As a consequence of the Lorentz transformations, time and space transform into each other when changing reference frame. This calls for a unified description: Minkowski spacetime.

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1answer
148 views

Does mass compress space-time?

My understanding of relativity explains that the presence of mass warps space-time so that light travelling through the warp follows at straight line but the warp itself is curved and therefore the ...
1
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1answer
73 views

Questions about how the curvature of universe is described with a single number

I often read of physics talking about "the" curvature of the universe, giving it some letter $K$, and claiming that we have seen that $K = 0$ within such and such certainty. I have three questions: ...
0
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2answers
68 views

Don't rulers expand at the same rate as the universe they measure? [duplicate]

If you placed a giant ruler between the sun and our nearest star for example, wouldn't the divisions on the ruler expand at the same rate as the universe - therefore maintaining a constant distance? ...
2
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2answers
90 views

Can gravity prevent quantum superposition of positions for a massive object?

Theoretically, nothing prevents a really massive object to be in a superposition of two spatial locations, even far away one from the other. Then I guess spacetime would also show the superposition of ...
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1answer
48 views

Since Alcubierre drive moves a flat region of space, does it mean that space acts lika a liquid? [closed]

The Alcubierre drive would move a patch of flat space through space and, leaving exotic matter aside, is mathematically correct. Does that means that space-time is not a "solid" lattice i.e. not ...
2
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2answers
57 views

Could it be possible to bend space in more than one “way”?

Ever since the announcement of the discovery of gravitational waves, I have found myself pondering related notions of space. Recently, I was thinking about an analogy I've heard to explain how mass ...
0
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1answer
69 views

Black hole's singularity: Does it has to be multi-dimensional?

We assume that there is an infinite density at the center of a black hole. But we also know that if it was really infinite, it would apply an infinite gravitational force to masses even if they were ...
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3answers
246 views

Two “devil's advocate” questions related to LIGO measurement results interpretation

"If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things." Rene Descartes Laymen like me typically refers to Wikipedia ...
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3answers
97 views

How is Space-Time produced? [closed]

The parable of the ant walking on the surface of a balloon tells us that as the balloon expands, more of surface is created, hence more place for the ant to walk. Space-Time is also in the same ...
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2answers
89 views

How do you know what kind of space(time) you have when solving the Einstein Field Equations?

I'm experimenting with the EFE, and I ''invented'' a metric; a diagonal non-zero metric, and I discovered that the Riemann tensors are equal to zero which implies the Einstein tensor $G_{mn}$ equals ...
0
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1answer
58 views

What dictates the rate in which time passes? [closed]

I understand that special relativity tells us that our perception of the passage of time can change depending on reference frames. But why does time pass the rate at which it does in my reference ...
1
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0answers
99 views

What is the justification for continuing to model space-time as a manifold in string theory?

Background The question I have arises from taking seriously the idea that, in a physical theory, one should first define all physical quantities via (thought) experiment. Justification and ...
3
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1answer
62 views

Is the cosmological horizon expanding faster than space itself?

I read that the rate of expansion of the universe is still a mystery. But if it's actually decelerating, wouldn't it mean that our cosmological horizon is expanding faster than space, and that one day ...
1
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0answers
25 views

Time in the early universe [duplicate]

When it is said, for example, that grand unification took place "Between 10−43 second and 10−36 second after the Big Bang", how are these figures of time derived? Moreover, do these figures have any ...
-4
votes
1answer
106 views

Time slows down as you approach the speed of light, travelers observe speeds faster than light travel? [closed]

If I was on a spaceship traveling almost at the speed of light, my time would slow down relative to the time for a stationary external observer. My question is, since we measure distances between ...
0
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0answers
61 views

Scale factor of the universe

Do we impose that the scale factor $a(t)$ of the Universe is a continuous function? Or there is a physical meaning? Usually in physics we define functions to be continuous, such as the velocity of a ...
4
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0answers
90 views

Aren't black holes required to exist forever in our frame of reference?

I know that for an observer far away, nothing ever crosses a black hole horizon (due to time dilation), while in the frame of reference of a falling observer the horizon is nothing special on its way ...
2
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4answers
156 views

Does light in vacuum actually travel at the speed of light? [duplicate]

I know my question sounds like a joke (and I suppose on some level it is) but I'm confounded by the following: As the thought experiment goes, if I'm in a spaceship flying rapidly the people on earth ...
0
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1answer
23 views

Energy to move in space-time

Disclaimer : I am quite a beginner in physics, so very sorry if this is too much basic of a question but I have never read anything about what I am going to ask now. Or maybe I have but did not ...
1
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1answer
66 views

Is it correct to think about a point in time as the set of positions of all “things”?

Is it correct to think about a point in time as the set of positions of all "things" (photons, electrons, etc) that exist in the universe at that moment, despite the fact that simultaneity is relative?...
1
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0answers
38 views

Do relativistic frames imply different realities? [duplicate]

From Einstein's principle of relativity space-time and mass are relative to the frame from which they are being observed. Now would that mean a ball moving at the speed of light wrt to earth would ...
5
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1answer
131 views

How do we choose how to discretise spacetime in loop quantum gravity?

In LQG we choose a two-complex (or other) on which to discretise GR before quantising. I'm a little uncertain about the nature of this choice. Is the two-complex an a priori property of the universe (...
1
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1answer
114 views

What are gravitational waves relative to? [closed]

I have been having trouble picturing what kind of waves say Sun and Earth would make. Looking from top perspective Sun is in the middle and denting space while Earth is moving which is also denting ...
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2answers
92 views

Is Time Dilation in GR Simply a Consequence of Curved Space?

My understanding of time dilation in General Relativity is that it is the consequence of particles traveling at the speed of causality following longer, curved paths. Since it takes longer for two ...
1
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1answer
77 views

Is it possible to travel faster than the speed of light under extreme warping of spacetime?

The event horizon of a black-hole is defined as the point at which light itself cannot escape, supposedly due to a black-hole's immense gravity and effect on spacetime. However, would this not require ...
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0answers
43 views

Measuring distance in a spaceship moving with 0.5c [closed]

If there are a spaceship moving at a speed of 0.5c that sent a photon when an asteroid was exactly $3\times 10^8$ m away, will the distance between the spaceship and the asteroid when the photon hits ...
0
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2answers
83 views

How is the universe flat?

I have real trouble visualising what is meant by the descriptor 'flat' when referred to the shape of the observable universe. Which one of the below is more accurate? a) It is flat in a 2D way, like ...
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3answers
91 views

Time in spaceships near the speed of light

I know that the time on a moving object moves slowly compared to a stationery one, but if someone on a spaceship that moves at V=0.5c and a person is driving it. Will he notice that the clock on his ...
4
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3answers
234 views

Gravitational self-interaction

Today, someone asked me why "the warped space-time warps itself" (he read it in Kip Thorne's: The Science of Interstellar). I guess this is related to the gravitational self-interaction. But I don't ...
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1answer
61 views

Turbulence in gravitational waves

I want to understand physical meaning and possible implications of few terms often used in physics specially with regards to gravitational waves / space-time fabric Space-time fabric is disturbed by ...
3
votes
1answer
184 views

Quantization on Minkowski/Schwarzschild spacetimes based on unusual surface

I'm reading the book of Wald "Quantum Field Theory in Curved Spacetime and Black Hole Thermodynamics", and I'm pondering on this problem: In Minkowski spacetime, we usually quantize our fields with ...
0
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1answer
29 views

How is light used to measure the change in time caused by gravity?

Is the following analogy correct, if not- what changes are necessary to correct it? Let's consider a guy riding on a photon with a clock, and every time his clock ticks he paints a dot. Let's also ...
0
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3answers
99 views

Thinking about the properties of 'nothing' [closed]

If a certain identifiable part of space that has no type of measurable energy fields manifesting 'in it' for a given duration ; is such a totally empty space the same as 'nothing'? Anything with any ...
2
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2answers
86 views

How does gravitational wave compress space time?

My question came from the talk of how gravitational wave stretches and compresses space time. Say there are two protons that are 1 centimeters apart, as a G-wave passes through them, would the ...
0
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1answer
55 views

Why do planetary all rings seem to be on the equatorial plane?

Why do planetary all rings seem to be on the equatorial plane? When I first saw a picture of Uranus and its rings, I was surprised by their inclination, 90 degrees from the axis of rotation. This ...
4
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5answers
186 views

Is the universe bounded?

As I understand it nobody can pinpoint an objective "center" of the universe nor "where" the Big Bang happened. It seems the observable universe is limited by our event horizon at some 14 billion ...
0
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1answer
75 views

Trouble in understanding spacetime

I have a problem in understanding spacetime. What i understood from the conversion of time to distance is that the interval between any two events is always the same for any observer. But how is that ...
0
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1answer
76 views

Time Travel possibility and Paradoxes of The Past [duplicate]

can one travel back in time and if not so, what laws prevent time travel to the past. this is quite a challenge to understand.
0
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1answer
109 views

How can gravitational waves be detected when spacetime bends the instruments? [duplicate]

Apologies for the naive question, hoping someone with a proper physics background can explain this in layman's terms (as opposed to the more detailed answers at LIGO flawed by the identical expansion ...
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0answers
30 views

Space/time elasticity and state changing

What happens to a particular section of space/time that has been bent due to a large gravitational force that has passed it by? Does it "snap back" to it's original state. Is it permanently bent? Is ...
1
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3answers
76 views

On geometry of light's path in the Universe

Is it possible for us to see our own galaxy from different perspective, as path of light emitted from our galaxy is curved by any possible ways and travelled back to our eyes even if it take much time?...
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0answers
23 views

Warping of space time by objects

Note: This question may seem very silly, because I have never formally studied the physics I'm about to ask about at all, all the knowledge I have is from watching videos on YouTube out of interest or ...
1
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2answers
87 views

If the earth was really massive, then is it possible that no sunlight will reach earth due to gravitational lensing?

Say the earth was really massive, that it warps space significantly then is it possible that no sunlight will reach earth due to gravitational lensing?
5
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2answers
133 views

Gravitational waves in other dimensions

I know this question is purely speculative, as we don't know if more dimensions do exist and also we do not know if gravity is indeed stronger in other dimensions (if they were to exist). But, one of ...
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0answers
20 views

Light from the big bang [duplicate]

Considering that the Big Bang all started from a single point in space time, and the light emitted from it has been spreading outwards in all directions ever since, how do we, from earth, see the ...
1
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2answers
90 views

Are gravitational waves effected by the curvature of space time (gravitational lensing)?

I have a basic question I can't seem to find anything on (I keep hearing about how gravity waves and gravitational lensing were both predicted by Einstein). We all know about the gravitational ...
0
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0answers
90 views

How much time distortion was caused by GW150914?

I understand (at least I think I understand) that LIGO used distortion of space to detect GW150914 (one arm grew longer, the other arm grew shorter, causing interference in the returning laser-pulse ...
0
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1answer
182 views

LIGO discovery: if the space “time” metric is changed, how is it measured? [duplicate]

Regarding the wonderful 2016 news about gravitational waves. Travel time in one arm of the LIGO is ~ 30μs. A gravitational wave affects the arm for some few hundred of these laps. Then for example ...
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0answers
36 views

Why does a curved spacetime result in a movement?

If gravity is not a force but a curvature of spacetime, where does the motion towards the center of gravity come from? To put it differently, why would two objects in a space fall towards each other ...
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2answers
105 views

Is there a connection between Space-Time Vortex and Gravitational Waves? [closed]

Is there a connection between Space-Time Vortex and gravitational waves? Space-Time Vortex