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md65536 last won the day on September 3 2019

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  1. To do it from a diagram like that, you can rotate the image 180 degrees, then overlap the ellipses. Here the two suns are the foci. Obviously the accuracy will be limited by image quality but for example you can see that the foci of Mercury's ellipse are farther apart than Earth's, and that Mercury is on the order of 3/2 as far from the sun at aphelion as it is at perihelion. Mercury: Earth:
  2. Couldn't you just find the distance from the first focus to Mercury at perihelion, and the distance from the first focus to Mercury at aphelion, then take a vector from the first focus toward the point of aphelion, with a length that's the difference of the two distances? Even if those values are determined by an accurate-enough simulation, that should be easy. According to wikipedia, the difference is 23.8 million km, so that's approximately how far apart the foci should be (neglecting the sun's wobble). That's more than half the distance between Mercury and the sun at perihelion. Mercury's orbit eccentricity is huge (0.2056) compared to Earth's (0.0167).
  3. If you're simulating Newtonian gravity, then all you need to get an elliptical orbit is to give the smaller mass a velocity. Then calculate updated positions and velocities, using gravity for acceleration. The data would be mass of the sun, location of the planet relative to center of sun, and velocity at that location. Or if accurate relative positions aren't important, just distance from the center of the sun at apogee or perigee, and speed at that point (oriented 90 degrees from the sun) will do. Simply updating position, velocity, and acceleration iteratively ("Euler method") can give a good approximation for simple visualization. I'd be curious to see if you can find eg. the max deviation in distance between Mercury and the sun, based only on those data. You would know you have a small enough step size, when making it a lot smaller (eg. half) doesn't change the results much.
  4. As MigL suggested, your idea is to warp space with a system of energy that has much more mass than the ship? And it pulls you along as you fall toward it? But to travel anywhere, wouldn't you have to accelerate it (using much more energy than accelerating the ship, since it's much more massive)? Are you imagining something with a lot of gravitational mass but little inertial mass? I don't think anything known or predicted is like that.
  5. Is that a fact? A spacetime interval can have a length that's positive, negative, or zero, so that value is not always negative. Also, you're talking about a metric signature (+ + + -) which is only a convention, but so is (- - - +). A measure of proper time uses the latter. Then, ds^2 is negative for spacelike intervals, and positive for timelike. As for physical significance, could you say that the proper time along a spacelike interval is imaginary?
  6. I agree that shutting it down was justified, but it went from indulging OP's avoidance of simple questions, to brushing off everyone's questions, with no warning and nothing in between. A warning a few pages earlier could have prevented both rambling posts AND people bothering to continue asking serious questions. Also, the topic was started in Relativity I think, and I was reading it only through notifications of replies. I didn't see any indication that it was moved to Speculations, and that replies were no longer considered worth anything.
  7. For example, a post on SR that was moved to speculations was closed recently. The reply immediately before it was closed was from someone asking questions to OP. The problem is that the topic was closed only due to OP's behavior, but there were other people in the thread. This suggests that OP "owns" a bad topic, even if others are discussing reasonably. It would be nice to instead see a warning, like "Stop posting what you're posting. You have a chance to answer questions others have asked. If you don't take it, the thread will be closed." Or a warning to others: "Don't bother asking any questions, we're not giving OP more chances to answer." Even if all indications are that anyone else posting in the thread is having their time wasted, it's still good to know whether our questions or corrections or suggestions made any difference. If closing a topic is justified, the note about its closing could address everyone participating in the discussion.
  8. Are you talking about some aspects of SR that can be observed without referring to different clocks etc., or are you saying all of SR can be understood without them? If you separate two clocks and bring them together again, one might have measured a longer time than the other. Do you explain that without saying one ran faster or slower than the other, or is that not one of the aspects of SR that you're talking about, or are you saying that wouldn't happen?
  9. Yes, extra connections don't seem to add any meaning. The Krasnikov tube wiki you linked has an example with 2 one-way tubes that can bring you to Earth 6000 years before you departed. Not that that's assumed to be possible, but a connection between Earth 6000 years apart wouldn't make it a common 'now' away from that connection.
  10. Does GR tell you how much time is measured outside the warp "bubble" or at the other end of a wormhole? Or "when" it is on the other side? With the Alcubierre drive, is there a horizon between inside and outside, so you can't interact with the outside? Suppose there was a way to create the warp in one place, and something else to cancel it out in another place, so you could travel there. Then suppose there was a way to do that in the opposite direction, so you can come back. Does GR tell you when you'd come back? Eg. if you could spend a day traveling at 10c, then immediately spend a day returning at 10c, is the idea that you could return to Earth with 2 Earth days having passed? Or is it some other time or unknown or undefined? When it comes to the wormholes, "when" is it on the other side of the wormhole? Is that arbitrary? Can you have a wormhole or a series of them connecting you to beyond our visible universe? I can't make sense of the idea of "now" on the other end of a set of wormholes, yet no universal now. For example, if you had 3 extremely distant events A, B, and C, each connected to each other with a wormhole, either the relative timing of the events would be arbitrary, or it would establish a common 'now' between the 3 locations???
  11. Populated with what? Measurements of A? Or a prediction, based on the LT or the underlying definition of simultaneity? If simultaneity was not defined, could B say what the time at A "really" was? Is there for B, a physical "now" at the distant location A independent of that definition? Would you say that Einstein was wrong in writing that such a definition is needed? I didn't say "current". I said B can measure the total ageing of A without ever considering what the "current" or "real" time at A might be. It can measure what the time at A appears to be, using only the local current time at B. Why? He didn't, and got the right answer, never assuming anything at all about simultaneity. You say the speed of light must be considered, but don't you mean the one-way speed of light? B only needs to care about incoming light from A, to determine everything it needs to know about A, right? What is the one-way speed of incoming light? How do you know that light takes time to arrive? I'll just tell you the answer: You know it because the time it takes incoming light to cross a fixed distance is defined to be the same as the time it takes outgoing light to cross the same distance. You're wrong to say you "must" come to the same conclusion to be able to predict the ageing of A. I've just shown, B can predict the total ageing of A using only the relativistic Doppler effect, which is a real measurement that can be made without relying on any definition of simultaneity, and gives you the same answer regardless of how you define the "current time at a distant location." I'll just assume you're still using your own meaning of the word 'theory'. Both the LT and the relativistic Doppler effect can accurately let B predict the total ageing of A. Would you say there is no way to know which one matches reality? So, accepting that you can't know the answer to the question, you conclude that it must be the answer most reasonable to you? Can you conceive of the idea that the inability to measure the 1-way speed of light is the one "theory" that matches what is real??? It's not that a way to measure it hasn't been figured out yet, it's that there's no accepted theoretical way in which such a measure can meaningfully be made. It's like saying "Measurements of the Ether are all consistent with the fact that it doesn't exist," and someone arguing "I agree. Even though it exists, we may never have the ability to detect it." I agree! Einstein in fact did say something along those lines. He said, "in reality it assumes absolutely nothing about light" as I've quoted. In his 1905 paper he wrote, and then defined the equal timing of light signals in opposite directions. Thus he literally said that 1) we "might content ourselves" with an alternative, which I take to mean that it can provide workable solutions, and 2) a justification of the definition he used is that it is more practical. He knew what he was doing and didn't get mired in trying to base the theory on what he thought to be "real", only what agrees with experience.
  12. What's the definition of a clock's "existence" in another observer's frame? What if B doesn't know of relativity, and says "A's existence spans 2 of its years on my outbound journey, and 8 years on my inbound, and I've measured that to be true"? How can you prove to B that it's wrong and that your description of existence is the right one? Can you convince it that what it measures (2 + 8 years observed) is wrong and your numbers (unmeasured, but later verified to be consistent with a particular definition of simultaneity) are the ONLY ones that can be real? And can you do this without relying on Einstein's definition of simultaneity or an equivalent? Do you think that when Einstein defined simultaneity in such a way that real-world events could be tested against that definition to determine if they fit it or not, he actually did much more than that, and actually defined existence? Or could it be that his definition so perfectly aligns with your assumptions about reality, that you figure he is proving your assumptions correct simply by definition?
  13. That's wrong. B can SEE A ageing. B predicts that A's clock can be seen ticking at a rate of 0.5x its own, for 4 of B's years, and then ignores whatever happens at A while B turns around, then predicts A's clock can be seen ticking at a rate of 2x its own, for 4 of B's years. So it predicts A will be seen ageing 2+8 = 10 years, plus whatever it ignored. Why must it predict 6.4y, when it can predict the correct value? The rest of your post, you just keep repeating a similar false claim over and over. There's no such thing. Distant simultaneity isn't sensed. B doesn't "sense" a change in the time at A while it turns around (in negligible time). The coordinate time at A changes BY DEFINITION of simultaneity given by Einstein. Do you not accept that? You say his definition is a convention and then give pages and pages and pages of arguments that it's not. I've not convinced you of anything, and I'm repeating the same thing over and over, I give up. No thanks. I don't think that all of the unnecessary complications you're adding will help to understand the uncomplicated case. So start with something that makes sense. Don't just make random changes, choose the idea that you're trying to model. If you only change things that do not influence any real measuring device readings then the end result should agree with reality. Assume your "fused spacetime continuum" if you want. Just *don't* change something that doesn't affect real measurements, end up with something that agrees with reality, and then conclude that your changes must represent "true reality". (For example, choosing a random privileged frame will agree with reality, that doesn't make its privilege real.) Also don't take existing definitions that don't affect real measurements and conclude that they must represent "true reality".
  14. There's another simplification that can be made. How do you know what's a realistic acceleration? We could be talking about twin neutrinos. If we're talking about rockets, the physical properties of the rockets aren't given. That's fine because they don't matter. The mass of the object that accelerates doesn't factor into the SR equations. Therefore it can be simplified out. We can talk about abstract twin particles. Imagining they're something specific, just adds red herrings. Sure, but they're synchronized only (generally speaking) in the Earth/A/X inertial frame. Ie. B is momentarily at Planet X and at rest with it. B's now in A's inertial frame, and agrees with A's (X's) measurements: A is 3 LY away, and A's clock is Einstein-synchronized to X's, which reads 5 years (per OP's specs, halfway---according to any of A, B, C---through the experiment). Nah! How would you measure that sweep at A? You can definitely predict it, using SR, but if you didn't know SR but had any conceivable measuring device you can imagine, how would such a device measure (not predict) that sweep? If you can unambiguously measure it, I'll agree it's the only outcome consistent with reality. Just checking we're on the same page: What does X's clock read when B reaches it, comes to rest with it, and then leaves again (all in negligible B's proper time)? That's what makes it a philosophical argument, not a scientific one. Scientific theories do not pick a choice they think is "real" based on Occam's razor. You don't settle eg. Copenhagen interpretation or string theory based on Occam's razor. You also don't have to because the questions answered by science are about quantitative predictions, not "which model is the one true description of reality?". The conventions used in SR are not about picking a choice that one thinks is "real", it's about ... again, in Einstein's translated words: "that in every real case it must supply us with an empirical decision as to whether or not the conception that has to be defined is fulfilled." Ie. it is chosen because it is useful in making measurements. Any conventions that give you measurable predictions that equally agree with reality, are equally real. You need a different measurement given by different conventions, to be able to physically evaluate which is more "true-to-nature". Occam's razor tells you nothing about that, but it can tell you which are more practical than others.
  15. A possible way forward is to treat c as a constant local speed of light, as it is in GR. It might be possible not to worry about the speed of anything measured from a distance, in your equations? I don't recommend following any of my advice on anything, unless you agree with it! I'm 100% sure you understand the technical details better than I do. If you're interested in testing whether your results are in agreement with SR, you might try deriving the Doppler effect including any of your alterations. If it doesn't give the exact same values as SR, it's not going to agree with real measurements as SR does. But also, I'm not sure what you're working to accomplish, so I don't want to suggest more work. I think we'll never agree, because of philosophical differences. Of course, SR doesn't depend on philosophy, and I think anything "purely" philosophical is not part of the theory. The way I see it... SR is correct, independent of experimental validation. The theory is purely mathematical. You start with some assumptions and mathematical rules, and you end up with some consequences. It is an exact, error-free model. Experimental validation deals with how well that model corresponds with reality, not whether or not it is correct (or complete, or whatever). We find that when measuring the universe, it really does seem to adhere to the assumptions and rules that SR uses, and thus the predictions made by SR are accurate in the real world. Philosophically, the only things I treat as "real" are what are measurable. If there's some mathematical prediction or description, like "A sweeping contiguously through time relative to B in the instant B accelerates", but it is not measurable, for me it's just a part of the model, not something real. For me, it makes so much more sense when everything "optional" is left out (cut off by Occam's razor). That's why I like OP's experiment. Changing from "B and C pass by each other" to "B turns around" doesn't change the prediction, so there's nothing real in that left to figure out.
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