The Fermi Paradox: A 10 Step Guide To Finding Aliens

8. The Size Of Time

Another thing we have to take into consideration is that fact that Space Is Old.

People often talk about the size of space being a factor in the likelihood of flagging down a passing alien, but a lesser discussed variable is the size of time.

The age of the universe is roughly 13.8 billion years (give or take the odd 59 million) and humans, for example, have only been transmitting radio signals for about 100 of those years. Cosmologically speaking, we're basically still in the womb. So, when considering the probability of detecting intelligent life in the universe, we have to take into account the likelihood that a civilisation would arise close enough to us to detect at the same time as us, or at least with some crossover.

To figure out how likely that is, we have to figure out how long a civilisation will typically transmit signals into space. It could be that the natural progression of an intelligent species is to try and contact other for a bit then give up, continuing to exist in blissful silence for another billion years, meaning that we'd have to catch them in that one, contactable window.

We also have to take into consideration that there is an essential time limit on the lifespan of any civilisation, but more on that later.