All Questions
42
questions
0
votes
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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 ...
8
votes
1
answer
357
views
The synchronized clocks on earth's surface: at which observer's rate are they beating?
From what I understand, the time rates (I'm not speaking about absolute times) of all clocks on earth's surface are synchronized. This means that, say, a mobile phone's clock is generally not beating ...
- 3,753
0
votes
2
answers
119
views
Time in the Standard Model of Cosmology
Beyond a formal preference for background independence, what is stopping us from setting cosmological time as a de facto universal timeline, analogous to newtonian absolute time? General relativity ...
- 1
1
vote
0
answers
106
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Energy is the time component of 4-momentum in SR: Proof as per R. Wald's book
This is an excerpt fom R. Wald's book on General Relativity (page 61). I'm not able to understand how he deduces that $E$ must be the time component of $p^a$ with only the assertions made before this ...
- 107
-3
votes
1
answer
99
views
Would time dilation increase the distance between objects? [closed]
Two objects are moving towards a gravity well. They are at $x$ distance from each other and moving at a fixed speed. The gravity well is massive enough for the objects to experience significant time ...
- 141
0
votes
2
answers
75
views
General Relativistic version of the Lorentz factor
In curved spacetime, the Lorentz factor is different than that in flat spacetime.
Is there any expression that gives the Lorentz factor for any arbitrary metric tensor?
user355398
2
votes
2
answers
97
views
Is it possible for a Ricci-flat manifold to have a negative energy measured by distant observers?
Supposing that there is a stationary sphere made of regular matters, the external spacetime geometry can be described by the Schwarzschild metric, which describes a spacetime with vanishing Ricci ...
- 1,455
0
votes
0
answers
27
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Is it correct to say that acceleration slows the frequency of an oscillator?
My question is based on differential aging or differential timekeeping due to, 1) increased speed, and 2) proximity to center of gravitational field. As far as I know, both involve acceleration, and ...
- 1
0
votes
2
answers
159
views
Observers in General Relativity: do transformations happen between two different observers or between two local coordinates both of the same observer?
In my understanding of general relativity, I am a little confused. Could someone please clarify this:
Given the definition of a manifold with its collection of subsets(patches) and mapping functions, ...
- 306
0
votes
1
answer
209
views
What is the definition of an asymptotic observer?
I can't find the definition of it in Wikipedia or in books on my bookshelf.
- 898
1
vote
0
answers
170
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Rindler Observers
In the process of transition from STR to GR, I'm trying to understand what Rindler observers actually are. Here is how one of the questions from our assignment defines them:
If the distance between B ...
- 67
0
votes
3
answers
499
views
Where in the universe does time pass fastest relative to time on earth?
It is my understanding that time essentially moves slower in higher gravitational fields relative to time on earth. Conversely, in lower gravitational fields, time passes faster relative to earth. Is ...
2
votes
1
answer
149
views
How can the infalling observer see the event horizon to retreat in front after the observer crossed it (and can't even notice it)?
I have read this question:
so looking toward the singularity, you see the horizon retreating from you as you fall in - even after you've already crossed the horizon.
Are black holes naked ...
- 29k
1
vote
0
answers
37
views
Does the clock tick faster when falling? [duplicate]
I just read this answer that explains that the time dilation due to the gravity and the time dilation due to velocity are the same thing.
Does that mean that, if I fall from the top of a skyscraper on ...
- 143
0
votes
0
answers
36
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If frequency shift is positive then how to interpret it?
Let say lightning is happening at $r=r_{A}$ from center of gravity and our observer at $r=r_{B}$ with $r_{A}>r_{B}$ then if we get frequency shift is positive (by considering let say schwarzschild ...
