Space-time Definition and 419 Threads

http://www.news.cornell.edu/stories/March06/CMB_Timeline300.jpg If space-time is flat (on large scale), why then does this [above] picture show curves? Would I be right to say that space time at anyone moment is flat but over time it is curved?

I'm taking a "Space and Time" 4000 level philosophy course and right now we are desperately trying to wrap our heads around the discrepancies between minkowski and prior space-time diagrams and the philosophical significance of absolute speed of light and of time- and length-...

Space-Time is deformed from a uniform gravitation field to one that is compressed inward so as to form a curvature. That curvature is uniform and can be understood as a series of decreasing diameters of circular field lines. If that is the case, then why are the planet's orbits elliptical and...

Please note that I do NOT want to discuss whether gravity is a force or the effect of space-time curvature here. If you want to discuss this, please post a separate topic about it. What I wanted to ask is what Einstein's own beliefs on this were. Up till now I had always believed he had...

I was looking for a space time metric that describes the INTERIOR of spherically symmetric rotating stars. However, wherever I look it is always the metric for an exterior of "slowly rotating star" (frame dragging effect) or something similar to it but always the metric AROUND the object...

i recently read A Brief History of Time. it says that the orbits of planets may seem elliptical, but are actually straight in space-time. so how does that happen?? how does space-time curve?? here does time refer to imaginary time? and what do we really mean by imaginary time? is it taken that...

Hey, not strictly homework but this is probably the best place for it, I wonder if you guys can help me out with a past paper question I've been pondering: Two events occur at the same place in an inertial reference frame S, but are separated in time by 3 seconds. In a different inertial frame...

Cinsider please the invariance of the space-time interval in an one space dimension approach (x-0)2-c2(t-0)2=(x'-0)2-c2(t'-0)2 My question is: does it hold for arbitrary events (x,t) in I and (x',t') in I? Does it hold only in the case when the events are genertated in I and I' by the same...

"So would they be able to detect a holographic projection of grainy space-time? Of the five gravitational wave detectors around the world, Hogan realized that the Anglo-German GEO600 experiment ought to be the most sensitive to what he had in mind. He predicted that if the experiment's beam...

First I thought If nothing can move faster than c, then nothing can accelerate faster than c/sec, right? Well, that means that the maximum amount space-time can curve is up to the ol' 45 degree slope, not like straight down as some black-hole pictures are made. Right? And then I thought...

I wasn't sure where to put this, so astrophysics seems like a good bet? I'm only fourteen, but I'm incredibly interested in astrophysics, quantum mechanics, black holes and the like. I've read about naked singularities, that they can occur the black hole's charge is great enough and the...

I am not a scientist, so my apologies if this question is naïve, but I have read a bit on the subject. Anyway, I was recently watching a documentary on Einstein and the standard illustration of Space-time being warped was presented. A massive ball was placed on the trampoline of “space-time”...

Hypothetical thought experiment; What would happen if you created a very long cylindrical material, eg 100 000km long and took it into deep space. Here you rotate one side of it so the tube is spinning in a large circle with radius 100 000km, ignoring friction and gravity. Once it is...

Does string theory state that space-time is made of strings? And if so, how can "empty space" be made of strings if string theory says that a single string is a particle? Also, would space-time being made of strings be an explanation as to why it behaves so erratically at very tiny scales...

Why do things orbiting, i.e. free-falling, around Earth float away from each other? Why don't they both free fall toward Earth together? I remeber hearing once that if you let go of 2 objects while 'floating' in space they both go away from you and away from each other. Is this due to curving...

Homework Statement How do we argue that gravity is not a force due to curvature of space-time? Homework Equations I'm new.. I don't even understand the eqn of tensor calculus. The Attempt at a Solution No force is needed for as massive objects follows the curvature of spacetime...

I know what the equation for proper time is in basic Euclaiden space. But when space-time is concerned, I get a bit confused. The equation is: \Delta\tau=\sqrt{g_{\mu\nu}dx^{\mu}dx^{\nu}} I realize that g_{\mu\nu} is the Metric tensor. However i don't understand the dx's and their indices...

what is space-time disturbance..can anyone explain it to me.

I'm confused, but when objects travel along the straight lines in curved space-time, do they undergo acceleration? We know that following geodesics is equivalent to inertial motion (one example is free-fall), but when these inertially moving objects travel in curved spacetime, they accelerate...

Hello... I have a little problem I hope you guys can help me with. I'll write down the problem-text first, so it will be easier to point out the problem - hopefully. Here it goes: Event E0 has the following coordinates in some frame S: x = 2 m ct = 4 m Locate E0 on a space-time...

Hello... I have a little problem I hope you guys can help me with. I'll write down the problem-text first, so it will be easier to point out the problem - hopefully. Here it goes: Event E0 has the following coordinates in some frame S: x = 2 m ct = 4 m Locate E0 on a space-time...

i studied somewhere that acceleration and gravity are equavalent .does acceleration produce ripples in space-time just like mass?

Imagine a beam of light being turned on at the surface of a massive body such as a neutron star, the beam of light travels along a geodesic path towards a mirror located at radius r from the planet's surface, when the light beam hits the mirror, the light bounces back to the observer located at...

Just wondering? Space-time is exerting pressure. Is this movement faster than the speed of light?

Considering the simple case of two observers O1 and O2 lying on the same radius at positions r=r1 and r=r2 respectively. Using a result from Stephani(1) I work out that the ratio of frequencies of light sent radially between these observers is given by this ratio, numerator and denominator...

I don't know anything about GTR, nor do I know anything about differential geometry. But I have one maybe stupid question: As far as I know space-time in general relativity is represented by a pseudo-riemannian manifold. And according to Whitney's (or Nash's? - don't know who is in charge here)...

*Please read the thread before you vote in the poll! Disclaimer: I am not advocating a fraudulent theory, I am presenting original evidence and logic (detailing the contradictions in quantized gravity) both of which are certainly open for debate. Gravitation In classical mechanics, the...

Can anyone explain in words (or equations if you can't use words, or in words to describe the equations) how "...according to the theory [of gen relativity], half of this deflection [of light by any massive body, the sun in this quote's case] is produced by the Newtonian field of attraction of...

Does relativistic mass curve space-time, i.e., does relativistic mass affect the gravitational field of an object?

Does a photon curve space-time, i.e., produce a gravitational field? Is the degree of curvature a function of its energy?

What is the rationale for the sign convention in the space-time 4-vector? How is it related to the sign convention in the energy-momentum 4-vector, if at all?

Trying to 'visualize' phenomena at sub atomic sizes is imposssible because our idea of visualization relies on space time and light. Its similar to trying to put real meaning to imaginery numbers. Does 'i' exist or not. What does a photon 'look like' - has no meaning because we cannot bounce a...

Hi. Could anyone here help/teach me how to calculate the resulting bend in space-time from any particular mass? Specifically I'm trying to figure out how much space-time is stretched or bent relative to "unbent" space-time in space. I'm not exactly sure this is the right question to be asking...

Hello everyone, I am a self taught (dare I say Physicist?). I have been struggling with a specific concept of GR/SR. This concept is "Gravitation" and it's explanation. As I understand it, classic Newtonian gravity in which mass attracts to other mass is not technically correct. There are...

What would be the easiest way to plot a space-time curvature from a metric as a curved 2D surface. For example the Alcubierre metric would be plotted with the result as in the attached image. The mathematical programs I have at my disposal right now are Maple, Matlab and Mathematica. I'm much...

I find in the literature the following transformation equations for the space-time coordinates x'=g(x-vt) t'=t/g g=gamma. Please tell me what do they bring new in the approach to SRT? Thanks

Hello, I have been trying to work out the mathematical details of H Snyder's 1947 paper, titled http://prola.aps.org/abstract/PR/v71/i1/p38_1" , and I am stuck at something. When the space-time variables are considered as Hermitian operators, and we need to verify that they satisfy Lorentz...

Please tell me if it is possible to derive the formula which accounts for the Lorentz contraction from the invariance of the space-time interval. Thanks

I would like to ask another 3 question, 1.Gravity causes warps in the space-time fabric in general Relativity what cause this gravity? i was told in grade school it was with the planets rotation around its axis, but now, trying to do my own research in General Relativity i have found nothing...

Please tell me if the following statement is correct: In cc(dt)^2-(dx)^2=cc(dt')^2-(dx')^2 dx and dx' represent proper length dt and (dt') representing non-proper time intervals.

hey guys, I asked my( well she's not mine since i don't take physics yet)physics tacher if there is an equation to find out how much a body can curve space-time, but she gave me f=Gm1m2/r^2. But I'm pretty sure that's not it. I know that the equation is not linear. Could one of you guys who...

*note: I had this reviewed by a moderator before posting, so I hope you consider it appropriate to this forum. Hypothetical proposition (of the form “if p, then q” – without asserting the truth of p or q): If space-time S is not infinitely divisible, then space-time S cannot be infinite in...

In an attempt to explain space-time curvature and gravity, the analogy of a flat rubber sheet is often used whereas a massive object, such as a bowling ball indents the sheet in the same way that a massive object such as a star creates curvature in space time. Would it be a fair analogy...

As i know the model of how gravity works is. The fact that there is a web of space time that you place a ball (sun) into it pushes down onto it, then placing smaller balls (earth) into this dent and they will in and around it... What I do not understand is how in the world is this logically...

Greetings all. This is my first post. I'm a newbie to general relativity, but I think I'm getting the hang of it thanks to some helpful professors at UC Berkeley. From what I understand, and now fully believe, there are no external forces applied to an object that is free falling in...

Ok let me begin by saying I'm far from an expert on this subject... but I'm doing some personal research and have a question. Please answer without being TOO technical xD (I can do some calculus and somewhat advanced math but not like insanely complicated math.) Anyways... does anyone know any...

Neutron Stars (black hole?) picture. maybe this not news. Published in something like "physics review of celestial body". I attached a pic, but it does not manage to show.

Penrose proved that a more than 4-dimensional spacetime would be unstable.. does this mean that String theory is completely wrong?? (since this only works on 11 dimensions). Also without offending nobody's beliefs .. .what're the proofs for the existence of String theory ??, its math elegance...

Hey, I've been a little confused on the concept of gravitons. I know that they are the messenger particle of the gravitational force, but I thought that gravity was a result of the warping of the fabric of spacetime. If a large star warps spacetime, therefore attracting things around it, then...

That is the question, if you assume the space-time is discrete then it will be an smallest amount of volume line surface and so on, but how do you know how big this amount is ? for example in usual QM we have that energy is quantizied so the avaliable energy levels are eigenvalues of the...