Cosmic,
That's the water hole of the MB narrowband search or am I still lost?

Joe,
But 1% would still be nearly 3 billion suns. To me that is an awfully large sample of stars. If it's not in there we may be alone.

--edit--
Thanks again for the reference. I gotta hang on 'til 2020! :-)

Joe,
How much is 'very much'? Just ballpark, guess.
...

Well, assuming e.t. has a more sensitive receiving system than Arecibo (something like the Square Kilometre Array or better), the radio pulses sent by the Arecibo Planetary Radar could be detected out to 1000 light years or so. The Milky Way galaxy has a diameter of about 100000 light years, we're about 27000 light years from the center so star systems are spaced relatively far apart. In short, much much less than 1% of the star systems in our galaxy are near enough for detection of our strongest radio signals.

                                                                   Joe

Technically, a signal goes on infinitely. However, you end up with attenuation and interference from other locations in space and you get to a point where the signal you sent out blends in with the background "hiss."

In open space, like between two galaxies, the attenuation is significantly less than within a galaxy full of dust and gas and stars.

And then you end up with another huge "what if?" problem: was the signal that was sent out omni-directional, or was it focused in one direction? An omni signal takes astronomical (pun sort-of intended) power to travel even halfway across the galaxy, but a focused, directional signal needs much less power to reach the same distance.

[edit: To add more clarification, even with astronomical power (a star) broadcasting light (a radio frequency, technically) in an omni-directional pattern, we have trouble seeing ones on the opposite side of our own galaxy, but we can see individual stars from Andromeda, for example. The space between galaxies is much closer to being an empty vacuum than the space between stars within a galaxy. Sure, we can see the stars on the other side of our galaxy if we change how we look for them (infrared or x-ray), but that's only because most stars broadcast practically the whole electromagnetic spectrum, so there are many ways to "see" them. And also, when a star goes supernova, or turns into a pulsar, there is a focused beam of energy coming from the poles and we can see that practically across the entire universe. Omni vs. directional.

And the reason detecting radio signals becomes so difficult is not just omni vs. directional, but unlike a star, radio signals have a very narrow frequency range, so there's really only one way to look for it, and that is to be listening on the same frequency range.]

Arecibo is a directional antenna (both for transmit and receive). Of course, it all depends on the head that is installed, as well, because if you have a head that is designed in a certain way, you can end up transmitting or receiving on an arc that covers something like 40 degrees.

So it makes more sense to send out directional signals because they need much less power and are more likely to travel longer distances with less attenuation. Like when we send signals up to the satellites in orbit, only something like 5-10% of the broadcast beam actually hits the receiver on the satellite--the rest of it goes on out into space beyond. It would be a 1-in-many trillions shot of being 30,000 light-years away at the exact time and place to be able to even detect that narrow, focused beam that was broadcasted into space.

And even if you DO happen to be in that exact spot at the right time, there will have been so much attenuation that even with very sensitive and advanced detection equipment, you might not even be able to detect it at all. And if you were able to detect it, then you have to figure out what kind of signal it may have been, how to decode it, and then try to make sense of it.

Long story short.. it's finding a needle in a haystack, when the haystack is the size of a planet, and you don't know what a needle is or even looks like. Basically.. you're looking for something that doesn't look like everything else. My understanding of the way we're searching is using the frequency of hydrogen, because it makes the most sense. Kind of like in Contact, a deliberate signal was sent and focused right back at us using the frequency of 'hydrogen * pi' because.. "math and science are the only truly universal language." 1+1=2 in any language, here on Earth or on the other side of the universe.




So that's my take on it. Maybe that answered your question, maybe not. And I realize some of my facts may not be 100% accurate, but they are generally close enough for the context of this discussion.

---

Linux laptop:
record uptime: 1511d 20h 19m (ended due to the power brick giving-up)

Joe,
How much is 'very much'? Just ballpark, guess.
--edit--
By radio transmissions you mean like our radio, tv and radar?
If we spent $50 million a year how strong of a chirp-chirp signal could we
send out. I mean how many light years out would it be good for if they had a simple Ariciebo.

I just looked at your link. Thanks, very good.

Some good technical background is in part 1.2.3 of the old Usenet SETI@home FAQ. In essence, the question boils down to how much power the distant civilization beams our way, and that FAQ answer makes it clear that the kind of power we have used for radio transmissions cannot reach very much of our galaxy.

Some good technical background is in part 1.2.3 of the old Usenet SETI@home FAQ. In essence, the question boils down to how much power the distant civilization beams our way, and that FAQ answer makes it clear that the kind of power we have used for radio transmissions cannot reach very much of our galaxy.

However, the amount of power which could possibly be used by a more advanced civilization doesn't have any absolute bound. The technology to gather and use something like the total output of a star can at least be thought about. Or consider something like finding a way to add artificial modulation to the pulses being generated by a Pulsar, IOW using a radio source which already reaches huge distances and making it carry a message.

                                                                   Joe

Let's see if I can ask this question without making a total ass of myself.

If MB can see out to an effective distance of say,for our discussion, an area including 100,000 stars, how far out can AP see it's chirp-chirp signal?

If I get some answers, I may have to rephrase my question, if I am capable of doing that.