Science Forums 2

[Freethinker]

Originally posted by: TeleMad

Here's the idea in a nutshell. Picture yourself in a regular elevator. Naturally, you are standing on the floor because gravity pulls you down and holds you to it. Now, imagine that the elevator is not here on Earth but is instead out in deep intergalactic space, where there is no gravity. You are floating around inside the elevator. But if the elevator were to be accelerated at 9.80 m/s^2 in a direction towards the top of the elevator, you would find yourself standing on the floor and being held there by the accelerating elevator. You'd feel a force on your feet equal to the force of gravity if you were on Earth and the elevator motionless. The two situations are indistinguishable. Even if you perform an experiment, you can't tell the difference. For example, if you had a ball and dropped it, in either situation it woud fall towards to the floor with an acceleration of 9.80 m/s^2. Einstein concluded that since there is no experiment you could perform that would tell which is the case - on Earth and motionless or out in space and accelerating - that gravity and acceleration can be considered equivalent and gravity can be transformed away by replacing it with a suitable acceleration (or vice versa).

This and a good number of other thought experiments are covered in his own book on the subject "Relativity (The Special and General Theory)" Albert Einstein.

Not only do you benefit from sharing his understanding and specific apporach, but just to actually read HIS words as he felt they best explained his ideas. Great book.