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MalabarJag · 10-17-2017, 07:40 PM

(10-17-2017, 07:04 PM)TheO-LineMatters Wrote:
(10-17-2017, 06:21 PM)MalabarJag Wrote: What happens in a distant galaxy is immaterial, so the number of stars is not infinite. Realistically, if we're talking about extraterrestrials actually visiting Earth we should limit this to our own galaxy, about 100 billion stars, most of them much smaller and cooler than the sun.

There are two possibilities, either spacefaring intelligent life is common, or it is uncommon. If it is common the Earth would have been colonized by extraterrestrials millions of years ago. If it is uncommon the odds of another race appearing within the last million years in a 13 billion year old galaxy are rather low. Counting humanity as a spacefaring race that would mean that for 12.999 billion years there was no intelligent race in the galaxy, and now in the last .001 billion years there are two.The fact that we are here pretty much invalidates the possibility that space aliens are visiting Earth.

Why?

Why would a race in a distant galaxy choose to visit a planet in our galaxy? Even assuming faster than light travel speeds (and I can't imagine undertaking interstellar curiosity trips at sub-light speeds) there's a lot of real estate to investigate before ever coming to the Milky Way galaxy.

Maybe you can include the galaxies in the local group and other nearby galaxies along with the Milky Way, but that only increases the number of possible extraterrestrial home planets by a factor of a hundred or so at most, and doesn't change the argument. It just makes the meaning of common vs. uncommon slightly different. Wherever they supposedly came from there wasn't an earlier race that colonized Earth, so they would have have to arisen at cosmologically the same time as we did.

The Sci-Fi stories of other races interacting with humans are enjoyable, but Asimov's galactic empire where humans are the only higher life form in the galaxy is much more likely.

"Why should I give information to you when all you want to do is find something wrong with it?"