|IDEA BY:||Martin Roberts||LOCATION:||Other||CATEGORY:||Science/Medical|
|IDEA BY:||Martin Roberts|
The main postulate of General Relativity is the Equivalence Principle which states that the force due to acceleration is the same as the gravitational force. In fact we can eliminate a uniform gravitational force by choosing a suitable accelerating frame of reference. If we consider an accelerating box in space, any occupant of the box would conclude that he/she was in the presence of a gravitational field. This field would act downward from what would be perceived as the ceiling to what would be perceived as the floor of the box. Any occupant of the box would also conclude that a photon emitted from the perceived floor to the perceived ceiling would be slowed by the gravitational force. The reason being that if we choose a non-accelerating frame of reference, then the photon would have a longer distance to travel. The theory behind black holes is that it is possible to reverse the direction of light with a gravitational field, so it should also be possible to reverse the direction of a photon with an accelerating frame of reference. We can see however that this is not possible because the ceiling of the box would have to travel away from the photon faster than light which is not possible accordingly to special relativity.