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Inertial Frames of reference are fractals. You can imagine each Frame of reference as a box within a box within a box etc You can zoom in or out. The observer in each inertial "box" see the behavior of matter according to the laws of "classical"Mechanics == That is clocks run normally, mass is constant as is length. Example a car traveling at constant ...

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I don't think I can rigorously prove that simulation engines don't need to worry about the (possibly? I don't know if there's a reliable measurement) finite speed of gravity, but I can offer some lines of thought that point in that direction. I'll start with your question 3. Suppose that gravity does have finite speed equal to $c$. Your question seems to be ...

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It's tempting to think of gravity as some kind of interaction between the two bodies involved - maybe some form of signal (gravity wave?) sent between the two bodies. If this were the case then you would indeed have to allow for a propagation delay as the signals were sent between the two bodies. However this is not how gravity works. A massive object ...

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There is not a universal rest frame. There is, however, a galactic rest frame. Because you can look up at the stars, falsely assume that they do not change, and count your rotations that way. However, that method is only as reliable as the premise that the stars don't move, which they do slightly. The Hafele-Keating experiment used a variant of this, ...

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Leaving aside for a moment the comments made by dmckee et al, what matters is the angle of the measurement to the direction of motion. If an ether exists and you make a measurement along the direction of motion then you would get a different result to a measurement made at right angles to the direction of motion. It doesn't matter whether the right angle ...

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Remember that you must always specify the inertial frame of the observer. Other than that, your question makes perfect sense. The "closing" velocity of the two photons approaching each other will be 2c only in an inertial (stationary) observer at rest relative to the center point. To an observer "riding" with one of the photons, (either one), the closing ...

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Yes. The speed of light is independent from the direction and the reference system. In fact Michelson and Morley did their experiment in different directions and periods of the year in order to work in different earth revolution period, and they found always c.

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The question of what is the velocity of a photon relative to another photon does not make sense. Neither it does asking what is the velocity of anything relative to a photon. This is because in special relativity we only have the concept of a velocity defined for a massive observer, which is defined from the four-velocity $$u^\mu = \frac{d x^\mu}{d\tau}$$ ...

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The important thing is that all speeds seem to change: If you would look at the universe, in this case the two protons, from the perception of a man shrunk to the size of a proton, not only would the particles appear much faster, but so would the speed of light. So if you shrunk yourself to a trillionth of what you are now, one proton would have a diameter ...

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If I understand you correctly, your two points about apparent slowness of speeds is related to scale, and disappears when you quantify it using a common unit. ie: We think of 10m/s as relatively slow because the average human is 1.8 metres in height, and we can imagine that 10 metres per second, or 36 kilometer/hour as an achievable speed using a machine ...

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A "vertical variation of modern versions of the Michelson-Morley experiment (MMX) with one arm pointed in the vertical direction" experiment has been performed. Watch the following video starting at 0:45. http://youtube.com/watch?v=s9ITt44-EHE "Imagine the Earth as if it were immersed in honey," says Francis Everitt of Stanford University in California, ...

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There is certainly an interaction there between the optical medium and the photon. Actually, there are two photons in the interaction: the incoming one is absorbed by an electron in the material so that the latter fantastically fleetingly rises to an excited state. A fantastically short time later, another, outgoing, photon is emitted and the electron ...

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Lightspeed can be anything non-zero and finite for special and general relativity to work. Any medium, including vacuum, has a permittivity (electric field) and permeability (magnetic field). The permittivity ε and permeability µ of a medium together determine the phase velocity v = c/n of electromagnetic radiation through that medium, $\varepsilon \mu = ... 0 No, even if no particle does the entire trip, the pole has elastic properties, i.e., you push some molecules, and those push the next ones, and so on, until the information that travels with the pushes reaches the other side. You're basically sending a density wave through the pole. This video of a falling slinky in slow motion shows that. 0 If an object emits light in all directions at the speed of light ( no matter what the velocity of the object is), and the object is moving in the forward direction for instance, light is still emitted in this same direction at the speed of light, thus the object itself can not have been moving any faster than that light. Thus the object is confined in this ... 4 The way to do problems like this is always to use the Lorentz transformations. Choose some sensible spacetime points in the rest frame$S$and use the transformations to see what those points look like in the moving frame$S'$. In this case this is what the points look like in$S$: The spacetime points are labelled as$(t, x, y)$- we'll ignore$z$since ... 0 Light isn't a single vector. It propagates out in all directions, because it is a spherical wave. edit: I stand corrected, but I was trying to imply being able to a light pulse would require some sort of spherical wave reflecting off of particles in air. If in vacuum then you would not see the light ray. In this picture you wouldn't see anything because ... -2 There's no answer to this "Why". This is what we observe in nature. Nothing* can travel faster than light. *Note: Denizens of the Quantum World like atom may not be agree with this. For example, information of quantum states of two entangled entities are shared between them faster than light. It has been tested with polarized light beams. Understand it this ... -5 Because not until now that scientists discovered laws that can be applied on objects attaining even the speed of light .. actually no one knows what happens when an object attains the speed of light 7 http://en.wikipedia.org/wiki/Light_cone It simply says that some parts of the space-time are not accessible to us. For example I assume :-) you are on (Earth, Now). No matter what you do (Moon, Now) is not accessible to you. (Moon, Now + 1 second) is also not accessible to you, because the Moon is 1.28 light seconds away from Earth. Some events from the ... 0 I'm going to take a slightly different approach to explaining this, in analogy with a great answer about the ontological nature of Newton's Laws. First, let's posit the existence of an inertial reference frame. It doesn't matter which one, but there has to be one. This is an important point, and one that's often overlooked. In it, nothing is moving faster ... 2 The situation is too ill-defined for an answer. The problem there is that in general relativity, you do have general conservation laws that follow from the Einstein field equation. In the asymptotically flat case, you have conservation of a global ADM mass, and in all cases there is a local covariant conservation law that requires the stress-energy to be ... 3 Yes.$c$is the highest possible speed for light/any information to travel. So for a person 1 light year away, he wouldn't even realise that the object has disappeared, until the light carrying that information has travelled there. You can also think about this another way. Gravitational waves (which researchers today are trying very hard to detect) can ... 1 You have to measure everything from the same frame of reference. Your own frame of reference obviously has a velocity of 0, relative to you. The other object moving toward you, or away from you, will never move faster than the speed of light as seen from your frame of reference. A third observer can see two objects, each moving at the speed of light. Toward ... 4 The situation you described gives evidence that, if we really believe nothing can travel faster than the speed of light, the usual view of an electron actually orbiting the nucleus (like a planet orbits a star) can't be correct. The model of the atom you described, with electrons moving around the nucleus, also has other problems. Physicists noticed these ... 7 In the rest frame of the atom there are of course no changes, so I assume you're asking what the atom will look like to the stationary observer watching the moving atom. First note that electrons don't orbit the atom like planets orbiting a star. The electrons in atoms exist as a delocalised probability distribution. This distribution can have a non-zero ... 2 Your question is hypothetical since the universe is almost certainly not closed and will not recollapse (pace Andrei Linde). However if we assume an FLRW metric and a closed universe then all comoving observers will agree on the time between the Big Bang and the Big Crunch so the twins will have aged the same amount. If you have in mind a different scenario ... 1 The medium (the water or whatever else) has a preferred frame, that is its frame of rest. In that medium, the speed of light is not the same for all observers and it doesn't have to be because there is a special restframe now. In vacuum there is no such preferred restframe, that being the root of the principle of relativity. -2 Since this question is about how a photon can travel at light speed and yet have no mass, I will answer by saying that photons having no mass is precisely why they can travel so fast, and without mass, it becomes intangible for anything to make it go slower. 1 No. The speed of light is always c. And only that is constant to every observer. You use only c in Lorentz transformation. In some medium light would appear to slow down because it would jiggle electrons of atoms in that medium which would generate electromagnetic waves themselves. The combined result is a wave traveling slower in a medium. You can see it ... 11 It's c for constant or celeritas, which means speed in Latin. Everyone uses it because it's convention. You could use$\xi$or$\zeta$or$\gamma\$ or any other symbol you wanted, but then you'd have to explain what it meant, and people would have to go through the trouble to remember this every time they read your papers. Better to go with convention and ...

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Any phenomenon in the universe follows the principle of conservation of energy. Perpetual motion is possible when no external force acts on an object and the object is moving with constant velocity. The answer to your question is "yes". This is the reason why we can observe stars that are millions of light years away from us. In our universe this motion is ...

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The speed of any object is constant if there are no forces acting on the object. This applies to light and all other matter. Without forces (e.g. friction), an object that is moving will never stop moving. By "perpetual motion" people usually mean a machine that can produce more work than the work required to run it. It's hard to think of an everyday ...

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