All Questions
37
questions
4
votes
2
answers
371
views
Are objects in an uniform field inertial?
It is currently understood that gravity is not actually a force, and a fact that is often used to show this is that an object in free fall doesn't "feel" that it is accelerating and is thus ...
- 365
25
votes
4
answers
7k
views
If gravity is not a force, then how come gravitational assists work?
I have learned about general relativity and how gravity arises from spacetime curvature. And I have always been taught that gravity is not a real force in the sense that
$$\frac{dp}{dt} = 0$$
And from ...
- 1,896
-2
votes
1
answer
243
views
A problem in the light beam experiment of the equivalence principle?
Could someone tell me where i'm wrong? The light beam experiment of the equivalence principle which was the mind experiment that made Einstein deduce the curvature of light around heavy objects, has a ...
user348262
2
votes
3
answers
184
views
Weight in Interplanetary Space
How is weight zero in interplanetary
space? The Moon is orbiting the Earth because of the gravitational pull of earth. Then gravity must exist in interplanetary space too. So any body in space must ...
- 19
0
votes
1
answer
77
views
Defining acceleration in gravity-free space
Without information from outside a closed spaceship, an astronaut cannot distinguish A from B.
A) In gravity-free space, the floor accelerates upwards at $a=g$ and hits a dropped watch.
B) On earth's ...
- 65
2
votes
0
answers
58
views
Is there a way to know if you accelerate in empty space or in a uniform gravitational field?
If I'm in a room that accelerates through empty space uniformly I won't measure tidal forces. The situation is the same as standing on an infinite massive plane. So I could think, while looking ...
0
votes
1
answer
283
views
How can a person inside from a veiled and free-falling elevator distinguish whether he is in an inertial or non-inertial frame?
From wikipedia: "A non-inertial reference frame is a frame of reference that undergoes acceleration with respect to an inertial frame", according to that statement, I would say that an ...
- 339
1
vote
3
answers
115
views
Newtonian physics and equivalence principle: a doubt on acceleration and gravity
First of all, the famous Einstein's elevator experiment is quite clear in my head, both of versions.
But now, consider the following:
Suppose then you wake up inside a car that is traveling in ...
20
votes
14
answers
6k
views
Why don't you feel gravity the same way you feel a car's acceleration? [closed]
If you are in an accelerating car or spaceship you feel an apparent force pushing you backwards, which as I understand is due to your own body's inertia (it wants to keep its current velocity but the ...
- 317
0
votes
1
answer
104
views
A problem regarding light bending
My professor in his lectures has stated that a consequence of Einstein Equivalence Principle (EEP) alone is that light bends in a gravitational field.
The proof went as follow: Imagine to be a free ...
- 4,577
13
votes
6
answers
2k
views
Is spacetime curved in a near-earth-free-falling-object's frame of reference?
If I float motionless in outer space, I will measure spacetime to be approximately flat.
By the equivalence principle, I will get flat spacetime if I am free falling near earth.
Is this right? ...
- 131
1
vote
1
answer
110
views
Strong gravitational field equivalent to accelerated frame
I have recently learned about the equivalence principle and what it says is that( If I have understood it properly) the trajectory of the particles will be the same irrespective of the properties of ...
- 135
1
vote
1
answer
78
views
Can one identify the presence of a gravitational field?
This is a slight modification to the Einstein's relativity thought experiment that I have not been able to find a discussion on.
Suppose that you are in a spaceship with no windows. Is there any ...
- 11
-4
votes
1
answer
773
views
If gravity is a fictitious force, could there be a real force counterpart for it atleast locally? [closed]
I wanted to ask the same question in different ways.
1.Consider the below example whereby we have a man M in a box B in outer space. B is acted upon by a force, F. B moves in direction of F. As the ...
- 73
2
votes
1
answer
173
views
How much of general relativity does the equivalence principle actually imply, why is it different?
From EP we have that gravity is not a force but a pseudo force, i.e
an inertial force due to a gravitational field an accelerating a body
independantly of its mass, in other words, the trajectory of ...
- 91