Speaker 1: Brought to you by the reinvented two thousand twelve Camray.
Speaker 1: It's ready. Are you get in touch with technology with
Speaker 1: tech Stuff from how stuff works dot com. Hello everyone,
Speaker 1: welcome to tech Stuff. My name is Chris Poulette, and
Speaker 1: I am an editor at how stuff works dot com.
Speaker 1: Sitting across from me as always, at least as far
Speaker 1: as I can tell, here in the Dark his senior
Speaker 1: writer Jonathan Strickland when the night has come and the
Speaker 1: land is dark and the moon is the only light
Speaker 1: we will see, as an especially good one for today's episode. Yeah,
Speaker 1: I've been trying to theme them a little. Uh. You
Speaker 1: can tell the theme ones because those are the ones
Speaker 1: where I thought about finding the quote before we started recording.
Speaker 1: And most of the time he goes, oh wait, wait, wait,
Speaker 1: I gotta think of a quote. Yeah, exactly, that's that's
Speaker 1: the problem. Usually it's just when we hit record and uh,
Speaker 1: and I strugged. I struggled to find some lyric. But
Speaker 1: any way, let's move on to today's topic, which is
Speaker 1: night vision. And we've had a couple of people asked
Speaker 1: us to cover night vision and people were just curious,
Speaker 1: you know, how does this work? What does how are
Speaker 1: we able to create electronics that allow us to see
Speaker 1: in near perfect darkness, and so we're going to kind
Speaker 1: of cover that. Night vision The technology dates back to
Speaker 1: the late thirties early forties. It was technology that was
Speaker 1: developed during World War Two and used mainly by the American, British,
Speaker 1: and Soviet forces during World War Two, although other nations
Speaker 1: began to to develop their own version of night vision
Speaker 1: technology around the same time. Well, yeah, the Germans, UH.
Speaker 1: A lot of what we had as far as our
Speaker 1: technology in the United States was based on some German
Speaker 1: research that was done in the late thirties. UM. And
Speaker 1: really what it comes down to, UM is the spectrum
Speaker 1: of light that that you're trying to see. Yeah, it's
Speaker 1: it's two different things. It's trying to accept other parts
Speaker 1: of light that human eye is not able to detect,
Speaker 1: and also to uh to amplify whatever little light is there.
Speaker 1: There are two main ways of achieving a night vision
Speaker 1: UH technology. One is called image enhancement, and that's where
Speaker 1: you're taking the little amount of light that's out there
Speaker 1: and UH and trying to amplify it so that you know,
Speaker 1: you're able to see better in that environment. And the
Speaker 1: other is thermal imaging, which is also you know, we
Speaker 1: think of that as being able to see heat. You know,
Speaker 1: the whole idea about like if you've ever seen that
Speaker 1: documentary Predatory, the Predator actually uses both forms of this,
Speaker 1: but the thermal imaging would be the one where it
Speaker 1: switches and it's that really colorful display where the hotter
Speaker 1: things in the field of vision are a brighter color,
Speaker 1: usually red, uh, and then the cooler things are are
Speaker 1: in the other part of the spectrum of light, so
Speaker 1: they'd be you know, if it's cold, it might be black,
Speaker 1: but if it's cooler, it might be blue or even
Speaker 1: kind of an indigo color. Um. Both of those are
Speaker 1: ways of achieving night vision. I think the one that
Speaker 1: most people think of when they think of night vision
Speaker 1: is the one where you've got the greenish uh display.
Speaker 1: That's the image enhancement approach, And well, you know that
Speaker 1: that's I think that's the reason people think about it
Speaker 1: is because it's used that way in TV and the movies. Yeah,
Speaker 1: probably so as a visual clue to the viewer that hey,
Speaker 1: we're doing something that you can't normally do, right. Yeah.
Speaker 1: I In fact, I watched a movie just last night
Speaker 1: that involved having a night vision the screen tinged night
Speaker 1: vision and it was and I'm not going to call
Speaker 1: it a documentary because that's how much of a skeptic
Speaker 1: I am. It was paranormal activity too. And uh, you
Speaker 1: know in paranormal activity those movies, those are done as
Speaker 1: found footage movies, which, in case you're not familiar with
Speaker 1: the term, that's the idea where the film is presented
Speaker 1: as if it were uh collection of clips taken from
Speaker 1: various cameras that it wasn't meant to be a feature
Speaker 1: film is supposed to be actual footage shot of something, right,
Speaker 1: So clover Field is another example, or Blair Witch Project.
Speaker 1: There's another example. The first time I thought about yeah,
Speaker 1: and that it's really popular with the horror crowd. Uh
Speaker 1: and uh so the paranormal activity too. There's one of
Speaker 1: the cameras that is being used in that has a
Speaker 1: night vision setting and it's using the image enhancement approach.
Speaker 1: By the way, in case you're curious about why green,
Speaker 1: the the answer I found through my research was that
Speaker 1: the reason why you get green images is not because
Speaker 1: of any technological limitation. It's because does if you're in
Speaker 1: an environment where you're using night vision. You want to
Speaker 1: be able to switch between night vision and your normal
Speaker 1: vision as quickly as possible. But if you use really
Speaker 1: intense light, and in some of the brighter lights, your
Speaker 1: pupils will constrict as you're looking at it, which means
Speaker 1: when you take the night vision glasses off, it's going
Speaker 1: to take more time for your eyes to readjust to
Speaker 1: the darkness around you. But the green that is used
Speaker 1: is a more subtle light, and so your your pupils
Speaker 1: are remain mostly dilated. So when you remove the night
Speaker 1: vision goggles, you don't have as long a time to adjust.
Speaker 1: It doesn't take as long for you to adjust to
Speaker 1: night regular night vision like our natural night vision. Uh,
Speaker 1: when you when you go back and forth, And that
Speaker 1: kind of makes sense to me, I mean, if you
Speaker 1: especially when you consider that night vision was really originally
Speaker 1: used as a military technology, you would want to be
Speaker 1: able to have as much versatility and flexibility as possible
Speaker 1: so that you can adapt to whatever the situation calls for. Yeah,
Speaker 1: that makes sense, Its sense to me. So Yeah, so
Speaker 1: at least according to that, we could in theory have
Speaker 1: night vision where it's any color. Uh, you know, it
Speaker 1: probably still probably be monochromatic, but we'll get into that
Speaker 1: when we get into the you know exactly what's happening.
Speaker 1: So so all the different kinds of night vision lie
Speaker 1: at least somewhat on the infrared, uh, part of the
Speaker 1: spectrum of light, right, and that infrared spectrum of light
Speaker 1: is outside the range of uh, the visible light spectrum. UM.
Speaker 1: In fact, there are three parts to the infrared spectrum,
Speaker 1: which is near infrared, and that's the closest one to
Speaker 1: the visible spectrum spectrum. Yes, I can say that word
Speaker 1: mid infrared um and that has uh oh, I didn't
Speaker 1: mention the wavelengths. The wavelengths for near infrared are from
Speaker 1: point seven to one point three microns um. Mid infrared
Speaker 1: has wavelengths from one point three to three microns um.
Speaker 1: And then thermal infrared, which is the biggest part of
Speaker 1: the infrared spectrum, and that's from three to more than
Speaker 1: thirty microfs. Yeah, and so the the thermal infrared you're
Speaker 1: talking at that point about infrared radiation really heat in
Speaker 1: other words, is what's kind of how we perceive it usually,
Speaker 1: but uh, that's something that's actually given off by an
Speaker 1: object itself, whereas when we're talking about visible light. That's
Speaker 1: something that's reflected off of an object. Right, So if
Speaker 1: if I'm looking at a tree in sunlight, what I'm
Speaker 1: seeing is the light being reflected off of that tree.
Speaker 1: It's that light's hitting my eyes then going through the
Speaker 1: whole focal point, getting into my brain and somewhere up
Speaker 1: there in that Yeah, somewhere up there in the gray matter,
Speaker 1: my brain says, Hello, that's a tree, possibly a large
Speaker 1: a large. Um, I recognize that from very far away. Yes,
Speaker 1: that's how to recognize treats from very far away, quite
Speaker 1: a long way away. Uh. Yeah, So that's how that
Speaker 1: would normally work with thermal infrared. If I were to
Speaker 1: see an object using thermal infrared, Let's say that somehow
Speaker 1: I have that ability. You know, we're not talking about
Speaker 1: technology here, but I somehow have the the the natural
Speaker 1: ability to see the thermal infrared. It happened when they
Speaker 1: shot him into space and he was bombarded by cosmic
Speaker 1: waves while we're really just pop culturing this all to
Speaker 1: heck and back. So yeah, with the thermal infrared ability,
Speaker 1: I would be able to see the energy that is
Speaker 1: being emitted by any particular object. Uh. It's not necessarily light.
Speaker 1: That's reflecting off. In fact, there doesn't have to be
Speaker 1: any sort of light source at all. It just so.
Speaker 1: And if I were in a perfectly dark room and
Speaker 1: there was another object there that's giving off heat, essentially,
Speaker 1: I would be able to see it because I would
Speaker 1: be seeing in that range even though there's no other
Speaker 1: light source coming in. It would just be that I've
Speaker 1: actually seeing that that energy. Because we'll get into why
Speaker 1: it's kind of interesting. Has to do with excitation, but
Speaker 1: not good vibrations. Yeah, although perhaps that lady was a
Speaker 1: will never mind, so moving on. She was made up
Speaker 1: of atoms, that's true. But before we get into the
Speaker 1: whole atoms and thermal infrared, let's let's talk about the
Speaker 1: image enhancement approach first because that's the one that's the
Speaker 1: most familiar and uh, it's kind of uh interesting. Um.
Speaker 1: The way that it works currently is that you've got
Speaker 1: you've got very basic parts to a particular kind of
Speaker 1: night vision. You've got you've got your lens. That's where
Speaker 1: the light is going through. The objective lens. Just a
Speaker 1: lens that catches a lens. Yeah, it catches ambient light,
Speaker 1: it catches near infrared light. So this is the near
Speaker 1: infrared spectrum, the light that's closest to the visible spectrum.
Speaker 1: Now that light is sent to a tube, and that
Speaker 1: tube is called the image intensive fire tube tense. Yeah,
Speaker 1: and the drinking energy drinks all day and yeah. So
Speaker 1: you can think of this tube. It's almost like a
Speaker 1: vacuum tube. In fact, there it is, There is a
Speaker 1: vacuum in side of it. So you think of this
Speaker 1: sort of a imagine a glass vial all right. In
Speaker 1: the middle of this glass vial or on one end
Speaker 1: of the glass vile, you've got something called a photo cathode. Now,
Speaker 1: the photo cathode takes photons. Those are those individual elements
Speaker 1: of energy for light, yes, and and those come in
Speaker 1: the entire spectrum of light um, so infrared. There are
Speaker 1: infrared photons just as there are visible light photons. So
Speaker 1: the photo cathode converts photons into electrons. It's it's one
Speaker 1: of those, uh so it changes light into electricity essentially. Yeah.
Speaker 1: And if you listen to our episode about high speed
Speaker 1: and low speed photography, we talked about how there are
Speaker 1: certain types of materials that when a photon strikes it,
Speaker 1: it causes a reaction. That's the case here a photocathode.
Speaker 1: It's that's the and that's how it behaves. When a
Speaker 1: photon hits it, it gives off an electron. Uh. So
Speaker 1: you've got the photocathode at one end of this tube,
Speaker 1: and that's where the light that's being captured by the
Speaker 1: lens is directed to the photo cathode. The electrons emitted
Speaker 1: by the photo cathode then have to pass through what
Speaker 1: is called a micro channel plate or or m c P.
Speaker 1: That's a little glass disc. Yeah, I see, I thought
Speaker 1: MCP was the master control program end of line is Okay, However,
Speaker 1: two different mcps. Well, it was until Tron got a
Speaker 1: hold of it, that's right. So glass disc Tron, m
Speaker 1: c P. I'm sensing some convergence here again. Ye. So anyway,
Speaker 1: you've got this glass, little tiny glass disc called a
Speaker 1: micro channel plate and has lots and lots of channels.
Speaker 1: That's why it's called a micro channel plate. Lots of
Speaker 1: channels that go through this plate. Okay, So think of
Speaker 1: the plate. Think of it like a dish. You got
Speaker 1: a dish, put it up on its side, and it
Speaker 1: has a whole bunch of holes drilled in it. Now,
Speaker 1: those holes are what allow electrons to pass through. But
Speaker 1: there's also an electrode on either side of the dish.
Speaker 1: So electrons coming from the photo cathode strike one side
Speaker 1: of this micro channel plate and start to go through
Speaker 1: one of the channels, and they're going through in the
Speaker 1: same direction they came from the the from the photo
Speaker 1: cathode UH section of this this UH this image intensive
Speaker 1: ire tube. So the photon converts to electron. Electron goes
Speaker 1: through this channel. As it goes to the channel, it
Speaker 1: starts to actually set off a well a reaction and
Speaker 1: it basically functions as a multiplier for the electrons. It's
Speaker 1: called a cascaded secondary emission. So this is where when
Speaker 1: electron collie collides with something inside that that channel, it
Speaker 1: starts to set off other electrons uh down that same pathway.
Speaker 1: And there's a voltage applied to those electrodes that's channeling
Speaker 1: the electrons through that pathway, like that's why they're going
Speaker 1: in that direction. So you've got more and more electrons
Speaker 1: bouncing off of each other through these channels, which means
Speaker 1: that you've you've created an amplifier and UH, if you
Speaker 1: guys want to know kind of like a big picture
Speaker 1: way of what this might look like. Imagine having a
Speaker 1: h and you can see play of videos of this
Speaker 1: on YouTube. But imagine having a big glass container filled
Speaker 1: with mouse traps, and each mouse trap has a ping
Speaker 1: pong ball set on it, and then you drop a
Speaker 1: ping pong ball into the the glass chamber and that
Speaker 1: will set off a mouse trap, And as the ping
Speaker 1: pong balls bounce around, they set off more and more
Speaker 1: mouse traps, so soon the glass case like within a
Speaker 1: fraction of the second ball. The balls are bouncing everywhere, right,
Speaker 1: same sort of idea here with the microchannel plate, except
Speaker 1: that we're talking on a sub atomic level, and we're
Speaker 1: talking about something that's really channeled, really has a firm direction.
Speaker 1: So instead of the electrons bouncing everywhere, they're going in
Speaker 1: a very specific direction. Right now, when they get to
Speaker 1: the other side of that micro channel plate, you've got
Speaker 1: the electron still traveling in the same direction they were
Speaker 1: when they came in on the front side, but now
Speaker 1: there are way more electrons, right, just amplified the number.
Speaker 1: The electrons then hit a screen that's coated with phosphors. Now,
Speaker 1: phosphors phosphors do there, they're kind of like the opposite
Speaker 1: of the photo cathode. Right, they take when the electron
Speaker 1: strikes the phosphoor, they give off light, So you're changing
Speaker 1: the electron back to a pot photon. Right. But now,
Speaker 1: because there are more electrons coming through hitting that phosphoor
Speaker 1: than they were coming in, the light that's generated is
Speaker 1: much greater in intensity than the light that was coming in.
Speaker 1: So you've ample vide the light. Now that information that
Speaker 1: light is sent to a viewer of some type. It
Speaker 1: could just be a regular lens, which is usually called
Speaker 1: the ocular lens, or it could be sent to a monitor.
Speaker 1: So if you have a night a pair of night
Speaker 1: vision goggles or a night vision scope, that's what you're seeing.
Speaker 1: You're seeing that amplified light hitting the lens or the
Speaker 1: Monitor's pretty cool, it's pretty awesome. Right. And again, this
Speaker 1: isn't just the the visible light, the ambient visible light
Speaker 1: that's out there, but also the infrared light so um
Speaker 1: because those photons, you know, it doesn't you know, the photons,
Speaker 1: It doesn't matter if it's visible or not. Um. And uh,
Speaker 1: the more light that's hitting certain areas, that the brighter
Speaker 1: it's going to be for whatever it is you're looking at.
Speaker 1: So if you're looking at something that's that's fairly reflective.
Speaker 1: Um you're gonna be able to see it in higher
Speaker 1: definition than you could with something that is not as reflective. Uh. Now,
Speaker 1: there are different ways of actually achieving this too. You
Speaker 1: can have a various there are various generations of this technology,
Speaker 1: all right, So the earliest generation of this technology actually
Speaker 1: involved shining infrared light at the objects you're looking at
Speaker 1: through the through the night vision goggles. Right, So when
Speaker 1: that that infrared light was reflected, then you would be
Speaker 1: able to see it, right, because these goggles were not
Speaker 1: so sensitive as to be able to take just the
Speaker 1: ambient light. If you did that, you would probably get
Speaker 1: you you might be able to see marginally better than
Speaker 1: you would if you had just use your regular vision.
Speaker 1: But using this infrared flashlight, essentially you could illuminate the
Speaker 1: scene and be able to see it through the night
Speaker 1: vision goggles. But if you did not have the goggles,
Speaker 1: because infrared light falls outside the visible spectrum, any independent
Speaker 1: observer wouldn't be able to tell you were doing Yeah, now,
Speaker 1: uh I UM I did some research on the the
Speaker 1: US military website about the history of of night vision,
Speaker 1: and apparently UM they sent about three hundred sniper scopes
Speaker 1: over to be used in the Pacific theater during World
Speaker 1: War Two, but they didn't get used very much because
Speaker 1: of the way that the technology worked. Um they really
Speaker 1: could see less than a hundred yards, so they weren't
Speaker 1: very effective, right because again, since it's dependent upon a
Speaker 1: reflected ray of infrared light, if it's you know, the
Speaker 1: rays starting to dispersees as it goes out, Right, it's
Speaker 1: not not a not a concentrated like a laser beam. Yeah,
Speaker 1: it's not a beam. It does disperse and diffuse as
Speaker 1: it goes out. So the further away your target, the
Speaker 1: less likely you're going to be able to see it.
Speaker 1: And even with a really really advanced version. That's by
Speaker 1: the way, it's called active infrared because you're actively beam
Speaker 1: infrared radiation out in order to try and see uh,
Speaker 1: stuff coming back through the monitors. Um if because because
Speaker 1: you're relying on that reflection, if it's too far away,
Speaker 1: you're not gonna be all se very well. So obviously
Speaker 1: a sniper rifle where at least in theory, you want
Speaker 1: to be able to put your snipers at a good
Speaker 1: distance away from the targets to maximize their effectiveness and
Speaker 1: minimize the chance that they will be targeted. Um, it doesn't.
Speaker 1: It's not so effective if you know your your distance
Speaker 1: is cut down that dramatically. Yeah. Plus, the first generation
Speaker 1: wasn't exactly um useful for someone like a sniper, considering
Speaker 1: the batteries were huge and the I R emitters had
Speaker 1: to be carried on flatbed trucks. It's hard to put
Speaker 1: one of those up in a tree. Yeah. Yeah, it
Speaker 1: turns out that also all of these are going to
Speaker 1: involve having a power supply of some sort. But for
Speaker 1: the active infrared it requires even lot more energy because
Speaker 1: you're not you're not just for your your actual night
Speaker 1: vision device, whether it's a scope or goggles or whatever,
Speaker 1: but also for the emitter. By the way, that generation
Speaker 1: is normally referred to as generation zero for a night vision.
Speaker 1: Generation one was the first generation using passive infrared system. Now,
Speaker 1: this was the kind of of night vision goggles or
Speaker 1: scope that could just use the ambient light in the area,
Speaker 1: although it needed a good amount of the ambient light.
Speaker 1: So moonlight or starlight should say starlight, Yeah, that's what
Speaker 1: it was. Yeah, the U. S Army they called it starlight. Uh,
Speaker 1: the without the moon or stars you wouldn't be able
Speaker 1: to see very much, so on an overcast night it
Speaker 1: would not be terribly useful. But on a clear day,
Speaker 1: you could see forever. You're got a clear day, you
Speaker 1: don't need night vision. Okay, starlight first star I see tonight. Um,
Speaker 1: So yeah, it was better than generation zero. Still still
Speaker 1: pretty far acry from what we have today. Although interestingly,
Speaker 1: if you were to go out and buy a pair
Speaker 1: of night vision goggles, you know, a consumer brand version
Speaker 1: would probably be Generation one. I guess you know. That's
Speaker 1: the military tends to reserve the more the more advanced
Speaker 1: forms UH generation too, it's possible that they could be
Speaker 1: generation two as well. Generation two where they had better
Speaker 1: UH image in tensi fire tubes, which meant that they
Speaker 1: could use them in extreme low light conditions. So on
Speaker 1: a moonless night, you could use these and it would
Speaker 1: be UH strong enough to be able to to amplify
Speaker 1: that light so you can see. Generation three is what
Speaker 1: you can find in the US military now. Um. And
Speaker 1: that is they used a new kind of photo cathode
Speaker 1: called gallium marsonite, so it's even more sensitive than the
Speaker 1: previous ones, which means that you know, it's it's not
Speaker 1: that the Uh, they've really advanced the technology that much.
Speaker 1: They just found them material that that emits electrons much
Speaker 1: more readily than others. Yeah. As a matter of fact,
Speaker 1: I believe we talked about gallium arson and when we
Speaker 1: talked about transistors, I believe we did back. Yeah, and
Speaker 1: then we have generation four, which is yet more improvements. Uh.
Speaker 1: And it works both in in low and high level
Speaker 1: light environments. Which that's important too, because some sometimes you're
Speaker 1: in an environment where you're gonna have more light than
Speaker 1: uh than Well, let's take two separate nights. Okay, we
Speaker 1: have one night where let's say there's a lot of moonlight, Uh,
Speaker 1: there's starlight. There might even be some some lights set
Speaker 1: up in whatever it is you're looking at, Like let's
Speaker 1: say it's an enemy encampment. Let's say you're sniper looking
Speaker 1: at an enemy encampment. Uh. If you're using a device
Speaker 1: that's meant for low light environments, you might not be
Speaker 1: able to see anything anyway because all of that light
Speaker 1: just overwhelms the device, and so you all you see
Speaker 1: is just a big green screen. Uh. So you need
Speaker 1: to have one that can work in both kinds of situations.
Speaker 1: UM So, Yeah, that's your basic that's your basic uh
Speaker 1: image enhancement style night vision. Now, I guess we can
Speaker 1: move on to the the thermal devices, which again can
Speaker 1: look at you can look at stuff and see the
Speaker 1: energy it's giving off, the light it's giving off even
Speaker 1: though light, uh, an outside source of light isn't necessarily
Speaker 1: present m and this has to and this involves the
Speaker 1: whole concept of excitation. Yeah. Yeah, Now you have to
Speaker 1: have a special type of lens to use when you're
Speaker 1: working with thermal imaging, basically to identify the infrared light.
Speaker 1: And you've got to uh, what happens is once the
Speaker 1: light is focused through the lens um, a phased array
Speaker 1: of infrared detector elements scans it um basically trying to
Speaker 1: create a dn called a thermogram, which shows you the
Speaker 1: different ranges in temperature um. And this can be done
Speaker 1: pretty quickly, about on a second, So like okays a
Speaker 1: second essentially, yeah, and concerning that film is twenty four
Speaker 1: frames a second. That is that's fast. Yeah, It's fast
Speaker 1: enough so that you can get a good view. So
Speaker 1: even if something's in motion, you should be able to
Speaker 1: get a pretty good view of it. Yeah. And then
Speaker 1: and then very much like the other style. It creates
Speaker 1: a thermogram UH and then translates it into UH an
Speaker 1: electric impulse UM just like that, and then it's sent
Speaker 1: to a signal processing unit which is basically UH electronic
Speaker 1: circuit board UM, and UH. Instead of converting electrons to photons,
Speaker 1: it actually creates display of information UM. So it's more
Speaker 1: like a computer than it is UH. An ocular system
Speaker 1: with the Yeah, you wouldn't have a lens. You would
Speaker 1: have a monitor of some site, some type. Now that
Speaker 1: monitor might be small, so it could be a monitory. Yeah,
Speaker 1: it could even fit into a headset or or binoculars
Speaker 1: or whatever. Um. Yeah, this is the what I was
Speaker 1: talking about with the the documentary Predator, where you've got
Speaker 1: the different colors representing different temperatures. So if you've ever
Speaker 1: watched any ghost hunting shows where they use thermal detectors
Speaker 1: to try and see if there are cold or warm spots,
Speaker 1: that's what they're using. By the way, just so just
Speaker 1: side note, the air can actually retain heat for a
Speaker 1: good amount of time. So let's say that you're with
Speaker 1: a big crew of people down in a cold basement
Speaker 1: and you've set up a bunch of lights and stuff,
Speaker 1: and you're filming some things, and then you turn the
Speaker 1: lights off and you go and you turn on the
Speaker 1: thermal imaging detector and you see this hot spot in
Speaker 1: the air that could possibly be generated by someone who
Speaker 1: had been standing there for about five or ten minutes,
Speaker 1: or even a light that have been turned on, not
Speaker 1: necessarily a paranormal, uh ghostly presence. Okay, rent Over, I
Speaker 1: was actually going to use Blue Thunder as an example.
Speaker 1: Like they used to they would fly outside and hover
Speaker 1: outside the window and they could see the shapes where
Speaker 1: people were, Which is funny because when you when you
Speaker 1: mentioned it like that and the movies and TV uh,
Speaker 1: when a person moves across the room, the heat stay,
Speaker 1: you know, stays with the person. It makes very identifiable
Speaker 1: human shape. It's very very much defined to that particular shape.
Speaker 1: It seems like in the case of since the air
Speaker 1: can retain heat, it seems like they would leave a
Speaker 1: trail of some Yeah, depending on how residual pattern as
Speaker 1: much as the roadrunner does with a little cloud of
Speaker 1: dust when it takes off. Well, if you're if you're moving,
Speaker 1: if you're moving steadily through the environment, you're probably not
Speaker 1: leaving much of a trail. But if you have been
Speaker 1: staying in a position and then start moving, then it
Speaker 1: wouldn't be so quick as to you wouldn't see like
Speaker 1: a clearly human defined red shape, uh move from uh
Speaker 1: from a position that had been standing in for like
Speaker 1: twenty minutes and then move across the room. It wouldn't
Speaker 1: you know, it wouldn't be in an immediate effect. You
Speaker 1: would still be able to see at least the residual
Speaker 1: heat that was left behind. Now it might be enough
Speaker 1: so that you can clearly tell which one is the
Speaker 1: human and which one's just the space that the human
Speaker 1: was in, but it's not gonna be you know, just
Speaker 1: totally clear cut. Um. So I'm sorry. I was just
Speaker 1: gonna say. So if you're if you're looking at a
Speaker 1: show and they're showing a colored image of you know,
Speaker 1: night vision, basically that's thermal imaging. And if you're looking
Speaker 1: at the monochromatic green screen version, that would be the image.
Speaker 1: So you know now which one is which? Right, So
Speaker 1: let's why are you able to see the heat? That's
Speaker 1: the question. Well, let me let me talk about some
Speaker 1: atoms here. Now you've probably heard us talk about how
Speaker 1: atoms are uh normally they're moving. It's really only if
Speaker 1: you're at zero kelvin when you have no molecular movement,
Speaker 1: when you have no movement on the atomic scale, absolutely,
Speaker 1: thank you, absolute zero. Yes, uh, Because atoms are always moving,
Speaker 1: even in in solid material like a block of marble.
Speaker 1: The atoms within that block of marble are moving. They're
Speaker 1: not moving necessarily at the same speed as say, uh,
Speaker 1: oxygen gas is moving, but they are moving. And atoms
Speaker 1: have a specific state, an energy state that they are
Speaker 1: naturally found in the ground state. No, no, not that
Speaker 1: kind of state. The ground state is what we call it.
Speaker 1: That's the ground state energy level. That's the amount of
Speaker 1: energy and atom has normally if no other outside forces
Speaker 1: or energies are acting upon it. So you've got the
Speaker 1: ground state energy level. That's when all the electrons are
Speaker 1: at their normal electron shell distances from the nucleus of
Speaker 1: the atom. When you add energy to an atom, then
Speaker 1: you excite the electrons until they start to have so
Speaker 1: much energy that they'll pop into outer electron shells further
Speaker 1: out from the nucleus, and the more energy you pour in,
Speaker 1: the further out they get. Okay, so when you remove
Speaker 1: that energy, when that energy is when the electrons get
Speaker 1: to a point where the energy is is decreased enough
Speaker 1: so that the electrons are going to go back toward
Speaker 1: the nucleus. They have to give off some kind of
Speaker 1: energy for that to happen, all right, So you think
Speaker 1: of it almost like you have a a balloon and
Speaker 1: you over inflate that balloon when you let out the uh,
Speaker 1: the air, than that balloon is gonna deflate some. Right,
Speaker 1: it's gonna come back down to a smaller size, and
Speaker 1: if you keep it open, it's gonna go all the
Speaker 1: way down to flat. Well, the electrons are gonna start
Speaker 1: moving back towards the nucleus. They give off photons when
Speaker 1: they do this, and depending upon the material uh that
Speaker 1: in question, you'll get different different kinds of photons within
Speaker 1: the spectrum of light. So some things are going to
Speaker 1: give off light that is actually visible, especially if you
Speaker 1: pour enough energy into it. That's why Let's say you've
Speaker 1: got a toaster oven, and you got the toaster oven
Speaker 1: going on full blast, and you look in and you
Speaker 1: see the little toaster oven coils have turned red. That's
Speaker 1: actually photons being given off by these atoms. And uh,
Speaker 1: if you were to pour even more energy into it.
Speaker 1: If you were to crank it up a notch, those
Speaker 1: coils might start to glow even brighter and different colors.
Speaker 1: So if they went from red to orange, that would
Speaker 1: mean that you have even more energy that's being given off,
Speaker 1: right that you've you've poured more into it, and it's
Speaker 1: and it's giving off higher energy photons. So, uh, all materials,
Speaker 1: all all things are giving off at least some kind
Speaker 1: of photon energy when they because of the whole idea
Speaker 1: of movement and excitation, and the more it gives off,
Speaker 1: the brighter it's going to be. So that's that's what
Speaker 1: the thermal night vision goggles are detecting when when they're
Speaker 1: going when the lights being pulled through that lens, when
Speaker 1: the lens is directing that light to the the sensors,
Speaker 1: it's detecting the the photons that are given off, the
Speaker 1: thermal infrared photons that are given off by things just
Speaker 1: because of the excitation of atoms. So that's what we're
Speaker 1: actually looking at. That's why you can be in a
Speaker 1: completely isolated room. You could be in a cave deep
Speaker 1: below the Earth's surface where there's there's no ambient light whatsoever,
Speaker 1: and still be able to see based upon the what's
Speaker 1: around you. Now, the less the less stuff gives off heat,
Speaker 1: then the less you're gonna be able to see, the
Speaker 1: less the less excitation is there. So if you're in
Speaker 1: a cave where there's nothing else living in there, it
Speaker 1: may you know, the thermal the thermal goggles may not
Speaker 1: do you any good except to let you see where
Speaker 1: your feet are in relation to the rest of you.
Speaker 1: So that might be more useful to carry, say a flashlight. Yes, yes,
Speaker 1: that might be a good idea. To carry a flashlight
Speaker 1: or a head lamp even better. And um, yeah, so
Speaker 1: that's kind of the basics of night vision. It's pretty
Speaker 1: cool stuff. I don't know, have you ever had an
Speaker 1: opportunity to actually look through any sort of night vision stuff? No,
Speaker 1: not really, I just haven't been exposed to it. Um.
Speaker 1: But you can use it for all kinds of different things.
Speaker 1: Of course, the military applications are obvious. Um. But you
Speaker 1: can use it for uh, you know, photography, Um, for spelunking.
Speaker 1: You know, that was an excellent uh suggestion, you know,
Speaker 1: all kinds of sports and things where you might be
Speaker 1: out hunting, you know, out in the woods. There are
Speaker 1: a lot of cam quarters out there that have it. Now,
Speaker 1: there's also cars that have UH displays that include night
Speaker 1: vision UH a night vision element so that you can
Speaker 1: see better when you're driving a night and and they're
Speaker 1: in fact cars that use different versions of it. There's
Speaker 1: some that use the thermal version where they're really detecting
Speaker 1: the heat of things so that you can get an
Speaker 1: idea if there's something in the road like a person
Speaker 1: or an animal, but those are only gonna show you
Speaker 1: things that are again active really uh. Then there are
Speaker 1: other kinds that use the the the image enhancement style UM.
Speaker 1: And there are even some that use the active image
Speaker 1: enhancement so when you turn on your head lights, you're
Speaker 1: actually beaming not just visible light, but infrared rays as well,
Speaker 1: infrared radiation. So uh, the the system and those cars
Speaker 1: picks up the reflection just like we were talking about
Speaker 1: in the generation zero image enhancement night vision. He uses
Speaker 1: that same principle. Now that of course means that the
Speaker 1: range is limited, just as we were talking about earlier,
Speaker 1: and if it's a foggy night, it doesn't work so
Speaker 1: well because the fog will reflect that the that radiation
Speaker 1: back before it can hit something more substantial, so you'll
Speaker 1: just end up it's just like fog. Right, It's just
Speaker 1: like if you were to put your high beams on
Speaker 1: the fog bank, it's like out there. Yeah. Yeah, And
Speaker 1: and in that case, the night vision might not help
Speaker 1: you out unless you have well, if you have a
Speaker 1: thermal one it it might, but the the the image
Speaker 1: enhancement style not so not so useful in that situation. Yeah.
Speaker 1: I've also read that they're looking into the possibility of
Speaker 1: adding it to some smartphones, which would be interesting. Um.
Speaker 1: I've definitely seen the overlays where it's not it's not
Speaker 1: actual thermal imaging, but it is. Yeah, it's the it's
Speaker 1: just the you know, all it does is all it
Speaker 1: does is simulate thermal imaging so that it overlays all
Speaker 1: these bright hypercolors on top of an image. Still have
Speaker 1: a hypercolor shirt? Do you? Does it work? Not anymore?
Speaker 1: I don't think So that's for another podcast. We'll have
Speaker 1: to do a whole podcast just on hypercolor. I've got
Speaker 1: I've written an article about it. All right, guys, we're
Speaker 1: gonna wrap this up. If you have suggestions for particular
Speaker 1: kinds of technology that you would like us to tackle,
Speaker 1: let us know. You can email us our addresses tex
Speaker 1: stuff at how stuff works dot com, or drop us
Speaker 1: a line on Facebook or Twitter. Are handle there is
Speaker 1: tech Stuff hs W. Chris and I will talk to
Speaker 1: you again really soon. Be sure to check out our
Speaker 1: new video podcast, Stuff from the Future. Join how Stuff
Speaker 1: Work staff as we explore the most promising and perplexing
Speaker 1: possibilities of tomorrow. The house stuff Works. I fine app
Speaker 1: has arrived. Download it today on iTunes, brought to you
Speaker 1: by the reinvented two thousand twelve camera. It's ready. Are
Speaker 1: you