bvr Posted July 31, 2016 Posted July 31, 2016 I think they are.A "light clock" (a system that counts the rebounds of a light signal between two mirrors) will evidently slow when it is in movement.But all clocks are sorts of light clocks.A "light ruler" (a system than determines the distance between two points by mean of a light signal) willevidently shrink when it is in movement.But all objects are sorts of light rulers.The "twin paradox" is easily solved when one realizes that the symmetry of the situation is merely theoretical. The two frames are not physically equal, although all laws of physics are the same and light speed = c in both frames, and no "proper" movement can be determined.I wonder why these explanations, which are truly compatible with Einstein's theory, are so rarely found.I wrote an article about some years ago: link deletedI hope it can help understanding the relativistic effects.
swansont Posted July 31, 2016 Posted July 31, 2016 I wrote an article about some years ago: link deleted ! Moderator Note Making a thread to link to your blog is against our rules. Anything you want to discuss should be discussed here.
michel123456 Posted July 31, 2016 Posted July 31, 2016 I think they are. A "light clock" (a system that counts the rebounds of a light signal between two mirrors) will evidently slow when it is in movement. But all clocks are sorts of light clocks. A "light ruler" (a system than determines the distance between two points by mean of a light signal) will evidently shrink when it is in movement. But all objects are sorts of light rulers. The "twin paradox" is easily solved when one realizes that the symmetry of the situation is merely theoretical. The two frames are not physically equal, although all laws of physics are the same and light speed = c in both frames, and no "proper" movement can be determined. I wonder why these explanations, which are truly compatible with Einstein's theory, are so rarely found. I wrote an article about some years ago: link deleted I hope it can help understanding the relativistic effects. You are correct there is no symmetry in the twins paradox. As there is no symmetry in the Hafele-Keating experiment. Be our guest and post your explanations here.
Enthalpy Posted August 9, 2016 Posted August 9, 2016 No symmetry is an explanation not so rare. I guess many authors and journalists still call it "paradox" by replicating other texts, and possibly to attract readers. Much like Schroedinger's cat is plain garbage, all serious people know it, but this story is still repeated from book to book.
Delta1212 Posted August 9, 2016 Posted August 9, 2016 Does someone think they aren't explainable? I thought the explanation was, you know, relativity.
michel123456 Posted August 9, 2016 Posted August 9, 2016 Does someone think they aren't explainable? I thought the explanation was, you know, relativity. They are all explainable. They are not all understandable.
Strange Posted August 9, 2016 Posted August 9, 2016 They are not all understandable. That is observer dependent. 4
bvr Posted August 9, 2016 Author Posted August 9, 2016 Does someone think they aren't explainable? I thought the explanation was, you know, relativity. I see, on many forums and other places, many questions asked by many intelligent people, struggling with the concepts of time dilation, space contraction, "light" speed constancy etc. No symmetry is an explanation not so rare. I guess many authors and journalists still call it "paradox" by replicating other texts, and possibly to attract readers. Much like Schroedinger's cat is plain garbage, all serious people know it, but this story is still repeated from book to book. No symmetry is indeed a common argument, but it's almost always given as a superficial explanation: of course there is no problem, since the two situations are different. But thinking further, it's not that simple, especially when trying to explain what is happening, concretely and physically, in the traveller's reality.
MigL Posted August 9, 2016 Posted August 9, 2016 Relativity doesn't 'cause' the effects. These effects are just the normal workings of the universe. Relativity EXPLAINS the effects. ( if you understand it correctly- as Strange points out ) 1
bvr Posted August 11, 2016 Author Posted August 11, 2016 IMHO if many people do not understand it correctly, it's because it is not explained correctly.
michel123456 Posted August 11, 2016 Posted August 11, 2016 (edited) IMHO if many people do not understand it correctly, it's because it is not explained correctly. To me it is even worse: it is because the people who explain it do not understand it. It was a time when almost nobody could understand GR. Now anybody is entitled to understand. “Asked in 1919 whether it was true that only three people in the world understood the theory of general relativity, [Eddington] allegedly replied: 'Who's the third?”― Arthur Stanley Eddington Edited August 11, 2016 by michel123456
swansont Posted August 11, 2016 Posted August 11, 2016 IMHO if many people do not understand it correctly, it's because it is not explained correctly. In some cases, perhaps. But blaming the teacher is a convenient way to avoid any personal responsibility the student has for learning. 1
Delta1212 Posted August 11, 2016 Posted August 11, 2016 To me it is even worse: it is because the people who explain it do not understand it. It was a time when almost nobody could understand GR. Now anybody is entitled to understand. There was a time when almost nobody understood how to work a computer. Now anybody is entitled to understand. There was a time when almost nobody understood what electricity was. Now anybody is entitled to understand. There was a time when almost nobody understood how biological inheritance worked. Now anybody is entitled to understand. There was a time when almost nobody understood how oxidation worked. Now anybody is entitled to understand. There was a time when almost nobody understood how to use calculus. Now anybody is entitled to understand. Science marches on. When something is new, very few people understand it not because it is impossible to learn, but because very few people have tried to learn it, the resources for learning it are generally very scarce, and people's base education was generally not geared toward laying the foundations for learning that subject. Eventually all of those things stop being true. What was bleeding edge because core knowledge. People become more open to the ideas instead of spending a large chunk of their learning time trying to find the seams and poke holes in it. Foundational knowledge takes the new late stage knowledge into account and students become aware that that knowledge exists much earlier even if they don't learn it directly. Fields and technical professions get bolt up and around it so that it is required knowledge by many more people just to do their jobs rather than more esoteric knowledge of interest to only a few. It's hardly surprising that a paradigm changing theory would go from only being understood by the person who developed it to being very widely understood by the scientific, engineering and science-minded community at varying levels. That's not evidence that everyone is misunderstanding it because only Einstein was capable of knowing how it worked. That's just how humanity tends to learn things as a collective.
Endy0816 Posted August 11, 2016 Posted August 11, 2016 (edited) I don't get why people are so set on fixed values in the first place :/ Edited August 11, 2016 by Endy0816
michel123456 Posted August 11, 2016 Posted August 11, 2016 I don't get why people are so set on fixed values in the first place :/ What do you mean?
bvr Posted August 11, 2016 Author Posted August 11, 2016 In some cases, perhaps. But blaming the teacher is a convenient way to avoid any personal responsibility the student has for learning. I agree on that, but not in the context of SR. The theory is not difficult to learn. The difficulties are rather ontological, but quite neglected in physics lessons.
swansont Posted August 11, 2016 Posted August 11, 2016 I agree on that, but not in the context of SR. The theory is not difficult to learn. The difficulties are rather ontological, but quite neglected in physics lessons. You miss the point. There are things you can work out for yourself.
StringJunky Posted August 11, 2016 Posted August 11, 2016 (edited) In some cases, perhaps. But blaming the teacher is a convenient way to avoid any personal responsibility the student has for learning. It's a mathematically-based science at the end of the day that requires concerted effort on the part of the learner. You can inform someone but you can't do the thinking for them as well. To paraphrase Einstein: one can only explain things as simply as is possible but there's a limit to how simple before it becomes useless. Edited August 11, 2016 by StringJunky
Markus Hanke Posted August 12, 2016 Posted August 12, 2016 It was a time when almost nobody could understand GR. Now anybody is entitled to understand. That is because we now live in a world where it is easy to access the required information, and learn about the model. Not too long ago, the necessary resources ( i.e. textbooks ) were something only found in major university libraries, so the vast majority of the general populace had little incentive to go and access it; nowadays, most of the needed information is only a Google search away, and hence available to anybody who is interested in the subject matter. Also, at its heart, GR is just really simple geometry - all those tensors with their indices and fancy symbols look intimidating at first, but the underlying principles of geometry are very straightforward, and can be understood by anybody. The major issue I see is that there is a lot of misleading and plainly wrong information about GR out there, and the average Joe will not have the required knowledge to judge the accuracy of any given source. The pop-sci media has a lot to answer for, in that regard.
swansont Posted August 12, 2016 Posted August 12, 2016 Consider that you need time to pass before any new discovery makes it into the textbooks and gets taught more broadly to students, who get to have that as part of their schooling rather than as a new finding — it often takes time for new ideas to become ingrained into one's thinking. Plus, "understanding it" and "understanding it well enough to do research and contribute to the field" are two different levels of understanding. Also, when Eddington made his pronouncement, even basic GR was still being refined. A lot is different today compared to 100 years ago, in terms of GR.
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