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Everything posted by DanMP

  1. But in the case of your ring there is a surface, the table, and the vibrating ring may take advantage of the reaction force from it. See here a nice example of how bouncing can propel you if there is a medium that reacts.
  2. Well, I'm not sure, but it still may be the gravitational force to blame. It seems that when friction tends to zero, due to vibration, the ring is sliding to the right, in all experiments. The rotation may be caused by the red tape: the friction appears to be greater between the tape and the table than between the metal and the table ... There are also some forces from the cables ... In order to understand it better, you should: use a bubble level meter (to be sure that the surface is horizontal), reduce the tape/cable rotating effect by "gluing" the ring on a "plate" and minimizing the tension from the cables, and last but not least, remove the metal items around.
  3. In this case the vibration is less important (the car has wheels) and it hints that magnetic forces (from the metal items around) are more probably involved.
  4. The system is not isolated. As I wrote earlier you have metal items around and the table may not be perfectly horizontal, so the magnetic and/or gravitational forces may be responsible for the slide/momentum.
  5. I think the best answer until here was the one exchemist offered: So, the vibration that makes the friction with the table almost zero is from the "high frequency alternating magnetic field". You wrote "Driving Frequency approx. 5 KHz". See here that the sound/vibration in your videos has about 5 kHz. The external force that causes the slide may be gravitational (you didn't show with a bubble level meter that the table is perfectly horizontal) or/and magnetic ("I notice the table has metal legs and that there are various large metal components also on the table").
  6. It doesn't but thanks anyway. It sounded elaborate Ok, I knew that, but I think that behind any principle should be a reason, an explanation of what and why is actually happening. Wow! This is the best explanation. Thank you! +1 Another nice, comprehensive and useful explanation. Thanks! The underlining is mine and I did it because, in my opinion, the model, not the universe, cannot have only three spatial dimensions. And, as far as I know, this isn't the only possible model, there are graviton-based models in progress, modified Newton models and string theory attempts. Now I want/need to explain what I meant in my first post: in our world there are things we can feel, like apples and rocks, very real, things we define and measure, like temperature, pressure and time intervals, real enough, things like math, science models and words, real to us, humans, and very useful/powerful, but created not discovered, and things we created/imagined for fun, like unicorns. All these things exist for/to us, but they are not on the same footing. We kind of feel space by moving through it in all directions, so space is very real. In time we cannot move backwards, stop or "accelerate" forwards, so it is different. Needed, but different. In my opinion time is about change and the rate of change. We can observe change, so change is very real, but time is something made/created/defined by us in order to characterize the change, so it's less real. This is what I meant. In my understanding, to go back in time is to reverse all the changes in the whole universe. Do you see it different? How? And the last thing, if spacetime is not just a "tool" in our models, does it mean that the future is already "written", present in this spacetime?
  7. I didn’t say anything about biological ageing, which is a different matter. The principle of extremal ageing means that a test particle under the influence of gravity will tend to trace out that world line in spacetime which represents an extremum of proper time,... (Emphasis mine) Why "a test particle" would do something so elaborate? And how it knows how to do it, or to "tend" to do it? Why not? This reminds me something that may interest you: https://science.sciencemag.org/content/329/5999/1630
  8. Yes, time intervals are what we measure/observe. For this reason I said that time has a meaning when it's about time intervals. No disagreement here Regarding "time as a dimension" and its role in gravity: I'm not so convinced, probably because I don't know/understand enough. By the way, I admire your knowledge and the fact that you take the time to share it with us. I have some questions about spacetime (how/why exactly is warped around massive objects and why/how "the principle of extremal ageing" is imposed) but I don't want to hijack the thread, so don't answer this questions here if you think that this is not the right place.
  9. Time does exist, like temperature, pressure, the word time and so on, because we defined them. Space is real because we can move left-right, forward-backward and up-down. In "time" we can't move backward, so it's not as real as the space. Time has a meaning when it's about time intervals, like distances in space. Time as a dimension has less or no meaning. Yes. You can find in this forum my alternative theory, based on dark matter. It is intuitive, it is in agreement with the experiments/facts and it offers new experiments, able to prove it.
  10. If special relativity and all associated concepts such as Lorentz transformation, time dilation, length contraction ideas have been invalidated by your new theoretical framework, how you explain time dilation experimental confirmations (e.g. Hafele–Keating experiment)?
  11. I'm sorry to disappoint you but what I posted was a theory (not experiment) about waves of light through a medium, not single photons passing through slits, so I don't think it can support your "theory". Indeed. The reason I posted it was the fact/idea that many physicists are not really interested in "how is energy conserved" ... But they should be. You can't create photons/energy without consuming/absorbing an equal amount ... According to wikipedia so, if "The charges thus radiate their own electromagnetic wave that is at the same frequency" and "The light wave traveling in the medium is the macroscopic superposition (sum) of all such contributions in the material: the original wave plus the waves radiated by all the moving charges", the resulted wave (the sum) appears to "contain" more photons than the original/incident wave but, as I wrote above, you can't create photons/energy without consuming/absorbing an equal amount, so something is wrong ... What is wrong? [This is a bit off-topic (sorry!), so maybe we should move it (and continue) in another location.]
  12. This is a good point, in my opinion, but the microscopic explanation of how light is slowed in transparent materials suggests that new photons do occur (when we have a wave of light, not one photon at a time): and nobody seem to be bothered abut "how is energy conserved?" ... (Many physicists were more bothered by the fact that I asked the question: see 1, 2, 3).
  13. Ok what you did wrong was not the actual swapping, but the fact that you didn't notice that the notations were different. In your LT calculation (not derivation, sorry) S' was moving to the right, while in the geometrical calculation, S was moving to the right, as you can understand from the picture and its caption: As I wrote above, in order to compare the results, you have to keep the same scenario/notations, because (unfortunately) the notations are not the same everywhere, as you may see also in other 2 examples/derivations: https://www.amnh.org/learn/pd/physical_science/week3/time_dilation.html https://phys.libretexts.org/Bookshelves/University_Physics/Book%3A_University_Physics_(OpenStax)/Map%3A_University_Physics_III_-_Optics_and_Modern_Physics_(OpenStax)/5%3A__Relativity/5.3%3A_Time_Dilation
  14. The formula is the same. The problem is that you swapped the frames. Time dilation is usually calculated for a clock (it doesn't matter if it is a light clock as in your link or any other clock) and from a reference frame. In your LT derivation the clock was static in the origin of S' (the condition was x'=0), while in the geometric calculation the clock was static in S frame (the initial x' was different than the final x', while x was 0 all the time). So, in order to compare the results, you have to keep the same scenario/notations and to swap t' with t in one of the calculations.
  15. The above shows (correctly) that for "SC1: x' = 0, x = vt", when the primed clock (consider it a light clock) is in the origin of the S' frame (x'=0), moving with the speed v away from the origin of the S frame (x=vt), Lorentz transformations yield: t'= t/γ (where t' and t are in fact Δt' and Δt, time intervals from the moment t1'=t1=0 when x1'=x1=0). On the other hand taken from: (more precisely https://en.wikipedia.org/wiki/Time_dilation#Velocity_time_dilation) is valid for x=0, not for x'=0 as in "SC1" (where x' and x are in fact Δx' and Δx), so t and t' are swapped ... This is the origin of the "error". In fact Lorentz transformations are correct, as we all know.
  16. Ok, thank you! I apologize for insisting with this question.
  17. I'm sorry but it was you who insisted to talk about that particular derivation : I referred to your source, so I'm not really off-topic. Sorry anyway, I just wanted to understand it better. When I wrote "you", I meant:
  18. The origin of the confusion(?) is not really Jan Slowak, as you can see in the pdf offered here. This is odd, because it is the second time I posted this question in this thread. First time was yesterday. So, again, why v'=v (in value, because in fact v'=-v)?
  19. It is also unbelievable that you don't have an answer to my question. I'm still waiting ...
  20. Yes, but when in S' we write x' and t' ... Why not also v'? The speeds are not seen/measured identical from different frames, so why this time v'=v? [This question is addressed to all the participants in this thread, not just to Jan Slowak.]
  21. After I wrote the above (something you may have considered redundant/obvious) I wondered why v is the same, I mean when x' = 0, x = vt but when x = 0, x' should be -v't'. Why v' = v ?
  22. In the above quote (with y = mx + b) you are right, those two problems have nothing in common, but in the first quote (with x' = Ax + Bt) the "problems" are not independent, they are about exactly the same thing seen from different perspectives (different frames). When x' = 0, x must be vt, because at t=0, x' = x = 0 and the "x' frame" moved with the speed v. In the "Special Case 2", where x = 0, x' must be -vt', for the same reason. This is not random as in your example (SC1: x = 0, y = 5 and SC2: y = 0, x = 0). [I'm not absolutely sure that all I wrote is correct, but I think it may help.]
  23. So I need to buy the above article in order to see how you(?) explain the Sagnac effect through optical fibers, where the speed of light is c/n?
  24. If it really is "global/generalized", you must also take into consideration (and deal with) the cases where n, the refractive index, is greater than 1 (e.g. when light is traveling through optical fibers, with the speed c/n). Did you? Maybe it is (as I wrote in this here forum), but it is very well explained using special relativity, as you can see here.
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