Get in touch with technology with tech Stuff from how stuff works dot com. Hey there, and welcome to tech Stuff. I am your host executive producer, John than Strick, London. I love all things tech. It is time for another classic episode of tech Stuff, and today we're going to visit an episode that we originally published on January two thousand twelve. Chris Pallette my co host at the time, and I decided to look into the topic of radio telescopes. I talked about these not too long ago when I did a series about DARPA. Well, now we're gonna have a full episode dedicated to the topic, and I hope you guys enjoy. So. Um, before we get started, we're gonna do something we haven't done a little while. Yeah, we're gonna listen to a little listener mail. This listener mail comes from me who says I love your podcast and have enjoyed listening to your incifle and quirky explanations immensely. I tried to search through the past podcast to see if you have done one on radio telescopes, to no avail, So I hope I didn't just miss it. It seems to me that radio telescopes are being used frequently to learn about this and study the far reaches of the galaxy and beyond. And that's pretty darn cool, so it'd be neat to learn more about how they work. Thanks and thanks for the show, Minka. Well you're welcome, Inga. I just wanted to say you're welcome. All right, So now we're moving on to our topic, the Smurfs. No, no, we're gonna talk about radio telescopes. Good, yeah, we sort of. Well, we've talked about things that relate to radio telescopes like radio and stead yes, and steady set, which does very much relate to radio telescopes. Well, what do radio telescopes do? Why are they important? Well, it's funny that you should mention that, Yeah, because they're I my notes crashed, so I don't know what I'm talking about. Your notes crash. No, I'm not. I'm just kidding. They're still up. He can't see my computer from where he sits. Yes, because he's sitting directly across from me. Yes. See. If if you ever wondered if that was true or not, it is. Yeah, um no, it's it's actually using it's unlike a typical visual telescope, which uses lenses and your eyeball, and you look through it and you look for stuff on the other side and base it directs light which is in the visible spectrum of the electromagnetic frequency. Yes, to our to our eyeballs ultimately right right, But and again another drastic oversimplification of the parts. But a radio telescope is actually monitoring different parts of the electromagnetic frequency. Yeah. Yeah, it's good looking at a completely different spectrum. So this is part of the spectrum that is not visible to the naked eye. So we are using these telescopes to measure um radio frequency variations that come from outer space. And it turns out that lots of stuff out there generates radio frequencies, right, So things like quasars, pulsars, galaxies, uh, distant stars, these sort of things can generate electro magnetic radiation and in the form of radio frequencies. And sometimes these are are objects that we can't detect visually, but we can detect them if we have a sensitive enough tool that can can detect and measure radio frequencies. So that's really what a radio telescope is all about. And it's kind of tricky picking up radio frequencies from outer space because only certain the actual band of frequencies or wavelengths I should say, the band of wavelengths that exist within the electromatic spect magnetic spectrum that are radio frequency waves. It's pretty broad. Yeah, about ten meters and to one millimeter. That's a pretty good size. Yeah, you can actually get radio waves that are even longer than that, like the size of football fields. But here's the thing is that the Earth has a level of the atmosphere called the ionosphere. Now, the iono sphere is uh, it's kind of funky. So you guys probably have heard us talk about ions before, you know. That's when we're talking about uh, atoms that have either gained or lost an electron. And if you ionize something, that means you've got some free electrons roaming around in it. So like an ionized gas or a plasma can actually hold carry an electric charge. Right, Yes, Why are you smiling at me just because I saw a whole bunch of people going WHOA free electrons? Yeah? Sorr, there're so expensive. Otherwise that's true. Have you seen my electric bill? Anyway? So you have the ionosphere, whether these free roaming electrons out there, and uh, and it kind of acts as a bit of a shield or reflector in in some ways, and so radio waves of a certain way wave length cannot pass through the ionosphere. Essentially, anything that's ten meters are longer, the ionosphere is opaque to those. That's why you can actually broadcast certain long wavelength radio waves uh and bank them off the ionosphere because it won't pass through. Now, when you start getting shorter than a ten meter wave length, you have radio waves that can pass through the ionosphere. But if it's longer than twenty centimeters, which is about one point five gig hurts in frequency when you talk about these, If it's longer than twenty centimeters, you start to have distortion as it passes through the ionosphere. It's called scintillation. And this isn't that different from the way when we look up into the sky and we see stars twinkling. That's sort of the same sort of thing we talked about being scintillating, same kind of idea, except in this case, you know, that's we're talking about the visual spectrum there, but here, Yeah, the twenty centimeters are longer, you run into that problem. And so that's not entirely useful for measurement purposes. So radio telescopes tend to focus on pun intended Uh, wavelengths that are between one centimeter and twenty centimeters in length tend to Now there are some variations. And also if you were to have a radio telescope, say in orbit where it's you know, you don't have the ionosphere as a in play. Um, that's a different story. But ground based radio telescopes kind of had to play within these rules because the way the ionosphere works. One of the nice things though about the radio telescope is that, uh, those frequencies generally come through pretty clearly. So uh, putting one of the ground based radio telescopes in orbit really wouldn't improve its ability to detect signals um, at least based on my research, and not not within anything that's within those wavelengths. Yeah. Actually it's it's a little tricky to detect that stuff anyway, because we're talking about really we signals. I mean, by the time they reached the Earth, that these signals are not very strong at all. In fact, one one reference I I looked at said that that if you were to add up all the energy that every radio telescope on Earth had been subjected to since they were built, it still would not equal the energy would find in the snowflake. Yeah, that's pretty impressive. Act grant that snowflake is the size of Detroit. No, I'm kidding, I'm kidding. Typical snowflake. No. Uh. And it is also worthwhile to note, especially before anyone writes in um, that radio telescopes do have to be placed away from population centers in general, uh, to some degree to because there is earthly interference. Yeah, there's terrestrial radio interference that you have to try and minimize as much as possible. Otherwise it's just so much noise that you're not going to even find any signal out there, right right, So, um, Yeah, it has its it has its good points and in its ad points because of the frequencies, it's able to monitor. And it's a good point too that you uh, you mentioned the from the very first because these these devices, I mean, I'm I imagine people you know, have a good idea what radio telescopes look like. I mean, we've all seen satellite dishes, and to some degree that's more or less what they look like. In fact, you may have seen pictures of them, but um that I think gives it the the sort of feeling that it's a fairly recent thing. And in fact, um it was somebody in uh nine thirty three who who figured out that, um, there was, uh, there were radio frequencies coming from extraterrestrial bodies. Someone at of course Bell telephone laboratories, laboratories. You always do that. I can't fight it, that I can't fight this feeling anymore. I can't. But yes, so you're talking about Carl Carl Jansky. Carl Jansky, Yes, Uh, he he built the first antenna that could be used as a radio telescope back in ninety one, but it would take a couple of years to really figure out, uh, the fact that you could use this to to explore the heavens above. Because when he built his radio frequency detector, it was not to act as a radio telescope. It was meant to detect static that could potentially interfere with radio telephone services. Right, So he was he was working literally on a project for Bell. Yeah, and what happened was he discovered that there was this interesting hissing noise he was picking up, and that was hitting a cycle. The hissing noise would would occur at a certain time every day, and the cycle hit, well, not every day, the cycle hit every twenty three hours and fifty six minutes, And once he removed the snake from the line, he realized there was something else hit. He figured out that the twenty three hours of fifty six minutes was essentially the period that it takes for if you've if you've got a fixed point on the sky for the you to come background so that you're pointing at that same object and come up again later. Eventually he determined that this was the the origin of this radio frequency was otherworldly, so it was coming from outside the Earth, and that it was in fact coming from somewhere in the Sagittarius constellation far out. Yeah, so guys, I'm picking up a signal from outer space. No, I'm sorry, it's not from outer space. It's just from just outside the room. It's Tari, She's telling me that we need to take a break to thank our sponsor. So it would take a few more years before you saw anyone build a parabolic antenna, which is what Chris was talking about earlier, the dish style antenna. Those are not the only kind of antennas that are used in radio telescopes. It's probably, i would argue, probably the most iconic and the most common that we we see. But there are other types of antenna as, including dipole antenna's, cylindrical parabolics, which are they kind of look like a trough. Uh there are the yaggy antenna's, which are um not little guys who teach you how to use kung fu kara, I should say, their horn antennas their mills crosses that kind of STU mills crosses telescope um. Various ways of doing this, but the principle is essentially the same. It's to try and gather to detect together as much as radio frequency UM radiation as possible. And usually there are several reflectors involved that reflect radio frequencies to a focal point that can then send the signal to receiver and then from there it gets amplified. And we'll go through that process in a little bit. But uh so in and the parabolic style of of antenna, this is why you have that big dish. The dish part is actually reflecting frequencies so that they all are directed to a single focal point and that's usually called the feed. That's usually a small antenna called the feed that uh as often called the feed horn, that will collect the signal and send it to the receiver. Yes, so these these radio frequencies are, like we said, generated by lots of different stuff out there in the in the in space. Um so. But the problem is that the they're so so delicate. There's so such tiny little frequencies that you have to really control for the noise element, not just by trying to isolate the antenna of it, but also by making sure the material you've used in your antenna array is the right kind of stuff, because they're pretty sense of things, and also the amount of information you can get is very much connected to the side of your antenna. Bigger antennas are able to provide a higher resolution image. It's kind of a weird word to say, because we're not talking about visible light necessarily, but an image of what it is you're looking at. Right. So, so the larger the better in general. But if you start building so large that the material itself is heavy enough to warp because it's it's it's so heavy that the structure itself can't maintain a specific shape, well, then you're not reflecting the radio frequencies to that focal point anymore, you've warped it out of shape. So you have to build it out of special materials and you have to plan for Okay, well, we know that by designing an antenna of this size, this particular warping is going to occur, so we have to factor that into the design so that the warping actually ends up helping rather than hurting. And usually you do that by adding a second reflector that is that's movable, so you can have a second reflector actually um position in such a way where the distortion from the main reflector hit the second reflector, which then reflects it back to the focal point. So it gets a little complicated. In fact, there are two main types of secondary reflectors. There's the Cassegrain focus, which is a reflector that's in front of the main antenna or the main reflector, i should say. And then there's another one if you have it in the back. It's called Grigoryan focus, and it chants a lot. At a feeling you were going to say that, yeah, there was a pretty good chance. Uh yeah, it's possible. Um Now, given what Johnathan was just talking about, giving the materials and and the uh, there are a lot of things that that can affect uh, the efficiency of a radio telescope, including heat, because the materials will expand or contract, wind, the surface of the material itself, the surface of the material itself. Um. But other than that, I mean, once you take all these things into account, it is theoretically possible to build as larger radio telescope as you possibly can. There's really no limit to the size other than the fact that you're going to have to take things like gravity and temperature and things like that into a tensile strength. But conceivably, if you could build one that's three times the size of Earth, it would work. Yeah. But that and that's fascinating because it's it's not it doesn't have to be a particularly large or particularly small device. It just you know, you can pick up more with it. And a lot of a lot of radio telescopes are actually telescope like antenna arrays, So it's not just one antenna's several antennas working together in order if you to gather this information work, that's what I say. And and that that helps you create a larger radio telescope just but you know, you're adding extra elements, and it means that you sort of get around part of the problem, which is, you know, building just an enormous single antenna. You can do an array of antennas. There are different limitations on this as well. Um. So, the signal that you're picking up with this radio telescope is really really weak, So in order for you to have it, uh and to to transmit first you have to you have to transfer the radio frequency information by by changing it into electricity. But because the frequency signal is so weak, the electric current would be pretty pathetic. You would not be able to measure it just by converting it right from radio frequency to electricity without amplifying it in some way. So typically a radio telescope will then have a pre amplifier. So you musicians out there and and and radio folks, you know, you're probably pretty familiar with the idea of a pre amplifier. Microphones usually have a pre amplifier that kind of thing. Um So, a pre amplifier is really just a a way of boosting a signal a certain amount before it gets truly amplified, uh for the final use of whatever that signal is gonna be, whether it's in the audio industry, or in this case, the measuring the celestial bodies. Yeah, I was gonna say that they don't necessarily usually have them anyway. Um, well, that's that's fair, but it does. It does assist, uh, and in picking up these weak signals, that's for sure. Yeah. And so the kind that tends to be used in radio telescopes are called low noise amplifiers because we're talking about such small, very very quiet signals. And so, boy, I'm glad didn't do the old listener mail beginning because then with all this it would have proably blown everybody's ears out. So the the these l n A pre amplifiers take these um signals and then they boost them. Now here's the thing. Any sort of interference at this point could really compromise the measurements you're making. So that includes molecular movement of the pre amp. So the fact that you know, everything in matter is made up of molecules, and these molecules move even in solid objects, right, yes, so they in a in big radio telescope facilities, things like the professional ones that you would find in say NASA, they tend to have to cool down the pre amplifier to reduce molecular movement as much as possible, and usually to around ten kelvin. It's pretty cold. Pretty cold, yeah, zero kelvin means no molecular movement. That's what like the deepest reaches of space would be is zero kelvin. So ten kelvin's pretty cold. They tend to use liquid helium to cool down the this this device low enough so that it reduces the chance for it to contribute noise to this signal. All right. From there, the signal moves into a mixer, yes, where it has a party and networks with people and not. Oh, should have taken different notes. Okay, well I'll just work from memory here then, um no, a mixer. The mixer's purpose is to change the frequency of the signal. Now, the signals are very high frequency and uh, and it turns out that it's easier to amplify lower frequencies. It's possible to amplify higher frequencies, but in general, it takes less uh effort to amplify the lower frequency signals. And if it's kept it it's high frequency and you're just you're you're working with the frequency at that and it's native frequency. There's the chance they'll travel back up the antenna and create feedback. It's not dissimilar to what would happen with a microphone too close to a speaker, where you get that wonderful sound. That's wonderful. Now you're you're probably more familiar with it than I am with your rock and roll lifestyle and all. So then what happens is the mixer mixes this frequency, not just it doesn't just lower. The way it lowers this frequency is it mixes the frequency with a frequency generated by an oscillator. Okay, so the oscillator creates two frequencies that are both sent into the mixer, and uh one is there the polar opposites of each other. And so the the mixer adds in the lower frequency together with the frequency that came in through the receiver, and that is what it sends out to the intermediate frequency amplifier. So we've gone PREAMPTI mixer. Mixer pulls in a second frequency from the oscillator, the oscillator frequency, the lower one gets combined with the incoming frequency that is then sent to the intermediate frequency amplifier or i F amplifier. And that just process that says is that signal and amplifies it. And we've talked about amplifiers before in this podcast, so I'm not going to get into that. Uh. And then this, this stronger signal from the i F amplifier gets sent to Well, now we've got to go to the square law detectors and the d C processors because we have to create a d see a direct current in order for that to go to a recording device. So this converts the frequency from the amplifier to direct current signals, and it smooths out the signals to make them easier to measure because they fluctuate quite a bit. Even as direct current, they tend to fluctuate. So the way they do this is they use capacitors. And if you recall we've talked about capacitors before too, capacitors store up electricity and then release it all at once, right. They're they're kind of like a battery that it can store electricity, but unlike a battery, it is and it releases all the electricity. It doesn't do a constant flow. This, by the way, is the reason why it's a bad idea to fiddle around with electronics. You don't know a lot about, including things like televisions and computers because they have capacitors in them that can store high amounts of electricity that are potentially deadly. So especially things like computers and televisions, you don't want to, you know, just knock a hole in one or you know. I have seen like videos. If you've ever seen a video of someone who who excellently breaks the television, you see a spark go off. That's a capacitor that's that's discharging, and those can be very dangerous. Chris and I have a little bit more to say about radio telescopes, but before we do, let's take another quick break to thank our sponsor. I have read an interesting analogy which said, imagine that you have a water hose and water is moving through the hose, but the pressure keeps changing, so the water sometimes it's flowing out very quickly and sometimes it's sputtering out. Okay uh. In the case of this detecting radio frequencies, you want to a steady um flow so that you can measure it properly. So what if you were to instead of just measure the measuring the water that comes out of the hose, you you direct the hose towards a bucket, okay, and at the base of the bucket there's this big it that you can open up. Well, if you open up the spin on the bucket, water is going to flow out at a much more steady rate than it's flowing out of the hose. That's the kind of idea here with the capacitor, and that it's to try and smooth out that signal and make it easier to record, and then finally you've got the actual recording device. Now, in the old days, the recording device was a an old man who said what is that? No, it was actually a pen attached to a a movable arm and some paper that was pulled across and then the movable arm would would move depending upon changes in voltage. And so it's very similar to uh earthquake detecting equipment. We talked about seismological equipment in the past where you see that or even if you think also a similar things light detectors, that's what I was saying, polygraphs where they have the little the little pen that scratches back and forth across the papers, the papers going by, similar kind of thing. Um Now in October fourteen, yeah, so we when did you go super nova. Um. No, so this in this case instead, what's doing is it's actually uh, modern ones don't tend to use this anymore. They tend to actually send the data directly to a computer where it gets recorded and you read out the information on a computer screen, as opposed to looking at a physical representation scratched out in pen um. That's generally how the radio telescope works from start to finish. So it's pretty interesting stuff. It's a little complex, I would say, yeah, yeah, Um. One of the things that uh, we were talking about two Jonathan mentioned, um the Jansky's experiments where he was he would note that the interference would come around at a certain period of time. UM. One of the prime places to put a radio telescope is near the equator because it is really good. Um. It's a really good place to get an accurate depiction as the Earth rotates, um, and it can it can identify sources of radio information coming from space very clearly. UM. Unfortunately, it's a rather expensive place to try to build a radio telescopes, and that's one of the reasons why they can be found in many different places around the world. But yea closer to the equator tends to be better just for the you know, the quality of information you can get from this. UM and and uh, we've actually started using radio telescopes to kind of map out the celestial bodies around us, even ones that are not visible to the naked eye. And it's been very useful for astronomers. And there's still there's still even you know, uh, amateur astronomers who use radio telescopes. This this it's not just the realm of massive scientific organizations like NASA, although I mean those are the ones that you know, if you look up the pictures online, you tend to see the really larger arrays or really large antennas that belonged to these major organizations. Now, a radio telescope is able to detect things celestial bodies and sky by their angular resolution. UM. Basically it it really is contingent on the wavelengths that it is able to detect. So that's one of the reasons why UM, a radio telescope does need to be large. UM. Yeah, if you you could build a small one, but it wouldn't be nearly as functional as a larger one. Basically, the larger radio telescope is the greater it's angular resolution. Um. But um that that's basically uh, that's basically what it is. What what it's using. In terms of how you would measure the effectiveness of a radio telescope. Yeah, if you you know, if you had like a backyard telescope visual telescope, the resolution you would get on that is equivalent to what you would get with a huge radio telescope. The solution on a radio telescope is proportional to its size. So um, yeah, you've gotta have a big one if you're going to have any any real precise resolution. And again we're not, you know, it's it's a little weird because it's hard to think of resolution in terms of something other than visible light because that's what we're mostly familiar with. But but yes, it's it still applies in this case. Yep, yep, um and radio basically, radio astronomers have been able to detect all kinds of different molecules in space too. Um, you can. You might be surprised to learn. I was a little surprised to learn that radio radio astronomers were able to identify carbon dioxide, water, formaldehyde, ethyl alcohol, methanol, ammonia, UM and all kinds of other different kinds of just that kinds twice of compounds out in space UM and and to use the radio telescope in that way, I mean it's you can get a lot of information. And that's actually uh sort of ties back into the SETI project because the if if you haven't listened to that particular podcast or are unfamiliar with the project, Basically, UM astronomers were collecting large amounts of data from the radio telescope. They were using UM for their project, and the thing is their computers couldn't analyze it all at one time. They were collecting so much that it was just stacking up essentially, not literally but to figurative. To create an analogy, We've talked about in the past, how on YouTube, users are uploading forty eight hours of content every every minute. So it'd be like telling one person to watch everything that's on YouTube. You've got you've got a growing amount of content that you're never going to catch up to and only so much ability to consume it. So same sort of thing. In this case, we're talking about generating uh, incredible amounts of data and having a limited ability to actually analyze the information. So what they would do was to break it down and use it in a distributed computing project, which they were calling SETI at Home, and the idea being that people take a slice of information, allow their computers to work it out using a specially designed program, and send it back to the astronomers so that they could evaluate it and added to the project. And uh, you know, it's just sort of a kind of a neat way to to get into helping out with the project like that. But that's that's one of the problems, a good problem to have with with radio astronomy is that these uh large radio telescopes can couldn't collect an awful lot of data. Yeah, and so we might use them to discover things like quay stars re pulsars that we had never seen before, or even detect the presence of a galaxy that before this point we just didn't know existed. Now. CETI, of course, was really looking for any sort of signals that might indicate a pattern or uh a possible um well possible hint that there's some sort of other intelligent life out there that's generating these signals, not not just some natural phenomenon. Do do do do well? Um and radio. Radio telescopes can also detect information about near celestial bodies as well. The surface. For the Moon, we knew it was sort of sandy before people actually landed there because astronomers had used radio telescopes to, uh to get signals from the Moon and learn, you know, what it was like. They're also Venus, you know, is shrouded by clouds, but astronomers are able to learn more about the surface by using radio telescopes and radar to get an idea of what these the actual planet surfaces. Well, they've also used it to observe the storms on Jupiter, so that's kind of interesting too, Like they just looked at the weather report for you right today today it's gonna be a big gas. It sounds like my never mind never yes, let's it's most like that, Okay, but yeah, I think, uh, it's it's an interesting topic. It's really and it's one honestly I did not know very much about before we started researching this podcast. I agree with you. I mean I knew of it, I knew it existed, but I didn't really understand what it was doing or how it did it. And it is pretty cool. I mean, it just shows me that radio is way cooler than I ever imagined when I you know, so there you turn a radio on. That's that's the extent of your Maybe you play with a walkie talkie, but that's about it as far as radio goes. And then the more you look into it, the more you're like, wow, this is really phenomenal stuff. Tesla was onto something. It's gonna say you probably had a patent for that. Yeah, I probably did. And then never mind, I'm not gonna go into another Tesla rent. Okay. Then all right, Well that wraps up this discussion. Minka, thank you so much for writing in and jesting that that was a really cool topic for us to tackle. And that wraps up another classic episode of tech Stuff. I hope you guys enjoyed it. It's always a joy to look into tech with Chris. I hope he's doing well. I cannot get him back on the show because he's got better things to do than to sit across the table and talk into a microphone with me. He's doing important work like making people way way smarter. So, Chris, if you're listening, thanks so much. There's a joy to work with you, and it's always fun to listen back to these old episodes. If you want to reach out and suggest new topics for me to cover in future episodes of tech Stuff, go visit our website, it is tech stuff podcast dot com. There you're gonna find all the different ways to reach out to me and to let me know about your suggestions for the show. I greatly appreciate it. Don't forget. You can visit our merchandise store over at t public dot com slash tech stuff. Go check that out. Any purchase you make goes to help the show. We greatly appreciate it, and I'll talk to you again really soon for more on this and thousands of other topics. Is that how stuff Works dot com

Get in touch with technology with tech Stuff from how stuff works dot com. Hey there, and welcome to tech Stuff. I am your host executive producer, John than Strick, London. I love all things tech. It is time for another classic episode of tech Stuff, and today we're going to visit an episode that we originally published on January two thousand twelve. Chris Pallette my co host at the time, and I decided to look into the topic of radio telescopes. I talked about these not too long ago when I did a series about DARPA. Well, now we're gonna have a full episode dedicated to the topic, and I hope you guys enjoy. So. Um, before we get started, we're gonna do something we haven't done a little while. Yeah, we're gonna listen to a little listener mail. This listener mail comes from me who says I love your podcast and have enjoyed listening to your incifle and quirky explanations immensely. I tried to search through the past podcast to see if you have done one on radio telescopes, to no avail, So I hope I didn't just miss it. It seems to me that radio telescopes are being used frequently to learn about this and study the far reaches of the galaxy and beyond. And that's pretty darn cool, so it'd be neat to learn more about how they work. Thanks and thanks for the show, Minka. Well you're welcome, Inga. I just wanted to say you're welcome. All right, So now we're moving on to our topic, the Smurfs. No, no, we're gonna talk about radio telescopes. Good, yeah, we sort of. Well, we've talked about things that relate to radio telescopes like radio and stead yes, and steady set, which does very much relate to radio telescopes. Well, what do radio telescopes do? Why are they important? Well, it's funny that you should mention that, Yeah, because they're I my notes crashed, so I don't know what I'm talking about. Your notes crash. No, I'm not. I'm just kidding. They're still up. He can't see my computer from where he sits. Yes, because he's sitting directly across from me. Yes. See. If if you ever wondered if that was true or not, it is. Yeah, um no, it's it's actually using it's unlike a typical visual telescope, which uses lenses and your eyeball, and you look through it and you look for stuff on the other side and base it directs light which is in the visible spectrum of the electromagnetic frequency. Yes, to our to our eyeballs ultimately right right, But and again another drastic oversimplification of the parts. But a radio telescope is actually monitoring different parts of the electromagnetic frequency. Yeah. Yeah, it's good looking at a completely different spectrum. So this is part of the spectrum that is not visible to the naked eye. So we are using these telescopes to measure um radio frequency variations that come from outer space. And it turns out that lots of stuff out there generates radio frequencies, right, So things like quasars, pulsars, galaxies, uh, distant stars, these sort of things can generate electro magnetic radiation and in the form of radio frequencies. And sometimes these are are objects that we can't detect visually, but we can detect them if we have a sensitive enough tool that can can detect and measure radio frequencies. So that's really what a radio telescope is all about. And it's kind of tricky picking up radio frequencies from outer space because only certain the actual band of frequencies or wavelengths I should say, the band of wavelengths that exist within the electromatic spect magnetic spectrum that are radio frequency waves. It's pretty broad. Yeah, about ten meters and to one millimeter. That's a pretty good size. Yeah, you can actually get radio waves that are even longer than that, like the size of football fields. But here's the thing is that the Earth has a level of the atmosphere called the ionosphere. Now, the iono sphere is uh, it's kind of funky. So you guys probably have heard us talk about ions before, you know. That's when we're talking about uh, atoms that have either gained or lost an electron. And if you ionize something, that means you've got some free electrons roaming around in it. So like an ionized gas or a plasma can actually hold carry an electric charge. Right, Yes, Why are you smiling at me just because I saw a whole bunch of people going WHOA free electrons? Yeah? Sorr, there're so expensive. Otherwise that's true. Have you seen my electric bill? Anyway? So you have the ionosphere, whether these free roaming electrons out there, and uh, and it kind of acts as a bit of a shield or reflector in in some ways, and so radio waves of a certain way wave length cannot pass through the ionosphere. Essentially, anything that's ten meters are longer, the ionosphere is opaque to those. That's why you can actually broadcast certain long wavelength radio waves uh and bank them off the ionosphere because it won't pass through. Now, when you start getting shorter than a ten meter wave length, you have radio waves that can pass through the ionosphere. But if it's longer than twenty centimeters, which is about one point five gig hurts in frequency when you talk about these, If it's longer than twenty centimeters, you start to have distortion as it passes through the ionosphere. It's called scintillation. And this isn't that different from the way when we look up into the sky and we see stars twinkling. That's sort of the same sort of thing we talked about being scintillating, same kind of idea, except in this case, you know, that's we're talking about the visual spectrum there, but here, Yeah, the twenty centimeters are longer, you run into that problem. And so that's not entirely useful for measurement purposes. So radio telescopes tend to focus on pun intended Uh, wavelengths that are between one centimeter and twenty centimeters in length tend to Now there are some variations. And also if you were to have a radio telescope, say in orbit where it's you know, you don't have the ionosphere as a in play. Um, that's a different story. But ground based radio telescopes kind of had to play within these rules because the way the ionosphere works. One of the nice things though about the radio telescope is that, uh, those frequencies generally come through pretty clearly. So uh, putting one of the ground based radio telescopes in orbit really wouldn't improve its ability to detect signals um, at least based on my research, and not not within anything that's within those wavelengths. Yeah. Actually it's it's a little tricky to detect that stuff anyway, because we're talking about really we signals. I mean, by the time they reached the Earth, that these signals are not very strong at all. In fact, one one reference I I looked at said that that if you were to add up all the energy that every radio telescope on Earth had been subjected to since they were built, it still would not equal the energy would find in the snowflake. Yeah, that's pretty impressive. Act grant that snowflake is the size of Detroit. No, I'm kidding, I'm kidding. Typical snowflake. No. Uh. And it is also worthwhile to note, especially before anyone writes in um, that radio telescopes do have to be placed away from population centers in general, uh, to some degree to because there is earthly interference. Yeah, there's terrestrial radio interference that you have to try and minimize as much as possible. Otherwise it's just so much noise that you're not going to even find any signal out there, right right, So, um, Yeah, it has its it has its good points and in its ad points because of the frequencies, it's able to monitor. And it's a good point too that you uh, you mentioned the from the very first because these these devices, I mean, I'm I imagine people you know, have a good idea what radio telescopes look like. I mean, we've all seen satellite dishes, and to some degree that's more or less what they look like. In fact, you may have seen pictures of them, but um that I think gives it the the sort of feeling that it's a fairly recent thing. And in fact, um it was somebody in uh nine thirty three who who figured out that, um, there was, uh, there were radio frequencies coming from extraterrestrial bodies. Someone at of course Bell telephone laboratories, laboratories. You always do that. I can't fight it, that I can't fight this feeling anymore. I can't. But yes, so you're talking about Carl Carl Jansky. Carl Jansky, Yes, Uh, he he built the first antenna that could be used as a radio telescope back in ninety one, but it would take a couple of years to really figure out, uh, the fact that you could use this to to explore the heavens above. Because when he built his radio frequency detector, it was not to act as a radio telescope. It was meant to detect static that could potentially interfere with radio telephone services. Right, So he was he was working literally on a project for Bell. Yeah, and what happened was he discovered that there was this interesting hissing noise he was picking up, and that was hitting a cycle. The hissing noise would would occur at a certain time every day, and the cycle hit, well, not every day, the cycle hit every twenty three hours and fifty six minutes, And once he removed the snake from the line, he realized there was something else hit. He figured out that the twenty three hours of fifty six minutes was essentially the period that it takes for if you've if you've got a fixed point on the sky for the you to come background so that you're pointing at that same object and come up again later. Eventually he determined that this was the the origin of this radio frequency was otherworldly, so it was coming from outside the Earth, and that it was in fact coming from somewhere in the Sagittarius constellation far out. Yeah, so guys, I'm picking up a signal from outer space. No, I'm sorry, it's not from outer space. It's just from just outside the room. It's Tari, She's telling me that we need to take a break to thank our sponsor. So it would take a few more years before you saw anyone build a parabolic antenna, which is what Chris was talking about earlier, the dish style antenna. Those are not the only kind of antennas that are used in radio telescopes. It's probably, i would argue, probably the most iconic and the most common that we we see. But there are other types of antenna as, including dipole antenna's, cylindrical parabolics, which are they kind of look like a trough. Uh there are the yaggy antenna's, which are um not little guys who teach you how to use kung fu kara, I should say, their horn antennas their mills crosses that kind of STU mills crosses telescope um. Various ways of doing this, but the principle is essentially the same. It's to try and gather to detect together as much as radio frequency UM radiation as possible. And usually there are several reflectors involved that reflect radio frequencies to a focal point that can then send the signal to receiver and then from there it gets amplified. And we'll go through that process in a little bit. But uh so in and the parabolic style of of antenna, this is why you have that big dish. The dish part is actually reflecting frequencies so that they all are directed to a single focal point and that's usually called the feed. That's usually a small antenna called the feed that uh as often called the feed horn, that will collect the signal and send it to the receiver. Yes, so these these radio frequencies are, like we said, generated by lots of different stuff out there in the in the in space. Um so. But the problem is that the they're so so delicate. There's so such tiny little frequencies that you have to really control for the noise element, not just by trying to isolate the antenna of it, but also by making sure the material you've used in your antenna array is the right kind of stuff, because they're pretty sense of things, and also the amount of information you can get is very much connected to the side of your antenna. Bigger antennas are able to provide a higher resolution image. It's kind of a weird word to say, because we're not talking about visible light necessarily, but an image of what it is you're looking at. Right. So, so the larger the better in general. But if you start building so large that the material itself is heavy enough to warp because it's it's it's so heavy that the structure itself can't maintain a specific shape, well, then you're not reflecting the radio frequencies to that focal point anymore, you've warped it out of shape. So you have to build it out of special materials and you have to plan for Okay, well, we know that by designing an antenna of this size, this particular warping is going to occur, so we have to factor that into the design so that the warping actually ends up helping rather than hurting. And usually you do that by adding a second reflector that is that's movable, so you can have a second reflector actually um position in such a way where the distortion from the main reflector hit the second reflector, which then reflects it back to the focal point. So it gets a little complicated. In fact, there are two main types of secondary reflectors. There's the Cassegrain focus, which is a reflector that's in front of the main antenna or the main reflector, i should say. And then there's another one if you have it in the back. It's called Grigoryan focus, and it chants a lot. At a feeling you were going to say that, yeah, there was a pretty good chance. Uh yeah, it's possible. Um Now, given what Johnathan was just talking about, giving the materials and and the uh, there are a lot of things that that can affect uh, the efficiency of a radio telescope, including heat, because the materials will expand or contract, wind, the surface of the material itself, the surface of the material itself. Um. But other than that, I mean, once you take all these things into account, it is theoretically possible to build as larger radio telescope as you possibly can. There's really no limit to the size other than the fact that you're going to have to take things like gravity and temperature and things like that into a tensile strength. But conceivably, if you could build one that's three times the size of Earth, it would work. Yeah. But that and that's fascinating because it's it's not it doesn't have to be a particularly large or particularly small device. It just you know, you can pick up more with it. And a lot of a lot of radio telescopes are actually telescope like antenna arrays, So it's not just one antenna's several antennas working together in order if you to gather this information work, that's what I say. And and that that helps you create a larger radio telescope just but you know, you're adding extra elements, and it means that you sort of get around part of the problem, which is, you know, building just an enormous single antenna. You can do an array of antennas. There are different limitations on this as well. Um. So, the signal that you're picking up with this radio telescope is really really weak, So in order for you to have it, uh and to to transmit first you have to you have to transfer the radio frequency information by by changing it into electricity. But because the frequency signal is so weak, the electric current would be pretty pathetic. You would not be able to measure it just by converting it right from radio frequency to electricity without amplifying it in some way. So typically a radio telescope will then have a pre amplifier. So you musicians out there and and and radio folks, you know, you're probably pretty familiar with the idea of a pre amplifier. Microphones usually have a pre amplifier that kind of thing. Um So, a pre amplifier is really just a a way of boosting a signal a certain amount before it gets truly amplified, uh for the final use of whatever that signal is gonna be, whether it's in the audio industry, or in this case, the measuring the celestial bodies. Yeah, I was gonna say that they don't necessarily usually have them anyway. Um, well, that's that's fair, but it does. It does assist, uh, and in picking up these weak signals, that's for sure. Yeah. And so the kind that tends to be used in radio telescopes are called low noise amplifiers because we're talking about such small, very very quiet signals. And so, boy, I'm glad didn't do the old listener mail beginning because then with all this it would have proably blown everybody's ears out. So the the these l n A pre amplifiers take these um signals and then they boost them. Now here's the thing. Any sort of interference at this point could really compromise the measurements you're making. So that includes molecular movement of the pre amp. So the fact that you know, everything in matter is made up of molecules, and these molecules move even in solid objects, right, yes, so they in a in big radio telescope facilities, things like the professional ones that you would find in say NASA, they tend to have to cool down the pre amplifier to reduce molecular movement as much as possible, and usually to around ten kelvin. It's pretty cold. Pretty cold, yeah, zero kelvin means no molecular movement. That's what like the deepest reaches of space would be is zero kelvin. So ten kelvin's pretty cold. They tend to use liquid helium to cool down the this this device low enough so that it reduces the chance for it to contribute noise to this signal. All right. From there, the signal moves into a mixer, yes, where it has a party and networks with people and not. Oh, should have taken different notes. Okay, well I'll just work from memory here then, um no, a mixer. The mixer's purpose is to change the frequency of the signal. Now, the signals are very high frequency and uh, and it turns out that it's easier to amplify lower frequencies. It's possible to amplify higher frequencies, but in general, it takes less uh effort to amplify the lower frequency signals. And if it's kept it it's high frequency and you're just you're you're working with the frequency at that and it's native frequency. There's the chance they'll travel back up the antenna and create feedback. It's not dissimilar to what would happen with a microphone too close to a speaker, where you get that wonderful sound. That's wonderful. Now you're you're probably more familiar with it than I am with your rock and roll lifestyle and all. So then what happens is the mixer mixes this frequency, not just it doesn't just lower. The way it lowers this frequency is it mixes the frequency with a frequency generated by an oscillator. Okay, so the oscillator creates two frequencies that are both sent into the mixer, and uh one is there the polar opposites of each other. And so the the mixer adds in the lower frequency together with the frequency that came in through the receiver, and that is what it sends out to the intermediate frequency amplifier. So we've gone PREAMPTI mixer. Mixer pulls in a second frequency from the oscillator, the oscillator frequency, the lower one gets combined with the incoming frequency that is then sent to the intermediate frequency amplifier or i F amplifier. And that just process that says is that signal and amplifies it. And we've talked about amplifiers before in this podcast, so I'm not going to get into that. Uh. And then this, this stronger signal from the i F amplifier gets sent to Well, now we've got to go to the square law detectors and the d C processors because we have to create a d see a direct current in order for that to go to a recording device. So this converts the frequency from the amplifier to direct current signals, and it smooths out the signals to make them easier to measure because they fluctuate quite a bit. Even as direct current, they tend to fluctuate. So the way they do this is they use capacitors. And if you recall we've talked about capacitors before too, capacitors store up electricity and then release it all at once, right. They're they're kind of like a battery that it can store electricity, but unlike a battery, it is and it releases all the electricity. It doesn't do a constant flow. This, by the way, is the reason why it's a bad idea to fiddle around with electronics. You don't know a lot about, including things like televisions and computers because they have capacitors in them that can store high amounts of electricity that are potentially deadly. So especially things like computers and televisions, you don't want to, you know, just knock a hole in one or you know. I have seen like videos. If you've ever seen a video of someone who who excellently breaks the television, you see a spark go off. That's a capacitor that's that's discharging, and those can be very dangerous. Chris and I have a little bit more to say about radio telescopes, but before we do, let's take another quick break to thank our sponsor. I have read an interesting analogy which said, imagine that you have a water hose and water is moving through the hose, but the pressure keeps changing, so the water sometimes it's flowing out very quickly and sometimes it's sputtering out. Okay uh. In the case of this detecting radio frequencies, you want to a steady um flow so that you can measure it properly. So what if you were to instead of just measure the measuring the water that comes out of the hose, you you direct the hose towards a bucket, okay, and at the base of the bucket there's this big it that you can open up. Well, if you open up the spin on the bucket, water is going to flow out at a much more steady rate than it's flowing out of the hose. That's the kind of idea here with the capacitor, and that it's to try and smooth out that signal and make it easier to record, and then finally you've got the actual recording device. Now, in the old days, the recording device was a an old man who said what is that? No, it was actually a pen attached to a a movable arm and some paper that was pulled across and then the movable arm would would move depending upon changes in voltage. And so it's very similar to uh earthquake detecting equipment. We talked about seismological equipment in the past where you see that or even if you think also a similar things light detectors, that's what I was saying, polygraphs where they have the little the little pen that scratches back and forth across the papers, the papers going by, similar kind of thing. Um Now in October fourteen, yeah, so we when did you go super nova. Um. No, so this in this case instead, what's doing is it's actually uh, modern ones don't tend to use this anymore. They tend to actually send the data directly to a computer where it gets recorded and you read out the information on a computer screen, as opposed to looking at a physical representation scratched out in pen um. That's generally how the radio telescope works from start to finish. So it's pretty interesting stuff. It's a little complex, I would say, yeah, yeah, Um. One of the things that uh, we were talking about two Jonathan mentioned, um the Jansky's experiments where he was he would note that the interference would come around at a certain period of time. UM. One of the prime places to put a radio telescope is near the equator because it is really good. Um. It's a really good place to get an accurate depiction as the Earth rotates, um, and it can it can identify sources of radio information coming from space very clearly. UM. Unfortunately, it's a rather expensive place to try to build a radio telescopes, and that's one of the reasons why they can be found in many different places around the world. But yea closer to the equator tends to be better just for the you know, the quality of information you can get from this. UM and and uh, we've actually started using radio telescopes to kind of map out the celestial bodies around us, even ones that are not visible to the naked eye. And it's been very useful for astronomers. And there's still there's still even you know, uh, amateur astronomers who use radio telescopes. This this it's not just the realm of massive scientific organizations like NASA, although I mean those are the ones that you know, if you look up the pictures online, you tend to see the really larger arrays or really large antennas that belonged to these major organizations. Now, a radio telescope is able to detect things celestial bodies and sky by their angular resolution. UM. Basically it it really is contingent on the wavelengths that it is able to detect. So that's one of the reasons why UM, a radio telescope does need to be large. UM. Yeah, if you you could build a small one, but it wouldn't be nearly as functional as a larger one. Basically, the larger radio telescope is the greater it's angular resolution. Um. But um that that's basically uh, that's basically what it is. What what it's using. In terms of how you would measure the effectiveness of a radio telescope. Yeah, if you you know, if you had like a backyard telescope visual telescope, the resolution you would get on that is equivalent to what you would get with a huge radio telescope. The solution on a radio telescope is proportional to its size. So um, yeah, you've gotta have a big one if you're going to have any any real precise resolution. And again we're not, you know, it's it's a little weird because it's hard to think of resolution in terms of something other than visible light because that's what we're mostly familiar with. But but yes, it's it still applies in this case. Yep, yep, um and radio basically, radio astronomers have been able to detect all kinds of different molecules in space too. Um, you can. You might be surprised to learn. I was a little surprised to learn that radio radio astronomers were able to identify carbon dioxide, water, formaldehyde, ethyl alcohol, methanol, ammonia, UM and all kinds of other different kinds of just that kinds twice of compounds out in space UM and and to use the radio telescope in that way, I mean it's you can get a lot of information. And that's actually uh sort of ties back into the SETI project because the if if you haven't listened to that particular podcast or are unfamiliar with the project, Basically, UM astronomers were collecting large amounts of data from the radio telescope. They were using UM for their project, and the thing is their computers couldn't analyze it all at one time. They were collecting so much that it was just stacking up essentially, not literally but to figurative. To create an analogy, We've talked about in the past, how on YouTube, users are uploading forty eight hours of content every every minute. So it'd be like telling one person to watch everything that's on YouTube. You've got you've got a growing amount of content that you're never going to catch up to and only so much ability to consume it. So same sort of thing. In this case, we're talking about generating uh, incredible amounts of data and having a limited ability to actually analyze the information. So what they would do was to break it down and use it in a distributed computing project, which they were calling SETI at Home, and the idea being that people take a slice of information, allow their computers to work it out using a specially designed program, and send it back to the astronomers so that they could evaluate it and added to the project. And uh, you know, it's just sort of a kind of a neat way to to get into helping out with the project like that. But that's that's one of the problems, a good problem to have with with radio astronomy is that these uh large radio telescopes can couldn't collect an awful lot of data. Yeah, and so we might use them to discover things like quay stars re pulsars that we had never seen before, or even detect the presence of a galaxy that before this point we just didn't know existed. Now. CETI, of course, was really looking for any sort of signals that might indicate a pattern or uh a possible um well possible hint that there's some sort of other intelligent life out there that's generating these signals, not not just some natural phenomenon. Do do do do well? Um and radio. Radio telescopes can also detect information about near celestial bodies as well. The surface. For the Moon, we knew it was sort of sandy before people actually landed there because astronomers had used radio telescopes to, uh to get signals from the Moon and learn, you know, what it was like. They're also Venus, you know, is shrouded by clouds, but astronomers are able to learn more about the surface by using radio telescopes and radar to get an idea of what these the actual planet surfaces. Well, they've also used it to observe the storms on Jupiter, so that's kind of interesting too, Like they just looked at the weather report for you right today today it's gonna be a big gas. It sounds like my never mind never yes, let's it's most like that, Okay, but yeah, I think, uh, it's it's an interesting topic. It's really and it's one honestly I did not know very much about before we started researching this podcast. I agree with you. I mean I knew of it, I knew it existed, but I didn't really understand what it was doing or how it did it. And it is pretty cool. I mean, it just shows me that radio is way cooler than I ever imagined when I you know, so there you turn a radio on. That's that's the extent of your Maybe you play with a walkie talkie, but that's about it as far as radio goes. And then the more you look into it, the more you're like, wow, this is really phenomenal stuff. Tesla was onto something. It's gonna say you probably had a patent for that. Yeah, I probably did. And then never mind, I'm not gonna go into another Tesla rent. Okay. Then all right, Well that wraps up this discussion. Minka, thank you so much for writing in and jesting that that was a really cool topic for us to tackle. And that wraps up another classic episode of tech Stuff. I hope you guys enjoyed it. It's always a joy to look into tech with Chris. I hope he's doing well. I cannot get him back on the show because he's got better things to do than to sit across the table and talk into a microphone with me. He's doing important work like making people way way smarter. So, Chris, if you're listening, thanks so much. There's a joy to work with you, and it's always fun to listen back to these old episodes. If you want to reach out and suggest new topics for me to cover in future episodes of tech Stuff, go visit our website, it is tech stuff podcast dot com. There you're gonna find all the different ways to reach out to me and to let me know about your suggestions for the show. I greatly appreciate it. Don't forget. You can visit our merchandise store over at t public dot com slash tech stuff. Go check that out. Any purchase you make goes to help the show. We greatly appreciate it, and I'll talk to you again really soon for more on this and thousands of other topics. Is that how stuff Works dot com