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Re: [Phys-L] another DIY relativity experiment



On 05/20/2016 04:16 AM, Bob Sciamanda wrote:

Now we find that clocks are gravity dependent.

I still think it is a mistake to describe the physics
that way. That's the usual TV-show explanation, but
it's not the best physics explanation.

We do not say that odometers are path-dependent; why
should we say that clocks are path-dependent? If you
carry odometers by two different paths from Point A
to Point B, you get different answers, but that does
not mean there's anything wrong with either instrument.
Each measures the righteous distance along its path.

not just some clock, but ALL clocks, and ALL processes (eg., your
heartbeat) are gravity dependent.

That seems like a tremendous coincidence. I don't
believe in that sort of coincidences.

Rather than saying all processes are affected, it is
simpler to say that *none* of them are affected. Use
Occam's razor. Every clock and every bit of physics,
including biophysics, measures the righteous time
along its path.

You can't say that one clock is ticking «faster» than
it should unless you have some a_priori standard to
compare it against, which you don't. Anything you
might compare it against behaves the same way.

In a world where all paths were almost straight, you
might develop a false intuition that said odometers
always agreed with each other, independent of path.
You might be surprised the first time somebody found
a sufficiently-circuitous path to produce significantly
different odometer readings. However, the result does
not mean that either odometer is malfunctioning; it
just means your intuition was wrong.

Now it turns out that in the real world, ordinary
paths are so close to parallel (in four dimensions)
that the elapsed time between Event A and Event B
is "usually" independent of path, approximately, if
you don't look too closely. However, you should
*NOT* take this as evidence that the elapsed time
"should" be path-independent.

Bottom line: Clocks are like odometers, not like
rulers. Each clock measures the righteous time
along its path.