The Fermi paradox: a lunchtime remark that will not go away

The story is that over lunch at Los Alamos in 1950, in a conversation that had drifted onto flying saucers, Enrico Fermi asked: where is everybody?

The anecdote is thin and the accounts differ. The argument underneath it is not thin at all, and it has survived seventy-five years of attempts to dispose of it.

The argument

The galaxy is about thirteen billion years old and about a hundred thousand light years across. A civilisation expanding at even a thousandth of light speed — slower than we could manage now, using technology we can describe — would cross it in about a hundred million years.

That is under one per cent of the galaxy’s age. So if technological civilisations arise at all often, the galaxy should have been thoroughly settled long before Earth had multicellular life.

It has not been. That is the paradox: not that we have heard nothing, but that we appear to be living in an empty galaxy that has had ample time to fill.

The families of answer

They are rare. Some step between chemistry and technology is far harder than it looks — the origin of life, or the eukaryotic cell, or intelligence itself. On Earth each took a very long time.

They do not last. Civilisations reliably destroy themselves or collapse within a window too short to expand. This is the answer nobody enjoys.

They are there and we cannot see them. Not transmitting, not expanding, or expanding in ways we would not recognise. This overlaps with the observation that our own detectability is falling as our technology improves.

They are hiding, or we are contained. These are unfalsifiable, which is not the same as false but does place them outside what evidence can settle.

We are early. Star formation will continue for a very long time, and the universe may simply be young — most planets that will ever exist do not yet exist.

Why it belongs on this site

Because it is the strongest argument against the assumption underneath a great deal of UAP writing. If the galaxy were full of travelling civilisations, we should be seeing evidence far less ambiguous than lights on infrared cameras.

That cuts both ways and is worth stating carefully. It does not prove nothing is here. It does mean the quiet, marginal, endlessly-contested character of the evidence is a fact that needs explaining rather than explaining away — and Vallée’s objection to the spacecraft hypothesis is essentially the Fermi paradox restated at close range.