SETI and the hydrogen frequency?


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Bjørn E. Pedersen
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Message 932303 - Posted: 10 Sep 2009, 18:56:58 UTC

Hi all you happy people.

I'm quite new in the seti@home. And i hoped you could give me some information.

I have installed the boinc screensaver, and it just keep running :)

But my question is: Is SETI only scanning at the frequens of hydrogen and why?
I have found the following link that explains some of it.
http://www.setileague.org/askdr/hydrogen.htm

But Does SETI only scan, at the hydrogen frequency and why?

Has it something to do with, that the background noise from suns and neutronstars are at this frequency?

Sorry if this already have been debated in other topics, but I couldn't find any such topics.

Thanks
Bjørn E. Pedersen

John McCallum
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Message 932310 - Posted: 10 Sep 2009, 19:33:33 UTC - in response to Message 932303.
Last modified: 10 Sep 2009, 19:34:48 UTC

"Has it something to do with, that the background noise from suns and neutron stars are at this frequency?"
You hit the nail on the head my son.The hydrogen frequencies are the least noisy and so it is assumed that any Extraterrestrial will know this also and IF they are trying to communicate with the rest of the galaxy/universe or simply the nearest star to them this is the frequency that they might use.Of course I could be wrong and making all this up.Welcome to the Home for Bewildered Gentlefolk.(AKA s@h forums).
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Bjørn E. Pedersen
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Message 932316 - Posted: 10 Sep 2009, 20:13:09 UTC

Thanks for the Answer John.

John McCallum
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Message 932320 - Posted: 10 Sep 2009, 20:51:26 UTC - in response to Message 932316.

Look in the staff blogs area for more info from Kevin Douglas PHD on the hydrogen subject he did some research on it if I remember correctly.
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Profile Johnney Guinness
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Message 932368 - Posted: 11 Sep 2009, 0:58:58 UTC
Last modified: 11 Sep 2009, 1:05:30 UTC

Bjørn,
You could also read this; How SETI@home works. Its a 6 page article but it explains about why SETI@home searches the hydrogen line.

You could also read; Wikipedia - Hydrogen line

Hydrogen is the simplest and most abundant element in nature and a spectral line is created by changing the energy state of neutral hydrogen. This occurs at about 21 cm or 1420 MHz. Other intelligent civilisations would find this out quite easily and would know its an obvious marker point in the electromagnetic spectrum. Good for telling everybody your here!

John.
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Bjørn E. Pedersen
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Message 932526 - Posted: 11 Sep 2009, 16:51:14 UTC

Thanks for all the answers and links.

I will get right on with styding them :-)

Profile William Rothamel
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Message 933256 - Posted: 14 Sep 2009, 9:33:04 UTC

The SETI frequency that is scanned is one of the absorption lines of Hydrogen. one of the the LYMAN series --I think. It is the most profoundly emissionless region in the spectrum.

Makes you wonder though why a signal wouldn't be absorbed as well by all of the Hydrogen in the path from sender to receiver.

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Message 933258 - Posted: 14 Sep 2009, 9:44:13 UTC - in response to Message 933256.
Last modified: 14 Sep 2009, 9:44:45 UTC

The SETI frequency that is scanned is one of the absorption lines of Hydrogen. one of the the LYMAN series --I think. It is the most profoundly emissionless region in the spectrum.

Makes you wonder though why a signal wouldn't be absorbed as well by all of the Hydrogen in the path from sender to receiver.

Probably because it is very sparse, unless you meet a cloud like the one described in Fred Hoyle's "The black cloud".
Tullio
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Message 933345 - Posted: 14 Sep 2009, 20:57:51 UTC

Guys,
I have a lot of doubts in my mind about only searching the Hydrogen line, which is what SETI@home does. If ET is sitting on his planet shouting on the top of his voice through a star sized telescope, we will still miss it! ET could be sitting there right now saying;
"Why won't those dam Earthlings transmit back?. I have been signalling them for the last 100,000 years!"

I'm really not convinced by the argument about searching the Hydrogen line. I still think the search should be much broader, even if its more difficult to remove the RFI.

John.
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Profile William Rothamel
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Message 933361 - Posted: 14 Sep 2009, 21:25:39 UTC
Last modified: 14 Sep 2009, 21:27:18 UTC

John,

So good to hear from you and Tullio again. Perhaps someone out there who is an Astro-Physicist could comment. I suspect that this is the most logical band to peruse at the microwave spectrum. I don't know if other frequencies or multiples of this frequency makes sense.

What I do know is that spread spectrum communication is extremely effective. Perhaps there is a logical progression of spread spectum sets of frequencies that might be deducible to the cognoscenti--terestrial or alien. Anyone know ??.

What is the Allen Array doing for frequency monitoring? To me--it's more valuable to go back to a hot spot and run it to the ground to see if there might be a true alien signal that might contain unmistakeable intelligence. Such as counting out the prime numbers or cycling through the first 50 digits of pi.

Regards,

Bill

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Message 933444 - Posted: 15 Sep 2009, 4:09:30 UTC

AFAIK SETI is looking for a narrow line emission, Astropulse (which I don't get anymore on my Linux box) is searching a wider spectrum. Also Einstein has a search called astrobinarypulsar which searches for binary pulsars in Arecibo data and that is also a wide spectrum search. That one I can crunch. Cheers.
Tullio
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Bjørn E. Pedersen
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Message 935737 - Posted: 24 Sep 2009, 23:12:08 UTC

I just found a link where theoretical physicist, Michio Kaku talks about SETI and the hydrogen Frequency.
As Michio Says maybe aliens use another frequency or maybe laser technology.

http://www.youtube.com/watch?v=Kw8dcb8iKSM

Much of his argumentation makes sense to me.

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