And finally, in case noone has noticed, WE are running out of time. Even if the good folks in M31 detected us in a million years when our signals get that far, and I am wrong about the end of science and they are able to come here, they will NOT find little biological human beings here. As I pointed out earlier today in an answer: electronic technology has advanced more than 9 orders of magnitude in the last 4 decades. We have gone from devices in our homes with a few tubes in them to the computer you are using which has hundreds of billions of active components. The beauty of this technology is that is extensible by duplication, unlike propulsion technology. Another 4 decades and you will have in your home a machine with several orders of magnitude more components. Easily enough to put sentient, self aware robots in your home, my office, factories, farms, Mars or wherever. These robots will be our competition. We will lose. Not by crass violence but by natural succession. It is these robots (or whatever succeeds them) that the hypothetical folk from M31 will discover when (and if) they get here, not us.
Therefore, space and time are against us, and guarantee our status as lone sentients. We cannot fathom the space that separates us from any life that MIGHT exist. Neither can we span the time that separates us from POSSIBLE contact.
So as always: we ARE alone.
Cheers!
Edit:
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Whoa guys, I only just drafted up a reply. Quality takes time.