[ExI] Pesky Neutrinos

[john clark]

I wrote:
"But you ARE undergoing acceleration because you are in a gravitational field, you are standing on the surface of the Earth undergoing an acceleration of 1g. Your friend is far from the Earth so he's not in a gravitational field, but he could be accelerating for other reasons." 

On Nov 2, 2011 Adrian Tymes wrote:


"This acceleration is canceled out by the normal force of the Earth's surface"

If you are in a rocket accelerating at 1g is the acceleration canceled out by the normal force of the rocket's floor?

"relative to the Earth, you are not accelerating." 

As far as time and space are concerned gravity and acceleration are equivalent. If you are in a closed box there is no way to know if you and the box are just sitting on the Earth's surface or if you are in intergalactic space being accelerated by a rocket at 1g, and any clock you have inside that box doesn't care which is true. 

GPS satellites orbit the Earth ever 12 hours at a speed of 8700 mph, because they are moving so fast the atomic clocks in them run 7200 nanoseconds per day SLOWER than a clock on the Earth's surface. But because they are further from the Earth's center and thus in a weaker gravitational field they run 45900 nanoseconds per day FASTER than a clock on the surface. So putting both figures together we would expect to see the clock in the satellite to run 45900−7200= 38700 nanoseconds per day FASTER than a clock on the ground, and this is indeed exactly what we see. The weaker gravity actually has over six times the effect on the clock than the rapid speed of the satellite does, and its in the opposite direction.   

 John K Clark

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