All Questions
Tagged with spacetime reference-frames
197
questions
8
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5
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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 ...
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2
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1
answer
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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 ...
- 171
1
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3
answers
175
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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 ...
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2
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3
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193
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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/...
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0
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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 ...
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1
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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 ...
1
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1
answer
90
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What does hypersurface of simultaneity exactly mean?
HSS - "Hyper Surface of Simultaneity"
Listening to different sources online I understood that HSS for a observer represents the points that are at same moment of time.
Consider a 1d world. ...
4
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1
answer
112
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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 ...
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0
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51
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Geometric definition absolute velocity in affine spaces
currently I am reading the following paper by Halvorson and Clifton (https://arxiv.org/abs/quant-ph/0103041) where they try to argue that localizable particles are inconsistent with relativistic ...
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2
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Do all observers see the same curved spacetime -- or would that be a (prohibited) preferred inertial frame? [duplicate]
My question -- pardon if not asked in the most incisive scientific prose
Do all observers see the same curved-space time?
Let me clarify:
Given that objects traveling at different relative speeds will ...
0
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2
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104
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Justification of string breakage in Bell's Spaceship paradox from observer's frame
In Bell's Spaceship Paradox, are there any direct observations that the stationary observer can make that would justify the breaking of the string without taking into consideration as to what's taking ...
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41
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4
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Rotate an object about the time axis
Is there a notion of rotating an object about its time axis? I'm not sure if this question totally makes sense, but it seems intuitive to me that an object with dimensions in the three spatial ...
- 521
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3
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How to prove: Are perpendicular coordinates (wrt to relative velocity) unchanged (or only scaled) while deriving the Lorentz Transformations?
Thank you for helping with this question and I'm sorry if it's kind of stupid.
TLDR: In many textbooks and other derivations deriving the Lorentz Transformations, they omit coordinate axes orthogonal ...
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1
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Is distance irrelevant to time if two events are in the same inertial reference frame? [closed]
Assuming that there is some observer "O" at location 0, and there are two events A and B, with B occurring 1m farther from A. Both A and B are equipped with two synchronized clocks reading ...
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3
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174
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Trajectory of light send from a moving box [closed]
In a closed box in inertial motion a ball bounces up and down vertically. Apart from this movement, the ball is motionless relative to the box. The trajectory of the ball seen by a stationary observer ...
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2
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75
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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
0
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1
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120
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Stress-energy tensor in different reference frames and spacetime curvature
The components of the stress-energy tensor are different in different reference frames. Also there is no universal time, so values of energy will be different in different reference frames.
Via the ...
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1
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146
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Why is the flat spacetime of special relativity not a linear vector space? [duplicate]
Why is the flat spacetime of special relativity, not a real linear vector space? It seems to satisfy all the axioms for a set to form a vector space. I mean adding to spacetime points $(t_1,\vec{r}_1)$...
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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 ...
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2
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250
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What is concept of left region of rindler space-time?
A accelerated object follow a hyperbolic path in a Minkowski spacetime diagram. Minkowski spacetime has two regions: left (I) and right (II) regions of Rindler spacetime, as it is shown in the picture ...
- 209
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4
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140
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Simultaneity of events
Apologies, this thought has been bugging me and I am... Simple
Consider two observers.
One on Earth (stationery) One travelling away from Earth at some
appreciable % of c
If the spaceship sent a ...
- 3
1
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2
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250
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Four vectors and coordinates
Hartle, gravity. Chapter 5
A four-vector is defined as a directed line segment in four-dimensional flat spacetime in the same way as a three-dimensional vector (to be called a three-vector in this ...
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2
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63
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Does a person in relativistic circular orbit have the same age as a stationary person at the centre? [duplicate]
Consider a circular orbit whereby a spaceship travels around near the speed of light.
Say the radius of this orbit is such that the angular velocity is low.
An observer is placed at the center of the ...
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4
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Twin Paradox (SR): How can we express the comparative length of arbitrary world-lines mathematically?
The simplest and most intuitive way I have found so far for explaining which twin ages less in the Twin Paradox, is that it's the twin who's world-line is the longest (if it's the longest in one ...
- 200
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2
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In spacetime what is the time $t$ on the $ct$ axis?
In spacetime, I understand that we multiply time by the speed of light to deal with homogeneous distances over the four axis, space and time.
But what does $t$ refers to precisely? Where is $t$ ...
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74
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Minkowski Diagrams and Synchronized Clocks [duplicate]
While using Minkowski diagrams for studying spacetime and time dilation, I came across a problem that seems like a paradox to me, but may actually just be from a lvl of understanding.
Imagining two ...
5
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4
answers
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In the twin paradox or twins paradox what do the clocks of the twin and the distant star he visits show when he's at the star?
In the twins paradox of relativity one twin stays on earth while the other travels to a star ten light years away, and then immediately flies back. Because his rocket travels at just under the speed ...
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1
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111
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At what constant speed should I travel one light-second to make my time and a stationary person's time 1 second off?
at what constant speed should I travel one light-second to make my time and a stationary person's time 1 second off?
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537
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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 ...
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402
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Physical Meaning of Pullback metric vs. Effective Spatial Metric
Consider a Riemannian Manifold with a metric tensor $g_{\mu\nu}$ and coordinates $(t, x^i)$. Let us assume that the spacetime is stationary, so $\partial_t g_{\mu\nu} = 0$. At a fixed coordinate time ...
- 709
3
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2
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532
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Using time dilation to find universal frame of reference
Before I ask this question, I just want to clarify that I am by no means an expert and that this question most likely came about due to my ignorance on the subject. If this is the case, please let me ...
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3
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419
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How "accurately" does the CMB tell the age of the universe?
Just to clarify, I am not asking about clock accuracy per se at all. The reason I am asking this question stems from the fact that on this site, most questions about the age of the universe answer ...
- 29k
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What if the Twin Paradox use the "day time" and "night time" on earth as their age reference?
I've searched this site, I found a similar question here but not exactly like mine.
So I can't understand the Twin Paradox when I use the "day" (bright time) and "night" (dark time)...
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403
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How are spatial coordinate systems in physics defined?
Grothendieck once asked "What is a meter?" (https://golem.ph.utexas.edu/category/2006/08/letter_from_grothendieck.html). This innocent sounding question, made me to think about how ...
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If we find a star exploding 100 light years away, that means it happened 100 years before? [duplicate]
So can someone please help me with this? Can someone make the answer as simple as possible?
So my question is if we see a star exploding like 100 light-years away, that means that star exploded 100 ...
4
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3
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270
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Can we think of space as any kind of aether in any way? [duplicate]
I am not asking about the Michelson-Morley experiment in any way. I am specifically asking, if space (including the fields that QFT describes) itself can be thought of as any kind of aether that ...
- 29k
6
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2
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750
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Can a Kerr black hole be viewed as a Schwarzschild black hole by changing the frame of reference?
In a local universe empty of any matter except a Kerr black hole and an observer, that observer is spinning at the same rate as the black hole and observes it from a great distance directly above its ...
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What does this spacetime diagram mean?
I'm reading a book called "Reality is not what it seems: the journey to quantum gravity" by Carlo Rovelli and I'm struggling to understand this diagram that is part of the chapter about ...
- 435
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5
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558
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What is actually waving in a gravitational wave if spacetime is not a thing (just a mathematical construct)?
I have read this question:
except what is waving is spacetime itself.
Gravitational Wave - What is waving?
Is gravitational wave a new category of wave?
Yet none of the answers are satisfactory, ...
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304
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What will be the Lorentz transformation formula for 2 frames where they do not cross each other at $t=t'=0$?
For the standard Lorentz transformation,
we assume that F' crosses F at $t=t'=0$
and is moving to the right i.e. velocity $= +v$.
In that case, we use
\begin{gathered}x'=\gamma(x-vt),
\\t'=\gamma\left(...
- 4,476
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3
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Can there be simultaneity without a reference frame?
I have been reading about the concept of the relativity of simultaneity which states that whether two events, separated by space, occur at the same time is relative to the observer's reference frame. ...
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1
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In order To synchronize clock should the observers has same plane of simultaneity?
Suppose we have to observer $A$ and $B$ with their time given by $t_A$ and $t_B$.To synchronize their clocks observer $A$ send lights at $t_A$ towards $B$. $B$ receives the light at $t_B$ and send it ...
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5
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How should I understand the idea of relativity of space?
In the book General Physics by L.D.Landau, he mentioned the following in the first and second paragraph
The fundamental concept of mechanics is that of motion of a body with
respect to other bodies. ...
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Description of an Event in Special Relativity
Let me set up a system, where we have a rocket, and an asteroid moving towards it. Event 1 : When asteroid appears on the Horizon ( crosses an arbitrary mark about 14 light minutes away ), Event 2 : ...
- 1,791
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How the time slows down? In thought experiment of special theory of relativity in which two mirrors are used how the time gets slow for moving person? [duplicate]
If experiment is observed from stationery frame of reference then light travels more distance than frame of reference of mirrors so to keep speed constant time for stationery frame of reference should ...
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262
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Acceleration and reference frames in General Relativity
A person walks on Earth in a straight line, he says he is walking with uniform velocity. But I (from space) see him walking on a curved surface and say that he must be accelerating since he is ...
- 159
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51
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"Different reality" inside a black hole
why does our perception of space and time entirely change inside a black hole? And why does time not stop inside it from the perspective of the inside observer, however, extremely slows down for the ...
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Is the earth's version of time dictated by the earth's speed? [closed]
Is time on earth, relative to everywhere else, dependent on the earth's speed? Earth rotates at a speed, it moves around the sun, the sun moves around the galaxy and the galaxy is also moving - is it ...
1
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1
answer
113
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How to tell who is experiencing time slower and who faster when travelling at different speed?
I am trying to understand time dilation w.r.t velocity. Its said that when a satellite travels around earth (at speed more than a synchronized clock on earth which is stationary w.r.t earth), it ...
0
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1
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216
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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 ...
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