# How can we detect extra terrestrial radio signals? **URL:** \ **Category:** Factual Questions\ **Created:** [December 14, 2008, 3:22am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083 "2008-12-14T03:22:06Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [December 15, 2008, 1:58am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/21 "2008-12-15T01:58:11Z")
> [@Musicat](#): > > Yet there they are, hopelessly searching for one signal beamed directly to us. That’s exactly what they _are_ looking for. ---
**Author:** ![Apex\_Rogers](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@Apex\_Rogers](https://boards.straightdope.com/u/Apex_Rogers)\ **Post date:** [December 15, 2008, 2:42am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/22 "2008-12-15T02:42:49Z")
> [@Q.E.D](#): > > That’s exactly what they _are_ looking for. Umm.. you clearly didn’t follow the line of reasoning implied by **Musicat’s** post. S/He was saying that since aliens can’t detect _our_ RF emissions, there’s no reason to think they’d be sending anything our way intentionally. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [December 15, 2008, 2:49am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/23 "2008-12-15T02:49:41Z")
> [@ApexRogers](#): > > S/He was saying that since aliens can’t detect _our_ RF emissions, there’s no reason to think they’d be sending anything our way intentionally. Sure there is. Well, not at _us_, specifically, but in our general direction, sure. After all, we did just that [in 1974](http://en.wikipedia.org/wiki/Arecibo_message). Umm, yourself. ---
**Author:** ![Apex\_Rogers](https://avatars.discourse-cdn.com/v4/letter/a/e480ec/32.png) [@Apex\_Rogers](https://boards.straightdope.com/u/Apex_Rogers)\ **Post date:** [December 15, 2008, 3:06am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/24 "2008-12-15T03:06:48Z")
> [@Q.E.D](#): > > Sure there is. Well, not at _us_, specifically, but in our general direction, sure. After all, we did just that [in 1974](http://en.wikipedia.org/wiki/Arecibo_message). > > Umm, yourself. I didn’t mean to present the argument as my own, though I can see how it would be read that way. I was trying to clarify **Musicat’s** stance in light of your curious reply earlier. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [December 15, 2008, 3:26am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/25 "2008-12-15T03:26:12Z")
> [@Q.E.D](#): > > Umm, yourself. May I use that to dis someone who dissses me, or do you have it copyrighted? 🙂 ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [December 15, 2008, 3:37am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/26 "2008-12-15T03:37:33Z")
All yours. ---
**Author:** ![guizot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guizot/32/3636_2.png) [@guizot](https://boards.straightdope.com/u/guizot)\ **Post date:** [December 15, 2008, 11:41am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/27 "2008-12-15T11:41:16Z")
> [@Wendell\_Wagner](#): > > guizot writes: > > \> So all we’d pick up would be old radio shows from other planets. That hardly > \> seems useful to me. Imagine how stale the jokes would be from the Jack Benny > \> equivalent of Theta Centari-C. > > Did you read my post or did you just pick a random post to quote when you replied? The point of my post is that any star is too far away for even a huge radiotelescope to be able to pick out our television and radio signals from the noise. After two years no receiving apparatus can pick out a TV or radio signal. Yeah, I got your point. It was just a bad joke. Even if they could pick out our signals from the noise, what exactly would we want to say? I know they sent out that thing that tries to describe humankind on earth in pictures and icons. bit it could easily just seem like gibberish to them. Not that it isn’t worth a try. And really, how practical is it to communicate with beings of an unknown nature when it takes years to reach them? Theoretically it’s a fascinating idea. But Star Trek was just a TV show. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [December 15, 2008, 3:11pm UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/28 "2008-12-15T15:11:38Z")
> [@Baldwin](#): > > (Actually, that’s the premise of one of my screenplay outlines, in which ordinary television from an alien civilization becomes hugely popular on Earth.) I like it. It’s a nice reversal of the normal sci-fi theme of: Alien race that’s technologically more advanced than us, but culturally one-dimensional, become enamored with American TV and rock n roll. And what is this thing that you call “love”? :rolleyes: Seriously though; good idea. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [December 15, 2008, 3:31pm UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/29 "2008-12-15T15:31:45Z")
> [@SenorBeef](#): > > Well, yes, but there aren’t many stars that close Just so everybody’s clear, there’s exactly one star within the two-light-year sphere. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [December 15, 2008, 7:34pm UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/30 "2008-12-15T19:34:38Z")
> [@guizot](#): > > Imagine how stale the jokes would be from the Jack Benny equivalent of Theta Centari-C. Now excise that out! ---
**Author:** ![guizot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guizot/32/3636_2.png) [@guizot](https://boards.straightdope.com/u/guizot)\ **Post date:** [December 15, 2008, 11:50pm UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/31 "2008-12-15T23:50:38Z")
> [@Bryan\_Ekers](#): > > Now excise that out! Okay, some of his jokes still stand. But do you think the beings of Theta Centari-C are really going to find it funny that Jack Benny is stingy? On the other hand, they might send us jokes about how glomulobilus retroflection makes for hilarious situation comedies. Once we decode it, do you think we’re going to be rolling in the aisles with laughter because one character decided to transform into a reptile, rather than the expected marsupial? ---
**Author:** ![Baldwin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/baldwin/32/7264_2.png) [@Baldwin](https://boards.straightdope.com/u/Baldwin)\ **Post date:** [December 16, 2008, 2:17am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/32 "2008-12-16T02:17:24Z")
> [@Q.E.D](#): > > **Wendell** is. To detect incidental RF activity (that is to say, signals like our commercial TV and radio broadcasts which aren’t intentionally beamed towards us) would require an antenna (or an equivalent array of antennae) spanning roughly the diameter of the solar system to pick it out of the background noise floor. I’ll bet a thousand years from now (if our civilization survives and continues to advance) we’ll be able to do just that. And we’re a very young civilization. So maybe, just maybe, there’s somebody out there who’ll hear us someday. On the other hand (referring to us listening for others) will more advanced civilizations be spewing EM waves in all directions? Maybe all their communications are on tight beams, or through cute li’l wormholes or something. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [December 16, 2008, 2:24am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/33 "2008-12-16T02:24:43Z")
> [@Baldwin](#): > > will more advanced civilizations be spewing EM waves in all directions? Maybe all their communications are on tight beams, or through cute li’l wormholes or something. Did SETI look for strong signals particularly designed to announce the presence of another civilization rather than weak _I Love Lucy_ shows? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [December 16, 2008, 2:25am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/34 "2008-12-16T02:25:21Z")
> [@Baldwin](#): > > I’ll bet a thousand years from now (if our civilization survives and continues to advance) we’ll be able to do just that. I don’t doubt we’ll be able to do that even sooner. We wouldn’t need to build a single large antenna that size; we need only deploy several smaller antennae across that distance and use aperture synthesis interferometry. We use the same technique on a much smaller scale right now, for example, in the VLA in New Mexico. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [December 16, 2008, 3:24am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/35 "2008-12-16T03:24:55Z")
> [@Q.E.D](#): > > aperture synthesis interferometry Does that go through the deflector dish or the Bussard ramscoops? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 16, 2008, 3:29am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/36 "2008-12-16T03:29:33Z")
> [@](#): > > Does that go through the deflector dish or the Bussard ramscoops? All three, of course. That’s the whole point of aperture synthesis. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [December 16, 2008, 4:07am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/37 "2008-12-16T04:07:39Z")
> [@Chronos](#): > > All three, of course. That’s the whole point of aperture synthesis. Aperture Synthesis gets you the angular resolution, which is determined by the physical seperation of two or more smaller dishes. And a bunch of computing power as well. The amount of signal you collect is just a function of the total area the dishes. So, you still need a bunch of surface area to collect a nice amount of signal. Though, if we ever expand some into something other than low earth orbit, lots o big ass dishes should be able placed in nice zero g regions of the solar system. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [December 16, 2008, 4:08am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/38 "2008-12-16T04:08:22Z")
Once we can start detecting earth-like extrasolar planets, then we should turn our ears toward those. That’s assuming we’re right about life needing a “goldielocks-zone”. But, hey, it’s a good place to start to narrow our focus, rather than the brute-force method we’re using now. Perhaps some ETs have detected our earth-like planet, and are beaming us a message. I’m not holding my breath though. ETA: Another thought… we’d have to be sure to stream a continuous message for a looong time, toward each target, lest they miss our call. It’s not like they (or we) have interstellar voice mail. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [December 16, 2008, 4:09am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/39 "2008-12-16T04:09:26Z")
> [@ApexRogers](#): > > I didn’t mean to present the argument as my own, though I can see how it would be read that way. I was trying to clarify **Musicat’s** stance in light of your curious reply earlier. Thank you, Sir. 🙂 I was also trying to point out, indirectly, that the glaring lack of detection of ANYTHING promising so far by SETI might be due to[ol][_]our inability to detect “ordinary” communications like our TV/Radio signals, and/or[_]The severe restriction in possible sources if we have to depend on only those who are beaming directly at us.[/ol] ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [December 16, 2008, 4:15am UTC](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083/40 "2008-12-16T04:15:28Z")
> [@cmyk](#): > > ETA: Another thought… we’d have to be sure to stream a continuous message for a looong time, toward each target, lest they miss our call. It’s not like they (or we) have interstellar voice mail. Why do I have some cartoon version of an Alien, something like from Futurama or the Simpsons…floating through space with a cell phone… “Can you hear me now?” [Previous page](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083.md?page=1) [Next page](https://boards.straightdope.com/t/how-can-we-detect-extra-terrestrial-radio-signals/477083.md?page=3)