I am highly skeptical about the UFO phenomena that has been an abiding craze since WW2. It strikes me that if intelligent beings went to the enormous trouble of travelling (at a very minimum) thousands of years to cross the galaxy to get here (and why here?), then they would have more to do and say than play a strange game of hide and seek. Ditto even if the craft are automated, without biological life forms present. Such a vessel would be programmed to do something other than make brief enigmatic appearances or abduct the locals to perform oddly primitive experiments.

But there is a possibility that intelligent species have evolved elsewhere in the galaxy or wider universe, either in the past or in our present. It is possible that many civilisations have come and gone. Equally, in my estimation, that we are alone. Completely.

Assuming that the former is true, it would also be reasonable to suppose that intelligent life forms who have come to master the resources of their planet would also have passed through similar technological and scientific pathways as we have. They would all, at some point, have learnt how to split the atom and manufacture nuclear weapons. Futurists posit nuclear war as one of the potential 'great filters' that civilisations must pass through to survive. Others include, for example, meteor strikes, gamma ray bursts, ageing stars and catastrophic climate change.

We are on the cusp of two of those filters it would seem. How humans handle these matters is critical to whether we continue as a species or hand on a dead planet for cosmic visitors to puzzle over.