Two conflicting theories suggest on the one hand that the complex biological nature of Earth is rare or even unique in the universe or conversly that life is inevitable just about everywhere, given a few constants.
Are we alone in the universe or are there countless planets with complex life and intelligent species within our astronomical neighbourhood?
How likely is it that that not very far away in our own galaxy that there are sentient beings asking this very same question?
Dear Barry,
I lean on the side that life on earth is very typical. Our sun is typical, planets like us are most likely typical, life on earth did appears as soon as water was liquid. I expect life to take about 3 billion years to become multicellular on all these planet and to take about 500 million years to become intelligent and about half million year either to become stable and extinct. In the case of the planet where intelligent life become stable, I expect it to become planetary integrated life form within a few thousand years. I expect to be typical as well. I also expect these planetary life form to become integrated at a higher galactic level with instantaneous communication channel as soon as they reach the planetary life form level. The answers to all your question are only sure at that level where communication is established. But I think we have it built in in our life form already the compulsion to go towards this normal life development at the higher level of life scale. The Universe is still very young and I am not sure if the integration at the galactic level is already established or if we will be among the first member cell of this life form.
Considering that apparently our solar system is in no way special, indeed the Sun is a very typical star and also the planets appear to be more or less common from what we know about exoplanets, it would be odd to assume that only at one place life emerged. Then again the time where the constituents of our life (carbons) have existed, has not been so long in the universe.
That being said I doubt there are hundreds of species evolved in the galaxy. Some may survive the battle of evolution to actually become starfaring, but many might not. Then again considering the numerous species on Earth that are intelligent, e.g. dolphins, elefants, certain birds and apes, makes it unlikely that no intelligent life form at all does exist next to us.
So in short, I am sure there are other intelligent life forms out there. Yet, I doubt we will ever have meaningful contact with them, let alone meet - unless a fundamental part of Einstein's theory of relativity is wrong: that information cannot travel faster than the speed of light, or we find a way to circumvent that.
A student of Democritus, Metrodorus of Chios, in the fourth century BCE, wrote: ‘’To consider the Earth as the only populated world in infinite space is as absurd as to assert that in an entire field sown with millet, only one grain will grow’’
A new slant on the question.
https://www.researchgate.net/post/Intelligent_Life_in_Our_Galaxy