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TenBillionDollHairs t1_iyb7s96 wrote

  1. Advanced civilizations probably don't use omnidirectional signals because it's a massive waste of energy. Their transmitters and receivers are probably set up for signals to be sent in one direction like a laser. You could even transmit power like this.
  2. You could detect such a tightbeam signal from very far away. There is even a theory referenced here that the famous WOW! signal was a tiny bit of leakage from a power transmission.
  3. If alien civilizations do want to be found, one way they could make it easier to find them would be to beam a signal at a cosmic event which they are certain any civ with telescopes will look at. That way, any civilizations on the other side of the event from your beam will open up their data and say "huh, that shouldn't be there."
  4. (It's also possible that they would send a signal to that event for reasons other than communication, I guess like a very patient version of radar? but anyway)
  5. In other words: I, an advanced alien, have spotted a binary neutron star pair in the next galaxy over. I know it will take my signal 250k light years to get there, but that happens to be exactly when these two stars will end their dance in a kilonova. However, I know any fresh young civs will definitely be awed by the big explosion it makes, so they will all turn their telescopes at it. Being ancient and alien and inscrutable, I send this signal even though I will likely be long dead before it's even partway there. 250k years later, the signal arrives at the massive explosion.
  6. Another half million years later, someone on Earth---which happens to be more or less exactly on the other side of that binary star pair from our old alien friend---records this explosion, and then notices there's an artificial signal buried in there on top of the stuff that looks like every other explosion. If they talk to aliens anything like we do, we're left very disappointed by some mathematical universal constants and a picture of what they looked like naked. (We could probably actually learn some tech by figuring out how they made such a powerful signal but I like my version better)

anyway this was my best tl;dr

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imhereforthespuds t1_iycarl1 wrote

Or there is a civilisation out there that just roams around looking for this extraordinary and rare events, and sends out information just enough to make nearby civilisations aware and respond. Then bam, feeding frenzy.

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danielv123 t1_iycpzuf wrote

How do you beam data at a cosmic event so that it passes the cosmic event right as it happens? Or are we talking a continuous beam here?

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TenBillionDollHairs t1_iycs0hv wrote

I mean I guess continuous on a short time scale, but not continuous like "for 1000" years. Maybe a decade? I don't know how long binary neutron star explosions last

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InevitableSignUp t1_iyd4bzc wrote

Upvoted for the disappointment in point 6, but I have a question - does their laser have to be coming from the opposite direction? Or would we be able to pick up a laser coming through what we’re looking at from the side? And would it hypothetically be traceable back to its point of origin by ‘tracking’ it back along the beam?

… without the half a millions years of delay being anything to worry about, of course.

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