The REAL Reason You Don't Understand Relativity 

One random day, when I was in my early 60s, I watched an MIT lecture on RU-vid where the prof explained the Lorentz Transformations and it was a “eureka” moment for me. The math made perfect sense. All the implications of Special Relativity made perfect sense. The lesson for me was realizing ( to paraphrase H.L. Mencken ) simple answers to complex problems are always wrong.

I would be curious to know what the professional background of this channel's creator is. The limited content of his that I've seen consists entirely of "everyone else is wrong and/or stupid, and only I know this stuff". This is very off-putting. It's fine to be contrarian, but it would be nice to know there's some authority behind it rather than it coming from some rando on the internet.

You seem to be (wilfully?) missing an obvious point that Sabine made very clear - she was saying that what people generally mean when talking of 'time dilation' is actually a misunderstanding of the role of co-ordinate time (which is not physically real, just a labelling mechanism), whereas there IS a real world variance in time outcomes (I'll call it 'true time dilation' for the sake of clarity) which is caused by acceleration, which in turn is caused by changes of direction in the travel path (not by changes in speed). So 'true time dilation' IS real - there really WOULD be a difference in the time passed for Alice and Bob if one was on Earth and one travelled to Andromeda and returned, but that is NOT caused by the relationship between proper time and co-ordinate time. That's what she means by 'real' time dilation. She wasn't saying (to quote you) "we're treating time dilation too literally" she was saying we're misunderstanding what real time dilation is, that it exists but isn't connected to the hypothetical concept of co-ordinate time. That's different. She doesn't 'transfer' from 'velocity' to 'acceleration' in her time dilation argument, she transfers from 'co-ordinate time' to 'proper time (on a hyperbolic real world curve)'. And she makes clear that it's the path travelled, and hence the directional changes and thus acceleration, which determine the time dilation outcome - so observers taking different paths, and having different acceleration, will have different outcomes. Obviously the conclusion, as heavily implied by that, is that observers who are not accelerating will not perceive the same time dilation as those who are - yet you state that she is implying the opposite. The issue of agreement on the ticking of clocks seems spurious - I'm not sure I understand your premise anyway, but even so, clocks are measuring devices, not 'proper time' It's the agreement on the 'proper time' that would matter - when Bob gets back to earth from his trip, he will be physically a different age to Alice. That will be true (and measurable) regardless of how they each saw clocks ticking during the journey period. At no point does Sabine say that Kinematical time dilation isn't real, she doesn't mention it, and you have inferred that therefore she discounts it. But given that her stated aim was to show why basing thinking on co-ordinate time is wrong, she essentially just goes as far as she needs to to explain how that should be replaced by proper time and accelerative dilation. Someone 'not mentioning the second ingredient' is not the same as someone stating that there is no second ingredient. I also have to take issue with your statement that the kinematical slowing of Bob's clock "is the cause of his slowed ageing". Clocks measure, they don't cause cells to age (or not age so much). Bob experiences less passage of time, less entropic effect, which means his cells are less degenerated, less far along their lifetime journey - whatever it is that lies at the heart of "what time is", that ageing is not caused by the operating speed of a measuring device. Overall, you seem to be hung up on how clocks define 'true time dilation' when in fact they just measure it, and attributing opinions and positions to Sabine which aren't there. You 'tease' that you have the answer, but don't give it. Another "I know the answer, you don't understand it" without sharing it - the internet is full of those. I'm always wary of any proponent of a new theory that starts from a position of attacking others. Time to put up or shut up?

Since you are teaching relativity, saying "those who teach it don't understand it either" is a very bold and humble statement...

14:37 _“You don’t understand [special relativity] because the people teaching … you don’t understand it… [__13:12__] We need to re-examine … in particular, the assumption of absolute acceleration. [__15:17__] So hold on to your socks because our channel is about to move into uncharted territory.”_ Excellent research, but you’ve reached a conclusion that is non-physical since non-gravitational acceleration _always_ requires energy. Energy consumption is an observable - a historical result that, once done, becomes irreversible in both classical and quantum physics. Moreover, it requires energy proportional to the acceleration imparted. Thus, if you look at energy, non-gravitational acceleration is necessarily “absolute” regarding the observable energy consumption. The deeper problem is too much focus, then and now, on the non-physical concept of _unbalanced_ accelerations. Those don’t exist. In experimental physics, you _always_ see good ol’ Newtonian action-reaction pairs in which every action (acceleration) has an equal and opposite reaction (acceleration in the opposite direction). The momentum magnitudes imparted to the two units are identical, though the allocation of _energy_ to the two units can vary enormously due to the difference in the mass ratio of the pair. Now, watch this part closely: Would you agree that the successful insertion of some specific amount of energy into a cohesive lump of matter is an “absolute” event in terms of being historical and irreversible in both classical (e.g., batteries) and quantum (e.g., atomic excitation) physics? Yes? The next question is this: Is the lump of matter _required_ to stay spatially localized for its excitation to remain absolute and historical? Of course not. The battery may remain compact in space, but it may also explode. The atom may stay compact for a while but eventually re-radiates the energy or possibly ionizes. Thus energy insertion is an absolute event _regardless_ of whether the unit stays compact. Notice that disruption includes the case of the unit breaking into precisely _two_ components, moving in opposite directions - that is, action-reaction pairs. The point is that action-reaction events - which is to say, _paired_ accelerations - are energy-consuming events within the non-energized frame that launches them. If one pair member is vastly more massive, such as earth versus a rocket, it’s easy (but also not entirely correct) to _approximate_ the launch as a one-sided acceleration. The earth accelerates slightly in the opposite direction, acquiring the same momentum as the rocket. However, the _energy_ absorbed by the earth in such an asymmetric-masses event can, in most cases, be utterly ignored for calculation purposes. But it remains real for both sides since you cannot impart momentum without inserting some energy. Okay, non-gravitational acceleration as _paired_ events is always absolute and historical. So what? What does all of this mean in terms of time dilation? Just this: From the moment of energy insertion into an action-reaction pair, the launch frame always sees clocks in accelerated pairs as moving slower. Notably, there’s nothing relative about this. The launch frame can measure those clocks anytime it wants to, at any point along their paths. When it does, it _always_ sees a total elapsed time identical to the moving clocks ticking slower. That’s why particle accelerators work! A particle accelerator is an excellent approximation of a launch frame since it acquires almost no momentum energy from launching the particles. The particles, however, absorb enormous amounts of energy per particle compared to their rest masses. As long as they retain that energy relative to the frame that launched them, _their clocks run slower than those of their launch frame._ There is nothing relative about how their clocks slow down since that slowdown is _continuously_ measurable as they travel. All “relativity” of time is lost because the launch frame _never_ acquired the energy needed to slow down its clocks. The point is this: Energy acquisition is an absolute and historical event. When that acquisition takes the form of linear momentum, it _constantly and continuously_ slows down moving clocks relative to launch matter that received no such energy. The correct resolution to time dilation is almost absurdly simple: Follow the energy. A final observation: Yes, the Lorentz equation works, but it’s also a bit of a historical disaster that has impeded a more straightforward understanding of phenomena such as time dilation for over a century. The Lorentz or gamma factor, γ, is a computationally messy average of two more important numbers: the forward light path ratio R and its inverse 1/R [1]. The Ratio is identical to _e_ to the power of the particle physics quantity known as rapidity, but it’s a lot easier to think of it as the ratio (to the rest-frame case) of how much farther light must travel to reach the front end of a moving object. This ratio increases as the velocity of the object velocity increases since the light must travel farther to “catch up” with the front of an object that is moving close to lightspeed. ---------- [1] T. Bollinger, _Formulas and Google Equations for Converting SR Velocity Factors,_ Apabistia Notes 2023-02-08.2230 (2023). sarxiv.org/apa.2023-02-08.2230.pdf (a PDF copy of this 2023-04-29 comment is available at sarxiv dot org slash apa)

"... and explaining that our confusion about relativity stems from the simple fact that we're treating time dilation too literally" That's not actually what she said, nor what she meant. There's a real and measurable type of time dilation, and the confusion she tackles leads people to think of another type of time dilation that she labels "pseudo time dilation" (the meaningless one). "But as she implies in the beginning it's the idea that any type of time dilation being real that confuses people" What I heard her actually say was "confusing the coordinate time with the proper time is the reason for most misunderstandings for Einstein's theories that I have came across" Then, immediately after that, she goes into why that confusion over coordinate time and proper time leads to a meaningless idea of time dilation (she says "what people often call time dilation") which she then labels "pseudo time dilation" because "it's a meaningless comparison". "Secondly, she neglects to mention that observers who aren't accelerating will not perceive the same manner of time dilation as those who are". Are you lying on purpose? The very section where she mentions the "real time dilation" is the section where she's resolving the twin paradox by showing the asymmetry of someone who experiences the acceleration and someone at constant velocity (0 in this case). That is literally mentioning someone not experiencing the time dilation due to lack of acceleration. There's no way not to hear her mention the thing you're saying she neglects to mention. "So by no means can we claim accelerated time dilation to be more or less real than velocity based time dilation". But the velocity based time dilation is meaningless, due to treating something as real (the coordinate system) when it doesn't have a physical counterpart (unlike proper time). If the velocity time dilation exists only in the abstract after confusing coordinate time and proper time, but acceleration based time dilation has absolute, measurable asymmetries, then of course one is real (supported by evidence, and logically consistent) and the other isn't (we can literally identify the confusion, and resolve problems like the twin paradox by removing the confusion).

Honestly I never understood relativity, explanations are so ambiguous, so I'm glad to know that's it's not me, at leat it may not be just me. I will wait for your next video, yours is the best analysis I've seen. Congratulations

Probably the most radical interpretation that I've seen of General Relativity is a 5D one. This one caught my eye largely because of your great videos on the metric tensor. In it, you described how it's like trying to translate from the distances and angles on a map into the distances and angles on the physical curved globe. The only problem with this is that the metric tensor in that context is nothing more than an artifact of trying to represent the surface of a 3D object on a flat 2D plane. What's more intuitive: angles and distances changing mysteriously as you move around, or angles and distances changing because the surface is physically being extruded into another dimension? Distances on a map changing would be very confusing... up until you realize that it's just because there's a mountain at that point with large changes in altitude. Returning to general relativity, the analogous operation would be to introduce a 5th dimension, likely having some relation to mass, energy, or gravity, and then have the coordinates in this dimension change so that the overall length of the vectors being used stays constant regardless of what reference frame you measure them with. You are correct in that we need more people accepting that general relativity, like quantum mechanics, has multiple interpretations, and that pretending that there's only one is confusing when everyone presents their interpretations as _the_ interpretation.

You seem confused by Sabine pointing at two different examples of time dilation, and calling only one of them real. And no, she's not transferring it from velocity to acceleration, but from passing to coming back to meet. The meeting is the important point here. _she neglects to mention that observers who aren't accelerating will not perceive the same manner of time dilation as those who_ Apart from using those exact words, you actually quoted her when she did?! And yes, it's not acceleration per see, it's meeting up again that creates the "real" time dilation. Two objects taking different paths through spacetime from spacetime point A to point B can, obviously, compare the time they spent on the way between the same set of points. That's the real point here. OK, you even quote her saying exactly this?! _saying only accelerative time dilation is real while kinematical time dilation isn't_ ... you seem confused about what she is saying, or rather, what meaning she is trying to convey. Your Einstein quote suggests that you think she's talking about absolute movement?! Where on earth did you get that nonsense from?! I think your problem is that you expect everyone to conform not only to your personal interpretation of relativity but to your personal way of talking about it. Ah, yes. "They do it wrong, but I won't tell you what is the right way ... but keep watching." I think I know enough by now. Good bye.

OK, several serious problems here. Yes Sabine is incorrect in attributing the time dilation purely to acceleration - a common mistake in explaining the twin "paradox". But you introduce a notion of there being different "interpretations" of general relativity, on par with different interpretations of quantum mechanics. This is inappropriate because there is _no_ disagreement or mystery on what the math of general relativity tells us about what's physically happening; QM has the opposite situation, hence its various interpretations. You also place heavy emphasis on Einstein's personal knowledge, beliefs and opinions about GR. It doesn't matter what Einstein thought. I can't find the exact quote but it's as modern physicist Sean Carroll said, something like "I know more about GR than Einstein did, not because I'm smarter than Einstein, but because we've learned so much more about it since then." Worst of all, you leave the viewer with the impression that time dilation, length contraction, and relativity of simultaneity are just "heavy-handed space-and-time-altering pseudo-mysticism of relativity" that could be avoided with different "interpretations". _What?_ These effects are _observed in experiments_ and do not depend upon choice of coordinates as you say they do. 11:40 "If we want to treat time dilation as something real, then since different observers don't perceive the same manner of time dilation as one another, we seemingly have to accept a solipsistic worldview where different observers can construct different narratives of their existence." Different observers having different observations along their different worldlines is simply not a problem; invocation of solipsism is not warranted. This video's title "The REAL Reason You Don't Understand Relativity" is ironically accurate.

In my experience, the best way to understand the twin paradox (and the rocket paradox) is as follows. A clock measures time, like an odometer measures distance. This allows us to translate the twin paradox in spacetime to a similar paradox in 2D space, which can be understood more intuitively. Imagine two straight roads crossing each other at an angle of less than 90 degrees. Two cars start from the crossing and drive the same distance along each road (on their own twin odometer, or up to the first milestone along the road, assuming those milestones are at equal distance from the crossing). There they stop and observe where the other car is, relative to a line perpendicular to one’s own road. Both will find that the other car is behind and needs to travel further to reach that perpendicular line. This is the same principle as the twin paradox. Next, let’s call the cars Alice and Bob, and imagine there is a third straight road, which crosses Bob’s road where he is and Alice’s road somewhere ahead. Bob makes the turn to get back to Alice’s road. Immediately after turning into the third road, he observes Alice’s location again, relative to a line perpendicular to the third road. From Bob’s new perspective, Alice seems to have “jumped ahead”, simply by turning, even though Alice has not moved at all, and from her perspective Bob has hardly moved while turning. Finally, both continue their journey up to the point where the third road crosses Alice’s road, where Alice and Bob meet again and compare their odometers. Surely both will agree that Bob travelled a longer distance than Alice. It does not make sense for Bob to say that he travelled in a straight line all along and that it was Alice who turned back to him (even though her relative direction did change from Bob’s perspective while he turned), as that is simply not true and would lead to an incorrect theoretical calculation of odometer readings, which does not agree with the actual odometer readings. Only if both agree that Bob turned and Alice did not, they will calculate the correct readings that agree with the actual readings. This is a perfect 2D analogy of the twin paradox. The travelled distance translates to proper elapsed time, the odometer readings to clock readings. Bob’s change of direction by turning translates to change of velocity by acceleration. The math is not exactly the same, but very similar.

This video is 90% chaff and 10% wheat.

This channel still suffers from two things: 1) promises of explanations "in the following videos", still waiting for some/all 2) looking down on other physic RU-vidrs with long experience in research (and also hobby physicists). It's really cringe-worthy Those two facts make it hard for me to continue watching your channel.

I’m glad that channels like dialect and scienceclic exist. Dialect needs more recognition.

I've said this before on one your videos, and I'll say it again. Absolute acceleration necessarily falls out of how you choose what a constant rate time coordinate looks like. In relativity, we have one fundamental example and that is the one of the light clock. We can then define acceleration with the amount a light clock would veer from reflecting back into its aligned spot. I understand what you had said in previous videos regarding Newton and Mach's bucket, as well as the spring example from Sabine, but the light clock is a fundamental example. And any other method of keeping track of a time coordinate that agrees with a light clock will therefore necessitate this interpretation of absolute acceleration.

I didn't see Sabine's video but from this video, I feel like there is a misunderstanding. The postulates of special relativity just simply cause the fact that certain physical quantities that were well defined in Newtonian physics are no longer well defined. One of such quantity is for example length. Since we don't have absolute simultaneity anymore, it is difficult to define what the length is because if we want to measure length we need to measure the coordinate position of two ends of a certain object simultaneously. Therefore without absolute simultaneity, coordinate length is no longer a good quantity which means it depends on the reference frame you measure it in. Therefore if you want to define a quantity called length, you have to specify better what it means. For this reason, we have "proper" length which is the length of an object in its rest frame. This is the same with coordinate time. Coordinate time is no longer a well defined quantity in special relativity because how can we compare two clocks if we don't have an absolute simultaneity? for this reason, comparing time only make sense when measured at the same position so that the relative simultaneity is negligible and therefore time difference on two clocks have a real physical meaning. When Sabine said acceleration makes time dilatation real I think she meant that it is necessary if we want to compare two clocks at the same position because there is no other way to bring the clocks on one place. Therefore acceleration is the key to make time difference on two clocks a well defined quantity and therefore "real".

I think the most confusing element in ALL attempts at explaining relativity, including yours, is the notion of an observer observing clocks. We are talking about a theory where observations and their comparisons are critical and yet its never clear whether these observations take into consideration the light travel time between the observer and the observed or whether we are talking about a weird instantaneous observation which assumes some kind of simultaneity in a theory where time is relative.

When Sabine says that Time Dilation really occurs in the absolute acceleration (and not the kinematical, velocity-based scenario) you go on to point out that observers accelerating (A) and not accelerating (B) won't be able to agree on the time dilation, so they both have the same measure of "realness"... but the point is that this very disagreement only occurs because of the one that accelerates in the first place (A), whereas the one which we assume doesn't accelerate (B) becomes our chosen base coordinate system. Time dilation is certainly more on the side of acceleration (A), because otherwise, if we attribute the same value to both twins' perspectives (the the other, accelerating in relation to us, will be younger) the twin paradox would be an actual paradox: instead, as per the minutephysics video you linked, there is a certain asymmetry, so that the difference in time elapsed only occurs because of the one that performed the journey, and we can be certain that the one who went on the trip and is younger is the one that actually suffered the time dilation. Kinematical and accelerative together describe the elapsed proper time, sure, but elapsed proper time is not at all the same as time dilation. Overall, it seems more like a nitpick than anything else, so I don't think the hostility is really warranted - just by attempting to clarify actual science, all of these channels are already doing much better than those that subvert science not out of ignorance but outright malice, like flat earthers, quantum mystics, crystal scammers, and so on.

I think special relativity should be taught using the two postulates and the consequences of those two postulates. The implication of the second postulation is that signals has a finite speed. It’s not instantaneous. Time is a separation of a series of events. An observer is just a system receiving a signal from those events. For example, an electron releasing a photon and another electron receiving that signal. If the recipient is moving relative to that signal, say it’s moving away, the signal will have to take longer to reach the recipient. If a physical processes is the exchange of photons between particles, that delay in signal is time dilation.

I also think a reinterpretation of Mach's theory of there being an absolute baseline velocity in the Universe against which all velocities are measured is possible, now that we know the Cosmic Microwave Background is a plausible "ground zero" of velocity in the Universe. Objects at rest relative to the CMB do not experience time dilation. Those that are moving relative to it do, according to the Gamma function.

Sabine is an expert in QM, not relativity. Her channel covers a wide range of scientific topics and she generally does a really good job, but it often isn't perfect.

so condescending and for what? You sound so somewhat immature

The other part is (sorry for the numerous separate comments). Almost every clock we use is based on spin (except the ideal photon clock, and sort of an hour-glass, which in order to work would have to be in centrifuge and you're back to spin). Spin^2 + velocity^2 = C^2. Although this is generally written as S^2=C^2-V^2. And then we go 'why minus?'... well because it's really part of the sum of the other side. If you are going the speed of light you're left with 0 spin; a photon doesn't change orientation while it travels, it's identical in spin when it arrives as when it leaves. Our matter though is based on spin; and if we were going congenitally at the speed of light, we should have problems with our matter even working like matter; but the atoms are all slowed down because spin is limited. It's possible to model this same dilation using the photon clock mounted perpendicular to the velocity - but a photon clock mounted parallel to the velocity has 2 different speeds of covering 1 meter : 1/c+v and 1/c-v. At 0.5c, that's 1/1.5 =0.66. 1/0.5 = 2; and the round trip time is significantly longer than the lateral clock perpendicular to the length; but now we have to also accept length contraction, then that length can be scaled back such that the long round trip takes the same time as the horizontal. There are very reputable sources like Heaviside that first noted contraction of electron clouds. In my own development of the math of relativity (from the ground up, not assuming anything was right, except 1) the speed of light is constant. (The extra part, in any frame. which Einstein includes ends up falling out from the math, and doesn't really have to be postulated); but then the only way that LIGO would work is if there was length contraction to make the two arms the same time-length.... so I finally found what the space-gamma for length contraction and the time-gamma for time contraction (it's not really a dilation, since it's always a slower clock, except at absolute rest). Anyway, recent 3D demos I've done demonstrating this with simple reality that every photon is essentially a fixed location in space; once emitted, it no longer has anything to do with the source it was emitted from; it doesn't inherit any velocity (except in its waveform, which is red shifted behind the velocity and blue shifted in front and various degrees in between around the sides); but otherwise the network of all points that light was emitted from form a stationary background upon which all motion can be found. Oh - BTW - before I did this light speed relativity stuff, I did space curvature; what if it is that space is literally curved (which Einstein said 'don't consider it this way') but if it was, we would still the same gravity lensing around things, if something like a sun shoved the space even 9,000km to get the right arc that Eddington saw when he measured a star around the eclipse, that's not that much space... that's only about 200 femto-meters per atom; and we measure atoms to be around 60-80. But, if they did displace space, then the things we use to measure them are also shoved away, and flow around a thing, meaning we would think it was a lot smaller than it really is. A black hole then isn't infinite curvature or infinite acceleration, it's just a large displacement of space, which contains the stuff that all other atoms contain, but in MUCH greater quantity. (Could CERN produce a black hole? No, but they can slam together matter-size black hole and destroy them, and we're not doing so well at condensing matter out of photons). But that's even older videos; and a different set of simulations. There was no big-bang (not as we imagine it now anyway). Space is overall stretched by matter, and all the stretching from all the matter that light passes by and doesn't interact with (if it did interact then we wouldn't have seen it), that space is stretched longer than it would otherwise be, which over the time the photon passes through this, has to cover more space in the same amount of time, which stretches out the wave; pretty much a fixed amount for the distance it travels. I'd imagine this space stretching is more of a factor in the nearby space, so things that are near by are more red shifted in less distance than very distant things. The universe is flat (except where it's locally curved by matter). I predicted even before JWST launched that when it did get to see things, it would see galaxies very much like our own as far as it could see - was thrilled to be right :) Too bad I'm noone, and you know it's said to be 'one of those things no-one expected', which was right! :)

I continue to enjoy these videos. I am very much in favor of the idea of presenting the philosophy underlying relativity (or differing philosophies/interpretations). I find that very helpful in my field of statistics, and it is hard to find any discussion of quantum mechanics which does not address the philosophical concepts. If this aspect of relativity were a standard part of explanations of it, that might help prevent some of the confusion from different sources giving different interpretations/explanations of the math.

Time dilation is happening in two ways for satellites, speed, and gravity. The correction calculation for prediction and control are two parts. Calculations Combined: GR predicts that GPS satellites gain 45 microseconds daily due to Gravitational Time Dilation (time passing more slowly in a gravitational field). SR predicts GPS satellites lose 7 microseconds a day due to Kinetic Time Dilation (time passing more slowly in a moving reference frame).

Oh what a teaser. I want dialect to offer up something. Debunking works best if you can offer up the correct solution.

Dialect, sorry to be impatient.. but can I ask when you expect to be uploading your next installment of your interpretation of Relativity. I'm sitting here in Costas pondering the equivalence principle.. and I need your help :-). It is strange as it feels that there is a simple hidden answer explaining the equivalence phenomena that is just out of reach. There has to be a connection between SR and length contraction and GR spacetime curvature. I'm suprised that an accellerating Mass does not produce a wake in space time like a ship does in water.. but it doesn't. Can we think of GM like an infinite number of slithers of spacetime radiating out from a radiant, and imagine the slithers of spacetime in terms of SR. Then each slither can be thought of in terms of SR with length contracting in the direction of acceleration of spacetime. Ie in the direction perpendicular to the radiant. . Sabine was saying whilst talking about The Twin Paradox, that SR and GR differ because there is no curvature of Spacetime in SR. But if what I just said has merit then there is no difference..ie curvature is a infinite number of radiating slithers of SR spacetime from a central point. It amazes me how feeling Gravity is like accelerating without moving... I'm rambling lol.. Anyhow looking forward to your next inspiring upload. :-)

I'm really enjoying this channel. The videos on the twin paradox are quite good. Good thinking ... Cheers.

Just love the explanation in relativity for Reciprocity - people look smaller to each other at a distance and squares become rectangles when looked at from an angle! LOL So this proves that TD is just fine!

The best question verifying understanding of GR I've come up with: what is the difference in clock ticking rates between object free falling in gravitational field compared to distant stationary observer? Assuming their initial relative speed was 0.

Do you have a link to the chart of Einstein's Interpretations, at about 03:35 in the video?

Thank you for the video. There is a hypothesis - a single picture of the universe: When moving and fluctuating in a vacuum, the electromagnetic field in the nodes - Forms quanta of gravity - Which carry the speed of light. Suppose - Can be detected using a mobile, new hybrid - the experience of Michelson Morley, if it is in motion relative to the DGF - the dominant gravitational field, for example in 🚆, as in Einstein's mental experience.

Does an object that is free-falling towards a large mass (still at low velocity) experience time dilation? I didn't get the answer from Sabina's video, and I didn't get the answer from this one either.

At first, I was with you against other physics content creators about the nature of gravity and how time dilation is not actually causing gravity, but you kept repeating one fundamentally wrong concept which is that acceleration is relative. This is confusion on your behalf. In most of your videos, you either explicitly state that acceleration is relative, or you interpret absolute acceleration incorrectly. A simple example is that at 8:00, you failed to take into account how the inertial satellite sees those clocks on the screen as accelerating thus indeed having time dilation due to their spacial distance separating them. What Sabine was saying (or at least the correct way of seeing things) is that in special relativity, there is no way to communicate our time difference. It is meaningless because we cannot measure it. In general relativity we can measure it, so we interpret it as a real phenomenon and not just an artifact of our coordinates. It seems that you are a strong advocator for mach's view about the relativity of everything. You are assuming acceleration is relative, but you are failing to take into account how our physics change when we do so. You either interpret acceleration as absolute, or you have to include other factors in your equations. Exactly how you can interpret a person in a rocket as either accelerating, or under gravity, or a mix of both. Since you are always getting the latter interpretation wrong, I would recommend that you just stick to the simpler interpretation "acceleration" is absolute. The math of General Relativity is not easy, but it's not ambiguous. You can clearly find an answer and there is no room for debate. You should focus your arguments on the communication and simplification of these subjects and not the math itself.

I think of it this way:.......Draw a square 100mm by 100mm, and draw 45* line from bottom left to top right....Mark the top triangle Phi and the bottom triangle Psi..( they slide past each other on the 45* line, either up or down).....In the center draw a horizontal line any length left to right and a vertical line north and south. Slide the two triangles past each other while keeping the horizontal and vertical lines stationary. While sliding the triangles past each other at different speeds, the horizontal line would vary in lengths measured from the center point outwards as they indicate the volumes on the vertical line. The 45* line would indicate the change in respect of time. To me, and if all three movements are taken together in time ,, would explain time dilation as the inertial capacity changes from the macro source to the point source, and vice versa. This can only work if it is calculated using a cubic volume of space filled with aether, Apparently a spatial algebra has to be developed for that to succeed.

Special relativity at university is commonly taught without interpretation of spacetime itself, but just as a natural consequence of electrodynamics on a moving frame

Its a fallacy to say that because someone makes a mistake when communicating something that they don't understand the theory. Did you even try to contact her and ask for clarification ? It's also a fallacy to say because of one error (if it is that) all youtube science communicators fon't understand it. You also seem to suggest that none of these people, some of them well versed in the subject, dont know about the alternative interpretations which is unlikely since they are experts after all. You could have made your point by making a video of the correct interpretation. You basically wasted time and effort on something that could have been a few sentences in that video.

Relativity admitting it has a problem... I never really thought about relativity in terms of interpretation, the way quantum theory has a whole interpretation industry attached to it. This will be a fascinating topic to follow!

I think the problem is more like this. >Mass does effect the scale of matter in that it is smaller where the mass is higher. >Acceleration is caused by an imbalance in the matter caused by the forces relationships in the matter as per the spatial changes. >Acceleration requires matter in which two things in a force relationship exist, like EMR. >Matter slows down because some of its constantly moving parts go further when there is a higher velocity, so the matter slows down, but time in the Universe is totally universal. >The idea things are the same for all observers is true until close to the speed of light is correct coincidentally.

This is, again, a very interesting point you bring up in this video. The explanation about acceleration causing "true time dilation" is not only problematic, it is also factually wrong. Indeed, it is very well possible for two objects to start from a same point, follow two different trajectories while both are in free fall - not experiencing any acceleration - and then meet again with desynchronized clocks. That's what happens for example if we throw an apple upwards from the space station, such that it falls back to the station after one orbit. My interpretation of relativity would lead me to say that the "true cause" of time dilation is simply that two objects following two different paths through spacetime have no reason to have travelled the same "distance", i.e. the same proper time. But as you explained, it is in fact dependent on my own interpretation (which I think, though, might be one of the most common amongst relativists today), and it relies on the philosophical assumption that spacetime has an absolute geometry, independently from its content. Something Einstein might not have been satisfied with I guess. An interpretation of relativity I really like is the one following from the Hawking-King-McCarthy-Malament theorem : spacetime would only be a set of events causally linked to each other, and its geometry would only be a macroscopical / statistical property that emerges from this structure :)

Interesting take, will need time to digest it fully. Can you do one sharing your thoughts on eternalism and whether time is "real"? I'll be keeping my eye on this channel.

There are some heavy misunderstanding and misrepresentation of what Sabine actually said. Sadly it is too much to explain it here in the comments.

In earlier times I used to say/ write that the close connection between spatial and temporal quantities _allows_ us to merge time and space into spacetime. Since then I changed my mind thoroughly in the sense that spacetime is a thing anyway, and we need some reference body B in order to _split it up_ into time and space, the former being the time determined from B, the latter being the set of locations, i.e. positions relative to B. Since positions and velocities are defined with respect to B, we consider B stationary. If there is a second body B' moving with constant velocity v›, we are free to choose B' as reference body instead, so that we now consider B as moving at −v›. This principle is much older than Special Relativity, it's from GALILEI. What we formerly considered a location, namely a fixed position in space, has now become a position co-moving with B. Even if time were something absolute as NEWTON stated, space definitely isn't. So, I would teach the concept of spacetime _before_ going over to Special Relativity.

_Indeed, physicists being unable to make up their minds about what the meaning of time dilation actually is probably the biggest source of confusion in relativity, and why you get such backwards ideas like 'time dilation causes gravity'. Is time dilation something real - something that should modify our idea of true immutably flowing time? Or is it just an artifact of how we've chosen to formulate our theory and draw up coordinates? This is where the formalism of relativity doesn't provide any clear answers, and consequently where the personal interpretations begin to flow._ That's fundamentally confused about what physics is doing (not to mention just wrong on several counts - like that they don't understand the the meaning of time dilation). The formalism of ANY physics theory is always inherently open to differing interpretations, so there's nothing special about special relativity in that regard. He doesn't seem to fully appreciate the distinction between the theory versus the human interpretation (model) of that theory... nor that it's not a scientific question as to which interpretation is describing "true reality". Physics makes conceptual models so that the laws of physics can be correctly applied by the human beings who understand situations in light of those models. If someone doesn't like those models, and prefers to use another, that's fine... so long as that other model still produces the same physically correct predictions. If you want to speak about invisible gnomes pushing things, instead of forces operating in the world, that's fine (weird, but whatever...), just so long as your invisible gnomes push things according to F = ma. If two descriptions are always empirically the same, then you have: _same physical theory, different interpretations/models._ If two descriptions are empirically different anywhere, then you have: _two different physical theories._ So it's entirely unclear to me what this guy actually refers to when he says there's some "confusion" within physics about relativity. If someone wants to understand time dilation in terms of acceleration, or whatever, that's fine... provided the empirical consequences of such a position are the same as what "normal" physics predicts. Differing models of the same theory aren't a sign of "confusion" about the science itself, but rather are a debate over the preferable perspective & interpretation of that theory (or, for the confused, those are philosophical debates that the debaters have mistaken for scientific debates). Always ask if there's, in principle, some experiment that could distinguish the two descriptions, i.e. where the two descriptions predict different outcomes. - If the answer is yes, then you have two different physical theories, and in principle scientific investigation can eventually distinguish which is one superior. - If the answer is no, then you have two different descriptions of the exact same physical theory, and so physics can't distinguish between them. In that case, you can make philosophical and pragmatic arguments for which description to prefer (I prefer forces to invisible gnomes), but scientifically there is no difference. After all, what experiment would you perform to distinguish the two, to decide which model is the "correct" model, if both models predict the same outcome for any conceivable experiment? It's common to view the models created by physical theory as "speaking about reality", but that's a philosophical (ontological) issue that's separate from physics itself. Physics itself produces conceptual models that allow human scientists to apply the laws of physics correctly. (Humans are notorious for relying on conceptual models when trying to conceptualize.) Whether those models represent "reality" is an entirely separate matter, and one not decidable by scientific inquiry, but rather only philosophical argument. If I give an "alternate" theory of physics that's predicatively identical to "normal" physics in every way, but uses different conceptual models in the description, then which of the two models - mine and the usual one - is "correct" is entirely a philosophical question, since the two are empirically identical. Aside: This wasn't me being dismissive of the importance of debates over the interpretations of scientific theories. It's important to have the best possible conceptual models we can construct, since better models means greater ease & correctness in applying them. Even more importantly, better models allow us to ask better questions, and so best spurs further fecund research. My point here was simply to lay bare the distinction between a theory and its interpretation, and to note that the issue of ontological truth isn't a scientific question, but a philosophical one.

This video is well put! One question though: why do you think that absolute acceleration may not be true?

I still disagree with you on whether absolute acceleration is necessary for relativity. But I'm on the edge of my seat and excited to hear more about this interpretation from your channel. I do think that if acceleration were not absolute, it would be more parsimonious in some sense- more consistent with the original motivation of relativity, describing how the laws of physics could apply in any reference frame. I hope you prove me wrong!

The most amazing thing about Relativity is that we had a fella looking for some math for light, and the next thing you know he has decided that the Lorentz Transformation doesn't just apply to length but to time as well. The assumption that time passes differently from frame to frame is now not merely talking about light but the entirety of physics because time is involved with virtually all calculations in physics. Had he said it was absurd that time passes differently from frame to frame, and just gone with length contraction, then this would have basically been a description of how light's Aether bent, stretched and contracted and not effected the rest of physics at all. This was/is monumentally significant!

13:13 "We need to re-examine one assumption of relativity in particular ('ONE CRITICAL ASSUMPTION'): the assumption of absolute acceleration". No. We really don't, because the assumption of absolute acceleration is not an assumption of general relativity - nor even of special relativity. The assumptions of special relativity include: (1) if you have a frame of reference which is inertial, and a second frame which is moving at constant velocity with respect to the first, then the second frame of reference is also inertial, and (2), the speed of light is constant in all inertial frames of reference. Absolute acceleration is not an assumption, it's a conclusion, it's a consequence - an application of logic to these two assumptions (to be fair, to make the case airtight, there's probably another assumption, I imagine something along the lines of: if a worldline is observed to be continuous in an inertial reference frame, it is continuous in any frame which accelerates smoothly with respect to an inertial frame). It's true that many explanatory texts and videos may make the assumption that the reader/viewer knows that it is a necessary consequence of GR that there is absolute acceleration. Being a necessary consequence is quite different from being a critical assumption.

I enjoyed this video greatly, but I did get the impression that you placed a lot of emphasis on Einstein's own thoughts on GR, rather than on the corpus of cosmologists who came after him. As you said, Einstein was mired in his own philosophical assumptions (divorcing coordinates from physical significance was something that he lamented didn't come sooner). Sabine's video is probably one of the best, in particular for mentioning proper time, coordinate time, etc - it's so important but you rarely see it in popsci videos! But I agree that her distinction between a 'real' time dilation and a 'pseudo' time dilation is erroneous.

But isn't Sabine's whole point that the time ontology is based on measurable effects. Therefore your example of the constant gravitational field and the two observers would show one aging slower if they were able to measure their internal clocks against each other. So just like in the twin paradox, this shows her time dilation perfectly.

Explain tree ring growth using General Relativity. Explain the lifespan of a northern vs southern tree using General Relativity. Explain seed emergence using General Relativity. Explain embryo development/hatching using General Relativity Explain why clocks in motion use the same amount of energy as stationary clocks using Special Relativity Explain why solar sails are accelerated in space when a force is applied while a plant is accelerated in time using Soecial Relativity. Explain why the solar sail is losing mass through radiant heat while the plant is gaining mass using Special Relativity. Lastly. Explain why an astronaut's heart rate is in an accelerated state during lift-off while the onboard clock is recording fewer clock cycles using whatever Relativity you deem appropriate. If you look up Relativity in Wikipedia, it states that biological processes mimic mechanical processes. Why isn't the astronaut's heart rate slowing down? The scientific community has gotten away with bamboozling the public with their mathemagics and pseudo-science. We are not buying it anymore.

The physical in relativity are the invariants, for example (ds)^2, which are the same for all reference frames. Observation measurements are reference system dependent. The most direct measurement of time and time dilation is measuring particles decay or atomic level excited states decay processes (half life). For systems moving fast relative to us, no acceleration, we should observe a different decay half life exactly according to special relativity. You cannot get more physical than that, reference system dependent time measurement that is different from the proper time of the decaying rest system. I looking forward to your interpretation.

Surely by now, given how we've launched probes into space that use gravity assists, and often return back to Earth a few times during them, we've figured out EXACTLY the solution to the twin paradox, calculated how much time dilation you expect zipping away, delta-ving 10 or 20 km/sec, returning and comparing clocks, or looking at the shift in carrier frequency of their uplinks back to us, or something smart like that, and know FOR SURE a solution?

It seems to me that you have misunderstood what Sabine is saying. I rechecked her video and what she is saying makes complete sense and is pretty easy to understand.

If there were two twins and one twin was somehow teleported into a spacecraft traveling near the speed of light from Alpha Centauri, when that twin arrived at Earth, since there was no acceleration but a constant speed close to the speed of light, would the two twins still be the same age? Or because the one twin was traveling at the same near light velocity the entire trip would that twin still be younger if they were to communicate as they passed each other one on the earth and the other in the spacecraft?

It should be obvious from Einstein's time dilation formula: γ = √(1 - v²/c²) that time dilation is produced not by acceleration, but by velocity. What's not obvious, however, is which frame of reference should be used to measure that velocity? Mathematically, you're calculating the ratio of velocity to the speed of light, but that's not much help, since lightspeed (in vacuum) is the same regardless of your frame of reference. So 1/c² is in practice just a constant scaling factor applied to v² to produce a non-linear time dilation factor (1/γ) that asymptotically approaches infinity as velocity approaches lightspeed. Hence, there is no such thing as "absolute" time dilation, it must always be measured relative to a specific frame of reference, and depends solely on your relative velocity.

I asked a question in the comments of Sabine's video, because I was not convinced of the need for acceleration. Suppose the universe is an hypersphere, that is, going straight returns you to the starting point, who ages more, Alice or Bob, as both do not accelerate? I received no response. I hope this channel (which I appreciate a lot) will help me answering the question.

Time dilation is real regardless the interpretation or phylosophical stuff, GPS clock adjustment is one example of it. Physicists usually just shut up, calculate, and verify it with the experiment. Even the interpretation of electromagnetic wave or Newtonian gravity in classical physics that being thought in highschool has this kind of interpretation problem.

No two observers will view the clocks the same simply due to their relative instantaneous positions; of the clock at the instant it emits the EM Wave peek (photon), and of the observer when it detects the same EM Wave peek (photon), and latency of propogation of the EM Wave... Nothing to do with acelleration...

My sense is that the underlying model is wrong. We seemed to have backed into a new version of planets and epicycles (wheels within wheels). And it seemed to go wrong around the time of Michelson-Morley. My physics teacher didn't teach that the MM experiment disproved the aether; rather that it found nothing. Some might say from that that nothing means the aether does not exist. Or.... your trap to catch some _whatever stuff_ was not a good trap. Nowadays, we understand that an aspect of gravity is that space continually falls into the planet (that's what tries to "push" us down to the ground - see any of Professor Michio Kaku's lectures re gravity and the flow of space). Let's suppose that space and aether are linked (same?). My understanding is that the MM experiment took Earth to be like a ship ploughing through water, so measured a suspected sideways flow displacement on a flat, land based interferometer - a table of apparatus, which could be rotated in a flat plane. To no visible result, regardless of orientation, time or season of year (Earth's place in orbit). Let's now take it Kaku is right. Space is falling in down the z axis onto the apparatus, not sideways on some x or y. The whole MM experiment is now seen as carefully analysing the wrong axis. I'd say that that invalidates the work. Which does not prove some form of aether exists, but does suggest a point at which things started to go astray. After all, prior ideas of aether and vortices worked rather well for James Clerk Maxwell. I would want to widen the intellectual search, especially looking for omitted factors. There may be something at spacial foam level which we have not spotted, or suspect exists, which can explain what is going on. Re Einstein and the aether. HA Lorentz's argument c. 1916 convinced Einstein of the validity of some form of aether. The argument (paraphrased) was: "You can stick a physical probe into a region of space and sense physical properties (eg with a gold-leaf electroscope). For that to be possible, space must possess an aspect which is physical." Another hint from Einstein (not sure of date; again paraphrased): "All forces are forms of geometric curvature of space". Chase that and you may get somewhere.

Another great video, wish it was longer. 👍

6:08 another reason it doesn't make sense to name everything after a person: the Lorentz transformations were discovered by Voigt? It's like the Hessian and Jacobian matrices... one is a first order derivative, the other second order. Calling it a computer makes a lot more sense than "Bob's magic box" especially when Bob stole the idea from Jessica. Love your channel ✨

4:25 I can't find that video from Sabine Hossenfelder. At least give a link to it in your notes.

I think she gets the idea of acceleration as being equivalent to the "force" of gravity because it's measured as acceleration, also. Frankly, I have doubts that velocity has any effect on the passing of time. I've only heard the example of moving towards or away from a clock at light speed. However, I do believe mass affects time

Another rare solution to the twin paradox regarding only kinematic time dilation (without acceleration) is the use of relativity of simultaneity to prove that both stationary and moving twins agree with each other that it was actually the moving twin that experiences time slow. Can this be the real solution to twin paradox? What are your thoughts on this? (Btw great job! Amazed by the quality of the video 🎉)

Hey Dialect, absolutely love your videos! I was wondering what you think about the interpretation of GR where an object's worldline follows the path through spacetime which minimizes the Action and therefore is the "straightest and shortest" path which also maximizes the proper time interval of the worldline? Is this different than just curvature in the time direction in Lorentzian spacetime?

Totally agreed with what you said. Just to complete you, in one of his letters to Reichenbach, Einstein said: “It is wrong to think that geometrization is something essential. It is only a kind of crutch for the finding of numerical laws. Whether one links the geometrical intuitions with a theory is a private matter.”

At 8:00 it is stated that an observer free falling in a uniform gravitational field will not measure a time dilation gradient while an observer stationary (accelerating in place) will; this implies the time dilation in this case is observer dependent. Does this argument apply to REAL non-uniform gravtiational fields caused by massive bodies as well? Or is the time dilation caused by spacetime curvature observer independent? I.e. would an observer free falling towards the Earth measure the same elapsed time at the surface of the Earth as another observer that is "stationary" on the Earth's surface?

The only absolute in this channel is the authoritative projection of the author.

I can't wait to watch the second part of this video! Thank you!

Great video. I have said this for a long time. General relativity isnt a theory, it is many. It comes down to which physicists who are teaching it.

im genuinely more excited for the next entries on your channel than an episode of any show ive ever seen

Good luck on your venture. I've been studying Special Relativity for some months now; I'm retired and have time. Started with videos of Dr. Brian Greene and went through most of the persons you show pictures including Dr. Sabine Hossenfelder etc. She was particularly confusing. I got a good feeling for the time dilation from Greene's math version and watched him do some derivations, etc. Of course I can understand the photon clock explanation but most clocks are not photon based and to state our metabolism slows down with motion is a bit too much to grasp. My Point: no data for some of that. So I'm kind of heavy into it and still cannot tell others what causes time dilation. Hope you can do better. You state Einstein did not get into too much explanation so that is a bit scary for hoping I will someday understand it all. Good luck. Try to use "plain English" If you can't explain time dilation to an intelligent person in words and diagrams and of course maybe some math, then you won't have succeeded.

Interesting video as always, that teases the debate between realism and anti-realism in science!

Dialect, is there a private way to contact you? You bring up some interesting points in your videos which I would like to collaborate with you about to expand on some ideas (that you would seem to agree with) for a couple papers that I plan to publish. I welcome you to be a coauthor.

13:27 Clearly acceleration is not as absolute as speed of light, but on the scale of absoluteness, it is more absolute than velocity. Different frame velocities do not change local physics while different frame accelerations do. Also, if velocity is measured, no one can really determine who is standing still and who is moving, hence perfectly symmetric ambiguity. However, if acceleration is measured, there is a physical test to determine who is accelerating and who is not, and there is no ambiguity.

You are a real hidden gem I swear! You and science clic are the only youtubers I do trust with physics and who's opinion I place above the rest. But I actually got one question. Is there a solution(s) for the twin paradox? It seems like there might be some different interpretations about it. I want to know if there is a objective solution (objective like in the sense that we can measure it) or not. I do not expect a full answer here as you people will probably make an excellent video about it. A quick yes or no would be enough.

Thank you for your great work

Massless particles and energy waves are dull-images of the same energy. A particle can convert to a wave and back and forth, at will, when it encounters another field or particle - this is new science for many people... And so when energy is traveling in S-T at speed (C) and there are no external fields acting upon it, it appears as a particle, but when that same energy encounters an external field, it converts instantaneously to a wave field. This explains what happens in the double-slit experiment and also it explains what happened when a particle encounters an atom... Within the atom resonance, the particle converts to a wave field and couples to one or more electron resonance cavities around that atom. Regardless of the speed of the ship, it can always accelerate, because the speed of the reaction of mass converting to energy, is un-effected by the speed of the ship. QED

Hello Dialect Channel, Thanks for your excellent Maverick RU-vid videos! I really like this critical and analytic approach which is much needed in the standing astrophysics and cosmology. IMO: The human time conception refers in general to motions, and we have all kinds of not linear motions in the observable Universe, hence time (and light) is cyclical in nature, and subsequently, a concrete “time-conception” does not exist at all, hence the Universe is eternal and containing eternal cyclical formations and motions = No Big Bang. Then you specifically mention the challenge of explaining watches going differently and faster in space compared to on the Earth. I don´t believe in a general “gravitational time-dilation”, and if forced to deal with the “clock-problem”, I initially would focus on the different atmospheric densities and electromagnetic conditions on the Earth and up in the Sky. I don´t even believe in the attached theory of “gravitational frame dragging increasing distances” between celestial objects. (Where the human concept of “universal time” really is stretched equally in this increasing distances). In my firm conviction, our Solar System was once formed by the attractive electromagnetically force working on a cosmic plasmatic fluent cloud in the early Milky Way formation and slung away from the Milky Way center, a motion which is confirmed by the observation of the galactic rotation curve. When focusing on the barred Milky Way structure, there is no way an assumed attracting gravity could make an abrupt 90 degree turn form the Milky Way arms and into the barred structure. It´s logically the other way around, hence no “dark matter” is needed at all. This initial outgoing centrifugal motion is still mirrored in the increasing distances between celestial objects in the Solar System. Thanks again and Best Wishes

It's fun that RU-vid in some limited fields of thought, like this, has become a venue for the democratization of ideas. I don't understand the math well enough to evaluate your presentation or those of Fermilab, or Sabine, or PBS Spacetime et al. But the fact that you're flinging ideas about at a level physicists themselves don't understand and making those concepts accessible to people like me is laudable and wondrous. Thanks! :)

Have you ever considered, Idunno, reading an actual physics book? Nobody learns physics from youtube videos.

Somehow I have become confused about whether I am confused and it feels hella funky. Let's take this slow. 1) So acceleration causes a gradient in time dilation from the point-of-view of the accelerating observer. This seems like an extremely big deal with some ontological teeth, but 2) Acceleration is not absolute and so, therefore, has no ontological teeth whatsoever. That means we are going to have to back out of our previous teethy intuition. So, lets try to figure why it seemed so important. Well, its because I can commit an action in my frame that then requires different corrections by different observers who are, relative to each other, still and therefore do not require any corrections between them. So Sally who I observe to be at point A in the gradient has to make a correction of say 2X. Jan who I observe to be a further away point B in the gradient has to make a correction of 3X. Yet, at the same moment, I also observe that Sally has to make no correction to agree with Jan. From the girls perspectives, Sally could send a radio signal to Jan that contained both Sally's corrections and a beeping sound at a pre-agreed frequency. Jan receives the corrections and verifies that the beep has no Doppler shift. Thus she assumes that she and Jan share the same frame of reference. Thus she has to make no corrections to agree with Sally. Thus she accepts Sallies corrections as her own. Now how can this fact jive with what I originally calculated from my perspective? Well, as I think about it, it only needs to have some jive at the moment I pass both Sally and Jan respectively. Yet, I believe (because I consider myself accelerating) that I will be in a very different frame of reference when I make the two crosses. So whatever mechanism I used to check Sally's correction will now itself be dialiated different relative to Jan. That means that I could perceive Jan to have made the wrong correction. And, I need to perceive that because Jan did not follow the set correction that I originally said she should. But, why isn't Jan surprised when her corrections fail. Well, she only knows she shouldn't have to correct Alice, so she concludes that Alice made the mistake. Now is there some way that I could signal to Jan that Sally's corrections passed. It seems there should be. I could for example hold up a sphere with one hemisphere black and the other white. If Alice passed the black side will oriented towards the fore of my ship. If she failed the aft my ship. Even though I am in a different frame of reference there shouldn't be a way that objects within my ship change their orientation relative to each other along the axis I am traveling. So it seems I have by accelerating created some sort of asymmetry among observers all of whom considered me to be accelerating. This very much seems like an absolute change because the disagreement is not over whether two events occurred at the same time or not; or in the same place or not; but whether they occurred at all or not. Either Sally made a mistake or she did not and Jan and I disagree about that.

I have 2 clocks together and synced. I move them apart in a completely mirror image of each other and then bring them to rest at a distance, again, in a mirror image way, and they both stop running and show their final values i.e. all accelerations, decelerations and constant velocities happen at exactly the same time and for the same duration in opposite directions. Relativity says one must be slower and the other advanced - but which one is which? From the frame of reference of the starting point, both dilated identically and are thus still perfectly synced? From the frame of reference of either clock however, the other clock is slower? ?

You said that accelaration is not the solution of twin paradox then you didn't make video on the solution of twin paradox.what is the real solution of twin paradox?

I really appreciate for what you did. Thank you so much. But I have a question, agreed those famous youtubers don't understand it, what is the guarantee we have that you understand it?

The physical change is absolute. When a particle accelerates and it changes at the same time (throw some propellant or radiation away) there is physical interaction and change which cannot see relatively in some frame that no change happened. When there is no physical change in the body but it seem to accelerate, it's all about fictitious acceleration - that's a situation when a body is falling free or you choose some inertial correction coordinates...

I've posted this as a reply to someone, but I thought I would want to bring this to Dialect's attention (at the possible cost of being redundant) regarding acceleration being relative or absolute. Doesn't the notion of Rindler horizons necessarily prevent any relativization of acceleration in SR? In SR, if you had two observers uniformly accelerating in one direction, oriented so that one is in the front and one behind, when they bounce a photon between each other (in the longitudinal direction), my understanding is that there is a point where if they were far apart enough or had enough proper acceleration, the photon would no longer be able to reach the guy in front. This doesn't happen if they were at constant velocity. Doesn't this kill off the possibility of relative acceleration (at least for rectilinear motion)? I'd be happy to be disproven or shown wrong, but I would appreciate any feedback on this point. (It's possible GR or some other theory says something different on the matter, but I want to handle this one specific point.)

Could the sponsors of the Dialect channel please say something about their background and credentials? I had a college physics course covering relativity, though that was not my major. It went over the Lorentz transformation and the derivation of E=mc2. I had been able to do OK on the exam problems, but years afterward, I increasingly realized that there is a difference between mechanically cranking through some equations, and really understanding what it means. It seems like even physicists do not fully understand or agree on the question, "What is this telling us about reality?" Eg., "Does the past still exist?" I have not been able to shake the suspicion that while special and general relativity may be mathematically correct, giving answers that match observations in certain situations, that it might nonetheless be in a category somewhat akin to a "bookkeeping accounting trick". The real reason for not understanding relativity is that it is a crazy, distorted funhouse of mirrors. What is not to understand about our lack of understanding?

When I saw the part and sabine's video that said "acceleration is absolute", I immediately thought of this channel! Anyway, it seems to me that the reason for so much confusion is that RU-vidrs go too far to dumb down explanations because they believe "us rubes" can't understand anything more complex, But personally, the whole reason I watch (and rewatch) so much physics on RU-vid is try to stretch my understanding. I do realize that without a formal physics background and being able to do the math I probably will never fundamentally understand what's behind the curtain, but sometimes I like to think the math is just how we communicate with each other about science...reality knows no math, so maybe anybody can know at least just a little bit about reality (said in Zach Braff Scrubs Episode-ending monologue rap-up voice😅)

Acceleration does cause time dilation, it's just that the amount of time dilation will depend on the distance the twin travels. It's like saying that dropping an apple causes it being crashed on the ground. The height will influence "how crashed" the apple will be but it's the "dropping" that is the cause. Acceleration is the cause, the traveled distance is a parameter. Without realizing it, you transformed a physical problem into a semantic one. Saying "cause time dilation" is not the same "is the only parameter of how much time dilation we get". @08:10 The satellite won't see all clocks ticking at the same rate because a gravitational field decreases its pull over distance (the farthest clock from the mass is less attracted by the mass than the closest ones).

You are wrong; absolute acceleration does exist. The starting point of General relativity is the "principle of equivalence", which states that in a small enough volume, an accelerated reference frame is indistinguishable from gravity. This is generalized to the statement that there is a preferred set of reference frames, the "freely falling" reference frames, in which the laws of physics take the same form. Conversely, the laws of physics can look different in reference frames that are not "freely falling"; e.g. reference frames that are accelerating.

I'm really grateful to you and your videos because you helped me to understand what awful teachers at university weren't able to. But, honestly, these recent videos, that I think ridicule and make fun of other channels (whether they are right or not) are making the love I have always felt for your amazing content fade away a little. It's really ok to debunk misconceptions and I think it can be done in an elegant way

I think @SabineHossenfelder is correct on absoluteness of acceleration and if Einstein was allegedly confused about this, that was his problem! 😅 I wish she responds to this and also the science Click guy.

Free fall observers, seeing clocks at stationary positions. Their position isn't changing over time, they are still near where they emitted a signal (relatively near anyway, there are logs of velocities involved that make us non-stationary), the the falling observer will see the same clocks +/- a little delay as they move past them, but the fast clocks will still be faster than the slow clocks (even though they're approaching slow clocks, and seeing their ticks faster until they pass that clock). The test for clock dilation using airplanes, one flying east and one flying west to counter the earths rotation worked too - they both had the same lack of gravity field so they ticked a little faster, but then they were still in that field and therefore accelerating, so it doesn't really matter that they are following the curve of the earth and are 'accelerating' sort of like satellites which have a velocity (the net velocity of us all is much greater than anything man can make at 300km/s relative to the CMBR).

A very very bold title, to be honest. And we aren't taught relativity from short RU-vid videos. I say we, because like you say so yourself as well it's misguided trying to truly and properly understand relativity from youtube videos. Everyone would also only learn the basics. And they garanteed lead to (stubborn) misconceptions.

I'd love to hear what YT contributors like Sabina, Nick Lucid, PBS Spacetime et al make of Dialect's take on their videos re relativity. We never hear from them about it.

You’ve clearly taken criticism from past videos into account and made an attempt to improve. However, you still opt to call out other RU-vidrs directly, even if you frame it as constructive criticism, and I think it would be better to instead restate the argument yourself and debunk that instead of debunking someone else’s video. Also, I don’t think it’s fair to claim someone’s interpretation is wrong without posing an alternative. I’m sure you have an interpretation in mind, and I’m looking forward to that video, but it really should have been included here. Without it, this comes off a bit more like an attack than constructive criticism. I’m glad you’re incorporating feedback to improve your videos, and I look forward to seeing you improve more in the future

What I'm trying to understand: when an object is under time dilation (observed from the outside by an observer) let's say considerable time dilation, is it interactions that slow down or objective time that slows down. In other words, interactions slow down but otherwise the particles under dilation get older by the same amount as particles not under dilation or the particles under dilation do not get as old? i.e. protons under dilations will fall apart just as often or would they last longer? Will proton decay happen at the same rate for protons under dilation or not?

6:45 I think she was comparing coordinate time with proper time. No one has to carry the clock that shows the coordinate time, but everyone's clock shows their proper time. So coordinate time dilation is just a mathematical statement, proper time dilation is a physical thing. Coordinate time is a type of coordinate that can be used to causally order events, but values of coordinate time are not necessarily physical. On the other hand, the value of proper time is physical and directly shows what your clock shows.