Why does only one object feel accelerated?

[Ascenxion]

In terms of general relativity, what does this question mean?

Thanks.

 

[Al68]

In terms of general relativity, what does this question mean?

Thanks.

Does it mean "why does an object feel a force acting on it"?

 

[jtbell]

One object? Which object?

 

[Ascenxion]

Well, I found this question in the http://en.wikipedia.org/wiki/Acceleration" topic in Wikipedia, and I was confused about its meaning.

After completing his theory of special relativity, Albert Einstein realized that forces felt by objects undergoing constant proper acceleration are indistinguishable from those in a gravitational field. This was the basis for his development of general relativity, a relativistic theory of gravity. This is also the basis for the popular twin paradox, which asks why one twin ages less when moving away from his sibling at near light-speed and then returning, since the non-aging twin can say that it is the other twin that was moving. General relativity solved the "why does only one object feel accelerated?" problem which had plagued philosophers and scientists since Newton's time (and caused Newton to endorse absolute space). In special relativity, only inertial frames of reference (non-accelerated frames) can be used and are equivalent; general relativity considers all frames, even accelerated ones, to be equivalent. (The path from these considerations to the full theory of general relativity is traced in the introduction to general relativity.)

Thanks.

 

[A.T.]

In special relativity, only inertial frames of reference (non-accelerated frames) can be used and are equivalent; general relativity considers all frames, even accelerated ones, to be equivalent.

I don't know what they mean by "equivalent frames of reference", but in GR still only inertial frames have the same physical laws: local experiments give the same results in all of them. The new thing in GR is that free falling frames in a small region of a gravitational field are considered inertial too, so you can use SR there.

So GR is not making accelerated frames equivalent to inertial ones, but it redefines what an inertial vs. accelerated frame is, regarding gravitational fields.