All Questions
Tagged with spacetime reference-frames
197
questions
8
votes
3
answers
1k
views
We know there is no aether, so what is being dragged in frame dragging?
I have read this question:
In stellar frame dragging what is the 'frame'?
There are several questions on this site about frame dragging, all of them take the frame that is being dragged as an ...
8
votes
5
answers
1k
views
Do you always experience the gravitational influence of other mass as you see them in your frame?
You see a galaxy far away. That galaxy is attracting you with a certain amount of gravity. I'm wondering if the gravity influence of the galaxy on you, as measured by you, always ends up being what ...
7
votes
5
answers
1k
views
How does brain perceive time dilation due to gravity?
Einstein's General Relativity says gravity warps spacetime. Consider a hypothetical scenario:
A person travels into space from Earth.
He landed on a different planet in some far off galaxy where time ...
2
votes
6
answers
984
views
Can there be a theoretical synchronised ‘now’ moment at all points across the universe?
Einstein’s relativity rejects the notion of a universal ‘now’ moment. It underlines how the concept of ‘now’ is compromised due to time passing at differing rates in differing frames of reference, ...
2
votes
1
answer
161
views
When you are in a gravitational field, do object far away get physically closer to you as you get closer to the mass?
An observer A is close to a black hole and an observer B one light year away. They are both remaining at constant radial distance from the black hole. A is at 2 Rs away from the center of the black ...
4
votes
1
answer
112
views
How to relate Riemannian and Lorentzian tetrad fields on the same manifold/spacetime?
Consider Gibbons and Hawkings paper wherein a Riemannian metric $\overset{\mathcal{R}}{g}_{\mu\nu}$ and everywhere well defined normalized line field $l_{\mu}$ on spacetime $M$ may be used to ...
13
votes
7
answers
4k
views
Does the "Andromeda Paradox" (Rietdijk–Putnam-Penrose) imply a completely deterministic universe?
Wikipedia article: http://en.wikipedia.org/wiki/Rietdijk–Putnam_argument
Abstract of 1966 Rietdijk paper:
A proof is given that there does not exist an event, that is not already in the past for ...
1
vote
3
answers
175
views
Seemingly equivalent linear form of the Sagnac effect
This is a derivative of the question regarding the Sagnac effect. Judging from the metric $ds^2=-dt^2+(rd\phi)^2$ for a constant $r$ for this question, it should be no different from that on a line ...
2
votes
3
answers
193
views
Sagnac effect viewed in the rotating frame
Consider the Sagnac effect. It is quite simple viewed from the rest inertial frame what the time difference should be. However, if viewed from the frame fixed to and rotating together with the emitter/...
3
votes
3
answers
537
views
Why is proper time $d\tau$ equated to spacetime length $ds$?
Follow-up to this question: Why proper time is a measure of space?.
The selected answer to me tells us why proper time is an invariant quantity, but I'm still wondering why we equate it to $ds$. Can ...
1
vote
5
answers
497
views
Is relativity of simultaneity an "observer issue"?
There are some threads about this, but some answers seem to disagree.
First, this is what Einstein said on this matter:
The light rays emitted by the flashes of lightning A and B would reach him ...
2
votes
2
answers
609
views
How to define the proper time of a photon?
I'm writing a paper about the motion of photons near a Schwarzschild black hole. At some point there's a derivative of the Hamiltonian of the system with respect to time $\tau$. I need to explain what ...
0
votes
0
answers
26
views
Question on Example 5.9 of Prof. Hartle Gravity textbook
I'm reading the Gravity Hartle book (ed.2003) and I'm having trouble with the question in the last part of Example 5.9 - Frequency Measured by an Accelerating Observer. More specifically the problem ...
0
votes
1
answer
216
views
Acceleration/gravitation vs velocity and the Twin Paradox
I see in Professor Pogge’s explanation
http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html dec. 2020.
that
“Because an observer on the ground sees the satellites in motion relative to ...
0
votes
1
answer
175
views
How is special relativity explained by general relativity?
To be more specific about this, I am under the below assumptions and then will explain my question further. Please let me know if any of the assumptions are incorrect.
(1) Special relativity describes ...