The BBC reports in Alien life in Universe: Scientists say finding it is 'only a matter of time' that Scotland's Astronomer Royal, Catherine Heymans, has said

We live in an infinite Universe, with infinite stars and planets."

Am I the only person to feel that this is such a gross simplification as to be inappropriate from somebody whose job is, fundamentally, to get things right?

She apparently goes on to say that

"And it's been obvious to many of us that we can't be the only intelligent life out there,"

which, whether I agree with it or not, I can't help but label as the "No true Scotsperson" fallacy.


1 Answer 1


We don't know the topology of the whole universe. If the universe has a density critical density of $\Omega>1$ it could be "finite but bounded" but if $\Omega\le1$ then it could be open and infinite. Actual measurements give $\Omega = 1.00 \pm 0.02$. In other words, in other words, it appears to be flat and infinite (but could be very slightly curved).

As the universe is very close to flat (if not exactly flat) it has a scale much larger than the observable universe, and may well be infinite. A flat, infinite cosmology is consistent with observations.

Whether Prof Heymans should have parenthetically added "Infinite, (or very much larger than the observable universe)" is surely a matter of opinion. While "infinite" has a specific mathematical definition, in non-technical use it sometimes means "beyond our ability to measure or calculate."

It is not a "No True Scotsman" fallacy. There is no attempt to dismiss a falsifying counterexample by arbitrarily excluding it.

  • $\begingroup$ I don't like criticising somebody who appears to have significant credentials in the field, and there's obviously a possibility that her comment's been mangled by an editor somewhere in the BBC. $\endgroup$ Sep 30, 2023 at 7:40
  • $\begingroup$ Well possibly. I think most of your question is a matter of opinion (and so unanswerable) $\endgroup$
    – James K
    Sep 30, 2023 at 7:44

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