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Re: Sir Hoyle on Copernicus and Ptolemy



Savinainen Antti wrote:

> perhaps I did not ask clearly enough. Sir Hoyle stated that (my
additions in
> brackets):
>
> "Today [1973] we cannot claim in any physically meaningful sense that
> Copernican theory
> [i.e. the Earth revolves around the Sun; not other way round] would
be right
> and Ptolemy's theory would be wrong.
> These two theories have no difference whatsoever from the point of
view of
> physics."
>
> Copernicus proposed that the Earth is not "fixed", it revolves around
the Sun.
> Is this correct or not?
> Or is it *just* a matter of reference frame?

Note: According to English tradition (and
there's not a lot that's more traditional than
knighthood) our hero is called either Prof. Hoyle
or Sir Fred -- never Sir Hoyle.

Anyway ... This doesn't look like a physics
question to me. I think we all know the physics.
Is this just an exegesis of the quote from Sir
Fred? If the question is whether the quote is
exactly right, I can answer without looking at
the text. No, it isn't exactly right. Nothing
anybody has ever written is exactly right,
especially if you take a couple of sentences
out of context.

You can always find fault. If somebody writes
"two plus two makes four" I can think of a
context where that's not true.

Certainly Ptolemy's theory as a whole is not
isomorphic to Copernicus's theory as a whole.
But we knew that.

At the other extreme, Sir Fred wasn't 100%
wrong, either. There are a number of valid
points he could have been making. I'm not
exactly sure which.
-- Large-scale homogeneity of the universe
implies _anywhere_ can be chosen to be the
"center" and therefore nowhere has any special
claim to be the center. The universe is
probably not quite so homogeneous as Sir
Fred thought it was, but neither is it as
inhomogeneous as Copernicus thought it was.
-- Modern physics can deal with non-inertial
reference frames.
-- ???

Exegesis is a poor substitute for physics.

Can you rephrase this as a physics question?
Recall today's gravimeter question, where there
was a specific, well-described piece of
apparatus whose behavior could be analyzed.