🚀 go-pugleaf

In article <3s6f2t$9ed@geraldo.cc.utexas.edu>,
 on 20 Jun 1995 12:31:25 GMT,
 Gene Preston <gene.preston@access.texas.gov> writes:
>>The idea I have mentioned here, that relatively speaking, the earth may
>>well be stationary and the universe rotating around it is valid and there
>>is no way we can tell what is happening from our point of view.  Everything
>>can be interpreted in either way...
>
>This is garbage and violates about every physical law I can think of.
>What century are you from?
>
>....gene preston

I didn't see the rest of this thread (and given the list of newsgroups
to which this is going, I'm not particularly disappointed) but this one
point IS valid.  Look up "Newton's Bucket" or "Mach's Principle", or if
you are into General Relativity, the "Lens-Thirring Effect".

If you assume that gravity is like electromagnetism, moving objects
generate the gravitational analogue of a magnetic field, which turns
out to correspond to rotation (in the same way that the ordinary
gravitational field corresponds to acceleration).  When anything
moves in this field, it is deflected in the same way as a moving
charge is deflected in a magnetic field.

It turns out that if you claim that you are standing still and it is
the universe which is rotating, the gravitational rotational field
of the universe causes things to move in strange ways which
correspond exactly to the Newtonian centrifugal and coriolis forces
experienced in a rotating frame of reference.

In this sense, all rotation and acceleration might effectively be
relative to the universe, and this idea is known as Mach's Principle.
(It is not clear whether General Relativity fully supports this idea,
although Einstein very much hoped that it would).

Of course, we CAN detect rotation locally, and we usually find that
it matches up with rotation relative to the "fixed stars", so for
practical purposes we can define what is rotating and what is not
over a large area of space.  However, if we were very close to a
very large mass, or a very rapidly rotating mass, we would find that
a locally non-rotating system would nevertheless be rotating
relative to the fixed stars, and in such cases we could not use the
simplifying assumption that rotation is absolute.

Jonathan Scott
jonathan_scott@vnet.ibm.com  or  jscott@winvmc.vnet.ibm.com