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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general relativity vs graviton discovery

Will the discovery of the graviton lead to the redundancy of general relativity even though it has been so well established. If not, will it mean that gravity will have two separate theories that ...
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19 views

Can orbiting a black hole 99.99% speed of light make other object with relatively fast clock travel faster than light, relative to me?

If i orbit a black hole, 99.9% speed of light, time for me is moving slowly, relative to me, planet earth is aging fast, and i have traveled 10 years into the future(relatively) in 1 second, suppose ...
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248 views

Physical interpretation of distances

Suppose we have a universe with only two distinguishable particles, neglecting gravitation. These particles start off next to each-other, ostensibly "touching" each-other and at rest. If it takes ...
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2answers
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What is “a general covariant formulation of newtonian mechanics”?

I am a little confused: I read that there are general covariant formulations of Newtonian mechanics (e.g. here). I always thought: 1) A theory is covariant with respect to a group of transformations ...
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38 views

How to construct a space which is translation invariant but not rotation invariant

I am just confused by the following idea. Consider a 3-dimensional translation invariant space, we now have 3 translation generators. Then let us start with a point, the full 3-dimensional space ...
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220 views

Emergence of space from quantum mechanics

Once talking to a visiting professor at my institute, I heard about some simple model that captures the emergence of space coordinates as the eigenvalues of some infinite-dimensional quantum ...
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139 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 ...
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72 views

What would a universe with 2 time dimensions be like? [duplicate]

In a universe with 2 dimensions of time, and 3 spatial dimensions, the equation for finding the change in time is: $\Delta T= \sqrt{(\Delta \alpha_1)^2+(\Delta \alpha_2)^2} \geq 0$ Where $T$ is the ...
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3answers
405 views

Energy Required to Rip Spacetime

I have heard that the presence of an extremely strong gravitational field possesses the capacity to warp or tear spacetime and to potentially create a wormhole. Is any energy lost when spacetime is ...
60
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8answers
5k views

Turbulent spacetime from Einstein equation?

It is well known that the fluid equations (Euler equation, Navier-Stokes, ...), being non-linear, may have highly turbulent solutions. Of course, these solutions are non-analytical. The laminar flow ...
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2answers
331 views

Watching a live stream in spaceship traveling away from earth close to speed of light

My name is Dennis. This might sound just straight up ignorant of basic concepts of physics. I was having a conversation with my friend in regards to streaming a live event on earth to a spaceship ...
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1answer
82 views

How is Riemann tensor related to the curvature in the coordinates?

I came across statements such as "the acceleration observed in a weak gravitational field is mainly due to curvature in the time coordinate. " I want to know how we can explicitly find the curvature ...
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117 views

Gravitational Time Dilation vs Acceleration Time Dilation

I might be a little dense to this subject, but I would like to ask a question relating to this one ( Is gravitational time dilation different from other forms of time dilation? ) but asking if this ...
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2answers
153 views

Does negative mass reverse the arrow of time?

General relativity predicts that normal mass (positive mass) results in the curvature of spacetime which in return leads to gravitation. Since space and time are bonded together, any change on the ...
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5answers
3k views

Hubble's law and conservation of energy

If all distances are constantly increasing, as Hubble's law say, then lots of potential energies of form ~$\frac{1}{r}$ changes, so how is the total energy of the Universe conserved with Hubble's ...
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5answers
747 views

If the size of universe doubled

My question is silly formulated, but I want to know if there is some sensible physical question buried in it: Suppose an exact copy of our universe is made, but where spatial distances and sizes are ...
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2answers
2k views

Is spacetime flat inside a spherical shell?

In a perfectly symmetrical spherical hollow shell, there is a null net gravitational force according to Newton, since in his theory the force is exactly inversely proportional to the square of the ...
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3answers
720 views

How to prove the raising/lowering indices operation?

I've read this related question, though it didn't satisfy me; I hope this complements it. I know that if I contract a covariant tensor ${A_{\alpha\beta}}$ with a vector ${B^\beta}$, I get some other ...
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0answers
23 views

Could I use a VHP lazer to determine my actual spacetime 3d age if I could pinpoint where the earth was at my birth? [closed]

Given a specific origin point in space, i.e. our exact place in the universe at the time of our birth, and perhaps a second reference point or more i.e. our Sun, can we calculate our actual space-time ...
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2answers
191 views

Is it possible for the Higgs Field strength, to increase with time? [closed]

Magnetic fields are created when an electric current flows: the greater the current, the stronger the magnetic field. What influences could affect the Higgs Field? If the Higgs field grew in ...
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1answer
202 views

Herbert Dingle's paradox modified

Suppose two spaceships A and B have on them clocks A and B move along the same straight line at uniform speeds differing by 161 miles per second. And suppose they are at positions A and B in space ...
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1answer
159 views

Can special relativity be derived from the invariance of the interval?

As far as I know, the classical approach to special relativity is to take Einstein's postulates as the starting point of the logical sequence, then to derive the Lorentz transformations from them, and ...
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40 views

Homogenity and Isotropicity of space

In school it is given that law of conservation of momentum is a result of homogeneity of space and law of conservation of angular momentum is a result of isotropicity of space but what is isotropicity ...
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4answers
113 views

Why is acceleration of expansion of space unexplained?

I didn't know how to better phrase the question so here we go. It says that the farther we see from our galaxy the faster the other object seems to be going away (accelerating). My common sense ...
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2answers
66 views

In the classical inflation and big bang theory how can the universe grow to infinity?

Some astronomers make the conjecture that the universe is actually infinite in extent (which is a bad manner of expressing, I know). If so, how could it grow to this size in the classical theory of ...
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28 views

Behavior of an object in a region of uniform spacetime curvature

Let's say there is some spherical region of space. In this region, there is a large curvature of spacetime. This curvature is completely uniform throughout the region. I decide to stick some object ...
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1answer
62 views

How to prepare mental skills to understand relativity theory? [closed]

Upto the high- school, I had to admit and write-on-exam the strange, counter-intuitive statements of relativity theory; those I could not believe. Now, I'm not a physics or math-student, (and indeed ...
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1answer
48 views

Can reality be explained in 2 dimensions? [closed]

First, I apologize if this question is too long or too incoherent to respond to on your website. Second, I am no mathematician or physicist, only a thinker. Third, what follows is all part of my ...
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482 views

Does the current acceleration of universe imply that our universe is open?

Does the current acceleration of universe imply that our universe is open? If the universe is closed, from the Friedmann's equation, the acceleration of universe wouldn't be possible, would it be? (Of ...
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1answer
189 views

Is there a minimum distance?

I would imagine there is no limit to how small space can get. Is this correct? I am aware of planck's constant, but cannot objects be closer than Planck's constant is short? Perhaps this question is ...
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2answers
57 views

How does rotation of a mass affect the geometry of space? [closed]

I understand (or rather, I have been told, but do not understand) that a large mass can distort space by its rotation. While I am somewhat familiar with the concept of a mass distorting space and ...
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4answers
107 views

Does the $t = 0$ hypersurface of simultaneity constitutes the universal present?

Does the hypersurface of simultaneity in the diagram below represent the universal present moment? Source: Einstein for Everyone - Spacetime
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2answers
247 views

Could time be considered a force

I think I understand the basic concept of spacetime, at least some of it. And when people talk about spacetime they don't call gravity a force, but rather the result of mass interacting with it. And ...
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2answers
62 views

Is the effect of mass density on the expansion of the universe linear?

The average expansion rate for large scales parsec and above measured is $\approx 73\,{\rm km}\,{\rm s}^{-1}\,{\rm Mpc}^{-1}$. This expansion is calculated for average densities of space volume across ...
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918 views

Is the tide on Earth caused by curvature of spacetime

The tide on Earth appears absolutely whenever the moon is overhead. Is that tide caused by spacetime, re-curvature in space or attraction gravity?
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2answers
106 views

How does gravity truly work in the bend of spacetime?

If gravity is caused from the bend in space time from a large mass, why do all objects fall towards earths center and not strait down to below earth? Sorry i am not an expert in any fields just trying ...
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4answers
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Could the black hole in the center of the galaxy be a white hole?

In the center of the galaxy there is a strong radio source which we call Sagittarius A*. Based on the high speed and orbit of nearby stars we have calculated that something with the mass of more than ...
2
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1answer
81 views

What is the latest science on closed timelike curves? [closed]

In Scientific American (Sept 2014), Lee Billings writes: Lloyd, though, readily admits the speculative nature of CTCs. “I have no idea which model is really right. Probably both of them are wrong,”...
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4answers
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Conservation of Energy vs Expansion of Space

My question pertains to a possible inconsistency between the first law of thermodynamics and the general expansion of space itself. First, the knowns: Space itself has, and continues to expand - ...
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1answer
106 views

Does space itself fall into a black hole? [duplicate]

Long time ago I heard someone say that it is space itself that falls into a black hole. Yesterday I saw a little animation that suggested the same (although I´m not sure, because the person who put ...
3
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2answers
115 views

Is a spacetime of constant positive curvature just a 4-hypersphere?

In discussions of basic cosmological models, I don't see "spacetime of constant positive curvature" described more simply as a "4-hypersphere". What am I missing?
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A photon lives life as a flat-lander? [duplicate]

Think length contraction... I was thinking about going close to the speed of light the other day, and I was thinking about the idea that, if you went close to the speed of light, time would slow down ...
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1answer
189 views

If a point r lies in the boundary of the chronological future of another point p, why does the chronological future of r belong to that of p?

I am studying the global causality of the spacetime. Here, I come across a problem. Suppose a point $r\in \partial I^+(p)$. $I^+(p)$ is the chronological future of a different point $p$ in spacetime....
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3answers
1k views

What is space made of?

General Relativity posits that matter curves spacetime, such that geodesics point towards the object in question, hence, gravity. Now, how does matter do this? What is spacetime "made of", anyway, ...
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3answers
139 views

Mathematical Formulation of Classical Spacetime

I have seen two formulations of Classical Mechanics: Newtonian spacetime (learned it from the lectures of Professor Frederic P. Schuller): Definition: A Newtonian spacetime is a quintuple $(M, \...
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1answer
84 views

If the universe has no center, how it can collapse?

After reading Does the universe have a center? and trying to find a place in my mind for "There exists no center", I asked myself: If there is no center, in what direction our universe will collapse, ...
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39 views

Does the rate of observable change within space-time change as time passes?

Mass seems to be one thing the effects the "relativeness of time". Assuming the big bang, if the universe had mass in one central location and the mass is moving away from a singular point it would ...
2
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1answer
92 views

How much Gravity is required to stop time?

Clocks free of gravitational influence run faster than those experiencing gravity. Is it possible for gravitational influence to bring time to a stop? Additionally can acceleration affect clocks in ...