Relativity

Time dilation will redshift the spectrum of an radiating object moving relative to the observer. Also the motion of the object will redshift (if the object is moving away) or blueshift (if the object is moving closer) it spectrum because of the Doppler effect. For an object moving toward the observer, is there a speed where the redshift cause by time dilatation will be compensated exactly by the Doppler blue shift ?

If, say we had a particle at rest at point A, wouldn't that violate the Uncertainty Principle because we know it's location, Point A, and it's speed in the time dimension which is C. Or am I just ignorant here?

Theres the classic experiment in which someone is sent into space, rides around at a high speed, and comes back to everyone being older. Im assuming the reasons for this are well understood by the forum community. But what if the people on earth were to build a device capable of tracking the spacemans craft, and sending a video/audio signal to him. How would they appear? would they seem to be moving in a "fast forward" sort of motion, or would they jump ahead as the spaceman decellerated? I have a vague grasp of this, but im looking for some more definite understanding. Also, for the purposes of eliminating variables, the spaceman is moving at about 99.9% of c

e=mc2 well you got that far saying matter and energy are the same thing e=m SO WHAT IS THAT STUFF matter and energy

When I look at the gamma factor in relativity equations, I always see the Pythagore theorem [math]\gamma=\sqrt{1-v^2/c^2}[/math] If we take c for unit of speed we get [math]\gamma=\sqrt{1-v^2/1^2}=\sqrt{1-v^2}[/math] and [math] 1=1^2 [/math] so we can write [math]\gamma=\sqrt{c^2-v^2}[/math] [math]\gamma^2=c^2-v^2[/math] [math]c^2=\gamma^2+v^2[/math] When the gamma factor is applied to time, it make me thinks that time is more than one dimentionnal. What do you think about that ?

How much does a photon weigh? According to E=mc² if a photon is made of energy, it would have a (albeit an exceptionally small) mass, therefore it should exert a gravitational influence on it's surroundings, shouldn't it? Which brings me to another question: do high-energy photons move slower then low-energy photons? If they really are heavier, then should they be not quite able to reach the maximum speed limit, as there's more photon to move around...?

What is a graviton?

In general relativity the gravitational field energy-momentum 4-tensor is a pseudo-tensor. Basically GR conserves energy-momentum, which is generally different to energy conservation, which general relativity conserves only in asymptotically flat space-times. Energy is a frame dependent concept, and as there are no preferred frames in GR there is no clear definition of energy or whether it is conserved or not. http://arxiv.org/PS_cache/gr-qc/pdf/0410/0410004.pdf http://arxiv.org/PS_cache/hep-th/pdf/0308/0308070.pdf http://www.pma.caltech.edu/Courses/ph136/yr2002/chap01/0201.2.pdf In order for energy to be conserved, the matter energy-momentum 4-tensor must satis…

(FTL = faster than light) OK, I know you may automatically respond "it's impossible" and I know it is, but explain this: You have a disk rotating at 0.25C (powered by a motor), then attached to the center of that rotating disk you have another motor turning another disc at 0.25C and then a 3rd and a 4th etc... So all relative to me (at rest), unless specified: Motor1 body is stationary, motor1 moving head rotating at 0.25C, motor2 main body is rotating at 0.25C (attached to disk1 which is attached to the moving head of motor1) and then the moving head of motor2 is rotating at 0.25C relative to the main body of the motor2, making disk2 (attached to moto…

When most people talk about the possibility of "Time Travel", I would think that we all, for the most part, expect to interact in some way with the past or the future that we "Travel" to, in order to warrant and validate such a statement. But on the other hand, if we were to only hope to "observe" the past from a point of safety and not acctually try to interact with the past or future event, surely we can, and do this all the time in everyday life..? As I understand it, all the light that enters our retinas has taken a certain amount of "time" to reach us and has traveled a great distance, so taking this simple concept to a greater scale, all the humanly vi…

I would like some help developing what I am going to call frame theorems. For right now, I am going to define frame as synonymous with a three dimensional rectangular coordinate system. It's just easier to say frame. Theorem 1: If F is an inertial reference frame, then any frame G whose coordinates are related to the coordinates of F by a simple rotation through an angle f is also an inertial frame. Has anyone seen this theorem before? PS: Here is my goal. I want the frame theorems to increase my ability to solve physics problems. Specifically problems dealing with rotation, and translation. In other words, the goal of the theorems isn't to be i…

I know that the theory of relativity is E^2 = (mc^2)^2 + (pc)^2 And when a particle is at rest it has no momentum therefore p = 0 and we arrive at E = mc2 But how did Einstein arrive at E^2 = (mc^2)^2 + (pc)^2 first.

Ok, i'm trying to figure out how many different 4-vectors exist in SR -4-velocity -4-acceleration -4-force -energy-momentum 4-vector -displacement 4-vector -4-potential Is there some other? How many different 4-vectors exist in Special Relativity?

Suppose that I have a 'loop' with spokes, attached to a motor. Let the ring be a regular N sided polygon. Therefore N>3. Might as well analyze the simplest case. Let N=3. So the polygon is an equilateral triangle. There are three spokes, and they meet at the center of inertia of the triangular loop. Let the perimeter of the equilateral triangle be one meter. Therefore, the length of any side is 1/3 of a meter. (incidentally you can tessalate a plane with equilateral triangles) Ok so this object is going to start spinning. Suppose that the Lorentz contraction formula is a true statement. Here is my question. What is th…

This thread is for any experts in the general theory of relativity. Suppose that it is possible to accelerate like the starship enterprise does, where its going at warp 1, and then jumps to warp 7, but the inhabitants aren't tossed about, because they cannot feel any forces due to changes in their speed. Suppose that is possible, and has been done by mankind in the future. Would that existence of that kind of ship be experimental proof of the falsity of the principle of equivalence? A simple yes or no will do. Thank you in advance

Physics is a lot more interesting than I ever imagined it to be, at least the special relativity aspects of it. I have a couple of questions. I mostly understand the theory, but a few questions which I can't find an answer to (at least not translated into non-expert-physicist terms) have been bothering me. (I know, they're the really amateur questions that people who don't understand it well ask a lot but....) First of all, if there's a spaceship moving at .9c, then relativity tells us that time moves slower because its moving, I.E. the twin paradox. However, couldn't the spaceship consider itself at rest and everything else moving slower through time? What is it that det…

my friend says he doesn't believe in time dialation and when I tried to explain to him all the proof and stuff, like mathematical and even experimental, he wouldn't listen to the mathematical and when I told him about the experimental ( rocket flying really fast, clocks were slightly different) he just said some crap (I am allowed to say that right?) about how it was probably rigged, because scientists wanted more money, how the clocks couldn't have been started at the same time and other crazy sorts of things. I was wondering then, if anyone here can give some sort of explanation of how time dialation has been observed and maybe some sort of reasoning to convince hi…

Al Einstein all my life all you hear is Einstein " Relativity" you never never hear Einstein E=mc2 Farther of the atomic bomb! you see that is why everyone knows Einstein he won ww2 single handedly by inventing the atom bomb but america has to claim the victory and they do it by trying to always make you think of relavity instead of atom bomb like relativity is so important , i have one question how often do you move at a hundred million miles per second! what never! so that so important, that you never do it but never ever say al won ww2 never never say that never never never

if there was only one object in the universe, would gravity exist? gr says that gravity is the warping of space caused by matter. so, in gr, there would be gravity. but, in qm, gravity is caused by graviton exchange. so, in qm, there wouldn't. what's the deal?

Okay, I know there are other posts on Time Travel, but they seem burned out so, this is my own personal question anyway. Am I to understand that Time Travel to the Future has been proven Fact? I was watching phycisist Brian Greene (I think that was his name) saying that Time travel to the Future has been proven by taking 2 identically set clocks, put one on a Pan Am Jet, and when it came back they no longer said the same time. The difference was extremely minimal, like Billionths of a second. But he also says that if we travel at almost light speed away from the earth for 6 months, and come back at the same speed for another 6 months that we would have only aged a y…

I was reading in the paper on special relativity from David W. Hogg and i was hopping it would explain frames, but it hasn't so far, though it has mentioned them plenty of times. Please explain to those of us who go to high school in some hick town out in the middle of nowhere. Thank you

A simple question: Is relativist mass subject to gravity ?

Which are the components of the Lorentz tensor in SR if the signature of the Minkowski metric is (-+++)? Can you give me a link to some page showing them? Thanks

The appropriate category for this is classical electrodynamics, but there is no category here for that. But since relativity comes out of EM, I figured I would put it here. My question is quite simple. I want to know if this propulsion system will work or not. Construct a solenoid. Wrap a wire around a cylinder N times. Now place an iron ring around the solenoid, and then connect the leads to a battery. There will be an induced EMF in the iron ring, and the ring will be launched into the air. Jumping ring demonstration. So something is pushing that ring up, in the rest frame of the solenoid. Ignoring action/reaction for the moment... Suppose you con…

I was tempted to put this in the Cosmology forum, but I would prefer theoretical critisism to empirical I believe. I'm going to "draw" a simple model of the universe. It's a circle. So, if you will, imagine a circle and call it the universe. This is a universe in ONE dimention, the outer curve of the circle. The actual universe has more dimentions, you may picture them as you like, but they are all tangential to the plane that the circle exists in. This circle is a moment in (space)time. If you were to freeze-frame the universe this is what it would look like. More importantly, I would like to add that the big bang happened a the center of the circle. As the unive…