I never understood why everything moves at the speed of light... until now!

[@Mahesh_Shenoy]

Head to squarespace.com/floatheadphysics to save 10% off your first purchase of a website or domain using code FLOATHEADPHYSICS PS: I made a visual error in the last part. Since the space is shown as 2D, I should have used a flat aeroplane instead of a 3D aeroplane. I saw a question in the comment about what if the object was a sphere? Then it 'turning' wouldn't change the length of the shadow and so length contraction? That can't be right! Well, you cannot use a sphere because, again, we are only using two dimensions for space and one dimension for time. So, you would have to imagine a disc. And when a disc turns, it's shadow will contract. Sorry about that oversight.

[@piyush3836]

So does it also applies for black holes as time ticks slower near them ?

[@Prongsie2]

@@Not_a_Physicist I'm from Nepal as well! To multiply two or more physical quantities is basically like combining them (not adding, combining) Area of a wall equals Length times Height is because for each number of horizontal unit there is, there is a unit of vertical as well. The same concept is for physical quantity, for each unit (length, mass, breadth, height, motion, etc) of one physical quantity, when you multiply it with another, there is another same equal unit of the physical quantity

[@lih3391]

@Mahesh_Shenoy Sir, what about the spacetime invariant, (ct)^2-x^2=S^2? I believe this is what you are referring to, but you have forgotten about the hyperbolic geometry of time. This is what makes time different from space right? You can't move freely, only forwards by some amount.

[@babyoda1973]

So maybe that's why entanglement seems to move faster we are seeing the actual extra dimension😮

[@ayushsahoo2078]

Thats Great, thats mind blowing, keep making videos on such topics and thank you sir, for such marvelous experience!!!!!!!! Could you please provide the link for that book?

[@manasyadav1993]

That was insane. The last part blew my mind. Probably the best explanation why time can’t flow backwards. Way better than the entropy explanation.

[@mantrid777]

it doesn't mean time can't flow backwards. it actually assumes the particle moves forward in time (i.e. it doesn't explain that, it assumes that). then explains why we/particle don't have access to "time-travel" along time dimension like space but instead see "ghost" of time dimension instead (as clocks). if we assume a particle going back in time, we'll get same conclusions for a backward-time particle.

[@Rudyard_Stripling]

If you sat on the event horizon in a black hole you would see everything in the past everything in the present and everything in the future all at once. It is written God has this view so he may well have his home in a black hole.

[@alexb241]

Actually entropy is a super logical explanation why time flows in only one direction. It is one of the most accessible aspects about the whole theory.

[@Rudyard_Stripling]

Actually, if everything goes the speed of light in the 4th dimension then there will be no entropy or death and any decay at all.@@alexb241

[@the6millionliraman]

@@Rudyard_Stripling Unfortunately for that deity, if it lived in a black hole, it would have zero influence on the rest of the universe because its sphere of causality would be limited by the event horizon of the black hole it lived in.

[@louisalfieri3187]

When he turned first the plane! Chef’s kiss!!! I have a masters in physics and can say Great Job. I love this guy.

[@jellewillems7118]

You managed to explain an extremely complicated phenomenon like general relativity with just a plane vector, some arrows and a graph so that even middleschool kids could understand it, and it made perfect sense. Like the Einstein, the founder of this whole idea said: "If you can't explain it simply you don't understand it well enough." And you absolutely did. You have my sub, sir!

[@krzysztofciuba271]

yes? In this case, he died without knowing how to resolve his/P.Langevin's nonsense Twin Paradox (in R.Schlegel, his conversation in 1952, 3 years before his death- in footnotes in R.Schlegels' books).

[@josephbigler]

You're explained several topics that have always kind of baffled me. Not only that, you managed to do it without all the complex mathematics that usually goes with them. This is one of the best explanation of all of these topics I have ever seen. Thanks very much.

[@VictoryDance0]

I can vouch for this being a factual comment I am in middle school and understand this topic

[@BritishBeachcomber]

If you can't explain it simply... True... That's why quantum theory is so enigmatic.

[@Peregringlk]

Your channel has rapidly become one of my favourites about science. Your focus on intuition is priceless.

[@N8_Bit_official]

This x 1000

[@kcz6865]

It turns out that we really do live in Plato's cave, surrounded by the shadows of reality.

[@abebuckingham8198]

Underrated comment.

🤯

[@forestvan4915]

This comment is arguably one of the most brilliant on KZbin

[@bsadewitz]

Yeah, that's why the allegory is still fundamental in epistemology. ;-) It's not something that turned out; it always was (well, according to Platonists, anyway, but u don't have to be so committed for it to be worthwhile to contemplate). That was Plato's (well, at least Socrates' lol) point. He was using allegory to illustrate en.m.wikipedia.org/wiki/Theory_of_forms

[@abebuckingham8198]

@@bsadewitz It's also a reference to the two shadows he uses in the video. That's why it's so clever.

[@NgocBaoM1022]

I found your channel 40 minutes ago and I'm already fallen in love with your contents. Please make more videos, I'm glad that you are the one explaining all of this to us.

[@THICCTHICCTHICC]

Your ability to explain such abstract and complex concepts so simply is genuinely unparalleled

[@akaHarvesteR]

Holy hell, the idea of length contraction as a ROTATION of the moving coordinate frame is absolutely mind blowing!!

[@vyvianalcott1681]

I actually need time to recover from the amount of fundamental shifts of understanding I just experienced, holy shit.

[@Rudyard_Stripling]

I think the length contraction is a flaw in this, what if the airplane was a round sphere, then it wouldn't matter what angle it is at, no contraction.

[@Littleprinceleon]

If the third dimension in that example/analogy is time, whhat part/property of any object extends in this direction?

[@akaHarvesteR]

@@Rudyard_Stripling Actually it would. Calling it a rotation is a bit of an oversimplification. What's really happening is a sort of out-of-round rotation that actually causes the object to skew.

[@Rudyard_Stripling]

with a sphere, you can't have an out-of-round rotation lol.@@akaHarvesteR

[@meoncrack]

I've been on and off other YT videos on this topic for a few years now, and none of them clicked for me until yours. Seriously amazing job. Your genuine enthusiasm and knowledge on these subjects really draws people in. Please keep it up!

[@krek17]

I am just trying to imagine what are we projections of, and man this explanation, with the graphs, and pythagoras, all so simple, and you said it, wrapping your head around. Good video!!

[@arman-cl6be]

Probably the best educational video I’ve seen on KZbin. I really appreciate your enthusiasm for explaining these topics in an intuitive way

[@manmohanmahapatra6040]

19:56 best part of the whole video. Loved it! ♥ To summarize: The speed of light (c) is constant in 3D space because observers' measurements of time and space adjust (via time dilation and length contraction) to ensure they always calculate c as the same. However, in 4D spacetime, c's constancy is deeper-it’s an intrinsic property of spacetime itself, independent of any observer's motion. The 3D constancy relies on observer-relative effects, while in 4D, it’s a universal truth of the cosmos.

[@jasonlough6640]

Dude, that energy at the beginning, you are absolutely an engineer at heart. I get the same way. Theres something special about understanding something, a kind of magic from holding a thought and understanding whats going on. Its exciting, as exciting as a PvP match or playing soccer or riding a roller coaster. Awesome vid.

[@bsadewitz]

It isn't unique to engineering [such that one could say "you're an engineer at heart" on that basis, tho please understand I am not deprecating engineering]. If one could say any discipline could claim it more than any other, that discipline is philosophy, but I don't really look at it that way--not quite. I had an intro philosophy textbook titled "Does the Center Hold?". That comes from: "Turning and turning in the widening gyre The falcon cannot hear the falconer; Things fall apart; the centre cannot hold; Mere anarchy is loosed upon the world ..." That comes from "The Second Coming" by Yeats. en.m.wikipedia.org/wiki/The_Second_Coming_(poem) "The poem uses Christian imagery regarding the Apocalypse and Second Coming to describe allegorically the atmosphere of post-war Europe.[2]" It's also the title of this book, just to give you another example of the theme: en.m.wikipedia.org/wiki/Things_Fall_Apart I'm sure you can see the applicability of the metaphor to understanding writ large. Indeed, consider the word "understand" itself. One could literalize it as standing under something--in awe.

[@bsadewitz]

The opposite of things falling apart is the integrative project of science, or generally seeking a coherent body of knowledge about the world, which science is a part of. And obviously physics plays a fundamental role in this project. Whether physics as it is constituted today will always be considered the MOST fundamental remains to be seen, as one may argue that the only thing that we actually have access to is consciousness itself. And nobody knows for sure what that (or perhaps THIS) even is, or whether we are even capable of coming to grips with that. I like to think so, but we don't know ...

[@glenben92]

Channels like this are the thing I'm most grateful for on the internet

[@clairecelestin8437]

My favorite way to visualize higher dimensions is to recognize that what "a different dimension" means is that it can move independently on that dimension without impacting the other dimensions. So instead of worrying about "where" the 4th dimension is, I just imagine objects in 4d space as being some color on the spectrum from red to blue, and things can only interact with objects that are the same color. If I could tie a ball to a string and swing it in the vertical-color dimension, it would move up and down in a straight line in 3d space, and the ball would change color to be purple at the top and bottom of each swing, and it would be red as it passed the midpoint on the way down, blue as it passed the midpoint on the way up.

[@PegLegKegCraig]

“(The 4th) dimension is length contracted to zero” This is such a beautiful explanation. We’re just along for the ride like a fish in a tidal wave.

[@MichaelHarto]

You make me understand the length contraction concept. Thank you

[@gordonhamilton7160]

I love this stuff so much. You do a great job, Mahesh!

[@Mahesh_Shenoy]

Thanks, Gordon :)

[@williamwalker39]

​@@Mahesh_ShenoyWe present an experiment that proves conclusively that information can be propagated nearly instantaneously across space, in the nearfield of an electromagnetic pulse. The experiment consists of a ~30kV high voltage spark generator creating an electromagnetic pulse that propagated 1.5m to a detector. The leading edge of the transmitted pulse and the leading edge of the detected pulse were then compared using an oscilloscope and no time delay within the capability of the scope was observed, where 5ns is predicted if it had propagated at the light speed. The maximum uncertainty in the measurement was 1ns due to noise in the electronics. Since a pulse is digital information. This experiment proves information can be transmitted across space nearly instantaneously. The results is perfectly predicted by Maxwell equations, which yield a wave equation set equal to a source term. Analysis of this equation shows that the phase speed, group speed, and information speed are instantaneous in the nearfield and reduce to the speed of light in the farfield. Below is a link to see a preprint of the paper. We are currently looking for a journal for peer review and publication. The impact of this discovery has implications in both engineering and the foundations of modern physics. The result is completely incompatible with Relativity. Instantaneous signals invalidate Relativity of Simultaneity in all inertial frames and can be used to synchronize all their clocks. In addition, a derivation of Relativity using instantaneous electromagnetic fields (light) yields Galilean Relativity, where time is the same in all inertial frames of reference, and there is no speed limit for mass, fields, and, even light. This can be easily be seen by inserting c=infinity into the Lorentz Transform, yielding the Galilean Transform. This means that if a moving object is observed with farfield speed c light, then Relativistic effects will be observed. But the effects are not real and can be proved by simply changing the frequency of the light, such that instantaneous nearfield light is used, causing the Relativistic effects to disappear. This then proves that the effects of Relativity are just an optical illusion. Since General Relativity is based on Special Relativity, then it has the same problem. A better theory of Gravity is Gravitoelectromagnetism which assumes gravity can be mathematically described by 4 Maxwell equations, similar to to those of electromagnetic theory. It is well known that General Relativity reduces to Gravitoelectromagnetism for weak fields, which is all that we observe. Using this theory, analysis of an oscillating mass yields a wave equation set equal to a source term. Analysis of this equation shows that the phase speed, group speed, and information speed are instantaneous in the nearfield and reduce to the speed of light in the farfield. This theory then accounts for all the observed gravitational effects including instantaneous nearfield and the speed of light farfield. The main difference is that this theory is a field theory, and not a geometrical theory like General Relativity. Because it is a field theory, Gravity can be then be quantized as the Graviton. Lastly it should be mentioned that this research shows that the Pilot Wave interpretation of Quantum Mechanics can no longer be criticized for requiring instantaneous interaction of the pilot wave, thereby violating Relativity. Consequently the Pilot wave interpretation should become the preferred interpretation of Quantum Mechanics due to its deterministic simplicity. Electromagnetic pulse experiment paper: www.techrxiv.org/doi/full/10.36227/techrxiv.170862178.82175798/v1 KZbin presentation of above arguments: kzbin.info/www/bejne/qZazlX1tq7iErLM More extensive paper for the above arguments: William D. Walker and Dag Stranneby, A New Interpretation of Relativity, 2023: vixra.org/abs/2309.0145 Dr. William Walker

[@ItzBluh]

​@@Mahesh_Shenoywhat if spacetime moves through a 5th dimension?

[@anjin77]

The first time this really 'clicked' for me was reading Brian Greene's "Elegant Universe" years ago where he used the example of a car that only goes 100 mph, and how the velocity must be 'spent' in other dimensions/axes when not driving in a perfectly straight line. In the book's appendix he expanded on this basically using simple vector mathematics. Once you picture x^2 + y^2 + z^2 = magnitude^2 in 3 dimensioal space, then it's not much of a leap to determine that x^2 + y^2 + z^2 + t^2 = c^2. And since our movement in three-dimensional space is comparatively very slow, then the rest of our magnitude through spacetime must be 'spent' in the t dimension. That was a huge 'light bulb' moment for me that day. Good stuff! What was a new light bulb moment for me in this video was your visualization for length contraction. Thanks!

[@adlikfasadlikfas9531]

Something clicked in me while reading your comment: we say that kinetic energy is dependant on velocity and mass (as in E=mv^2/2) so using that logic and the way you made equation we can say that E=mc^2 is basically our kinetic energy in spacetime. Of course this logic might be flaved but it still sounds awsome.

[@sgiri2012]

How passionate you are. You are dedicatedly explaining the topics. Iam all ears when you are speaking because it's so exciting to hear. To top it all, your facial expressions gives positive energy for the topic and made us feel good. You are explaining all the intricate details of the topic which is so good. Oh my gosh, Despite you have crossed 1 lakh subscribers, you are still posting one video per week. Please try to make your folks engaged throughout the week. Sooner or later, this channel should be flooded with the hoards of people and zeptillion of videos. My dream will come true. P.s. please teach us about tensors. How it can be felt under the bones ? I think you are the right person for explaining this thing. Who all want about tensors ? Please give thumbs up for this comment.

[@sylfthesoundyoulongfor8363]

Maesh's tensor nedeed agreed 😂

[@ArjunA-ln3ov]

Im a cs major... watching ur videos and other physics videos at my pace after college is the only time of the day I really enjoy

[@birdthompson]

what is cs?

[@ArjunSingh-vx6cj]

And here me (A junior software engineer) addicted to his Videos

[@ArjunA-ln3ov]

​@@BanterMaestro2-vh5vn "at my pace"

[@sierra1513]

Counterstrike major

[@jakobo8908]

i love this channel so much, for someone interested in physics but who has no academic experience those explanations that everyone can understand are so perfect

[@asadirshad6405]

Mind blown in the last part 🤯. This has become my new favorite youtube channel now! Please keep on making more explanatory videos like this ✌️

[@PhysicsConcept-cd1bi]

Keep making this kind of videos which have a different prospective to visualise the physics. We appreciate you for it!

[@jameswebb3410]

One of the best(if not best) explanations of complex concepts I've ever come across on the internet.

[@rustyspygoat4089]

This channel is incredible. Exactly what I have been looking for...

[@Bassotronics]

Thank goodness for videos because to comprehend such things just reading text would be very difficult.

[@bensyversen]

What a great video. This really helps me to understand this stuff better as I've been trying to wrap my head around it recently. Thank you! Here is a great historical detail that you might enjoy: this mathematical description of space-time didn't originally come from Einstein. It actually came from mathematician Hermann MInkowski, who was Einstein's math professor in college (Einstein didn't take math very seriously at that time and tended to skip class). After Minkowski presented these ideas, Einstein was initially skeptical. He called it "superfluous erudition" and wrote that "since the mathematicians have grabbed hold of the relativity theory, I no longer understand it myself!" Einstein thought the fancy math obscured the beautiful physics. But he eventually came around when he realized just how powerful a tool this was for understanding the idea and making new predictions. Cheers!

[@DrDeuteron]

well, he never could have formulated General Relativity w/o Minkowski, since its Minkowski's 4D spacetime that gets curved. I have never seen a GR formulation without it.

[@bensyversen]

@@DrDeuteron yes, this was Einstein's reaction to Minkowski's work in 1908. As you say, it wasn't long before he realized that he couldn't formulate general relativity without it.

[@mreclecticguy]

Wow. You explained a complicated idea in such an intuitive and visual way that it was easy to follow the logic.

[@remcodejong9149]

I understood fairly quickly what the implications of the two dimensional projection was on space time. I completely did not see length contraction coming though, that had me stunned.

[@nisarshaikh-e6o]

same

[@omegabased]

I just wanted to let you know that I love your channel. It is my favorite new channel by far. Your content is fresh and interesting and inspiring. It’s not just the same old recycled tropes that every other physics channel does and you don’t get enough credit for this. I wish you unlimited joy and success and I can’t wait to finish watching this video. Thanks brother

[@iceseic]

Mahesh your channel is what I truly need deep down in my heart! Years ago I questioned do light experience time (which you answered years later), and back then that question drown me in my own postulate and thought experiment that also lead me to think we travel through time at C and whatnot. Even the use of shadow analogy that manifested in our space world that can be observed, but man your explanation and visualization actually make a clearer implication of this way of approach and many things I never thought of despite thinking the same thing ❤❤

[@iceseic]

It was pure hype when you explain the length contraction

[@dhrubajyoti53]

My mind was totally blown away... I never thought I could ever get a real perspective and physical significance of relativity.... Thanks for this awesome video...

[@soberskater]

The enthusiasm is contagious! I'm going to read today instead of watching any more screens... great video!

[@benlap1977]

Your enthusiasm is contagious! And I cheered when you showed where length contraction came from!

[@AdarshRaj-fj4fw]

What does it mean by the ,term speed in time dimension.. I mean even in spatial dimensions don't you have to include time as well to measure (or define) speed in the first place?

[@dismalthoughts]

It's quite simple, really. In that 4 Spatial Dimension area, where _our_ concept of time is really just a spatial dimension through which a 4D entity is traveling at the speed of light, there's a 5th Temporal Dimension. And that 4SD entity, of which we are its shadow, is a shadow of a 5 Spatial Dimension entity which is traveling through one of its 5 Spatial Dimensions at the speed of light, which then becomes _its_ 6th Temporal Dimension -- its concept of time. So really, that 5SD entity is a shadow of a 6 Spatial Dimension entity...

[@tintun8918]

Speed just becomes a ratio of two spacial units. It is like how you can say, "That house is 3 units north and 1 units east." Speed will be like 1 unit in spacial part of space time over 1 unit in temporal part of it.

[@asdfoifhvjbkaos]

@@dismalthoughts no, general relativity does not need a 5th dimension to work

[@garylcamp]

I asked "Starts With A Bang" a year or so ago about why we are moving through time at 1 sec/sec which I noted was 186,000m/s but I got no answer. You have really shown me more than I asked for. By far! It is truly wonderful. I can see why you are so excited. Great presentation.

[@piyushpathak1186]

Ohh bhaii @21:05 explains why we can't move back and forth in time Because it's length contracted 🤯🤯🤯

[@_Kalakos]

Wouldn’t that mean past, present, and future are happening at the same time?

[@Telugu_is_the_oldest_language]

@@_Kalakosyah that’s correct all are happening at the same time

[@Super_Beast124]

This is by far the easiest visualization of these concepts I've ever encountered. Masterfully done sir

[@PaulThatcher-iu5in]

Mahesh, you say you're still having trouble wrapping your head round it - yeah, I know the feeling. I mean, I understand the points made here, I see why time dilation, length contraction, and the relativity of simultaneity flow from the idea of our 4-velocity being c - I even see why spatial dimensions are traversible in both directions, but time is not. However, I just know that this feeling of understanding will be blown away by the next, deeper realisation of the beauty of this explanation. And that's what's amazing in Relativity: no matter how long and hard you look at it, it just keeps getting more beautiful in its simplicity.

[@DrDeuteron]

"it just keeps getting more beautiful in its simplicity." Physics in a Galilean universe would be a mess.

[@angeldude101]

@@DrDeuteron Physics in an elliptic universe wouldn't have time, since the spatial dimensions are already elliptic. If it did have time, then accelerating enough would let you go back in time. Galilean relativity at least maintains a distinction between space and time, though the 0s that can pop up can make things weird.

[@helifynoe6956]

Not the next deeper realization, but the one from the past. I threw some vids together 10 years ago that use a geometric representation of "c" motion within space-time, (a geometry composed of the combination of motion vectors and length scalars), all to explain special relativity and at the same time it is used to derive the SR mathematical equations, and derive the Lorentz transformation equations, with each derived in the most simplest and quickest way ever possible.

[@one6632]

Now that I've watched your videos,I really need a friend like you at college to talk to all day on these amazing concepts!!! I really admire the way you're excited on the realisations we get in the process of understanding. Sir never stop uploading 💫✨

[@Raj-yv7xt]

after seeing this video i would recommend to move around alot ...so that u r moving slower in time's axis and thus live more than the people of the same age...

[@divxxx]

You don't actually live longer, you can simply delay your death with respect to others. Don't forget that from your own perspective you are at rest, therefore your clock is ticking normally.

[@kylelochlann5053]

There is no "time axis" in the world to move relative to - there are only the world-lines of objects.

[@Raj-yv7xt]

@@kylelochlann5053 i am sorry i don't have proper words to say my thoughts...but what I wanted to say is like even if the one moving doesn't feel anything different in time he experiences... but as a third person we know that the one traveling or moving is experiencing time dilation and will not age similar to that of a person stationary or consider on earth....one traveling will experience the time normally but he can know in his head that he is experiencing time dilation and when he meets his counterpart he will be younger than him..and when i mean at rest or stationary it is all relative ...in this intuition of his he says everything is moving at max. Speed ..i.e light speed ..so if we consider relative velocity we r all at rest ...or constant velocity..which we can't differentiate...time axis and all is intuition we just move through time but the time itself is measured by motion of something(photon)....but yes that's what i wanted to tell...so i said even if insignificantly small..if u move alot then u will age late or die after ur twin or any other counterpart....

[@THICCTHICCTHICC]

At best you might somehow snag an extra femtosecond or something

[@Raj-yv7xt]

@@THICCTHICCTHICC yep..ik that...but man even a part of second matters...😂

[@vikasmorje]

incredible explanation, I went crazy. Out of my interest in Physics, I have been reading about this subject, especially space time and light, since 40 years back on and off. The best visualization of complex subject in a simplest way for dummies like us, hats off. Thanks!

[@SimonThwaites]

This is a fantastic video, thank you - only the latest of a tremendous series that has become a must watch with each new one. The thing I struggle with is whether ideas like this - in this case that everything moves with the same speed in 4D and that our experience is a ‘projection’ in 3D with a ‘phantom’ length contracted spatial dimension which represents time - are actually meaningful as descriptions of how the universe really is, or if they are instead very clever analogies and images that exploit superficial similarities between systems that are characterised by ratios between two numbers.

[@juliavixen176]

The atoms of our bodies and all other material objects are held together with electrostatic force... basically, "light". We are partially made of light, and so parts of us are propagating at the speed of light... you are always traveling at the speed of light and you can't go faster than yourself. Atoms and molecules are basically microscopic light clocks. The really important question that always gets skipped over in explanations of Relativity is: " _Why does anything travel _*_slower_*_ than light_ ?" And the answer is confinement, it's where "E=mc²" comes from... and I don't know why it only gets covered in colledge physics classes and not KZbin videos. Anyway, it's the origin of inertia (mass), and why "time" and "space" have any distinct meaning.

[@user-fv3uf9kz2t]

Ive watched a ton of these types of explanations and this video is by far the most intuitive teaching of a very difficult subject. Hats off to this teacher. We will see more of him.

[@abhaychordiya6489]

Is that the Minecraft grass block as the floor😂😂 That's nice

[@Mahesh_Shenoy]

Honestly, I just picked the first free photo I could find :D

[@smithstudiertetwas8914]

Yes that definitely is the Minecraft grass block loll

[@Snakyy1]

It’s not minecraft block textures are 16x16 this is double that

[@Astronomator]

What a wonderful, simple explanation for perhaps the most complex attribute of our universe. Well done.

[@remcodejong9149]

This may be the best explanation of special relativity I have ever seen.

[@doktorjansson]

Wow! I have done a lot of teaching at university level. The hardest thing in teaching is to explain complicated things in an easy non threatening intuitive way, and that takes a master teacher to do. You are a God!

[@davidaronson9475]

I don't think I've ever seen anyone so happy in my life as you during the explanation of length contraction. Mazel tov!

[@crow2989]

Is this why it’s said that photons traveling at light speed don’t experience time? All of their Velocity is in Space and little to none is in the Time Dimension?

[@Sahil01499]

That is the wrong question. To experience time, you in a reference frame and remember in relativity there is no reference frame of photon . So saying that will photons experience time?is actually a wrong question. He has made video on it you can watch .

[@gstgst6334]

Beatiful explanation. Amazing to see someone as well versed in all of this as you are getting your mind blown.

[@london8732]

Hi Mahesh, great video. In the part that explains the twin paradox, you stated that the twin sister moves through space, so she loses some of her velocity through time, making her younger when they reunite. Wouldn't it be the case that from her perspective, she is at rest, and her twin is the one that moved through space. So when they reunite, she would expect that her twin was the younger one. If it is just about the relative motion through space, then I don't see how this resolves the paradox. It explains time dilation from both subjective perspectives, but the paradox remains as both would expect the other to be younger from their frame of reference. This is not a criticism, I think this video was fantastic. It's just that I feel like I've missed something here.

[@pavandn]

Yes, I haven't come across any convincing explanation for twin's paradox so far. All the explanations deviate into answers that don't explain the fundamental problem. The actual question we should be asking is : "Between two objects that are in constant relative motion, which one sees time dilation and length contraction". If we can't do an experiment to determine who is moving as per the theory, then the time dilation for only one of the objects disproves this statement, as we can simply compare the clocks and see who moved !!

[@sudhakanthagirmohanta5695]

You should take into account the relativity of simultaneity and really ask what this question of age means from each reference frame. Mahesh already made a nice video regarding that.

[@drfisheye]

The perspectives of the twins aren't the same. One twin moves away, then changes direction and comes back. The other doesn't change direction. That's a measurable difference. If both would be constantly throwing a ball in the air and catching it, the twin that moves, then changes direction and comes back would lose her ball, because the ball would continue in the first direction (try throwing a ball in the air while you change the direction of your car, you will lose the ball). The twin that stayed stationary would never lose the ball, because she didn't change direction. So there is no symmetry between the twins movements. That's why one will be younger than the other one and they can observe the difference themselves.

[@pavandn]

@@drfisheye What if the space time is curved such that he doesn’t have to change direction and meets his twin after travelling in straight line?

[@drfisheye]

@@pavandn the Twin paradox is about special relativity, not general relativity, so there is no curvature involved. Even so, if there would be curvature then if the stationary twin would let go of a ball, it would fall down. If the twin in orbit (because of the curvature) would let go of a ball, the ball would continue to move with the twin. So that situation isn't symmetrical either.

[@ErvaarT809]

Wow you are a hero. I started studying by myself at 30 because I couldn’t memorize anything at school in the past. And with time I realized that it was because they weren’t teaching correctly. I was scared of gravity, light…and all because I knew that they were controversial subjects and I didn’t have time to discover everything by myself so thank you very much to you and to the author of the book.

[@user-hf9qr4bp1z]

I just wanna say your excitement and enthusiasm make me happy. You are a great teacher and love how you explain everything

[@voldy3120]

There had been times when I wished time just froze (not from embarrassment but from emotional reasons). I sort of fantasized it to the extent that I started to wonder how things would appear and behave if I moved. Now a few years forward in time, I don't have no more need to freeze time or fantasize about it but that question still comes to my mind. This is how I truly got intersted into theory of relativity. And sir from Khan academy to this you have been a great source of inspiration and great help. Thanks alot. And please keep the series going.

[@Creepyslandofdreams]

Your raw passion makes me so happy. Never change.

[@MicheleMelchionna-c8e]

These series of videos are a gem, it is such a great work, well done for everything and all the enthusiasm. One question on the last part (on the brother and sister bit) that puzzles me slightly: moving through space causes time dilation with respect to the clock in the rest frame. In THAT time direction the sister moving through space has been left behind in time. However, isn't that true from relativity that there is no privileged frame of reference (direction for time or space)? So, from her own reference frame she has not moved, travelling in spacetime at normal time (maximum time), and her brother moved instead. On what basis when they meet again she is the younger of the two? Wouldn't this imply an absolute time arrow? Thanks for any further explanation on this

[@Cliff_P]

Finally! I used to use the example a block of matter in a empty universe with a powerful rocket motor that ran and then burned out, with the time frame change always being negative with the introduction of kinetic energy. And also a satellite orbiting Earth with the gravity being slightly more on the near side of the craft versus the outside of the craft causing a relativistic time difference. Your explanation clarified everything.

[@terrycrooke1]

Just discovered your channel ... you're enthusiasm shows no bounds.... awesome job

[@raezuk]

Love this video.... you totally walked back and ran through some of some of my misgivings on previous things I've seen from you. Perspective is really the key.

[@JosephCain-hp9jx]

Wow wow wow! Mahesh, your enthusiasm is infectious. Thank you for conveying these elegantly simple ideas into full-blown mind streams. I knew I had learned to read when, for the first time, the simple letters C A T sprang from the paper and combined to form a lively feline in my mind. Your presentations work on me in the same way. Your youthful enthusiasm takes me back 60 years to my three-year-old self and I re-live the joy of discovery. Thank you!

[@stephanelaflamme7513]

That legit blew my mind sir, I'll have to think about these for a while...It's too bad I can't throw more likes at you. Probably some of the most insightfull explanations of these concepts out there, and I've been looking.

[@mwerensteijn]

Thank you so much Mahesh for creating these brilliant videos. They really help me!

[@CalloohCalley]

One of my favorite video essays ever. Thanks dude! Question: What (if anything) would happen if we rewrote or re-thought our theories of spacetime by substituting Time for "c"? In other words, what if we defined time as the maximum speed limit, and not as seconds? It seems like time, then, would become the universal speed instead of the photon (or any other massless particle). What would shift in our understanding of the universe if we redefined time in terms of speed through the 4th dimension? What that do anything useful? Related thought. What if the big bang was/is an "explosion" in time? And the entropy is the result of that? All that energy is still pushing us through the this time dimension? And the speed we measure ourselves moving through time is simply the speed the big bang is currently moving?

[@jdog987]

Yo! This is such a nice way to think about it, placing time on an axis and looking at the projection. I also loved the 'photon clock' on a cart analogy, not only did that perfectly describe time dilation, it also demonstrates how you can think of light as a particle and a wave. Great video my guy!

[@jgri1324]

It is so much fun to watch someone as excited as I was during my preteen and teen years explaining this kind of complicated physics with such intuitive examples :-) really makes my day!

[@femalwolf]

OMG!!!!!! , I had been confused for months, viewed so many videos, trying to make sense of special relativity, Now, Finally, this solved my confusion!!!

[@sunilgokhale]

Super explanation....clears the basic concepts of space-time

[@kylelieb2977]

Wow. This was literally the best explanation of spacetime and relativity that I have ever seen. Def Saving this one.

[@babyrossbaby2354]

this is insane. really blow my mind. plus he can explain such complex concept in an easy-to-understand way is amazing. thanks!

[@charlesrosenbury231]

It is a nice model. Questions remain around why we think all particles share the same dimension of time (if in fact they do which is not certain), and what is "the arrow of time" which is a record of events as things move in spacetime. This is not the first ti.e I have heard this, but it is by far the best presentation. Good job.

[@ostanin_vadym]

20:43 No future, No past, only Present exists at the same time, because everything moves in Time and is contracted to zero in Time dimension. Thank you for educational video.

[@himeshph]

"If it's just told, I don't like it, I want to discover things myself and piece things together and come with conclusion myself." - Mahesh The above quote is powerful. 👌

[@Rudyard_Stripling]

Sweet, without your help I doubt I could have understood this just from the book. Incredible and amazing.

[@knubswak]

Love your energy, friend. I also get excited in much the same ways when super deep concepts suddenly click. It feels like my consciousness suddenely balloons and knowledge comes rushing in. Always keep the good feelings flowing!

[@Arun-Home]

Your explanations are like fresh breath of air! ❤

[@yoteach]

Awesome animations of this idea! It becomes even more intuitive if you replace "c" with the "speed of causality" rather than light. Then light, gravity - anything not anchored to spatial dimensions by mass - travels at the speed of causality: the fastest way information get from one point in spacetime to another point.

[@sevenstarsofthedipper1047]

I am not a scientist nor was I a science major but, I thought that he was going to say that Gravity was a consequence of an object diverting some of its speed in the spatial direction because it looked like the plane was nosediving back into the ground the more it diverted its motion to the spatial direction. But he didn’t say that so, I am probably not really understanding what he is saying.

[@sylfthesoundyoulongfor8363]

@@sevenstarsofthedipper1047 Gravity IS Indeed a conséquence of spacetime deformation. Check PBS "IS Gravity an illusion l'' on that matter

[@sevenstarsofthedipper1047]

@@sylfthesoundyoulongfor8363 Are you saying that the “deformation” in spacetime we call Gravity is caused by mass in motion inside a moving Universe? So, then what is spacetime made of? It must be made of something, otherwise, this SR model makes no sense. Something has to generate the shadows that are used to explain length contraction in this model?

[@JohnGalt0902]

Great job! The best explanation of why only 1 time dimension. And loved the picture demonstrating the 3 consequences. Keep it up!

[@masai2]

Wooooow! Your animation with the plane and its shadow explains more than dozens of books and films I have read and watched in my life. Grats!

[@MrMoose1347]

The best explanation and shortest as to why time doesn’t go backwards is the very nature of its direction to go one direction.

[@maryannematthews7176]

Wow 🤯 I’ve been watching videos about this for a while now and this is the first time I’ve had even a flicker of understanding. Truly mind blowing.

[@kostaskakavas6266]

Thank you for all the videos, they are awesome. This idea really puzzles me. If we all move through spacetime with constant velocity c. 1. Why ? This might be a good research subject. But it is obvious to ask why, how does this come to happen ? 2. But the more puzzling. Does this also mean that there is absolute motion ? The old question: an object moves relative to what? If we all move though space time (relative to space time itself if this exists?), when I see an object accelerating, this means that it gets more space like velocity (loosing some time like velocity) relative to spacetime. So there must be an ultimate space like object (e.g. e/m waves, light) that gets all the (spacetime) velocity in space component (in all reference frames). And an ultimate time like object that gets all the velocity in time component. And this should be stationary from all reference frames. Or is spacetime a localized concept, applied to an inertial reference frame, a construct to measure time and distances? That does not have any physical meaning?

[@seabeepirate]

The illustration was well done. I’ve been imagining dimensional projections for a while. Very neat to see them in action.

[@Bored_Miss_A]

Wow! I need sometime to ponder on all these. Thanks for your effort making this video.

[@Mahesh_Shenoy]

You're so welcome!

[@Rudyard_Stripling]

I think the length contraction is a flaw in this, what if the airplane was a round sphere, then it wouldn't matter what angle it is at, no contraction. Am I right or wrong?@@Mahesh_Shenoy

[@bobspongieux]

Tell that to Elon and we'll have spherical rockets

[@Rudyard_Stripling]

We have spherical UFOs already and they could definitely be made purely spherical lol.@@bobspongieux

[@juliavixen176]

​@Rudyard_Stripling I wish he would just lookup Terrell Rotation. Length contraction doesn't actually make things *look* smaller... Also lookup Born Rigid Body Motion too, because all this "Introduction to Special Relativity" stuff is neglecting to mention that it's only describing *points* in a 1D line, and not extended 3D objects.

[@anjin77]

You are an exceptional teacher and communicator, inspiring others with your passion. I wish you much success, happiness and fulfillment! Thanks for providing such great content Mahesh! Subscribed.

[@imagiro1]

Not sure what I like more: Your explanations or your excitement :)

[@horseios3655]

This is easily the best video you have ever published on this channel. Well Done!

[@jeremiahjohnson6661]

This video is well worth watching at least twice, good work on this

[@akphotodesign]

Thank you! This explanation makes it so digestible.

[@jorgejorge8878]

Your happy energy and excitement matches exactly what I feel about this subjects. Thanks for the great content.

[@artb4700]

Thanks for the excellent explanations and your enthusiastic presentation. Enjoyed this 😊.

[@brianr8081]

Incredible video. I kept having these incredible breakthrough realizations, it would just click, only to flicker out seconds later....but I'll watch this video dozens of times. I can't believe these analogues really exist, that is so freaking cool.

[@vanjoff1475]

Hi, I just wanted to say that I really enjoy your videos and your energy and enthusiasm are infectious. Thank you for the great content, keep it a coming!

[@vanjoff1475]

I'd also like to ask if you would make a video on the work Stephen Wolfram is doing? I love to listen to him talk and feel that I follow along broadly, very broadly lol. I would love to hear your breakdown

[@sergekannon9048]

This video brought tears to my eyes I will not because it's beautiful, but because I had used my own thought experimentation to come to the same conclusion years ago. Yes! When we travel at the speed of light in any direction, we lose that dimension dimension and it becomes a temporal one. That means there are infinite spatial and temporal dimensions. There are temporal dimensions in every direction an wkectron can travel and each of those temporal dimensions will have its own spatial dimensions that are not the same as ours. I imagine this is how there are infinite universes right within our own universe. I also imagine it as if when you're traveling at the same speed and direction with photons, you experience the energy of those photons as matter. You've earned a lifelong subscriber. You are truly a high genius!

[@johnc4957]

My goodness, this man is a exceptional teacher.

[@AnkitRathi7]

That was incredible, that's the best explanation where I could visualize four dimensions. I just couldn't before watching this video.

[@nickdegroot222]

Profound and beautiful! Traveling through time at the speed of c from our own reference frame. Wow!!

[@shadowpapito]

Sometime a person can get lucky and find great content .. Thank you, this video is greatly appreciated!

[@audiodead7302]

Personally, I find relativity more profound than QM. It implies very startling things about the nature of reality. p.s. Probably the best video I've ever seen on relativity.