« on: Yesterday at 04:54:09 »
Kryptid: The point I was trying to make is that an acceleration of 9.8m/s2, 50 billion kilometres from earth or other gravitational influences,is in no way representative of the gravitational force on earth. Instead as Janus points out the force that would be experienced by the spaceship would be the same force that it would experience if it were on an earth that possessed a radius of 50 billion kilometres ! This reinforces my original conjecture that in the absence of a large mass close by, Einstein's thought experiment makes no sense. He is using gravity as an explanation of itself.This has no bearing on the equivalence principle.
An example illustrating the principle is this:
Take your ship, put it just above the surface of the Earth firing its engines with just enough thrust to hold it hovering above the Ground at a constant height. An occupant in the rocket standing on a scale would weight the same as he would standing of the surface, if he drops an object, it falls to the floor, etc.
Now take that rocket and move out to 50 billion miles from the Earth. But still firing its engines at the sane thrust as before. Now this of course will be more thrust than the pull of gravity from the Earth and the rocket will accelerate away from the Earth. An occupant inside the ship however will still weigh the same on a scale in the ship and objects will still fall towards the floor of the ship just like they did when the ship was hovering just at the surface of the Earth. Relative to the rocket, objects in this accelerating rocket behave just like they would in a gravitational field.
This is the gist of the equivalence principle. The importance of this is that you can imagine how something like light would behave in the rocket in the second scenario For example, light emitted from the tail would appear red-shifted to an observer in the nose, or if fired sideways to the acceleration would trace a curved path relative to the ship, and then use this to conclude conclude that it would exhibit the same behavior in a gravity field (be red shifted climbing against it or have it path curved by it.
You would also conclude that an observer in the nose of the accelerating rocket would measure a clock at the tail as running slow, and by extension that someone higher in a gravitational field would measure a clock lower than them as running slow.