Lazarus Posted October 1, 2014 Author Share Posted October 1, 2014 I do like dherries. The whole article is questioning the validity of the bending of the light passing the sun as a proof of General Relitivity. Th GR equations work but apparently other equation also work. Link to comment Share on other sites More sharing options...
elfmotat Posted October 1, 2014 Share Posted October 1, 2014 The whole article is questioning the validity of the bending of the light passing the sun as a proof of General Relitivity. No it isn't. You should try rereading it. It takes a shortcut by using the fact that the non-Newtonian additional deflection is due to spacial curvature, and the factor contributing to the extra gravity is the same as the Doppler-shift factor. Also, there's no such thing as a "proof" of a theory. This is science, not math. Link to comment Share on other sites More sharing options...
Lazarus Posted October 5, 2014 Author Share Posted October 5, 2014 To accommodate the conservation of energy, when a photon moves from one gravitational level to another, something must change. The simplest solution is a change to the speed of the photon and there is evidence that it does change. The difference in the speed is hardly noticeable because the change in latent energy pales in comparison to the kinetic energy at the speed of the photon. Since the speed of photons is related to the gravitational latent energy, the only place the base speed of photons can be determined correctly is at a location with zero gravity, the value of c could have been measured wrong on Earth. We talk about the speed of light in a vacuum but did we take zero gravitational force into account? Link to comment Share on other sites More sharing options...
swansont Posted October 5, 2014 Share Posted October 5, 2014 You get a red or blue shift for a photon that changes height. Confirmed with the Pound-Rebka experiment Link to comment Share on other sites More sharing options...
Lazarus Posted October 5, 2014 Author Share Posted October 5, 2014 You get a red or blue shift for a photon that changes height. Confirmed with the Pound-Rebka experiment A faster photon would have more energy as does the blue shifted photon. Does the photon maintain the same speed or does it share the energy with the blue shift or even cause the blue shift? Link to comment Share on other sites More sharing options...
swansont Posted October 5, 2014 Share Posted October 5, 2014 Photons travel at c, but that has to be measured locally. Link to comment Share on other sites More sharing options...
Lazarus Posted October 14, 2014 Author Share Posted October 14, 2014 In trying to make sense of the light bending I wound up with a confusing example. The situation is one guy standing still and another guy running up from behind. Just as the two guys are side by side, light arrives from a distance. One guy says the light is red but the other guy says it is blue. (He runs pretty fast.) Now regardless of the “frames” the light travels at c in relation to both guys. How can we account for the blue shift? Link to comment Share on other sites More sharing options...
Strange Posted October 14, 2014 Share Posted October 14, 2014 Classically, you can view it as the runner encountering the waves faster because he is running through them. Or, you can think of it in terms of energy. If it were a tennis ball, they would disagree with the kinetic energy the ball has. Similarly, they disagree about the amount of energy the photons have; in other words, different frequency. Link to comment Share on other sites More sharing options...
swansont Posted October 14, 2014 Share Posted October 14, 2014 Energy is not an invariant quantity. No "accounting" necessary. 1 Link to comment Share on other sites More sharing options...
Lazarus Posted October 15, 2014 Author Share Posted October 15, 2014 Energy is not an invariant quantity. No "accounting" necessary. What do you mean. Almost everything is “not an invariant quantity.”. Dust on the floor is “not an invariant quantity.”. Link to comment Share on other sites More sharing options...
elfmotat Posted October 15, 2014 Share Posted October 15, 2014 What do you mean. Almost everything is “not an invariant quantity.”. Dust on the floor is “not an invariant quantity.”. "Invariant" means "the same value in all reference frames." The number of dust particles on the floor actually is an invariant quantity. The energy of a particle is not. Energies depend on your reference frame. Link to comment Share on other sites More sharing options...
Lazarus Posted October 15, 2014 Author Share Posted October 15, 2014 "Invariant" means "the same value in all reference frames." The number of dust particles on the floor actually is an invariant quantity. The energy of a particle is not. Energies depend on your reference frame. I failed to realize the specialized use of invariant. Does this equation give the correct path for a comet passing the sun? You get a red or blue shift for a photon that changes height. Confirmed with the Pound-Rebka experiment The Pound-Rebak experiment has two possible explanations. The photon accommodates the latent energy change by increasing its energy resulting in the observed blue shift. Or the alternatively, the resonate frequency of the iron atoms is different because of the different gravitational potential. The photon is unchanged but the resonate frequency doesn’t match. Link to comment Share on other sites More sharing options...
Strange Posted October 15, 2014 Share Posted October 15, 2014 The Pound-Rebak experiment has two possible explanations. As far as I know, one of those explanations corresponds to a scientific theory and the other doesn't. Link to comment Share on other sites More sharing options...
elfmotat Posted October 15, 2014 Share Posted October 15, 2014 I failed to realize the specialized use of invariant. Does this equation give the correct path for a comet passing the sun? In the context of relativity, which is what we're discussing, "invariant" is synonymous with "the same in all reference frames." That equation is in my signature, it has nothing to do with this thread. Link to comment Share on other sites More sharing options...
Lazarus Posted October 15, 2014 Author Share Posted October 15, 2014 That equation is in my signature, it has nothing to do with this thread I wondered about that. Link to comment Share on other sites More sharing options...
swansont Posted October 16, 2014 Share Posted October 16, 2014 I failed to realize the specialized use of invariant. Does this equation give the correct path for a comet passing the sun? The Pound-Rebak experiment has two possible explanations. The photon accommodates the latent energy change by increasing its energy resulting in the observed blue shift. Or the alternatively, the resonate frequency of the iron atoms is different because of the different gravitational potential. The photon is unchanged but the resonate frequency doesn’t match. This is why it is important in science to not focus too narrowly on a problem, because all phenomena must match a theory — everything in physics is related to something else in physics. If the photon frequency doesn't change, for example, you violate conservation of energy, so now you have to fix that, and anything else that breaks as a result. It all tumbles down like dominos. Link to comment Share on other sites More sharing options...
Lazarus Posted October 17, 2014 Author Share Posted October 17, 2014 This is why it is important in science to not focus too narrowly on a problem, because all phenomena must match a theory — everything in physics is related to something else in physics. If the photon frequency doesn't change, for example, you violate conservation of energy, so now you have to fix that, and anything else that breaks as a result. It all tumbles down like dominos. Damn, you are good at hitting the essense of the problem. The consevation of energy is the best argument against choice number two. However, an argument can be made that conservation of energy is not violated because if speed of the photon can not be increased or decreased by gravity there is no energy required for it to escape gravity. Link to comment Share on other sites More sharing options...
Lazarus Posted October 19, 2014 Author Share Posted October 19, 2014 swansont Posted 14 October 2014 - 02:40 AM Energy is not an invariant quantity. No "accounting" necessary. ................................................................................................. The variability of energy is an interesting but confusing concept. In the example of the two guys, one stationary and the other moving, the photons appear to each of them as arriving at the same speed. Therefore, the frequency should appear the same to both of them. But it doesn’t. One is blue shifted. So what is the reason for the blue shift? Link to comment Share on other sites More sharing options...
elfmotat Posted October 19, 2014 Share Posted October 19, 2014 swansont Posted 14 October 2014 - 02:40 AM Energy is not an invariant quantity. No "accounting" necessary. ................................................................................................. The variability of energy is an interesting but confusing concept. In the example of the two guys, one stationary and the other moving, the photons appear to each of them as arriving at the same speed. Therefore, the frequency should appear the same to both of them. But it doesn’t. One is blue shifted. So what is the reason for the blue shift? Frequency of a wave is not the same as speed of a wave. The frequency is how many times it oscillates per second. The speed is how fast it travels. Two waves can have the same speed and different frequency. The fact that energy is not an invariant quantity is not new. This was obvious even in Newtonian physics. For example: if you toss a ball it will have some kinetic energy. But in the ball's rest frame it has zero kinetic energy. Thus energy is not invariant. Link to comment Share on other sites More sharing options...
Lazarus Posted October 20, 2014 Author Share Posted October 20, 2014 Frequency of a wave is not the same as speed of a wave. The frequency is how many times it oscillates per second. The speed is how fast it travels. Two waves can have the same speed and different frequency. The fact that energy is not an invariant quantity is not new. This was obvious even in Newtonian physics. For example: if you toss a ball it will have some kinetic energy. But in the ball's rest frame it has zero kinetic energy. Thus energy is not invariant. In the blue guy's rest frame the photons look the same to him as the red guy's do to him. Why are the blue guy's photons blue? I know this is similar to the last question but I can't see how that explains it. Link to comment Share on other sites More sharing options...
elfmotat Posted October 20, 2014 Share Posted October 20, 2014 In the blue guy's rest frame the photons look the same to him as the red guy's do to him. Why are the blue guy's photons blue? I know this is similar to the last question but I can't see how that explains it. Because they have different energy according to blue guy and red guy. (I feel like we're going in circles here.) Say Alice is moving relative to Bob. Bob tosses a ball in the direction Alice is moving. In Alice's rest frame the ball has less energy than in Bob's rest frame. It's the same situation, only with light. It doesn't matter that the light moves at the same speed relative to Bob and Alice, they still report different energies because the energy of a photon isn't related to its velocity! It's only dependent on its frequency, which can be different for two waves that move at the same speed. Link to comment Share on other sites More sharing options...
swansont Posted October 20, 2014 Share Posted October 20, 2014 swansont Posted 14 October 2014 - 02:40 AM Energy is not an invariant quantity. No "accounting" necessary. ................................................................................................. The variability of energy is an interesting but confusing concept. In the example of the two guys, one stationary and the other moving, the photons appear to each of them as arriving at the same speed. Therefore, the frequency should appear the same to both of them. But it doesn’t. One is blue shifted. So what is the reason for the blue shift? The Doppler effect Link to comment Share on other sites More sharing options...
Lazarus Posted October 25, 2014 Author Share Posted October 25, 2014 The explanations from all the posters have been clear, logical and easy to understand but the answers to the last question don’t appear to meet that standard. But never mind, let’s see how Newton would have done the calculation if he had been informed of the results of modern experiments, that the speed of light in a vacuum had been determined to high precision, that light traveling from Earth to Venus and back took longer than expected, that mass was related to energy, that the frequency of light changed with changes in gravitation potential, that matter is constrained to the speed of light, that light can be treated as a collection of particles and that the path of light changes while passing a massive body. A reasonable assumption from the Venus experiment is that light slows as it encounters increasing gravitational potential. Since light slows while approaching a mass is opposite from what would be expected the potential energy change must be accounted for by an increase in internal energy which is reflected in the frequency. The bending of the path of light by a mass requires that the internal energy increase be twice the loss of kinetic energy of the light. The slowing of the speed of the light causes the amount of bending to be more that if the speed of the light stayed constant or increased as do masses. That should make the calculations give the same result as my friend Albert’s equations. Link to comment Share on other sites More sharing options...
swansont Posted October 25, 2014 Share Posted October 25, 2014 That should make the calculations give the same result as my friend Albert’s equations. Should make or does make? Link to comment Share on other sites More sharing options...
Lazarus Posted October 25, 2014 Author Share Posted October 25, 2014 Should make or does make? If you would be satisfied that there is a correct solution to the bending of light by the sun from these assumptions which does not require the Relativistic assumptions, I will construct an equation even though I can’t even remember how to spell kaculus much less how to use it. Most of the posters on this forum could do it with these assumptions over a hot beer. Link to comment Share on other sites More sharing options...
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