So… is the existence of life common in the Universe? Can an assertion that life probably does exist elsewhere be construed as a valid scientific theory, or can it be viewed as an assumption only?
The answers seem to be: probably; and such an assertion might be viewed as a valid, but borderline scientific theory- based on probability, which in turn may be based on observational evidence.
Anyone reading this post knows that our Earth is a mere speck in the vastness of the known universe. The Sun is a very average yellow dwarf star. According to the latest estimates, there are between 200 and 400 billion stars in the galaxy we reside in (the exact number will most likely never be known because of the gargantuan amount of gas and dust obscuring our view). How many of these stars have planetary companions? It’s safe to say that a large percentage of them do.
How many galaxies are in the known universe? Recent estimates are as high as 500 billion. The Hubble Deep-Sky camera photographed a small area of the sky a few years back- an area 1/150th the apparent size of the moon. 3,000 galaxies were counted in that small area alone!
As far as we know, the universe elsewhere is composed of the same elements that we, our Earth, our sun, and our galaxy are composed of. The physical laws of nature, as we know them, seem to apply everywhere in the observable universe, as far as we have seen.
It happened here… why not elsewhere? It doesn’t even have to be carbon-based… but we’ll save that for a future post.
And what about the probability that some “supreme being” created the whole universe just for us? One can’t help but be purely subjective on this, but I say… ZERO.