3
votes
1answer
72 views

If dark energy is accelerating the expansion of the universe, why can't I feel it?

Based on the Lambda-CDM cosmological model, our universe is not only expanding, but is accelerating in its expansion. However, the Equivalence Principle would suggest that inertia manifests itself in ...
0
votes
0answers
35 views

Mario Livio's book on symmetry and the relationship between gravity and acceleration

In his book: The Equation That Couldn't be Solved Mario Livio explains the equivalence principle in laymen's terms. I took the statement on page 209: The force of gravity and the force resulting from ...
14
votes
2answers
345 views

Do accelerated charges radiate or not?

This questions has been asked all over the net (here included) but I can't find a satisfactory answer or discussion. Some say it does not radiate if the acceleration is caused by a uniform gravity ...
1
vote
4answers
179 views

Equivalence principle and acceleration vs a gravitational field

I picked this up on the net: Einstein came to realize the principle of equivalence, and it states that an accelerated system is completely physically equivalent to a system inside a gravitational ...
5
votes
2answers
220 views

Did people realize that gravity accelerated things before Einstein's elevator thought experiment?

I'm reading about the (very near) equivalence of gravitational mass and inertial mass in my undergrad GR course, and the text (Lambourne) describes this equivalence as the inspiration for Einstein's ...
2
votes
3answers
255 views

Does GR imply a fundamental difference between gravitational and non-gravitational acceleration?

Does the equivalence principle imply that there is some fundamental difference between acceleration due to gravity and acceleration by other means (because there is no way to 'feel' free fall ...
1
vote
4answers
444 views

“Weight” of moving object in a car collision

From time to time I see safety warning about keeping loose items in your car. The last warning used a 2kg object, and claimed that if a collision occurred at $50{km\over h}$ it would have a weight ...
3
votes
4answers
687 views

Why acceleration is not relative in General Relativity?

I was thinking of it, If I say: "I'm moving at a velocity $v_1$ relative to a reference frame $M$ then the acceleration will be the derivative of $v_1$ relative to the reference frame $M$." In other ...
0
votes
1answer
174 views

Is the result of (every) research on acceleration equivalent to gravity?

Is the result of an experiment on acceleration equivalent to another experiment in a gravitational field? If I have an experimental conclusion from research under uniform acceleration, can the ...
1
vote
2answers
148 views

Can acceleration feel like constant gravity for indefinitely long?

So here's the setup: I'm in a spaceship, without windows as always, and the ship is accelerating upwards at a constant rate of $1\,\text{g}$. So inside the spaceship it feels like I'm being pulled ...
0
votes
2answers
176 views

How is space ship's acceleration perceived if the acceleration is perpendicular to the velocity?

Spacecraft in orbit around the Earth are constantly accelerated by the gravitational field of Earth. That's why the spacecraft ($m \ll M$) is in an (elliptical) orbit around the centre of gravity of ...
0
votes
4answers
1k views

Questions from elevator ride

I like to play inside the lift (elevator). For instance, there are bars attached at the side of the lift, and I like to hold my body up using my two hands on the bar. I realised that I actually feel ...
0
votes
2answers
228 views

Why equivalence principle is principle and not law?

We can prove that the inertial mass and the gravitational mass should be the same (equivalence principle) from the $f=mg=ma$ then $g=a$, so we have equivalence law! But why we said equivalence ...
2
votes
5answers
2k views

Why Gravity attracts all objects with the same speed?

Why Gravity attracts all objects with the same speed? Is this question was solved? What is the exact answer?
1
vote
1answer
243 views

Accelerating elevator?

If your in an elevator accelerating downwards faster than gravity, would you be pushed up to the ceiling? Since gravity cannot match the acceleration of the elevator, you're wouldn't be able to move ...
12
votes
7answers
4k views

Would it help if you jump inside a free falling elevator?

Imagine you're trapped inside a free falling elevator. Would you decrease your impact impulse by jumping during the fall? When?