Is there really life on other planets?

Nobody knows. If you forced me to give an opinion one way or the other, I’d say yes, and probably on millions of planets. But who cares about an opinion? There is no direct evidence. One of the great virtues of science is that scientists know when they don’t know the answer to something. They cheerfully admit that they don’t know. Cheerfully, because not knowing the answer is an exciting challenge to try to find it.

One day we may have definite evidence of life on other planets, and then we’ll know for sure. For now, the best a scientist can do is write down the kind of information that might reduce the uncertainty, might take us from guesswork to an estimate of likelihood. And that, in itself, is an interesting and challenging thing to do.