What exactly is "exact" (was Clean Singleton Docstrings)

[Steven D'Aprano]

On Tue, 19 Jul 2016 10:36 am, Rustom Mody wrote:

> I recollect — school physics textbook so sorry no link —
> that in the Newton gravitation law
> f = -GMm/r²
> 
> there was a discussion about the exponent of r ie  2
> And that to some 6 decimal places it had been verified that it was
> actually 2.000002

Because gravitational forces are so weak, it is very difficult to
experimentally distinguish (say) an exponent of 1.999999 from 2.000002 from
2 exactly.

Most physicists would say that an experimental result of 2.000002 is pretty
good confirmation that the theoretical power of 2 is correct. Only a very
few would think that the experiment was evidence that both Newtonian and
Einsteinian gravitational theory is incorrect.

(Newton, for obvious reasons; but also general relativity, since Newton's
law can be derived from the "low mass/large distance" case of general
relativity.)

But it's an interesting hypothetical: what if the power wasn't 2 exactly?





-- 
Steven
“Cheer up,” they said, “things could be worse.” So I cheered up, and sure
enough, things got worse.