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You said, " in fact light always travels as a probability wave and is absorbed as a quantum/particle." but this is just a very wild guess about how light works. Actually as its based on the idea of Quantum mechanics, its obviously nonsense. But regardless, the illustration of the moving light clock is also totally wrong and BS, and everything about Einstein's theories are just nonsense too.

silverrahul wait, how long ago was 3 week? I already figured out this problem. The reason is because for one twin to move in the first place, he had to accelerate which causes time dilation cuz of special relativity and stuff. Doesn’t an object in motion feel more drag than a stationary object. I imagine if there was a quantum mechanical explanation, it would have something to do with drag and slowing the motions of all particles in a person’s body, forcing them to physically age slower as their DNA would have trouble replicating, causing DNA replication and therefore aging of the person to slow down.

silverrahul No, I mean theoretically it could work like that. I mean technically speaking, we haven’t actually proven that a dimension of time even exists nor have we proven that time exists. Hell, it could just be an emergent property of our universe.

As a non animator, I can see that too

You haven't understood it. That is the whole point. Because the light must travel further and always does so at a constant speed it will bounce less often, in other words time ticks slower.

If the vertical position is plotted horizontally then what's plotted vertically?

Also, isnt the speed of light, the speed of light, no matter what? Even if travelling in a light clock moving at the speed of light?

GPS satellites have faster running clocks because orbiting the earth makes their clocks run slower

@@adawg3032 Is that to keep them in sync with Real Time or, with global time-zones?

Gents, a common misconception is that the proper lenght/trajectory is diagonal! That's false and relativity has nothing to do with this. Diagonal is the trajectory as seen by one other observer, the viceversa holds true either; the "statuionary" observer, stationary with respect to its frame, sees the beam UP and DOWN, so BOTH see light travel UP and DOWN. The same concept applies to length contraction. You CANNOT compare time pace and space extension as seen in differing frames and states that they are different. To do that, you have to "transport" quantities from one frame to the other. Actual the length of the light clock is the same, this is the proper length, a concept that relates to proper time. Bottom line is that both perceives the clock of the moving frame as ticking at a lower pace. But at the end of the day only the moving clock slows down! Moving with respect to what? what is the "absolute" reference to say a clock is moving faster than one other? It's the light cone, the array of the light cones as they materialized throughout the while space-time. I striogly recommeng this reading: “Close to the Speed of Light”: Dispersing Various Twin Paradox Related Confusions" by M. Arsenijevic, where the meaning of the misleading word "relativity" is physically addressed: the word relativity is actually a pitfall and nowadays used and abused like it was for the word incompleteness of the incompleteness theorem of the mathematics. Contrary to popular belief an absolute entity still exists even in relativity ... read and discover the clue to any apparent paradox.

To the observer - that is, the person OBSERVING the moving clock - the passage of light DOES indeed look angled - and longer than if viewed in the reference frame of the clock. Hence the rest follows. Look up Feynmans Clock for clarifications.

Thanks. All animations were made with Blender.

If you take "conservation of distance" as a fundamental axiom, then indeed you will never retrieve length contraction or the Lorentz transformations, for that matter. But the generally agreed on fundamental physical laws from which coordinate transformations are derived actually do not include "conservation of distance" or "conservation of length". They are instead: 1) isotropy and homogeneity of space (the properties of empty 3D space, devoid of matter, are the same at every location, in every direction, and at any moment in time), and 2) the principle of relativity (the laws of motion - and of physics in general - are the same in every inertial reference frame). Now, if you apply strictly these assumptions, nothing else, and attempt to find all coordinate transformations compatible with them, you eventually find out that there are two distinct possibilities: the Galilei transformations, which do "conserve 3D lengths", and something like the Lorentz transformations with one single parameter that plays the role of an unspecified "speed limit", which bring about length contraction. This is strictly logic and math from very basic assumptions, no space-time necessary, not even a speed-of-light assumption, just event coordinates in space and time as we all know them. It is known as "relativity without light" and there are some very nice papers about it out there (can't find a non-paywalled link to the original one right now, but see arxiv.org/pdf/0710.3398.pdf and philsci-archive.pitt.edu/13220/1/rwl%202017.pdf for instance). The bottom line is that the fundamental principles give us 2 logical options, Galilei or Lorentz-like, and nature shows us which one applies in reality: it turns out it is not the Galilean one, and so 3D length is not "conserved".

Your comment is equally misleading. Apparently you do not know what Translation Symmetry is. It is part of physics. Every theory has to be compatible with Translation Symmetry. Special Relativity is not. compatible with it. How much do you know about physics?

​@@ericsu4667 You simply proved that proper length remains the same, that is obvious and beyond discussion. You missed the point that contraction of length refers to one other view of the same body, the body and the intrinsic physical dimension remain the same, its the view that changes because it's the observer that changes. And it's not an illusion, because what you measure it's reality, for you in your reference frame as for anyone else in his reference frame. This is a common misconception, that body changes arbitrarily depending on the reference frame: relativity is NOT about that!

@@giorgiovercelli8974 Read your own statment carefully. "You simply proved that proper length remains the same". It remains the same in every reference frame. It is identical in every frame for every observer regardless of the observer's motion. You and measure the same length of the objecti. There is no contraction.

Yes, unlike Galilei transformations it doesn’t conserve distances in 3D space. But it does conserve distances (spacetime intervals) in space-time. The problem is that while we have the right equipment to _see_ distances in the 3 space dimensions, we need a workout under a “thinking hat” before we get a sense of what “distance in spacetime” might be.

spacetime is a proposal by Minkowski who is a mathematician. Math people focus on consistency but not reality, nor physics. If indeed spacetime is conserved then time has to be absolute because space is conserved. vixra.org/abs/1709.0120

Thanks and sorry for the late reply. No, the calculation doesn’t assume that the light beam inherits velocity from the mirror. It assumes that the beam moves at the same velocity in any direction, whatever the velocity of the mirror on which it reflects. The reason you find the sideways propagation disconcerting is probably because you think of the light beam as a particle beam: if a particle moves sideways after colliding with a surface, it must have acquired a velocity component from that surface. But light is not quite “particles”, even in terms of photons, and in this case it may be helpful to picture it instead in terms of wavefronts. What happens is that wavefronts that are parallel to the mirrors in one frame (say, the moving clock frame) appear tilted when observed from the other (stationary) frame, and conversely. That is, where the clock frame observes wavefronts parallel to its mirrors, the other frame observes tilted wavefronts propagating at an angle relative to the motion of the clock and therefore reflecting off the clock mirrors at an angle. The tilting of the wavefronts is a fundamental phenomenon and unfortunately it’s not emphasized enough. It is the simplest way to understand why the Maxwell equations governing light propagation are invariant under the relativistic Lorentz transformations, but not under the Galilei ones. If you are interested, there is a segment in my video on “Lorentz transformations” that visualizes the tilted wavefronts, although in a different context. It starts around the 2:45 mark.

Thanks for the reply, however, as I do understand what you mean, I think it is still false. You should try to imagine when your clock starts to move from standing still to moving sideways. The light will not follow the mirrors. Not saying that time dilation does not exist, just saying the light clock is a bad example and will not function in the real world, only as thought experiment (think Einstein said the same).

Late reply again. But, try the converse: leave the clock untouched in an inertial frame and imagine yourself accelerating away from it sideways. Clock still functions as it should, throughout your acceleration period until you reach final velocity and settle in a new inertial frame. it is obviously your perception of it that changes.

I understand it, just saying physically a lightclock is not possible, as imagined in yours and other people animations. The light will reflect at the same angle as it hit the surface, and when you start at a 90 degree angle, you can move the mirrors, but it still will reflect at a 90 degree angle, and missing the upper mirror. When the clock is not moving, but it is me that is moving, then indeed it seems that the light is moving at an angle, however, this also means that it will appear that it is travelling a longer way in the same time, so it would be quicker than the speed of the light, but that is only perception. The lightclock is just a bad example, which will leave many people with questions.

"physically a lightclock is not possible": No, it's perfectly possible, nothing physically wrong with the concept. “The light will reflect at the same angle as it hit the surface, and when you start at a 90 degree angle, you can move the mirrors, but it still will reflect at a 90 degree angle, and missing the upper mirror”: This is only true in the clock’s own rest frame. From another moving frame things are different, the reflection laws must take into account the orientation of the reflecting surface relative to the direction of motion. But for a surface parallel to the direction of motion they remain the same as in the rest frame. So you can safely apply them to a clock perpendicular to the direction of motion. “When the clock is not moving, but it is me that is moving, then indeed it seems that the light is moving at an angle, however, this also means that it will appear that it is traveling a longer way in the same time, so it would be quicker than the speed of the light, but that is only perception.”: No, the light beam travels at an angle, and a longer distance than just the length of the clock, but it always travels at the speed of light, that’s the whole crux of the matter. It’s also the thing that rattles our regular intuition. The beam "should" go at a different speed than the speed of light, but it doesn't.

Yes, objects appear brighter the faster you move towards them. It's called the relativistic headlight effect. But it's more complicated then just photons hitting the eye at a faster rate. The angular spread of light rays gets ever more squeezed in a cone around the direction of motion as velocity increases, and gets compounded with time-dilation, plus there is Doppler blue shift.

Just for consistency, if anybody else is interested in this: I answered a similar question at my other video here: ruclips.net/video/-eqBE1ksAEs/видео.html. The gist of it is that "a different timeframe" does not mean "a different space-time". To the contrary, any event, occurring at a given point in space and time, is unique, in the sense that if it occurs for one observer, it occurs for any other observer. What changes from one observer to another are the event coordinates, and with those the observed sequencing of events. So if inertial observer A sends a signal to inertial observer B and documents that the signal did reach the position of B at some point in time, then B definitely observes that the same signal did reach him at some moment of his own time. So communication between inertial observers is never an issue, despite time dilation. For non-inertial observers, including uniformly accelerated observers, things may be complicated by the occurrence of event horizons. For instance, there exists a region of space-time to which an accelerated observer cannot send signals, and another region that cannot send signals to him.

This is incorrect. Time slows down, but also does distance become shorter. You being a stationary observer, would have time faster only for "your" particles, nothing slows down around you; a common misconception. It is an intrinsic property to your body only. Same goes for the traveler near light speed, only does his/her/it's matter contract due to the c because at c you become infinitely contracted to 0. This distance shortcut is proportional to the time frames that you skipped as a result of being in a vector velocity near c. So it basically invalidates your immortality proposal.

What you miss is Lorentz Transformation. Length contraction comes from Lorentz Transformation which is impossible in physics. vixra.org/abs/1709.0120

Long story. Let's take it one step at a time. "Would it then be unreasonable to assert that the observer who ages more slowly must be traveling into the future of the other observer?" Well, I would put it a bit differently. Take one moment of the "stationary" observer's time and have him examine clocks co-moving with the moving observer and spread across space. His own clocks, wherever they are, are all synchronized and show the same time. But the moving clocks show different times, depending on their position along the direction of motion: those further back are more advanced then those further ahead. So yes, you can say that at any moment of his time the stationary observer sees across the time of the moving one, from way back in the past to way ahead in the future. Otoh when he follows any of the moving clocks as they travel along, he sees each one of them running slow, all at the same rate, but with different offsets depending on their position relative to the stationary frame. And the same holds for the point of view of the moving observer looking at the stationary one. "Does this not mean then that the two observers cannot agree on each others " instant " of time " being the " same instant " of time...... or is that clocks just disagree?" They do not agree on which events are simultaneous and which are not *when those events happen at distinct locations*. But they do agree on events that happen simultaneously *at the same location*: they always sees such events occurring at the same time and in one place. "By this conjecture then are we not forced to deduce that each observer is living in either in the past or future of the other?" In a way. But each sees the other coming from the past and going to the future, never the other way around. "If this was the case then how could they communicate?" Good question. It all comes down to how time works in conjunction with relativity of simultaneity. Say a recording station in the stationary frame is passed by the moving observer, but at some later time observes an important event at its location and wants to send a warning to the moving observer. The best it can do is send the message at light speed. Now, when the event occurs, the stationary frame observes that the event time on a moving clock over there is in the *future* of the time on a moving clock at the location of the moving observer. But, by the time the light signal catches up to the latter, the event time will already be in the local past of the moving observer. In other words, although running slow, time at the moving observer's location always passes faster than the time needed for the light signal to reach him. So no communication from the future to the past is ever possible in special relativity. "I am unaware of any mechanism which would allow me to contact directly, at this instant, with anyone in my past or future, whether it was a year into my past or present or even a nanosecond." As far as we know right now, there isn't any that works in reality.

Uncertainty Drive . Most grateful for your lengthy reply and explanation. It is refreshing not to be dismissed out of hand as a crank or be the recipient of some form of personal abuse. I will have to read you explanation more than once to take it all in. But if I may, let me put a similar conjecture to you. Using the usual example of the astronaut who travels at near light speed and is away for say ten years as perceived by those left behind on Earth. If the astronaut returns to find everyone on Earth is now ten years older than himself, then surely and by definition he must deduce that has been travelling through" time "with respect to those on Earth, and vice versa for the stationary observers on Earth. If either observer cannot agree on a common " present " whilst one has been in motion relative to the other then surely they couldn't have been in the same timeframe during this relative motion and therefore communication would not have been possible. Since the time dilation equation is valid for all T then any arbitrary velocity of one observer with respect to the other would forbid communication. I am a mathematics hobbyist at the moment although I studied for a year at university. Einstein's equations are really something else. My current understanding of differential geometry is insufficient for me to reach a full comprehension, particularly in respect of derivation and interpretation of the Christoffel symbols, but I'm working on it. Anyway thanks again for your kind reply.

Welcome. I hope things make a bit more sense. "If the astronaut returns to find everyone on Earth is now ten years older than himself, then surely and by definition he must deduce that has been travelling through" time "with respect to those on Earth, and vice versa for the stationary observers on Earth." Again, in a way. In any case, the difference between the times experienced by the two parties has to do not only with time dilation while moving uniformly, but also with that experienced during the acceleration and deceleration legs. Ignoring the latter two is not a good idea, because it leads to contradictions in certain details. You may want to take a look at the explanations in physics.stackexchange.com/questions/242043/what-is-the-proper-way-to-explain-the-twin-paradox. The 3rd answer down explains the pitfalls of the twin paradox "without acceleration". And Einstein's own take on the paradox is another interesting read, see en.wikisource.org/wiki/Translation:Dialog_about_Objections_against_the_Theory_of_Relativity. "If either observer cannot agree on a common " present " whilst one has been in motion relative to the other then surely they couldn't have been in the same timeframe during this relative motion and therefore communication would not have been possible." For *uniform motion* do not imagine the different "timeframes" as distinct separate entities that cannot communicate. They are just different viewpoints across the same space-time and communication is perfectly possible. For *accelerated motion* things are more complicated. The accelerated guy may indeed observe an event horizon beyond which he cannot communicate. In fact he may even outrun a light ray, see 4th answer down in the link I mentioned. As for the Christoffel symbols, they make a lot more sense if you start with curvilinear coordinates in 3D space, where you can really visualize things. see en.wikipedia.org/wiki/Curvilinear_coordinates.

"the imaginary light clock only can fit Einstein’s theory when it moves in a direction perpendicular to the light clock." Not really. The light clock fits the theory of relativity regardless of its orientation relative to the direction of motion. The reason we use it in only two preferred orientations is to keep things simple and avoid having to explain relativistic shape distortions and modified reflection laws. "if the light clock moves (with respect to the observer) in the same direction followed by the photon between the clock mirrors (for example, if both are moving in a vertical direction), the intervals measured between the tics of the clock would be very different" Correct. As seen by the stationary observer, the intervals displayed by the moving clock are very different. But have you watched this entire video? Because the 3rd part is an extensive segment precisely on a light clock aligned along the direction of motion. It starts at around 5:30. "Therefore, the light clock would show time dilation (between the first tic and the second tic) and time contraction (between the second tic and the third tic)." No. You arrive at this conclusion because you don't account properly for relativity of simultaneity, or better say, how the proper time of the moving frame is observed in the stationary frame. This is usually explained with a bunch of math. But since you are probably annoyed by the intuitive schism, you may want to take a look at my videos on the Length Contraction Paradox, and especially on Lorentz transformations. The latter has a segment on plane lightfronts used to visualize planes of simultaneity, starting at about 2:45. Basically, a plane lightfront that synchronizes clocks along the direction of motion in one frame (and so parallel to that direction) is observed as tilted from the other frame. So the light pulse of a clock aligned along the direction of motion "chases after" its rest frame's planes of simultaneity when going in one direction, and runs against them in the opposite direction. But it always "bounces" between planes of simultaneity corresponding to equal intervals of time in the moving frame. And those intervals of time are always time dilated. "In conclusion, the interval of time measured between an even number of tics cannot be equal to the dilated time predicted by Einstein’s formula, and thus a light clock that moves in the same (vertical) direction which is followed by the photon does not fit the Relativity Theory" See above. Again, the intervals of proper time measured by a light clock are always equal and time dilated. Light clocks are just one way to visualize this, but the essence of time dilation and all that transcends them. It's about the nature of space-time itself. Literally.

The basic formula to calculate relativistic time dilation is the following one: the dilated interval of time (T) is equal to the interval of time (t) multiplied by the gamma factor. T and t are the intervals of time (measured by two different observers) between two tics of the light clock, that is, between two "bounces" of the photon. If the light clock moves in a direction perpendicular to the photon, we have T = t x gamma, 2T = 2t x gamma, 3T = 3t x gamma, 4T = 4t x gamma, 5T = 5t x gamma … The relativistic formula is always correct and (strangely enough) you have not considered the so-called "relativity of simultaneity" for this special case … However, if the light clock moves (with respect to an external observer) in the same direction followed by the photon between the clock mirrors, then we have T ≠ t x gamma, 2T = 2t x gamma, 3T ≠3t x gamma, 4T = 4t x gamma, 5T ≠ 5t x gamma. The relativistic formula fails in this case, seeing that the rate of the clock is variable for the external or "stationary" observer (slow - quick - slow - quick … ), and this means time dilation - time contraction - time dilation - time contraction … In my opinion, the last part of your video simply shows that something goes wrong in this case.It is absurd to argue that relativity of simultaneity solves the problem, because this hypothetic effect should be applied for every case. You cannot apply relativity of simultaneity in the measurement of some intervals (T, 3T, 5T …) and discard it in the measurement of other intervals (2T, 4T, 6T …). And you cannot avoid its application (for every interval of time) when the light clock moves in the direction that fits Special Relativity, that is, when the light clock moves in a direction perpendicular to the photon. This is not a consistent scientific method.

The physicist who created the first cesium atomic-clock, named Louis Essen, was a reputed expert in time measurement and in the measurement of light-speed. He lived until 1997 but he never believed in the relativity of time. He criticized the Special Relativity theory in several articles, and he also criticized the experiments made with atomic clocks in an attempt to prove it (i. e. the Hafele-Keating experiment). See www.ekkehard-friebe.de/Essen-L.htm

I see what you mean. And thank you for Lois Essen's story, I was not aware of it and it is so interesting. But the answer is still negative. "The basic formula to calculate relativistic time dilation is the following one: the dilated interval of time (T) is equal to the interval of time (t) multiplied by the gamma factor." If t is the clock's period in it's own rest frame and T is the period observed in the stationary frame, then yes, correct. With one very important observation: Time dilation only concerns durations t measured at *one single location along the direction of motion* in the clock's frame and the corresponding duration as observed (at two different locations) in another frame. It does NOT apply to durations between events taking place *at different coordinates* along the direction of motion in the clock's frame. And conversely. This is why the vertical clock is so simple: If the clock frame moves in the x direction, all its tics take place at the same coordinate x, albeit at different locations along its length. But if the clock lies along the x-axis, only durations between "round trip" tics at the same end, or any other location, will display time dilation. So, "If the light clock moves in a direction perpendicular to the photon, we have T = t x gamma, 2T = 2t x gamma, 3T = 3t x gamma, 4T = 4t x gamma, 5T = 5t x gamma … " Correct, as explained above. " However, if the light clock moves (with respect to an external observer) in the same direction followed by the photon between the clock mirrors, then we have T ≠ t x gamma, 2T = 2t x gamma, 3T ≠3t x gamma, 4T = 4t x gamma, 5T ≠ 5t x gamma." Partly correct, but the conclusion is wrong. If the sequence of events in the clock frame is (0,0), (ct, t), (0, 2t), (ct, 3t), etc., the corresponding sequence in the other frame is (0,0), ( gamma(1+beta)ct, gamma(1+beta)t ), (2 gamma beta ct, 2 gamma t), ( gamma(1+ 3 beta) ct, gamma (3 + beta) t ), etc. So the stationary frame observes the moving clock to beat time at 0, T, 2 gamma t, T + 2 gamma t, 4 gamma t, etc. In other words, the interval between successive beats *at the same end of the clock* is always 2 gamma t, and this is exactly what time dilation is about. The fact that T is different from (gamma t) does NOT invalidate time dilation, because it is a duration between events taking place at different locations along the x-axis. "In my opinion, the last part of your video simply shows that something goes wrong in this case." No. Nothing goes wrong. Just counter to everyday intuition. "It is absurd to argue that relativity of simultaneity solves the problem, because this hypothetic effect should be applied for every case." I beg to differ on the absurd bit. It always applies in the same way, that's the beauty of it. "You cannot apply relativity of simultaneity in the measurement of some intervals (T, 3T, 5T …) and discard it in the measurement of other intervals (2T, 4T, 6T …). And you cannot avoid its application (for every interval of time) when the light clock moves in the direction that fits Special Relativity, that is, when the light clock moves in a direction perpendicular to the photon." I didn't discard anything at any point. And I certainly did not *apply* relativity of simultaneity to any measurements or events. I simply showed how it *follows* from the speed of light postulate using the clock-along-the-direction-of-motion setup. It just doesn't work the way you assume. Likewise, it wasn't discarded for the vertical clock. It is still there very much, but it simply isn't necessary to invoke it - because 3D geometry still functions the good old way (and is so much easier to understand). As for Lois Essen, we can't deny that strange things happen even to the best of us. I see an intriguing parallel to Einstein himself, who was always at odds with quantum mechanics, although he had a serious hand in its beginnings. Essen never came to terms with relativity, but he gave us the currently accepted value of the speed-of-light, on which all measurements of relativistic effects rely.

Thank you for your long answer, but I still think that you play a "wild card" only when it is convenient for your arguments. This speculative theory is so elastic that it can be accommodated to nearly any fact. For example: You say that the constancy of light-speed in vacuo rely on "all measurements of relativistic effects", but when I discussed the gravitational effect of time dilation (with a theoretical physicist) he told me that, according to General Relativity, the speed of light is only measured as the constant c by a local observer, and not by the distant observers. Therefore, the Second Postulate of Special Relativity was modified by General Relativity, the second part of the same theory, only ten years later ... Maybe you are not aware of other important historical events. The true creator of Special Relativity (and some concepts of General Relativity) was the French Mathematician Jules-Henri Poincaré, basing on the previous studies by Larmor, FitzGerald and Lorentz. In fact, the original contribution of Albert Einstein (to the Special Relativity theory) was very small. See www.brera.unimi.it/sisfa/atti/1998/Giannetto.pdf

On "why the stationary observer and the moving observer will see each others clock pulsing slower": This *is* factual after all, we do have experimental evidence that relatively moving observers do see each other's clocks running slower. The ultimate reason is the speed of light limit, since without it there would be no time dilation, length contraction, or relativity of simultaneity. But the trick to understanding the big picture of it all is to go beyond one single moving clock after we understand that it must run slower. Imagine instead a whole array of equally spaced clocks, all moving at the same velocity relative to you. Not only do they all run slower than your own clock, by the same factor, but they show *different times* (have different offsets) depending on where in the array they are. So what you observe as the state of the moving array at one of your moments in time, is in fact a "space-time cross-section" across the array's own time. That is, different locations in space show us different moments of the array's history. Likewise, an observer traveling with the array sees a "space-time cross-section" of your own frame's history. If you'd like, it is "as if" different observers "look sideways" across space-time, along "different directions". Unfortunately the scale on which we'd have to operate to actually "see" this effect for ourselves is astronomical, and barely in our technological reach right now. We are getting there, but in the meantime we still lack experiential exposure on which to form a working intuition about basic relativistic phenomena. You may want to watch my videos on length contraction, especially the 2nd part of the one on the length contraction paradox, for more details on this point of view.

On "the idea that what is actually observed is not a real time event occurrence but rather is a time delayed view, a ghost view of a past event?" Not quite. Slower rate does not mean "always stuck behind in the past". In fact, for the clock array mentioned before, a snapshot across all of space at one moment of your time captures array clocks showing both past times *and* future times. Yes, you could record the future of the array relative to your time. But being limited to transmitting that info at other points in space at most at light velocity makes the whole thing useless for cheating time: you can never communicate the future to other points in the array ahead of "array time".

To " UncertaintyDrive". I thank you for taking the time to give such an expansive reply to my questions .It is most appreciated. I fully grasp the concepts and explanations that you offer up and I think I can accept the troublesome 'Time' factors in understanding special relativity. I don't think you explained though why both clocks would run slow relative to each other. You seem to be accepting that only one of them is considered as moving.

"why both clocks would run slow relative to each other": Because of the principle of relativity, which is always fundamental. If inertial frame A observes inertial frame B's clock running slowly then it must also hold that frame B observes frame A's clock running just as slowly. Otherwise there would be some preferred inertial frame, and the principle of relativity would not hold. "only one of them is considered as moving": same as above. Whether you mean that one frame is distinguished because it observes a moving clock run slowly, or that one frame is distinguished because it is absolutely moving or, equivalently, absolutely stationary, the answer is the same. The principle of relativity requires that physical laws are the same for all inertial frames and means that there is no such thing as an absolutely stationary frame.

If you search for explanations of the ''Twins Paradox' it will help to understand how this is possible.

Welcome. One thing though, it's not really an "illusion" in as far as it is perfectly measurable. But then you may want to look up the Terrell-Penrose effect, which shows that visually we see the "illusion" that length contraction does not exist! Doesn't get more "relative" than that, does it? :D

Thanks, I may try to put something together in the future, but don't have anything for the moment unfortunately :) In the meantime you may be interested in Cassiopeia Project videos on Quantum Mechanics, www.cassiopeiaproject.com/vid_courses3.php?Tape_Name=QM. Ch.6 deals with wave function collapse, entanglement, etc.

Thanks. Sorry about the voice, but it's much better than mine, believe me. Is it the pitch, the tempo, the intonation?

UncertaintyDrive Mostly the off monotone and pronunciation. The video really did help me understand relativity. I have a couple of questions though. What happens when two objects pass each other faster than half the speed of light (say, 60% c). Relative to each other they should go 120% c but we both know that's impossible. What keeps that from happening? My second question is similar but for this one the two objects move away from each other at 60% c from a central point. Relative to each other the opposing object should be moving away at 120% c but that is impossible. Why and what would an observer on either of the objects see in this scenario?

THUNDERTURTLE Your two questions are actually a single one, since the objects go toward each other before they meet, and away from each other after that, all the while having the same velocities relative to the observing frame. In any case, in the frame that observes both objects going at ±0.6c, their apparent separation does decrease/increase at a rate of 1.2c. Just as you'd expect, the lower/upper limit for the rate of change of their separation is ±2c. But this rate is not a proper relative velocity. That is, it is not the velocity at which one object observes the other, neither is it a velocity relative to the observing frame. The true relative velocity of the two objects is given by the relativistic velocity addition formula, which unlike the Galilean one is nonlinear, and always gives a result less than c. The correct relative velocity of the 2 objects is (0.6c + 0.6c)/[1+(0.6c x 0.6c)/c^2] ~ 0.88c. The reason for this counterintuitive composition rule is ultimately relativity of simultaneity, because what one frame observes as simultaneous positions, appear as non-simultaneous positions in another frame. Since each frame defines distances and velocities by means of simultaneous positions, this means that different frames must use completely different events to evaluate relative velocities and the simple Galilean rule no longer applies.

Thanks for the link. Will take a look.

UncertaintyDrive Cool :) I like your way of making videos. The visuals are very nice and extremely well support the clear presentation of the mathematics. I noticed someone commented about the speech synth used on one of your videos. Check out the Mac OSX speech synth voices, I use them as some of them sound quite natural. Do you use Blender for modelling btw?

Thanks a lot, I try to keep the story as intuitively logical as possible without sacrificing rigor. And yep, using Blender … with a Mac voice and all :), plus final polishing on Audacity.

UncertaintyDrive Ah, I didn't realise that's Mac voice synth. It sounded so Windows like. Try the other voices, some of them sound much better. Interestingly there are some English voices with even Indian accent :) I try to vary the voices used so the videos don't all sound the same.. Do you also use the Blender video editor for editing the clips?

Ouch, just checked the Windows 10 voice. I see what you mean, it's the pitch, but I had no idea whatsoever! My videos are 100% Mac, I think I mention it at the bottom of descriptions. Actually I put a good deal of effort into a more mature/resonant version of Alex. Was pretty happy with it. And yes, Blender everything for the clips up to raw avi, mp4 compression separate. Can't get Blender's ffmpeg to do the mp4 quite the way I want it.

The basic reason is relativity of simultaneity: for any two points on a moving object, the proper time for the foremost one in the direction of motion lags behind the proper time of the rear one. So given two events with the same proper time, the rear one shows up first. Equivalently, in a Minkovski diagram the plane of simultaneity of the moving object is at an angle to that of the observing frame. The second part of the video tries to visualize how this tilted plane of simultaneity generates the real-time view.

Hmm, K. Is there some sensible reason why the forward point's proper time would lag behind the rear's?

The ultimate reason is the speed-of-light law: what propagates at the speed of light in one inertial frame must propagate at the speed of light in any other frame. Now take the arrangement of Einstein's famous train: A device emits 2 light flashes in opposite directions from the middle of the train. From the train's p.o.v. the flashes propagate at the speed of light and reach the train's front and rear simultaneously, at the same instance of the train's proper time. From the p.o.v. of another observer watching the train pass by, the flashes still propagate at the speed of light, but the one going against the train's direction of motion meets the rear faster, while the other one has to chase the front a longer time. So for this observer the proper time at the train's rear is ahead compared to the proper time at the front. And this wouldn't happen without the speed-of-light law.

Thank you.

Chris Frisella Welcome.

+NEWKNOWLEDGE Thank you for your comment and the link. I didn't quite understand until I watched your videos, but I do now: you begin from a certain heuristic view and justify the diagram which you then use to reconstruct SR, while I retrieve basically the same diagram with its intuitive representation from within SR. Although there are some differences in the finer points, in the end we obviously have a case of, well, remarkably "uncanny relativity" :) I have to confess that my path to this representation was more or less linear, and I couldn't have thought of it your way. May I ask how you got the idea in the first place?

Well, back in grade 9 I had noticed the odd paradox concerning the outcome of moving at an infinite speed across an infinite distance. I pointed it out to the science teacher and was basically told to sit down and shut up because he thought I did not know what I was talking about. Due to health reasons, I soon was out of school (My parents took me out, thus I became a high school "take out") and thus I never had the chance to obtain any physics education. Years later I went back to analyzing "motion". I was tickled pink to find out that my outcome of my analysis was the same as Special Relativity and all of its equations. But I also discovered that no one else used geometry the way that I had, meaning the stacking on top of each other both length scalars and motion vectors. Kill two birds with one stone, so to speak. Not bad considering that all of my teachers thought of me as a hopeless case. They came to that conclusion because my primary interest was in "understanding" not "knowing", thus I absorbed little knowledge and in turn was seen as nothing but the class dimwit.

+NEWKNOWLEDGE Interesting story. I think you followed a good geometrical intuition grafted on the idea that "all objects move through space-time at the speed of light", which in the end is formally true in itself, but difficult to justify as a first principle. It works if you allow for relativity of simultaneity, but this is also difficult to take as first principle. And there is the distinction between "time in the observer's frame" and the "proper time of objects observed", and a few other things. I guess your initial intuition carried you very fast at the expense of the step-by-step argument from the more basic premises. Which ends up being unnerving from either point of view, despite the common conclusion.

+UncertaintyDrive The next step I took was understanding Quantum mechanics. It did not take that long to understand Particle/Wave duality, entangled pairs, delayed quantum choice, and action at a distance. Today's physicists are going to be very embarrassed when they too figure it out. Yes they have got the math down pat, but they still don't understand it. Here is a clue. An apple has both an inside and an outside. Well so does reality. The laws of physics on the outside are different than those on the inside. So whenever an event is governed from the outside, it has the physicists somewhat mystified since they do not yet include the second set of laws of physics as an intentional second separate set. Good luck with G.U.T. if they continue try to squeeze all reasoning into the inside only.

+NEWKNOWLEDGE What you say sounds very much like a "hidden variables" version. There have been several such attempts, and the general problem with them is that according to recent tests of Bell's inequalities QM statistics is not very compatible with hidden variables. The precision and accuracy of such tests is rather impressive already and constantly improving. In any case, a discussion along these lines needs another setting.

+Walid Nouh Thank you, much appreciated!

+Behfar Bastani Glad you like it, thank you!

+Eric Drucker Welcome and thank you!

However, length contraction is impossible in physics. It is only mathematics. Problem is in Lorentz Transformation. vixra.org/abs/1709.0120