# Tag Info

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I'm a bit unsure where you are unsure, but let me try. The "real" behaviour is best seen in the frame of the liquid. In this frame the bullet will shrink compared to it's stationary size, and so it will have a higher density than the water (supposing they have the same density when stationary). The acceleration downwards will be given by the difference in ...

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When you talk about a point in space, you're talking about a specific set of $(x, y, z)$ coordinates. Of course there's no use to talking about a point in space unless something is happening there, e.g. $(0, 6, 0)$ is the cannonball's starting location". An event is the same idea in $3+1D$ spacetime- it's a specific set of $(t, x, y, z)$ coordinates. ...

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Just open any string text which has a discussion of the relativistic point particle. http://arxiv.org/abs/0908.0333 - Section 1 for example or Green, Schwartz, Witten Volume 1 Punchlines: 1) Time can be introduced as an operator but you need to introduce a 'proper time' parameter for which the system evolves with. In doing this you introduce a gauge ...

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My name is Sarah Huggins, about three years ago, my dad wrote an article on Wikipedia to demonstrate how nothing on the site is reliable. That article was The Huggins Displacement Theory. A couple years later, it's in three books, multiple movie and book reviews, and on physics blogs like this. He took the article down once it got flagged, but I thought I ...

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Let's say that at the outset, the observer on the platform has a wristwatch reading 12:00. He considers his own location to be point $0$. He considers the right side of the train car to be at location $x$. The light flashes. The train car continues to move. The light catches up to the right side of the train car at (say) 12:01 by the observer's ...

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First of all, the train is moving at constant speed (inertial frame of reference) so, to observers within the train, it must behave as if it were stationary. This means that the light takes the SAME amount of time to reach the left and right edges of the train. This can be objectively verified by putting two synchronized clocks, one at each end of the ...

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Actually your perception is correct in regards to the events you consider, but the conclusion does not contradict the concept of length contraction. In short, what you are looking at are simultaneous events in the train's rest frame. These do measure the length of the train in the rest frame, but not its contracted length as seen by the 'stationary' ...

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You say: The general relativity is based on Minkowski geometry but I suspect most of us would take the opposite view. If you take the Einstein equations and look for solutions where the stress-energy tensor is zero then you find a number of these vacuum solutions. These solutions include black holes, along with some very esoteric geometries, but if you ...

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Causality in special relativity implies that no signal can travel faster than light. In quantum mechanics, that does not translate in bounds on the speed of Dirac-delta wave-packets, not least because that would be in general an ill-defined condition (a localised wave-packet typically spreads out when evolving in time, so a delta at x=a would never evolve to ...

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Photons do not have an inertial reference frame because photons travel at the speed of light in any inertial reference frame, and obviously you can not have a frame in which the "at rest" particle is not at rest. In fact, as far as velocities allowed in an inertial frame go, the $c$ is the asymptotic limit - "asymptotic" meaning of course that $c$ is not ...

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If you seriously think the second principle goes without saying, then Galileo should be credited with discovering special relativity. The second principle basically asserts that the laws of electromagnetism are physical laws valid in all frames, not just laws that hold in the frame of a medium. And since that was an actual view back then, it needed and ...

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The necessity of anti-particles was first noticed when trying to construct quantum mechanical descriptions of particles that obey the relativistic energy-momemntum-mass $m^2c^4 = E^2 - (\mathbf{p}c)^2$ relationship. The Schrödinger equation is intuited from a combination of de Broglie's rules $E = hf$ and $p = h/\lambda$ and the classical Hamiltonian \$E = ...

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Anything with mass and/or energy warps space-time. When Light with different energy level passes through gravitational field of a massive object, higher energy will be attracted under the influence more than lower energy light. But, Higher energy of light particle will have more inertia than low energy particle. And since light of different energy level ...

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The laws of special relativity, of which the constant speed of zero mass particles in vacuum is a basic tenet , have been tested innumerable times with many experiments, particularly in particle physics. The Michelson Morley experiment has shown that there exists no luminiferous ether, i.e. there is no medium on which light propagates with this velocity c. ...

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See the question A Special Relativity Paradox: The Barn and the Pole in the Usenet Physics FAQ. Quoting part of the answer here. (The exact numbers differ a bit from your question, but that doesn't change the significant part of the question.) These are the props. You own a barn, 40m long, with automatic doors at either end, that can be opened and ...

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No. Photons do not experience the passage of time, as they are traveling at the speed of light. Remember when they discovered that neutrinos must have mass? Originally it was thought that neutrinos traveled at the speed of light, but then it was discovered that neutrinos change their flavors over time, which means that time must pass for neutrinos, which ...

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