Special Relativity: This Is Why You Misunderstand It

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Күн бұрын

Try out my quantum mechanics course (and many others on math and science) on Brilliant using the link brilliant.org/sabine. You can get started for free, and the first 200 will get 20% off the annual premium subscription.
Does time really slow down when you move? What about gravitational fields? What's the resolution to the twin paradox and what's up with Newton's bucket. In this video, I tell you how it really works.
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00:00 Intro
00:34 Space+Time = Spacetime
04:30 Proper Time
07:59 Time Dilation
10:21 The Twin Paradox
13:59 Newton's Bucket
15:25 Time Slows Down Near Black Holes
19:30 Learn More on Brilliant
#physics

Пікірлер: 6 100

@MrVasile Жыл бұрын

I always learn something from Dr. Sabine. Today one of the things I learned is that in Germany they teach the Pythagoras Theorem in kindergarten!

@angellestat2730 Жыл бұрын

I would not be surprise if she is the one who learn that when she was in kindergarten :)

@KwieKokosnuss Жыл бұрын

From her view the math and physics of your school time are kindergarten basics. ;-)

@garysevenofnine Жыл бұрын

I came here to write this and saw you beat me to it. 😆

@janami-dharmam Жыл бұрын

but I now have no questions that answers; I am confused!

@jmaniere Жыл бұрын

Otherwise Sabine's "special" humor ...

@mcwolfbeast Жыл бұрын

Definitely a great, condensed description that is a lot less confusing and allowed me to grasp a few fundamental principles that eluded me so far because they were never explained to me in relation to each other. Thank you, Sabine!

@jovetj Жыл бұрын

Ha! I see what you did there...

@stoyanfurdzhev Жыл бұрын

You deserved your like

@ix12 Жыл бұрын

@@jovetj what did s/he do there? :) I feel like I'm missing smth :)

@jovetj Жыл бұрын

@@ix12 Raving about the "condensed" description of things very small (e.g. light)

@TheReaverOfDarkness Жыл бұрын

I think your teaching style is great. I always understand things way better after watching your videos than anywhere else. And part of that is because on some of these topics, you're one of the few sources who actually seems to understand the subject in the first place.

@w0tch Жыл бұрын

Yeah exactly, the sad truth is that she is among the few who actually deeply understand these stuff

@geoffreymilward3293 Жыл бұрын

What I particularly liked was your distinction between proper time and co-ordinate time. Thank you. It's really helped me understand geodesics in GR in a much more geometric way.

@stylis666 Жыл бұрын

Indeed. That was always confusing to me and this was like having all the puzzle pieces that still didn't make a picture just shoved in place in one move by Sabine and boom: picture :D And I was like, ooooooooh, well that explains a lot :D Somehow instead of being all abstract and shizzle Sabine ties it to the actual universe making it all far more practical and real and way easier to understand.

@iurlc 5 ай бұрын

Are you sure you understand really what she is telling with this diagram and 45° light for speed of light and the hyperbolic curves? @3:40 45° for speed of light is an error. When something move with the speed of light, the time stand still. There is no choose for an other angle than 0° to the right in the diagram. Think about the light clock which explain special relativity. If the one you look at is standing still relative to you, the light in his light clock jumps up and down. When he accelerate, you will see the light beam of his clock get diagonal and the clock ticks slower. If he gets (which is not real possible) speed of light, the light beam will move horizontal with him and the clock stand still. No ageing!!! The explanation of the twin paradox is not correct. Make the twin paradox with 3 twins symmetrically! One is moving to the left, one is moving to the right and on remains on earth. Due to the complete symmetrically situation, the moving twins must see each other younger! And the one remain on earth will see both a little younger. Why should it not possible to see each other younger? There is an issue with seeing the other older. Imagine they are real single egg twins (same gender, same look like). If one of the twins see after the journey the other twin older, than he can see into the future. He will see e.g. if he is 20 years after the other return from flight, how he will look like when he is e.g. 40 years like his returning twin. And this should not possible. If you draw your diagram correct, you will see, that there is no possibility, that they can come to the same time coordinate. So there is always a time difference between them, and if you draw the diagrams for both you will see that the other one is always back in time - so the other one is always younger. Her acceleration story is also wrong. Imagine an endless train station and an endless train. In each cabin of the train is a light clock you can see also from outside. And at the train station in same distance like the cabins are also light clocks. When standing still all light clocks are synchronized (have the same number of counts on the displays). Both the one on train station and the one in the train see the same time. Now the train accelerate. The one in the train see train light clock with normal speed, but with increasing speed the light clocks at the train station ticks slower. The one at the train station see clock from the train station with normal speed but the clock in the train ticks slower. And when the train decelerate the one in the train see the clocks at the train station become faster until they have the normal speed when the train stops. And the one on the train station see the clocks in the train become faster until they have the normal speed when the train stops. But for the one in the train the clocks at the station have less ticks count. For the one at the station the clocks in the train have less ticks count. There is no difference caused by acceleration, if the acceleration is 1g. And at the way back the same happens. So both see each other younger!!!! And even when you take in account length contraction. There is now way, that in this example the clock from one ticks faster then from the other one. And finally - if you think the traveling one see the earth one older - what does it mean? It means, that from the view of the traveling one (his clocks tick from his view normal) that the clocks from the earth one have speed up. But which formula on physics show speeding up clocks? If traveling speed e.g. is 0.5c and as long you accelerate with values man did not die, you can neglect the influence of acceleration cause by general relativity. I like her videos - but this one was simply retelling wrong stories, which are based on a lot of tiny wrong assumptions - starting with the wrong diagram, where traveling with speed of light is 45° (or other) instead of 0° to the right in her example.

@treeinthewood Жыл бұрын

Things I learned from this video: 1. Einstein obliterated the Minkowski bobblehead industry; 2. Physicists' humor doesn't exceed 45°; 3. Newton was concerned with buckets; 4. Flat earthers aren't entirely wrong; 5. Climbing a mountain can accelerate aging. Taking a selfie near a black hole can promote longevity, though.

@enforced9550 Жыл бұрын

I have never came across the concept of hyperbolic distance we use on the space time diagram before, and that it gives us the proper time passed, absolutely stunning and well explained!

@zekicay Жыл бұрын

The most interesting thing to me with this proper time is that all particles moving at the speed of light experience no time - their proper time is always zero.

@franklittle8124 Жыл бұрын

@@zekicay Yes. A photon is everywhere on its path through the universe at once, from its perspective.

@Tore_Lund Жыл бұрын

@@franklittle8124 -or formulated differently: the Universe has no length and no time passes from the photon is created until it interacts with an electron at the other side of the Universe zero distance away.

@SandipChitale Жыл бұрын

I think the pronounced hyperbolic appearance is because of the choice of 45-degree convention Sabine talks about. If the true proportions were uses between time and space axis the hyperbolas will still be asymptotically hyperbolic but for all practical purposes straight lines near x axis. That will also clarify as to why the photon travelling at the speed of light goes to infinity in no time and thus does not experience it as the elapsed time for its journey is zero. And for same reason photon does not experience the distance as the space gets shortened to zero in its direction of travel.

@stoyanfurdzhev Жыл бұрын

@@zekicay Great!

@ryancraig2795 Жыл бұрын

I never got as far as relativistic physics in university, but about 30 years ago I read Roger Penrose's "The Emperor's New Mind" which did a pretty good job of explaining these concepts, and more. This was a great refresher - very easy to follow.

@kwimms Жыл бұрын

Yeah, I read that story too.

@stylis666 Жыл бұрын

That is so cool! I think that Dr. Penrose is a very insightful and kind man. And I think that he and I would both agree that Sabine is the better physicist because she is as brilliant but has a giant head start because of the work of people like Penrose. He had a lot less to work with, taking him a lot more time to get where Sabine pretty much started from. But anyway, that's not why I commented. Do you know what the title of that book is referring too?

@hieronymusholt-xj2rg Жыл бұрын

Should be an endash: -

@BillGreenAZ Жыл бұрын

I read that book 30 years ago and it's one of my favorite books that I've read in the past 30 years. I should read it again.

@kwimms Жыл бұрын

Douglas Hofstadter had some great books around the same time dealing with more computing science rather than the laymanistic fairy tale put out by Penrose and his 'pal' Hawking. Sabine is an actor, btw. Pop!

@daviddavis-vanatta1017 Жыл бұрын

Dear Dr. Hossenfelder: First, I really like your YT videos. They take some fresh looks at things that I've read before, and even if one of them doesn't answer all my questions and struggles with a topic (some of this actually IS difficult stuff!), each one adds to my understanding, gives some new perspectives, helps raise a different set of questions, etc. So, thank you for these lesson videos. Somewhat incredible to me how the Twin Paradox has produced a century of discussion and debate, and to this day without universal agreement. There are presentations of it that say, as clearly, simply, forcefully, and every bit as certainly that the explanation, or resolution, of the (apparent) paradox requires NO treatment of acceleration whatsoever to explain the real effect of differential aging. Those explanations often require accepting and using the (special) relativistic phenomenon of length contraction, and its effects. One thing is sure, and something not always made clear, while acceleration may (or, to me, may not) be required to resolve the paradox, General Relativity has no place in describing this paradox, and absolutely is not needed for a full resolution of it. One can indeed "totally describe" acceleration within the conceptual theory and the mathematics of special relativity, alone. But acceleration as the correct resolution seems to be not so categorical. Some accept and use it, successfully, and others disagree that the required acceleration is the correct explanation. These latter treatments, the ones that are focused on acceleration as the causal explanation, also seem to use time dilation effects to explain the resolution of the apparent aging paradox. While those that eschew acceleration as the central, causal explanation tend to use length contraction effects. Given that time dilation and length contraction are really one in the same, two sides of one coin, "mirror" effects of each other, etc., I suspect that both resolutions, that is, both those claiming that the causal effects for differential aging are inherent in the acceleration periods, and those who equally say that no treatment whatsoever of the acceleration periods is required to resolve the paradox, are probably both accurate in their thinking and equally in full accord with SR. As wonderful as this lesson is to consider, excellent things in it to absorb, I don't think I can see how it is that some treatment of the three acceleration periods on this journey, provides the sought-after answer here, that is, it is the accelerations that provides the conceptually correct explanation for the differential aging effects found in this experiment that resolve the apparent paradox of the differential aging. For a good write-up that takes the position that “the acceleration incurred by the traveling twin is incidental and the paradox can be fully resolved” without it, see Scientific American, “A Matter of Time,” March, 2012, by Ronald C. Lasky (Dartmouth). A final important fact to note: this apparent paradox is not just theoretical. Its basic tenets have been very well-tested in any number of experimental settings, including ones involving precise clocks and co-relative travel. Without exception, these have confirmed many times, using various setups, that the seemingly paradoxical differential aging effect is both altogether real, all the experiments end with the two clocks no longer having the same time, and that they differ precisely as special relativity says they should.

@alonamaloh Жыл бұрын

I must have read the same incomprehensible books 30 years ago. I ended up becoming a mathematician and I never formally studied Relativity. This is far, far better. Thank you!

@hyperduality2838 Жыл бұрын

GRAVITATION is equivalent or dual (isomorphic) to ACCELERATION -- Einstein's happiest thought, the principle of equivalence or duality! Space is dual to time -- Einstein. Time dilation is dual to length contraction -- Einstein, special relativity. The Twin paradox is duality -- which twin is actually moving? Questions are dual to answers. Points are dual to lines -- the principle of duality in geometry. Space, length, distance is defined by two dual points -- space duality. The future is dual to the past -- time duality. We predict (syntropy) the future and remember the past. Absolute time (Galileo) is dual to relative time (Einstein) -- time duality. My absolute time is your relative time and your absolute time is my relative time -- time duality. If time is dual them space must be dual. Time duality is dual to space duality. Duality within duality! "Always two there are" -- Yoda.

@bsadewitz Жыл бұрын

It is astonishingly simple, yet profoundly counterintuitive. I actually had already understood most of what was in this video. To do this, (I think!) you just consider time as another dimension. It doesn't even matter whether it actually is or not (whatever that even means). I thought of it like this: a helicopter has three degrees of freedom it can move in--the three dimensions. Now, just presume that everything actually moves at the speed of light. Add a fourth dimension. Now, think of the helicopter: any motion in one of the three spatial dimensions is motion that is not happening any of the other dimensions--including the temporal dimension. Now, its speed in three dimensions is the sum of its speed moving in each of the spatial dimensions. Now, as everything moves at the speed of light, its motion in the fourth dimension is the speed of light minus however fast it is moving in the fourth dimension. Light, therefore, does not move in the fourth dimension at all, and the faster you go in the three spatial dimensions, the slower you will go in the fourth dimension. Gravity is the curvature of space-time itself, and this changes the "distance" one must travel to get between two points in a given amount of time. That is gravitational time dilation. Of course, without the math this is just a fanciful narrative. It does not even get us to a testable hypothesis. If I could do that, I'd be a physicist. ;-)

@bsadewitz Жыл бұрын

@@hyperduality2838 Equivalence is not duality. The two concepts are orthogonal.

@hyperduality2838 Жыл бұрын

@@bsadewitz Orthogonality, perpendicularity = duality. Duality:- two equivalent descriptions of the same thing -- Leonard Susskind, physicist. Are you saying Einstein & Susskind are idiots? Equivalence, similarity = duality! Wave are equivalent or dual to particles -- quantum duality. In physics you learn to generalize everything -- abstraction.

@bsadewitz Жыл бұрын

@@hyperduality2838 I didn't even call you an idiot, so why would I be calling Suskind an idiot? What I'm saying is that the equivalence principle simply is not what you seem to be implying it is (?) It refers to the equivalence of gravitational and inertial mass. Look, I've been down this road before. William James wrote in his treatise on the subjective effects of nitrous oxide: "There is a reconciliation ! Reconciliation ^conciliation ! By God, how that hurts ! By God, how it does n t hurt ! Reconciliation of two extremes. By George, nothing but othmg ! That sounds like nonsense, but it is pure 0#sense ! Thought deeper than speech ! Medical school; divinity school, school! SCHOOL! Oh my God, oh God, oh God ! The most coherent and articulate sentence which came was this : - There are no differences but differences of degree between different degrees of difference and no difference." This reminds me of what you're saying now. James concluded that, "the togetherness of things in a com mon world, the law of sharing, of which I have said so much, may, when perceived, engender a very powerful emotion ; that Hegel was so unusually susceptible to this emotion throughout his life that its gratification became his supreme end, and made him tolerably unscrupulous as to the means he employed; that indifferentism is the true outcome of every view of the world which makes infinity and continuity to be its essence, and that pessimistic or optimistic attitudes pertain to the mere accidental subjectivity of the moment; finally, that the identification of contradictories, so far from being the self-developing process which Hegel supposes, is really a self-consuming process, pass ing from the less to the more abstract, and terminating either in a laugh at the ultimate nothingness, or in a mood of vertiginous amazement at a meaningless infinity." ia802305.us.archive.org/31/items/thewilltobelieve00jameuoft/thewilltobelieve00jameuoft.pdf

@brilliantcosmicspeck7956 Жыл бұрын

Love your descriptions Sabine. You explain things very well. I have been sending your videos to my mom who, for some reason, is convinced she cannot understand science. Your videos are proving her notion wrong and she is getting interested in science. We now have something additional to talk about. Thank you Sabine !!

@stoyanfurdzhev Жыл бұрын

I bet your mom is a very religious person.

@ewanholmes4559 Жыл бұрын

I mean my mum is similar and she's not religious at all

@lucashouse9117 Жыл бұрын

@@stoyanfurdzhev most older people are just not interested in learning new things. Religion doesn't have much to do with it.

@andoletube Жыл бұрын

@@stoyanfurdzhev stupid comment

@robertnull Жыл бұрын

Cool story, though I bet special relativity will still prove to be too hard a topic to digest for her :)

@Dismythed Жыл бұрын

This was the best video I have seen on the subject. So many people get caught up on the "move away from earth" diagram that they miss that it is about acceleration, not direction. Even slowing down is acceleration and the direction of movement does not matter is what so many science communicators fail to understand or fail to explain to their audience. Thanks, Sabine.

@stewiesaidthat Жыл бұрын

What most people don't understand is that acceleration and deceleration forces DECREASE lifespan. That's why motors and engines are run at a constant speed. It's why passengers/cargo is strapped to the vehicle's frame. So that the vehicle endures the forces, not the passengers. Only at constant velocity, 0 gravity, does lifespan increase. This is all well documented in engineering. Why is physics still stuck in the 18th century?

@LowellBoggs Жыл бұрын

Thank you so much for this video. This is my second watch and you explained several concepts that other videos have muddied up. I'll watch again in a few weeks.

@jamesduncan6729 Жыл бұрын

Sabine's videos contain the most accurate and concise summations of these kinds of topics and I absolutely love it ❤️

@eonasjohn Жыл бұрын

Yes.

@chriskennedy2846 Жыл бұрын

Many of Sabine’s science videos are very informative and provide a great public service to non-scientists looking to better understand confusing topics such as: quantum theory or nuclear fusion. Unfortunately, we will not be able to add this relativity video to her list of shining examples. It is riddled with erroneous statements and also relies on a convoluted explanation that will appear to be complete gobbledygook to a non-scientist seeking a better understanding of relativity and the twin paradox. She even contends that you don’t need gravity or general relativity to solve the twin paradox. Einstein’s official explanation for the twin paradox was published in 1918 (titled: Dialog about objections against the theory of relativity) and broke down comparative time dilation events between stationary and traveling twins into 5 steps: 1) initial acceleration away from Earth 2) constant (inertial) velocity away from Earth after acceleration to desired speed 3) slowing, turning around and reaccelerating to head back toward Earth 4) constant (inertial) velocity toward Earth 5) slowing down and coming to a complete stop back on Earth. Contrary to what Sabine claims in this video, Einstein explained that step 3) was responsible for resolving the paradox because a “gravitational field” appeared due to the fact that the traveler experienced an acceleration that was equivalent to gravity. (This is known as the Principle of Equivalence and was published by Einstein in 1911.) This was mentioned by Sabine with her elevator example toward the end of this video as she (correctly) showed that a person in an elevator being pulled up (by the elevator) would feel their feet pressing against the floor and it would be indistinguishable from being in a motionless elevator on the surface of the Earth. Einstein contends that since at the step 3) turnaround, the traveling twin would be in a lower position of the induced gravitational field, the traveler would experience an additional slowing of clock time that the Earth twin would not experience and this would explain how the traveling twin would have aged less than the Earth twin upon reunification at the end of the Journey. If you are not familiar with Einstein’s 1911 Equivalence paper, please seek it out and read it or find Richard Feynman’s explanation using light pulses in The Feynman Lecture on Physics series (which you can find for free online). Once you have a good grasp of how the elevator explanation justifies the difference in clock times by comparing the frequency shift of light signals (or time intervals of light pulses) you will see how this doesn’t apply to Einstein’s 1918 example. This turned out to be a big problem for Einstein. There is nothing (to my knowledge) in the historical record about the reason for the physics community’s endorsement of the Einstein 1918 explanation while Einstein was alive and then later, the quiet shift toward replacing that resolution with the “space-time” diagram example which is now everywhere, including in this video. It’s possible that enough smart scientists spotted the error that Einstein made in the attempted resolution of his own theory and replaced it with the “space-time” diagram. By the way - the official resolution used by most spacetime diagrams these days is to completely remove acceleration from the example by having triplets instead of twins. The triplet traveling away from Earth simply transfers her clock time to the third triplet traveling the same velocity (from farther out) toward Earth. The exact moment when their paths cross - the outward triplet will transfer her clock time to the Earthbound triplet and continue the simulated non-accelerating journey. I will give the community credit. Although this explanation is also a complete work of fiction and is science at its almost worst, at least (unlike Einstein 1918) it is self-consistent, so the community will get as much mileage out of this explanation until more people realize that actual time dilation experienced in the GPS clock system (which is a very real phenomenon that I do not dispute) shows that neither Einstein 1918 or space-time 2023 have no basis in reality.

@YbisZX Жыл бұрын

I don't think so. If "acceleration causes time-dialation", you may think that total dialation of time depends on the periods of acceleration. But it is wrong. Bob can accelerate in the same short periods (hours) and travels for years with constant velocity - resulting time dialation will depend on time and speed of the main part of the journey. Changing the frame of reference (acceleration) may be the cause of the start of the time-dialation, but amount of dialation depends on total path.

@NoNameAtAll2 Жыл бұрын

please add uncertainty values

@SheanHoxie Жыл бұрын

It’s cause she gets rid of the gobbledygook 😂

@ChuckHenebry Жыл бұрын

Those books you and I read 30 years ago were written in a style designed to maximize the reader's sense of wonder, because wonder (and a dash of incomprehension) is what sold books. What I love about your videos, Sabine, is that you never stoop to that cheap rhetorical trick. You're here to give us understanding, not gobbledygook.

@SirBlot Жыл бұрын

Maybe I had a better book than ppl on here.

@croozerdog Жыл бұрын

These days it's articles like "The universe isn't real" People flip out, not their fault really, these articles don't care to explain what "real" means in science and that it isn't the same as a philosophical or social real haha

@Nat-oj2uc Жыл бұрын

Huh what a nonsense. There was no conspiracy or any agenda. First of all maybe you're not smart enough to understand those books. Secondly being taught simplified explanation so you could think you got it isn't the same as actually getting it. And the most important thing is those books were written many years ago and there was not enough time to simplify it to your liking. You think she would be able to explain it that way if there was no previous knowledge she built her understanding on?

@johnt.inscrutable1545 Жыл бұрын

This was so entertaining and elucidating as well. Sadly, what it elucidated for me was how little I fully understand these ideas. Though intuitively they seem to makes sense. Thank you, JTI

@robertgoss4842 Жыл бұрын

Dr. Hossenfelder: Your videos are among the best learning tools I have ever come across. I'm no physicist, but I think I have a pretty good layman's understanding of the theory of special relativity (far less so of the general theory). This video greatly helped me further grasp the special theory. Thank you for your many careful, and comprehensible, programs

@jandobbelsteen8953 Жыл бұрын

Nice video! That reminds me: in 2005, the Dutch astrophysicist Vincent Icke published a simple book: "Niks relatief, De speciale relativiteitstheorie zonder formules", which translates to "Nothing relative, Special Relativity without Formulas". It takes him only 70 pages to completely explain in layman's terms what it is all about. The nice thing about the book is, that if you flip it upside down and start reading from the back, you will have a book "Nothing Relative, Special Relativity WITH Formulas". This side only takes 63 pages. I'm sorry, I think it's never been translated into other languages than Dutch, but if you're German, you might be able to read it and understand it (according to a German colleague, you might have to read out loud).

@richsadowsky8580 Жыл бұрын

"Moves just left or right, like American politics maybe..." Sabine, I love the humor you inject into your explainer videos. Long time subscriber here

@fannyalbi9040 Жыл бұрын

“no absolute rest” even in cemetery 😢

@franklittle8124 Жыл бұрын

Except that it is more like moves between center and off-the-scale right - with the center governments never quite reversing the damage done by the other.

@saimon174666 Жыл бұрын

I've seen so many explanations about twin paradox, but this is hands down the best, thanks!

@stylis666 Жыл бұрын

And the simplest. She just tells you what happens and why we see what we see. The graphs show me exactly why I didn't understand any of it when other people explained it. And Sabine is like, Bob accelerates and that's what matters. And I was like, ooooooh, well that could've save me 50 hours of lectures that made no sense to me.

@MrCmon113 10 ай бұрын

@@stylis666 That "acceleration" is absolute should be extremely alarming. That means acceleration isn't just the second time derivative of position. It's fundamental. And it looks exactly like gravity. Why?

@dexter8705 9 ай бұрын

Thank you Sabine this qas a great video, nobody teaches inertial and non inertial frames better than you do. Love ya work

@alex.pozgaj Жыл бұрын

Wonderful! I saw 1000 videos about these topics already, and I thought to have quite a solid understanding of it sll, but this video really made it all fall into place! "Acceleration is not relative" is so important, but I don't think I ever heard it before.

@HowardS185 Жыл бұрын

ditto here, and I have a BS and MS in physics!

@snack711 Жыл бұрын

what i dont understand is how you define absolute acceleration without gravity. but maybe im missing the point.

@HowardS185 Жыл бұрын

@@snack711 If you were in an area of free space, far from any sources of gravity, and someone turned on your rocket engine, you would feel the acceleration. This would happen regardless of your initial motion.

@cazcam2000 Жыл бұрын

@@HowardS185 That's because of "Inertia". Inertia opposes a change in motion.

@TheHesseJames Жыл бұрын

@@c4pt4ina69 It is relative. You could indeed put it like that. You also could say that when on Earth, sitting at your desk you are constantly accelerating at 1 g. It would be equal to sitting in a spaceship accelerating at 1 g.

@auseryt Жыл бұрын

This makes so many videos about space time and general relativity SO MUCH clearer! Especially the part between minute 8 and 10.

@pluto9000 Жыл бұрын

Why is there 3 hyperbaly?

@auseryt Жыл бұрын

@@pluto9000 you mean the three hyperbolic lines? Along such a line all events are at the same proper time according to the length metric of space time.

@auseryt Жыл бұрын

@Balungi Francis can you add anything useful or is spam your only way to communicate?

@stoyanfurdzhev Жыл бұрын

Otherwise everything is cristal clear.

@samirsaha2163 Жыл бұрын

Simple and beautiful, Sabine! Many thanks!!

@GrimmSpector Жыл бұрын

Excellent, I agree it's one of the hardest concepts I have explaining to folks, and sometimes I do it poorly. Have to hang on to the link to this one!

@itfrombit Жыл бұрын

Wow, what a great video! A frustrating one too, because everytime I believe I know something, you come around with another video and I am reminded of the simple fact that I got it wrong - until now. And I have been thinking about these things for several decades. Sabine is the best science communicator in existence - period. Not making a topic more complicated than necessary, but - most importantly - not making it any easier. I salute you!

@yesthatsam Жыл бұрын

It’s clearly the best way to explain it I’ve encountered in over 30 years of interest on the subject. Especially because you presented both special and general relativities, and used each time the same examples (paradoxes, spring, …), that helped so much. I hope there is an award for physics vulgarisation because this video would win it hands down. Thank you very much for this exceptional clarity.

@hyperduality2838 Жыл бұрын

@berniv7375 Жыл бұрын

There is not an award for the vulgarisation of physics I am glad to say but there should be an award for the popularisation of physics.

@RWin-fp5jn Жыл бұрын

Agree, but is also exceptionally wrong. Imagine 100 years of stagnation and confusion amongst top physicists on what they all agree is rather 'basic' theory. You should also watch her colleague Don Lincoln's (Fermilab) explanation of SR on youtube contradicting directly what Sabine claims. It is speed and not acceleration that matters. And he is right! The issue here is that Einstein claims speed is not absolute. But it is in the case of SR! So even Einstein got it wrong. Notice Albert speaks of time 'dilation' (since when do we use a term like that in physics?) and 'length' contraction, as if an object becomes detached from spacetime and shrinks in length all by it selve? Bitte Bitte Herr Einstein und Fraulein Sabine; let's call it for what it is; Speed contracts frontal spacetime. Period! If you speed you have less frontal space (hence appear shrunk) and less frontal time (hence your clock ticks slower). Speed impacts the grid itself!. Goes for macro object (this is what SR is all about) and it goes for the tiny unaligned subatomic particles making top restmass, given the appearance of radial ST contraction around restmass. GR describes that geometry wise. I say hats off to academia to for keeping us in the dark for 100 years, but it is time we start teaching the obvious truth now. Sabine can do way better then this!

@richardhussong7232 Жыл бұрын

@@RWin-fp5jn - Lincoln and Hassenfelder do not contradict one another in any way. Because special relativity is quite counter-intuitive, you cannot expect to understand it by thinking about it in everyday terms. The only way to truly understand it is to do the math. Fortunately, special relativity in one spatial dimension can mostly be done using only high-school algebra, so it is reasonably accessible to most people. The thing to keep in mind is this: if you can't correctly solve the problems in a relativity textbook, then you don't understand relativity at all!

@RWin-fp5jn Жыл бұрын

@@richardhussong7232 Dicky, before adding a comment, I suggest you actually look up youtube and see Don Lincoln explain the twin paradox of special relativity. He sums it up; Anyone who suggests that acceleration determines which twin experiences time dilation does NOT understand special relativity. So if Sabine says it does, then both are NOT in agreement (unless `woke' speech determines contradiction = agreement). But Don is right, if even for the wrong explanation. It is about speed, because the speeding twin physically CHANGES its frontal grid, whilst the static twin does not. This is also the deeper reason behind gravity. It is no wonder we failed to understand gravity for 100 years. Even Einstein got it horribly wrong as far as the fundament under SR is concerned.

@pedromalafayabaptista3655 Жыл бұрын

Thank you for the enlightenments you provide, Dr.

@SAMACAG Жыл бұрын

Sabine has not done her homework. Please watch: Common Sense Einstein Super Star

@LesCish Жыл бұрын

I'd never seen an explanation of the twin paradox that made sense to me. Until now. Thank you!

@BradleyLayton Жыл бұрын

Agreed, I've been puzzling over that twin's paradox for years. I'll have to go back and do the vector calculus and look at how the answer comes out of the acceleration.

@SAMACAG Жыл бұрын

Sabine has not done her homework. Please watch: Common Sense Einstein Super Star

@markpmar0356 Жыл бұрын

I would say that this explanation of the twins paradox, hyperbolic curves in spacetime, and the difference between co-ordinate time and proper time is the best I've seen so far. I can understand the difference between "e equals m c squared" and "e equals gamma m c squared" more fully now and you've done this with fewer words and fewer diagrams as well. Even the math portion is accessible. So, thumbs-up from this viewer. The key, finally, is to more fully grasp the difference between acceleration and the gravitational effect.

@stevecreighton3352 Жыл бұрын

Sabine, you explain things with a clarity that only someone who completely understands the subject can do.

@onetruekeeper Жыл бұрын

I don't think she undestands the mistakes in Special Relativity Theory. She has her degree so why should she care whether or not us uneducated people understand it ?

@davidbarnett.2313 Жыл бұрын

Ah yes! Like all learning, you have to work the concepts until you understand them. If this discussion does not make intuitive sense, we have Brilliant to help you in your quest. Just a few US dollars please.

@Watchyn_Yarwood Жыл бұрын

So very true.

@johnjohnson7070 Жыл бұрын

Yes. This was absolutely much clearer - and understandable - than "those" books. Thanks for that.

@SAMACAG Жыл бұрын

Sabine has not done her homework. Please watch: Common Sense Einstein Super Star

@Brandon-rc9vp Жыл бұрын

Best quick and clean explanation on KZfaq for twin paradox, great job Sabine!

@luudest Жыл бұрын

11:10 thanks for the info about the difference between speed and velocity. Always thought it is the same.

@KaiHenningsen Жыл бұрын

Simplistically, Velocity is like speed combined with direction. It's the difference between "you're driving at X km/h (or mph)" and "you're driving from A-city to B-city at X km/h (or mph)".

@davidpnewton Жыл бұрын

Then you've always misunderstood badly. Speed is a scalar quantity. It has only magnitude. Velocity is a vector quantity. It has both magnitude and direction.

@luudest Жыл бұрын

@@davidpnewton this!

@erinm9445 Жыл бұрын

@@davidpnewton This response is rude. Clearly they get it now, and don't need it re-explained. Your response and editorializing adds nothing.

@stoyanfurdzhev Жыл бұрын

No, your are a fool all the same.

@Taomantom Жыл бұрын

I had to digest the last section twice. That was an exceptionally well stated point of view. And my universal understanding of space/time acceleration is enhanced. The working in on the curvature influence helped! Thank you for all you do. Missed you Wednesday.

@MarvinMonroe Жыл бұрын

Digest twice? That means you had to swallow it again after you had already eaten and digested it. Really gross

@user-uj9cc5ch5p 2 ай бұрын

Always give me something to thing to think about Sabine. I really enjoy your videos. Mr. X

@paulmccaffrey2985 Жыл бұрын

Mind Blown! I've been told many times that time dilation was as a result of acceleration, but it was never explained to me. Now I get it! Thank you Dr. Sabine.

@schmetterling4477 Жыл бұрын

Acceleration is required. There is no way to leave and to later come back without changing velocity, hence acceleration. It's just not the correct explanation for the size of the effect.

@erikafein4353 11 ай бұрын

@@schmetterling4477 Acceleration is not required if the world is a hypersphere and Bob makes the round trip :)

@schmetterling4477 11 ай бұрын

@@erikafein4353 That's one big if. ;-)

@wardieleppan8443 Жыл бұрын

Love her videos! Just got her book Existential Physics just before Christmas. A great read. A few chapters I had to read twice because I’m a pea brain but can highly recommend it. Not to be missed!!

@jaim3_mm Жыл бұрын

As always that was an amazing experience, thanks for your work Sabine

@morenofranco9235 Жыл бұрын

Kerist! Sabine! This sounds like learning calculus at my father's desk. He was fun about everything EXCEPT math. That is when the beating and ear twisting started. I NEVER failed math at school. Failure=Pain. And today, 60 years later... I UNDERSTAND EXACTLY, what relationship you are describing. I love you.

@RichardAuber Жыл бұрын

Thank you, Dr. That was the clearest explanation yet and the humor and irony were charming.

@SAMACAG Жыл бұрын

Sabine has not done her homework. Please watch: Common Sense Einstein Super Star

@CleverNeologism Жыл бұрын

The "proper" in "proper time" does not mean "correct" or "appropriate"... in this case, "proper" takes on a slightly archaic meaning in English: "belonging to itself". In other words, "proper time" literally means "the time belonging to the object in question", or "it's own time", and is exactly that.

@kylelochlann5053 Жыл бұрын

Correct. You get a thumbs up. But keep in mind that this eigen-time is physical time.

@carcharhinus_555 Жыл бұрын

Oh my god, this was *so much* better than most of the books! It's a comprehensible explanation for anybody with a bit of understanding of maths. Ok, it requires the "leap of faith" in the maths in the beginning, but it answers a lot of questions answers to which are surprisingly hard to find, on which others used hundreds of pages and didn't come close. Immediately bookmarked for the next time someone is curious. Honestly: this is *really* good - or at least it applies very well to my type 🙂

@DrWhom Жыл бұрын

too bad

@BruteZ7957 Жыл бұрын

Same

@fkeyvan Жыл бұрын

Her explanation is incorrect. But she says with a lot of confidence

@BruteZ7957 Жыл бұрын

@@fkeyvan how so

@fkeyvan Жыл бұрын

@@BruteZ7957 because she says that Alice is at rest because there are no forces on her. And that Alice’s proper time is therefore not the longest. But that’s only true from Alice’s frame. Not from Bob’s. From Bob’s rest frame Alice is moving. According to Bob , Alice moves away turns around and returns. Therefore according to Bob , Alice has the longer proper time and Bob measures Alice’s clock ticking less. I think the mistake Sabine makes is considering all motion from Alice’s frame only. In other words she considers Alice’s frame as absolute rest

@stevejorgensen1105 8 ай бұрын

By far, the clearest explanation that I’ve encountered and the first one that I ever thought I had understood afterward.

@mnada72 8 ай бұрын

That is insightful explanation. Yet I have to watch it several times to feel comfort about it 😊. Thank you.

@etienne8576 Жыл бұрын

“as we learned in kindergarten” 😂 That’s why you are so clever Sabine. I wish I attended the same kindergarten!😂

@pumbaa667 Жыл бұрын

That was crystal clear ! One of the best explanation I saw on this topic.

@samiehessi8163 Жыл бұрын

Thank you. You explained all the key points about this concept. I thought I've understood it until seeing this :)

@SAMACAG Жыл бұрын

Sabine has not done her homework. Please watch: Common Sense Einstein Super Star

@richardneifeld7797 Жыл бұрын

Books and videos are only as insightful as the clarity of knowledge and thinking of the presenter. This on is spot on. Thank you for distinguishing gravity and acceleration!

@VelvetCondoms Жыл бұрын

I think this was a lot more helpful than the books that I read when I was younger, because at least where I live, mechanical physics and relativistic physics are taught completely separately and they usually just abstract away the Nuance of acceleration rather than velocity for the purposes of special and general relativity. By bridging them, you made this make a lot more sense.

@hyperduality2838 Жыл бұрын

@imid-ltd Жыл бұрын

Thank you for this remarkable clarification. I've been frustrated by assumptions about my personal motivations, but can see how an oversight in proper time can lead to the continuation of an error in coordinate time. So when an observer takes a judgmental position because the consequences of an oversight are severe, then it's corrected without apprehension whether we're aware of it or not.

@winstonsolipsist1741 Жыл бұрын

I have some special relatives that I constantly misunderstand.

@urick4321 8 ай бұрын

Absolutely Fascinating! Back in the 90s I read "Einsteins Universe" by Nigel Calder, and it was interesting, but I came away a little confused. Your video has brought me closer to understanding relativity. Thank you! You are amazing!

@LP6_yt Жыл бұрын

Excellent video. There have been a number of poor/inaccurate explanations of this by some otherwise decent KZfaqrs in recent years. This one hits the mark.

@stoyanfurdzhev Жыл бұрын

A like from Sabine.

@vasilyp Жыл бұрын

Excellent way to explain time dilation! Thank you! and as always with the appropriate humor and attitude 😉

@sdsa007 Жыл бұрын

very good… i learned a lot! Thank you for your insight! Very good specific, concise refutations of popular ideas that are completely wrong!

@w0tch Жыл бұрын

Thanks so much for clarifying this, so much videos I watched that just confused me before this 😅 I would love an explanation if there is any on what actually happens during acceleration that makes proper time run slower.

@tomschmidt381 Жыл бұрын

I really like these videos about time. Casually time seems like such a simple concept yet the deeper one examinees it the more nonintuitive it becomes. I liked the way you explained frames of reference, I thought I understood it but your example crystalized it for me.

@KaiHenningsen Жыл бұрын

The real problem is that all these effects only become noticeable at significant speeds. Since we evolved without ever having interactions with similar speeds, our intuition about the world doesn't include these effects. It is much easier to learn about something that doesn't flat-out contradict our intuitions. Quantum mechanics has similar problems for the same reason. (And failing this kind of leap is what causes flat-earthers, for example.)

@tomtoups Жыл бұрын

WOW! I've watched a lot of videos on this topic, but this is the only one that has explained it so clearly. I've learned so much. She can make a complex idea accessible without having to use grossly incomplete analogies and metaphors.

@tomtoups Жыл бұрын

@Savage samm thanks 👍

@timesquare5473 Жыл бұрын

@Savage samm Lets not . 🤡

@SAMACAG Жыл бұрын

Sabine has not done her homework. Please watch: Common Sense Einstein Super Star

@pontuslandgren7997 Жыл бұрын

Awesome explanation of acceleration causing time dialation, never understood it before 😊

@lingarajpatnaik6514 5 ай бұрын

Amazing and brave! I thought I noticed SR misrepresented in text and popular books. After looking at this video I shall have to revisit my books and rework. Great teacher! A gift!

@thepeff Жыл бұрын

Great analogy for path-dependence in four dimension, great video as always

@alorcalderon279 Жыл бұрын

As good as it gets for this difficult subject. Thank you! I’ll still look for absolute rest no matter what the physics says about it.

@gstlb 3 ай бұрын

“As we learned in kindergarten.” I have to quit watching these as I’m drinking my morning coffee 😂

@alanoneill4058 9 ай бұрын

This is only about the second time I've been moved to comment online about anything. This is great!

@ffggddss Жыл бұрын

As a grad student 50 yr ago, when MTW* was new, and Prof. Misner was teaching us relativity using that book, I'm glad to see both SR & GR being "properly" presented. Praise for Sabine, and for John Archibald Wheeler's vision of the topic! Mainly for recognizing that the use of a theory rests on top of a basic understanding of the underlying, important concepts. Which you have conveyed beautifully! Fred * MTW = _Gravitation,_ by Misner, Thorne, and Wheeler, IMHO a ground-breaking treatment of special & general relativity

@bobjones7908 Жыл бұрын

Kip signed my copy around 1990, and he added "don't believe everything you read here". I think Taylor was the one who really emphasized you don't need GR for acceleration, but it is buried in MTW.

@ffggddss Жыл бұрын

@@bobjones7908 Edwin Taylor, of "Spacetime Physics" by Taylor & Wheeler, 1963/66? A friend of mine had that as a textbook in an undergrad course at U.Md. Anyway, I didn't think it was "buried" in MTW; I recall a bit of material about Rindler coordinates from there, e.g., and "how to outrun a light ray" (by constant acceleration, a, starting with a "lead" of c²/a), both in flat spacetime, i.e., SR. Which, BTW, demonstrates that in a constantly accelerating frame, there's a "horizon!"

@daviddavis-vanatta1017 Жыл бұрын

100% agree about the excellent, superb job Taylor & Wheeler ("Spacetime Physics") does in explaining relativistic physics, at least to me. I struggled with my undergrad tests on it until I just gave up. Much later in life I found Taylor & Wheeler. Fabulous! If only I could have had that for my UG intro to relativity text, like @ffggddss's friend at U. Md. *sigh* But at least I eventually found that book! I'll go back to look at their treatment of the resolution to the Twin (seeming) Paradox. I think it's a bit different from the one shown here.

@ed.puckett Жыл бұрын

Thank you for making this so clear. As you usually do.

@stoyanfurdzhev Жыл бұрын

I like it.

@georgeluke6382 Жыл бұрын

Thank you so much for this!

@russellcastagnaro72 Жыл бұрын

Thank you! This was really great

@gshort4707 Жыл бұрын

Fantastic summary of relativity, especially Newton's bucket. I hadn't heard of that one before, but for a long time I've wondered about the relativity of spinning objects. Great explanation, easy to understand. Thank you.

@damianlukowski9996 Жыл бұрын

I'm not satisfied with the bucket. Is spin absolute or not?

@gshort4707 Жыл бұрын

@@damianlukowski9996 when an object is spinning then each point in the object is constantly changing direction. A change of direction is an acceleration towards the new direction. Acceleration is absolute. Even in an otherwise empty universe with nothing else to compare with and no frames of reference you would still be able to measure acceleration. That is how I understand it.

@damianlukowski9996 Жыл бұрын

@@gshort4707 How do you distinguish a spinning and non-spinning bucket in an empty universe? If both is possible, the universes must differ in more than the shape of water, because both shapes should have a cause.

@fredflickinger643 Жыл бұрын

Thanks Sabine, although I learned that I had a good grasp on Special Relativity, I couldn't have explained it and connected all together so well!

@hyperduality2838 Жыл бұрын

@morenofranco9235 Жыл бұрын

Sabine. All things are relative. My relatives are things. My relatives took all my things. And I love your work.

@SAMACAG Жыл бұрын

Sabine has not done her homework. Please watch: Common Sense Einstein Super Star

@whilewecan 4 ай бұрын

Thank you. Understood well. Appreciated.

@pesilaratnayake162 Жыл бұрын

Great explanation, Sabine. Tied together a lot of loose ends in my understanding. I hadn't heard of Newton's Bucket, though, so that's a new concept for me. I guess it's another way to detect acceleration, although it seems more restrictive than the spring, since an acceleration would be necessary to have an even surface for the water in the first place. Maybe a fluid sphere, held in shape by pneumatic pistons that change their applied force as the fluid exerts a force on the sphere. Springs sound a lot simpler!

@davidparker2173 Жыл бұрын

Didn't grasp much, but did acquire a sore brain, proving I did attend the subject. Amazing I am able to come to some grasp of these topics if I attend them enough. Provides good exercise if nothing else. Appreciate your humor.

@vibaj16 Жыл бұрын

Vsauce's video "Which way is down?" provides a less in-depth, yet easier to understand explanation of some parts of relativity. It's the first video that made me finally understand how gravity isn't a force, and that freefall is actually not acceleration.

@johnburke568 Жыл бұрын

There is a good Witten lecture on maximizing proper time on YT. This helped me orient more to try and understand his talk better. Thanks.

@stefanleichsenring6891 Жыл бұрын

Very good explanation, thx.

@eonasjohn Жыл бұрын

Thank you for the video.

@mina_en_suiza Жыл бұрын

I also had the "Einstein for beginners" book (the German version), but I had the same problem with it as with most popular science books: They went to great length to explain the easy parts very well, but once it gets complicated, they rush through it. This is the frustrating part of 99% of all popular science books: Great at explaining what you already know or can easily understand, but a total loss when getting to the real stuff. This video was actually great, but I don't know how helpful it would have been to my younger self. I can't judge, because it actually didn't tell me anything really new. When my kids are a bit older (and know English), they're gonna be my test subjects.

@MmmhMarky Жыл бұрын

In college, there was a science textbook that did the same thing. It went into detail like a few pages explaining simple stuffs, but when the hard stuffs appear, it rushed over it.

@dennisbrown5313 Жыл бұрын

LOL - so true in all physic course, even higher level ones.

@mina_en_suiza Жыл бұрын

@@dennisbrown5313 In mathematics, we cleverly write: "The proof of the following steps is left as exercise to the reader."

@renedekker9806 Жыл бұрын

Part of the reason for that might also be that it is easier to understand stuff you already know... 😉 That is, the point where the science book gets difficult differ between different people.

@mina_en_suiza Жыл бұрын

@@renedekker9806 Sure. However, I really noticed a repeating pattern: People putting much less effort in explaining the tough stuff well than the easy parts. I understand the reason: It's easy to explain what you yourself really and truly understand. It gets hard if you approach your own limits. That's one of the things, I really appreciate from Sabine: She never pretends that particle physics or general relativity are dead easy, but she makes it less intimidating.

@WorldwidePeace2all Жыл бұрын

Thank you so much for this excellent video Dr. Hossenfelder! You explained time dilation due to acceleration through spacetime and due to gravity, which is not a force but the absence of one, which is also the result of acceleration so well and so concisely! You made it very simple to understand! Far better than the books I've read! And I love your sense of humour, your hilarious jokes made me lol! Thank you so much for these great free videos, they are a great service to the public, you have become a professor to the people of the World! Please keep making your excellent videos! Take care! Much love! And to anyone reading this I wish you peace and love! World Peace and Unity!!! Science is Real! Science is the study of reality and of the truth! Everyone must learn the truth and stop believing in lies!!!

@briancrowther3272 Жыл бұрын

DR Sabine, this is fascinating. i took physics at Sheffield uni 1976-79, along with geology and physical geography. I ended up after being a petroleum geologist, a science teacher at high school junior science, & pre uni physics and earth science, in Sydney Australia. I’m now 65 and what I’m trying to say is I have done this all my life. I found special relativity really hard to understand at uni and keep revisiting to understand it better and better. We didn’t get to general relativity on my course. One nice thing Eistien said that helped me feel better was we are not designed to see in 4 D and even he does not fully see it, it just knows the maths works. I think I am good at physics because I see how things move (I was tested in this and go off the bell curve for the general population in that trait, hence the geology as well) and then have just enough maths ability to back that up, even if I don't have great teachers (had 5 maths teachers in my last 2 years, ie the pre uni course, at school, and as a teacher I now realise that is like poison to learning). Like you when a kid at school my kids loved relativity in the New South Wales Course. The resources to teach it got better and better with the advent of the web. So, my understanding got better. Brian Cox's shows got me into trying to understand general relativity and his co-authored book, "Why e= m c squared?" is just fantastic for all this. In that book I realised like you say gravity is not a force. So cool. When my boss retired the school did not honour him after 40yrs science teaching so I did it by making a social do and raised money for a gift to present at the associated dinner. He got fly fishing wading boots. But I didn't tell him. I did a talk about entropy (based on Brian Cox's show) and what is happening in that regard, happening in the universe while we are at the dinner ie the arrow of time can only move forward so as to obey Maxwell’s 2nd law of thermodynamics (entropy always increases). Then I got a cuckoo clock and placed it in a cardboard box and made out this was the gift from the staff. I presented this to the boss as such calling it "an entropy machine". Then to the Principal of the school I informed him re general relativity that this machine does not work on the force of gravity it is a result of the earth curving space time and that time runs slower closer to the Earth's surface, this gives the acceleration which we feel as a force of gravity, ie the ground pushing up.. Thank you for this. It helps, I'll have to re watch it a few times and dovetail that with what’s locked away in my old brain cells, dredging that up to synthesise and once again attempt to understand it better. Being evolved to grab the low hanging fruit in 3D is a pain when attempting to see in 4D. I think that our atoms being organised in such a way to allow us to able to do this is the miracle. This is one of life’s pleasures and I feel so lucky to be in a position to do this. Despite a life time of doing physics, you have relieved me of one important misconception, relativity is for constant velocity and general for acceleration. Thankyou.

@schmetterling4477 Жыл бұрын

So now that we have heard your irrelevant life story, is there anything of importance that you would like to contribute? ;-)

@barryon8706 Жыл бұрын

Thank you, Sabine! And your wonderful staff, Alice and Bob. They don't get enough credit for the good they've done in physics and cryptography.

@human_shaped Жыл бұрын

Alice and Bob are probably due for an honorary joint Nobel prize by now.

@pixelfairy Жыл бұрын

Will bob ever get the message? Will Eve foil her plans again?

@axle.australian.patriot Жыл бұрын

IKR! Alice and Bob are going to start competing with Albert. "Yes, those guys again" lol

@hyperduality2838 Жыл бұрын

@axle.australian.patriot Жыл бұрын

@@hyperduality2838 So any thoughts on how we solve this paradox? Or like me, I am attempting to accept the paradox as part of the ultimate truth of the universe and write that into my view of the physics?

@dubberj2847 Жыл бұрын

I will need to watch this a few more times to properly understand all of the concepts. However I would say this is one of the best and most concise explanations of Special relatively that I have watched. Especially the explanation of the mathematics and diagrams that describe Spacetime. Sabine makes the mathematics very simple to understand.

@aupotter2584 Жыл бұрын

@@nemlehetkurvopica2454 On the contrary, I disagree w the explanation of Twin paradox based on Lorentz transformation alone, as velocity is relative and Sabine has clearly pointed out that both Alice and Bob will get older at the same time which makes no sense at all, though I still dunno why acceleration causes time dilation as told by Sabine, or earlier by one of my Physics professors, because I also think that acceleration is relative as well, just thinking of centripetal force and the centrifugal force relative to the rotating frame of reference...

@Kycilak Жыл бұрын

@@aupotter2584 Centrifugal force is exactly the consequence of acceleration being not relative. Let me demonstrate: Imagine you have 2 people - First and Second - in space and Second is on a carousel. When the carousel is not spinning, both are in a weightless state and at rest relative to each other. Now consider the carousel spinning. When looking from outside we can clearly see that carousel acts on Second in its seat because if it didn't second would not go round but instead would go straight. This force that acts on him that makes him go round is called centripetal force. From the view of Second the whole world is spinning, so you conclude that he may think that everything is rotating around. But he can feel the seat of the carousel acting on his bottom with the centripetal force. He may not see himself rotating (instead everything else is) but even though he should be at rest (according to his eyes) he knows there is a force acting upon him. So we see that both First and Second agree who is the one that the force acts upon and since acceleration is proportional to force they both agree Second is being accelerated. Hence acceleration is not relative.

@aupotter2584 Жыл бұрын

@@Kycilak You've just shown to me that centripetal and centrifugal forces are relative: the First sees the carousel exerting an inward centripetal force on the Second to maintain the circular motion, while the Second sees the opposite as experiencing an outward centrifugal force. The acceleration is hence relative, pointing inward when viewed from the First's inertial frame at rest, and outward when viewed from the Second's rotating frame of reference.

@Kycilak Жыл бұрын

@@aupotter2584 If the forces were relative as is speed for example, Second would have to see a force acting upon First. But that is not the case, both know Second is being acted upon. And even from Second's view the force is acting inward. The seat of the carousel accelerates him towards the center of rotation from the view of both.

@aupotter2584 Жыл бұрын

@@Kycilak Good points, but carousel is something we used to play w so we always have 'mixed' feelings from both frames of reference... if we scale it up to our Earth, we won't recognize it spinning fast as viewed from outer space, but we do experience a weaker gravitational force due to the centrifugal force... moreover, rotating frame of reference is not an inertial frame, so we'll also observe a centripetal force acting on every star or galaxy appeared to be spinning around us.

@3kinformaticamanutencaoeve91 Жыл бұрын

Ms. Sabine is such person and chanel that the algorithm needs to indicate to everybody.

@EventHorizon618 Жыл бұрын

Great video as always. You mention the negative sign in the Lorentzian Distance is there "because it works". I think it is possible to use Einstein's (that man again) train thought experiment to show that (ct)² - x² = (ct')² - x'² and therefore determine that (ct)² - x² is invariant for all observers.

@JamesMcCaughan Жыл бұрын

The Ptolemaic system of the heavens was a mathematical construction that correctly tracked heavenly movements for 1400 years until Galileo discovered with his telescope that Venus had phases like that of the moon, which were not predicted by the system. This led, at first, to the replacement of the geocentric kinematical construction by a similar and simpler heliocentric construction of Copernicus, which gave phases to Venus. But in turn kinematical construction was replaced by dynamical nature with Newton’s law of gravity. There was a reason from nature, not the mathematics, why the sun should be at the centre of the solar system. With Newton the philosophy driving the physics switched from idealism, saving the appearances with prediction, to realism, explaining how nature behaved. Construction is like a scaffold enfolding a building. The scaffold touches the building, but the links holding the construction together do not reflect how the building is. Relativity is a construction. By starting with reference frames it is homocentric. It begins with the mind by choice of frames and not with nature; it remains a mental exercise by working with the links of the construction. Nature does not require a reference frame to do what it does; nature does not require Special Relativity. The twin paradox was solved by George Darwin using light Doppler shift. We have two ways of doing physics: Ideal physics or observer based physics and Real Physics or physics of the observed. The philosophy driving the physics determines the type of questions that can be put to nature and the way they can be answered. In answering life’s biggest questions through physics in Dr Hossenfelder’s latest book "Existential Physics", the philosophy driving her physics provides her answers. In her KZfaq channel presentation "Special Relativity: This is why You Misunderstand It," Dr Hossenfelder leaves us with five takeaways: 1. Acceleration is absolute. 2. The reason that time slows down is acceleration 3. Time dilation is a real effect and has been measured. 4. Special Relativity does describe acceleration, but only in flat space-time. General Relativity describes gravity in curved space-time. 5. Gravity is not a force, which is why being at rest with a surface of gravitating body requires an acceleration and that too slows down time. The role of acceleration is the critical element in four of the points. The twin paradox is solved through the asymmetry of the experiences of the twins. Although the acceleration at turn around of the travelling twin is identical to the acceleration of the stationary twin as seen by the travelling twin, nevertheless the travelling twin experiences the forces from that acceleration, but the stationary twin does not. The result is that, according to Dr Hossenfelder, the stationary twin reads coordinate time and the travelling twin a shorter proper time. This prediction has been entirely a mental process involving acceleration with the construction of Special Relativity (item 4). It uncovers a “phases of Venus” situation for the construction: I regret to say that item 2 is false in nature. That acceleration does not affect clocks has been experimentally verified at CERN in J. Bailey et al, “Measurement of relativistic time dilation for positive and negative muons in a circular orbit”, Nature 268 (1977) pp 301-305. The acceleration of the muons in the circular orbit was 10^18g, but the dilation of decay times was that of Special Relativity alone. Item 5 falls as well, but for a different reason. If gravity is not a force, then there is collateral damage to Newton’s laws of motion. Dr Hossenfelder bases her claim on the fact that one does not feel the force of gravity in free fall, but that is the exception for that force alone. Consider: 1. A spring stretched between two hands. 2. The same spring stretched by the same amount pulling a mass with acceleration across a smooth surface. 3. The same spring and mass hanging vertically at rest in a gravitational field, stretched by the same amount again. In the first case the spring, obeying Hooke’s law, is extended by two equal and opposite forces, since the spring is at rest. In the second, the spring has to be extended to exert a force on the mass, but the spring requires two opposite forces at either end to be extended. These forces are not equal because the spring and mass have common acceleration. The force that the mass exerts on the spring is the real inertial force F identically= mg, where g is the acceleration. In the third, the spring is extended by the same amount as in the second, but spring and mass are at rest. The force that the mass exerts on the spring is its weight W= mg from Newton’s second law of motion. One can also write W identically= mg where g is now the strength of the gravitational field. The field is everywhere in the space surrounding the earth. Weight is defined as the force exerted by gravity on the mass. When one measures weight on a weighing machine, it is the normal force N from the machine platform that is measured, which yields the weight by keeping the mass at rest through W-N = 0 from Newton’s second law of motion. One is weightless when N disappears in free fall, but W continues. Exceptionally, one does not feel W in free fall as gravity applies to every last atom in the body, which does not produce internal strain, either as stretch if the external force pulls, or compression if the external force pushes. One feels the strain as real inertial forces. My apologies for spoiling your presentation, but it shows the power of accounting for observations through nature, where force is central, and not from mathematics of a theoretical construction. Lost in Math sums up the situation. "Real Physics vs Ideal Physics", near completion, has been developed over 26 years. My background is 50 years teaching undergraduate physics, mainly at the first and second year level, at the University of Sydney, finishing as a Senior Lecturer in 1999 and then Honorary Senior Lecturer till 2015. My research field was Cosmic Radiation (Extensive Air Showers using cloud chambers and image intensifiers) till 1991. For the sake of the future of physics we should talk or correspond. Yours sincerely, Dr James McCaughan

@anslicht4487 Жыл бұрын

Watching your videos from years back vs now (I binge on them repeatedly) it's interesting that your German accent with traces of British has become British with traces of German. Among all your other accomplishments, kudos on being ever more smoothly bilingual as well. I have none of your skills but do appreciate what you bring us (and so am a Patron).

@PedroGondalles Жыл бұрын

did you understand everything ?

@vinceturner3863 Жыл бұрын

Thanks Sabine, yes your explanations are better than a book.

@RWBHere Жыл бұрын

Thanks Sabine. This is the best explanation I've heard since first learning about this subject, too many decades ago. I'll be sharing this video. The responses should be interesting.

@fsmvda Жыл бұрын

You could have said that the reason for the 45 degrees being C is that is what you get when you set C = 1 by choosing time and distance units to get that and cancel it out of equations.

@JackPullen-Paradox Жыл бұрын

Or, you could determine that that would make a good graph of a cone, where a three dimensional cone would be (Δ x - h)² + (Δ y - k)² = (Δ z - m)²; so, a four dimensional cone would be (Δ x - h)² + (Δ y - k)² + (Δ z - m)² = (Δ t - n)². Or, eventually, Δ x² + Δ y² + Δ z² = c²Δ t². That leads to Δs² = -c²Δ t² + Δ x² + Δ y² + Δ z², because we want to include the interior as well as the surface of the cone. When² Δs² = 0, we are talking about the surface of the cone; when Δs² < 0 (Δs² is a notation convention, so it can be negative; it is really the differential), then we are talking about the inside of the cone; when Δs² > 0, then we are talking about the outside of the cone. All of these have physical meanings concerning the type of event. Light is represented as the surface of the cone; time-separated as the interior; space-separated as the exterior. The slope of the cone is c. If c = 1 then the slope corresponds to a 45 degree angle. So the 45 degree angle is a convention as you've indicated.

@McBobaa Жыл бұрын

I can't really say this video made things any clearer for me, I think it only made it more confusing 😆 I was lost as soon as you started talking about proper time. I appreciate the effort though.

@skwervin1 Жыл бұрын

I wish I had someone like you 40 years ago when I was learning physics in high school. Biology and chemistry I had no problems with but some parts of physics just melted my mind because my teacher just couldn't explain stuff and just told us to read the book. Back in those days we didn't have KZfaq or the internet.. I honestly think I could have gone further in physics if I'd had a half decent teacher. It also didn't help that in those days, girls were not encouraged to do higher level sciences or maths but then again I did always like proving people wrong!

@dancincoolkid Жыл бұрын

Prospective teacher here, hoping to do exactly what you wished a high school physics teacher did for you! I remember taking physics in high school and being equally as perplexed, and then after a degree in college (and with much accompanying, self-taught, grueling hours) things finally made some sort of sense! Hope I can translate that knowledge to other physics hopefuls 🤞

@CJ-gn8qm Жыл бұрын

How strange? I was the exact opposite at school. Physics made total sense to me and chemistry was hieroglyphics! Not surprisingly I went into engineering! Though for my degree I did have to catch up on the chemistry!

@SAMACAG Жыл бұрын

Would You be so kind, and look at these two Clips? Common Sense The Needle Common Senes Red Pinhead We would love your feedback ... :)

@SAMACAG Жыл бұрын

Sabine has not done her homework. Please watch: Common Sense Einstein Super Star

@shorthand1121 Жыл бұрын

This was REALLY good ... I learned Special Relativity in high school but we never touched it in my physics undergrad except waving hands at it for high energy particle physics ... but I never got this kind of clarity on the time paradox and always figured it simply had to do with the energy expended in acceleration ... never considering that you didn't need to either leave or arrive back with 0 relative velocity. (We just always assume second-order continuity b/c that's the world we live in.)

@ramonortiz7462 Жыл бұрын

Time is not a thing nor was time discovered!! Man invented time to SYNCHRONIZE from one moment to the next moment in the CONSTANT present!! Why don't they know what GRAVITY is ITSELF in ANY FUNDAMENTAL WAY??

@ytbit Жыл бұрын

Fun fact: the precision of atomic clocks is such that when a time laboratory moves its clocks to another floor (or even to a different height in a rack) they must calibrate for the change in gravitation.

@erinm9445 Жыл бұрын

Wow!

@thomasherrin6798 Жыл бұрын

.....change in their acceleration!?!

@franklittle8124 Жыл бұрын

Pretty impressive, I know that gravimeters used in geophysical field work can detect the change in gravity between a tabletop and floor, but to be able to detect the relativistic effect of that change is amazing.

@MiccaPhone Жыл бұрын

One could include acceleration sensors into each clock to self-re-calibtate each clock automatically. Wondering if this is already done.

@mikehalpin1385 Жыл бұрын

Question: If acceleration slows time, and if I was to build a centrifuge that could create say 1000 G's, and I put an atomic clock in it for delta t my time, would that clock undergo a time dilatation relative to outside the centrifuge? Thanks for all your videos, Mike H.

@Tore_Lund Жыл бұрын

Yes that clock would tick slower in respect to an outside observer or a clock closer to the center of the disk.

@legendzero6755 Жыл бұрын

This was better than old textbooks, thanks :)

@everettflores738 Жыл бұрын

Yes, I believe this has helped me better understand things.

@JayVal90 Жыл бұрын

Ok the distinction of coordinate time =/= proper time makes things super understandable. Also the fact that “path length” as measured by that hyperbolic distance formula is “perceived time on that path” and not some weird combination of the two helps. I’m curious what happens if you define c such that it’s at 90 degrees instead of 45 degrees in those spacetime diagrams. I know they’ll be less useful (maybe), but certain simplified things may make more sense.

@Anonymous-df8it Жыл бұрын

90 degrees would be covering infinite distance in zero time (relative to the observer)

@nenhard Жыл бұрын

Then you would have extra dt*dx component in formula for proper time

@Anonymous-df8it Жыл бұрын

@@nenhard ???

@nenhard Жыл бұрын

@@Anonymous-df8it Metric tensor in such coordinates would not be.diagonal.

@dynapb Жыл бұрын

I also wonder why they don't use 90 degrees for speed of light travel. To me it makes more sense on the graph because at the speed of light time stops so that would make it a horizontal line. Probably some math thing. Also if you could go faster than light the travel line would move to the negative quadrant and you would be going back in time. Makes more sense to me!

@dumbofliesvermont5684 Жыл бұрын

Thank you. Understanding the difference between proper time and coordinate time was an eye opener for me. I had always wondered how the traveler in the twin paradox could stay alive because "everything slows down." I expected chemical reaction rates to slow as well and so he would die due to lack of biological activity. Now I see that's laughable. Thank you again.

@lawrencedoliveiro9104 Жыл бұрын

What she calls “proper time” is what I learned to call “interval” (Lorentzian distance). The “interval” between two points on the path of the same light beam is always zero.

@MiccaPhone Жыл бұрын

He would rather die from the high g-forces. With low g-forces the time dilation would be too small to be visible to human perception.

@RagingGeekazoid Жыл бұрын

Death is a biological process, and that slows down too.

@Tom-sp3gy 8 күн бұрын

Sabine I think this is one of your best videos yet! Thanks for all the effort you are taking educating us all. You truly deserve more than just words of praise. I hope one day the physics community actually names an important science institution or department in your honor. At the very least, Germany should bestow on one of its finest daughters a medal of excellence.