Letter: A proposition about the use of the word 'theorem'

From Doug Clark, Edinburgh, UK

Leah Crane says that because an estimate by physicist Maximiliano Isi of the mass and spin of a black hole is based on the no-hair theorem, which holds that no information about a black hole beyond its mass, spin and electrical charge is visible beyond its event horizon, this suggests that the theorem is correct (21 September, p 6).

A theorem is a mathematical proposition not self-evident but proved by a chain of reasoning, a truth established by reason and based on accepted axioms.

I suggest that this “theorem” would more accurately be called a conjecture.

The editor writes:

We have to call things what they are universally called and this is the language cosmologists use.