Space-time Definition and 419 Threads

Hi there. This is my first posting to this forum, and in fact to any forum in many years, so please excuse me if I have not followed the rules correctly or chosen the correct forum. I have been watching a lot of Neil DeGrasse Tyson-related videos and it has lead me to a line of thinking...

Time variable of space-time at the end of universe... As universe is continuously expanding at the accelerating speed...expansion of the universe causes Redshift...the whole universe is made up of the tiny particles and the material. Because of this all the material particles of the universe...

Can someone direct me to the solution to the space-time metric, ds^2 = -dt^2 + dx^2 + dy^2 + dt^2? Thanks.

Are spinors needed in modern theoretical physics as opposed to tensors? I have come across Penrose's book "Spinors and space-time". Does anybody know what mathematical prerequisites are needed to actually understand it? (at least volume 1) Can I manage to go through it with a good knowledge of...

As the universe expanded after the big bang it was expanding into nothingness, ie even the fabric of space-time itself didn't exist. How far ahead of the expanding matter was space-time being created for it to expand into?

When looking at Earth's ability to curve space-time; how far does these curves go? can they theoretically be registered at the edge of the universe?(just an infinite small amount of course).? i suppose i could just ask if Earth's gravity stretches everywhere in the universe? or.. is there a...

Gravity around star is often depicted as the curvature if spacetime or a 'dimple" in a flat sheet. What would happen to space-time around a star if the star were to instantly disapear? Would the fabric of space time snap back to flat space or would it reverberate, expanding then contracting...

I understand that matter and energy bend space time, yet i am curious as to the level at which it requires to bend it. This is obviously an elementary leveled question, but i am quite curious. Also, is there any level of matter that is incapable of bending space-time? Thank you!

If space-time itself is quantified, and the spatial universe has, at anyone time, a finite volume, would this not imply that at anyone moment there are a finite number of spatial locations? (If so, then integrating over an infinite number of points would only give an approximation.)

I have a question that has been bugging me for a while. You see, I have a predisposition of trying to visualize everything that I learn. I have no problem visualizing space-time, black-holes distorting space-time, the universe expanding, etc..., but when it comes to the Doppler Effect I want to...

Please teach me this: What does causality principle mean when space time dissapear(e.g being inner black hole or before Big Bang).Does it meaningless to say about causality when having not the time. Thank you very much in advance.

if i consider space time to b a fabric as considered by einstein then expansion of this fabric leads in two direction 1-if the fabric has high elasticity then the curvature of space caused by the a massive object will keep on increasing,thus the flow of time will be faster...

Hi all, One thing I found puzzling about several intros to GR is that, after a summary exposition of absolute diff. calculus, without further ado they posit a Levi-Civita connection, then derive the Einstein field eq. As if all manifolds had to be pseudo-Riemann, then. Do they really have...

How does time and space appear to a photon in vacuum (i.e. photon at at the speed of light)? Does time stop, when looked, from the frame of reference of a photon? What about space? Time-space are in a senses interchangeable/inseparable, so how does space-time appear to a photon? Does a...

Hi there I understand the general idea about the Theory of Relativity and the idea of a 4 dimensional space-time fabric, how the sun ( a mass ) sits on the fabric and creates a well on which the planets sit and therefore orbit the sun due to gravity. But how does one explain the case of...

Hello everyone, I'm a new member of the Physics Forums, and not a physicist by specialization, so please have mercy :-) I'm a linguist by training, and by profession a writer of fiction and role-playing games. I'm currently in the process of getting my first science-fiction novel...

Im looking for books or research that contains data on the actual curve of space (for example, the curve a specific mass or force creates) e.t.c If anyone knows any books or research done on this topic would be highly appreciated.

Is entanglement effected by space-time? other than, of course, when entanglement is created/destroyed...Some related thoughts: - information transfer needs mass-energy to carry it - mass-energy cannot travel faster than speed of light - in entanglement...mass-energy is not involved...(in the...

Plot of energy against space-time (from alpha to omega) I was wondering what a plot of energy against space-time would look like going from alpha to omega, using the assumption that the universe is heading towards an omega of flat absolute zero. I came up with a guess of this...

Could it be possible that space-time curvature is not caused by matter but is an inherent characteristic of space-time? Wouldn't this explain dark matter?

I apologize if this is a nonsensical suggestion/question. I would also like to apologize if this has been placed in the wrong forum. While surfing the Internet I suddenly had a thought. Could the Higgs field (HF after this) be interchangeable or combined with Space-Time? (to be called "ST"...

Hello. This is my first thread. I consider relativistic frames of reference in terms of E=MC2. I'll discuss the mass of my body for an example. If I increase the energy in my mass I lose mass and gain energy. So if I travel at the speed of light, I will have 0% mass, and 100% energy. I would...

How could "strange shapes" affect space-time? To my understanding anything massive enouph to bend space and time noticeably would end up becoming a sphere due to how gravity works. But what if you could have diffrent shapes that were massive enouph to affect the universe? What if you made a...

How does moving at near the speed of light affect the geometry of space-time? How does an object increase in mass in relation to its speed? Does this have to with more collisions with the theoretical Higgs boson?

Why Yab=Xab-kHab+k2HacHcb-... and not Yab=Xab-kHab+(1/2)k2Haccb-...? Y is the curved space-time metric X is the planespace-time metric

Hi there, physics lovers! Sorry I'm bothering you again. The following may sound as stupid questions, but this is a very hard topic for me, so don't judge me that bad! :) You see, when we're talking about light in curved spacetime, the geodesic equations (or equations of motion) use an affine...

Ok, I sort of understand the space-time fabric but there's one thing that bugs me. In this picture, how does the satellite orbit the earth? I know it's because of gravity but how is affected by the curvature of the space-time? It's not touching the curved part. Or does the curvature go all...

Hi, I was wondering what the expression would be for the energy operator in general relativistic quantum mechanics. So I attempted it for strictly diagonal metrics. Here it is: Assume a stationary observer. Then the expression for a particle is E=-g_{\alpha\beta}p^\alpha...

Hi, is Spacetime geometry there even without the presence of matter or does matter produced Spacetime? Or in other words. If the universe is completely empty without matter. Is there a Spacetime geometry?

(Hopefully, Part 1 of 2) This is one of my favorite metrics, and I decided that while tedious, and old-fashioned, I would practice for my GR studies by finding the Christoffell symbols and write out the equations for geodesics using the Gödel metric, then attempting to solve them. First...

Hi, I was wondering if the non-relativistic kinetic energy (or the total energy) of a body in a curved space-time can still be written as \frac{\mathbf{p}^2}{2m} As an example, is the kinetic energy \frac{\mathbf{p}^2}{2m} in the Schwarzschild metric for a non-relativistic particle...

Hi, I'm reading a book on SR/Field theories that simply posits the space-time interval and from that defines a Lorentz transform as any transformation which leaves the interval invariant. My question is how do we posit the space-time interval in this manner using only the postulates of...

Hi, I am wondering what are the transformation laws (Lorentz transformations) for a general metric, if they exist.

From what I have gathered, M-theory states that there are 11 dimensions. We live in 4 of these dimensions, and I believe the common understanding is that the 7 other dimensions are incredibly small. At the time of the Big Bang, these 3 dimensions expanded along with the universe while the...

Since nobody answered my last question I''l try it this way: Why does redshift indicate that space-time is expanding and not that galaxy's are just flying away from each other?

I know that Hubble observed redshift which led to the conclusion that space was expanding. But why did redshift lead to such conclusion? Why didn't they just think that galaxy were "flying" away from each other instead of thinking that it was the space that was actually expanding? What made...

How to change the curvature of space-time around a very powerful laser beam?

Suppose we are looking from an inertial frame at two events in a region of space-time. The first event A (0,0,0,0) is the orign of our frame. The second event is B(10,10,5,15/c) where the 4th corrordinate is time and c is the speed of light. Then the total interval between the to event is ...

Why is it possible that an object can be found in the same place in different times but can not be found at the same time in different places?

My biggest qualm with the special theory of relativity and, for that matter, the general theory of relativity is the fact that both assume a little bit too much. My first area of skepticism is that so many cling to these as much as they do to Newton's laws, but there has been no tangible proof...

This is for anybody who might wish to cling to the idea that there is space and there is time, each of which are measured individually as sole and separate characteristics of the universe by either a ruler or a clock, but that they do not otherwise intertwine as within the context of Relativity...

Alright, I'm a bit ignorant when it comes to more advanced subjects (well, very ignorant...), but, from my understanding, according to Einstein's theories, a strong gravitational field, perhaps describable as increased Space-Time density, increases the rate of time of an observer and warps...

Mass can curve space-time. Is it possible that space-time around a black hole is so badly curved that it forms a closed 4D manifold?

Hello, I am in a college seminar on Einstein and his theories. One of the topics we have recently been discussing is space-time geometry, particularly that of De Sitter. A question arose the other day about whether two of Einstein's Cylinder space-time maps could be added together in order to...

What is the relation between Hilbert Space and space-time? Are the two disjoint or is there something relating the two?

Hi, I have been wondering if there is a Lorentz-invariant quantity that satisfies the definition of a metric for space-time. The space-time interval s2 = t2 - r2 [where r is the vector (x,y,z)] does not satisfy the requirement for a metric m that m(t1,r1, t2,r2) = 0 if and only if (t1,r1)...

In GR, there is said to exist a fabric of space-time, and gravity is the warping of the fabric of space-time. Since GR is simply an extension of SR, the fabric of space-time should exist for both, then, both relating to the same universe and all, right? So could the fabric of space-time be...

LET, Lorentz ether theory, is identical to SR but invokes an ether as the cause of length contraction and time dilation with motion through the ether. With it, there are no strange conceptualizations according to each observer's own particular reality for what they observe of other frames, but...

I'm trying to find Schwarzschild solution for 3-dimensional space-time (i.e. time\otimes space^2). The problem is, I can't take the 4-dimensional solution \[ds^2=\left(1-\frac{r_g}{r}\right) dt^2-\left(1-\frac{r_g}{r}\right)^{-1} dr^2-r^2\left(d\theta^2+sin^2\theta d\phi^2\right)\] and...

From the wikipedia page on http://en.wikipedia.org/wiki/Complementarity_(physics)" : As I recently noticed in the double-slit experiment there is a lot of time-uncertainty, not only position-momentum uncertainty. That is shown in the fact that the probability wave does not reach the screen...