: six inches of water inside the tube, but the tube

945
00:59:58,760 --> 01:00:02,600
Speaker 1: breeds that as b being uh, three quarters of an

946
01:00:02,640 --> 01:00:05,960
Speaker 1: inch of rain. You're like, well, why is that? I mean,

947
01:00:05,960 --> 01:00:08,840
Speaker 1: there's there's six inches of water inside the tube. How

948
01:00:08,840 --> 01:00:10,439
Speaker 1: can it be three quarters of an inch of rain?

949
01:00:10,880 --> 01:00:13,360
Speaker 1: It's because the funnel that's catching all that rain and

950
01:00:13,400 --> 01:00:16,120
Speaker 1: funneling it down into the tube. It's a larger diameter,

951
01:00:16,200 --> 01:00:19,000
Speaker 1: it's got more surface area, so more rain is hitting

952
01:00:19,000 --> 01:00:21,680
Speaker 1: that funnel than would have hit the tube just on

953
01:00:21,720 --> 01:00:24,720
Speaker 1: its own. Now, the reason why you have the collecting

954
01:00:24,800 --> 01:00:28,240
Speaker 1: vessel there is that sometimes you get more rain than

955
01:00:28,280 --> 01:00:30,680
Speaker 1: what the tube can handle. If the tube is calibrated

956
01:00:30,920 --> 01:00:33,080
Speaker 1: so that it can hold up to one inch of

957
01:00:33,160 --> 01:00:37,080
Speaker 1: rain compared based upon the size of the collecting vessel,

958
01:00:37,160 --> 01:00:39,360
Speaker 1: it is in what happens if you get more than

959
01:00:39,400 --> 01:00:42,080
Speaker 1: an inch of rain, well, water will start to overflow

960
01:00:42,240 --> 01:00:44,160
Speaker 1: from the top of the tube and pour into the

961
01:00:44,160 --> 01:00:47,080
Speaker 1: collecting vessel. When rain is done and you're wanting to

962
01:00:47,120 --> 01:00:49,720
Speaker 1: see how much rain has fallen, you go out, you

963
01:00:49,760 --> 01:00:52,800
Speaker 1: remove the funnel, you remove the tube, and you say,

964
01:00:52,800 --> 01:00:55,600
Speaker 1: all right, we start with one inch of rain. Because

965
01:00:55,680 --> 01:00:58,320
Speaker 1: this tube is full, that means that it rained at

966
01:00:58,360 --> 01:01:01,320
Speaker 1: least an inch. You pour that out it. Then you

967
01:01:01,360 --> 01:01:03,720
Speaker 1: take the water from the collecting vessel, you pour that

968
01:01:03,800 --> 01:01:06,400
Speaker 1: back into the tube, and you use that to measure

969
01:01:06,400 --> 01:01:09,440
Speaker 1: how much in addition to one inch has fallen. So

970
01:01:09,480 --> 01:01:11,960
Speaker 1: that's the reason for the collecting vessel and for the calibration.

971
01:01:12,360 --> 01:01:14,440
Speaker 1: Otherwise you would just have to keep building tubes that

972
01:01:14,480 --> 01:01:16,840
Speaker 1: are taller and taller and taller, and you know, if

973
01:01:16,840 --> 01:01:20,960
Speaker 1: they're narrow enough, it can give you an unrealistic account

974
01:01:21,000 --> 01:01:25,240
Speaker 1: for how much rain has fallen. That's your basic rain gage.

975
01:01:25,800 --> 01:01:29,280
Speaker 1: Um there there are other types of rain gages beyond

976
01:01:29,320 --> 01:01:32,800
Speaker 1: the basic one. There's one called the tipping bucket rain gage.

977
01:01:33,000 --> 01:01:37,560
Speaker 1: I love these. If you've ever seen fountains where there's

978
01:01:37,600 --> 01:01:41,160
Speaker 1: a small container that gradually fills up with water and

979
01:01:41,200 --> 01:01:44,080
Speaker 1: when it fills up to the top, it tips over,

980
01:01:44,280 --> 01:01:46,840
Speaker 1: dumping all the water out into the base of the fountain,

981
01:01:47,160 --> 01:01:49,040
Speaker 1: and then it tips back up again because now the

982
01:01:49,080 --> 01:01:51,600
Speaker 1: water's gone, that that counterweight has gone, so the bucket

983
01:01:51,640 --> 01:01:56,840
Speaker 1: returns to its normal, uh normal orientation. That's exactly the

984
01:01:56,960 --> 01:02:01,560
Speaker 1: way these tipping bucket rain gage is work. They work

985
01:02:01,600 --> 01:02:04,240
Speaker 1: as they have two buckets, typically on a see saw

986
01:02:04,600 --> 01:02:09,320
Speaker 1: like device, so they swivel on the seesaw device as

987
01:02:09,360 --> 01:02:12,120
Speaker 1: one fills up. It gets heavy enough once it reaches

988
01:02:12,160 --> 01:02:14,800
Speaker 1: a certain point for it to tip, pouring its water

989
01:02:14,880 --> 01:02:20,360
Speaker 1: out into a containment vessel below. The other bucket is

990
01:02:20,400 --> 01:02:23,560
Speaker 1: then tilted upward to catch the water from that point

991
01:02:23,600 --> 01:02:26,720
Speaker 1: forward until it fills up, and then it tilts again

992
01:02:27,240 --> 01:02:30,320
Speaker 1: and dumps its water. These buckets hold a very small

993
01:02:30,360 --> 01:02:34,920
Speaker 1: amount of water, typically one an inch of rain essentially,

994
01:02:35,640 --> 01:02:39,680
Speaker 1: and you have a switch that is connected to this

995
01:02:39,960 --> 01:02:45,120
Speaker 1: see saw like device, and every time it tilts, the

996
01:02:45,160 --> 01:02:48,800
Speaker 1: switches registers it. And because it registers that, it makes

997
01:02:48,800 --> 01:02:51,640
Speaker 1: a mark on the device, makes a mark on a

998
01:02:51,640 --> 01:02:56,040
Speaker 1: piece of paper or otherwise activates a counter, and that

999
01:02:56,120 --> 01:03:00,320
Speaker 1: tells you that an inch of rain has just been

1000
01:03:00,840 --> 01:03:07,360
Speaker 1: uh registered counted. And then you just add up all

1001
01:03:07,440 --> 01:03:09,840
Speaker 1: the different one one hundreds of an inch, and you

1002
01:03:09,880 --> 01:03:12,240
Speaker 1: can tell within a hundredth of an inch how much

1003
01:03:12,360 --> 01:03:14,760
Speaker 1: rain has fallen in that given area. There are even

1004
01:03:14,880 --> 01:03:17,720
Speaker 1: versions of this that are heated, where they have little

1005
01:03:17,760 --> 01:03:21,240
Speaker 1: heating elements, typically coils of wire that will heat up

1006
01:03:21,280 --> 01:03:23,640
Speaker 1: as current passes through them, and the purpose of that

1007
01:03:23,720 --> 01:03:27,320
Speaker 1: is so that they can measure frozen precipitation. As frozen

1008
01:03:27,320 --> 01:03:30,440
Speaker 1: precipitation hits the buckets, that heats up, it converts into water,

1009
01:03:31,040 --> 01:03:35,240
Speaker 1: and also it prevents the gauge itself from freezing over

1010
01:03:35,400 --> 01:03:38,360
Speaker 1: in cold weather, something that we don't get a whole

1011
01:03:38,440 --> 01:03:40,880
Speaker 1: lot of in my neck of the woods, but I

1012
01:03:40,920 --> 01:03:46,240
Speaker 1: think it's a pretty cool way of measuring rainfall. There

1013
01:03:46,240 --> 01:03:49,160
Speaker 1: are other types of rain gages. They are weighing gauges.

1014
01:03:49,400 --> 01:03:53,120
Speaker 1: Weight gauges you could say that estimate the amount of

1015
01:03:53,200 --> 01:03:57,520
Speaker 1: rain based upon the weight change. And UH, those are

1016
01:03:57,600 --> 01:04:02,880
Speaker 1: the major types of precipitation gauges. Then you have various

1017
01:04:02,920 --> 01:04:06,960
Speaker 1: devices that can detect electrical storms. UH. Basically what you

1018
01:04:07,000 --> 01:04:11,440
Speaker 1: need is an antenna. Meteorologists use thunderstorm detectors. That our

1019
01:04:11,480 --> 01:04:16,560
Speaker 1: antenna that registers spikes of electro magnetic radiation or lightning strikes.

1020
01:04:17,080 --> 01:04:19,760
Speaker 1: So if you've ever listened to a m radio during

1021
01:04:19,760 --> 01:04:24,320
Speaker 1: a thunderstorm, you may have noticed that there's this burst

1022
01:04:24,360 --> 01:04:28,840
Speaker 1: of static whenever there's a lightning strike somewhere in the area.

1023
01:04:29,080 --> 01:04:32,960
Speaker 1: Thunderstorm detectors pick up electrical discharges, typically within a couple

1024
01:04:32,960 --> 01:04:36,680
Speaker 1: of hundred miles of the detectors, so it doesn't have

1025
01:04:36,720 --> 01:04:39,280
Speaker 1: to be that close in order to pick up on it.

1026
01:04:39,280 --> 01:04:42,360
Speaker 1: It just is this little spike of electric discharge that

1027
01:04:42,400 --> 01:04:45,080
Speaker 1: the antenna can pick up on. Your basic system is

1028
01:04:45,080 --> 01:04:48,720
Speaker 1: a simple receiver. There's no transmitter, it just records it

1029
01:04:49,560 --> 01:04:52,480
Speaker 1: and using several of those sensors across the region will

1030
01:04:52,520 --> 01:04:56,160
Speaker 1: help you determine where and not just when lightning strikes.

1031
01:04:56,400 --> 01:05:00,160
Speaker 1: You can use triangulation using three or well really three

1032
01:05:00,200 --> 01:05:03,560
Speaker 1: points to figure out where did the lightning strike These

1033
01:05:03,600 --> 01:05:06,560
Speaker 1: three different detectors picked it up. Based on the timing

1034
01:05:06,800 --> 01:05:09,600
Speaker 1: of the three detections, we can say the lightning strike

1035
01:05:09,680 --> 01:05:13,880
Speaker 1: must have happened at these coordinates. It's a very simple

1036
01:05:13,920 --> 01:05:17,000
Speaker 1: way of doing it. But there are also mobile lightning

1037
01:05:17,000 --> 01:05:20,720
Speaker 1: detectors that you are typically would put in an aircraft.

1038
01:05:21,760 --> 01:05:24,800
Speaker 1: You fly a plane around a weather plane and look

1039
01:05:24,840 --> 01:05:31,880
Speaker 1: for these electra electric discharges. These will use attenuation signal

1040
01:05:31,880 --> 01:05:35,720
Speaker 1: attenuation to determine the location of lightning strikes, but that

1041
01:05:35,880 --> 01:05:40,240
Speaker 1: is not um not always accurate because it is dependent

1042
01:05:40,320 --> 01:05:45,160
Speaker 1: upon some other factors that can confound the device. But yeah,

1043
01:05:45,160 --> 01:05:48,160
Speaker 1: there's a couple of different ways of doing it. Other

1044
01:05:48,200 --> 01:05:53,480
Speaker 1: devices that meteorologists might use might include paranometers or pyranometers

1045
01:05:53,520 --> 01:05:58,640
Speaker 1: if you prefer um pyra to indicate heat that measures

1046
01:05:58,640 --> 01:06:02,200
Speaker 1: a solar radiation actually or how much sun exposure a

1047
01:06:02,280 --> 01:06:04,880
Speaker 1: place will receive over a given amount of time. These

1048
01:06:04,880 --> 01:06:08,040
Speaker 1: are also used not just for weather forecasts, but also

1049
01:06:08,120 --> 01:06:10,280
Speaker 1: when you want to figure out the best place to locate,

1050
01:06:10,360 --> 01:06:14,240
Speaker 1: say a solar panel farm, you might use a pyranometer

1051
01:06:14,720 --> 01:06:18,920
Speaker 1: to see how much solar radiation that area actually receives.

1052
01:06:19,040 --> 01:06:21,080
Speaker 1: Does it make sense to put a solar panel farm

1053
01:06:21,120 --> 01:06:24,320
Speaker 1: there or are you not going to maximize your efficiency

1054
01:06:24,560 --> 01:06:28,400
Speaker 1: if you place it there. Typically, they measure sun exposure

1055
01:06:28,440 --> 01:06:31,480
Speaker 1: by using thermopiles, which are sensors that generate electricity as

1056
01:06:31,480 --> 01:06:36,480
Speaker 1: they heat up from absorbing light. So these things absorb

1057
01:06:36,640 --> 01:06:38,920
Speaker 1: lots of light. They're very dark, they tend to be black.

1058
01:06:39,520 --> 01:06:42,000
Speaker 1: Absorbed light, they generate electricity, and then by measuring the

1059
01:06:42,040 --> 01:06:45,800
Speaker 1: electricity you understand how much sun exposure you got. Then

1060
01:06:45,840 --> 01:06:49,920
Speaker 1: there are devices called celo meters which are used to

1061
01:06:49,920 --> 01:06:54,120
Speaker 1: measure clouds, like the ceiling spelled like that. Celo meters

1062
01:06:54,440 --> 01:06:57,080
Speaker 1: they can measure cloud height and thickness. And the one

1063
01:06:57,360 --> 01:07:00,000
Speaker 1: I was looking at specifically does this in a pretty

1064
01:07:00,040 --> 01:07:05,720
Speaker 1: cool way. It shoots lasers at clouds. So the lasers

1065
01:07:05,760 --> 01:07:08,280
Speaker 1: hit the clouds, and then the laser lights starts to

1066
01:07:08,360 --> 01:07:12,080
Speaker 1: scatter as it encounters the various particles that are in

1067
01:07:12,120 --> 01:07:15,400
Speaker 1: clouds like water, vapor, and that kind of stuff. And

1068
01:07:15,440 --> 01:07:21,080
Speaker 1: then you use backscatter technology to measure that dispersal of

1069
01:07:21,200 --> 01:07:25,000
Speaker 1: light within the clouds. So you fire laser into the cloud.

1070
01:07:25,080 --> 01:07:28,200
Speaker 1: The particles in the cloud cause the laser light to

1071
01:07:28,240 --> 01:07:31,040
Speaker 1: scatter at different levels depending upon the density and composition

1072
01:07:31,040 --> 01:07:33,680
Speaker 1: of those particles, and you measure that backscattered light to

1073
01:07:33,720 --> 01:07:36,160
Speaker 1: allow you to define the parameters of the cloud and

1074
01:07:36,240 --> 01:07:38,240
Speaker 1: it's density, and even be able to tell whether or

1075
01:07:38,240 --> 01:07:41,160
Speaker 1: not precipitation is likely to fall because of those clouds.

1076
01:07:42,280 --> 01:07:45,360
Speaker 1: You've also got visibility sensors that can measure how transparent

1077
01:07:45,480 --> 01:07:48,880
Speaker 1: the air is, which might sound kind of silly until

1078
01:07:48,880 --> 01:07:52,520
Speaker 1: you remember that fog is totally a thing. Uh So

1079
01:07:52,600 --> 01:07:56,680
Speaker 1: these devices measure light attenuation and use backscatter technologies similar

1080
01:07:56,680 --> 01:07:59,200
Speaker 1: to the cealimeters I just talked about in order to

1081
01:08:00,040 --> 01:08:04,600
Speaker 1: measure visibility. So you can use optical sensors to measure

1082
01:08:04,640 --> 01:08:07,080
Speaker 1: of visibility as well, in other words, like cameras and stuff,

1083
01:08:07,120 --> 01:08:09,520
Speaker 1: and you can get a firsthand look at visibility, but

1084
01:08:09,640 --> 01:08:12,280
Speaker 1: these are looking at it on a more precise level

1085
01:08:12,280 --> 01:08:17,640
Speaker 1: than just does it look clear out there. Oh and

1086
01:08:17,720 --> 01:08:20,599
Speaker 1: Doppler radar. I can't finish this episode without talking about

1087
01:08:20,600 --> 01:08:23,280
Speaker 1: Doppler radar. If you've watched a weather report, you've likely

1088
01:08:23,280 --> 01:08:25,519
Speaker 1: heard this term bandied about when it comes to measuring

1089
01:08:25,600 --> 01:08:29,000
Speaker 1: rainstorm systems and their movements. So Doppler radar measures not

1090
01:08:29,120 --> 01:08:32,799
Speaker 1: just the presence of something but it's movement either toward

1091
01:08:33,000 --> 01:08:36,479
Speaker 1: or away from the radar station. So your basic radar

1092
01:08:36,520 --> 01:08:39,719
Speaker 1: is pretty simple. You beam out a signal in a direction.

1093
01:08:39,840 --> 01:08:43,000
Speaker 1: That signal encounters other stuff and bounces off of it,

1094
01:08:43,120 --> 01:08:45,920
Speaker 1: some of it coming back to you, and it gets

1095
01:08:45,920 --> 01:08:48,559
Speaker 1: to the starting location. If you look at the time

1096
01:08:48,840 --> 01:08:51,600
Speaker 1: between when you sent the signal out and when the

1097
01:08:51,640 --> 01:08:55,080
Speaker 1: signal came back, you can then use that to extrapolate

1098
01:08:55,160 --> 01:08:59,120
Speaker 1: how far away that thing is. And if it's stationary,

1099
01:08:59,360 --> 01:09:02,160
Speaker 1: then you're not going to see any difference in the

1100
01:09:02,240 --> 01:09:05,519
Speaker 1: frequency of the signal coming back as the one you

1101
01:09:05,600 --> 01:09:08,880
Speaker 1: sent out. Right, it should be pretty much identical, and

1102
01:09:08,920 --> 01:09:12,200
Speaker 1: you'd say, all right, there's a stationary object that's ten

1103
01:09:12,240 --> 01:09:18,640
Speaker 1: miles away. Godzilla is taking a nap now. Uh. You

1104
01:09:18,680 --> 01:09:20,800
Speaker 1: can do this, by the way, because those radio waves,

1105
01:09:20,840 --> 01:09:23,920
Speaker 1: the radar waves, are traveling at the speed of light

1106
01:09:24,080 --> 01:09:26,840
Speaker 1: right there. It's a constant speed, so you don't have

1107
01:09:26,880 --> 01:09:29,960
Speaker 1: to worry about anything else. You just say, well, I

1108
01:09:30,000 --> 01:09:32,920
Speaker 1: know how fast light travels. I know how long it

1109
01:09:32,960 --> 01:09:37,240
Speaker 1: took the returning wave to get back to me. Because

1110
01:09:37,280 --> 01:09:40,400
Speaker 1: I've got a timer. It tells me that this much

1111
01:09:40,439 --> 01:09:45,280
Speaker 1: time passed between transmission and receiving the echo. Then I

1112
01:09:45,320 --> 01:09:48,040
Speaker 1: can say, well, how far away, how far did the

1113
01:09:48,080 --> 01:09:52,440
Speaker 1: signal have to travel in order to get there and back? Um,

1114
01:09:52,479 --> 01:09:54,479
Speaker 1: And that will tell you how far away the object is.

1115
01:09:54,760 --> 01:09:58,240
Speaker 1: But you can also tell if the object is moving

1116
01:09:58,320 --> 01:10:01,679
Speaker 1: toward you or away from you, because the signals coming

1117
01:10:01,680 --> 01:10:04,080
Speaker 1: back to you will be affected by this. Uh. It

1118
01:10:04,160 --> 01:10:07,240
Speaker 1: is the Doppler effect, something that is pretty easy to

1119
01:10:07,320 --> 01:10:09,840
Speaker 1: encounter out in the real world, just on your own.

1120
01:10:09,880 --> 01:10:13,200
Speaker 1: If you've ever heard a like a police car blaring

1121
01:10:13,240 --> 01:10:16,080
Speaker 1: a siren and the police cars coming toward you and

1122
01:10:16,120 --> 01:10:19,679
Speaker 1: then it passes you, you've probably noticed that the sound

1123
01:10:19,760 --> 01:10:23,080
Speaker 1: of the siren changed as the police car passed you.

1124
01:10:23,920 --> 01:10:27,360
Speaker 1: So when the cars coming towards you, it's actually compressing

1125
01:10:27,680 --> 01:10:32,200
Speaker 1: those sound waves that are emitted by the siren. Uh.

1126
01:10:32,240 --> 01:10:36,920
Speaker 1: And because it's compressing the sound waves, UH, it means

1127
01:10:36,920 --> 01:10:40,640
Speaker 1: that it's increasing the frequency. It's like physically compressing, not

1128
01:10:40,800 --> 01:10:44,479
Speaker 1: digitally compressing. We're talking about physically compressing those waves so

1129
01:10:44,520 --> 01:10:47,479
Speaker 1: that the frequency is increased. That means the pitch goes up,

1130
01:10:47,800 --> 01:10:50,479
Speaker 1: so you hear a higher pitch noise as the cars

1131
01:10:50,520 --> 01:10:54,919
Speaker 1: moving away. It's along gating those sound waves, it's stretching

1132
01:10:54,960 --> 01:10:59,600
Speaker 1: them out which means decreasing the frequency and us decreasing

1133
01:10:59,640 --> 01:11:03,400
Speaker 1: the pitch, making it a lower pitch. Well, radar has

1134
01:11:03,439 --> 01:11:07,360
Speaker 1: the same shifts with its signals if it hits something

1135
01:11:07,400 --> 01:11:10,080
Speaker 1: that's moving toward it. So you've got a radar station

1136
01:11:10,479 --> 01:11:13,719
Speaker 1: shoots out a little radar beam. The radar beam comes

1137
01:11:13,760 --> 01:11:18,400
Speaker 1: back and the frequency is shorter like it's it's the

1138
01:11:18,560 --> 01:11:21,679
Speaker 1: or the frequency has been increased. The wavelength is shorter.

1139
01:11:22,400 --> 01:11:25,400
Speaker 1: That tells you that the objects moving towards you. It

1140
01:11:25,560 --> 01:11:32,439
Speaker 1: is compressed the length the wavelength of that of that signal.

1141
01:11:33,320 --> 01:11:36,280
Speaker 1: If the wavelength is longer, tells you that the object

1142
01:11:36,320 --> 01:11:39,800
Speaker 1: is moving away from you. That the frequency has hit

1143
01:11:39,840 --> 01:11:42,599
Speaker 1: the object, but the objects moving away and thus the

1144
01:11:42,680 --> 01:11:47,120
Speaker 1: returning waves have an elongated wavelength. So Doppler radar is

1145
01:11:47,240 --> 01:11:50,360
Speaker 1: very cool and that it can tell you where a

1146
01:11:50,680 --> 01:11:53,200
Speaker 1: storm system is and whether or not it's moving toward

1147
01:11:53,280 --> 01:11:56,240
Speaker 1: you or away from you. Um and you use multiple

1148
01:11:56,280 --> 01:11:59,559
Speaker 1: observation stations with Doppler radar to get a full picture

1149
01:12:00,680 --> 01:12:03,080
Speaker 1: where is the system going. You can even detect things

1150
01:12:03,160 --> 01:12:07,679
Speaker 1: like precipitation using Doppler radar. The cool thing about Dopper

1151
01:12:07,800 --> 01:12:10,439
Speaker 1: radar in my mind is that it is a lazy,

1152
01:12:10,520 --> 01:12:14,679
Speaker 1: lazy worker. And by that I mean in a typical hour,

1153
01:12:15,360 --> 01:12:19,160
Speaker 1: the Doppler radar is actively sending out signals for about

1154
01:12:19,320 --> 01:12:22,920
Speaker 1: seven seconds total out of the entire hour, not all

1155
01:12:22,960 --> 01:12:25,720
Speaker 1: at once, but if you look at an entire hour

1156
01:12:25,840 --> 01:12:27,880
Speaker 1: and you measure the amount of time that the Dopper

1157
01:12:27,960 --> 01:12:32,280
Speaker 1: radar was sending signals out, it averages to about seven seconds.

1158
01:12:32,880 --> 01:12:36,439
Speaker 1: It's spending the other fifty nine minutes and fifty three

1159
01:12:36,479 --> 01:12:41,800
Speaker 1: seconds listening, Which seems like a great job to me

1160
01:12:42,280 --> 01:12:44,479
Speaker 1: to work for seven seconds and then just listen for

1161
01:12:44,479 --> 01:12:46,720
Speaker 1: fifty nine three seconds, But I guess it depends on

1162
01:12:46,720 --> 01:12:50,120
Speaker 1: what you're listening to. In this case, it's listening for

1163
01:12:50,160 --> 01:12:53,800
Speaker 1: those echoes, those returning frequencies for the rest of the hour.

1164
01:12:53,920 --> 01:12:57,320
Speaker 1: And again not all in one batch, it's spread throughout

1165
01:12:57,360 --> 01:13:01,080
Speaker 1: the hour, but collectively we're talking fifty nine minutes fifty

1166
01:13:01,080 --> 01:13:06,720
Speaker 1: three seconds of listening. Uh. It is scanning the sky

1167
01:13:06,760 --> 01:13:09,000
Speaker 1: in a series of angles. So think of a Doppler

1168
01:13:09,080 --> 01:13:11,760
Speaker 1: radar like a think of like a little satellite dish,

1169
01:13:11,840 --> 01:13:16,479
Speaker 1: and you start off at say forty five degree angle

1170
01:13:16,760 --> 01:13:19,200
Speaker 1: pointed at the sky, and then you move it up

1171
01:13:19,200 --> 01:13:22,519
Speaker 1: to seven degrees for the next scan and so on

1172
01:13:22,560 --> 01:13:25,439
Speaker 1: and so forth, and it's also rotating, so it's taking

1173
01:13:25,560 --> 01:13:29,000
Speaker 1: scans of different levels of elevation. In fact, they call

1174
01:13:29,120 --> 01:13:34,760
Speaker 1: these elevation slices in the Doppler radar gang and UH

1175
01:13:34,960 --> 01:13:40,000
Speaker 1: it gives the system a volume coverage pattern or VCP. Now,

1176
01:13:40,080 --> 01:13:42,439
Speaker 1: once it goes through all of its elevation slices and

1177
01:13:42,479 --> 01:13:46,559
Speaker 1: all of its rotations, it completes one volume scan, and

1178
01:13:46,640 --> 01:13:50,360
Speaker 1: it does this every five minutes or so during precipitation

1179
01:13:50,400 --> 01:13:53,880
Speaker 1: mode scans. The data that comes back can then be

1180
01:13:53,960 --> 01:13:57,280
Speaker 1: interpreted to build out a picture of weather systems where

1181
01:13:57,280 --> 01:14:00,360
Speaker 1: they are moving and how quickly they are moving. And

1182
01:14:00,439 --> 01:14:04,000
Speaker 1: that even includes active precipitation, which is pretty cool stuff.

1183
01:14:04,040 --> 01:14:08,400
Speaker 1: I think now that wraps up the basic tools and

1184
01:14:08,479 --> 01:14:11,280
Speaker 1: sensors that meteorologists used. Not keep in mind, there are

1185
01:14:11,360 --> 01:14:14,720
Speaker 1: other ones I didn't talk about, satellites, which are very important.

1186
01:14:15,000 --> 01:14:18,479
Speaker 1: Satellites also gather a lot of data about active weather

1187
01:14:18,560 --> 01:14:21,439
Speaker 1: systems on the Earth, and that data gets fed into

1188
01:14:21,479 --> 01:14:26,040
Speaker 1: computer models or weather forecasts. UH. There are other sensors

1189
01:14:26,040 --> 01:14:27,880
Speaker 1: and tools as well, but I wanted to cover the

1190
01:14:27,880 --> 01:14:30,639
Speaker 1: ones that you would find at your typical observation station

1191
01:14:30,760 --> 01:14:34,920
Speaker 1: on the ground. Keeping in mind there are others, So

1192
01:14:35,720 --> 01:14:39,840
Speaker 1: I hope I've given you an indication of how complex

1193
01:14:39,880 --> 01:14:43,720
Speaker 1: this is just from the types of information alone that

1194
01:14:43,840 --> 01:14:47,559
Speaker 1: have to be gathered and poured into these computer models

1195
01:14:47,920 --> 01:14:51,960
Speaker 1: so that we can get accurate weather forecasts. In our

1196
01:14:52,000 --> 01:14:56,000
Speaker 1: next episode, I'll talk specifically about how those weather models

1197
01:14:56,040 --> 01:15:00,519
Speaker 1: are constructed and how they generate forecasts, and the different

1198
01:15:00,560 --> 01:15:03,800
Speaker 1: models that are out there, and why are there different models,

1199
01:15:03,840 --> 01:15:07,439
Speaker 1: and what are the computer systems that are actually running

1200
01:15:07,760 --> 01:15:11,800
Speaker 1: these simulations, why are we using supercomputers? And will we

1201
01:15:11,880 --> 01:15:16,360
Speaker 1: ever get a computer model so comprehensive that we'll never

1202
01:15:16,400 --> 01:15:19,439
Speaker 1: be surprised by the weather again. Well, we'll talk about

1203
01:15:19,439 --> 01:15:22,400
Speaker 1: that in our next episode. Guys, if you have suggestions

1204
01:15:22,400 --> 01:15:25,519
Speaker 1: for future episodes of tech Stuff, let me know, would you.

1205
01:15:25,520 --> 01:15:28,120
Speaker 1: You can send me an email. The address is tech

1206
01:15:28,240 --> 01:15:31,680
Speaker 1: stuff at how stuff works dot com, or you can

1207
01:15:31,760 --> 01:15:34,960
Speaker 1: drop me a line using Twitter or Facebook. The handle

1208
01:15:34,960 --> 01:15:37,840
Speaker 1: of both of those is text stuff h s W.

1209
01:15:38,640 --> 01:15:42,000
Speaker 1: You can also drop by Twitch dot tv slash tech stuff,

1210
01:15:42,000 --> 01:15:45,439
Speaker 1: and you can watch me record these shows live like

1211
01:15:45,520 --> 01:15:49,080
Speaker 1: the audience I have watching me right now. I record

1212
01:15:49,160 --> 01:15:52,639
Speaker 1: on Wednesdays and Friday's. Just go to Twitch dot tv

1213
01:15:52,840 --> 01:15:55,439
Speaker 1: slash tech Stuff and you can see the schedule there

1214
01:15:55,840 --> 01:16:04,080
Speaker 1: and I'll talk to you guys again really soon for

1215
01:16:04,160 --> 01:16:06,479
Speaker 1: more on this and thousands of other topics, because it

1216
01:16:06,560 --> 01:16:17,320
Speaker 1: how staff works. Dot com