Tim88

You said instead that it is not a property of the object. [edit:] In fact, you exclaimed "Absolutely not" to the above cited reflection "objects seem to possess [motion] yet they don't in isolation" by Rasher. It does sound as if you don't understand the philosophical basis (also related to the non-universal definition of words). Let's try this (emphasis mine: Was I wrong in thinking that you probably disagree with that?

I hope you are realizing that you are asking philosophical questions in a physics forum. The answers you get are therefore just opinions most of which cannot be proven and don't really belong here. For example, Newton appears to have considered motion to be a property just as you reason here; Strange thinks differently, and his disagreement with Newton is his right. Such philosophical statements about motion and time are not physics proper. It's important to understand that! What is great about scienceforums (just my impression as newcomer ) is that it also has a philosophy section.

Well, that kind of reasoning went in a flash through my head at the moment that I typed my first comment that the car's synchronization will be messed up; it seemed pretty safe to claim that the synchronization would be off. And in most cases that's no doubt correct. No, not at all - I can't understand how you can assume that I made use of complex equations that are unnecessary for the analysis. Instead, as you can read in my first post, I used physical reasoning - just like Einstein did when stating "It is at once apparent" (§4). This is also a bit like Bell's spaceship paradox, as Bell similarly used physical reasoning while his colleagues used complex formula's. So, it will be difficult to find a mistake in your hyperbolic curves or their interpretation if you made one, due to their complexity. In contrast, if I made a mistake then it should be very easy to spot! If anyone sees a problem with any of the points 1-4, or has questions about them, please tell. PS I did not see this particular case anywhere else; but of course the literature is huge. Anyway, we won't need it as it's quite simple.

Bold face mine: I'm not writing an article, just trying to have a discussion with valuable output: the aim is to end with posts that will be useful for referencing in other discussions. Indeed, I had not seen that post by you; but even if I had, I don't see the relevance for the question of a need to resynchronize for this special case. As already explained, I consider my original statement about resynchronization erroneous due to a subtlety of the scenario that I had overlooked, even though you next gave support to it with a statement that according to me is explicitly erroneous. Now, to my surprise you still don't notice the issue but continue to support my original statement. This has nothing to do with philosophy and it is both pertinent and useful for SR, so I'll spin it off: http://www.scienceforums.net/topic/99360-does-a-change-in-direction-turnaround-result-in-loss-of-synchronization/

In the philosophy forum we are discussing interpretations of the car scenario that was earlier discussed in this forum. The car has two synchronized clocks. While rehashing it, I turned it "on the fly" into a twin scenario by letting the car do a turnaround. To keep it simple, a let the car take a sharp turn without changing speed. Without much reflection I stated that after turnaround the car's "reference system has been messed up: the speed of light doesn't seem the same anymore in both directions" because the clock synchronization was done for a different inertial reference system. Mordred added that "A change in direction results in loss of synchronization (turnaround)" But when looking at it more carefully, I realized that I had based my statement on a different scenario with linear acceleration. And according to my new analysis, our statements were wrong. Here's my analysis, which is very simple, all from the perspective of the ground frame: 1. The car's rear clock is advanced on the front clock by a time difference D, such that for the car the speed of light appears isotropic relative to the car. 2. In this particular case the clock rates are kept identical and constant, because (neglecting the asymmetry of the car) both clocks keep on moving at the same speed even while taking the turn. 3. Accounting for the turnaround, the time difference is still D. 4. After taking the turn, the front clock is still in front and the rear clock is still at the rear. It's just the mirror case of the first leg of the trip. In other words, concerning the car we have the same physical situation as before: the car is still moving at the speed v with a clock synchronization that is the standard one for that speed. No resynchronization is required to newly obtain a measured speed of light c in both directions.

Maybe this is mostly about words? The discussion concerns physics and metaphysics - natural philosophy. In the common definitions of words, physical objects have three dimensions - the spatial dimensions. The 3 dimensions of space + the 1 dimension of time = 4 mathematical dimensions. More dimensions can be added, for example temperature. We then have 5 dimensions which can be described in a 5-dimensional mathematical "space". But temperature is also "in space"; adding more mathematical dimensions doesn't change the fact that physical space has three dimensions - that's why they are called "the spatial dimensions". The understanding that physical bodies are three dimensional doesn't imply a claim that bodies exist without time, temperature and other properties or influences. However that understanding does imply that time and temperature are not "hidden" fourth and fifth spatial dimensions of bodies, such that we would have 4D (or 5D) physical entities; length is physically distinct from time. Then, concerning your first statement that 'even for an hypothetical 1D Space to "exist", you need time': it depends on how you understand "time". If time is a measure of the progress of physical processes, conceptually you don't need time for objects to exist. There is even a word for that concept: "timeless" (also the figurative expression "frozen in time". In contrast, if we would strip a spatial dimension from an object then it's not an object anymore. Concerning the second part, studiot's remark is pertinent IMHO: there is a strong dissimilarity with spatial dimensions due to the famous minus sign, on which you have a topic yourself. And how does distance act as an obstacle? Moreover with general relativity the universal constancy of the speed of light was abandoned; it has become a local constant instead. See also https://en.wikipedia.org/wiki/Shapiro_delay Mordred wrote (numbers added by me): 1. It's totally unclear to me what you are trying to say there.. However, the starting point isn't correct: Presentism certainly does not regard the "now" as more "real" than other times; at least, there is no reason for it, and a 3D Absolute Space concept isn't related to such ideas. 2. Time is of course not an illusion. "time" and "length" are human concepts related to observations of nature; if those observations were just illusions, we could not do physics. 3. Time is conceptually separable from space, in contrast to length (see my reply to michel here above). The concept "spacetime" is a hybrid of two distinct concepts. That's the whole point. A concept that was held by most physicists until some time after Minkowski, cannot be disproved by the fact that some people have problems understanding it. PS. Note also that "physical" in metaphysics includes things we may infer from observations. Now that this discussion is "sinking in", I'm flabbergasted. The argumentation here appears to be to the effect that a pen cannot be a three dimensional object! Did I hear that correctly??

A link to your calculation could be useful, thanks. [edit:] However, I don't know about this particular case in the relativity forums. And just as Einstein replaced calculation by physical reasoning when feasible, here that is also preferred. Further, what is again lacking, is 2e: to understand the physical motivation for the same from the viewpoint of the Block universe philosophy.

OOPS - I found an unspotted error in my example, due to the fact that this scenario is subtly different from others that I discussed in the past - sorry for that. It doesn't matter for the essence, but it's of course not acceptable to have an error in the SR description when trying to explain the causes! Bold face by Mordred: In fact I decided on that scenario in a second, but there is no need for an extremely sharp turn; it was only because I had in mind to let the car immediately retrace its original trajectory. Further, the first bold face is wrong in this ideal case. In general with acceleration, synchronization is required in order to reestablish an inertial reference system. But in this special case, there is only a change in direction; on purpose I kept the speed of the car and both clocks constant for ease of analysis (neglecting a very small error due to the asymmetry of the car). That is realizable if I'm not mistaken. By presenting a smoothly turning car at constant speed instead of a train that reverses direction, the result is totally different, for the front clock remains in front and the speed remains the same as well. Following similar physical reasoning as Einstein in 1905 with his single clock that moves in a circle, a mere change in direction (circular turnaround) will not result in "loss of synchronization". This discussion turns out to be useful for me, as I had not carefully analyzed this particular case before (or in a way I had, but it looked differently: on a rotating disc). Thus the corrected 1e becomes: We now turn it into a "twin paradox" scenario. Let's just take a sharp turn (ignoring the strong acceleration effects) and drive back without changing speed. 1e. The car is just as much length contracted as before the turnaround. In this special case, the car and both clocks kept on moving at the same speed, with the front clock in front, and the rear clock at the back, even during the turnaround (we'll ignore a minor error due to the asymmetry of the car). The clocks have advanced equally and the physical state of the car is the same as before. Consequently, the car driver should still measure the one way speed of light as c in both directions, without touching the clocks; no resynchronization is required in this case.

We are here comparing the offerings of two strongly disagreeing interpretations; I don't know how you could have read my invitation as "peremptorily dismiss".

Please don't forget that the main purpose of this discussing is to present the two explanations in their own right, demonstrating their particular strengths. It appears that many books and papers are available where each tries to "prove" that the one is right and the other wrong; if that were allowed to happen to this discussion, that purpose would not be attainable. We should also add the causal views on gravitational time dilation and length contraction. It will certainly be useful to compare philosophical arguments for or against each, which thanks to our demonstrations may show to be pertinent or not; but that's for a spin-off topic - if there isn't already a thread about it! Meanwhile Mordred's comments convinced me that it's not only useful but quite important to elaborate on the synchronization - as that's crystal clear for me now, I had simply forgotten how it puzzled me many years ago. I'll work out an elaboration of the initial car's clock synchronization with the "Absolute Space" interpretation (point 1b), but please be patient - my purpose in life is not to spend all my days in front of a computer screen. Maybe someone else here volunteers to do the same for the "Absolute Spacetime" interpretation (point 2b)? PS Mordred I know indeed how and why the synchronization method as we know was used by Poincare, and why Einstein agreed. Moreover, your historical claims about "ether drag fluid dynamics" and Lorentz are mistaken. But again, that's not the aim of the discussion here.

A correct understanding of synchronization is key. The one-way speed of light is determined by dividing the observed distance by the observed time interval. And I already cited how the Lorentz transformations follow from the conservation laws; please don't waste time. What is still lacking is some better demonstration of what the Absolute Spacetime can do, and maybe studiot will help. My reaction is: please be to the point; here you even did not bother to tell what your point is.

Sorry I cannot spend more than a few hours per week on such discussions. Which question or comment of you that is pertinent for the discussion did I overlook? If you think that a question about the Absolute Spacetime explanation can be helped by the phrase near the star, please go ahead.

Thanks Mordred! Coincidentally, in the new thread I clarified that "space" of space-time is 3D, and that the physical entity called Lorentz ether is 3D; therefore, I find your clarification that "the absolute ether Lorentz ether is a 4d model" confusing at best; I perceive there another mix-up between mathematics and physics. It's better to phrase it like Einstein and Langevin did, and their formulations can be used to emphasize the philosophical differences between Lorentz's and Minkowski's models of reality. Then, your statement: "the inertial frames are designed to follow Newtonian physics. Ie the classical kinematics. The Lorentz transformations preserve each IF" is not understandable to me. Newtonian physics is based on so-called Galilean frames, and so is SR. Although SR is based on the same inertial reference systems as Newtonian physics, SR does not follow Newtonian physics. However, my sentence "The inertial frames of SR are the reference systems of Newton's mechanics" is a bit ambiguous. "SR uses the same inertial reference systems as Newtonian physics" may be clearer. Regretfully we could not clarify if or how a block universe explains such facts as the observation of time as being separate of space, and the one-way direction of time. If those are not current discussion threads, I'll start a discussion on it. [edit:] and including two other remaining questions mentioned here below. Further, the equivalence between inertial and gravitational effects is already understood in Newtonian mechanics. Here the question is if block universe explains the existence of inertia the same as Lorentz ether does, or if it explains it differently, or if it simply can't explain what causes the inertial reaction force of a body when you try to change its state of motion. Sorry, I don't see how that statement as well as the later comment "Lorentz ether isn't Galilean relativity" could be interpreted so that they may correct or useful. There is even no need to introduce the jargon "Galilean relativity". According to Wikipedia, "Galilean relativity states that the laws of motion are the same in all inertial frames". - https://en.wikipedia.org/wiki/Galilean_invariance The following clarification "again were comparing Galilean relativity to SR. Absolute frame is still a 4d frame under Lorentz " is similarly wrong, a bit like stating "a pipe is still a 2D object". A "reference frame" in SR is 3D, see http://plato.stanford.edu/entries/spacetime-iframes/ If there is ambiguity about the meaning of "reference frame", it's better to avoid it in the discussion; we don't need the jargon "frame"! Yes indeed. Consequently: "the speed of light doesn't seem the same anymore in both directions." However you commented: No, you can't eat the cake and keep it. Only after he resynchronizes his clocks so that the speed of light again appears to be isotropic with respect to the car, will he next measure a speed of light c in both directions. [edit:] note that in this example the car driver does not touch his clocks before comparing them side by side with other clocks. More useful are the following clarifications: Yes indeed. However, as that additional explanation is equally helpful for both views of reality, it does not help to answer the questions about the distinctive features of block universe: why an object in a different state of motion is obliged by Spacetime to trace a different trajectory through Spacetime, and why we are fooled into perceiving this single "block of ice" as divided in entities called "length" and "time". A principle is not a cause-and-effect explanation. About how the block universe causes length contraction and time dilation effects: That is constructive, thanks! Maybe it will lead to follow up questions. About how Minkowski block universe understands the isotropy of one-way light speed and its independence to the car's motion: Surely there is no "ether drag" in Minkowski block universe?! There even is no "ether drag" in Lorentz ether. It's unclear in what way Fizeau "drag" contributes to clarifying how block interprets and explains the isotropy of one-way light speed and its independence to the car's motion. During the discussion it was shown to be a point that requires clarification. I managed to do that for Lorentz ether, but not for block universe.

I did not exactly quote Newton but explained what he meant with N1L; your question suggested to me that you were not aware of it. My statements about inertia were meant to create more familiarity with the territory, for better understanding. And I simply replied to your comment to me, I had not yet seen your later insight! I think that your question is pertinent and that most textbooks brush over it without sufficient attention. IMO, Newton's bucket belongs in chapter 1 of mechanics text books - but I did not hear about it until after my studies.

Here we should go step by step, for I see many issues! Here we face a first and main issue: according to Lorentz (and even Einstein in 1916), space is 3D but our time is not absolute. 3D Space as elaborated in the parallel thread means a physical entity consisting of the three spatial dimensions. 3D space is not merged with time - in contrast with Minkowski's philosophy which Einstein chose to ignore in his 1916 writing. As the concept of 3D space explicitly does not depend on the concept of time (non-withstanding mathematical correlations), the only thing that one can conclude from that label without further precision is that time is of a different physical nature than spatial dimensions. As Celeritas put our attention to that possible misunderstanding in the other thread, I therefore labeled Lorentz's philosophy "relativistic presentism". More tomorrow; perhaps this already suffices. However: Do you think that your argument in post #1 proves that relativistic presentism is incompatible with relativity?

No, you pretend that there is a link to information theory. I told you about Newton's explanation which apparently went over your head, and added the (incomplete) electromagnetic insight that mass -and thus also inertia- relates to field energies, which you also didn't register. Do you know about experiments that demonstrate that space cannot be just nothingness, such as Newton's bucket? How do you explain it, what is acting on the water? (Or, figuratively speaking: what is it that the water "feels", or where does the water "get the information from")?

Nope - we are in nearly the same position (but slightly better) than the ancient Greeks when they invented the atom concept. In fact they already found the answer, just not totally sure, and without details. And already somewhat better: the first law is about inertia. Thanks to people like Newton we can make sense of it, and thanks to people like Maxwell we know that self induction and inertia are related. The electron told us not only about electricity, but also about mechanics. What did you learn so far?

This is a spin-off from a parallel discussion here, in the context of different explanations of SR. The compatibility of 3D Space with SR was put in doubt (if I correctly understood it!) based on the argument that 3D space implies presentism, and presentism is incompatible with SR. I suspect that there's an error somewhere in that logical scheme. Mordred wrote: I could not follow that argument, regretfully... But before getting into details: it was next suggested that usually "presentism" implies a classical Newtonian concept of time. If that is correct, then it doesn't apply to Lorentzian 3D Space. Then, does your argument still stand, do you think? Please clarify, thanks!

For example this topic by Mordred is a candidate for such a spin-off thread: I could not follow the logical arguments that I didn't cite here, maybe I'm missing some information. If you still think that your reasoning applies (if it's a classical concept then it may not apply!), we could give that spin-off thread a title like "3D Space, relativity and presentism". [edit:] I now see that it received a +1 vote, which suggests to me that we should elaborate on it. So I will start that topic here.

Newton postulated that motion is in reality with respect to Absolute Space (your teacher may have forgotten to inform you). According to Newton the body "knows" how to move even without external action, because that entity is no hindrance as long as the body doesn't accelerate with respect to it. Alternatively, Minkowski proposed a Block Universe. You can read ongoing discussions about those concepts in the General Philosophy forum (Is Space-Time a physical entity, physical space vs physical space-time).

Thanks Mordred, it will be great if you can make the block universe look more capable than serving as little more than a necessary but mysterious background for the "odometer". Meanwhile this thread is already getting impractically long, and there is more to discuss. It's high time to generate a few spin-off topics (with mention of it here) for discussing so far unanswered questions and loose ends. Summary results for this topic can then be injected back into this thread with links to those discussions in part.

Thanks for the added comments. Regretfully nobody accepted the challenge... As already mentioned, it's high time to get back to business and see if we managed to improve the causal explanations by means of the two competing views. On hindsight, maybe I should have immediately started this topic with the car example according to both views, to avoid any possible ambiguity of what I expect from this discussion. Some of the comments are certainly useful for improving the competing explications. I'll try to include as much as possible of the constructive contributions in the following further elaborated car example (I hope I don't overlook much). Slowly we can make the explanations clearer by working on this together. For example, while the mathematical explanation equally applies to both views, I will elaborate a little more on the physical explanation of length contraction offered by the "Space" view, and make explicit mention of the apparent lack of any physical explanation for it by the Spacetime view. And as Celeritas thinks that the term "presentism" is reserved for Newton's Absolute time", I'll hereby introduce the term "relativistic presentism" to better convey the meaning. My opening sentence is somewhat inspired by a sentence from Celeritas. ------------------------------------------------------------------------------------------- Physical effects such as inertia and time dilation can be modeled as caused by an underlying ether ("Absolute Space"), but a more widespread view is that they are caused by a block universe (2Absolute Spacetime"). One might ask, what is the practical difference? Here's a comparison of how the two models in "action" pretend to create special relativistic effects. For a start, both models see themselves as causing the space-time metric: Absolute Space: Time is a measure for the progress of physical processes (relativistic presentism), therefore it plays a role that is different from our measurements of distances. Inertial frames can be set up just as in Newton's mechanics. Similarly as in the old theory, the state of motion (speed) cannot be detected although a change of motion with respect to Space can be detected, since Space literally induces an inertial effect at a change of motion. For the electron this can even be understood in a straightforward manner as self induction (QM improves on this quantitatively); this suggests that one day a unified theory may be found that explains all inertia as due to change of field energies. Other improvements to Newton's Space following from Maxwell and Lorentz are that radiation does not propagate like particles but as waves (or, since QM, like wavelets), so that its speed is determined by the Space that it propagates through; and that matter is affected by motion just the same as Heaviside's moving EM fields.The inertial frames of SR are the reference systems of Newton's mechanics. Absolute Spacetime: Time and Space form a single entity as proposed by Minkowski (leading to one form or another of eternalism). This model explains nothing about the passage of time. Inertial reference systems ("frames") can be set up just as in Newton's mechanics, similarly as in the old theory. However the state of motion (speed) is here interpreted as a trajectory of which the direction cannot be detected, implying that Spacetime must be homogeneous(?) although a change of angle (a change of motion) with respect to Spacetime can be detected. [please someone else complete this, how does Spacetime explain inertia?? How does it explain the observation of time as being separate of space, and the one-way direction of time?]. Now we are going to make use of inertial reference systems related to a fast car that is driving over the ground, and we let either Space or Spacetime act on them to create the required effects. Similar to classical mechanics, we are free to choose the landscape as pretended "rest frame" (neglecting rotation), in which case the car is "moving" (even if we are inside). But different from common practice, we assume here that the car conductor has set up an inertial reference system according to the assumption that the car is in rest and the ground is moving under it. Moreover the car happens to be driving at the crazy speed of 0.86c. Let's say that there are clocks c1 and c2 above two openings in the car, and these clocks have been "Einstein synced". Now the car driver drops two balls, presumably simultaneously, so that from his perspective : _________________________ | | | |_ | ___ c1 c2 ___| / \--- ----1m---- ---/ \ _______\___/___o__________o___\___/_________ <- v According to the car the balls were dropped simultaneously at 1 m distance, so that they also hit the moving ground at 1 m distance. According to the ground however the car is length contracted, and the balls are not dropped at the same time so that they hit the ground at different times: _____________ | | | | | | v ----> / \- -----o-/ \ ____________\_/___o_____\_/_____________________________________ ______________ | | | | | | v -----> / \- ----- -/ \ __________________o________\_/2m_____o_\_/____________________________ Distance between the corresponding events as measured with a ruler on Earth in blue. Now the differing worldviews: 1. Stationary ether (Absolute Space model): When you are driving your car, in general both your car and the landscape are in motion, resulting in what may be figuratively called different perspectives of the same reality. This is an essential point to keep in mind before reading on. Only for simplicity of explanation we'll first pretend in this introduction that the landscape is, by pure chance, in "absolute rest". 1a. The car is then Lorentz contracted caused[1] by the car's motion through space, as would be expected if fundamentally all matter consists of some kind of waves. In this example one could (in principle) measure that the car is half its proper length. 1b. The car's synchronization is in this case also messed up due to the car's motion, as can be easily understood by working out the timing errors from the light pulses as they propagate through space (we may ignore the air). Thus the car's synchronization is chosen such that it seems as if the one-way speed of light (also called "closing speed") is the same in both directions. According to the ground (here by chance the true "view"), it is obvious that the car's synchronization is wrong. 1c. As per the relativity principle these effects combine in such a way, that the car conductor measures that the ground is length contracted (he may of course choose to regard himself in motion, in which case he will measure that the ground is not length contracted but he is!). Moreover, just as was the case in Newtonian mechanics, the same relationships occur between two reference systems in uniform translational motion. In other words, both inertial reference systems provide in general a somewhat "distorted" perspective on reality. Note that these combined effects are not a "conspiracy", as the Lorentz transformations follow from the conservation laws. 1d. Moreover, in this special case the clocks of the car truly tick slower; this is physically understandable by means of the "light clock" illustration (e.g. Simple_inference_of_time_dilation ). Due to the car's (mis)synchronization of clocks (together with its length contraction), it seems from the car's perspective as if instead the ground clocks run slow. In general no reference system corresponds to Newton's "Absolute Time"; all show Lorentz's "local time". We now turn it into a "twin paradox" scenario. Let's just take a nearly infinitely sharp turn (ignoring the impossibly strong acceleration effects) and drive back without changing speed. 1e. The car is just as much length contracted as before. However, this time the car driver notices that his reference system has been messed up: the speed of light doesn't seem the same anymore in both directions. This follows directly if one considers that the true speed of light is the same as before, while the absolute effect of speed on the car's clocks is approximately the same (in this case the true clock rates can in theory be kept identical). Consequently the observational symmetry has been broken, and the absolute effects resulting from speed relative to the ether can thus be detected. 1f. If the car now passes clocks on the ground that it passed earlier in the other direction, the driver will notice that his clocks are behind on the ground clocks. That is as expected, since his clocks (in this simplified case) truly ticked slower all the time. As the Lorentz transformations form a group similar to the Galilean transformations, the exact same phenomena are observed between a car in motion relative to a ground that itself is also in motion. While this point may be less intuitive due to our limited mental capability to conceive such complexity of different relative motions and effects, it is not too difficult to verify this fact mathematically. 2. Block universe (Absolute Spacetime model): When you are driving your car, you are selecting (or experiencing) a slice out of Spacetime; motion is a perception caused by your Spacetime trajectory. Regretfully, no physical explanation is available why an object in a different state of motion is obliged by Spacetime to trace a different trajectory through Spacetime, and why we are fooled into perceiving this single "block of ice" as divided in entities called "length" and "time". 2a. The car appears Lorentz contracted to half its length from the perspective of the ground frame due to the car's trajectory through Spacetime which is at a different spacetime angle than the ground trajectory. The physical explication as to why this is the case is that "time" is an unexplained illusion from our senses. Everything is just trajectories through Spacetime that we can "slice" in different ways. No other explanation is given than that the physical source of length contraction and time dilation is in the geometry of space-time. 2b. The car uses the standard synchronization convention, such that the spacetime trajectory of light relative to the car appears to be symmetric in both directions. Also here one is free to choose the "angle", that is, the apparent one-way speed of light (also called "closing speed") relative to the car, depending on the choice of reference system. Unclear is how the isotropy of one-way light speed and its independence to the car's motion is understood [someone please clarify; without that it's insufficient!] 2c. The relativity principle is automatically built into this model. Here the relativistic effects are due to the different trajectories, affecting the recorded amount of "space" and "time" as if an odometer is tracing Spacetime. 2d. While the clocks in the car in reality don't tick at all, the perceived tick rate is just as truly the normal rate as those of that of clocks on the ground. Time dilation is again a matter of perspective, due to the different trajectories. A peculiarity is that a longer Spacetime trajectory between two points corresponds to less proper time increase. We now turn it into a "twin paradox" scenario. Let's just take a nearly infinitely sharp turn (ignoring the impossibly strong acceleration effects) and drive back without changing speed. 2e. From the grounds perspective, the car is just as much length contracted as before because its trajectory has changed but the relative space-time angle is the same. However, this time the car driver notices that his reference system has been messed up: the speed of light doesn't seem the same anymore in both directions. This is because the car has made a turn in Spacetime, changing its trajectory through it. That is an absolute effect; the clocks were synchronized in relation with a different trajectory. 2f. If the car now passes clocks on the ground that it passed earlier in the other direction, the driver will notice that his clocks are behind on the ground clocks. That is as expected, since the Spacetime trajectory is longer between the same events (a curved line compared with a straight line). ------------------------------------------------------------------------- Important philosophical consequences of the "Absolute Space" view of reality are that time and distance have not been totally robbed from their classical, intuitive aspects; however, physical length in the direction of motion and time rate are affected by motion through Space. In other words, only Space is causal in that view. Important philosophical consequences of the "Absolute Spacetime" view of reality are that time and distance have been totally robbed from their classical, intuitive aspects: space and time form a single physical entity (studiot's book reference: "like a giant block of ice"), in which at least all events in the past and present (and commonly also the future) "coexist and are frozen in their locations in space and time". In the Spacetime view, Space and Time are coexisting causal physical entities, or even different aspects of a single causal physical entity. [The "Evolving Block Universe" variant doesn't have the coexisting future problem but it has the strange property of "double time", how to explain that?]. Once more, corrections of errors are welcome. We should still give examples of interpretations of basic GR effects. [1] Elaboration: what follows is from memory, in order to provide more context in view of comments by Celeritas and bvr as well as Mordred; it's slightly simplified and there may be a few inaccuracies but the gist of it is certainly correct (suggestions for improvement welcome of course; however I want to keep it compact!). The discoveries related to Maxwell's theory and the electron (a moving electron's energy and mass roughly correspond to its electromagnetic field energies) gave way to the hope that all matter may be shown to be entirely electromagnetic. It was also realised that atoms are bonded by electromagnetic bonds. At about the same time that observations forced the length contraction hypothesis on theory as the only reasonable solution to the puzzle, Heaviside calculated that electromagnetic fields should contract by the gamma factor when in motion (we now know that atoms must contract the same: details can be found in Bell's "How to teach special relativity"). Newton's assumption according to which matter is not affected by motion had already become implausible. The independent proposals by Fitzgerald and Lorentz that length contraction by the gamma factor must take place as the result of motion was, in the end, the only solution, imposed by both theory and experiment. Soon after, it was found independently by Larmor and Lorentz, that motion similarly must slow down natural processes by the same factor (Bell also elaborated on this aspect in detail).

Concerning SR, it means that you are almost there! If your math skills are not too poor, you can understand a derivation of the Lorentz transformations with your "19th century" knowledge. However, that would be typically something to elaborate in the physics or relativity forums; thus I guess that a derivation is not what you are after.

OK, both hypotheses (a historical Jesus and a non-historical Jesus) are mentioned for discussion in the OP - thanks for the correction. I should have written "highlighted" instead of "chose". Although the OP puts the second hypothesis in the lime light ("Here is what I find to be a compelling explanation for why a historical Jesus most likely did not exist"), both hypotheses were to be discussed - as was done. That doesn't change my assessment of the likely causes of the negative votes on that post: they may have deemed it one-sided or unfair, and it's not hard to find why. But maybe one of them will clarify later.

I see that some people pressed the "negative reputation" button under that reasoning; I think that it's more useful to briefly comment on the probable cause, which is the one-sided view of that post which doesn't fairly reflect the discussion. The OP video clarified that we are facing two hypotheses: that of a man who was a bit like most other people of that time, to which the god concept was added; and that of a god who like most other gods of that time had a human aspect, with a historical narrative added to it. The hypothesis that the OP chose for discussion here is the second one; a "null-hypothesis" approach would consist of trying to disprove that hypothesis. And of course, there are variants of each hypothesis. As there is in the eyes of adherents of each hypothesis and variants of them credible or even strong evidence for their hypothesis without pertinent counter evidence, no consensus can be reached.