The REAL Reason You Don't Understand Relativity

Think Relativity is confusing? Well, it's not just you -- even the experts can't seem to agree on its meaning, and often get basic facts about the formalism completely wrong. Here, we critique one such renowned professional who, in claiming to be clarifying the standardized theory of relativity, turns out to actually be promoting a misguided personal interpretation. What is this expert's confusion exactly, and why are such misconceptions so prevalent amongst the physics community?

Indeed, be cautious of posturers, gaslighters, stigmatizers, and Giordano-Bruno-burners who want to convince you that your inability to understand Relativity stems from your own deficient reasoning -- because when even the experts can't agree, you know there is something up...

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A link to minutephysics twin paradox video:
(Note that where minutephysics says that there are "gaps" in the accelerated observer's accounting for time, this is the phenomenon of accelerative time-contraction, i.e. where observers perceive gravitational fields/time speeding up.)

Some of Einstein's Relevant Papers:

His 1905 Special Relativity Paper:
His 1914 (not 1913) Paper "On the Relativity Problem":
His 1918 discussion of the Twin Paradox and the Gravity-based solution:
His 1920 lecture at the University of Leiden on the ether:

Contents:
00:00 - Intro
01:11 - The Many Interpretations of Relativity
04:55 - Examining Sabine's Interpretation, Pt. 1
08:30 - Examining Sabine's Interpretation, Pt. 2
10:58 - The Source of Confusion
12:12 - Are There Better Interpretations?

[lorigulfnoldor]

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

[alcyonae]

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

[sumofallnbs]

"... 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).

[TerryBollinger]

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.



(a PDF copy of this 2023-04-29 comment is available at sarxiv dot org slash apa)

[orthoplex]

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.

[lukasrafajpps]

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".

[BobAlexander-tg]

One random day, when I was in my early 60s, I watched an MIT lecture on YouTube 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.

[drh]

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.

[b.munster]

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.

[JohnDoe-suew]

This video is 90% chaff and 10% wheat.

[StrawEgg]

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.

[irrelevant_noob]

14:17 you're kind of missing the point here. She *_DIDN'T_* say "only" acceleration can cause TD, she's using that statement as a secondary premise to reach a conclusion. She had P1 A exists, and then merely added a correct statement that was useful to the syllogism: if A then TD. This doesn't mean A iff TD. You own unspoken comment that _many_ things "produce" TD does in fact mean that the statement as she wrote it was correct: it's just a shortened form of "A, like many other things, causes TD".

[philweight]

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?

[angeldude]

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.

[habouzhaboux]

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.

[auseryt]

There are some heavy misunderstanding and misrepresentation of what Sabine actually said.

Sadly it is too much to explain it here in the comments.

[AnyVideo]

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.

[A_GoogIe_User]

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.

[brainfreasel]

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.

[zemm]

I am confused at the end because there is no such thing as absolute acceleration as a postulate of relativity. GR only has 5 axioms (assuming it is impossible to derive the geodesic movement from the other 4). There is no mention of absolute acceleration and the only thing that could even approach that is the postulate number 4 which is that there is no acceleration in a free falling reference frame which can be easily shown to be equivalent to the geodesic assumption that Einstein used in his original work. Most Physicists including Einstein at first take this postulate at face value because it matches the straight line movement of Newtonian Mechanics and you can obtain it from an intuitive variational principle. Later on Einstein was upset not at "absolute acceleration" or anything of the sort but at the fact that he wanted to remove postulate 4 from the theory and obtain it as a theorem.