However we do come back to Fermi's Paradox: the universe is 13800million years old. So far we have no evidence a probe has reached our star system. Where are they? Maybe we just haven't stumbled across one yet. Or maybe life really is very rare?

Well there are actually some pretty convincing explanations for for the Fermi Paradox. The one I like most is that despite the 13800 million years, we're pretty early for complex life, and we may just be the first technological civilization in the Milky Way.

The theory goes that while there are a lot of older stars out there, there aren't a lot of 3rd generation stars. When some stars get to the end of their life, they collapse and then go supernova, leaving behind a dust cloud in which other stars can then form. Here's the thing, many heavy elements are only produced through nuclear fusion during a supernova. (Basically everything heavier than iron, about 3/4 of the periodic table). So that second generation of stars contain more heavy elements within the star. When the second generation goes supernova, more heavy elements are created.

Life exists on earth thanks to all of the complex chemical reactions that can take place on earth. But all that may only be possible because we're a 3rd generation solar system with all our fancy heavy elements, and 3rd Gen star systems are relatively new, we're quite early on the scene.

So because of that, we're certainly an early civilization, and we might be... the first.