WEBVTT - TechStuff looks at Radio Telescopes 0:00:00.280 --> 0:00:02.840 Brought to you by the reinvented two thousand twelve Camra. 0:00:03.160 --> 0:00:08.840 It's ready. Are you get in touch with technology with 0:00:09.000 --> 0:00:14.680 text Stuff from houstuff works dot com. This podcast is 0:00:14.680 --> 0:00:17.320 brought to you by Audible dot com, the Internet's leading 0:00:17.360 --> 0:00:20.200 provider of audio books, with more than one hundred thousand 0:00:20.239 --> 0:00:24.520 downloadable titles across all types of literature. For tex Stuff listeners, 0:00:24.680 --> 0:00:27.440 Audible is offering a free audiobook to give you a 0:00:27.520 --> 0:00:30.480 chance to try out their service. One audio book to 0:00:30.560 --> 0:00:35.000 consider is The Singularity Is Near When Humans Transcend Biology 0:00:35.159 --> 0:00:38.800 by Ray kirtzwil Churtswaile explores a future where man and 0:00:38.880 --> 0:00:41.880 machine are one and the same. Text Stuff is fascinated 0:00:41.880 --> 0:00:44.400 by the idea of singularity, and this is a great 0:00:44.400 --> 0:00:47.560 book to learn more about it. The Singularity Is Near 0:00:47.640 --> 0:00:52.360 When Humans Transcend Biology by Ray kirtzwild available from Audible. 0:00:53.240 --> 0:00:55.440 To try Audible free to day and get a free 0:00:55.440 --> 0:00:58.440 audiobook of your choice. Get to an Audible podcast dot 0:00:58.480 --> 0:01:03.720 com slash tech Stuff. That's Audible podcast dot com slash 0:01:03.920 --> 0:01:10.080 tech Stuff. Hello everyone, and welcome to tech Stuff. My 0:01:10.160 --> 0:01:12.200 name is Chris Poulette and I am an editor at 0:01:12.200 --> 0:01:14.800 how stuff works dot com. Sitting here across from me. 0:01:14.880 --> 0:01:16.560 A guy who used to be an adventurer like you 0:01:16.640 --> 0:01:18.759 until he took an arrow to the knee is senior 0:01:18.760 --> 0:01:22.280 writer Jonathan Strickland. The sky above the port was the 0:01:22.280 --> 0:01:28.360 color of television. Tune to a dead channel. It's good guy, Okay, 0:01:28.440 --> 0:01:30.520 So um, before we get started, we're gonna do something 0:01:30.520 --> 0:01:33.559 we haven't done a little while. Yeah, we're gonna listen 0:01:33.560 --> 0:01:41.480 to a little listener mail. This listener mail comes from Minka, 0:01:41.600 --> 0:01:44.360 who says I love your podcast and have enjoyed listening 0:01:44.360 --> 0:01:47.319 to your incifle and quirky explanations immensely. I tried to 0:01:47.319 --> 0:01:49.040 search through the past podcast to see if you have 0:01:49.120 --> 0:01:51.640 done one on radio telescopes, to no avail, So I 0:01:51.680 --> 0:01:53.680 hope I didn't just miss it. It seems to me 0:01:53.720 --> 0:01:56.320 that radio telescopes are being used frequently to learn about 0:01:56.320 --> 0:01:59.320 this and study the far reaches of the galaxy and beyond, 0:01:59.720 --> 0:02:01.560 and it's pretty darn cool, so it'd be neat to 0:02:01.640 --> 0:02:03.760 learn more about how they work. Thanks and thanks for 0:02:03.800 --> 0:02:07.440 the show, Minka. Well you're welcome, Minga. I just wanted 0:02:07.440 --> 0:02:09.000 to say you're welcome, all right. So now we're moving 0:02:09.040 --> 0:02:13.200 on to our topic, the Smurfs. No No, we're gonna 0:02:13.200 --> 0:02:17.560 talk about radio telescopes. Yeah, we sort of. Well, we've 0:02:17.600 --> 0:02:20.840 talked about things that relate to radio telescopes like radio 0:02:21.680 --> 0:02:25.600 and set yes and set CD, which does very much 0:02:26.000 --> 0:02:30.080 relate to radio telescopes. Well, what do radio telescopes do? 0:02:30.200 --> 0:02:33.240 Why are they important? Well, it's funny that you should 0:02:33.240 --> 0:02:37.680 mention that, because they're my notes crashed, so I don't 0:02:37.720 --> 0:02:40.359 know what I'm talking about. I'm not I'm just kidding. 0:02:40.360 --> 0:02:43.240 They're still up. He can't see my computer from where 0:02:43.280 --> 0:02:45.959 he sits. Yes, because he's sitting directly across from me. Yes. 0:02:46.240 --> 0:02:48.239 See if if you ever wondered if that was true 0:02:48.320 --> 0:02:51.359 or not, it is. Yeah, um no, it's it's actually 0:02:51.520 --> 0:02:57.239 using It's unlike a typical visual telescope, which uses lenses 0:02:57.520 --> 0:03:00.400 and your eyeball and you look through it and you 0:03:00.440 --> 0:03:02.720 look for stuff on the other side and base it 0:03:02.760 --> 0:03:05.239 directs light which is in the visible spectrum of the 0:03:05.280 --> 0:03:10.200 electromagnetic frequency to our to our eyeballs. Ultimately right, right, 0:03:10.320 --> 0:03:14.679 But and again another drastic oversimplification of the parts. But 0:03:14.880 --> 0:03:18.600 a radio telescope is actually monitoring different parts of the 0:03:18.639 --> 0:03:22.560 electromagnetic frequency. Yeah, yeah, it's good looking at a completely 0:03:22.560 --> 0:03:24.680 different spectrum, So this is part of the spectrum that 0:03:24.840 --> 0:03:28.400 is not visible to the naked eye. So we are 0:03:28.480 --> 0:03:33.480 using these telescopes to measure um radio frequency variations that 0:03:34.000 --> 0:03:37.000 come from outer space. And it turns out that lots 0:03:37.040 --> 0:03:41.640 of stuff out there generates radio frequencies, right, So things 0:03:41.720 --> 0:03:48.120 like quasars, pulsars, galaxies, uh, distant stars, these sort of 0:03:48.120 --> 0:03:53.480 things can generate electromagnetic radiation and in the form of 0:03:53.680 --> 0:03:58.920 radio frequencies. And sometimes these are are objects that we 0:03:59.040 --> 0:04:02.400 can't detect visually, but we can detect them if we 0:04:02.480 --> 0:04:09.120 have a sensitive enough tool that can can detect and 0:04:09.240 --> 0:04:13.680 measure radio frequencies. So that's really what a radio telescope 0:04:13.760 --> 0:04:16.880 is all about. And it's kind of tricky picking up 0:04:17.040 --> 0:04:21.560 radio frequencies from outer space because only certain the actual 0:04:21.680 --> 0:04:25.400 band of frequencies or wavelengths I should say, the band 0:04:25.440 --> 0:04:29.880 of wavelengths that exist within the electromatic magnetic spectrum that 0:04:30.000 --> 0:04:34.560 our radio frequency waves. It's pretty broad, Yeah, about ten 0:04:34.680 --> 0:04:39.599 meters and to one millimeter. That's a pretty good size. Yeah, 0:04:39.640 --> 0:04:41.919 you can actually get radio waves that are even longer 0:04:41.960 --> 0:04:45.119 than that, like the size of football fields. But here's 0:04:45.120 --> 0:04:48.400 the thing is that the Earth has a level of 0:04:48.440 --> 0:04:52.120 the atmosphere called the iona sphere. Now, the iona sphere 0:04:52.480 --> 0:04:55.839 is uh, it's kind of funky. So you guys probably 0:04:55.880 --> 0:04:58.440 have heard us talk about ions before, you know. That's 0:04:58.440 --> 0:05:02.640 when we're talking about uh, atoms that have either gained 0:05:02.680 --> 0:05:05.680 or lost an electron. And if you ionize something, that 0:05:05.680 --> 0:05:08.080 means you've got some free electrons roaming around in it. 0:05:08.120 --> 0:05:11.320 So like an ionized gas or a plasma can actually 0:05:11.320 --> 0:05:15.080 hold carry an electric charge. Right, Yes, why are you 0:05:15.120 --> 0:05:19.360 smiling at me just because I saw a whole bunch 0:05:19.400 --> 0:05:24.160 of people going free electrons? Yeah, they're so expensive otherwise 0:05:24.360 --> 0:05:27.120 that's true. Have you seen my electric bill? Anyway? So 0:05:27.480 --> 0:05:30.600 you have the ionosphere, whether these free roaming electrons out there, 0:05:30.680 --> 0:05:33.400 and uh, and it kind of acts as a bit 0:05:33.600 --> 0:05:38.040 of a a shield or reflector in in some ways. 0:05:38.360 --> 0:05:43.120 And so radio waves of a certain wavelength cannot pass 0:05:43.360 --> 0:05:46.400 through the ionosphere. Essentially, anything that's ten meters are longer. 0:05:46.680 --> 0:05:49.720 The ionosphere is opaque to those. That's why you can 0:05:49.760 --> 0:05:55.400 actually broadcast certain long wavelength radio waves uh and bank 0:05:55.480 --> 0:05:59.839 them off the ionosphere, right because it won't pass through. Now, 0:06:00.400 --> 0:06:03.800 when you start getting shorter than a ten meter wave length, 0:06:04.440 --> 0:06:07.360 you have radio waves that can pass through the ionosphere. 0:06:07.400 --> 0:06:10.880 But if it's longer than twenty centimeters, which is about 0:06:10.880 --> 0:06:13.279 one point five gig hurts in frequency when you're talking 0:06:13.279 --> 0:06:17.159 about these, If it's longer than twenty centimeters, you start 0:06:17.240 --> 0:06:21.080 to have distortion as it passes through the ionosphere. It's 0:06:21.080 --> 0:06:24.880 called scintillation. And this isn't that different from the way 0:06:24.880 --> 0:06:26.880 when we look up into the sky and we see 0:06:27.000 --> 0:06:29.359 stars twinkling. That's sort of the same sort of thing 0:06:29.360 --> 0:06:32.400 we talked about being scintillating, same kind of idea, except 0:06:32.440 --> 0:06:34.240 in this case. You know, that's we're talking about the 0:06:34.320 --> 0:06:39.080 visual spectrum there, but here, Yeah, the twenty centimeters are longer, 0:06:39.360 --> 0:06:42.560 you run into that problem, and so that's not entirely 0:06:42.640 --> 0:06:48.040 useful for measurement purposes. So radio telescopes tend to focus 0:06:48.160 --> 0:06:52.760 on pun intended uh. Wavelengths that are between one centimeter 0:06:52.839 --> 0:06:56.840 and twenty centimeters in length tend to Now there are 0:06:56.920 --> 0:06:59.400 some variations, and also if you were to have a 0:06:59.480 --> 0:07:03.000 radio tell scope, say in orbit, where it's you know, 0:07:03.080 --> 0:07:06.919 you don't have the ionosphere as a in play. Um, 0:07:06.960 --> 0:07:10.560 that's a different story. But ground based radio telescopes kind 0:07:10.560 --> 0:07:12.920 of had to play within these rules because the way 0:07:12.960 --> 0:07:16.080 the ionosphere works. One of the nice things though about 0:07:16.200 --> 0:07:21.280 the radio telescope is that, uh, those frequencies generally come 0:07:21.360 --> 0:07:25.440 through pretty clearly. So uh, putting one of the ground 0:07:25.480 --> 0:07:29.560 based radio telescopes in orbit really wouldn't improve its ability 0:07:29.680 --> 0:07:33.320 to detect signals, UM, at least based on my research, 0:07:33.600 --> 0:07:36.640 not not within anything that's within those wavelengths. Yeah. Actually, 0:07:36.680 --> 0:07:39.040 it's it's a little tricky to detect that stuff anyway, 0:07:39.080 --> 0:07:43.120 because we're talking about really weak signals. I mean, by 0:07:43.120 --> 0:07:45.640 the time they reached the Earth, that these signals are 0:07:45.640 --> 0:07:49.040 not very strong at all. In fact, one one reference 0:07:49.080 --> 0:07:52.840 I I looked at said that, um that if you 0:07:52.880 --> 0:07:56.120 were to add up all the energy that every radio 0:07:56.160 --> 0:08:00.320 telescope on Earth had been subjected to since they were built, 0:08:00.880 --> 0:08:03.040 it still would not equal the energy would find in 0:08:03.040 --> 0:08:06.880 the snowflake. Yeah, that's pretty impressive. Actor. Now, grant that 0:08:06.920 --> 0:08:10.520 snowflake is the size of Detroit. No, I'm kidding, I'm kidding, 0:08:10.800 --> 0:08:14.720 typical snowflake. No. Uh. And it is also worthwhile to note, 0:08:14.800 --> 0:08:18.400 especially before anyone writes in UM, that radio telescopes do 0:08:18.480 --> 0:08:23.320 have to be placed away from population centers in general, uh, 0:08:23.360 --> 0:08:27.080 to some degree to because there is earthly interference. Yeah, 0:08:27.120 --> 0:08:29.680 those terrestrial radio interference that you have to try and 0:08:29.680 --> 0:08:33.200 minimize as much as possible. Otherwise it's just so much 0:08:33.240 --> 0:08:35.400 noise that you're not going to even find any signal 0:08:35.559 --> 0:08:38.920 out there, right right, So, um, yeah, it has its 0:08:39.000 --> 0:08:41.520 it has its good points and it's bad points simply 0:08:41.559 --> 0:08:45.640 because of the the frequencies it's able to monitor. And 0:08:45.679 --> 0:08:47.880 it's a good point too that you uh you mentioned 0:08:48.360 --> 0:08:52.120 the from the very first because these these devices. I mean, 0:08:52.120 --> 0:08:54.840 I imagine people you know, have a good idea what 0:08:55.000 --> 0:08:58.560 radio telescopes look like. I mean, we've all seen satellite dishes, 0:08:58.600 --> 0:09:02.000 and to some degree that's more or less what they 0:09:02.040 --> 0:09:04.240 look like. In fact, you may have seen pictures of them. 0:09:04.280 --> 0:09:09.560 But um, that I think gives it the this sort 0:09:09.600 --> 0:09:12.640 of feeling that it's a fairly recent thing. And in fact, 0:09:13.080 --> 0:09:17.320 um it was somebody in uh nineteen thirty three who 0:09:17.360 --> 0:09:21.080 who figured out that um there was uh, there were 0:09:21.160 --> 0:09:26.760 radio frequencies coming from extraterrestrial bodies, someone at of course 0:09:27.360 --> 0:09:33.280 Bell telephone laboratories. You always do that. I can't fight 0:09:33.320 --> 0:09:36.400 it that, I can't fight this feeling anymore. I can't. 0:09:37.280 --> 0:09:42.040 But yes, so you're talking about Carl Carl Jansky. Carl Jansky, Yes, uh. 0:09:42.080 --> 0:09:46.079 He he built the first antenna that could be used 0:09:46.120 --> 0:09:48.240 as a radio telescope back in nineteen thirty one, but 0:09:48.240 --> 0:09:50.719 it would take a couple of years to really figure out, uh, 0:09:50.800 --> 0:09:54.120 the fact that you could use this to to explore 0:09:54.240 --> 0:09:59.040 the heavens above. Because when he built his radio frequency detector, 0:09:59.400 --> 0:10:02.840 it was not to act as a radio telescope. It 0:10:02.920 --> 0:10:06.160 was meant to detect static that could potentially interfere with 0:10:06.280 --> 0:10:09.720 radio telephone services. Right. So he was he was working 0:10:09.800 --> 0:10:13.720 literally on a project for Bell. Yeah, And what happened 0:10:13.760 --> 0:10:16.679 was he discovered that there was this interesting hissing noise 0:10:16.679 --> 0:10:18.920 he was picking up and it was hitting a cycle. 0:10:19.679 --> 0:10:23.679 The hissing noise would would occur at a certain time 0:10:24.160 --> 0:10:26.880 every day, and the cycle hit, well, not every day, 0:10:26.920 --> 0:10:29.280 the cycle hit every twenty three hours and fifty six minutes. 0:10:29.720 --> 0:10:31.839 And once he removed the snake from the line, he 0:10:31.920 --> 0:10:33.880 realized there was something else hit. He figured out that 0:10:33.920 --> 0:10:36.080 the twenty three hours of fifty six minutes was essentially 0:10:36.120 --> 0:10:38.719 the period that it takes for if you've if you've 0:10:38.720 --> 0:10:41.360 got a fixed point on the sky for you to 0:10:41.440 --> 0:10:44.559 come back round, so that you're pointing at that same object. 0:10:44.800 --> 0:10:48.120 This will come up again later. Eventually he determined that 0:10:48.160 --> 0:10:53.920 this was the the origin of this radio frequency was otherworldly, 0:10:54.280 --> 0:10:56.320 so it was coming from outside the Earth, and that 0:10:56.400 --> 0:10:59.200 it was in fact coming from somewhere in the Sagittarius 0:10:59.280 --> 0:11:04.640 constellation far out. Yeah, so it would take a few 0:11:04.679 --> 0:11:08.600 more years before you saw anyone build a parabolic antenna, 0:11:08.640 --> 0:11:10.920 which is what Chris was talking about earlier, the dish 0:11:11.280 --> 0:11:14.560 style antenna. Those are not the only kind of antennas 0:11:14.600 --> 0:11:18.000 that are used in radio telescopes. It's probably, i would argue, 0:11:18.080 --> 0:11:21.120 probably the most iconic and the most common that we 0:11:21.120 --> 0:11:23.720 we see. But there are other types of antennas, including 0:11:23.760 --> 0:11:27.199 dipole antenna's, cylindrical parabolics, which are they kind of look 0:11:27.240 --> 0:11:31.560 like a trough. Uh. There are the yaggy antenna's, which 0:11:31.559 --> 0:11:34.480 are um not little guys who teach you how to 0:11:35.400 --> 0:11:39.599 use kung fu karate, I should say, their horn antennas, 0:11:39.600 --> 0:11:42.360 their mills crosses that kind of stuff. Mills crosses. Telescope 0:11:42.480 --> 0:11:46.720 is um various ways of doing this, but the principle 0:11:46.840 --> 0:11:49.760 is essentially the same. It's to try and gather to 0:11:49.880 --> 0:11:54.800 detect together as much as radio frequency um radiation as possible, 0:11:54.800 --> 0:12:00.600 and usually there are several reflectors involved that reflect radio 0:12:00.640 --> 0:12:05.360 frequencies to a focal point that can then send the 0:12:05.360 --> 0:12:09.800 signal to receiver and then from there it gets amplified. 0:12:09.840 --> 0:12:12.480 And we'll go through that process in a little bit. 0:12:12.520 --> 0:12:16.480 But uh so, in our and the parabolic style of 0:12:16.480 --> 0:12:19.120 of antenna, this is why you have that big dish. 0:12:19.200 --> 0:12:24.839 The dish part is actually reflecting um frequencies so that 0:12:24.920 --> 0:12:28.880 they all are directed to a single focal point and 0:12:28.960 --> 0:12:31.920 that's usually called the feed that's usually a small antenta 0:12:32.000 --> 0:12:35.199 called the feed that us often called the feed horn 0:12:35.760 --> 0:12:40.679 that will collect the signal and send it to the receiver. Yes, 0:12:41.240 --> 0:12:45.280 so these these radio frequencies are, like we said, generated 0:12:45.280 --> 0:12:48.320 by lots of different stuff out there in the in 0:12:48.440 --> 0:12:53.559 the in space. Um so. But the problem is that 0:12:53.520 --> 0:12:59.319 they're so so delicate. There's so such tiny little frequencies 0:12:59.640 --> 0:13:02.200 that you have to really control for the noise element, 0:13:02.240 --> 0:13:05.040 not just by trying to isolate the antenna of it, 0:13:05.200 --> 0:13:09.520 but also by making sure the material you've used in 0:13:09.640 --> 0:13:13.320 your antenna array is the right kind of stuff, because 0:13:14.160 --> 0:13:18.880 they're pretty sensitive things. And also the amount of information 0:13:18.920 --> 0:13:23.199 you can get is very much connected to the size 0:13:23.240 --> 0:13:26.920 of your antenna. Bigger antennas are able to provide a 0:13:27.000 --> 0:13:31.199 higher resolution image. It's kind of a weird word to say, 0:13:31.200 --> 0:13:34.040 because we're not talking about visible light necessarily, but an 0:13:34.120 --> 0:13:36.880 image of what it is you're looking at. Right. So, 0:13:36.880 --> 0:13:39.840 so the larger the better in general. But if you 0:13:39.840 --> 0:13:43.480 start building so large that the material itself is heavy 0:13:43.559 --> 0:13:47.160 enough to warp because it's it's it's so heavy that 0:13:47.640 --> 0:13:51.360 the structure itself can't maintain a specific shape, well then 0:13:51.400 --> 0:13:54.559 you're not reflecting the radio frequencies to that focal point anymore. 0:13:54.559 --> 0:13:56.040 You've warped it out of shape. So you have to 0:13:56.040 --> 0:13:58.520 build it out of special materials, and you have to 0:13:58.640 --> 0:14:02.120 plan for Okay, while uh, we know that by designing 0:14:02.160 --> 0:14:05.559 an antenna of this size, this particular warping is going 0:14:05.559 --> 0:14:07.640 to occur, so we have to factor that into the 0:14:07.720 --> 0:14:10.839 design so that the warping actually ends up helping rather 0:14:10.880 --> 0:14:13.360 than hurting. And usually you do that by adding a 0:14:13.400 --> 0:14:16.640 second reflector that is that's movable, so you can have 0:14:16.840 --> 0:14:20.080 a second reflector actually um position in such a way 0:14:20.120 --> 0:14:24.000 where the distortion from the main reflector hits the second reflector, 0:14:24.040 --> 0:14:26.600 which then reflects it back to the focal point, so 0:14:26.640 --> 0:14:28.160 it gets a little complicated. In fact, there are two 0:14:28.240 --> 0:14:33.160 main types of secondary reflectors. There's the Cassegrain focus, which 0:14:33.480 --> 0:14:36.440 is a reflector that's in front of the main antenna 0:14:37.200 --> 0:14:40.040 or the main reflector, i should say. And then there's 0:14:40.040 --> 0:14:41.960 another one if you have it in the back. It's 0:14:41.960 --> 0:14:46.600 called Grigoryan focus, and it chants a lot feeling you 0:14:46.640 --> 0:14:48.600 were going to say that, yeah, there was a pretty 0:14:48.600 --> 0:14:54.840 good chance. Uh, yeah, it's possible. Um. Now, given what 0:14:54.840 --> 0:14:57.760 what Jonathan was just talking about, giving the materials and 0:14:57.760 --> 0:15:00.040 and the uh, there are a lot of things that 0:15:00.040 --> 0:15:06.040 that can affect, uh, the efficiency of a radio telescope, 0:15:06.160 --> 0:15:11.200 including heat or cold, because the materials will expand or 0:15:11.240 --> 0:15:15.600 contract right wind the surface of the material itself, the 0:15:15.640 --> 0:15:18.720 surface of the material itself. Um. But other than that, 0:15:18.760 --> 0:15:21.600 I mean, once you take all these things into account, 0:15:21.920 --> 0:15:25.240 it is theoretically possible to build as large a radio 0:15:25.240 --> 0:15:28.000 telescope as you possibly can. There's really no limit to 0:15:28.040 --> 0:15:30.360 the size other than the fact that you're going to 0:15:30.400 --> 0:15:34.280 have to take things like gravity and temperature and things 0:15:34.320 --> 0:15:38.000 like that into a tensile strength. But conceivably, if you 0:15:38.000 --> 0:15:40.960 could build one that's three times the size of Earth, 0:15:41.080 --> 0:15:44.600 it would work. But that and that's fascinating because it's 0:15:44.640 --> 0:15:47.880 it's not it doesn't have to be a particularly large 0:15:47.920 --> 0:15:51.560 or particularly small device. It just you know, you can 0:15:51.600 --> 0:15:54.120 pick up more with it. And a lot of a 0:15:54.120 --> 0:15:57.720 lot of radio telescopes are actually telescope like antenna a rays, 0:15:57.760 --> 0:16:00.960 so it's not just one antenna's several antenna's working together 0:16:01.440 --> 0:16:06.200 in order for you to gather this information, and that 0:16:06.200 --> 0:16:09.720 that helps you create a larger radio telescope just but 0:16:09.920 --> 0:16:12.400 you know, you're adding extra elements in. It means that 0:16:12.440 --> 0:16:15.360 you sort of get around part of the problem, which is, 0:16:15.360 --> 0:16:18.320 you know, building just an enormous single antenna. You can 0:16:18.360 --> 0:16:21.200 do an array of antennas. There are different limitations on 0:16:21.240 --> 0:16:24.800 this as well. Um So the signal that you're picking 0:16:24.840 --> 0:16:29.160 up with this radio telescope is really really weak, So 0:16:29.240 --> 0:16:31.960 in order for you to have it and to to 0:16:32.160 --> 0:16:35.360 transmit first you have to you have to transfer the 0:16:35.440 --> 0:16:39.880 radio frequency information by by changing it into electricity. But 0:16:40.280 --> 0:16:43.920 because the frequency signal is so weak, the electric current 0:16:43.960 --> 0:16:46.640 would be pretty pathetic. You would not be able to 0:16:46.680 --> 0:16:50.560 measure it just by converting it right from radio frequency 0:16:50.600 --> 0:16:54.880 to electricity without amplifying it in some way. So typically 0:16:55.040 --> 0:16:58.280 a radio telescope will then have a pre amplifier. So 0:16:58.440 --> 0:17:02.440 you musicians out there and and and radio folks, you know, 0:17:02.480 --> 0:17:05.160 you're probably pretty familiar with the idea of a pre amplifier. 0:17:05.600 --> 0:17:09.040 Microphones usually have a pre amplifier, that kind of thing. Um, 0:17:09.240 --> 0:17:12.320 So a pre amplifier is really just a a way 0:17:12.320 --> 0:17:15.320 of boosting a signal a certain amount before it gets 0:17:15.359 --> 0:17:18.639 truly amplified, uh, for the final use of whatever that 0:17:18.680 --> 0:17:21.760 signal is gonna be, whether it's in the audio industry 0:17:21.880 --> 0:17:25.800 or in this case, the measuring the celestial bodies. Yeah, 0:17:25.960 --> 0:17:27.919 I was I was gonna say that they don't necessarily 0:17:28.280 --> 0:17:32.000 usually have them anyway. Um, well, that's that's fair, but 0:17:32.040 --> 0:17:35.439 it does it does assist, uh, and in picking up 0:17:35.440 --> 0:17:37.480 these weak signals, that's for sure. Yeah. And so the 0:17:37.560 --> 0:17:40.000 kind that tends to be used in radio telescopes are 0:17:40.000 --> 0:17:45.119 called low noise amplifiers because we're talking about such small, 0:17:45.560 --> 0:17:49.720 very very quiet and signals. And so, boy, I'm glad 0:17:49.760 --> 0:17:52.280 didn't do the old listener mail will be getting because 0:17:52.320 --> 0:17:54.560 then it with all this, it would have probly blown 0:17:54.600 --> 0:17:58.280 everybody's ears out. So the the these l n A 0:17:58.400 --> 0:18:02.480 pre amplifiers take these um signals and then they boost 0:18:02.520 --> 0:18:06.640 them now here's the thing. Any sort of interference at 0:18:06.640 --> 0:18:10.480 this point could really compromise the measurements you're making. So 0:18:11.240 --> 0:18:17.080 that includes molecular movement of the pre amp. So the 0:18:17.119 --> 0:18:20.679 fact that you know, everything in matter is made up 0:18:20.680 --> 0:18:24.200 of molecules, and these molecules move even in solid objects, right, 0:18:25.440 --> 0:18:30.320 So they in in a in big radio telescope facilities, 0:18:30.320 --> 0:18:32.199 things like the professional ones that you would find in 0:18:32.240 --> 0:18:35.800 say NASA, they tend to have to cool down the 0:18:35.920 --> 0:18:39.920 pre amplifier to reduce molecular movement as much as possible, 0:18:39.960 --> 0:18:44.240 and usually to around ten kelvin. It's pretty cold. Pretty cold, yeah, 0:18:44.320 --> 0:18:47.639 zero kelvin means no molecular movement. That's what like the 0:18:47.680 --> 0:18:50.760 deepest reaches of space would be zero kelvin. So ten 0:18:50.840 --> 0:18:54.320 kelvin's pretty cold. They tend to use liquid helium to 0:18:54.640 --> 0:18:58.120 cool down the this this device low enough so that 0:18:58.680 --> 0:19:01.480 it reduces the chance for it to contribute noise to 0:19:01.520 --> 0:19:04.879 this signal. All right. From there, the signal moves into 0:19:04.960 --> 0:19:09.200 a mixer, yes, where it has a party and networks 0:19:09.200 --> 0:19:15.080 with people and not. Oh, should have taken different notes. Okay, 0:19:15.080 --> 0:19:17.760 well I'll just work from memory here then. Um No, 0:19:17.920 --> 0:19:20.639 a mixer, what the mixer's purpose is to change the 0:19:20.720 --> 0:19:24.200 frequency of the signal. Now, these signals are very high 0:19:24.200 --> 0:19:28.439 frequency and UH, and it turns out that it's easier 0:19:28.520 --> 0:19:32.720 to amplify lower frequencies. It's possible to amplify higher frequencies, 0:19:32.720 --> 0:19:37.600 but in general, it takes less UH effort to amplify 0:19:37.680 --> 0:19:41.760 the lower frequency signals. And if it's kept at it's 0:19:41.840 --> 0:19:44.560 high frequency and you're just you're you're working with the 0:19:44.600 --> 0:19:48.680 frequency at that and it's native frequency, there's the chance 0:19:48.720 --> 0:19:51.800 that will travel back up the antenna and create feedback. 0:19:52.520 --> 0:19:56.440 It's not dissimilar to what would happen with a microphone 0:19:56.680 --> 0:19:58.600 too close to a speaker, where you get that wonderful 0:19:59.680 --> 0:20:03.240 sound that's not wonderful. Now you're you're probably more familiar 0:20:03.240 --> 0:20:05.119 with it than I am, with your rock and roll 0:20:05.160 --> 0:20:10.600 lifestyle and all. So then what happens is the mixer 0:20:11.000 --> 0:20:13.919 mixes this frequency, not just it doesn't just lower. The 0:20:13.920 --> 0:20:16.360 way it lowers this frequency is it mixes the frequency 0:20:16.440 --> 0:20:19.879 with a frequency generated by an oscillator. Okay, so the 0:20:19.920 --> 0:20:23.439 oscillator creates two frequencies that are both sent into the 0:20:23.480 --> 0:20:28.280 mixer and UH one is their polar opposites of each other, 0:20:28.640 --> 0:20:33.240 and So the the mixer adds in the lower frequency 0:20:33.440 --> 0:20:38.560 together with the frequency that came in through the receiver, 0:20:39.560 --> 0:20:44.359 and that is what it sends out to the intermediate 0:20:44.680 --> 0:20:49.840 frequency amplifier. So we've gone PREAMPTI mixer. Mixer pulls in 0:20:49.840 --> 0:20:53.919 a second frequency from the oscillator. The oscillator frequency, the 0:20:53.960 --> 0:20:57.199 lower one, gets combined with the incoming frequency that is 0:20:57.240 --> 0:21:00.920 then sent to the intermediate frequency amplifier or I of amplifier, 0:21:01.960 --> 0:21:05.280 and that just process that sesses that signal and amplifies it. 0:21:05.359 --> 0:21:07.679 We've talked about amplifiers before in this podcast, so I'm 0:21:07.720 --> 0:21:10.360 not going to get into that. Uh. And then this 0:21:10.560 --> 0:21:14.160 this stronger signal from the I F amplifier gets sent 0:21:14.240 --> 0:21:17.240 to Well, now we've got to go to the square 0:21:17.280 --> 0:21:22.159 law detectors and the d C processors because we have 0:21:22.320 --> 0:21:26.040 to create a d C a direct current in order 0:21:26.119 --> 0:21:30.520 for that to go to a recording device. So this 0:21:30.600 --> 0:21:34.120 converts the frequency from the amplifier to direct current signals, 0:21:34.359 --> 0:21:36.920 and it smooths out the signals to make them easier 0:21:36.960 --> 0:21:39.960 to measure because they fluctuate quite a bit. Even as 0:21:40.000 --> 0:21:41.879 direct current, they tend to fluctuate. So the way they 0:21:41.880 --> 0:21:45.280 do this is they use capacitors. And if you recall 0:21:45.320 --> 0:21:50.760 we've talked about capacitors before too, capacitors store up electricity 0:21:50.840 --> 0:21:53.680 and then release it all at once, right there. They're 0:21:53.760 --> 0:21:55.840 kind of like a battery that it can store electricity, 0:21:55.880 --> 0:21:59.200 but unlike a battery, it is and it releases all 0:21:59.200 --> 0:22:03.080 the electricity, doesn't do a constant flow. This, by the way, 0:22:03.240 --> 0:22:06.199 is the reason why it's a bad idea to fiddle 0:22:06.240 --> 0:22:09.040 around with electronics you don't know a lot about, including 0:22:09.080 --> 0:22:13.760 things like televisions and computers, because they have capacitors in 0:22:13.800 --> 0:22:16.840 them that can store high amounts of electricity that are 0:22:16.960 --> 0:22:21.480 potentially deadly. So, especially things like computers and televisions, you 0:22:21.560 --> 0:22:24.560 don't wanna, you know, just knock a hole in one, 0:22:24.800 --> 0:22:27.439 or you know, I've seen like videos, if you've ever 0:22:27.480 --> 0:22:29.960 seen a video of someone who who accellently breaks the television, 0:22:29.960 --> 0:22:32.120 you see a spark go off. That's a capacitor that's 0:22:32.200 --> 0:22:36.200 that's discharging, and those can be very dangerous. So anyway, 0:22:36.960 --> 0:22:38.879 in this case, the capacitors are used to kind of 0:22:38.920 --> 0:22:42.199 smooth out those signals. I have read an interesting analogy 0:22:42.440 --> 0:22:46.840 which said, imagine that you have a water hose and 0:22:46.960 --> 0:22:49.720 water is moving through the hose, but the pressure keeps changing, 0:22:50.040 --> 0:22:52.320 so the water sometimes it's flowing out very quickly and 0:22:52.320 --> 0:22:56.880 sometimes it's sputtering out. Okay. Uh. In the case of 0:22:56.960 --> 0:23:00.680 this detecting radio frequencies, you want to a steady um 0:23:01.160 --> 0:23:04.159 flow so that you can measure it properly. So what 0:23:04.280 --> 0:23:06.919 if you were to instead of just measure the measuring 0:23:06.960 --> 0:23:09.679 the water that comes out of the hose, you you 0:23:09.960 --> 0:23:12.639 direct the hose towards a bucket, okay, And at the 0:23:12.680 --> 0:23:15.480 base of the bucket there's a spigot that you can 0:23:15.520 --> 0:23:17.720 open up. Well, if you open up the spigot on 0:23:17.760 --> 0:23:19.440 the bucket, water is going to flow out at a 0:23:19.520 --> 0:23:22.479 much more steady rate than it's flowing out of the hose. 0:23:23.200 --> 0:23:25.240 That's the kind of idea here with the capacitor, and 0:23:25.280 --> 0:23:27.600 that it's to try and smooth out that signal and 0:23:27.600 --> 0:23:29.640 make it easier to record. And then finally you've got 0:23:29.640 --> 0:23:32.960 the actual recording device. Now, in the old days, the 0:23:33.000 --> 0:23:37.159 recording device was a an old man who said, what 0:23:37.359 --> 0:23:40.359 was that. No, it was actually a pen attached to 0:23:40.720 --> 0:23:44.399 a a movable arm and some paper that was pulled 0:23:44.440 --> 0:23:47.800 across and then the movable arm would would move depending 0:23:47.880 --> 0:23:52.360 upon changes in voltage and so it's very similar to uh, 0:23:52.560 --> 0:23:56.480 earthquake detecting equipment. We've talked about seismological equipment in the 0:23:56.520 --> 0:23:59.400 past where you see that or even if you think 0:23:59.440 --> 0:24:03.800 also similar things lie detectors. That's exactly what I was thinking. 0:24:04.000 --> 0:24:06.560