Question: What is the probability of an inhabitable planets like earth existing?

Alice Harpole answered on 10 Mar 2016:

We have seen several exoplanets now that appear to be similar to our Earth – similar in size, orbiting stars similar to our Sun, and probably rocky like the Earth (i.e. not gas giants like Jupiter or Saturn). However, our telescopes are not currently powerful enough for us to tell if these planets have atmospheres, or what these atmospheres are made of. This is very important if life is to survive. If there is no atmosphere, then the planet will be far too cold and there will be nothing to shield its surface from the powerful radiation of its star. If the atmosphere is too thick or made up of the wrong gases, then it could produce a very extreme greenhouse effect that would end up heating the surface up so much that nothing could survive there.

However, given that we know planets are pretty common (at least in the our galaxy), and there are thought to be about 1,000,000,000,000,000,000,000 stars in the universe, I think it’s almost certain that there is a planet out there with suitable conditions for life!