[lunar11 (OP)]

Hi.
Recently two Earth-like planets were discovered, which did once lie in the 'habitable-zone', but now are too hot.
My question is lets say that there was intelligent life on one of these planets once, and that they were sending radio waves in all directions, including our direction. It would take about a 1000 years for the signals to arrive to Earth. Would these signals still be arriving even if the life-forms died out millions of years ago.

I could be thinking Monolith (as in Space Odyssey 2001)

[CliffordK]

NO.

1000 years is just a drop in the bucket as far as time.
Plus, the light we're seeing all originates at the same time, or at most within a few hours difference depending which side of the star the planet is located on.

Given time, I believe Humans could engineer weather modification systems that would save Earth from any solar-based warming cycles up to the sun entering the Red Giant phase, at which point, we may be able to eek out a living on some of the more distant planets and moons.

So...  say, 2 billion years from now, if Earth is no longer in the "habitable zone", we may still find life here.  And, may also find life on the other planets in the solar system that would not otherwise be predicted to support life.

Anyway, so my point is that if a planet could have supported "intelligent life" equal, or beyond what humanity has today.  Then if they were forced to adapt to a slow, but severe climatic change over thousands or millions of years, it is likely that they would have been able to adapt, either by modifying their planet's climate, or moving to a nearby planet or moon.

[syhprum]

I read this as a technical question as to over what distance radio commuication is possible, SETI quote a figure of 1000 ly between Aricebo size antenna and multi megawatt transmitters with 1 Hz bandwith .
This of course assumes the antenna are pointing in the right direction and the doppler shift is well known which might be a little difficult to arrange.

[CliffordK]

I read this as a technical question as to over what distance radio commuication is possible, SETI quote a figure of 1000 ly between Aricebo size antenna and multi megawatt transmitters with 1 Hz bandwith .
This of course assumes the antenna are pointing in the right direction and the doppler shift is well known which might be a little difficult to arrange.

A 2-way communication with a civilization 1000 lightyears away would be most difficult.
If you asked them a question, it would take 2000 years (1000 years each way) to get a response back.  I.E. one would have to wait 50 to 100 generations to get the response back.

While one might take a while to decide how the planet "Earth" should respond to such information, it would also take 2000 years to ascertain that both ends were in fact listening to the conversation, subtracting at most 100 years that Earth has been broadcasting radio and TV which may "leak" at very low power.

[syhprum]

I doubt if simple leaks from broadcasts would get to any other solar systems you need real directed power

[CliffordK]

I doubt if simple leaks from broadcasts would get to any other solar systems you real directed power

Does SETI broadcast?

We have been sending signals to our various satellites, both near and far.