Relativity 101b: Introduction to Special Relativity

[@eigenchris]

I botched up the previous version of this video with mistakes. I'm hoping this video is mostly error-free. If you see any more problems, please let me know. Thanks to everyone who pointed out the problems with the previous version.

[@might_e]

So uuuuhhhhh, there be no description so I cant click the link you wanted to put in there on relativistic mass

[@eigenchris]

@@might_e Should be fixed now. Weird things happen when you edit videos in multiple browser tabs.

[@smartscience5305]

@@eigenchris I am 12 years old and I finished learning quantum mechanics,electromagnetic spectrum...... But I have a question sir, if the graviton boson really exist can it solve the string theory or loop quantum gravity, and can this boson complete the general relativity?????

[@eigenchris]

@@smartscience5305 Unfortunately I don't know anything about string theory or loop quantum gravity. You'll have to look somewhere else to learn those things.

[@smartscience5305]

@@eigenchris Even that thank you very much

[@screamindeacon]

THANK YOU!! I have always been interested in astronomy, and gravity has long fascinated me. A few years ago, I even did a "deep dive" into Special Relativity, and came to understand the basic math of SR. So, l have read or heard dozens of explanations about the speed of light being the same in all reference frames, and I understand why that creates time dilation and length contraction. Everyone starts with the same story about aether and the Michelson-Morley experiment. Yet, I have NEVER heard anyone speak to the reason *why* the speed of light is fixed. Nothing that I have encountered has made the connection between sound waves propograting through the atmosphere and light moving through a vacuum. No one has ever stated "the speed of light is fixed because there is nothing for it to measured relative too." That makes COMPLETE SENSE! SO THANK YOU for that little nugget to complete my understanding.

The relativity principle is not due to Einstein. It is Henri Poincaré's response to a Lorentz paper in 1904. By the way, your videos are very nice.

[@anmolmehrotra923]

That gravith example was so beautiful and intuitive. Thank you for sharing

[@hedgehog3180]

10:47 that disclaimer has to be one of the funniest disclaimers ever.

[@helmetongrass1893]

Not as funny as the one where he warned us about the muons not being as large as the earth

[@steveying1305]

this is such a well-explained video!!! U literally explained better than what my professor had been doing for a month

[@MRich955]

Awesome visual aids as usual, PUMPED to watch this again. Thanks :). One day I want to implement a little web app that allows you to "walk around" with relativistic effects, where c is set to some attainable speed, like 1 m/s. I think that would help me wrap my head around the calculations involved here.

[@Maltiez]

13:00 Strange, I was taught about the invariant mass (or just "mass"). And about the relativistic mass only as a historical reference.

[@MudahnyaFizik]

It should be taught as the rest mass and only as such. Some people (including practicing physicists) who argues that we cannot travel faster than light because we would be so massive. Some claimed that we would become a black hole, which is totally false.

[@alejrandom6592]

Man these videos are amazing! I thought I understood the basics of SR but you sir know how to explain it in a very simple way, I hope to learn not only the science but also from your way of teaching 😊

[@imaginingPhysics]

13:50 the same phenomenon happens in electrodynamics with repect to Electric force. There the magnetic field comes in just right to fix things. This suggests a quick fix for the relativistic gravity too: introduce gravitational "magnetic field" which, together with gravitational field obeys equations analogous to Maxwell equations. Now it turns out that this set of equations is not invariant under lorentz transformation. This Is because mass is not invariant whereas charge is. However this theory, called gravitoelectromagnetism, is approximately true and infact is (apart form a constant factor) equivalent to linearized version of GR. en.m.wikipedia.org/wiki/Gravitoelectromagnetism

[@imaginingPhysics]

Another note: not only are the masses closer to each other in the frame in which they are moving, but the masses also have more energy/momentum so they are heavier-->even greater atraction. So there is a double dilemma with the masses. With charges there is only the contraction issue, and it can be fixed introducing a magnetic field.

[@ammyvl1]

I like how you chose arrival of a train at la ciotat for the train

[@shahidmehmood9185]

Thanks for your lectures about relativity. Your lectures on tensors are also precise. Appreciating..Can you share pdf notes of Tensor calculus lectures? Thanks again.

[@samurai7474]

Very clear and easy to understand explanation.

[@punitsolanki5744]

qusetion - at 13:55 if we replace gravity with any other forces like tension, electromegnetic force the result will be same. I think the reason is that mass increases because of relativity, in a moving frame of reference and that why gravitational force increases.

[@eigenchris]

I don't fully understand your comment. For E&M, when electric forces change due to a change in reference frame, magnetic forces will also change to balance it out. So E&M is compatible with special relativity. This doesn't happen with gravity.

[@punitsolanki5744]

I just want to say if we connect the planets and the astronaut with springs. and there is a net force F and if we are looking at it from a moving frame of reference the net force should increase in this system due to lenght Contraction. and same thing is happening with gravity. I just don't understand that why the gravitational force increases. it's due to lenght Contraction or due to Relativistic Mass of planets and astronaut. And why special theory of relativity does not work in gravitational field. in leonardo susskind sir video they suggests that gravity is inconsistent with special relativity due to tidal forces. by the way your videos are so helpful.

[@punitsolanki5744]

do you understand what I want to say? 🙂

[@Manjeetkunwar7787]

Thank to your visual aid that help in understanding topic very easily.

[@lolerishype]

The slides are soooooo good :DD

[@SzTz100]

Excellent explanation, thank you.

[@rumplewang2814]

全網講的最清楚的相對論❤

[@n810h]

At 14:30, isn’t the same argument true for 5 electric charges, and the force being larger if we are in moving ref frame? Why does it work in that case for EM but not GR?

[@n810h]

OR is it related to Magnetic field that comes into play and makes things the same? I saw a comment below that references that

[@eigenchris]

It turns out that magnetic forces "save" us from any contradictions. Basically, when we change to the "moving frame", the increased charge density increases the electric force, but the fact that the charges are now moving creates a magnetic force that exactly cancels out the additional electric force. The final result is that all reference frames still agree on forces. I try to cover this in Relativity 103d. Some people theorized that there was a corresponding "gravito-magnetic" force for moving masses. And indeed, there are some effects like this in general relativity. I haven't investigated alternatives to GR much so I can't comment on non-GR resolutions to this problem.

[@n810h]

I see that makes sense. Thanks for reply! Amazing how EM works perfectly like that

[@jartsajartsa6230]

@@eigenchris Who said reference frames agree about forces? A weak electric field breaks a dipole, if said dipole moves fast enough through the E-field. The force exerted on the dipole is weak in the lab frame, strong in the dipole frame

[@alejandrolorenzogomez7683]

great video. You made it super clear

[@HuellBabineaux909]

Is there a clever example on lenghts contraction similar on what you said about time dilation?

[@hehen-t]

i may be mistaken, but doesn't the face that moving clock runs slow mean that time passed for a moving clock is less than time passed on a stationary clock? and well, from the given example, isn't tilde t - stationary clock (platform), t - moving clock (train)?

[@quilandbobdophysics3312]

Michelson-Morely didn't prove that the aether doesn't exist. It demonstrates only that, if it does exist, it wasn't detectable in these tests. That could be because the tests were insufficient, or that the aether doesn't act as predicted (for example, the aether could be fluid instead of fixed), or for any number of reasons.

[@atzuras]

well, it was an experiment designed to detect the aether as it was defined to be: a medium in which the light travels at speed 'c' but having also velocity 'v' relative to something. The result was v=0 thus making the aether useless for fixing the relativity problem of Maxwell equations. And because the idea of the aether was introduced exclusively to fix such problem, it was reckoned as a total failure. And belive it or not, Einstein never heard of such experiment when developing Relativity.

[@Igdrazil]

@@atzuras Einstein perfectly knew about Michelson experiment, of course and by many ways. One of them is that he aknoledge himself that he knew about Lorentz articles, where Lorentz of course talks about the Michelson Morley failure. Every physicist in Europe knew about that. Their World was very small with tiny communities of leading scientists. And information was very rapid crossing Europe in 2 or 3 days. Lorentz was World wide famous as the leading pure physicist and his work was known by all specialy in Germany World. Especialy in Zurich where Minkowski and Grossman were teaching. Moreover thé result was not "v=0", it was under thé limit at order v, than later when Morley joined Michelson to rafine the experiment to order v^2 it was still under the limit. And though Lorentz thaught that it light still hide under more subtile effects, it's Poincaré who put in 1898 an end to this endless game because he had understood since 1885 that the concept of aether was anecdotic in Hertz Theory. Then when Lorentz came with his revolutionary but party false and incomplète transformations in 1895, Poincaré immediately corrected them and exhibit their perfect form now days being thé Lorentz-Poincaré group. Einstein has nothing to do with Relativity, thé Theory was settled, achieved and perfect the 5 june 1905 by Poincaré who gave thé final important touch to Lorentz 1904 synthetic article. Moreover Poincaré applied thé achieved Theory of Relativity to Gravity in his 5 June and JULLY final article. He exhibit thé relativistic covariant GRAVITATIONAL Theory and predict GRAVITATIONAL WAVES. Relativity is 50% Lorentz and 50% Poincaré. Einstein came After thé battle and his article of september is full of mistakes playing with DEADFULL contradictions as using c+v and crap speeds of this kind to mess around with an empty and false "proof" of Lorentz Poincaré transformations that had been proved 7 years earlier by Lorentz and mainly Poincaré.

[@Igdrazil]

Exact ! Michelson found that the supposed draging effect was under expérimental prévision at order v. Than Morley joined him to push thé prévision to order v^2 and they couldn't watch any fringe shift. So they had to suppose that the draging was more subtile and maybe détectable at order v^3 or else. And it was Poincaré alone in 1898 who understood what was going on and that it was useless to waist more Time searching for such fantôme. He knew since 1885 that the concept of aether was obsolete by remarking in Hertz Theory of EM that this concept was in fact playing no essential rôle. Thus it was Poincaré who drove thé ship of science out of this trap by generalising the galilean Principle of Relativity to a Universal one for all Physics. Not only Mechanic but also EM, gravitation, etc. Einstein has nothing to do with all that' It is 100% Lorentz and mainly Poincaré brilliant work from 1885 to 1905 where he achieves the Theory to it's modern form the 5 june 1905. Moreover in this article and one last in july 1905 hé applies the achieved Theory of Relativity to GRAVITATION and exhibit thé relativistic covariant modification of gravitation, and predict GRAVITATIONAL WAVES traveling at the speed of light. But there has been a lot more experiments less known. A lot more on the aether quuest. Michelson continued searching with more and more previse interféromèter. Some others pushed forward. And After 1905 a lot of crucial experiments were done to verify the mass shift etc. Einstein has zéro effective contribution to Relativity contrary to mainsrtream Propaganda. The Theory of Relativity was achieved the 5 june 1905 by Poincaré in it's modern perfection with the Principles of Relativity, thé algorithm of clocks synchronisation, thé group of Lorentz-Poincaré... And the pathetic september article of Einstein that Everybody bow without Reading it is a scientific garbage ful of mistakes and leathal contradictions messing around with speeds of (c+v) or (c-v) in total contradiction of the Principle of Relativity and of light speed constancy. It sould never have been published in ANY scientific journal. Ever. It's a total garbage of crap science. But nobody reads it. Everybody suppose, prétend, believe, Hope, liké in a sect of brainwashed nerds. Its dramatic but true. So sad. Keswami has writen a brilliant article about Einstein leathal mistakes. But total silence in the World wide sect. Don't touch thé myth. Don't kill the vaudous icône...

[@benjaminfrank9294]

@@Igdrazil Poincaré has indeed played a huge role in Relativity but the Einstein article of 1905 set the speed of light to be constant for the first time in physics. The c+v and c-v is disturbing at first i agree but if you read the article carefully you will see it comes from the fact that the rod is moving : it is not the Galilean transformation. Einstein should have cited Poincaré and Lorentz but his article is still a good progress toward Relativity.

[@mpcformation9646]

@ You obviously don’t know what you are talking about. And so does E & Mileva when they consider c+v (in their 1905 forgery), in total contradiction with the principle of invariance of light speed they advocate in the beginning of their article, which implies that the light speed is a limit that cannot be overcome as Poincaré proves it and publish it in 1895-1900 (in several articles) while correcting Lorentz initial heavily erroneous « space-time » transformations. Thus writing c+v and similar crap is shear non-sens undoubtedly showing they don’t even understand what they are talking about. Not only they didn’t added a iota to Poincaré 20 years long (1885-1905) achievement of the theory of Relativity, but they made a shameful mess of it. So you can mess up all day with the facts you won’t change the Historic Truth.

[@michelmeunier9769]

Hello, First thanks again for your video. One thing I don't understand, is at 14:30 in your video, for me the density of the planet is growing but not is mass, so the result Fnet is the same. I make a mistake?? Thanks

[@michelmeunier9769]

Forget my question, it's because the planets are closer so gravity is more important. Nevertheless, thanks again for all your work.

[@MasterHigure]

0:30 None of Maxwell's equations say anything about forces. In particular, the first one doesn't say that like charges repel and opposite charges attract. By the way, very happy to see you avoid the Cardinal Sin of claiming that special relativity doesn't deal with acceleration. True, you didn't mention acceleration at all, but that's fine. As long as you don't claim it's outside the scope of SR.

[@eigenchris]

I guess you need to include the Lorentz force to get the full meaning.

[@Igdrazil]

Ahhh, so few but some, that alone saves the rest, do think, have solid basis and clear mind. Bravo ! I love your expression "CARDINAL SIN" that is perfect. Sin that Einstein had and never healed from, for the worse of brain screwed post-einstein generations that perpetuated this sin like brainwashed mormons of a sect. What a contrast with so many bullshit said, specialy on "Relativity". Refreshing

[@remisougnez2159]

Hi Chris, I assume you use LaTeX to write the equations in your videos. Which font style are you using? For example I'm unable to get such a pretty $v$ (the velocity vector at 2:35). Thanks!

[@eigenchris]

I use Microsoft Powerpoint to make my videos. It has an equation editor built-in in the "insert menu". It uses the Cambria Math font (plus italics option) by default, I think. You can either built equations with buttons or use LaTeX-style commands like \Gamma or v\vec to get various equation elements. Other Microsoft Office programs like Word and OneNote have this too.

[@HankGussman]

How many videos will there be in totality for Special & General relativity?

[@eigenchris]

6-7 videos for SR. No idea for GR.

[@canyadigit6274]

How would you derive length contraction formula?

[@eigenchris]

You'll get the video explaining that in July. The Fermilab channel and AK Lectures channel both have videos on it. My derivation in July will be a bit stranger, but I like it better personally.

[@imrem9673]

I like the muons 'proof' of special relativity but i have a problem with it. I understand that time is relative but the measurment of muins surviving their theoretical lifespan are 'real' the question what are we really measuring a shadow of a muon? In the frame of reference of the observer the muon is dead not? In his own frame the muons lives a little bit longer (or vice versa)

[@AbuSous2000PR]

u did well. u managed to distill a complex idea into simple language anyone can understand many thx

[@abcdef2069]

possible to cover this part? how has lorentz got his transformation? experimently? voigt wonderd and tried to find as to what transformation could be invariant for maxwell eqs, he got a different set of solutions, some said that voigt trans is also lorentz transformation in a different perspective. why wouldnt people try to find what transformation could be invariant for the maxwell eqs before einstein?

[@SuperDuperGuys]

A very awesome video! However, I have a question about the speed of light. Does the light from the car's inertial frame even exist? I mean it never reaches the car, and something that doesn't exist doesn't have speed, or is it just me being stupid?

[@eigenchris]

I'm not sure I understand the question. What do you mean by "the light never reaches the car"?

[@a.c.cefalas5152]

The best I ever watch. Thanks!!!

[@benjaminbrat3922]

Hi, thank you so much for your videos. They are so clear and well structured, I think I'll send it to tutees. As to the muon disintegration experiment, you are not the first person I hear saying that it proves the validity of special relativity, and on a very formal level, I don't quite agree. It formally proves that Galilean relativity is incomplete (or false, strictly speaking) and aside from that, special relativity explains the phenomenon. Casually, however, I completely understand your point, it is a strong piece of evidence that special relativity is closer to the truth than Galilean relativity. I have no certainty however that this interpretation of scientific theories is valid. Stay safe and healthy

[@eigenchris]

Yeah, I understand your point. Nothing in science is ever "proven" I guess, only falsified.

[@benjaminbrat3922]

@@eigenchris Yes, although it was the source of very animated debates with friends and colleagues =)

[@edwardmacnab354]

A clock moving in the direction of the earths spin at the equator will run slower than a clock standing still on the earth as it spins , and a clock moving in the opposite direction to the earths spin at the equator will run faster than the stationary clock . Also , all clocks on earth at the equator run slow compared to what they would run at If the earth was not spinning .

[@helmetongrass1893]

Wait a second so then what is happening from the pov of the muons themselves?? Like if i were to shrink a test subject and make him sit on a muon as it fell to the surface of the earth and later asked him if he enjoyed the ride and did he reach the surface, what would he tell me? That the muon brought him all the way to the earth's surface or did it popped out of existance in midair??

[@eigenchris]

From the muon's perspective, the earth's atmosphere is length-contracted to be about 10x shorter. So the test subject on the muon would experience the "ordinary" decay time, but would still reach the earth's surface because the distance travelled is 10x smaller.

[@kimsahl8555]

Einsteins postulate 2: Any ray of light moves in the "stationary" system with the determined velocity c. What is the "stationary" system? Galilei: A "stationary" system don't exists.

[@lowersaxon]

So moving clocks „run“ slow, ie run slow actually but moving rods „appear“ short? What?

[@active285]

Thanks you for the nice series and slides. Sadly 101b is missing a lot of slides. I like to take annotations directly when watching and recapture afterwards by myself!

[@eigenchris]

I believe I lost some of the slide on that video, which is why the file is incomplete. Sorry about that. Most of the other files are complete.

[@active285]

@@eigenchris Ah ok, no problem! I might be able to reconstruct them.

[@jfkt9467]

Can you elaborate on Maxwell about different inertial frames ?

[@eigenchris]

I go over some stuff involving the Maxwell Equations not working with Galilean relativity in video 103e. Maybe try watching that, and leave another comment if you still have questions.

[@samymaziz7193]

then i have a question and i want you to answer me please in the experiment of the train you send the light perpendicular to the velocity vector of the train how things will be if we send the light not perpendicular to the velocity vector of the train please answer me because this is a question i did not find an answer to it

[@eigenchris]

You would still end up with a time dilation effect, but the math would be a bit more confusing because the light is moving in the same direction as the train since we can't draw triangles easily in space. I talk about this a little bit in the 104a and 104b videos and draw the light beams on a spacetime diagram instead.. The math in 104b is more complicated than this video though. kzbin.info/www/bejne/a5O2qmRurJ13npI

[@hemantaphurailatpam3956]

My prof. also against using relativistic mass, thus we use relativistic momentum instead.

[@General12th]

I like considering the overall "inertia" of a system based on the sum of its rest energy, kinetic energy, and potential energies. This nicely sidesteps any wackiness with relativistic mass while also being a conserved quantity in special relativity.

[@berl411]

So we first measure muon's decay time here on Earth's lab?

[@EventHorizon618]

It always worries me that we should use light when performing this thought experiment. Instinctively I feel that that light must be a special case meaning that the experiment might fail to apply in all circumstances. I was wondering if the solution to my problem is to reconsider Einstein's second postulate to be: the space time interval is equal for all observers? It might be an interesting starting place with the maths. But then I guess we lose some of the intuitive nature of the thought experiment.

[@eigenchris]

In my relativity 104a and 104b videos, I cover this again, but much more geometrically on a spacetime diagram. I think it works in all circumstances. Also, I think saying "the spacetime interval is the same for all observers" amounts to the same thing, if you accept light has a zero spacetime interval (you can just solve for c in 0 = (ct)^2 - x^2 - y^2 - z^2 and find you get the same speed of light c in any inertial coordinate system).

[@michaelmacdonald2907]

The crazy thing is that since photons are moving at the speed of light - they are not travelling through time and should have no length. How does that work anyway ??

[@eigenchris]

I don't think reference frames in the frame of a photon are well-defined in the standard version of relativity. We can measure the time it takes light to go from one place to another when we're looking from an inertial frame, but light it self has no good definition of "proper time" in its own frame.

[@shashvatshukla]

My guy this video was so good!

[@narfwhals7843]

Isn't the increase in gravitational force in your last example exactly countered by the time dilation, so there would be no difference in motion? I just got here after watching both your tensor series and i greatly appreciate all your work!

[@eigenchris]

I don't think so? In the 2nd moving frame, lengths contract, and time slows down. I would have thought time would need to speed up to counteract a larger force? It's been a while since I've done any calculations with this, but inverse square laws aren't invariant under Lorentz transformations.

[@narfwhals7843]

@@eigenchris Time slows down so it looks like the attraction happens slower than would be expected from the larger mass density. Like moving masses create a repulsive gravitomagnetic field which acts against the attraction. I didn't calculate if that cancels out exactly, either. That is just what my intuition says. Thank you for your reply!

[@narfwhals7843]

@@eigenchris I've thought about this some more and found that apparently the Gravitomagnetic Maxwell equations aren't Lorentz invariant. Which I don't understand, to be honest, since they have the same form. And there should be a four-current of mass flux. So you just declare that the vacuum permittivity for gravity is 1/4πG and you have basically the same equations, at least in the weak field limit. They should even give gravitational waves. I'm a bit lost on that. en.wikipedia.org/wiki/Gravitoelectromagnetism

[@eigenchris]

@@narfwhals7843 So, just so we're on the same page, I think the standard Newton's Law of Gravity GMm/r^2 is not Lorentz Invariant (same goes for Coulomb's Law kQq/r^2 from E&M). The "correct" Lorentz-invariant equations of E&M are Maxwell's Equations, where the magnetic force "saves" problems caused by the electric force being not the same in all frames. (You might already know all this, sorry if I'm repeating it.) I've heard about this proposal to make "Maxwell's equations for gravity", which is the article you linked to, and it says "This approximate reformulation of gravitation as described by general relativity in the weak field limit makes". As for why they aren't Lorentz Invariant, I'm not totally sure. It may be related to the "equivalence principle", and the fact that mass (the "charge" for gravitoelectromagnetism) is also embedded in Newton's laws F = ma, whereas electrical charge q is not. To be honest I'm not yet at the point where I can teach GR. I'm still learning it myself.

[@narfwhals7843]

@@eigenchris the gravity equations aren't even GR. They are older than even special Relativity. I had thought that they would save the same problems that way. And that this could be explained in SR with the same length contraction and time dilation terms that "fixed" electromagnetism. But apparently that just isn't the case. You may be right about it being because of m in both formulas. Maybe it's related to why gravitational waves emerge under different circumstances (changing quadrupole) than em waves. All that being said I think you're doing a great job teaching in these videos and thank you again :)

[@atsavozdovachki4287]

Perhaps already reported but anyway, you say Tplatform Is movie clock and is greater than Tstationary, (on the train) and this is time dilation and moving clocks run slower. Isn't this a contradiction, given the choices of moving and stationary you make? Just an unintended choice of wards.

[@Ash18-17]

Can u pls tell me the best book for relativity general and special ?

[@eigenchris]

I don't have a "best book" recommendation. Some suggestions are: - Sean Carroll's free online GR notes - "Exploring Black Holes" free online GR text. Focuses on black holes, but there are also sections on gravitational waves and cosmology - "Gravitation" by Misner, Thorne, and Wheeler. This is very detailed and more advanced

[@Ash18-17]

@@eigenchris thank you 🙏

[@GetflytoFreedom]

The theoractical minimum by leonard susskin

[@biblebot3947]

(Partial^2)t? How does that work? Is it meant to be (partial t)^2?

[@eigenchris]

Yes. My bad.

[@Dismythed]

3:28 "... not compatible with Galilean relativity"? WHAT??? Galileo was the one who proposed them in the first place. He also proposed a third postulate not included here that fits here: "There is no absolute frame of rest," which is perfectly compatible with these, and physicists reference it all the time. (That is the postulate that the church went up in arms over when he proposed that the earth was not the center of the universe.) I think you are confusing Galilean Relativity with Galilean transformations. Galileo could not have believed what Newton believed because Galileo died the year Newton was born and Newton rejected Galileo by referencing an absolute frame. So the Galilean transformations were Newton's way of reconciling Galileo to his own theories of an absolute frame.

[@eigenchris]

Galilean relativity doesn't support the speed of light being the same in all reference frames. That's what I was trying to say.

[@Dismythed]

@@eigenchris You never clarified where that comes from. Galileo wasn't even aware that the speed of light was a thing. How can you say his theories didn't support it? Being incomplete does not make a theory wrong or "fail to support" a more advanced theory. Also, how is it not covered by the statement that physics is the same in all reference frames? You can't say he was wrong because he never made any calculations about it, nor did he make any statements that contradict it. (If you say he did, then please quote HIM, not your physics professor.) You have to be going entirely off of the transformations which are more Euclidian than Galilean and created by someone who believed in an absolute rest frame. Galileo did not.

[@eigenchris]

@@Dismythed The speed of light will change under a Galilean transformation, because the speed of everything changes under a Galilean transformation. Nothing in any of my videos in this series requires an absolute rest frame.

[@Dismythed]

@@eigenchris I'm afraid you are not hearing me. The Galilean transformations were made by Newton, not Galileo. It is more Euclidian than Galilean. You cannot point at the Galilean transformations and say: "This is what Galileo said" because Galileo did not create the transformations. Newton did. I did not say YOU support an absolute rest frame. I said Newton supported an absolute rest frame. This isn't about you, except in that I think you are misrepresenting Galileo because a professor said it and now you are toeing the line. All I want is for you to establish what statement made by Galileo (NOT from the transformations not authored by him) "fails to support" or is "not compatible" with the second postulate of Relativity.

[@foxhound1008]

enjoyed the video. in your example of the car (with the flashlight) moving relative to the scientist, although the speed of light is the same for both observers, the frequency of light is not. Of course, this does not show who is really moving, and who is standing still, just that there is a relative velocity between the two. Can you do a video showing the extent of this frequency shift? And how this would effect space travel? for example, a high velocity space ship, traveling thru space, would have to deal with the increased frequency, and energy, of a star it is approaching. Every video I have seem on special relativity talks about time time dilation and length contraction. Nobody ever really talks about the frequency shift, which for normal every day speeds, is negligible the same as length contraction and time dilation.

[@eigenchris]

I don't have plans for a video on this right now. You can search "relativistic doppler shift" to find the answer ti your question though.

[@spasokan]

There appears to be a logical flaw in interpreting the Muon Experiment. Events are invariant. The happening of any two events is an invariant fact. The observers only measure the space and time differences between those two events differently from their respective perspectives. The first event is a muon being born somewhere in the distant sky. The second event is the muon striking an earth-detector. When an earth observer observes the second event, it cannot be said that an imaginary observer who has been travelling with the muon could not watch it. Then, how is it possible for the muon to exceed its expected life span and live till it reaches the earth detector? The non-intrusive observations cannot alter reality. Maybe the increased life span of the muon was not due to Time Dilation, and the acceleration of a muon may increase its lifetime. Please clarify.

[@eigenchris]

An observer traveling along with the muon would also experience time dilation with the muon. I don't think the concept of a "non--obtrusive observer" makes sense.

[@spasokan]

@@eigenchris Thank you very much for your prompt response. I think I didn’t draft my question with clarity. Let us view the facts purely from the perspective of the muon. It is born somewhere in the sky. It finds the Earth at a distance, h meters, coming towards it with speed, say v m/s. Obviously, it will take h/v seconds for the Earth to reach it. If its lifetime is shorter than h/v, the event of the Earth reaching it will not happen. If the event did not happen, it did not happen for all observers in various frames. The very fact that it happened proves that its lifetime is ≥ h/v seconds, which is longer than its expected lifetime. This increased lifetime or the occurance of the event of the Earth and the muon colliding cannot be due to unrelated factor of an Earth Observer or an Observer in any other frame observing or not observing the relative motion between the muon and the Earth. The most probable reason for its increased lifetime seems to be its acceleration. If my question is still unclear, please ignore it.

[@eigenchris]

The point I try to convey in later videos i that both the muon observer and the earth observers observe the same thing (muon hitting the earth) but they attribute different causes. For the earth observers, they thing the muon's clock is ticking slowly because of its velocity, so they believe its lifetime is extended in their frame. FRom the muon's perspective, its clock is ticking normally, but the length of the atmosphere is length-contracted along with the entire earth because the earth is moving relative to it. So the earth frame attributes the muon hitting the earth to the muon's time dilation. The muon attributes hitting the earth to the atmosphere's length contraction. The standard versions of Special and General relativity say that acceleration doesn't directly affect clock measurements. It's only the instantaneous velocity (velocity tangent vector) that impacts clock measurements. Acceleration can change the 4-velocity vector, so it can indirectly impact clock measurements, but the formula for computing clock time only directly depends on the velocity vector, not the tangent vector. This is called the "clock hypothesis" and as far as I know it matches every experiment we know of.

[@spasokan]

@@eigenchris I shall view your later videos, and if it is irresistible, I’ll trouble you for clearance of my doubts, if any. By the way, I am not a professional physicist, and it has been my long-time wish to understand Einstein’s Relativity Theory. I read many books and viewed several video lectures, but I could not understand the subject despite my best efforts. After viewing a few of your videos, I was delighted beyond words and felt that I had found an excellent teacher who explains even tricky concepts in an easily understandable way with 100% clarity. I am now seriously viewing your videos on Relativity, and I hope that I’ll soon ask you to clarify my doubts about the advanced concepts of General Relativity.

[@lepthymo]

The muon example is so cool. So the thing goes fast in space, therefor it goes slow in time, so something that goes slow in space and fast in time, like the earth will have traveled 20 seconds while the muon has only traveled 2. Time really is the 4th dimension.

[@debrucey]

Where 101c?

[@skyfall-t8p]

I didn't know Gauss's law for magnetism has a lot of different not-universally-acknowledged names until I saw you call it "Nobody's law" and checked its Wikipedia page. Interesting...

[@eigenchris]

I just made that name up for fun because I don't know what the correct name is.

[@samymaziz7193]

first i want to say excuse me for any mistakes because i am algerian and my english is not very good

[@new-knowledge8040]

2:10 The Michelson-Morely test did not prove that an aether does not exist. It did prove that such a thing was not detectable. Then comes the claim, "There's no special 'stationary' frame of reference' ". Well, if you consider Space-Time to be your stationary frame of reference, and you proceed to analyze how it is that motion can take place within this stationary 4D environment, you will soon find out and understand how the Special Relativity(SR) phenomena is created in the first place, and within mere minutes after that, you will derive the SR mathematical equations. They key to understanding it all, is to understand that the magnitude of motion is the same for all objects that exist within Space-Time. Make a simple geometric representation of that by simply stacking motion vectors and length scalars, and by using it to assist, you can derive the SR equations in mere minutes, including the Lorentz Transformation equations.

[@new-knowledge8040]

Another amusing mistake, is when people say, "Time and Space are relative.". They make relativity example statements like, "I am at rest in space, and it is you who are moving. Then the other guy is to say, 'No, it is I who is at rest in space, and it is you that is moving.". What's funny though, is that they never give examples like, "I am at rest in time, and it is you that is moving through time, it is your clocks that are ticking, NOT MINE. And the other guy is to say, 'No, it is I who is at rest in time, and it is you that is moving, it is your clocks that are ticking, NOT MINE.". Yep, that "Time Relativity" example is always missing in their explanations of SR, for some reason. And that is because what they do always miss within their explanations of time, is the major ingredient that explains how it is that both observers are always in motion through time, rather than one being in motion relative to an others absence of motion.

[@dialectphilosophy]

You can’t consider spacetime to be a “stationary reference frame” because a reference frame is defined coordinatively, whereas spacetime is a coordinate independent four-dimensional manifold. The fact that it is modeled as unchanging does not equate to it being “stationary”. You would confuse people with ambiguous terminology. As to your second remark, yes no one is stationary with respect to time, but some through it faster than others, so by any definition space and time are still “relative”.

[@new-knowledge8040]

@@dialectphilosophy Oh yes I can. What you do is up to you. Anyhow, by starting with a simple A-B-C analysis of motion, you can soon derive the SR mathematical equations in mere minutes, and do so even if you have absolutely no physics background education at all. Simply start from scratch, and proceed to analyze what motion is, and what it is that is required to make motion possible, such as the existence of a stationary environment that it takes place within.

[@dialectphilosophy]

@@new-knowledge8040 If you want, you can expand your definitions to such a generous degree that you can basically demonstrate anything. But if you are adhering to the conventions supplied by the majority of mathematicians & physicists, then what you have said in your original remarks is both incorrect and misleading.

[@new-knowledge8040]

Expanding to the point of completeness, is wonderful thing. You can observe the absolute picture, or just look at it in a limited relative point of view.

[@kimsahl8555]

Light propagates in all systems at rest, and don't propagates in moving systems.

[@jewulo]

What do you mean that light propagates in all systems at rest?

[@kimsahl8555]

@@jewulo The meaning is about light that never propagates in systems of motion. The observer system is always at rest (to the propagation), so light propagates with constant c to the observer.

[@nhatanhnguyen71]

5:37

[@rupabasu4261]

The saviour

[@alejrandom6592]

10:48 "image not to scale" 💀💀💀💀

[@canyadigit6274]

NEW VID

[@MaxMaxx-tb6nz]

I spend a lot of time trying to understand , but in vain. The whole situation is COMPLETELY symmetrical. The person on the station can claim train move - speed goes mirr distance on train - time slow down on train compare to his clock The person on the train can claim a statuon move, speed travel more distance on the station - time goes slower on station They can't just encircle time dilation on each other. It doesn't make even a slight sense. 😢 It's not a science denier, but it all looks like a complete bs, which gives a correct result by a coincidence.

[@rktiwa]

You have been trying to starve us for your videos. Well, you succeeded. Would you please stop it now?

[@eigenchris]

A new one will come out tonight and another on the weekend. These videos do take time to make.

[@vidutv4520]

Terms1

[@Igdrazil]

I'm sorry but again despite your great effort to be precise, accurate and correct, your rhétoric is heavily fallacious. You are not aware that you keep using ILLICITE ABSOLUTE RETHORIC. Indeed when you say that "the moving clock tips slower than the fixed one", this is totaly incorrect. This is arbitrary interpretation that is not what the Theory of Relativity leads to, and which is allthemore obviously false since the situation is reversible. And not even in Relativity one clock can tip faster AND slower than another one, "at once". You are not sticking rigourously to what Relativity leads to. The only thing that can be rigourously said is that a relatively "moving" observer will SAY, through light exchange (acording to Poincaré clocks synchronisation algorithm), that the observed "fixed" clock (that he Sées Moving!), tip at a certain rate. This MEASURED rate Dt'=gamma.Dt. Not more. But this CANOTot be said to mean that the fixe clock DOES tip at this rate, and neigther that his "moving" clock tips at different rate than the "fixed" one. It is only a MEASUREMENT, hence a drasticaly RELATIVE POINT OF VIEW, WITHOUT ANY ABSOLUTE POSSIBLE RHETORIC. Each observer has no mean to know what the other clock is "actualy" doing. This "actually" makes no sens anymore, it's an ILLICIT ABSOLUTE RETHORIC. The ONLY KNOWLEDGE ACCESSIBLE IS THE MEASUREMENT. And not only theorically, also physicaly since the two observers will never meet again to check anything, since they are in relative uniforme straight translation. That's What Relativity Theory teachs us. You cant keep your ILLICITE ABSOLUTE RETHORIC. The only reachable FACTS IS, LIKE IN QUANTUM MECHANIC, THE MEASUREMENT. That's why Poincaré 1885-1898 clocks synchronisation algorithm is soooo important and fundamental. It is THE Heart of Relativity. And this is not a détail. What you are saying is a radical misinterpretation, obviously leading to logical basic non sens, violating precisely the SYMMETRIC Principle of Relativity! Be carefull

[@Igdrazil]

Despite the global technical quality of your pedagogical work, I'm very sorry to have to point out that you are repeating false historic "facts". No way that THE PRINCIPLE OF RELATIVITY could be Einstein invention. The historic facts, the historic documents let no doubt that it was HENRI POINCARÉ, the Science Master of the XX th century, who generalised since 1898, the galilean Principle of Relativity, to a UNIVERSAL FUNDAMENTAL PRINCIPLE FOR ALL PHYSIC (MECHANIC, ELECTROMAGNETISM, GRAVITATION, ETC). Poincaré publish it since 1898 in several textes and academic courses (1998-), conferences 1900,1904 St Louis), academic articles (1898, 1900, 1901, 1904, 1905), Books (1902, 1905). And just to point out one example, 1902 Poincaré best seller "La Science et l'hypothèse" détails all the main point of Relativity : Poincaré fundamental remark of obsolescence of aether concept (1885), Poincaré clocks synchronisation algorithm (1885-1895, that is the PHYSICAL mother of all the revolutionary Theory of Relativity), Poincaré fundamental Principle of Relativity (1898), Lorentz-Poincaré transformations (1895), PROPER TIME, apparent lenght contraction, apparent Time dilation, etc. And we have the words of Einstein direct friend and 1902-1904 Olympia Academia collaborator, who recalls that the "Academia epistemological team" : Einstein, Mileva, Besos, Solovine, etc, intensively studied Poincaré 1902 best seller "La Science et l'hypothèse" during 1902-1905 period. So NO WAY CAN ANYBODY PRETEND WHITHOUT EVIDENT LIE THAT EINSTEIN COULD BE THE INVENTOR OF THE THEORY OF RELATIVITY. NO WAY! On the contrary the Theory of Relativity doesn't start in septembre 1905 with the ("fraudulent" and full of mistakes) plagiarist article of Einstein (& Mileva who wrote it very surely sunce Einstein was ill), but on the contrary ENDS ON 5 JUNE AND JULLY 1905 AFTER 20 YEARS OF HARD WORK FROM LORENTZ AND POINCARÉ. Lorentz half opened the important door of coordinate transformations letting partialy invariant Maxwell's équations, and Poincaré corrected them in 1898 to their actual perfect form that he had the generosity to call them LORENTZ TRANSFORMATIONS. Poincaré showed since 1898 that they form a group and that fact being essential to their rigourous establishment. In total contrast of Lorentz and Poincaré brilliant and perfect work, it is sad to have to say that Einstein-Mileva september article on the Dynamic of électron is a scientific garbage, fraud and plagiat. By three times Indeed Can one find with horror in this bullshit article Einstein-Mileva taking référence frame physical speeds to be (c+v), (c-v) and last but not least sqrt(c^2-v^2), in total contradiction with the Principles of (Poincaré) Relativity and the (Maxwell) Principle of constant speed of light, as Keswami points out wisely in two brilliant articles. So give us a break with your Einstein Propaganda. What a SHAME. What a scientific and historic INSULT. What a pathetic illicit rewriting of Science History.. What a total lack of FACTS CHECKING. May you correct such disrespectfull fallacy

[@alexboehm7171]

why do you say "thee" with every word???? Love your content but this ....

[@eigenchris]

I had no idea I was doing it until people pointed it out.