WEBVTT - TechStuff Classic: TechStuff Looks at Radio Telescopes 0:00:04.120 --> 0:00:07.160 Get in touch with technology with tech Stuff from how 0:00:07.200 --> 0:00:14.160 stuff works dot com. Hey there, and welcome to tech Stuff. 0:00:14.200 --> 0:00:18.080 I am your host executive producer, John than Strick, London. 0:00:18.160 --> 0:00:21.360 I love all things tech. It is time for another 0:00:21.480 --> 0:00:24.319 classic episode of tech Stuff, and today we're going to 0:00:24.480 --> 0:00:28.760 visit an episode that we originally published on January two 0:00:28.800 --> 0:00:31.680 thousand twelve. Chris Pallette my co host at the time, 0:00:31.720 --> 0:00:35.560 and I decided to look into the topic of radio telescopes. 0:00:35.960 --> 0:00:38.000 I talked about these not too long ago when I 0:00:38.040 --> 0:00:41.920 did a series about DARPA. Well, now we're gonna have 0:00:42.040 --> 0:00:44.960 a full episode dedicated to the topic, and I hope 0:00:45.000 --> 0:00:48.640 you guys enjoy. So. Um, before we get started, we're 0:00:48.640 --> 0:00:51.360 gonna do something we haven't done a little while. Yeah, 0:00:51.520 --> 0:00:59.160 we're gonna listen to a little listener mail. This listener 0:00:59.200 --> 0:01:02.160 mail comes from me who says I love your podcast 0:01:02.160 --> 0:01:05.280 and have enjoyed listening to your incifle and quirky explanations immensely. 0:01:05.520 --> 0:01:07.480 I tried to search through the past podcast to see 0:01:07.480 --> 0:01:09.840 if you have done one on radio telescopes, to no avail, 0:01:10.120 --> 0:01:12.160 So I hope I didn't just miss it. It seems 0:01:12.160 --> 0:01:14.440 to me that radio telescopes are being used frequently to 0:01:14.520 --> 0:01:16.800 learn about this and study the far reaches of the 0:01:16.840 --> 0:01:19.840 galaxy and beyond. And that's pretty darn cool, so it'd 0:01:19.840 --> 0:01:21.919 be neat to learn more about how they work. Thanks 0:01:21.959 --> 0:01:24.760 and thanks for the show, Minka. Well you're welcome, Inga. 0:01:25.640 --> 0:01:27.120 I just wanted to say you're welcome. All right, So 0:01:27.120 --> 0:01:31.480 now we're moving on to our topic, the Smurfs. No, no, 0:01:31.480 --> 0:01:35.760 we're gonna talk about radio telescopes. Good, yeah, we sort of. Well, 0:01:36.040 --> 0:01:38.959 we've talked about things that relate to radio telescopes like 0:01:39.160 --> 0:01:44.000 radio and stead yes, and steady set, which does very 0:01:44.080 --> 0:01:48.760 much relate to radio telescopes. Well, what do radio telescopes do? 0:01:48.840 --> 0:01:51.920 Why are they important? Well, it's funny that you should 0:01:51.920 --> 0:01:56.120 mention that, Yeah, because they're I my notes crashed, so 0:01:56.120 --> 0:01:58.040 I don't know what I'm talking about. Your notes crash. No, 0:01:58.120 --> 0:02:00.840 I'm not. I'm just kidding. They're still up. He can't 0:02:00.840 --> 0:02:03.080 see my computer from where he sits. Yes, because he's 0:02:03.080 --> 0:02:05.600 sitting directly across from me. Yes. See. If if you 0:02:05.720 --> 0:02:08.080 ever wondered if that was true or not, it is. Yeah, 0:02:08.320 --> 0:02:12.760 um no, it's it's actually using it's unlike a typical 0:02:12.919 --> 0:02:17.360 visual telescope, which uses lenses and your eyeball, and you 0:02:17.360 --> 0:02:20.160 look through it and you look for stuff on the 0:02:20.160 --> 0:02:22.600 other side and base it directs light which is in 0:02:22.680 --> 0:02:26.280 the visible spectrum of the electromagnetic frequency. Yes, to our 0:02:26.639 --> 0:02:31.160 to our eyeballs ultimately right right, But and again another 0:02:31.240 --> 0:02:34.639 drastic oversimplification of the parts. But a radio telescope is 0:02:34.639 --> 0:02:39.320 actually monitoring different parts of the electromagnetic frequency. Yeah. Yeah, 0:02:39.360 --> 0:02:42.200 it's good looking at a completely different spectrum. So this 0:02:42.280 --> 0:02:44.520 is part of the spectrum that is not visible to 0:02:44.560 --> 0:02:48.400 the naked eye. So we are using these telescopes to 0:02:48.520 --> 0:02:54.280 measure um radio frequency variations that come from outer space. 0:02:54.480 --> 0:02:56.640 And it turns out that lots of stuff out there 0:02:57.000 --> 0:03:04.600 generates radio frequencies, right, So things like quasars, pulsars, galaxies, uh, 0:03:04.880 --> 0:03:09.520 distant stars, these sort of things can generate electro magnetic 0:03:10.040 --> 0:03:14.880 radiation and in the form of radio frequencies. And sometimes 0:03:14.919 --> 0:03:19.880 these are are objects that we can't detect visually, but 0:03:19.960 --> 0:03:22.639 we can detect them if we have a sensitive enough 0:03:23.919 --> 0:03:30.480 tool that can can detect and measure radio frequencies. So 0:03:30.560 --> 0:03:33.560 that's really what a radio telescope is all about. And 0:03:33.600 --> 0:03:36.920 it's kind of tricky picking up radio frequencies from outer 0:03:37.000 --> 0:03:42.200 space because only certain the actual band of frequencies or 0:03:42.240 --> 0:03:45.760 wavelengths I should say, the band of wavelengths that exist 0:03:45.840 --> 0:03:50.120 within the electromatic spect magnetic spectrum that are radio frequency waves. 0:03:50.840 --> 0:03:55.720 It's pretty broad. Yeah, about ten meters and to one millimeter. 0:03:56.160 --> 0:03:59.080 That's a pretty good size. Yeah, you can actually get 0:03:59.200 --> 0:04:01.240 radio waves that are even longer than that, like the 0:04:01.280 --> 0:04:04.520 size of football fields. But here's the thing is that 0:04:04.960 --> 0:04:09.800 the Earth has a level of the atmosphere called the ionosphere. Now, 0:04:09.840 --> 0:04:13.080 the iono sphere is uh, it's kind of funky. So 0:04:13.640 --> 0:04:16.240 you guys probably have heard us talk about ions before, 0:04:16.680 --> 0:04:20.240 you know. That's when we're talking about uh, atoms that 0:04:20.279 --> 0:04:23.320 have either gained or lost an electron. And if you 0:04:23.360 --> 0:04:26.119 ionize something, that means you've got some free electrons roaming 0:04:26.160 --> 0:04:28.400 around in it. So like an ionized gas or a 0:04:28.400 --> 0:04:32.599 plasma can actually hold carry an electric charge. Right, Yes, 0:04:33.279 --> 0:04:37.560 Why are you smiling at me just because I saw 0:04:37.600 --> 0:04:41.159 a whole bunch of people going WHOA free electrons? Yeah? Sorr, 0:04:41.520 --> 0:04:44.080 there're so expensive. Otherwise that's true. Have you seen my 0:04:44.120 --> 0:04:47.680 electric bill? Anyway? So you have the ionosphere, whether these 0:04:47.680 --> 0:04:50.520 free roaming electrons out there, and uh, and it kind 0:04:50.520 --> 0:04:55.720 of acts as a bit of a shield or reflector 0:04:55.760 --> 0:04:59.440 in in some ways, and so radio waves of a 0:04:59.480 --> 0:05:03.520 certain way wave length cannot pass through the ionosphere. Essentially, 0:05:03.560 --> 0:05:06.800 anything that's ten meters are longer, the ionosphere is opaque 0:05:06.880 --> 0:05:10.880 to those. That's why you can actually broadcast certain long 0:05:10.960 --> 0:05:15.680 wavelength radio waves uh and bank them off the ionosphere 0:05:15.920 --> 0:05:19.919 because it won't pass through. Now, when you start getting 0:05:20.240 --> 0:05:24.119 shorter than a ten meter wave length, you have radio 0:05:24.160 --> 0:05:27.200 waves that can pass through the ionosphere. But if it's 0:05:27.279 --> 0:05:30.120 longer than twenty centimeters, which is about one point five 0:05:30.160 --> 0:05:33.440 gig hurts in frequency when you talk about these, If 0:05:33.440 --> 0:05:37.560 it's longer than twenty centimeters, you start to have distortion 0:05:37.800 --> 0:05:41.400 as it passes through the ionosphere. It's called scintillation. And 0:05:41.440 --> 0:05:44.120 this isn't that different from the way when we look 0:05:44.200 --> 0:05:47.200 up into the sky and we see stars twinkling. That's 0:05:47.200 --> 0:05:48.560 sort of the same sort of thing we talked about 0:05:48.560 --> 0:05:51.640 being scintillating, same kind of idea, except in this case, 0:05:51.720 --> 0:05:54.600 you know, that's we're talking about the visual spectrum there, 0:05:55.200 --> 0:05:58.360 but here, Yeah, the twenty centimeters are longer, you run 0:05:58.360 --> 0:06:02.200 into that problem. And so that's not entirely useful for 0:06:02.320 --> 0:06:08.160 measurement purposes. So radio telescopes tend to focus on pun 0:06:08.160 --> 0:06:11.960 intended Uh, wavelengths that are between one centimeter and twenty 0:06:11.960 --> 0:06:16.440 centimeters in length tend to Now there are some variations. 0:06:16.480 --> 0:06:19.040 And also if you were to have a radio telescope, 0:06:19.080 --> 0:06:22.200 say in orbit where it's you know, you don't have 0:06:22.240 --> 0:06:26.640 the ionosphere as a in play. Um, that's a different story. 0:06:26.960 --> 0:06:29.680 But ground based radio telescopes kind of had to play 0:06:29.760 --> 0:06:33.400 within these rules because the way the ionosphere works. One 0:06:33.400 --> 0:06:37.479 of the nice things though about the radio telescope is that, uh, 0:06:37.520 --> 0:06:43.000 those frequencies generally come through pretty clearly. So uh, putting 0:06:43.360 --> 0:06:46.640 one of the ground based radio telescopes in orbit really 0:06:46.680 --> 0:06:51.080 wouldn't improve its ability to detect signals um, at least 0:06:51.080 --> 0:06:53.680 based on my research, and not not within anything that's 0:06:53.720 --> 0:06:56.279 within those wavelengths. Yeah. Actually it's it's a little tricky 0:06:56.320 --> 0:06:59.280 to detect that stuff anyway, because we're talking about really 0:06:59.680 --> 0:07:03.280 we signals. I mean, by the time they reached the Earth, 0:07:03.320 --> 0:07:05.640 that these signals are not very strong at all. In fact, 0:07:06.200 --> 0:07:10.840 one one reference I I looked at said that that 0:07:11.240 --> 0:07:13.920 if you were to add up all the energy that 0:07:14.080 --> 0:07:17.960 every radio telescope on Earth had been subjected to since 0:07:18.040 --> 0:07:21.200 they were built, it still would not equal the energy 0:07:21.240 --> 0:07:24.920 would find in the snowflake. Yeah, that's pretty impressive. Act 0:07:25.240 --> 0:07:28.720 grant that snowflake is the size of Detroit. No, I'm kidding, 0:07:28.720 --> 0:07:32.240 I'm kidding. Typical snowflake. No. Uh. And it is also 0:07:32.360 --> 0:07:35.760 worthwhile to note, especially before anyone writes in um, that 0:07:35.880 --> 0:07:39.800 radio telescopes do have to be placed away from population 0:07:39.840 --> 0:07:44.120 centers in general, uh, to some degree to because there 0:07:44.240 --> 0:07:47.720 is earthly interference. Yeah, there's terrestrial radio interference that you 0:07:47.800 --> 0:07:50.720 have to try and minimize as much as possible. Otherwise 0:07:51.040 --> 0:07:52.840 it's just so much noise that you're not going to 0:07:52.920 --> 0:07:56.920 even find any signal out there, right right, So, um, Yeah, 0:07:57.040 --> 0:07:58.920 it has its it has its good points and in 0:07:59.000 --> 0:08:03.880 its ad points because of the frequencies, it's able to monitor. 0:08:04.200 --> 0:08:06.080 And it's a good point too that you uh, you 0:08:06.120 --> 0:08:10.560 mentioned the from the very first because these these devices, 0:08:10.600 --> 0:08:12.880 I mean, I'm I imagine people you know, have a 0:08:12.880 --> 0:08:16.000 good idea what radio telescopes look like. I mean, we've 0:08:16.000 --> 0:08:19.840 all seen satellite dishes, and to some degree that's more 0:08:19.960 --> 0:08:21.680 or less what they look like. In fact, you may 0:08:21.720 --> 0:08:24.960 have seen pictures of them, but um that I think 0:08:25.520 --> 0:08:29.400 gives it the the sort of feeling that it's a 0:08:29.400 --> 0:08:33.000 fairly recent thing. And in fact, um it was somebody 0:08:33.120 --> 0:08:38.040 in uh nine thirty three who who figured out that, um, 0:08:38.200 --> 0:08:43.559 there was, uh, there were radio frequencies coming from extraterrestrial bodies. 0:08:44.240 --> 0:08:50.360 Someone at of course Bell telephone laboratories, laboratories. You always 0:08:50.360 --> 0:08:53.000 do that. I can't fight it, that I can't fight 0:08:53.040 --> 0:08:57.079 this feeling anymore. I can't. But yes, so you're talking 0:08:57.080 --> 0:09:01.079 about Carl Carl Jansky. Carl Jansky, Yes, Uh, he he 0:09:01.800 --> 0:09:04.959 built the first antenna that could be used as a 0:09:05.040 --> 0:09:07.360 radio telescope back in ninety one, but it would take 0:09:07.360 --> 0:09:09.560 a couple of years to really figure out, uh, the 0:09:09.559 --> 0:09:12.959 fact that you could use this to to explore the 0:09:13.600 --> 0:09:17.720 heavens above. Because when he built his radio frequency detector, 0:09:18.080 --> 0:09:21.520 it was not to act as a radio telescope. It 0:09:21.600 --> 0:09:24.840 was meant to detect static that could potentially interfere with 0:09:24.960 --> 0:09:28.400 radio telephone services. Right, So he was he was working 0:09:28.480 --> 0:09:32.400 literally on a project for Bell. Yeah, and what happened 0:09:32.440 --> 0:09:35.360 was he discovered that there was this interesting hissing noise 0:09:35.360 --> 0:09:37.600 he was picking up, and that was hitting a cycle. 0:09:38.360 --> 0:09:42.360 The hissing noise would would occur at a certain time 0:09:42.840 --> 0:09:45.560 every day, and the cycle hit, well, not every day, 0:09:45.600 --> 0:09:47.960 the cycle hit every twenty three hours and fifty six minutes, 0:09:48.360 --> 0:09:50.520 And once he removed the snake from the line, he 0:09:50.600 --> 0:09:52.520 realized there was something else hit. He figured out that 0:09:52.559 --> 0:09:54.720 the twenty three hours of fifty six minutes was essentially 0:09:54.800 --> 0:09:57.400 the period that it takes for if you've if you've 0:09:57.400 --> 0:09:59.839 got a fixed point on the sky for the you 0:10:00.000 --> 0:10:02.520 to come background so that you're pointing at that same 0:10:02.720 --> 0:10:06.760 object and come up again later. Eventually he determined that 0:10:06.840 --> 0:10:12.599 this was the the origin of this radio frequency was otherworldly, 0:10:12.960 --> 0:10:15.000 so it was coming from outside the Earth, and that 0:10:15.080 --> 0:10:17.880 it was in fact coming from somewhere in the Sagittarius 0:10:17.960 --> 0:10:23.440 constellation far out. Yeah, so guys, I'm picking up a 0:10:23.480 --> 0:10:26.720 signal from outer space. No, I'm sorry, it's not from 0:10:26.760 --> 0:10:29.760 outer space. It's just from just outside the room. It's Tari, 0:10:29.880 --> 0:10:31.640 She's telling me that we need to take a break 0:10:31.679 --> 0:10:41.520 to thank our sponsor. So it would take a few 0:10:41.520 --> 0:10:45.440 more years before you saw anyone build a parabolic antenna, 0:10:45.480 --> 0:10:47.760 which is what Chris was talking about earlier, the dish 0:10:48.120 --> 0:10:51.439 style antenna. Those are not the only kind of antennas 0:10:51.440 --> 0:10:54.840 that are used in radio telescopes. It's probably, i would argue, 0:10:54.920 --> 0:10:57.959 probably the most iconic and the most common that we 0:10:57.960 --> 0:11:00.160 we see. But there are other types of antenna as, 0:11:00.200 --> 0:11:03.880 including dipole antenna's, cylindrical parabolics, which are they kind of 0:11:03.880 --> 0:11:08.160 look like a trough. Uh there are the yaggy antenna's, 0:11:08.200 --> 0:11:11.199 which are um not little guys who teach you how 0:11:11.240 --> 0:11:15.840 to use kung fu kara, I should say, their horn 0:11:15.920 --> 0:11:18.680 antennas their mills crosses that kind of STU mills crosses 0:11:18.720 --> 0:11:23.560 telescope um. Various ways of doing this, but the principle 0:11:23.679 --> 0:11:26.640 is essentially the same. It's to try and gather to 0:11:26.760 --> 0:11:31.640 detect together as much as radio frequency UM radiation as possible. 0:11:31.640 --> 0:11:37.440 And usually there are several reflectors involved that reflect radio 0:11:37.480 --> 0:11:42.160 frequencies to a focal point that can then send the 0:11:42.240 --> 0:11:46.640 signal to receiver and then from there it gets amplified. 0:11:46.679 --> 0:11:49.320 And we'll go through that process in a little bit. 0:11:49.360 --> 0:11:53.960 But uh so in and the parabolic style of of antenna, 0:11:54.160 --> 0:11:56.520 this is why you have that big dish. The dish 0:11:56.600 --> 0:12:02.720 part is actually reflecting frequencies so that they all are 0:12:02.800 --> 0:12:06.600 directed to a single focal point and that's usually called 0:12:06.600 --> 0:12:09.400 the feed. That's usually a small antenna called the feed 0:12:09.440 --> 0:12:13.040 that uh as often called the feed horn, that will 0:12:13.080 --> 0:12:17.520 collect the signal and send it to the receiver. Yes, 0:12:18.080 --> 0:12:22.160 so these these radio frequencies are, like we said, generated 0:12:22.160 --> 0:12:25.120 by lots of different stuff out there in the in 0:12:25.280 --> 0:12:30.400 the in space. Um so. But the problem is that 0:12:30.360 --> 0:12:35.400 the they're so so delicate. There's so such tiny little 0:12:35.520 --> 0:12:39.040 frequencies that you have to really control for the noise element, 0:12:39.080 --> 0:12:41.880 not just by trying to isolate the antenna of it, 0:12:42.080 --> 0:12:46.360 but also by making sure the material you've used in 0:12:46.480 --> 0:12:50.160 your antenna array is the right kind of stuff, because 0:12:51.000 --> 0:12:55.080 they're pretty sense of things, and also the amount of 0:12:55.200 --> 0:12:59.560 information you can get is very much connected to the 0:12:59.640 --> 0:13:03.720 side of your antenna. Bigger antennas are able to provide 0:13:03.720 --> 0:13:07.840 a higher resolution image. It's kind of a weird word 0:13:07.840 --> 0:13:10.280 to say, because we're not talking about visible light necessarily, 0:13:10.320 --> 0:13:13.760 but an image of what it is you're looking at. Right. So, 0:13:13.760 --> 0:13:16.680 so the larger the better in general. But if you 0:13:16.679 --> 0:13:20.280 start building so large that the material itself is heavy 0:13:20.400 --> 0:13:24.000 enough to warp because it's it's it's so heavy that 0:13:24.480 --> 0:13:28.240 the structure itself can't maintain a specific shape, well, then 0:13:28.240 --> 0:13:31.400 you're not reflecting the radio frequencies to that focal point anymore, 0:13:31.400 --> 0:13:32.880 you've warped it out of shape. So you have to 0:13:32.880 --> 0:13:35.360 build it out of special materials and you have to 0:13:35.480 --> 0:13:39.160 plan for Okay, well, we know that by designing an 0:13:39.160 --> 0:13:42.840 antenna of this size, this particular warping is going to occur, 0:13:42.880 --> 0:13:45.480 so we have to factor that into the design so 0:13:45.520 --> 0:13:48.199 that the warping actually ends up helping rather than hurting. 0:13:48.200 --> 0:13:51.440 And usually you do that by adding a second reflector 0:13:51.520 --> 0:13:54.079 that is that's movable, so you can have a second 0:13:54.120 --> 0:13:57.360 reflector actually um position in such a way where the 0:13:57.720 --> 0:14:01.080 distortion from the main reflector hit the second reflector, which 0:14:01.120 --> 0:14:03.520 then reflects it back to the focal point. So it 0:14:03.520 --> 0:14:05.280 gets a little complicated. In fact, there are two main 0:14:05.520 --> 0:14:10.440 types of secondary reflectors. There's the Cassegrain focus, which is 0:14:11.000 --> 0:14:14.120 a reflector that's in front of the main antenna or 0:14:14.160 --> 0:14:17.160 the main reflector, i should say. And then there's another 0:14:17.160 --> 0:14:19.040 one if you have it in the back. It's called 0:14:19.080 --> 0:14:23.400 Grigoryan focus, and it chants a lot. At a feeling 0:14:23.400 --> 0:14:25.120 you were going to say that, yeah, there was a 0:14:25.120 --> 0:14:30.880 pretty good chance. Uh yeah, it's possible. Um Now, given 0:14:31.400 --> 0:14:34.600 what Johnathan was just talking about, giving the materials and 0:14:34.600 --> 0:14:36.840 and the uh, there are a lot of things that 0:14:36.840 --> 0:14:42.880 that can affect uh, the efficiency of a radio telescope, 0:14:42.960 --> 0:14:49.840 including heat, because the materials will expand or contract, wind, 0:14:50.080 --> 0:14:53.080 the surface of the material itself, the surface of the 0:14:53.120 --> 0:14:56.680 material itself. Um. But other than that, I mean, once 0:14:56.720 --> 0:14:59.760 you take all these things into account, it is theoretically 0:15:00.000 --> 0:15:03.600 possible to build as larger radio telescope as you possibly can. 0:15:03.640 --> 0:15:06.320 There's really no limit to the size other than the 0:15:06.320 --> 0:15:08.200 fact that you're going to have to take things like 0:15:08.600 --> 0:15:12.720 gravity and temperature and things like that into a tensile strength. 0:15:12.920 --> 0:15:17.080 But conceivably, if you could build one that's three times 0:15:17.120 --> 0:15:19.840 the size of Earth, it would work. Yeah. But that 0:15:20.040 --> 0:15:23.080 and that's fascinating because it's it's not it doesn't have 0:15:23.160 --> 0:15:26.920 to be a particularly large or particularly small device. It 0:15:27.080 --> 0:15:29.480 just you know, you can pick up more with it. 0:15:29.600 --> 0:15:32.120 And a lot of a lot of radio telescopes are 0:15:32.160 --> 0:15:35.480 actually telescope like antenna arrays, So it's not just one 0:15:35.520 --> 0:15:38.920 antenna's several antennas working together in order if you to 0:15:38.960 --> 0:15:42.640 gather this information work, that's what I say. And and 0:15:42.760 --> 0:15:46.440 that that helps you create a larger radio telescope just 0:15:46.520 --> 0:15:49.120 but you know, you're adding extra elements, and it means 0:15:49.160 --> 0:15:51.840 that you sort of get around part of the problem, 0:15:51.880 --> 0:15:54.840 which is, you know, building just an enormous single antenna. 0:15:54.920 --> 0:15:57.240 You can do an array of antennas. There are different 0:15:57.240 --> 0:16:01.200 limitations on this as well. Um. So, the signal that 0:16:01.240 --> 0:16:04.880 you're picking up with this radio telescope is really really weak, 0:16:05.800 --> 0:16:08.360 So in order for you to have it, uh and 0:16:08.440 --> 0:16:11.560 to to transmit first you have to you have to 0:16:11.600 --> 0:16:16.640 transfer the radio frequency information by by changing it into electricity. 0:16:16.640 --> 0:16:20.440 But because the frequency signal is so weak, the electric 0:16:20.480 --> 0:16:23.120 current would be pretty pathetic. You would not be able 0:16:23.160 --> 0:16:26.880 to measure it just by converting it right from radio 0:16:26.920 --> 0:16:31.080 frequency to electricity without amplifying it in some way. So 0:16:31.160 --> 0:16:34.600 typically a radio telescope will then have a pre amplifier. 0:16:35.000 --> 0:16:38.800 So you musicians out there and and and radio folks, 0:16:39.080 --> 0:16:41.080 you know, you're probably pretty familiar with the idea of 0:16:41.080 --> 0:16:44.720 a pre amplifier. Microphones usually have a pre amplifier that 0:16:44.800 --> 0:16:47.800 kind of thing. Um So, a pre amplifier is really 0:16:47.880 --> 0:16:50.440 just a a way of boosting a signal a certain 0:16:50.480 --> 0:16:54.680 amount before it gets truly amplified, uh for the final 0:16:54.800 --> 0:16:56.800 use of whatever that signal is gonna be, whether it's 0:16:56.840 --> 0:17:00.920 in the audio industry, or in this case, the measuring 0:17:00.960 --> 0:17:03.920 the celestial bodies. Yeah, I was gonna say that they 0:17:03.920 --> 0:17:08.680 don't necessarily usually have them anyway. Um, well, that's that's fair, 0:17:08.760 --> 0:17:12.160 but it does. It does assist, uh, and in picking 0:17:12.200 --> 0:17:14.040 up these weak signals, that's for sure. Yeah. And so 0:17:14.080 --> 0:17:16.680 the kind that tends to be used in radio telescopes 0:17:16.720 --> 0:17:21.960 are called low noise amplifiers because we're talking about such small, 0:17:22.440 --> 0:17:26.919 very very quiet signals. And so, boy, I'm glad didn't 0:17:26.960 --> 0:17:30.479 do the old listener mail beginning because then with all 0:17:30.520 --> 0:17:32.879 this it would have proably blown everybody's ears out. So 0:17:32.960 --> 0:17:37.240 the the these l n A pre amplifiers take these 0:17:37.359 --> 0:17:40.240 um signals and then they boost them. Now here's the thing. 0:17:41.200 --> 0:17:45.480 Any sort of interference at this point could really compromise 0:17:45.560 --> 0:17:51.000 the measurements you're making. So that includes molecular movement of 0:17:51.080 --> 0:17:55.120 the pre amp. So the fact that you know, everything 0:17:56.200 --> 0:17:58.960 in matter is made up of molecules, and these molecules 0:17:59.000 --> 0:18:03.600 move even in solid objects, right, yes, so they in 0:18:03.720 --> 0:18:08.080 a in big radio telescope facilities, things like the professional 0:18:08.080 --> 0:18:11.040 ones that you would find in say NASA, they tend 0:18:11.040 --> 0:18:14.919 to have to cool down the pre amplifier to reduce 0:18:15.000 --> 0:18:17.800 molecular movement as much as possible, and usually to around 0:18:17.840 --> 0:18:21.960 ten kelvin. It's pretty cold. Pretty cold, yeah, zero kelvin 0:18:22.040 --> 0:18:25.240 means no molecular movement. That's what like the deepest reaches 0:18:25.280 --> 0:18:28.040 of space would be is zero kelvin. So ten kelvin's 0:18:28.080 --> 0:18:31.800 pretty cold. They tend to use liquid helium to cool 0:18:31.880 --> 0:18:35.600 down the this this device low enough so that it 0:18:35.720 --> 0:18:38.960 reduces the chance for it to contribute noise to this signal. 0:18:39.480 --> 0:18:43.879 All right. From there, the signal moves into a mixer, yes, 0:18:44.040 --> 0:18:49.560 where it has a party and networks with people and not. Oh, 0:18:49.800 --> 0:18:53.120 should have taken different notes. Okay, well I'll just work 0:18:53.119 --> 0:18:56.280 from memory here then, um no, a mixer. The mixer's 0:18:56.280 --> 0:18:59.800 purpose is to change the frequency of the signal. Now, 0:18:59.840 --> 0:19:02.919 the signals are very high frequency and uh, and it 0:19:02.960 --> 0:19:07.280 turns out that it's easier to amplify lower frequencies. It's 0:19:07.320 --> 0:19:11.680 possible to amplify higher frequencies, but in general, it takes 0:19:11.920 --> 0:19:17.199 less uh effort to amplify the lower frequency signals. And 0:19:17.720 --> 0:19:19.800 if it's kept it it's high frequency and you're just 0:19:20.040 --> 0:19:22.840 you're you're working with the frequency at that and it's 0:19:23.040 --> 0:19:26.800 native frequency. There's the chance they'll travel back up the 0:19:26.880 --> 0:19:31.200 antenna and create feedback. It's not dissimilar to what would 0:19:31.200 --> 0:19:34.640 happen with a microphone too close to a speaker, where 0:19:34.640 --> 0:19:39.160 you get that wonderful sound. That's wonderful. Now you're you're 0:19:39.160 --> 0:19:41.479 probably more familiar with it than I am with your 0:19:41.560 --> 0:19:46.879 rock and roll lifestyle and all. So then what happens 0:19:46.920 --> 0:19:49.960 is the mixer mixes this frequency, not just it doesn't 0:19:50.000 --> 0:19:52.159 just lower. The way it lowers this frequency is it 0:19:52.200 --> 0:19:56.480 mixes the frequency with a frequency generated by an oscillator. Okay, 0:19:56.520 --> 0:19:59.880 so the oscillator creates two frequencies that are both sent 0:20:00.000 --> 0:20:04.040 into the mixer, and uh one is there the polar 0:20:04.080 --> 0:20:08.159 opposites of each other. And so the the mixer adds 0:20:08.160 --> 0:20:13.520 in the lower frequency together with the frequency that came 0:20:13.560 --> 0:20:18.399 in through the receiver, and that is what it sends 0:20:18.400 --> 0:20:25.879 out to the intermediate frequency amplifier. So we've gone PREAMPTI mixer. 0:20:26.000 --> 0:20:29.440 Mixer pulls in a second frequency from the oscillator, the 0:20:29.480 --> 0:20:33.040 oscillator frequency, the lower one gets combined with the incoming 0:20:33.040 --> 0:20:36.400 frequency that is then sent to the intermediate frequency amplifier 0:20:36.440 --> 0:20:40.640 or i F amplifier. And that just process that says 0:20:40.720 --> 0:20:42.800 is that signal and amplifies it. And we've talked about 0:20:42.800 --> 0:20:44.800 amplifiers before in this podcast, so I'm not going to 0:20:44.880 --> 0:20:48.840 get into that. Uh. And then this, this stronger signal 0:20:49.200 --> 0:20:52.960 from the i F amplifier gets sent to Well, now 0:20:53.000 --> 0:20:54.960 we've got to go to the square law detectors and 0:20:55.000 --> 0:21:00.040 the d C processors because we have to create a 0:21:00.160 --> 0:21:03.439 d see a direct current in order for that to 0:21:03.520 --> 0:21:08.560 go to a recording device. So this converts the frequency 0:21:08.600 --> 0:21:11.880 from the amplifier to direct current signals, and it smooths 0:21:11.880 --> 0:21:14.560 out the signals to make them easier to measure because 0:21:14.560 --> 0:21:17.520 they fluctuate quite a bit. Even as direct current, they 0:21:17.520 --> 0:21:19.119 tend to fluctuate. So the way they do this is 0:21:19.160 --> 0:21:22.720 they use capacitors. And if you recall we've talked about 0:21:22.760 --> 0:21:28.280 capacitors before too, capacitors store up electricity and then release 0:21:28.320 --> 0:21:30.919 it all at once, right. They're they're kind of like 0:21:30.960 --> 0:21:33.760 a battery that it can store electricity, but unlike a battery, 0:21:34.080 --> 0:21:37.160 it is and it releases all the electricity. It doesn't 0:21:37.200 --> 0:21:40.280 do a constant flow. This, by the way, is the 0:21:40.320 --> 0:21:44.320 reason why it's a bad idea to fiddle around with electronics. 0:21:44.359 --> 0:21:46.840 You don't know a lot about, including things like televisions 0:21:46.840 --> 0:21:51.200 and computers because they have capacitors in them that can 0:21:51.320 --> 0:21:55.880 store high amounts of electricity that are potentially deadly. So 0:21:56.040 --> 0:21:58.960 especially things like computers and televisions, you don't want to, 0:21:59.200 --> 0:22:02.439 you know, just knock a hole in one or you know. 0:22:02.600 --> 0:22:04.560 I have seen like videos. If you've ever seen a 0:22:04.640 --> 0:22:06.879 video of someone who who excellently breaks the television, you 0:22:06.880 --> 0:22:09.960 see a spark go off. That's a capacitor that's that's discharging, 0:22:10.280 --> 0:22:12.840 and those can be very dangerous. Chris and I have 0:22:12.880 --> 0:22:15.080 a little bit more to say about radio telescopes, but 0:22:15.160 --> 0:22:17.960 before we do, let's take another quick break to thank 0:22:18.000 --> 0:22:28.760 our sponsor. I have read an interesting analogy which said, 0:22:29.480 --> 0:22:33.280 imagine that you have a water hose and water is 0:22:33.320 --> 0:22:36.000 moving through the hose, but the pressure keeps changing, so 0:22:36.040 --> 0:22:38.479 the water sometimes it's flowing out very quickly and sometimes 0:22:38.480 --> 0:22:42.840 it's sputtering out. Okay uh. In the case of this 0:22:43.280 --> 0:22:47.280 detecting radio frequencies, you want to a steady um flow 0:22:47.480 --> 0:22:50.240 so that you can measure it properly. So what if 0:22:50.240 --> 0:22:52.760 you were to instead of just measure the measuring the 0:22:52.800 --> 0:22:56.119 water that comes out of the hose, you you direct 0:22:56.119 --> 0:22:58.720 the hose towards a bucket, okay, and at the base 0:22:58.720 --> 0:23:01.280 of the bucket there's this big it that you can 0:23:01.320 --> 0:23:03.520 open up. Well, if you open up the spin on 0:23:03.560 --> 0:23:05.240 the bucket, water is going to flow out at a 0:23:05.320 --> 0:23:08.280 much more steady rate than it's flowing out of the hose. 0:23:09.000 --> 0:23:11.040 That's the kind of idea here with the capacitor, and 0:23:11.080 --> 0:23:13.359 that it's to try and smooth out that signal and 0:23:13.400 --> 0:23:15.440 make it easier to record, and then finally you've got 0:23:15.440 --> 0:23:18.760 the actual recording device. Now, in the old days, the 0:23:18.800 --> 0:23:22.879 recording device was a an old man who said what 0:23:23.160 --> 0:23:26.159 is that? No, it was actually a pen attached to 0:23:26.520 --> 0:23:30.200 a a movable arm and some paper that was pulled 0:23:30.240 --> 0:23:33.600 across and then the movable arm would would move depending 0:23:33.680 --> 0:23:36.600 upon changes in voltage. And so it's very similar to 0:23:37.240 --> 0:23:42.199 uh earthquake detecting equipment. We talked about seismological equipment in 0:23:42.200 --> 0:23:44.960 the past where you see that or even if you 0:23:45.000 --> 0:23:49.320 think also a similar things light detectors, that's what I 0:23:49.320 --> 0:23:51.720 was saying, polygraphs where they have the little the little 0:23:52.000 --> 0:23:54.240 pen that scratches back and forth across the papers, the 0:23:54.240 --> 0:23:57.680 papers going by, similar kind of thing. Um Now in 0:23:57.800 --> 0:24:03.840 October fourteen, yeah, so we when did you go super nova. Um. No, 0:24:04.080 --> 0:24:06.640 so this in this case instead, what's doing is it's 0:24:06.640 --> 0:24:10.120 actually uh, modern ones don't tend to use this anymore. 0:24:10.119 --> 0:24:12.240 They tend to actually send the data directly to a 0:24:12.240 --> 0:24:14.919