Relativity

This came to me the other day. It can show that GR, in this one respect, is an approximation for classical gravity. Here is the scenario. If I took a bolder and lifted its edge and placed a block of foam underneath it, it will flatten. This is due to gravity-weight. Based on this scenario the local GR=gravity has not changed appreciably, yet classical gravity caused a compression in distance that exceeds the change in GR. What this suggests is in some applications classical gravity is an approximation for GR. But in this type application GR is an approximation for classical gravity. Classical gravity is changing the position of the atoms so they get physically closer…

The below theories were developed by us when we saw something wrong with Einstein's Theories of Relativity. we will like to tell you that when someone is on a moving vessel such as the earth or a rocket almost to that of the outwards moving galaxies,you will see the universe much more like it really is, but when you are stationary you will see that the universe tends to look constrasted in size.this is because the particles in the universe are all in constant high speed the more things approach light's speed the more you tend to varnish into thin air because of the light isnt able to expose all parts of them every well as usual but when they deccelerate they will the…

In Relativity: The Special and General Theory page 155, Einstein expressed this quality of spacetime as follows, "Spacetime does not claim existence on its own but only as a structural quality of the [gravitational] field" Am I correct to assume that empty space or a vacuum is essentially the qualities of the gravitational field? I have trouble understanding the concept of time, without the idea of movement. Is there a motion that is associated with the gravitational field itself?

This is a theory that came to be a few weeks ago. If we take the reciprocal of the SR equations, times the mass, distance and time, then instead of getting mass, distance and time increase we get mass, distance and time decrease using any given velocity. Where this could come in handy is if we were in a moving reference and had a relative velocity bead on a slower reference. It would tell us the MDT parameters of the slower reference based on the conservation of energy. For example, we have two rockets launched from earth. One has more fuel and is able to reach double its mass due to SR. The other has less fuel and only reaches 1.5 times its stationary mass. The ene…

As time slows down as a body approaches the speed of light and its length shortens does its other dimensions also change? How would this effect a space traveler whose mass should not change?

Not sure if this is the right place to post this, but why can't something accelerate past the speed of light? Can't you just give it more energy? Very odd indeed.

Have moved on from SR and started Schutz book "A first course in general relativity". I do not understand some of the symbols used in the proof of the invariance of the interval. I am referring to equ 1.2 to equ 1.3. What I am missing is what is meant by M with 2 subscripts followed by 2 quantities in brackets. M[math]_{ab}[/math] (dx[math]^{a}[/math]) (dx[math]^{b}[/math]) Umm have not quite worked out how to show equations yet either! The a and b are superscripts to the dx. Any help appreciated John

I've looked up the concept relativity of simultaneity on wikipedia and am having trouble understanding . I looked at the train and platform thought experiment and dont really understand it too well. It would be pretty nice if someone could help me out

ok im basiclly very new to relativity. I have read a little on it and understand it very little. Every book that I pick up and read explains it a little to complicated for where i am at. So im just asking if anyone knows any book that would explain it easier. Thanks alot. Matt

Hello there, new to the boards so forgive me if this is in the wrong place. I was in a discussion recently about relativity and probability and was wondering if anyone could tell me how much 1 days time at the singularity of the universe before the big bang would be in relation to current earth time. As time slows in the presence of gravity, what is the correlation between 1 day at the center of all mass in the universe to earth time. Thanks MW

I got a quick question. In SR there are two postulates. That the laws of physics are the same in all reference frames, and that the speed of light is a constant. So basically, there are two types of objects, those that go the speed of light, and those that move slower. As you know, there is a length contraction for different reference frames. The Lorentz-Fitzgerald Contraction. My question is this. What about for objects of Planck Length. That is, the smallest possible length there is. If it was accelerating relative to me, SR tells me I would view it get smaller. But it is defined as the 'smallest possible length'. Obviously this is a breakdow…

I'm thinking of the fact that time dilates to a halt relative to an observer at rest as you approach the speed of light. That means that no time passes for those inside the space ship that's traveling at the speed of light. All their displacement in spacetime is through space. As the space ship slows to a halt, no displacement in space occurs but displacement in time dilates to its usual rest rate (relative to an observer also at rest, of course). But what is this "usual rate"? Wouldn't it just be the same rate of displacement as that through space which the spaceship traveled when going at the speed of light? That is, when at rest, do we travel through time at the speed …

I just finished reading a remarkable biography of Albert Einstein, and want to recommend it. It's called Einstein, His Life and Universe. It's the first biography to tackle Einstein's enormous volume of personal correspondence that until recently had been sealed from the public. It's hard to imagine another book that could do equal justice to Einstein's richly textured and complicated life. It's really a wonderful read, and tells us not only about Einstein's science, but his personal life as well. Machines Like Us

"Weird question!" you are likely to say. Kindly follow me for a moment: Suppose a Quantum Theory of Gravity does hold. Then, gravitational influence of a body (call it B1) on another (call it B2) would be excerted by means of a shower of gravitons (virtual partices) B1 would emit, which would transfer momentum and energy to B2. And vice versa. Those gravitons (if they trully exist) are supposed to be emitted by the MASS of B1...Any objections so far? Suppose however that B1 undergoes gravitational collapse (e.g., if it is a red supergiant after the supernova phase) causing its mass to shrienk within its Schwarzschild Radius, i.e. confine itself within an "even…

Just a thought experiment. If you were in a heavy spacecraft in orbit around a supermassive black hole a comfortable distance outside the event horizon of a black hole then would it be possible to lower a camera on a length of string, recording at the camera, down into the black hole (deeper than the event horizon) and record what it sees, before retreiving it for viewing by pulling it back up with the string. The camera would have rocket motors to make side-to-side adjustments if necessary (to keep the string straight and radial to the orbit). It would obviously assume a very strong and long piece of string, of low mass. As it is a supermassive black hole the spage…

Ok, I just thought of this this morning and I've got to try out the idea on some people. Here's WHY the masses are equal: The Setup (skip it if you know alot of physics): Sorry, my mind works with analogies, I'll use standard ones, first, we have the sheet of rubber that has balls of different masses placed in it. The masses bend the rubber (warp the fabric of space-time) and display gravitational effects. It's a bad analogy because it relies on your knowledge of "real" gravity to power the motion, but hold that thought for a minute and I'll remove "real" gravity before I finish up. Next, we extent that sheet of rubber until it models the whole universe as a b…

The mass of a star represents the degree of gravitational attraction, however what role does the spinning of the star upon it axis play? If it did not spin would it also be unable to hold objects in its orbit? And if the spinning of the star is essential to holding objects in its orbit, do those objects drain the star of ‘gravitational energy’ by slowing that spin down with their own contrary inertia?

Some other thoughts that disturb me about Black Holes. BHs have intense gravitational fields. They are objects borne of the classical theory of GR. According to GR gravity propagates at c. It cannot move any faster than this according to the rules of GR. Thus if the sun was to suddenly disappear we wouldn't know about it for over 8 minutes - no signal can reach us at super-luminal speeds to warn us of our impending doom. We have experiments currently trying to detect gravity waves. The idea is to detect gravity waves as they pass us and warp spacetime. I haven't checked the research lately but last time I looked we had not detected any gravity waves. According…

I have been told that according to the theory of relativity if a man leaves Earth in a spaceship, and travels at a speed approaching I the speed of light his time passes slower than time on earth. If this is so, when the man returns to earth his calendar date and his time would be behind earths; he would be in earths past, and earth would be in his future. How could this be?

I've heard two opposing views of gravity, and many compilations. The first being: That gravity acts upon a static background and is a force that is there because of mass and it just is. And the second being that the curvature of spacetime because of mass causes objects to follow different paths making it seem they are 'attracted' to each other. Obviously, the first one is wrong, and has been disproven by GR and experiments since then. However, the second seems to be a common conception, but I don't understand how that would work. Because if something is merely curvature and I were to have a large body say, a black hole who influences much space around it to ha…

I'm trying to solve E=mc2, I'm not sure if I'm doing it correctly though, so I'll model out what I'm doing. First, the mass of the object 5 kg. So you plug in the numbers E=(5)(299 792 458 m / s), and then, you just multiply and you get 1,498,962,290 joules, and that's the amount of energy you need to move an object that weighs 5kg (11 lbs) at the speed of light. Is that correct? edit: Unfortunatly I forgot to square the speed of light, so the amount of energy from the annihilation of a 5 kg (11 lb) object would be 2.246887947x1018

I just thought of something about time paradoxes and i haven't heard anyone say this but it seems really obvious... I thought that if you were able to travel through time and then you went back with the intent of killing your dad before you were born it would simply be impossible to kill him. I'm not saying the universe "protects itself" by stopping you creating a time paradox, i'm saying that if you had killed your dad before you were born then you wouldn't have been born, thus not existing to kill him in the first place. So if you went back in time wanting to kill him you would know for definite that you couldn't, SOMETHING would stop you no matter what. Another th…

If the velocity of a satellite is required to be proportional to its distance from the star (ie Kepler’s law), how would the coming together of smaller satellites, form a satellite that is stable in its orbit? Just to try and simplify this request further - take the asteroid belt - each asteroid travels at a velocity required to maintain it in a ’stable orbit’, (with the absence of Jupiter) if these asteroids were to come together, the resulting increase in mass would require the new satellite to increase its velocity in order to ’stably’ maintain its orbit… …How is this explained? By the way... Warm greetings to all and thanks in advance for your effo…

I am a 16 year old student from Admiral Lord Nelson School currently studying AS Publicunderstanding Science. I have chosen to do a peice of coursework on the question; "Is Time An Illusion?" I am posting on this forum to gain as many people's opinions as possible. I would be grateful if you could reply to this stating what you believe time to really be and if possible any evidance for this. To answer "Is Time An Illusion?" first of all you first need to know what an illusion is. According to en.wikipedia.org/wiki/Illusion; “An illusion is a distortion of a sensory perception, revealing how the brain normally organizes and interprets sensory stimulation. While illu…

In the twins paradox one twin is said to move away and come back and be younger. But how can they tell which one is moving? They are moving relative to each other - sure - but surely then things would be the same from either point of view. Is the fact that one (or both) of them must have accelerated to get some relative speed and must then decelerate/accelerate to turn around and then decelerate to stop - relevant? Ie if the speed changes that occurred happened without the application of a force (ie by magic) would things be the same? I first read the special theory back in the 1950s when a student and have never really understood this point. It seem to me that motion …