Could we possibly receive radio transmissions from the center of our galaxy?

[Kobymaru]

Hi!

I've been reading this incredibly interesting article from the Blog Wait but Why: http://waitbutwhy.com/2014/05/fermi-paradox.html about the Fermi paradoxon:

If there are so many, many Stars and planets, then at least a few should have intelligent life. But so far, we have seen no evidence of them whatsoever. Why not?

The article cites some reasons for that, most of which are scary.

Hoewever, there is one more reason i thought of, but I can't really tell if it's plausible or not.

Is the reason that we haven't heard of aliens simply that they're just way too far away from us, to receive any coherent signals?

In order to answer that, I wanted to ask some of you math/physics/engineering experts here the following:

What is the weakest coherent radio signal that we could receive today? And assuming that someone from the center of our galaxy (which seems to be a good as place as any too look for signals), how strong would aliens sending a signal have to make so that it arrives with that weakest signal we could receive?

Would it require a feasible amount of energy? Is it possible to make an antenna that can send such signals? Can WE currently make such an antenna?

I'm looking for discussions and happy for everyone who does the quick (or not so quick) math, because I have very little knowledge about signal transmission and antennas and the likes but this question has been bothering me for a while.

[Aethon]

The largest radio telescope on Earth is Aricebo. IIRC it can put out a 2MW signal which we could detect (with an Aricebo type telescope) out to a distance of 400 (Seth Shostak) to 1000 (Frank Drake) light years.

One of the main reasons we haven't detected a signal is that SETI is in it's infancy. We've really only looked for a signal around about 1000 stars, and those have only been looked at for a few minutes at a time. The image in your link showing all the stars you can see in the night sky in that tiny little circle is one of my favorites. Finding a signal in all that vastness is a Herculean task, like finding a specific needle in a stack of needles. A further complication is we have no idea what a signal from an entity we know nothing about would be like, so it's analogous to looking for a needle, in a stack of needles, without knowing what a needle even is.

The galactic center is an interesting place to look because it is the single, unambiguous point in the galaxy, but it is also an incredibly dangerous place for biologics, like ourselves (our only data point). Incredible energies and dangerous radiation abound. The number of stars is much greater, but so is the occurrence of sterilizing supernovas.

Edited August 30, 2015 by Aethon

[Aethon]

Supernovae could aid us in our search for a signal from ET.

Let's say a supernova goes off in our galaxy (We're way overdue. C'mon Milky way!) and is noticed by a Vogon astronomer who notifies his fellow astronomers, and all the Vogon telescopes slew around to view and study the event- but one clever Vogon thinks hey, if I wait half a day we will be looking the opposite direction from the supernova in the sky, so any non Vogon astronomers on worlds opposite the supernova will be looking directly past us at said nova. So he may send out a powerful ping into the sky (Hey, we're here) in the direction opposite the nova. This could be used to increase the chances of a successful SETI detection.

Edited August 30, 2015 by Aethon

[Scotius]

Area around center of the Galaxy is full of dust and gas. Any signal passing there will be weakened faster, and fade sooner than signal crossing (mostly) empty space between the arms.

[Aethon]

The infrared spectrum actually passes nicely through gas and dust, but our atmosphere is opaque to most most of it, so SETI needs a space telescope. Get out your checkbooks!

[Brethern]

My common thinking is that any race capable of interstellar travel would be smart enough to realize that making themselves known to other species would be a bad idea. So they're stealthfully observing different races until the right time to make first contact comes around.

[Scotius]

Why? Do you think that human adage of "Kill, or be killed" applies to any sentient species? That's very anthropocentric

[AngelLestat]

The explanation of the filter that your blog talk about, it may be also explained in the same blog:

http://waitbutwhy.com/2015/01/artificial-intelligence-revolution-1.html

Or the same thing we are discussing here:

http://forum.kerbalspaceprogram.com/threads/132357-Everything-wrong-with-our-predictions-%28The-Singularity-is-coming%29

We are reaching a step in our tech progress that might be equal common for all species, the singularity.

This effect may be comparable with supernovas type 1a, no matter in what part of the universe they occur, they all explode with the same intensity, in the singularity case, we (or the AI) reach all the possible knowledge that can be know in a very short time, after that we (or the AI) may find a hiden true which dictates a common end (no matter what kind of "being" you were before).

Or maybe, if there is not more goals, we (or the AI) lose our purpose. Maybe there is not life without purpose, and maybe; that is the meaning of life.

[Brethern]

Why? Do you think that human adage of "Kill, or be killed" applies to any sentient species? That's very anthropocentric

Animals fight all the time, it's not a human centered thing as far as we know it's a nature thing.

I'm not saying we should kill any aliens that come to our planet, doing so is a good way to end up working in an alien mining operation, but we should be approaching this situation as you would if you were walking through central park at night. Don't announce your location and don't go running towards anyone who does.

[Aethon]

This effect may be comparable with supernovas type 1a, no matter in what part of the universe they occur, they all explode with the same intensity

I'm not at all sure anymore that 1a supernova are a reliable standard candle. IMO some of the wackyness of the standard model comes from biased measures of cosmological distances.

http://iopscience.iop.org/article/10.1088/0004-637X/803/1/20/meta;jsessionid=38E89CF97D27C1AF107A6DEA4EA73154.c1

http://www.centauri-dreams.org/?p=11732

http://phenomena.nationalgeographic.com/2014/08/28/type-1a-supernovas-cosmic-candle-mystery/

If the singularity is inevitable for intelligent races, then the galactic center is probably not the place to look for a signal. Heat is the enemy of computation. Intelligent machines may find the cold, dark depths of molecular clouds, only a few degrees above absolute zero to be more suitable for their needs. But now we're getting into alien sociology and our data set there is, to say the least, sparse.

Edited August 30, 2015 by Aethon

[Jolbucley]

If someone tens of thousands of years ago decided to set off a really bright radio pulse in our direction from the center of the galaxy, it’s conceivable that we could receive that signal. But in order to keep energy consumption reasonable (and I use the term “reasonable†very loosely) the signal would have to be a tight beam, implying that the sender expected somebody to be listening at the right time and in the right place, or else just got astronomically lucky. The signal wouldn’t be very strong by the time it got here since space has plenty of things that could interfere with it; plus, the galactic core is a fairly bright region of space, so even if we picked up the signal we would have to sift through the naturally emitted signals we detect and notice the anomaly.

But why would any alien civilization with sufficient technology to send that sort of radio signal ever bother? We aren’t broadcasting loud radio messages every which way like we used to; the window during which we shouted loudly enough for even the nearest star systems to hear lasted only a few decades, which means that even if a civilization developed around the Alpha Centauri system, it would have to be in about the same stage of development we are for us to hear it, assuming it does what we did  screaming into space for a few decades before directing more of our communications energy inward. High-energy radio signals waste a lot of energy, which is what another civilization would detect: the energy that we want to cut down on emitting. After all, why spend money to blast our talk shows into the next star system, let alone a quarter of a galaxy away? We have no reason to expect alien civilizations to behave any differently.

Loud, eavesdroppable communication is an immature phase of communications technology, and with the speed-of-light delay, it’s unlikely anybody in the galactic core would intentionally try to contact us. If they have the technology to know we’re here, it would probably involve the transmission or reception of information superluminally, in which case sending radio signals now makes no sense; by the time they get here, we’ll either be long gone or operating on other means of communication. Is contacting a relatively primitive race like us really worth the bother? Couldn’t they wait until we have an analogously causality-violating transmission technology to contact us? And if the denizens of the core somehow pick up our radio transmissions once they arrive, which is exceedingly unlikely, we can’t expect a response for another forty-odd-thousand years; our would-be correspondents might even realize that and not take the trouble to reply at all.