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Originally Posted by alaskaboy
The science documentary I watched the other day said 55 billion years at the speed of light. The human mind can't even grasp that type of distance. In reality, it's like a non reality when you think about it.
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Whether it's 30 billion or 55 billion light years across doesn't really matter. The argument you're making is the universe is so big that there has to be a civilization more advanced than us out there.
Possibility 1: we're it in the Milky Way, but there are advanced civilizations in other galaxies. The UK's version of Dr. Neil de Grasse Tyson,
Dr. Brian Cox, points out there are a lot of accidents in the evolution of life on earth that led to us. There was only single-celled life for the first 2.6 billion years of earth's history. Then, multi-cellular life arose, likely (Cox says) because of a happy accident. If an asteroid had not wiped out the dinosaurs, the mammals wouldn't have become dominant. The dinosaurs were around for 190 BILLION years without showing any sign of developing high intelligence. So his argument is: we're it in the Milky Way, but there may be advanced civilizations in other galaxies.
Let's suppose there's a civilization in the Andromeda Galaxy that's more advanced than us technologically. Andromeda is 2.54 billion light years from the Milky Way. That means they wouldn't be aware of us for at least 2.54 billion years from now plus however long it takes for us to develop a high enough technology that our presence would be detectable from that kind of distance.
What that means practically is: we're isolated from other galaxies by extreme distance. They might as well not exist from our perspective - so pragmatically, we're alone.
Possibility 2: there are hundreds to a few thousand advanced civilizations in the Milky Way.
Michael Garrett speculated at the International Astronomical Congress a few years ago that there are maybe 3,000 technological civilizations in the Milky Way. If this were the case, they'd be on the average 1,000 light years apart. Which means it will be roughly a thousand years before our nearest neighbor detects us, and if they send a message back, we'll receive it 2,000 years from now -- assuming we're still around.
What that means practically is: if anyone's out there in the Milky Way, it will be a few thousand years before we hear from them -- assuming they can detect our presence at all.
Possibility 3: there are a lot of highly technological civilizations in the Milky Way, and the closest one is close enough that they have received our radio and TV broadcasts from 100 years ago.
What that means practically is: we should have heard from them by now, since there are so many of them; that's the Fermi Paradox: if there are a lot of advanced civilizations out there, where are they?. Unless you assume they're avoiding us (which we have zero evidence for), we're left with Possibility 1 or 2.
I personally suspect Cox is too pessimistic, and Garrett is too optimistic. That would mean no one will realize we're here for tens of thousands of years, and a message from them would take twice that long. Imagining warp drive or "subspace" communication is an easy way out, but we have no more evidence those things are practically possible than that the Milky Way is full of Star Wars characters just dying to meet us. And I hope I'm wrong, and it's Possibility 3.
EDIT:
Another interesting article on the topic with yet another opinion:
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Whitmire calculates that at this moment, if they indeed exist, there may now be as many as a million current tech civilizations in our Milky Way galaxy alone. But if his paper is correct, we will likely never meet them.
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