Detection of artificial extrasolar signals...

I don't know whether this is the correct forum to post this in, but since the Honorverse is Mr Weber's 'space playground' I thought it the best location.

I've read a lot about our failure to detect artificial signals from other solar systems and how this might be an indication that there are no sentient alien life out there, etc. etc. etc.

It made me think, but since I'm not an astronomer or an astro anything, I thought I'd ask the experts for their input.

Given that our (Earth's) total artificial energy output is orders of magnitude smaller than our own sun's, at this stage of our technological development, how would any alien civilization at a comparable level of technological development manage to transmit a clear, unbroken signal over the vast distances involved?

After all, such a signal would not only have to 'break through' the background radiation of their own star, but would also have to travel across unimaginable interstellar distances where it'd have to contend with the combined radiation interference of hundreds of billions of stars. Could such a signal actually survive that journey without being entirely disrupted or dispersed by all the radiation it'd encounter during its journey?

hanuman wrote:I don't know whether this is the correct forum to post this in, but since the Honorverse is Mr Weber's 'space playground' I thought it the best location.

I've read a lot about our failure to detect artificial signals from other solar systems and how this might be an indication that there are no sentient alien life out there, etc. etc. etc.

It made me think, but since I'm not an astronomer or an astro anything, I thought I'd ask the experts for their input.

Given that our (Earth's) total artificial energy output is orders of magnitude smaller than our own sun's, at this stage of our technological development, how would any alien civilization at a comparable level of technological development manage to transmit a clear, unbroken signal over the vast distances involved?

After all, such a signal would not only have to 'break through' the background radiation of their own star, but would also have to travel across unimaginable interstellar distances where it'd have to contend with the combined radiation interference of hundreds of billions of stars. Could such a signal actually survive that journey without being entirely disrupted or dispersed by all the radiation it'd encounter during its journey?

Since this isn't directly related to the Honorverse, it should probably go into the Free-Range Topics forum. Maybe Duckk will move it for you...?

Edit: Hahahahaa... it got moved as I was writing...

Edit #2: Still showing in the Honorverse forum though, but when you reply, it redirects to Free-Range.

hanuman wrote:I don't know whether this is the correct forum to post this in, but since the Honorverse is Mr Weber's 'space playground' I thought it the best location.

I've read a lot about our failure to detect artificial signals from other solar systems and how this might be an indication that there are no sentient alien life out there, etc. etc. etc.

It made me think, but since I'm not an astronomer or an astro anything, I thought I'd ask the experts for their input....

I'm not an expert, but I think I can address some of your points.


IMHO, the real world doesn't have sufficient room or technology do do more than search cosmic noise for a specific frequency that SETI believes can travel interstellar distances and still be distinct from the background noise.

The Honorverse, OTOH has detection arrays that span entire solar systems that just might be able to detect and decode signs of intelligence. If those arrays were looking for the right signals, which they aren't and probably won't be in the foreseeable future. The Honoverse doesn't really need such long range sensors when they can get a lot better look by traveling FTL to a star they're interested in.

As I understand it, detecting and isolating intelligent signals requires the equivalent of a Very, Very, Very large parabolic dish antenna. The bigger the dish, the weaker the signal that can be detected. Isolating the signal from the noise is a trivial problem on a par with tuning in a single radio station from the broadcast spectrum.

IMHO, it can be done -- both RW and Honorverse -- but the investment won't justify the possible return. In the RW it will be far too expensive to launch and coordinate the necessary sensor net, and in the Honorverse, it would be redundant to FTL travel.

Weird Harold wrote:
I'm not an expert, but I think I can address some of your points.


IMHO, the real world doesn't have sufficient room or technology do do more than search cosmic noise for a specific frequency that SETI believes can travel interstellar distances and still be distinct from the background noise.

The Honorverse, OTOH has detection arrays that span entire solar systems that just might be able to detect and decode signs of intelligence. If those arrays were looking for the right signals, which they aren't and probably won't be in the foreseeable future. The Honoverse doesn't really need such long range sensors when they can get a lot better look by traveling FTL to a star they're interested in.

As I understand it, detecting and isolating intelligent signals requires the equivalent of a Very, Very, Very large parabolic dish antenna. The bigger the dish, the weaker the signal that can be detected. Isolating the signal from the noise is a trivial problem on a par with tuning in a single radio station from the broadcast spectrum.

IMHO, it can be done -- both RW and Honorverse -- but the investment won't justify the possible return. In the RW it will be far too expensive to launch and coordinate the necessary sensor net, and in the Honorverse, it would be redundant to FTL travel.

But such a signal would first have to get here, and that's what I'm asking. Given the tremendous background radiation from our hypothetical aliens' own star, plus the combined radiation interference of billions upon billions from other stars that such a signal will encounter during its journey through interstellar space, could it possibly survive the journey close enough to intact to be detected by us? Wouldn't all that unimaginable solar radiation simply disperse or scatter what would after all be a comparatively weak signal?

Actually, Earth's radio emissions can probably be detected for hundreds of light-years with a powerful enough detector. It is easily distinguishable mere noise, and at certain radio frequencies we outshine the sun.

So the answer to the direct question is, yes, it is possible to detect signals over interstellar distances.

The answer to the unstated underlying question is less optimistic--if there are civilizations out there, are we likely to be able to detect them with radio telescopes? There are additional unknown parameters involved in answering that question.

For example, most astronomers assume that a civilization would emit powerful broadcast radio signals for a limited fraction of its lifetime. After that, less indiscriminate methods of communication would probably be used. So unless a really advanced civilization deliberately set up radio beacons to attract the attention of incipient civilizations, we would only be able to detect a given civilization for a geologically narrow window, depending on how far away it is.

There are other issues as well, and it all adds up to a rather pessimistic estimate of the chances of SETI detecting anything. Still, it is possible, and we won't know if we don't try.

hanuman wrote:But such a signal would first have to get here, and that's what I'm asking. Given the tremendous background radiation from our hypothetical aliens' own star, plus the combined radiation interference of billions upon billions from other stars that such a signal will encounter during its journey through interstellar space, could it possibly survive the journey close enough to intact to be detected by us? Wouldn't all that unimaginable solar radiation simply disperse or scatter what would after all be a comparatively weak signal?

The signal would be very weak but unchanged from it's original nature. Electromagnetic radiation isn't like water -- signals don't dissolve into a glutenous mass of radiation. Signals can and do get "drowned out" by stronger signals, but if you cancel out the strong signals the target signal is still there to be isolated and decoded.

It is far more difficult than finding a needle in a haystack, but with a sensitive enough antenna and fine enough tuning and signal clarifiers, it should be possible for some distant planet to tune in and watch first-run episodes of I Love Lucy and the Show of Shows.or listen to Dreadful Dreadfuls on AM radio frequencies. (KBLU San Francisco, 1950s Saturday night radio suspense series featuring 1939-40 radio programs.)

Weird Harold wrote:

hanuman wrote:But such a signal would first have to get here, and that's what I'm asking. Given the tremendous background radiation from our hypothetical aliens' own star, plus the combined radiation interference of billions upon billions from other stars that such a signal will encounter during its journey through interstellar space, could it possibly survive the journey close enough to intact to be detected by us? Wouldn't all that unimaginable solar radiation simply disperse or scatter what would after all be a comparatively weak signal?

The signal would be very weak but unchanged from it's original nature. Electromagnetic radiation isn't like water -- signals don't dissolve into a glutenous mass of radiation. Signals can and do get "drowned out" by stronger signals, but if you cancel out the strong signals the target signal is still there to be isolated and decoded.

It is far more difficult than finding a needle in a haystack, but with a sensitive enough antenna and fine enough tuning and signal clarifiers, it should be possible for some distant planet to tune in and watch first-run episodes of I Love Lucy and the Show of Shows.or listen to Dreadful Dreadfuls on AM radio frequencies. (KBLU San Francisco, 1950s Saturday night radio suspense series featuring 1939-40 radio programs.)

Thank you, both WeirdHarold and SWM. Your answers were very informative and answered my question quite nicely. Once again, thank you.

Didn't thenovel, and movie, Contact address some of those points?

http://www.cbc.ca/quirks/episode/2012/0 ... ne-9-2012/

Part one answers some of this.

I was in the audience.

The jist that came across is that even though the universe is old the age of the universe is about right for the development of us( civilizations). but given how far apart Solar systems are from each other, (we) may not received a signal yet because (we) only have been sending out signals for a very short time.

It was also inferred that it could be that we are the first or one of the first races planets to evolve this far. Not counting strange UFO's. we have no evidence made public to say otherwise.

Signals have been leaving earth for less than a 100 years. anything further than 100 light years away wouldn't get here. Plus SETI searches very little of those areas.

In addition people tend to limit ourselves to looking for things like us. The way we would do it, using a system like our own. Heck even our supposed universal language assumes many things that may not hold when dealing with others.

We also have concepts that we hold as limits that others would have to follow. Like Aliens couldn't travel to earth as it would be too expensive. Who says aliens have money? or are short of resources? Pointing out that the pyramids are so expensive that no one could afford to built them now, let alone 4-5000 years ago....

We are finding planets now, I would be interested to see if SETI is searching those locations or still looking where someone else guessed something might be.

When thinking about this, you might want to look at what the Fount of All Knowledge has to say:

http://en.wikipedia.org/wiki/Fermi_paradox

It looks like a pretty comprehensive analysis.