Relativity

The genesis of the theory of relativity was a long process that involved three major players and their critical reactions to the electrodynamics of moving bodies. Lorentz made a key step when he sought to develop a mechanics that would obey the principle of relativity and Maxwell's equations. Lorentz exploited the invariance properties of the fundamental equations for the interaction between electrons and fields, and thus accounted for the absence of effects of the motion of the earth through the ether, but only to a certain approximation. Poincaré made this absence of effects a general postulate and elevated the principle of relativity even higher than Lorentz di…

okay based on the theory of reletivity light will always go the same speed, even if your going the speed of light and you turn on a light it will move away from you. but from a fixed point of reference it will move the normal speed of light. Now people always talk about needing to find a way to move faster then light to travel to distant stars. BUT it is impossible. because even if we were to be able to go faster then light through some imaginary means, we would just go the speed of light no matter how much faster we were going. BECAUSE, time slows down to equal the speed of light the faster your going. so if you were going faster then light, time would jus…

Does anyone know a good book/website/resource on the mathematics of relativity from an undergraduate/graduate perspective?

Hey. Just hoping people to write facts about Einstein as a normal guy

If i am correct we don't know if gravity is a wave or a particle or what it is. I was just wondering if gravity could be like light and it be a graviton riding on a "gravity wave". Is that possible?

Request for opinion - Do you think there are any logical problems in defining the the term "inertia" to refer to the resistance of body to a change in mometum? The fact that inertial mass is defined as m = |p|/|v| seems to suggest this definition. Pete

what experiments, if any, have been invalidated by the extinction phenomena.

Does the "speed of light" change. I just had a thought .I know that sound waves go faster when going through denser objects!! does the speed of light change when going through denser objects??? If yes, what speed do we clasify as 'speed of light'(not the actual speed)when light travels through a vacume???? thnx guys!!

Hi, new guy here. There are a couple of things I have issues with concerning the relativity theory. The first is the matter of accelerating a mass up to the speed of light. It is said that doing this would require infinite energy and that this is supported by particle accelerator experiments. When you are accelerating a particle with energy supplied from a system at rest, it is true that you would require infinite energy. It's all relative right? If the energy for acceleration was supplied from an on-board energy source on a spaceship, the mass of the energy source (and it's energy) would increase at the same rate as the mass of the spaceship. I can't see how…

Hello all members of SF, for my first post, I'd like to ask a question which has been bothering me for a while. It may be because my understanding of physics is still pretty rudimentary, but I haven't been able to figure it out, I hope one of you may be able to help. Any ideas are much appreciated. So, here it is: Two large, round magnets are placed on rods in a way that they are very close to each other and then accelerated in a circular motion (like a top spinning, not like an orbiting planet) at close to or at the speed of light, but in opposite directions. What happens? Thanks in advance.

Imagine a universe in which all that exists are three balls(one red, one blue, and one yellow). Each ball has a mass of 1kg. The red and blue balls are at rest with respect to each other, but are moving with respect to the yellow ball. From a reference frame in which the yellow ball is at rest, the red ball and the blue ball are moving and thus have kinetic energy. Now, let's move our reference frame to one in which the blue ball is at rest. The red ball at rest relative to the blue ball, so has no kinetic energy(and neither does the blue ball). The yellow ball, however, is moving and thus has kinetic energy. The red ball has more energy in the reference frame of the yell…

IF the total universe for whatever that is collectively was at zero point energy hypothetically speaking what would gravity look like?

Hi! I'm studying physics for quite some time, and some time ago a thought popped up in my head....: In classical distance measurement (Einstein, 1905) a lightsignal is emitted, and the time delay "T" is measured, it takes to reflect at a distance "X". Einstein said the observer has orientation with the starfield surrounding him. I'd like to ignore this assumption. So let's say it's dark and cloudy within a cosmic nebular. And an observer flying there wants to measure the distance to the (dark) spaceship next to him. He send a lightsignal, and gets it back, after T. All fine. But what if he recieves it from a different angle, than he emitted the lightsignal…

Equivalence Principle is absolutely wrong!!!! The "gyroscope experiment". (experiment 14, at {website link removed}) This experiment is the end of Relativity Theory...!!!! tsolkas

The physicist Tom Roberts once wrote in a trash-filled newsgroup that Einstein discussed the hidden postulates of special relativity in his "Jahrbuch" article of 1909. Today I checked a Wikipedia article (another unreliable source) on special relativity, in the section titled “Postulates”, and found that it mentions “several tacit assumptions,” one of which is “the independence of measuring rods and clocks from their past history.” The reference cited there is Einstein, "Fundamental Ideas and Methods of the Theory of Relativity", 1920. I’ve never heard of an experiment to test “the independence of measuring rods and clocks from their past history.” If this principle i…

Lets just take a moment to consider relative measurements... I'm on a train an throw a ball forward at 10m/s To me be ball is moving at 10m/s But compared to the earth the train is moving at 20m/s So compared to my friend Bill stood at the station I've thrown the ball at 30m/s. So even classically velocity measurements are all relative. One of the things that comes with more advanced physics is the lack of an absolute frame of reference, and another is that velocities don't add in the way they do classically as above.

if i were to travel to a star...say 5 light years away (10 LR round trip) at 99.99999999 percent the speed of light and then come back to earth...which of the following would occur: 1) 10 years would pass for me (the traveler) where thousands of years would pass for those back on earth or, 2) a few hours would pass for me due to time and space dilation, and 10 years would pass for those back on earth thanks

I was reading a book about General Relativity the other day, and something occured to me; there may be a serious flaw in Einstein's reasonings. What jumped out at me is that although the common analogy of a bowling ball making a dent in a trampoline is a convienient way of grasping the concept of General Relativity, the flaw lyes in the fact that that analogy deals with a 3D ball (the sun) and a 2D surface (spacetime?) but this view is not applicable in the real world because spacetime is not two dimensional, it is three dimensional. This obviously means that there is a flaw in the common understanding of General Relativity, because that would mean that a 3D object would …

I found this video talking about time slowing down the faster you travel. Is it possible that this video is real? http://www.metacafe.com/watch/1366485/stop_watch_this/ I kinda think it's fake ...but I dont know. Richard

why would it matter? it seems people think that you can go back in time by exceeding the speed of light. why? wouldn't you just arrive at your location faster than the light would? as far as my logic goes, the only difference is that it'd be dark when you stopped. and if going faster than light does enable us to go back in time, shouldn't we also de-age? if we age going slower than lightspeed, shouldn't we stop aging at lightspeed, and de-age if we exceed lightspeed?

Hello, newbie here from Washington DC, no background in physics or higher mathematics, but very curious about theoretical physics nonetheless. I've been reading various articles about the speed-of-light and I came across a statement that intrigued me: Everything travels at the speed of light. Now, I realize that most of this motion for everyday objects is diverted in both the time and space directions, so that theoretically an object at rest is travelling through spacetime at light-speed through the time direction while light travels at this speed through space. But my question is this: "objects at rest" that travel at the speed-of-light through time DO NOT app…

need some clarity does light travel in a straight line? does it bend with different mediums? is light speed constant through different mediums or does ir slow down? what changes the wave length of light as red has the longest and purple the shortest? when you answer are they the same when light is exposed to gravity (except black holes)?

How does special relativity affect a gravitational field? I'd think that because the radius becomes smaller and the masses become bigger, the field is magnified by a factor of gamma^4. Is that right? =Uncool-

Am doing problems at the end of a chapter on "Vector Analysis in SR" Got stuck when asked to find the "elapsed proper time for the body as a function of t (Integrate d[math]\tau[/math] along its world line)" The body concerned here is "uniformly accelerated" ie "its acceleration four vector has constant spacial direction and magnitude" Ignoring y and z for the moment is the world line given by x = 1/2at^2? If so how do I get from there to [math]\tau[/math] as a function of t? As v is increasing the [math]\gamma[/math] is of course a function of time too - hence the integration I think. Have already found the relationships for speed and distance as functions …

Both of the books I have only derive the LT for motion of the frames parallel to the x axis. OK, this keeps the maths simple and also covers motion parallel to any other axis. But nowhere have I seen the LT for a relative velocity v which has components in each of the 3 spacial dimensions. I understand that the x values will only be effected by the x component of the velocity - and similarly for y and z. But what about t? So I guess my question is what is the "t" transform in this case? John