184 replies to this topic

[bison]

MedicTJ, on 13 December 2012 - 07:50 PM, said:

Come on.  There's nobody else out there.  It's just us.  Think about it.  Out of all the BILLIONS of galaxies out there that receive light from, there HAS to have been not only one signal....but BILLIONS of signals.  Is someone gonna tell me that we're the only ones that use radio frequencies to communicate?

As soon as SETI turned on, they should have found something....if anything was out there.

         When we consider the very many combinations of the correct radio frequency, the correct time, during which we might receive a signal, and the required level of signal sensitivity, it is as if we have dipped a glass full of water out of the ocean, and finding no fish in it, conclude that none exist. The fact that an extraterrestrial signal was not found  almost immediately may simply mean that the task of finding such a signal is not an especially easy one. Perhaps this is because the rest of the galaxy is not devoting a large part of its time and resources to the task of communicating with us, on this one small planet. Given the billions of stars in the galaxy, this should not be surprising.

[Colonel Rhuairidh]

MedicTJ, on 13 December 2012 - 07:50 PM, said:

Come on.  There's nobody else out there.  It's just us.  Think about it.  Out of all the BILLIONS of galaxies out there that receive light from, there HAS to have been not only one signal....but BILLIONS of signals.  Is someone gonna tell me that we're the only ones that use radio frequencies to communicate?

As soon as SETI turned on, they should have found something....if anything was out there.

You know that radio signals can only be discerned if they're specifically transmitted at us?; general background chatter or things like radio or TV broadcasts (this was where Carl Sagan was apparently wrong) wouldn't be discernible at interstellar distances. Until we started sending signals out, no one would have thought it worthwhile to transmit anything towards us, unless it was in the manner of a specualtive probing sweep, e.g. the WoW signal.

Edited by 747400, 13 December 2012 - 08:32 PM.

[TheMacGuffin]

747400, on 13 December 2012 - 08:31 PM, said:

You know that radio signals can only be discerned if they're specifically transmitted at us?; general background chatter or things like radio or TV broadcasts (this was where Carl Sagan was apparently wrong) wouldn't be discernible at interstellar distances. Until we started sending signals out, no one would have thought it worthwhile to transmit anything towards us, unless it was in the manner of a specualtive probing sweep, e.g. the WoW signal.

I think it would have to be a very powerful transmitter aimed in our general direction for us to be able to pick it up.  That's why some people think that the 1977 Wow signal was an answer to the 1977 Arecibo signal.  Of course, who was doing the signalling and from where is anybody's guess.

I would not be at all surprised if ET signals might be picked up from something much closer than we imagine.

[kampz]

edit

Edited by kampz, 14 December 2012 - 02:25 AM.

[kampz]

MedicTJ, on 13 December 2012 - 07:50 PM, said:

Come on.  There's nobody else out there.  It's just us.  Think about it.  Out of all the BILLIONS of galaxies out there that receive light from, there HAS to have been not only one signal....but BILLIONS of signals.  Is someone gonna tell me that we're the only ones that use radio frequencies to communicate?

As soon as SETI turned on, they should have found something....if anything was out there.

Why do you believe there are billions of galaxies out there and why should there be intelligent life on it? Because you see pictures? Do believe in wood? I do because we have trees and pictures.

Edited by kampz, 14 December 2012 - 02:28 AM.

[Harte]

MedicTJ, on 13 December 2012 - 07:50 PM, said:

Come on.  There's nobody else out there.  It's just us.  Think about it.  Out of all the BILLIONS of galaxies out there that receive light from, there HAS to have been not only one signal....but BILLIONS of signals.  Is someone gonna tell me that we're the only ones that use radio frequencies to communicate?

As soon as SETI turned on, they should have found something....if anything was out there.

Due to signal attenuation, your logic falls completely apart.

We'd be lucky to pick up anything beyond about 10 LY unless it was purposefully sent directly to us.

Any radio signal that could survive intact over much greater distances would require an amount of power that would make it not worth the effort, given (obviously) the time lag.  That is, there couldn't be any meaningful communications. i.e. conversations.

Harte

[badeskov]

Harte, on 14 December 2012 - 02:38 AM, said:

Due to signal attenuation, your logic falls completely apart.

We'd be lucky to pick up anything beyond about 10 LY unless it was purposefully sent directly to us.

Any radio signal that could survive intact over much greater distances would require an amount of power that would make it not worth the effort, given (obviously) the time lag.  That is, there couldn't be any meaningful communications. i.e. conversations.

Harte

Harte,

It is very rare that I disagree with you, but here I'd like to offer a correction, albeit a small one. The strongest signals we emit into space are from the Ballistic Missile Early Warning System (BMEWS) radars and with our technology we should be able to detect those emissions out to about 200 LY before they drown in the background noise.

Cheers,
Badeskov

[Harte]

badeskov, on 14 December 2012 - 05:33 AM, said:

Harte,

It is very rare that I disagree with you, but here I'd like to offer a correction, albeit a small one. The strongest signals we emit into space are from the Ballistic Missile Early Warning System (BMEWS) radars and with our technology we should be able to detect those emissions out to about 200 LY before they drown in the background noise.

Cheers,
Badeskov

Okay. Knowing you, I'll take your word on that.

But the post I responded to appears to be talking about normal communications.

You see the claim all the time that aliens might have recieved (for example) our television broadcasts.  Not long ago there was an internet claim that a nearby star system had responded to the very first radio broadcast!

I'm pointing out that such a belief is fatuous.  It ain't gonna happen.

Harte

[bison]

Statements about how far away our signals could be heard in space are based on the capabilities of *our* technology. Given the age of the galaxy, and how much time there has been for other civilizations to develop, there could be races a billion or more years ahead of us, technically speaking. Why should our technical limitations apply to them?
There has been serious scientific discussion abvout the possibility of using the Sun as giant gravitational lens, which could focus interstellar radio waves. This method would enable its users to hear signals of even very modest power from throughout the galaxy.

Edited by bison, 14 December 2012 - 03:29 PM.

[Quaentum]

Time must also be taken into account.  If a civilizations is say 10,000 years more advanced then us and their first signals were sent 10,000 years ago but their planet is 11,000 LY from ours, then we wouldn't even begin to receive the signals for another thousand years.

[Harte]

bison, on 14 December 2012 - 03:27 PM, said:

Statements about how far away our signals could be heard in space are based on the capabilities of *our* technology. Given the age of the galaxy, and how much time there has been for other civilizations to develop, there could be races a billion or more years ahead of us, technically speaking. Why should our technical limitations apply to them?

Noise to signal ratios are real things and are not amenable to "high technology."

If aliens that far away could dismiss the attenuation of EM waves so easily, they wouldn't be looking for anyone like us anyway.

bison, on 14 December 2012 - 03:27 PM, said:

There has been serious scientific discussion about the possibility of using the Sun as giant gravitational lens, which could focus interstellar radio waves. This method would enable its users to hear signals of even very modest power from throughout the galaxy.

"Serious" scientific discussion?

The method would present plenty of problems, not the least of which would be the inability to focus waves except in a relatively small volume of space, the same distance in every direction.  Using gravitational lenses means manipulating gravity, which we can't do.  So our lens (the Sun) would be "set" to the same focal length in every direction.

Harte

Edited by Harte, 14 December 2012 - 04:47 PM.

[bmk1245]

quillius, on 10 December 2012 - 10:05 AM, said:

actually I do, and what you say above actually strengthens my point which seems to have been missed by most (except 747).

Yes 1LY is such a great distance we will not do it in a single lifetime rendering the distance of 1LY impossible right? so what difference is 1000LY to 10000 LY...both impossible in a lifetime? is one more impossible than the other??
[...]

First of all, I assumed we are talking about civilizations bit advanced than ours, i.e. capable of reaching significant ratio  v/c (0.8, 0.9, 0.995, etc). That alone would give you a chance to travel long distances in your lifetime (energy requirements, though, are immense... ).
Now 1000LY vs 10000LY. That gives you 100 times bigger volume (disk of Milky Way is ~1000LY thick, so cylinder shape is of better use) to search. Which first civilization would find us, if:
1) civilizations, both 1000LY and 10000LY from us, are on comparable technological level? Best guess - 1000LY;
2) civilization 1000LY from us is far more advanced than civilization 10000LY from us? Best quess - 1000LY;
3) civilization 10000LY from us is far more advanced than civilization 1000LY from us? Best guess - 10000LY (though, how "far" is far?).
I know, thats very simplistic, but chances we would be found by civilization that is not that far from us rather than from Andromeda (just curious, did D.Sereda returned from Andromeda, or he's still  building "galactic clock spaceship"?) are better.

quillius, on 10 December 2012 - 10:05 AM, said:

[...]can I swim 1000 miles under water? is it less likely I can swim 10000 miles under water?

Ah, thats easy, grow the gills...

quillius, on 10 December 2012 - 10:07 AM, said:

so something as definitive as 'impossible' you are suggesting has a range..i.e. 'more'??? impossible is impossible I thought...oh well...

I know, kinda optimaler/optimalest than optimal, but "impossible" in 747 post I understood as "impossible to us at the current state".

PS, sorry, 747, I did not replied to you post, since I was waiting for quillius for clarification.

[bison]

Harte, on 14 December 2012 - 04:46 PM, said:

Noise to signal ratios are real things and are not amenable to "high technology."

If aliens that far away could dismiss the attenuation of EM waves so easily, they wouldn't be looking for anyone like us anyway.



"Serious" scientific discussion?

The method would present plenty of problems, not the least of which would be the inability to focus waves except in a relatively small volume of space, the same distance in every direction.  Using gravitational lenses means manipulating gravity, which we can't do.  So our lens (the Sun) would be "set" to the same focal length in every direction.

Harte

                 Yes, recognized scientists have written quite seriously about the idea. Perhaps the most prominent of these, Dr. Frank Drake. A good, brief outline of the idea is found in chapter 10 of his book: 'Is Anyone Out There'? A space probe could be sent to the distance of the focal point of a star, and moved about at that distance to receive signals from different directions, coming in from the point directly behind the star. An advanced civilization might maintain a number of such probes at the same time, each monitoring targets of interest. Yes the method presents problems from our point of view. It would first be necessary to send a probe out to at least 550 Astronomical units, preferably 1000 AU, and maintain a communications link with it.

[bison]

1000 Astronomical Units is roughly 8 times farther out than our most distant current space probe, Voyager 1.  At Voyager's average speed it would take close to three centuries to reach 1000 AU. It would then be between 11 and 12 light days out. Its signal would be just under 2% as strong as that of Voyager is currently. Even if the probe was not maneuverable, if it were in orbit of the Sun it would slowly sweep across the focal point of various stars, at points directly opposite the Sun from its position.

Edited by bison, 14 December 2012 - 11:37 PM.

[badeskov]

Harte, on 14 December 2012 - 01:15 PM, said:

Okay. Knowing you, I'll take your word on that.

Quote

But the post I responded to appears to be talking about normal communications.

I saw that afterwards, I apologize. I was in the lab on my phone, so maybe a little fast on the keyboard. However, normal communications could fall under the same umbrella was one to use a directional antenna and point it somewhere into space.

Quote

You see the claim all the time that aliens might have recieved (for example) our television broadcasts.  Not long ago there was an internet claim that a nearby star system had responded to the very first radio broadcast!

That I completely agree with. The notion is utterly ludicrous. Nobody is going to respond to the Lucy broadcasts or what have you. And I have to make a small correction again. Detecting our broadcasts with technology we currently have and can envision in the near future would be possible maybe outside of our solar system, not much futher thanks to the omnidirectivity of the antennas used.

Quote

I'm pointing out that such a belief is fatuous.  It ain't gonna happen.

Nope!

Cheers,
Badeskov

Edited to add a small blurp I wrote about this some years back.

Edited by badeskov, 15 December 2012 - 12:03 AM.