Re: [asa] geocentricity

----- Original Message -----
From: <mrb22667@kansas.net>
To: <asa@calvin.edu>
Sent: Friday, July 06, 2007 4:42 PM
Subject: Re: [asa] geocentricity

Quoting George Murphy <gmurphy@raex.com>:

> Merv -
>
> My choice of coordinates doesn't force anybody else to do anything. You can
> also use any coordinates you choose. & if we each make measurements
> correctly we'll find that our results for distances, times, velocities &
> various other things will differ, but we'll be able to agree on the laws that
> the phenomena obey if those laws have been formulated in accord with the
> relativistic transformation rules.
>
> Using a particular coordinate system doesn't mean that one has to be in any
> particular place or move in a particular way. It's simply a choice of a way
> to describe the world for a particular problem.

Of course - classical relativity (from Galileo) is easily understood and
accepted. My point was that, with regard to celestial mechanics, some choices
are vastly simpler mathematically than others. And I know that 'simpler'
doesn't equal 'proven', but it does often (and especially in this case)
equal 'almost certainly closer to reality'. Nobody proves anything except
mathematicians - and then only after accepting postulates. It is evidence and
fruitfulness towards further inquiry that seems to overwhelmingly rule out
geocentricism, unless one relishes the practice with more difficult math.

Evidence and fruitfulness toward further inquiry points toward the idea that the laws of physics should be generally covariant - i.e., they should be in a form which is valid for all coordinate systems. This means, among other things, that a geocentric system is, in principle, as good as a heliocentric one for all problems of celestial mechanics.

A heliocentric system is much more convenient in practice - i.e., makes calculations simpler - than a geocentric one for many, though not all, problems of celestial mechanics. But for calculating the motion of an earth satellite it would not be more convenient.

But "more convenient" by no means implies "closer to reality." If physics gets us any glimpse at reality at all, surely the basic laws of physics get us closer to it than the essentially arbitrary methods we choose to make our work easier.

Shalom
George
http://web.raex.com/~gmurphy/

To unsubscribe, send a message to majordomo@calvin.edu with
"unsubscribe asa" (no quotes) as the body of the message.
Received on Fri Jul 6 21:16:37 2007