Believe it or not, we used to think life was much more common than we think now. Over time we have been forced to realize life is really not very common at all.
We used to think there were Martians that might one day invade us, or Venutians or some other advanced civilization living on a nearby planet within our own solar system.
We were disappointed, I think, to discover life nowhere else as of writing other than right here on Earth. Scientists really had hoped to find at least some kind of foscilized remnant of life on Mars, but we haven’t even done that. No life has been detected on any other planet than our own.
Why is that?
Well, it turns out there are a lot of factors that go into having an inhabitable planet other than a planet being in the Goldilocks region of a star. One of the big advantages we have is our moon. We have an unusually large moon tidally locked to Earth. Without the moon, everybody dies!
We don’t know how the moon came to be, but the theories are pretty amazing. One theory is that a Mars size planet collided with Earth and spewed all kinds of rocks into orbit which later coalesced into the moon. This is called the general impact therory. The chances of those circumstances happening on another planet, anywhere, is slim.
There is a real possibility that life exists nowhere else other than here. We’d love it to be otherwise. Sadly, so far, it isn’t.