Can our TV signals be picked up on other planets?


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Profile Andy Worth
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Message 794121 - Posted: 7 Aug 2008, 11:38:43 UTC

http://news.bbc.co.uk/1/hi/magazine/7544915.stm

Interesting article on the BBC website.


Can our TV signals be picked up on other planets?



WHO, WHAT, WHY?
The Magazine answers...


A television company has joined forces with a social networking site to send a message to the nearest theoretically inhabitable planet. But can our television and radio broadcasts already be picked up in space?

There is no widely accepted evidence of intelligent extraterrestrial life.

And yet the idea of sending messages to whoever is out there has been a recurrent theme over the years, whether it has been the plaques on Pioneer 10 and 11, Blur's call-sign for Beagle 2, the Arecibo message of 1974 or the Soviet "Mir" message of 1962.

The latest is a collaboration between RDF and Bebo to send a signal to the planet Gliese C, more than 20 light-years away, carrying 500 messages from earth.

In a letter to the Daily Telegraph, former BBC News website science editor Dr David Whitehouse raised the possibility that transmissions from Earth could draw the attention of "malevolent aliens", were any to exist.

But ordinary television and radio broadcasts can also travel out of Earth's atmosphere and through space, albeit quickly becoming mind-bogglingly diffuse and hard to pick up.

Space scientist Dr Chris Davis, of the STFC Appleton Rutherford Laboratory, says it is possible that television and radio signals from Earth could be picked up on other planets, but it isn't easy.

Some radiowaves, such as those of a short-wave frequency, bounce back off the ionosphere and are therefore poor candidates to be picked up in space. But waves like FM radio or television signals can pierce it and travel through the vacuum of space at the speed of light.

THE ANSWER
Many broadcasts penetrate the earths atmosphere and travel through space at the speed of light
Crossing trillions of miles they would become incredibly diffuse and hard to pick up

"There are two things that you would need to get a signal [to other planets] - firstly, it has to be able to leave our planet, secondly it would have to have as much power as possible," says Dr Davis.

"As you go into space that power would dissipate. They would need more and more sensitive equipment to pick it up."

In the case of the RDF/Bebo message, it is being sent in a concentrated beam by the giant RT-70 radio telescope in Ukraine.

But television and radio broadcasts are omni-directional - albeit focused as much as possible towards the horizon - and that means a lot of diffusion.



WHO, WHAT, WHY?
A regular feature in the BBC News Magazine - aiming to answer some of the questions behind the headlines

Assuming the energy spread out equally in a sphere, and that the receiver on Gliese C was as big as the planned Square Kilometre Array of antennas on Earth, the television signals reaching the planet would be a billion, billion, billion times smaller than the original signal generated on Earth, says Dr Maggie Aderin, a space scientist at technology firm Astrium.

"Detecting a signal like this with lots of background noise would be incredibly hard, but what they would look for is a pattern in the signals to show that they were not naturally occurring."

And that of course is what is going on on Earth in the form of the Search for Extra Terrestrial Intelligence programme.



Seti uses facilities such as the Allen Array in California to, among other things, look for meaningful patterns in radio waves from space. And that means if there were aliens out there, they could be doing the same thing.

"Some of our radars are easily detectable quite far, hundreds of light-years, into space, if the aliens wish to try, and if they're in the beam," says Seth Shostak, an astronomer at Seti.

"Of course, no one more than about 50-70 light-years away will have yet heard from us, but I figure that our earliest broadcasts are washing over about one new star system each day. So the potential audience is growing."

Shostak calculates that Nasa's recent broadcast of Beatles music towards Polaris, the North Star, using a 210ft antenna and 20kw of power, would require any potential aliens to have an antenna seven miles across to be aware of it. To actually receive it as music, this would need to be increased to a 500-mile wide antenna. Polaris is 430 light-years away.

But if aliens can watch our television, there might be a problem. Astronomer Carl Sagan, in his book Contact, suggested the first high-powered television broadcast the aliens would have picked up would be Hitler's broadcasts at the Nuremburg rallies.


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Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/1/hi/magazine/7544915.stm

Published: 2008/08/06 12:21:31 GMT

© BBC MMVIII

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Message 794667 - Posted: 8 Aug 2008, 17:38:51 UTC

There was a guy on a chat show here in the UK just now saying that sending this signal is a bad idea because the aliens might come and get us... :-s
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Message 794724 - Posted: 8 Aug 2008, 20:56:06 UTC - in response to Message 794667.

There was a guy on a chat show here in the UK just now saying that sending this signal is a bad idea because the aliens might come and get us... :-s


They wouldn't need our radio signals to know that we exist when they could use fairly simple planet detection technology analogous to what we have now to not only detect the existence of our world but also the fact that there is life here.

Anyway, never really understood what exactly they would "get us" for...? :P

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Message 795037 - Posted: 9 Aug 2008, 11:02:37 UTC
Last modified: 9 Aug 2008, 11:04:25 UTC

Why would they "take us"/"eat us"? Our meat would probably be poisonous to them and if they do not have enough food on their planet, why would they do interstellar travel? :D :D :D :D :D :D :D :D

So, here I already made a proof that ET civilization isn't harmful. Let's send some signals to them so they can figure out who we really are.

Henri.
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Message 796083 - Posted: 11 Aug 2008, 0:20:29 UTC - in response to Message 794724.

Anyway, never really understood what exactly they would "get us" for...? :P


Presumably, they would come for our women. Isn't that what invading space aliens do?

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Message 796154 - Posted: 11 Aug 2008, 3:26:58 UTC - in response to Message 796083.
Last modified: 11 Aug 2008, 3:27:13 UTC

Anyway, never really understood what exactly they would "get us" for...? :P


Presumably, they would come for our women. Isn't that what invading space aliens do?


Heck, I came here for the women and I haven't had much luck so far! :P

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Message 796173 - Posted: 11 Aug 2008, 4:02:21 UTC - in response to Message 796154.

Anyway, never really understood what exactly they would "get us" for...? :P


Presumably, they would come for our women. Isn't that what invading space aliens do?


Heck, I came here for the women and I haven't had much luck so far! :P


Off topic

find single women here ?


Just in case ET likes us chickadees.

Back to the topic now ;)
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Message 796310 - Posted: 11 Aug 2008, 14:47:08 UTC - in response to Message 796173.

Anyway, never really understood what exactly they would "get us" for...? :P


Presumably, they would come for our women. Isn't that what invading space aliens do?


Heck, I came here for the women and I haven't had much luck so far! :P


Off topic

find single women here ?


Just in case ET likes us chickadees.

Back to the topic now ;)


Yeah, we haven't even the slightest idea, what an alien would look like!?
Maybe the look like fish, trees, birds, shrubbery, or whatever? :)
Or something we never/ever dreamed off.

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Message 796334 - Posted: 11 Aug 2008, 16:05:23 UTC - in response to Message 796310.

... shrubbery...


... Shrubberry! ... LoL

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Message 796506 - Posted: 11 Aug 2008, 22:10:23 UTC - in response to Message 796310.


Maybe the look like fish, trees, birds, shrubbery, or whatever? :)
Or something we never/ever dreamed off.


Indeed. I just finished rereading a 1971 short story by Arthur C. Clarke called "A Meeting With Medusa" which involves rather gargantuan life in, of all places, the atmosphere of Jupiter.

We'd best take care regarding any assumptions we make about alien life, or blind dates.

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Message 810414 - Posted: 20 Sep 2008, 23:16:26 UTC - in response to Message 796083.

Anyway, never really understood what exactly they would "get us" for...? :P


Presumably, they would come for our women. Isn't that what invading space aliens do?


Why assume that aliens even know what a woman is... who's to say they reproduce in any way remotly similar to the way we do... in fact, there is no reason to believe that they would resemble us in any way at all. They could be 23 feet tall with 6 arms, and a giant spring like thing to bounce around on... who knows... they developed on a completly different planet! to reproduce, Maybe they just split in two... or even have some stranger method we can't even think of.

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Message 811635 - Posted: 24 Sep 2008, 20:07:45 UTC

There used to be a SETI Institute chart showing how far out we could see our own signals, using our own current technology.

The large radar sites that once made up the DEW (Delay Early Warning) line during the Cold War were shown to go the furthest out -- a few light years.

"Some of our radars are easily detectable quite far, hundreds of light-years, into space, if the aliens wish to try, and if they're in the beam," says Seth Shostak, an astronomer at Seti.

I don't know how they are now saying "hundreds of light years", unless they are speculating on ET being more advanced.

The Inverse Square Law sucks...

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Message 832547 - Posted: 20 Nov 2008, 21:31:52 UTC

Being an S/F reader the body shape of Aliens,is,I have noted a fairly frequent topic in most early S/F stories only a few recent ones touch on it and only in passing.As for the TV signal being detected perhaps the carrier wave may be but probibly not any meaningful content more likley to detect radio broadcasts especily the high power ones that try to be recieved across a large Geographic Area.
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Message 834586 - Posted: 26 Nov 2008, 19:07:49 UTC - in response to Message 832547.

Our earliest transmissions were radio wavwelenghts. Early TV transmissions are probally out to 55 light years or so. Most were omnidirectional and at that vast distance maybe a carrier wave would exist. I think that is what the tripletts and gaussians in seti@home. ET would have to accidentaly tune in at the right frequency and could maybe triangulate the sourse but it has to be a very good reciever. The top 200 hits could very well be some type of ET normal transmissions. Many are around stars that have been detected that are hits also have saturn or larger type planets around them. Cancri 55 has four planets confirmed by Keck observitory. Between the first 3 in close and a very large gap to the fourth planet away from the star. This leaves room for terrestial type planets like earth. This star system has many reoccuring signals from this part of space. Another plus for this star system it has a sun like star slightly smaller and slightly dimmer than our sun.
I think nearby stars would be watching Hitler giving speeches and shortwave transmissions at this time. Some older radion stations have tremedously powerfull signals. Who knows maybe we can show them I Love Lucy reruns.

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Message 834630 - Posted: 26 Nov 2008, 20:55:23 UTC - in response to Message 834586.

lets not forget the old signals are all analog signals. I might be mistaken but I recall these signals being dispersed fairly rapidly through space
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