[time-nuts] gravity, space and time
Chris Albertson
albertson.chris at gmail.com
Fri Dec 12 23:43:09 EST 2014
A VERY accuracy clock is actually a good sensor for gravity. This is
because the clock's speed changes with strength of the gravity because of
Einstein's General Theory. So if you have two very good clocks that are
separated if one starts to run faster then we can assume time itself is
running faster.
If the relative rates of two clocks change periodically then you have
(maybe) a periodic gravity wave.
The clock is the best sensor for measuring the rate if time. The rate of
time changes with gravity.
The problem is that you need many insanely good clocks spread over some
large area and a way to compare those clocks. I think well past the
current state of the art.
Perhaps you are confusing accuracy with sensitivity. When you want to
> measure something you need a sensor. If you have a choice you pick the one
> that's most sensitive.
>
> The very reason atomic clocks so accurate is that they are poor sensors. I
> mean, if you want to measure gravity, a plain quartz oscillator is much
> better. A pendulum clock is even better. Or just drop a rock off a
> building. You want something macroscopic, not something atomic. To measure
> those alleged space time ripples, you want something that measures motion,
> not something based on quantum mechanics.
>
> Consider that LIGO, the coolest gravity experiment in the world, is
> essentially a mirror hanging by a thread. It's a macroscopic, mechanical
> experiment.
>
> If you still don't believe me, here's a quick comparison of two gravity
> sensor technologies:
>
> 1) You can measure g to one digit of accuracy by dropping a coffee cup off
> a 4 foot table. The equation is d = gt²/2. If the cup takes 0.5 seconds to
> fall, then the result is g = 2d/t²= 9.7 m/s². Nice result; easy experiment.
>
> 2) To make a similar measurement of g using atomic clocks, you do
> something like http://leapsecond.com/great2005/tour/. The equation is
> df/f = t/T = gh/c². Here t (time dilation) was 22 ns, T (elapsed time) was
> 42 hours, h (altitude gain) was 1340 meters, c (speed of light) is
> 299792458 m/s, so the result is g = tc²/Th = 9.7 m/s². Nice result; hard
> experiment.
>
> What's wonderful about the universe is that the two methods agree. But
> which method could easily be improved if you wanted many more digits of
> resolution, or wanted to measure short-term variations in g?
>
> /tvb
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--
Chris Albertson
Redondo Beach, California
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