WEBVTT - How do signals get jammed? 0:00:07.800 --> 0:00:11.000 A common trope in science fiction is the strategic move 0:00:11.119 --> 0:00:15.880 of signal jamming, interfering with your enemy's ability to communicate. 0:00:16.440 --> 0:00:19.360 My personal favorite example of this is not from Star 0:00:19.440 --> 0:00:23.640 Wars or from Star Trek, but Space Balls. When their 0:00:23.640 --> 0:00:28.560 communications fail, they realize they've been jammed because literal raspberry 0:00:28.640 --> 0:00:32.840 jam drips across the screen. But is that really how 0:00:32.960 --> 0:00:36.919 jamming technology works or is it more like noise canceling 0:00:36.960 --> 0:00:41.120 headphones or something else. Today we'll dig into the physics 0:00:41.159 --> 0:00:45.279 of signal jamming, including the bleeps, the sweeps, and the creeps. 0:00:46.159 --> 0:00:49.800 Welcome to Daniel and Kelly's Extraordinary Universe. 0:01:02.960 --> 0:01:06.080 Hello, I'm Kelly Winer Smith. I study parasites and space. 0:01:06.800 --> 0:01:09.399 Hi, I'm Daniel. I'm a particle physicist and I'm a 0:01:09.400 --> 0:01:10.840 big fan of jam. 0:01:11.520 --> 0:01:14.160 Oh, but not the kind that we're talking about today. 0:01:14.319 --> 0:01:16.080 Were you in a band or anything in high school? 0:01:16.360 --> 0:01:19.320 Oh? I played the clarinet in a marching band and 0:01:19.400 --> 0:01:22.760 you could totally not hear anything. And I played the 0:01:22.800 --> 0:01:26.640 saxophone in a jazz band, so not a very cool 0:01:26.720 --> 0:01:28.560 kind of band. But yeah, I've been in bands. How 0:01:28.560 --> 0:01:31.800 about you? You were goth as a teenager, so you're 0:01:31.840 --> 0:01:34.640 either listening to or performing music. Yeah, I'm guessing. Yeah. 0:01:34.640 --> 0:01:39.840 I played the electric guitar in some grundrock bands. Pretty awesome. 0:01:40.000 --> 0:01:43.399 And you were recently invited by a listener to be 0:01:43.560 --> 0:01:44.600 on their hip hop track. 0:01:44.800 --> 0:01:48.520 Yeah, we'll see where that goes. They said I needed 0:01:48.600 --> 0:01:51.560 singing experience, so I'm guessing that's going to disqualify because 0:01:51.560 --> 0:01:53.240 singing in the car probably doesn't count. 0:01:53.520 --> 0:01:55.920 I don't know that's experienced showers and cars. 0:01:56.200 --> 0:01:59.200 I guess we'll see, all right. So my question for 0:01:59.280 --> 0:02:02.320 you today is we're talking about like, you know, equipment 0:02:02.400 --> 0:02:04.640 and when it doesn't work, whether it's you know, because 0:02:04.640 --> 0:02:07.960 someone's being malicious or not, that's really frustrating. So what 0:02:08.240 --> 0:02:11.760 piece of equipment in your life has been the most 0:02:11.800 --> 0:02:13.240 frustrating to you? Oh? 0:02:13.280 --> 0:02:16.400 Wow? I think the thing I'm most often frustrated by 0:02:16.440 --> 0:02:18.280 are the things I use most to, like a phone 0:02:18.320 --> 0:02:21.480 or a computer. But in reality, these things are amazing. 0:02:22.040 --> 0:02:24.680 Like I use my computer for hours every single day. 0:02:24.840 --> 0:02:27.640 It's always there, it's almost always works exactly as I 0:02:27.680 --> 0:02:30.560 expect it to, so my frustration there is really unfair. 0:02:31.120 --> 0:02:33.440 I think the frustration that's most fairly targeted is to 0:02:33.480 --> 0:02:37.200 the dishwasher, because like it's got a simple job. It 0:02:37.280 --> 0:02:39.960 does one thing and it just doesn't work a lot 0:02:40.040 --> 0:02:42.520 of the times. You know, like, why can't we just 0:02:42.560 --> 0:02:44.560 invent the dishwasher where you put the dishes in and 0:02:44.600 --> 0:02:45.440 they get washed. 0:02:45.720 --> 0:02:47.760 It does a lot of things though, it like it 0:02:47.919 --> 0:02:50.400 senses how dirty the dishes are, it washes them. It 0:02:50.520 --> 0:02:53.080 dries them also, that's another thing it does. It does 0:02:53.120 --> 0:02:54.480 at least two things. 0:02:54.840 --> 0:02:56.799 Wow, look at you standing up for dishwashers. 0:02:57.120 --> 0:02:59.120 I mean, they are kind of incredible. They save you 0:02:59.160 --> 0:02:59.800 a lot of time. 0:03:00.160 --> 0:03:02.480 When they become AI empowered and take over the world, 0:03:02.520 --> 0:03:04.240 they're going to listen to this podcast and they're going 0:03:04.280 --> 0:03:05.640 to know you're one of them. 0:03:05.760 --> 0:03:07.040 I'm hedge in my bets man. 0:03:10.360 --> 0:03:12.240 Well as a person who's done a lot of home 0:03:12.280 --> 0:03:16.320 improvement projects. Kelly, which piece of equipment in your life 0:03:16.320 --> 0:03:17.600 have you been most frustrated by? 0:03:17.760 --> 0:03:19.920 Oh, you know, I think I love all of my 0:03:20.040 --> 0:03:23.680 power tools equally. I think I think the thing. So 0:03:23.720 --> 0:03:25.560 I had a piece of equipment I worked with that 0:03:25.600 --> 0:03:30.480 gave me really big highs and really big lows. And 0:03:30.520 --> 0:03:33.000 that was the electro fishing boat that I used in 0:03:33.040 --> 0:03:36.000 grad school. So I was doing a largemouth bass survey 0:03:36.480 --> 0:03:38.640 in the Sacramento San Joaquin Delta and we were trying 0:03:38.680 --> 0:03:42.120 to catch largemouth bass. And I loved driving this boat. 0:03:42.160 --> 0:03:44.400 It was so much fun. I loved operating the boat. 0:03:44.600 --> 0:03:47.440 And when nobody was around at like four am, when 0:03:47.440 --> 0:03:49.520 we were putting the boat, you know, like down the 0:03:49.600 --> 0:03:53.680 ramp and into the delta, that was amazing. But at 0:03:53.840 --> 0:03:56.720 busy times of day, when I had to like use 0:03:56.720 --> 0:04:00.000 our giant truck and back the boat down the ramp, 0:04:00.920 --> 0:04:06.080 that was the most frustrating because inevitably, some incredibly well 0:04:06.120 --> 0:04:10.600 meaning guy would see, oh, a woman is trying to 0:04:10.680 --> 0:04:14.000 back the boat down the ramp. And they never were 0:04:14.080 --> 0:04:16.600 helping the guys. It was only when I was trying. 0:04:16.600 --> 0:04:19.080 And again they were trying to be very nice, right, 0:04:19.120 --> 0:04:22.200 and I appreciated their help, but it wasn't really helping 0:04:22.240 --> 0:04:23.880 because I did a great job on my own. But 0:04:23.920 --> 0:04:25.520 when they were trying to tell me, I would get 0:04:25.520 --> 0:04:28.280 really flustered because you know, you turn the you know, 0:04:28.320 --> 0:04:30.880 the wheel in one direction, the bocos in the opposite direction, 0:04:30.920 --> 0:04:32.440 and when somebody is trying to tell you, like go 0:04:32.560 --> 0:04:34.680 that way, it gets more confusing. I was doing flying 0:04:34.760 --> 0:04:37.039 on my own, but whenever somebody would try to help me. 0:04:37.440 --> 0:04:39.760 That's when I would mess it up. I just wanted 0:04:39.760 --> 0:04:42.159 to like leave my window rolled up and be like, no, 0:04:42.320 --> 0:04:44.200 I'm not listening to you, but then that would have 0:04:44.240 --> 0:04:48.279 been rude. And so anyway, that was my most frustrating 0:04:48.400 --> 0:04:51.600 equipment experience was trying to get the boat down the 0:04:51.680 --> 0:04:53.640 ramp when people were around. And again I wasn't mad 0:04:53.680 --> 0:04:55.400 at them. They were trying to help. That was nice. 0:04:55.520 --> 0:04:57.520 And you're not even mad at the equipment, right. 0:04:57.440 --> 0:04:59.320 No, I'm not even mad at the equipment. It was 0:04:59.400 --> 0:05:02.000 just like, it's just a very frustrating experience. Every time 0:05:02.040 --> 0:05:03.760 I'd pull up to the boat ramp, I'd get like 0:05:03.880 --> 0:05:07.000 anxious if there was anybody else there. But that's why 0:05:07.000 --> 0:05:08.840 I really liked being on the crew that would start 0:05:08.839 --> 0:05:10.920 at like four am, because usually there was no one 0:05:10.920 --> 0:05:13.680 else there and I could just whoop in one like 0:05:13.800 --> 0:05:15.960 fell swoop, get it down and then we'd be in 0:05:16.080 --> 0:05:20.080 the water and we'd go out when collect our fish. 0:05:20.120 --> 0:05:22.200 Well, we aren't all out on the water at four 0:05:22.200 --> 0:05:25.200 am to collect fish. But almost everybody lives a life 0:05:25.240 --> 0:05:29.559 that's dominated by machines electronic devices that enable your life 0:05:29.560 --> 0:05:33.120 and make it easier or more complicated or just more fun. 0:05:33.480 --> 0:05:36.359 And sometimes they don't work just because they're busted or 0:05:36.520 --> 0:05:40.239 it's user error, but sometimes it's malicious. That's right, somebody 0:05:40.279 --> 0:05:43.560 out there is interfering with your use of your devices. 0:05:43.960 --> 0:05:45.640 And today we're going to talk about one of those 0:05:45.720 --> 0:05:49.800 modes of interference, signal jamming, which appears all over the 0:05:49.800 --> 0:05:52.320 place in popular media and science fiction. And a bunch 0:05:52.320 --> 0:05:54.160 of people wrote in and said, hey, can you explain 0:05:54.320 --> 0:05:56.080 what is signal jamming? 0:05:56.520 --> 0:05:59.159 And I'm glad that they did because I love hearing 0:05:59.160 --> 0:06:02.200 stuff like this explo by Daniel. You'll get the clearest 0:06:02.240 --> 0:06:05.640 explanation when Daniel's the one explaining it. But let's go 0:06:05.720 --> 0:06:08.560 ahead and ask our extraordinaries, you know, the ones who 0:06:08.560 --> 0:06:11.520 didn't write in to ask for a better explanation. How 0:06:11.560 --> 0:06:14.720 does a signal jammer work? And here's what they had 0:06:14.720 --> 0:06:15.040 to say. 0:06:15.680 --> 0:06:21.000 You have a wave that's getting canceled out by another wave. 0:06:21.400 --> 0:06:25.039 They probably emit electromagnetic waves. It's just the right frequency 0:06:25.120 --> 0:06:27.599 to be perfectly deconstructive to other waves. 0:06:27.360 --> 0:06:32.840 By inserting destructive interference essentially the inverse waves of any 0:06:32.920 --> 0:06:37.719 intended communication, thus making it be unintelligible. Kind of how 0:06:37.920 --> 0:06:42.839 noise canceling headphones insert anti noise to negate out any 0:06:43.120 --> 0:06:48.239 undesirable outside noise. I have no idea how signal jamma works. 0:06:48.920 --> 0:06:53.240 My best guess would be that it uses photons in some. 0:06:53.080 --> 0:06:59.279 Way scrambling the radio waves. I don't know, some sort 0:06:59.320 --> 0:07:02.560 of powder way disrupting the others, but it needs to 0:07:02.560 --> 0:07:04.760 be a superior powderway. Can you hit a particle way 0:07:05.279 --> 0:07:06.640 with another particle. 0:07:06.240 --> 0:07:10.440 Way by sending a bunch of random data of the 0:07:10.480 --> 0:07:13.240 same signal type that screws up the receiver so it 0:07:13.240 --> 0:07:15.160 doesn't know what data is real and what's stake. 0:07:15.840 --> 0:07:19.320 All right. I love the idea of superior particles that 0:07:19.400 --> 0:07:21.440 you can like zap one kind of particle another kind 0:07:21.440 --> 0:07:23.720 of particle and it'll be dominated nice. 0:07:24.040 --> 0:07:26.120 Yes, that is pretty epic. 0:07:26.360 --> 0:07:28.800 The way you say nice reminds me that this weekend 0:07:28.840 --> 0:07:30.840 I was hanging out with a two year old and 0:07:30.920 --> 0:07:33.520 she's in this phase of just like picking up words, 0:07:34.320 --> 0:07:38.040 and something happened she like dropped a marble right under 0:07:38.040 --> 0:07:40.880 her mom's eye, and I said nice. And then every 0:07:40.960 --> 0:07:46.480 time she did something mischievous the whole evening, she went nice, 0:07:47.920 --> 0:07:51.320 and I laughed my head off. Anyway, these are very 0:07:51.520 --> 0:07:54.840 nice responses and the theme that emerges for me is 0:07:54.840 --> 0:07:58.000 that a lot of people think it's destructive interference. They 0:07:58.000 --> 0:08:00.880 think it's this fancy wave canceling stuff, like the thing 0:08:00.920 --> 0:08:04.520 happening with your noise cancelation headphones. So I think it's 0:08:04.560 --> 0:08:07.280 great that we're going to dig into the actual mechanics 0:08:07.280 --> 0:08:10.520 of how signal jamming works, because hint, hint, it's not 0:08:11.000 --> 0:08:12.120 destructive interference. 0:08:12.320 --> 0:08:15.440 What all right, So how our message is actually sent? 0:08:15.920 --> 0:08:18.160 Yeah, So to understand how signals are jammed, we have 0:08:18.160 --> 0:08:22.520 to understand the physics of signals. And for this conversation, 0:08:22.560 --> 0:08:25.400 we're going to ignore quantum mechanics because you mostly can. 0:08:25.920 --> 0:08:28.400 And as a reminder, you know, anytime we do physics, 0:08:28.400 --> 0:08:31.960 we're always using a simplified description of the universe. We 0:08:32.000 --> 0:08:34.120 can't bring all of our knowledge to bear all at 0:08:34.160 --> 0:08:36.040 once because tomorrow and we don't need to and number 0:08:36.040 --> 0:08:38.480 two then we'd get nothing done ever, because we'd be 0:08:38.520 --> 0:08:42.360 solving Einstein's equations in impossible ways. So we're always just 0:08:42.400 --> 0:08:46.040 like choosing what aspects of physics to use and neglecting 0:08:46.120 --> 0:08:48.680 some little bits. And for this conversation, we can treat 0:08:48.720 --> 0:08:52.400 this like classical and electromagnetism. So we have electric fields 0:08:52.400 --> 0:08:55.480 and magnetic fields and oscillations within them, and we can 0:08:55.520 --> 0:08:58.280 ignore like quantum pulses and fussiness and all that kind 0:08:58.280 --> 0:08:58.720 of stuff. 0:08:59.080 --> 0:09:01.400 Okay, okay, well, you know, and we only have an hour. 0:09:03.880 --> 0:09:05.959 And when we talk about messages, are we talking about 0:09:06.000 --> 0:09:11.079 like radio messages cell phone messages or are those all 0:09:11.160 --> 0:09:12.080 kind of the same thing. 0:09:12.320 --> 0:09:14.680 Those are all kind of the same thing. Everything here 0:09:15.040 --> 0:09:18.640 is a signal that's transmitted wirelessly, which means it's a 0:09:18.720 --> 0:09:22.040 pulse in the electromagnetic field, right, And so we're going 0:09:22.120 --> 0:09:26.040 to talk about messages encoded as pulses in the electromagnetic field, 0:09:26.240 --> 0:09:30.280 which basically means you're sending light invisible light or visible 0:09:30.360 --> 0:09:33.720 light of various frequencies. Right. And so when you listen 0:09:33.720 --> 0:09:37.080 to your radio, for example, you're getting radio waves. Radio 0:09:37.120 --> 0:09:40.880 waves are oscillations in the electromagnetic field that are picked 0:09:40.920 --> 0:09:43.360 up by your radio. When you listen to your cell phone, 0:09:43.679 --> 0:09:47.520 you're getting cellular information that's oscillations of the electromagnetic field, 0:09:47.559 --> 0:09:50.240 just at a different frequency. When you used to watch 0:09:50.280 --> 0:09:53.959 TV with antennas, you are picking up signals over the air, 0:09:54.240 --> 0:09:57.880 which are just oscillations in the electromagnetic field. When you 0:09:57.920 --> 0:09:59.960 tap your credit card on something to pay for it. 0:10:00.160 --> 0:10:03.280 There's a little bit of electromagnetic information being passed back 0:10:03.320 --> 0:10:07.080 and forth. So all of these things are electromagnetic, right, 0:10:07.120 --> 0:10:10.640 So all these messages are electromagnetic. They're just oscillations in 0:10:10.679 --> 0:10:13.360 the electromagnetic field, okay, And the way that you send 0:10:13.360 --> 0:10:15.480 them is an antenna. Right, So let's think about what 0:10:15.559 --> 0:10:17.760 is the physics of an antenna. It's like a long 0:10:17.800 --> 0:10:21.679 cylinder of metal. It's got a bunch of electrons in there, right, 0:10:21.720 --> 0:10:24.160 and you apply some current the electrons to move one 0:10:24.200 --> 0:10:26.800 way and the electrons to move the other way. Now, 0:10:26.800 --> 0:10:30.240 electrons have an electric charge, right, and so they make 0:10:30.320 --> 0:10:33.160 an electric field. So if an antenna is just sitting there, 0:10:33.200 --> 0:10:35.800 it has an electric field. And if you pull on 0:10:35.840 --> 0:10:39.480 the electrons to move them, the electric field changes because 0:10:39.520 --> 0:10:43.600 you're moving the electrons. The electric field moves with the electrons. Right. 0:10:43.679 --> 0:10:47.440 That makes sense. So if you have one electron, for example, 0:10:47.600 --> 0:10:50.640 and you wiggle it, what happens, Well, instead of having 0:10:50.679 --> 0:10:53.440 the same electric field through time, Now that electric field 0:10:53.520 --> 0:10:56.959 is changing. I move the electron, electric field moves with it. Right. 0:10:57.800 --> 0:11:01.520 All cool? But if I move my electron here in California, 0:11:01.679 --> 0:11:05.640 can Kelly tell immediately that I've moved my electron. No, 0:11:06.400 --> 0:11:09.199 she can only tell when the new electric field gets 0:11:09.240 --> 0:11:12.120 to her, so there's a time delay. If I wiggle 0:11:12.160 --> 0:11:15.040 my electron up and down, then I create a wiggling 0:11:15.120 --> 0:11:18.280 electric field through time that eventually gets to Kelly and 0:11:18.320 --> 0:11:21.199 she can pick it up with her electric field measuring device. 0:11:21.600 --> 0:11:22.400 Does that make sense? 0:11:22.600 --> 0:11:26.079 That does? Okay, It's kind of amazing that wiggling electric 0:11:26.160 --> 0:11:29.720 fields can give you like music and complicated. 0:11:29.200 --> 0:11:32.920 I know, crazy, yeah, And so all of this information 0:11:33.280 --> 0:11:37.600 is just encoded in wiggling electric fields, which create magnetic fields. 0:11:37.640 --> 0:11:40.640 And that's what light is, right. Light is a coupled 0:11:40.640 --> 0:11:44.440 oscillation between electric fields and magnetic fields. They're very tightly linked, 0:11:44.640 --> 0:11:48.280 and changing electric fields make magnetic fields, changing magnetic fields 0:11:48.320 --> 0:11:51.640 make electric fields. So it's this incredible physical phenomena that 0:11:51.679 --> 0:11:55.720 you can send information through the universe if they're in 0:11:55.760 --> 0:11:58.840 these fields. And as you say, it's really cool that 0:11:58.960 --> 0:12:01.960 you can use those wiggles to represent almost any kind 0:12:02.000 --> 0:12:05.320 of information. Right. You can like encode my voice, you 0:12:05.360 --> 0:12:08.720 can send data. You know, you can send anything essentially 0:12:08.760 --> 0:12:10.720 if you just come up with some way to encode it. 0:12:11.000 --> 0:12:13.400 You say, this kind of wiggle means that this other 0:12:13.440 --> 0:12:15.400 kind of wiggle means something else, and then you can 0:12:15.480 --> 0:12:18.760 use that to transmit information. And so the basic physical 0:12:18.840 --> 0:12:21.960 setup is you have an antenna where you are controlling 0:12:22.160 --> 0:12:25.000 the electrons, which means you control the wiggles and somebody 0:12:25.040 --> 0:12:28.160 else the receiver. Kelly has an antenna, and when the 0:12:28.200 --> 0:12:31.400 electric field arrives at Kelly, how does she know that 0:12:31.440 --> 0:12:34.640 it's changed. Well, her antenna's electrons get wiggled by the 0:12:34.720 --> 0:12:38.200 electric field for the same reason that wiggling my electrons 0:12:38.240 --> 0:12:41.640 makes a wiggling electric field. That wiggling electric field when 0:12:41.679 --> 0:12:45.400 it arrives at Kelly's antenna, it wiggles her electrons. Then 0:12:45.440 --> 0:12:48.920 she has electronics to pick up those wiggles as current 0:12:48.960 --> 0:12:51.920 and that's her signal. So effectively, I send a signal 0:12:51.960 --> 0:12:55.760 in my electronics to a signal in Kelly's electronics. That's 0:12:55.800 --> 0:12:57.560 how message transmission works. 0:12:57.760 --> 0:13:02.480 Okay, And this works because like so, these messages need 0:13:02.520 --> 0:13:06.600 to pass through like buildings and forests and stuff like that. 0:13:07.400 --> 0:13:10.200 And does some of it get lost as it passes 0:13:10.320 --> 0:13:13.680 through that? Or no, because electrons and their fields just 0:13:13.760 --> 0:13:14.679 go through stuff. 0:13:14.840 --> 0:13:19.800 Or do yeah, yeah, great question. The answer is yes 0:13:19.920 --> 0:13:23.080 and no. It depends on the frequency So for example, 0:13:23.120 --> 0:13:25.840 if you're doing radio, then your frequencies are like kill 0:13:25.840 --> 0:13:28.400 a hertz or megahertz. Right, when you're listening to like 0:13:28.760 --> 0:13:31.440 rock one o seven point nine, one oh seven point 0:13:31.520 --> 0:13:34.240 nine means one hundred and seven point nine megaherts is 0:13:34.280 --> 0:13:38.040 the frequency of that signal. When you're using Wi Fi, 0:13:38.240 --> 0:13:41.040 then it's like two point four or five gigahertz, right, 0:13:41.160 --> 0:13:43.280 those are hurts. Those are frequencies. It tells you how 0:13:43.280 --> 0:13:46.520 many times the signal oscillates per second. Five gigaherts is 0:13:46.800 --> 0:13:49.560 five billion oscillations per second. 0:13:49.880 --> 0:13:50.160 Wow. 0:13:50.200 --> 0:13:53.959 Cell phones use like six hundred megaherts to like fifty gigaherts. 0:13:54.360 --> 0:13:57.160 So each one has a different frequency range and different 0:13:57.200 --> 0:14:00.000 frequencies behave differently just the same with it, like different 0:14:00.080 --> 0:14:03.600 frequencies of light are either visible or invisible, and different 0:14:03.640 --> 0:14:07.319 stuff is transparent or opaque. Like X rays pass right 0:14:07.360 --> 0:14:10.240 through your soft muscle tissue, but they don't pass through 0:14:10.240 --> 0:14:14.680 bone and light visible light doesn't pass through soft muscle tissue, right, 0:14:15.160 --> 0:14:19.200 So different things are transparent to different frequencies. In general, 0:14:19.800 --> 0:14:23.200 shorter frequency stuff like cell phones and Wi Fi has 0:14:23.200 --> 0:14:28.040 shorter ranges than longer frequency stuff like radio. There's less 0:14:28.080 --> 0:14:31.720 atmospheric absorption. Like the atmosphere is more transparent to radio 0:14:32.080 --> 0:14:33.960 than it is to Wi Fi and cell towers, so 0:14:34.040 --> 0:14:37.840 it doesn't fizzle out as much, and radio is less 0:14:37.880 --> 0:14:41.400 sensitive to like small obstacles. Radio can also bounce off 0:14:41.400 --> 0:14:45.160 the atmosphere sometimes depending on the frequency, and so it's 0:14:45.200 --> 0:14:48.400 easier to pick up radio for miles and miles away 0:14:48.960 --> 0:14:51.120 or you know, like ham radio operators can talk to 0:14:51.120 --> 0:14:54.520 people from around the world using those frequencies, whereas you 0:14:54.520 --> 0:14:56.560 can never do that with like cell phone towers. But 0:14:56.640 --> 0:14:59.520 cell phone towers are designed to only cover like the 0:14:59.600 --> 0:15:01.920 region that you're in. You don't want to hear from 0:15:01.920 --> 0:15:03.040 other cell phone towers. 0:15:03.240 --> 0:15:05.760 Okay, I feel like I remember when we had a 0:15:05.760 --> 0:15:11.320 conversation about space based solar we were talking about frequencies, 0:15:11.360 --> 0:15:13.120 like what frequency would you pick so that you could 0:15:13.120 --> 0:15:15.280 get your message down to Earth so it wasn't getting 0:15:15.440 --> 0:15:17.720 caught in the clouds and stuff like that. And this 0:15:17.800 --> 0:15:20.120 is a similar, yeah, exactly idea. 0:15:19.880 --> 0:15:22.400 Right exactly, And the greenhouse effect is of an effect 0:15:22.440 --> 0:15:25.840 just for this reason that like light passes mostly through 0:15:25.840 --> 0:15:29.160 the atmosphere, but then the Earth absorbs it changes a frequency, 0:15:29.200 --> 0:15:33.640 glows at a lower frequency to which greenhouse gases are opaque, right, 0:15:33.680 --> 0:15:35.320 And so that's why the light can pass in but 0:15:35.400 --> 0:15:38.600 not out because the greenhouse gases are transparent to the 0:15:38.680 --> 0:15:41.240 light coming in and opaque to the light coming out. Right, 0:15:41.280 --> 0:15:44.080 So like the same gases are opaque or transparent to 0:15:44.160 --> 0:15:48.680 different frequencies. Another major issue for interfering is metals. Right, 0:15:48.720 --> 0:15:52.000 any kind of conductor, just like your antenna is going 0:15:52.040 --> 0:15:54.160 to receive the message, it's going to wiggle the electrons 0:15:54.160 --> 0:15:57.400 in your antenna. If you're inside a metal cage with 0:15:57.520 --> 0:15:59.840 your antenna, you're not going to get the signal because 0:15:59.880 --> 0:16:02.720 the metal cage is gonna wiggle its electrons, and it 0:16:02.760 --> 0:16:05.160 wiggles and its electrons in exactly the way to counter 0:16:05.440 --> 0:16:08.520 that field. That's what an antenna does. So the metal 0:16:08.560 --> 0:16:11.320 cage basically eats the signal. And that's why in an 0:16:11.360 --> 0:16:14.480 elevator or anything we call a Faraday cage just a 0:16:14.520 --> 0:16:18.600 metal box, you basically can't get electromagnetic signals or send them. 0:16:19.000 --> 0:16:21.040 This is why people put tinfoil hats on their head. 0:16:21.080 --> 0:16:23.160 There's like actual physical basis. 0:16:24.320 --> 0:16:28.800 That's great. Okay, wow, I never knew they were so smart. 0:16:30.280 --> 0:16:32.720 I'm not saying the CA is trying to control you, 0:16:33.000 --> 0:16:35.720 but if they were a tinfoil hat really would protect you. 0:16:35.800 --> 0:16:39.080 Wow, okay, great, maybe I'm gonna start lining my winter 0:16:39.200 --> 0:16:45.400 hats with tinfoil just in case. Amazing. All right, we're 0:16:45.400 --> 0:16:48.360 gonna take a break, so run to your kitchens, grab 0:16:48.440 --> 0:17:11.560 some tinfoil, and we'll be right back. And we're back 0:17:11.600 --> 0:17:14.440 to Daniel and Kelly's Extraordinary Universe. So we were talking 0:17:14.440 --> 0:17:18.840 about how the frequency of waves can determine what things 0:17:18.920 --> 0:17:21.080 might like get in the way of the signal. Are 0:17:21.119 --> 0:17:23.360 there other things that can like get in the way 0:17:23.560 --> 0:17:26.359 or generate noise or basically mess up the signal in 0:17:26.400 --> 0:17:26.760 some way? 0:17:27.200 --> 0:17:30.119 Yeah, noise is a big issue because your intent is 0:17:30.119 --> 0:17:33.720 not the only thing broadcasting, Like, the universe is variously 0:17:33.800 --> 0:17:38.560 loud at various frequencies because there's other stuff generating electromagnetic radiation, 0:17:39.320 --> 0:17:41.560 and so you want to pick a channel where the 0:17:41.640 --> 0:17:44.800 universe tends to be quieter. Like one of the reasons 0:17:44.840 --> 0:17:49.440 that astronomers look for messages from aliens at one particular 0:17:49.520 --> 0:17:52.320 frequency they call it the watering hole, is because that's 0:17:52.359 --> 0:17:54.080 the one where the universe is pretty quiet, And so 0:17:54.080 --> 0:17:56.200 if you were going to broadcast, that's a good place 0:17:56.200 --> 0:17:58.800 to do it. And so your goal is you want 0:17:58.840 --> 0:18:02.160 to send a message from Californative Virginia, is to either 0:18:02.280 --> 0:18:05.159 find a quiet band where nobody else is broadcasting, or 0:18:05.200 --> 0:18:08.240 to be louder than the noise so that the antenna 0:18:08.280 --> 0:18:16.920 can pick it up above the noise. That's crucial. Nice, 0:18:17.560 --> 0:18:19.400 I can always count on you for two year old humor. 0:18:19.440 --> 0:18:19.680 Thank you. 0:18:20.040 --> 0:18:22.320 Yeah, that's right, that's that's the level I've risen to. 0:18:23.600 --> 0:18:25.639 Nice. Think a two year old say that? 0:18:25.720 --> 0:18:26.400 Oh boy. 0:18:26.720 --> 0:18:29.680 Anyway, So the idea of a signal jammer is actually 0:18:29.760 --> 0:18:33.720 quite simple. It's make a bunch of noise, makes so 0:18:33.840 --> 0:18:36.080 much noise that the person who's trying to receive the 0:18:36.119 --> 0:18:39.280 signal can't hear it over the noise. It's like if 0:18:39.320 --> 0:18:41.000 your sibling is trying to spoil the end of a 0:18:41.040 --> 0:18:44.520 movie and you go l L L. You can't hear them. 0:18:44.640 --> 0:18:47.760 You are jamming their signal. You can't hear their signal 0:18:47.800 --> 0:18:50.320 over the noise that you are making, in this case, 0:18:50.359 --> 0:18:53.080 probably trying to prevent somebody else from getting a signal. 0:18:53.560 --> 0:18:55.720 So you just make a bunch of noise at the 0:18:55.800 --> 0:18:58.600 same frequency where they're trying to hear it, and maybe 0:18:58.600 --> 0:19:02.199 you're closer to the than the original sender is, so 0:19:02.240 --> 0:19:04.199 you can create a bunch of loud noise to make 0:19:04.240 --> 0:19:05.360 it hard for them to hear. 0:19:05.800 --> 0:19:07.359 Okay, so you need to make sure that it's the 0:19:07.440 --> 0:19:12.040 same wavelength so that it's it's not interfering, it's just 0:19:12.720 --> 0:19:15.720 overlapping and making noise exactly. 0:19:15.760 --> 0:19:17.600 And let's pull those two things apart, because a lot 0:19:17.600 --> 0:19:21.440 of the listeners suggested that signal jamming could use destructive interference. 0:19:22.040 --> 0:19:23.760 So let's dig into that for a minute and remind 0:19:23.760 --> 0:19:27.600 ourselves what is destructive interference? While we're thinking about electromagnetic 0:19:27.680 --> 0:19:31.320 signals as waves, waves are complicated and they can interfere. Right, 0:19:31.320 --> 0:19:33.440 you have the double slit experiment. You have also some 0:19:33.520 --> 0:19:36.800 weird optical effects you have like in your living room 0:19:36.800 --> 0:19:39.000 when you're listening to the TV, there's like spots where 0:19:39.040 --> 0:19:42.080 it's louder and quieter at the same distance from the TV. 0:19:42.240 --> 0:19:45.399 What is going on? Remember that waves can add and 0:19:45.440 --> 0:19:48.800 they can subtract. So waves go up and down. Right, 0:19:49.000 --> 0:19:52.000 if you slap on the surface of your bathtub, you 0:19:52.040 --> 0:19:53.879 make waves that are up and down in the surface 0:19:53.920 --> 0:19:56.000 of the water. If you slap with the other hand, 0:19:56.400 --> 0:19:59.080 then those waves overlap with each other. And if one 0:19:59.119 --> 0:20:01.200 wave is going down the same time the other waves 0:20:01.280 --> 0:20:04.439 going up. Then they cancel out. Up plus down equals nothing. 0:20:04.880 --> 0:20:07.439 So this is a destructive interference. It's not like you 0:20:07.480 --> 0:20:09.479 have two waves that are in the same place at 0:20:09.480 --> 0:20:11.120 the same time and you can detect both of them. 0:20:11.200 --> 0:20:14.000 They literally add up to zero, and so they cancel 0:20:14.040 --> 0:20:16.080 each other out. That's destructive interference. 0:20:16.720 --> 0:20:18.600 I miss being a kid. I can't remember the last 0:20:18.640 --> 0:20:20.680 time I took a bath. That was like a thing 0:20:20.760 --> 0:20:24.240 I did when I was eight, But it sounds like 0:20:24.280 --> 0:20:26.119 fun to smack on the surface of a bath and 0:20:26.160 --> 0:20:26.879 play with the waves. 0:20:27.040 --> 0:20:30.080 It's fun. You're doing physics experiments, that's right, But this 0:20:30.119 --> 0:20:31.919 is hard to do. In order for this to happen, 0:20:32.280 --> 0:20:34.720 you have to have two waves that are exactly the 0:20:34.760 --> 0:20:38.920 same height and the same frequency and out of phase 0:20:38.960 --> 0:20:41.320 by one hundred and eighty degrees, which means that like 0:20:41.359 --> 0:20:43.200 one of them is shifted so that it's going down 0:20:43.320 --> 0:20:47.600 when the other one is going up. Otherwise they'll constructively interfere. Right, 0:20:47.600 --> 0:20:49.440 two waves that are both going up at the same 0:20:49.480 --> 0:20:53.080 time will add up to a double wave. Right, And 0:20:53.160 --> 0:20:56.400 so this is hard to arrange. And it's amazing that 0:20:56.440 --> 0:20:59.200 like your noise canceling headphones can do this. What they 0:20:59.240 --> 0:21:01.199 do is they have a little microphone inside them, so 0:21:01.200 --> 0:21:03.680 they detect the sound that's about to hit your ear, 0:21:04.160 --> 0:21:07.679