Space-time Definition and 406 Threads

Is it allowed to travel to the past in ST?. I've always thought about paradoxes in the regular framework (4D space-time). What about ST framework?. I need a little guidance here. Thank you in advance, AGZ

So i just had a thought. A rotating object creates a small but identifiable vortex in space-time. I would imagine that the faster the object rotates, the more drastic the vortex becomes. My question is, if you were to have a massive object rotate very fast, at near the speed of light, how does...

What is space-time singularity? How it formed...? Is singularity possible..?

Homework Statement (a) Find ##\dot \phi##. (b) Find the geodesic equation in ##r##. (c) Find functions g,f,h. (d) Comment on the significance of the results. Homework Equations The metric components are: ##g_{00} = -c^2## ##g_{11} = \frac{r^2 + \alpha^2 cos^2 \theta}{r^2 +\alpha^2}##...

Is space time has a energy itself ? Thanks

Could it be possible that space-time might have existed before the big bang, but separately? And that "time" somehow collided with "space", and then merged together into space-time, and in the process created energy as a bi-product? Or how about if "time" collided with "space" like above...

http://en.wikipedia.org/wiki/Kaluza–Klein_theory ##http://link.springer.com/article/10.1007/BF01390677 (original german paper, Ich kan nicht Deutsche) http://www.scientificexploration.org/journal/jse_21_3_beichler.pdf (this author makes some interesting arguments) Also, a lot (if not all...

This is probably a stupid question but does k=1,0,-1 correspond to closed,flat,open refer to space or space-times? Looking at a derivation what each geometrically represents is only done when talking about the spatial part of the FRW metric. As space can be flat and space-time still curved...

I was interested to know as magnetism works in space. Can magnets be used to bend space-time? If this is possible may be able to time travel.....

I'm interested to understand the interpretation of gravity as a result of exchange of force particles (ie gravitons) vs General Relativity-based warping of space-time. Related to this is while a constraint to speed of cause and effect would apply to the graviton-based concept, why should this...

1. A photon does not experience time, does a photon experience space? (between interactions?) 2. When photon is bound between electron orbital levels it is "stuck" there and hence experiences time? When an electron jumps to a lower orbital it will emit a photon, this photon would then move at...

I consider myself a science fiction inventor. I have recently theorized a space-time pumping machine and want to use it as a faster than light propulsion theory. I really like to make my inventions very close to real physics and wonder if anybody knows concretely whether space-time can move...

How can we show one dimensional relative parallel velocities in space time diagram ? (One dimensional means there's only pozitive and negaive values of speed)

I have always wondered if spacetime is actually smooth, or if it is granular such as a quantized spacetime. I remember learning that if you draw the smallest possible square around a circle, you will, of course, get a perimeter, 8 times the radius of the circle. Then if you draw in the...

This is probably a stupid question, but is there an equivalence between matter, energy and space time? Like for instance if you had a ball of 1 kilogram, could you convert it into volumetric space and have everything around it be further away? When two or more objects are going further away from...

Can we add another time axis to Einsteins space time diagram? Since space and time are one thing they can be represented by one axis. The other axis can be a cosmological constant average axis. By adding this extra term can mass and energy be measured by a time scale relative to the expanding...

Assuming that my understanding is correct, I believe it was Einstein who proposed that gravity is the result of the warping or curving of space-time. My question is this: if gravity, which is solely attractive in nature, is the result of warped or curved space time, then is it possible for the...

I teach a class on astronomy and recently tried to explain the curving of space time by massive objects like neutron stars and black holes. I even used a sheet of spandex to represent space-time which we bent using different weights. However my students were very confused how space, which they...

In a paper published in Reviews of Modern Physics in 1949, http://journals.aps.org/rmp/pdf/10.1103/RevModPhys.21.378 , H.P. Robertson provided an analysis of the physical implications of the Michelson/Morley, Kennedy and Thorndike, and Ives and Stilwell experiments which seems definitive with...

Hello anyone who can answer. I have a question concerning dark energy (Please realize that my knowledge is limited on this subject) It is known that the universe is expanding at an accelerating rate, scientists say this is due to the mysterious dark energy. It seems to go against our...

Hi all, I was wondering if anybody else here thinks the concept of space-time dilation/concentration (curvature) is a little bit funny, not in the sense of it having an effect on the neighbouring particles, but in the sense of actually stretching or contracting, as though it itself had certain...

Is it possible that Quantum Space-time would exist?

I know that Space-Time is curved near the source of stress, but I'm not quite as clear what that means for the projection onto normal space and I'm trying to get my head around it. Is a kilometer on Mercury the same as a kilometer on Neptune? Is there a relatively simple formula (that is, an...

There's this graphic of space (s) versus time (t) of a particle. How would I know if the trajectory is always rectilinear and if the velocity is always positive? Observation: none of these "sentences" are true in this graphic. But I want to know how would I know these things if they were...

In the page http://en.wikiped ia.org/wiki/Hamilton%E2%80%93Jacobi%E2%80%93Einstein_equation, under Shortcomings of four-dimensional spacetime", you can see the following line: Is it correct? If it is, how can it be? Because in GR, gravity is space-time curvature!

In theory by John Wheeler...The Space Foam is a billion trillion smaller than the nucleus of the Atom, what is potential smaller than the Quarks, Calabi Yau Manifolds, Vibrating Strings and Space Foam? Is there anytime smaller than the Space Foam?

1. Gravity is the geometric curvature of space-time caused by massive objects. 2. Dark Matter surrounds galaxies. 3. Dark Matter is thought to be critical in galaxy formation. 4. The mass of Dark Matter creates curvatures in space-time around baryonic matter which forms galaxies. What roles...

I've always been interested in Space-Time fabric and have been trying to get a clear answer to whether or not its an actual fabric that's two dimensional or is that an easier way of understanding it when talking about gravity and matter and how Space-Time is effected. If it really is 2D, why?

Hi guys! I'm currently working on a topic in the field of cosmology, more specifically Bianchi IX models. It is hard to find any form of information about this specific subject. And of course I don't just want to derive the metric for Bianchi IX, I also want to apply this model and do some...

So what actually is space-time.

When we talk about space-time curvature or the curvature of space, how many different "types" of curvature are there according to GR? For example, the rounded surface of a cylinder is curved in only 1 dimension, while the other is flat. For a sphere, both dimensions of the surface are curved...

Hello experts, Could someone suggest some materials that would explain to me the current state of knowledge about how space and time are two aspects of the same thing, but matter is not? I've seen and read many popular explanations of how space-time was unified by Einstein's theories of...

The final episode of Cosmos: A Space-time Odyssey, "Unafraid of the Dark", was released today. This marks the completion of the series. Which episode did you like best?

Im reading about Coulombs law in my textbook. It states that: "The forces between to charged particles are proportional with the charges Q1 and Q2, and inversely proportional with the square of the distance r between them. F=kQ1Q2/r2 The forces acts along the straight line between...

Hi everybody, As you know, the Einstein field equation R_{μ\nu} - 1/2Rg_{μ\nu} =κT_{μ\nu} implies that at any point with vanishing energy-momentum tensor the Ricci curvature also vanishes: T_{μ\nu} = 0 \Rightarrow R_{μ\nu} = 0 hence a Ricci-flat space-time (the vacuum...

Can a magnetic field bend space-time?

If the space-time interval is calculated according to: ds2=dx2+dy2+dz2-c2*dt2 what might be an example of 2 events in space-time separated by this interval? Suppose for example ds2 =1 (or a constant) and the first event was at the origin where would the second events lie? Am I...

I'm sure many of you remember the original series hosted by Carl Sagan that aired on PBS during the 1980s, and how well it was done. I'm really looking forward to this new version: Cosmos: A Space-Time Odyssey - Wikipedia, the free encyclopedia I have come to respect Dr. Tyson for his deep...

A mass moves through space-time at constant velocity. Space-time around this mass is warped by the mass and as the mass moves through space-time it causes unwarped space-time to warp and already warped space-time to warp more. In addition, the space-time it has moved through de-warps. Why...

...is the impression that "God plays dice with the universe" an illusion? If all time in the universe is already defined, then, is the apparent randomness a result of the nature of the experiments we can perform? Does a 'sum of histories', and quantum probability... 'square' with the...

This is something I have pondered for some while... it is so obvious that there must be an answer and is probably a silly question, but I haven't found an answer yet... so... Gravity is a consequence of the localised curvature of space. According to Relativity, space (space-time) is...

There is an apparent conflict between relativity and quantum theory, in which case quantum theory must be redundant isn't it as it explicitly makes the assumption that spacetime is continuous whereas relativity in-fact derives the notion that spacetime is continuous from an experimentally...

Is there a single equation that can model both spatial and temporal metric contraction simultaneously? And also what's that equation that can model the actual degree of curvature n space-time that uses trig functions and how do you use that in combination with the two previously mentioned...

I am doing my B.S. in physics. I want to do my PhD in theoretical physics from a good university. It may not be a so called top ranked university. I just want a university that will give me the opportunity to innovate new ideas in theoretical physics. I have special interests in...

Hi. I know that as an object travels faster, its mass increases. Would this increase create a larger curvature in space-time?

I really find difficult understanding what spacetime diagram does relativity use while defining its notion of space and time and moving observers. Can we place both a still and moving observer in the same space time diagram as in the figure (A), then the moving observer measures time going...

Imaging at a Trillion Frame Per Second - Ramesh Raskar http://www.ted.com/talks/ramesh_raskar_a_camera_that_takes_one_trillion_frames_per_second.html Although this video is extremely interesting, The part I'm most interested in occurs at about the 9:30 mark. Ramesh Raskar says...

Would the spin of a particle be measured the same by any set of observers upon that strip? Would an observer experience a reversal of spin if the particle traveled far enough along the strip?

Space and time did not exist during the big bang or before. Are there any theories as to how the continuum was generated?

Hi guys! I have a rather brief question regarding circular free fall orbits in the Schwarzschild geometry. Consider an observer in a circular orbit in the equatorial plane at some allowed ##r = R##. The angular velocity as measured by an observer at infinity is given by ##\omega^2 =...