# Tag Info

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Within the theory of special relativity this is postulated. Hence the theory does not address why this is true. If you're wondering why special relativity postulates this, the simple answer is that these are arguably the simplest postulates that give a theory that explains observed phenomena. You may want to read about the history of special relativity to ...

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Minkowski spacetime has the symmetries of the Poincaré group, which include the four spacetime translations. Noether's theorem then says that there are four conserved quantities, $p_0, p_1, p_2, p_3$, associated with these four symmetries. Typically $p_0$ is denoted by $E$. The structure of the Poincare group implies that these four quantities are related ...

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Even if Alice and Bob are both first to measure their spin (according to their respective reference frames), two spins entangled into the singlet state will still give opposing results. That's what quantum mechanics predicts. Finding out that the entangled spins gave agreeing results would falsify a prediction of quantum mechanics. People would be very ...

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Think about this from the perspective of a person in the elevator. No windows, they can't look outside. As far as they are concerned, they live on a small box-like planet where the acceleration due to gravity is 9.8 + 1.2 = 11 m/s$^2$. In a system where the acceleration due to gravity appears to be 11 m/s$^2$, a bolt drops 2.7 m. How long does it take to ...

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$kT$ is related to the kinetic translation energy by the equipartition theorem. You are saying that the mean kinetic energy, is much greater than the rest energy. The particle has a large or relativistic velocity. The limit $kT>> mc^2$ is called ultrarelativistic limit. It means you can approximate the energy momentum relation $E^2=(pc)^2+(mc^2)^2$ by ...

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Since the traveller is circling Earth, he/she is actually accelerated. So his/her frame of reference is not inertial (if we take that of the beholder to be inertial). The two points of views are then not equivalent, unlike those in the twins paradox. If I'm not mistaken, one may show that the beholder will "see" the traveller be slower, and the traveller ...

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This is one of the most misunderstood things about entanglement, which is that it doesn't matter who goes first. Neither measurement actually affects the other one, contrary to the intuitive implications of "wave function collapse". Entanglement is correlation, not causation.

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Your question has nothing to do with entanglement. You might as well ask this instead: Physics predicts that two positive charges will repel each other. Suppose I bring two positive charges into close proximity and find that they attract each other instead. How can this contradiction be resolved? Or you could posit any other experimental result that ...

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For online sources, there are some good introductions to special relativity here and here. For a print book An Illustrated Guide to Relativity seems like a good intro. Another good one is Spacetime Physics by Wheeler and Taylor, which I think for the most part just requires algebra though there may be some sections/problems that use some basic calculus. ...

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I beleive you have a huge confusion. The Minkwoski metric only gives geometrical properties of the spacetime, and it basically states that the spacetime is not euclidean. What you are asking is similar to asking that Newton laws and classical mechanics comes from the fact that we live in an euclidean world (without time component). The first postulate: ...

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From the Minkowski metric plus the first assumption of Special Relativity, the rest may be derived. That is, if it is assumed that physical laws are the same in all inertial reference frames, which was first proposed by Galileo, and taken up by Newton; plus the Minkowski metric for spacetime, we automatically obtain the invariant spacetime interval, ...

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Special relativity does not tell you, that there are inertial systems moving along with a light ray. The formula for velocity addition is essentially a formula about transformation of a velocity in the frame of a moving observer. It's just not the right question to ask, what an observer moving at $c$ would observe. Since there are none.

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The velocity addition formula applies when there are two observers (say A and B) moving with respect to each other. If C is some other object, we have three relevant velocities: That of B as measured by A, that of C as measured by B, and that of C as measured by A. But in your setup there is only one observer. (A light beam is not an observer; it has no ...

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The part where you say the traveler wouldn't see any set speed limit is correct. They could always go faster and get there in less time in their frame of reference. An observer who sees the traveler moving would never see them move at or faster than the speed of light.

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