What is the probability that there is life in the universe aside from earth?
The probability is 99%
The universe is what we humans would like to call it, "endless".
And there are millions of galaxies containing thousands of planets which are in the habitable zone of their stars (in the habitable zone it is not too cold and not too hot for life to exist).
Scientists have already observed many planets in just our own galaxy that are in the habitable zone. That means, if there is water on those planets, it is flowing water, flowing water is needed for life to exist.
It is quite unlikely that Earth is the only planet with life in the universe.
It's possible that if we would have lived closer to the center of the galaxy (where there are more solarsystems) we would have met aliens already.
I am almost 100% sure that there is other life in the universe, in our own galaxy.