All Questions
8
questions
12
votes
5
answers
2k
views
Could relativity be consistent if there are multiple light-like fields with different invariant speeds?
My understanding of real physical theory of electromagnetism goes like this:
The Maxwell equations can be used to derive the speed of light;
$$\nabla\cdot\textbf{E}=0$$
$$\nabla\cdot\textbf{B}=0$$
$$\...
- 5,148
1
vote
2
answers
132
views
Do events very far away happen in a different timeline?
I am not sure how to ask this question in a concise manner so I am sure somebody out there explained it but I cannot seem to find it.
So I recently watched some videos explaining that $c$ not only ...
- 119
1
vote
1
answer
112
views
How to show mathematical equivalence between the idea of relativistic mass and the geometric explanation of why massive objects can't reach $c$?
I've frequently seen two different explanations for why, in SR, it's impossible for an massive object to reach $c$:
As a massive object approaches $c$, its kinetic energy starts being converted to ...
- 2,327
2
votes
3
answers
444
views
Why does $ds^2=0$ for a light signal's worldline in general relativity?
I know that in special relativity, the invariant interval $ds^2$ for a light signal's worldline is $$ds^2=\eta_{\mu\nu}dx^\mu dx^\nu=0$$ where the flat metric $\eta_{\mu\nu}=\text{diag}(-1,1,1,1)$.
...
- 4,235
0
votes
1
answer
415
views
Difficulty in understanding the three classes of events of light-cone
Recently I'm reading Chapter 2: Space and Time of A Brief History of Time. The paragraph that follows the light cone says:
Given an event P, one can divide the other events in the universe into ...
- 103
0
votes
2
answers
51
views
Why do we locate stars based on the light we see from earth?
Mapping space from our milky-way to Laniakea and the CMB, we always put a star or galaxies position from the light we see in that 3d coordinates of the universe.
But really if a star or galaxy we look ...
1
vote
1
answer
461
views
Are all time-like and light like separated events causally connected?
It is well known that all causally connected pairs of events are either time-like or light-like separated. Is the inverse -'All time-like or light like separated events are causally connected'- also ...
user191891
0
votes
1
answer
302
views
Is gravity instantaneous? [duplicate]
I want to know if (hypothetically) a star appears out of nowhere at a certain distance (say 20 light seconds) away from me, how long will it take for me to get the feel of it's gravity? Will I know it ...
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