All Questions
188
questions
-1
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4
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5k
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Does time exist without Gravity?
If you travel the universe and move into an area where there is negligible gravitational influence, does time stop? As an observer, would this be like watching someone cross the event horizon of a ...
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 ...
0
votes
1
answer
116
views
Time required to reach Black Hole's Event Horizon from outsider perspective?
Let's imagine a pair of particles that is entangled. One (call it $P_1$) is released and then falls to a black hole from a distant $x_0$, (for example $x_0=5r_s$) and velocity $v_0(=1/2c)$, while the ...
- 6,112
0
votes
2
answers
100
views
Thought experiment circumventing finite speed of light via relativity of simultaneity - what's wrong?
I just watched this video regarding block universe: https://www.youtube.com/watch?v=wwSzpaTHyS8&t=676s and it provoked the following thought experiment:
Let's assume two observers, O1 and O2, at ...
0
votes
3
answers
130
views
Can you tell who is moving through time? [closed]
In relativity, there is no way to tell if you are moving through space. So, if you were inside of a box, there would be no way for you to tell if you were moving or not. However, can you know who is ...
- 9,500
1
vote
2
answers
72
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Train example of special relativity
My friend Eric is at the center of the train. The train is moving forward. The front end and back end of the train flash a light at the same time. From Eric's perspective, both light arrives at him at ...
- 35.4k
1
vote
1
answer
117
views
How would a spacecraft travelling near light speed say 0.9c compensate for time dilation in radio communication from spacecraft to earth?
For a spacecraft travelling at 0.9 c for 5 seconds, only 5 seconds would have passed for an observer on Aircraft, while 26.31 second would pass for a stationary observer watching from Earth.
In a ...
- 530
9
votes
5
answers
2k
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A bar that appears straight in one reference frame appears bent in another?
Is there a relativistic effect at play that explains the following thought experiment, that I am unaware of?
The apparatus depicted in the image has two straight bars in the middle emitting light from ...
- 6,112
2
votes
3
answers
240
views
Relativity, Lorentz Transforms and the time it takes to perceive
I've been working a bit at understanding relativity a bit more, and understanding Lorentz transformations. I want to make sure I understand the meaning of a Lorentz transofmration, and when to use it ...
- 6,112
1
vote
5
answers
497
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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 ...
-1
votes
1
answer
178
views
Can we consider that the photons that were not and will never be detected live in a zero-dimensional space? [closed]
According to Einstein’s theory of relativity, any particle traveling at the speed of light experiences no passage of time. It follows that if a photon travels through space then within any two points ...
- 207k
0
votes
2
answers
86
views
Time desync with light delay: can we still "look into the future"?
I'm reasonably familiar with special relativity and its effect such as time desynchronization, but I'm having trouble understanding how these effects come into play when we also consider the time for ...
- 26.4k
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 ...
- 207k
9
votes
5
answers
8k
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Why is causality preserved in special relativity?
PART 1:
I was reading the article Relativity of simultaneity Wikipedia. I couldn't understand this line:
"if the two events are causally connected ("event A causes event B"), the causal order is ...
- 207k
1
vote
1
answer
145
views
How to calculate positions when switching reference frames in a Minkowski spacetime diagram
The below Minkowski spacetime diagram includes three worldlines, where B is the observer and has a rest frame. A and C both have a velocity of 0.71c.
I then created a second diagram where worldline A ...
- 12k