Space-time Definition and 419 Threads

Hi all, I understand the mathematics behind special relativity pretty well, but I only have a bare conceptual understanding of general relativity. My understanding is that energy, momentum and stress (as described in the energy-stress tensor) are what contribute to space-time curvature and...

I wonder if someone would field a beginner's muse I had: If gravity is just an illusion of the curvature of space caused by mass, does not the matter within that space follow the curve? and what is the granularity of that curvature? Does the curvature exist in the space between the nucleus and...

I know that according to Einstein's theory of relativity, space-time is like a fabric which can be pliable. Gravity is the shape, or the warping of that fabric. In this analogy, what would dark energy (the unknown form of energy that is causing the universe to expand) be?

Hi there. I was wondering that if mini or micro black holes could theoretically exist, and if not all black holes need to "devour' matter, then could it be possible that all things we perceive to have gravity could possibly be caused by a mini or micro black hole at the center of massive objects...

Hey, I have a thought that has been bugging me for a while. I know that Einstein's theory about the universe says we are all living in a 4 dimensional universe (the space-time fabric), but what if every fundamental particle in the universe has its own space-time. As if there are as many...

After going through the starting parts of Astrophysics, (and excuse me if I completely mess this up), that if the apparent brightness of the star decreases due to the loss in energy and contracts then expands again over a certain period. Then as the energy released has a mass equivalence, then...

Can someone explain how gravity pushes? I know that it bends space-time, and I've seen pictures of this. But in all of the pictures, they are just objects on a flat surface. Is it really like this, because then wouldn't space-time itself have its own gravity.

It is often said that gravity is a curvature of space-time and not a force. But since gravity is caused by mass, there must be some way in which mass curves space-time. What are the equations for how mass affect space-time?

One way to see that spacetime is curved is to try and draw a "rectangle" in spacetime (see the figure in the Feynman lectures, ch 42.7): If I wait for 100 seconds and then move upwards on earth, I end up at a different point in spacetime than when I first move upwards and then wait for 100...

Assume an eternal, static black hole which has an event horizon, a spherical surface at which any object passes a point of no return and is condemned to move toward a mathematical singularity. One of the predictions of being inside a black hole is that every spatial direction points towards the...

For the past few weeks, I've been struggling with the idea that velocity must curve space-time because of phenomena such as time dilation. Initially, I believed that because time is a component of space-time, through the phenomena of time dilation, velocity must curve space-time. I think I...

Hello, please note that the following is only about special relativity, not general. Of course, if there are any things to point out that fall in general relativity, feel free to do so, but I don't know GR, so I won't understand arguments based in GR. I also am not great with a geometry-based...

The impact of a bowling ball on the shape of a stretched gridded sheet is often used as a tool to help some of us to better visualize how the presence of a mass influences the curvature of spacetime? However, while this kind of diagram is helpful, I think that it is misleading because it...

I hope I am posting this in the correct forum, I am trying to better understand space-time singularities. I can find easily the basic, and advanced information on what it is and the different theories. My main question is how do scientists study these space-time singularities? Thank you for...

According to relativity gravity is just an illusion caused by wrapping of space-time fabric by mass, right? So, what is the elasticity of of space-time? There must be some king of resistance for the wrapping, otherwise even a tiny mass would plunge in the space time for eternity.

If space-time is curved like a klein bottle, is it theoretically possible that events could loop back in time ? :wink:

I am interested in the current understanding of time in SR GR QM and Cosmology and so apologies if this is the wrong place to post. I am currently reading "The End of Time" by Julian Barbour and am aware of "From Eternity to Here" by S Carroll and " The Singular Universe and the Reality of...

Why do we know space-time is locally flat,then we can use differentiable 4-manifold to describe the space-time?Do the Equivalence Principle say this?Classically space-time in GR is smooth,but what about if we consider the quantum effect?

is the higgs field the same ever wair or does the field thicker and thinner in places like space-time?

I have been working with the Godel solution to the Einstein field equations which is known to contain closed time-like curves. The metric I am using is the following: ds2 = dt2/(2ω2) + (exdzdt)/ω2 + (e2xdz2)/(4ω2) - dx2/(2ω2) - dy2/(2ω2) This is sign convention (+ - - -) Now from what I've...

I am having a very difficult time picturing space-time and fields and all... Anyone here have a sort of flow chart or procedural chart that I could use to try to better wrap my head around what this place is? Sort of starting with universe and then going into spacetime and from spacetime to...

Should one be able to take the results of 5D Kaluza-Klein theory and turn it into a theory that works with two less space dimensions? Thanks!

A source that is orbiting close to a singularity of a black hole is transmitting a radio frequency signal that lasts 60 seconds and is repeated infinitely. The signal is being transmitted using the amplitude modulation method (AM Radio). Let suppose that each minute passing in the transmitting...

I'm not a physicist so forgive me if this is a bad/stupid question, but i was just wondering what the current thinking was on a couple of things. (From what I understand space-time is a bit like a matrix which spreads out over the universe - and also gives us gravity etc?) 1. Does space time...

Do space-time have such behavior that if we give force on it and eventually it reacts according to the third law of Newton?

If so, what causes it to rip? Does it "heal"? What would a rip look like to us? What is the tension threshold at which spacetime rips? What are the units of this "tension"?

Homework Statement [/B] S' is moving at 0.5c relative to S. Two events, stationary with respect to S, occur at a distance of 4 light years from the origin at time 3 years and 6.5 years. Estimate the time between the events as measured by an observer in S'. Check your solution with the time...

A question from a physics laymen to those more advanced: if eLIGO detects gravitational waves by the difference to the combined laser wavelengths (a difference to the destructive interference pattern following curvature of space-time in each individual pathway), how is it that the lasers...

So the discovery of gravitational waves observed a contraction and stretching of space-time, and I've been trying to understand how the expansion of the universe means that space itself is growing. I want to understand how this actually works in relation to 'things' like a photon and an atom...

The original question title was too long, so i changed it. My question is: Does the detection of gravitational waves prove the existence of space time? The question may sound odd. I had an argument with one of my friends, who says space time is only a mathematical concept, space does not exist...

Ever since the proof einstein's theory of gravitational waves the whole world of physics has been literally changed. So I have a question, if space is made of something like a fabric which reacts to gravity; what keeps it together why doesn't it 'tear' if the gravity is too much. Is there a...

I just wanted to ask a question, since it went through my mind after hearing about 'gravitational waves' after they have now, apparently, been identified. does everything realease gravitational waves when it collides? Since everything with a mass has gravity, wouldn't that mean that even when...

If space is warped around heavy objects in space, i feel that space would be FUBAR around black holes. So, my question is, Does light get sucked in by gravity, or does it just get caught in the warped space around a black hole?

I've heard space-time described as 4-D and tenseless. The 4-D part I'm okay with, but I don't understand what tenseless means

Is not space curvature the curving or projecting into a higher dimension? Like a curved sheet of paper perceived by a two dimensional creature? The mystery seems to reside in our ape brains being unable to perceive (but not conceptualize) higher dimensions than three or relativistic, quantized time.

I obtained the black hole solution whose the metric function f(r) and scalar function ##\varphi(r)## are ; ##f(r)=\frac{1}{4}+\left(\frac{Z^{2}}{2r^{2}}\right)^{2}-\frac{1}{3}\Lambda r^{2}## ##\varphi(r)=\pm\left(\frac{1}{\sqrt{2}l}\right)r## where ##Z##, ##\Lambda## and ##l## are just...

Can anyone explain space-time to me, and how it disproves Newtons theory of gravity please? I've heard of the analogy that mass bends space-time like a bowling ball on a rubber sheet, but I don't understand how this happens, nor how this contradicts Newtons theory of gravity.

I don't know if this question is psychiatric or has to do with philosophy of physics : When we sleep is there subjectively no space-time, we don't feel in any place nor we know the time. So how does the brain reconnect to space-time ?

It space time is able to be warped, what is the shape of it? If it doesn't have a physical shape how can it be warped?

Hi everybody, I need to know if someone of you have ever simulated time-space varying permittivity media in RF mode with COMSOL. Thanks to all !

Hey, I have a question about waves. Why is it that the energy of a wave depends only on the frequency but not on the wavelength? Shouldn't two waves that have the same frequency but different wavelengths also have a different energy? If not there should be some other quantitiy with which one can...

Suppose we are in a Minkowskian space, away from all the source of gravity, and observe an accelerated frame from this frame. Acoording to Equivalence principle, we can consider the accelerated frame to be at rest and assume we have gravity in the accelerated frame. Thus, observer in the...

Hi, I have a general function u(x,y,z,t). Then, (1) what would be the space-time Fourier transform of G⊗(∂nu/∂tn) and (2) would the relation G⊗(∂nu/∂tn) = ∂n(G⊗u)/∂tn hold true? Here, note that the symbol ⊗ represents convolution and G is a function of (x,y,z) only (i.e. it does not depend on...

As an amateur, I am just testing my understanding on the following, since there is nothing worse than harbouring misconceptions. Suppose we have a space-time ( e.g. of FRW type ) which is conformally flat : C{^{\mu \nu }}_{\rho \sigma }=0 but not Ricci flat : R_{\mu \nu }\neq 0 Would that...

Hello, We were taught at school that gravity is a pulling force between two objects related to their masses and the distance between them. Based on this, it seemed reasonable why we can walk on Earth while on space or on the moon we cannot. But then I came to the Einstein's theory of gravity...

I'm trying to prove the following statements relating to space-like, time-like and light-like space-time intervals: 1. There exists a reference frame in which two space-time events are simultaneous if and only if the two events are space-like separated. 2. There exists a reference frame in...

I have heard many claims about the effects of space-time distortion but not really anything specific as far as matter. For example: I place two spheres 5 meters apart on the z-axis into empty space-time that is not at all distorted. Then I proceed to evenly stretch all of the space-time in that...

If time and space are relative, then if the amount of space is finite, is the amount of time finite? Is it possible to measure the amount of time for a given space?

Hi there, the most basic formula from Newtonian gravitation is, for a free falling object, x = gt^2/2, where x is the displacement in the vectical direction, in the case of general relativity, this just happens to be for weak gravitational fields, for the sake of simplicity (trying to express my...

Good morning, Yesterday I was reading a book about special relativity, It focused a lot about consequences of the theory, but there's only one thing I couldn't understand, which is as the title suggests, Relativity of simultaneity, that two different observers can't agree if two event are...