Visualization of Einstein's special relativity

[@angledcoathanger]

This helped me grasp the degree to which I don't understand this concept.

[@IHateLife13]

Hentai404 I was thinking 🤔 the same thing.

This visualisation is a daydream.

[@anitabonghit2758]

1 line is shorter than the other depending on whether you are watching from a stationary perspective or whether you are moving with the object emmiting the light. 1 person sees the light reach the 'wall' at tge same time. The other person sees it reach at different times. The speed of light does not change. What is chaging is time and length

[@rodrigolondres5592]

Did I just learn special relativity from a video sponsored by "The Rocker Spaniels - The Greatest Dog-Band in the History of Rock" ?

[@marcushendriksen8415]

I think we all did

[@-_Nuke_-]

Its funny cuz its true :D

[@jacobcastillo3384]

Who was in charge of producing this visualization? I want to congratulate them!

[@udiprod]

Thanks! :) I do this personally as a hobby. Thanks for your support.

[@jacobcastillo3384]

Nailed this one, make more!

[@joncavanaugh9980]

+Jacob Castillo Yeah, second that, for sure.

[@implementedideas1983]

Jacob Castillo yep

[@harriehausenman8623]

Best explanation on the whole net!

[@wishcraft4u2]

The world needs more videos like this, in fact classes should be taught using this kind of visualization.

[@wolfboyft]

Wow! An Ultima Underworld 2 pfp! nice

[@udiprod]

The scene with the photon moving at 180% c shows the 'classical' view, i.e., the common thinking before Michelson's experiment.

[@AbandonedMines11]

I'm reading "The Elegant Universe" and the second chapter explains Special Relativity pretty well in laymen's terms. That same chapter also talks about "time dilation" and "Lorentz contraction." This video is also helpful. I love this stuff!

[@nerdy5999]

I had that book but I lost it :(

[@NazriB]

Lies again? Sexist Racist

[@daytime2189]

@@nerdy5999 I stole it

[@gold333]

It’s interesting to realize how he came to this conclusion after studying Maxwell’s discovery that c is constant. Speed is simply distance over time. If absolute speed is never changing the other two variables must be malleable. Makes perfect sense.

[@yoshidc1]

I like to think I understand this.

[@Zambicus]

Tl;dr: the angle (compared to horizontal) of both yellow lines has to be the same, otherwise the speed of the two photons is different - which is a physical impossibility. Only the second transformation keeps both angles the same. Quick n dirty explanation: A: the speed of light must always be the same B: speed=distance divided by time. In the visualization, distance is the x axis, time is the y axis. So the speed of the photon can be found by taking the horizontal component of the yellow line, and dividing it by the vertical component. In the first transformation, the vertical component stays the same for both lines, but the horizontal becomes different, which means the ratio between the components is different for the left line and the right line i.e. the speed of the two photons is different. This cannot happen in physics, therefore this transformation is incorrect. In the second transformation, both the horizontal and vertical components change for both yellow lines, in such a way in fact, that the ratio (i.e. speed) remains the same for both lines. The speed of light remains constant, ta-da! This has some effects (shrinking, slowed time, broken simultenaenity), which are visualized at the end. The effects become more pronounced the faster you go.

[@Zambicus]

@@SubkhanSarif as far as I know, the speed of an electromagnetic wave (in light's case, the speed of a photon) in a given medium (e.g. air, or water, or vacuum), is simply constant. You could have two photons travelling at different speeds I believe, if they were in different media (e.g. one in air, the other in water), but in this experiment, that is not the case.

[@udiprod]

@LeconsdAnalyse The video shows just the principles of special relativity. I guess QM and GR complicates matters but I'm not expert enough to say how it should affect this video. You can think of it as a thought experiment or a hypothetical one. Regarding the 3D, you are basically right. The X and Y axes are used as space, and Z as time, but the Y axis is quite degenerate (the cart has height but all the action is on the X axis). I used the Y axis to change camera angle instead.

[@capellidipaja]

I'm deeply amazed. I've been searching for a video like this for months but I've never found anything like this one... I mean these 10 minutes (yes I've seen it a few times) have been super illuminating, thank you (I love this channel)

[@mfunke]

This is by far my favorite visualization of the effects of special relativity. You can see all transformations clearly and the fact that light doesn't change speed. Perfect!

[@-_Nuke_-]

Einstein BROKE the old physics of his time in pieces! Gravity is not a force any more, fallen things are not falling and the reason we see them fall is due to the bending of spacetime Time, Size and Simultaneity all have to brake for causality to be preserved! What a stunning realisation, that all of what we see around us is an illusion of our senses. Einstein was fortunate enough to see his theory be proven correct before his death - most groundbreaking physicists and innovators have their theories be proven way after their death. "A falling man will not feel his own weight" was Einstein's happiest thought! And I'm pretty sure the concept Relativity made Einstein so, so happy :)

[@isaiahcorrinth5754]

Looks like this graph is based on the idea that once a photon is fired out of the beacon, it "coasts" at light speed until it hits the sensor. In reality, photons are "self-propelled," so to speak. Photons travel at the speed of light, not move at the speed of light. So, I would imagine it's like firing a missile calibrated to fly 100mph from a plane moving 80mph... the logic of the classical view in the video suggests that the missile would fly forward 180mph, but remember the missile is calibrated to only fly 100mph.

[@MegaFPVFlyer]

Taking an interest in relativity has been a reminder of how smart some people are...

[@Oceiros95]

+Jonah Beale They only appear smart to you because of your understanding of the topic. As Einstein pointed out, everything is only relative, and its relative because we use something as a reference.

[@MegaFPVFlyer]

puddlemonster14 Damn. Never thought of it that way.

[@ericsu4667]

On the contrary, relativity has been proven to be incorrect in physics but still correct in mathematics.

[@werds1392]

Eric Su What do you mean? That’s like saying notes have been proven to be incorrect in playing music but still correct in writing it...

[@ericsu4667]

The difference between physics and mathematics is physics for real world and mathematics for virtual world. Special Relativity is based on Lorentz Transformation which is mathematics and has nothing to do with real world. vixra.org/abs/1706.0498

[@udiprod]

That's right. This is exactly what is demonstrated in this video: Photons emitted on a cart travelling at 80% light speed seem to travel at light speed no matter if you or on the cart or on the ground.

[@mybluemars]

Einstein preserved the speed of light by changing everything but the speed of light. I wonder what would happen if we had no constants for the Universe at all?

[@Mavrik9000]

@Justin Porter What does "alborate" mean?

[@udiprod]

If you refer to the scene at 2:18 then it just seems so since the right photon is barely visible when shot. The cart follows the time-space diagram where it is clear the gun is shooting both photons at the same time.

[@864208642]

The speed of light doesn't change between the two frames of reference as you explained. But your final visualization still looks like there is a difference in speed between the two when the only difference is the frame of reference. If you could show the same two photons in the two separate frames of reference at the same time the clarity of what's happening would be a lot more apparent. Good job with the video.

[@anselmschueler]

The photons move at light speed, but the distance required to get to the other side is greater on one side than on the other.

[@xfactoid]

It only looks like the speeds are different if you haven't understood the coordinates. Space in one direction, time in the other, so speed is represented by the angle, always a 45 degree angle in these coordinates. Really nice video.

[@udiprod]

@busybuzzbuzz It's indeed a bit confusing. The ground is the grey rectangle under the cart. Movements left and right represent movement in space, while movement towards the camera represents passage of time. In view 1 it the ground is moving to the left and the cart is stationary (except both move forward - but this represents time). In view 2 the ground is stationary and the cart is moving to the right. In the diagram shown after each view: the vertical axis is time and the horizontal is space.

[@psltmtir]

Very intuitive animation. Loved it.

[@udiprod]

What you describe occurs when the scene is viewed from the ground's frame of reference according to relativity. The photons do not travel the same distance since the cart is moving forward, making the path of the photon that moves backwards much shorter. This is made clear in the time-space diagram presented right after this scene.

[@skob_otp]

It not easy to understand but you did a very great work !

[@udiprod]

Physics deals with measuring things (e.g., measuring length, measuring time, measuring weight). 'things getting shorter' means that measuring them in one frame of reference has lower results then measuring them in another frame of reference. Physics does not deal with questions like 'what is the true length?'. This is left for philosophy.

[@civotamuaz5781]

FUCKING COMIC SANS!

[@ladamyre1]

As good an analogy as our limited minds can conceive. Yet, quantum entanglement proves information DOES travel faster than light. The "packet" of information tells a "twin" photon to change it's spin at a speed faster than the cosmic speed limit (300.000 km/sec), therefore either one or both theories are flawed understandings of physics. They are both accurate enough to advance technology, but so is the old "Newtonian" physics, and General Relativity proves it to be flawed. We're not there yet.

[@israelg99]

I don't get why in Einstein's relativity visualization the cart shooting 2 photons on the right side but 1 on the left side.

[@udiprod]

It's shooting one photon in each side, but the one shooting right takes a long time to hit the detector, because the detectors are also moving to the right. By the time it hits, already another pair of photons is shot, so for some time you see two photons moving to the right. The photon shot to the left hits the detector very quickly, because the left detector is moving towards it. It disappears long before the next pair is shot. You can verify all this looking at the space time diagram at 1:57

[@udiprod]

@ferose2 No. General relativity deals with gravity and with accelerating objects. This video deals with objects that move at constant velocities, which is the domain of special relativity.

[@elidrissii]

Now, if you're really interested in Physics, read some math textbooks and do a lot of problems. Then, you begin with the most elementary physics and work your way up needing more and more advanced math that you already know, or else, you'll have gaps in understanding. I have great recommendations for math and physics (Especially math) and if you want the names or links to download, just PM me.

[@DSRT888]

okay

[@Fragranttoe]

I have no idead how to dm. So, I am writing a comment here, hoping you will dm the links. Thank you in advance.

[@mrfrankincense]

This is the best video on explaining special relativity that I've seen on the internet.

[@jordanweir7187]

awesome way of explaining it :)

[@udiprod]

The photons moving at 180% speed of light are shown in a scene that describes the CLASSICAL view of physics, prior to the Michelson-Morely experiment and Einstein's relativity. At the time it was thought possible.

[@milton3204]

Jesus fucking christ I hate modern physics. I miss classical physics, everything was so beautiful and straightforward....

[@milton3204]

I may have mentioned Jesus Christ but I assure you it had nothing to do with religion. So I suggest you to calm down.

[@MrTopgearlover]

+ABC you are reason there is extremists in this world.

[@workhardism]

Its a public forum, people can and will add whatever they like too, including their religious views. If you just can't handle views, including religious views, other than your own, don't comment in a public place. Obviously.

[@lpsp442]

Consistency is only ever useful in a very precise context. When evidence reveals that what seemed like consistent rules actually do not always apply, one must update!

[@rinfeast3445]

@ABC people do this all the time and it's not a bad word because then that would mean "Oh My God!" is a bad word, when both are really used as phrases commonly said in tiredness and/or surprise, and christians wouldn't ever say stuff like that if it truly were offensive.he didn't offend anyone because he said something about himself and not about others... you need to grow up.

[@udiprod]

@qqdudeq Note that in view 3 both photons are moving at light speed relative to the ground, not to the cart (that's the point of relativity). The photon moving left is moving towards the left sensor at light speed, and the sensor moves *towards* it at 0.8 light speed. The photon moving right, however, needs to chase the right sensor that is running *away* from it at 0.8 light speed. This explains why the right photon has a longer path.

[@wilsonhsieh6487]

Interstellar brought me here

[@MegaFPVFlyer]

Same here

[@Pabloyellowboy]

This is the clearest explanation i've never seen. Thanks you. Now I really understand without any doubt what is relativity.

[@RedsBoneStuff]

COMIC SANS!!!

[@minnarewers3573]

UNDERTALE!

[@Mswordx23]

+Minna Rewers Ugh shut up, stop bringing up the game everywhere

[@minnarewers3573]

Mswordx23 Im just undertale trash.

[@udiprod]

Rotational movement is hard to analyze. But even for someone who moves fast in a straight line - his clock won't slow down from his point of view. They would slow down from the point of view of other observers that do not move along with him.

[@harriehausenman8623]

This is the best introductory visualization on the whole net! 🤗

[@udiprod]

The video only shows the transformation between two different inertial frames of reference: the ground's frame of reference and the cart's. I have no idea what mistake you are talking about.

[@udiprod]

@Cathode0 In view no 1, it is assumed the light travels at light speed relative to the cart, therefore it reaches both sides simultaneously. View no 2 presents the same scene from the ground, according to classical physics. Since in classical physics simultaneity is preserved, here too they reach both sides simultaneously. View no 3 presents the same scene according to relativity. Here the light travels at light speed relative to the ground, so the light reaches the back wall sooner.

[@MrPetur4o]

Key for understanding this video: 0:20 TIME dimension on the VERTICAL axis; SPACE on HORIZONTAL axis. Also, Within the Cart frame of reference space OUTSIDE the cart is irrelevant. In the ground frame of reference both space within and outside the cart are relevant. The speed of the card accelarates the right photon with 80%c and the left photon with -80%c. However, since c is constant in both frames of reference, it is necessary to CURVE the space-time coordinate system. I hope this helps!

[@udiprod]

There are a lot of technical issues involving how you see things with your human eyes. In particular, to see an object you need it to emit a photon that will hit your eye and this will also take time. If you are asking what would happen if you use accurate measurements then the answer is you'll get the same results as shown in the video.

[@nicos1097]

Thanks mr Lorentz

[@udiprod]

@ISUowns That's exactly right. In other words, simultaneity is something relative: what's simultaneous to one observer, is not simultaneous to another. It sounds strange at first, but it's not the strangest thing in physics.

[@armarr]

Though relativity still is a very elusive concept for me, this video has made it a lot clearer to me than that 30 min documentary I just watched. Thank you for enlightening me !

[@vanpat1987]

THIS animation deserves a PHYSICS oscar !!

[@Indrius]

Here's 3 simple hints that will help you understand this video: 1) this is a 2-dimensional space: x + time. The cart moves in 1-dimensional space - on x axis from left to right. The time dimension progresses from up to down. 2) objects that move at the speed of light travel at 45 degree angle in this spacetime chart (if 1x is 1 second, then 1y is 300k km). 3) to preserve the speed of light of photons, they must always travel at this 45 degree angle. Therefore you see those space transformations.

[@udiprod]

There is only one cart. The two theories mentioned in the video (Newton's classical theory and Einstein's relativity) have very different predictions as to how this cart would look like when observed from the ground. Both are shown in the video (Einstein was right but of course Newton didn't know so much about light speed back then so you can't blame him).

[@GinoTheSinner]

Saw this video in physics class couple o' years ago. It's as simple as it gets. You're mearely touching the basic idea and still you have to pay absolute attention not to get lost. His mind was brilliant to discover all he did in a single lifetime, with no predecessors to talk about. Or with. Ingenious

[@lumajs]

I think it's an excellent visualization. I just used it on my blog, article about the 100th anniversary of Minkowski spacetime. I am afraid that those who say that it's confusing on this video will always find relativity confusing.

[@udiprod]

The experiment shown in the video was never done in real life (and most likely cannot be done in real life). The surprising consequences of relativity, however, were confirmed in numerous experiments. To mention just one: the slowing down of time was observed on fast moving particles that decayed slower than expected.

[@VoidGravitational]

The quality of the thumbnail is top-notch

[@albedoshader]

I’m relieved this video doesn’t contain distracting and unnecessary music.

[@venkateswaranc8694]

The transformation was proposed by Lorentz and not Einstein, so the transformation was called as Lorentz Transformation. But it was Einstein who applied this transformation to space-time.

[@albedoshader]

He was able to rid himself of the notion of absolute spacetime, what Poincaré, Lorentz, Maxwell and others couldn’t or didn’t. He built on what others had prepared but that’s what all physicists do. The ingenuity lies in the readiness to think around the corner, to see time and space as one and to leave the notion of absolute space and time behind. There’s no doubt that others would have figured out the same maybe a couple of years later, but it was Einstein who did it in the end :)

[@rubecube8875]

I notice that sometimes I spend ages trying to learn a concept, then I give up and move onto something else, when I go back to the concept later, I can understand it much easier. The brain forms neural pathways that make it easier to think about the concepts you're learning.

[@projectmoses69]

"It shrinks moving objects." The closer an object gets to singularity the smaller space becomes = the smaller the object in that space becomes = the shorter the frame drag distance light (photons) needs to travel in that space = the faster light appears to travel in that space because of time differential= vortex physics. time and space converge at singularity, the closer you get to singularity the faster time flows, the further away you get the slower time flows. frame dragging due to torque.

[@libalchris]

it's honestly hard to tell exactly what you're trying to say. The idea is this: If I shoot a lightbeam forward, I will measure it to be going c (as previously defined.) Another observer travelling past me at half the speed of light (relative to me) will also observe the lightbeam to be travelling at c (relative to himself.) We can agree on our observations because (from my point of view) time for him is moving more slowly, and his length is contracted.

[@udiprod]

@bphysicsguy No, since the blue grid represents the ground viewer's perception of space-time. According to him the cart's X (space) position changes with time (with both space and time lines marked by the blue grid). According to the green grid the cart has a constant X at all times, which is of course the cart viewer's perception of things.

[@signorellil]

Exactly. In fact, the special theory of "relativiy" is misnamed - it's indeed the theory of the only thing that does not change: the spacetime interval between two events. In many way, the whole heart of the theory is well defined by the famous Minkowski quote "Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality"

[@kmarinas86]

1) The observer cannot actually see the photons being emitted from the center of the cart to the ends of the cart. 2) The observer only sees A) the photons from the light bulb, B) the photons that scatter as a result, and C) the other glowing lines 3) If the observer were to "measure" the speed of the photons, he would have to have a clock that corrected for the moving positions of the points. Doing so would give the "speed of light" as the answer.

[@sidewaysfcs0718]

guys guys, get this through your head the speed of light is CONSTANT, light does NOT slow down in air, it's the PHASE velocity of light that is lower, because light can't travel through air without getting bounced off of molecules, wich is why it reaches destinations apparently slower, but the speed of the photons in between absorption and re-emission is always c. so stop saying light slows down though air or water, it doesn't, it's the phase velocity that slows down.

[@mfunke]

This is perheaps the most clear visualizaion of Einstein's Relativity I've seen. 5 Stars from me.

[@klopedokle]

1. “The most essential requirement is, however, that irrespective of frequency the wave or wave-train should continue for a certain interval of time, which I have estimated to be not less then one-twelfth or probably 0.08484 of a second..."

[@signorellil]

Yes they do. Gamma (the Lorentz factor) is a relation between space and time who contracts space and dilate time by the same proportion.

[@iamstoned4life]

I recommend you to watch a few other videos about this topic and then watch this video again. It all fits together and makes perfect sense.

[@ObjectsInMotion]

You misunderstood the slowing down of time. Without added energy, the wheels would continue to move at 10,000 rpm regardless, because to an observer inside the vehicle time moves at the same pace as it always did. It only seems slowed down from the outside.

[@McDaidUSA]

Loved the graphics, but they ended up making the explanation more confusing. The simple diagrams drawn by Einstein conveyed the concept better.

[@nazishhussain2571]

I understand till the 1st view. The tilting of path in grounds view(classical physics) confuses me.

[@udiprod]

@lip333 This is not accurate. Relativity says both an observer on the cart and an observer on the ground will see the photons travelling at the speed of light. According to classical physics this is impossible, because for the ground observer, the speed of the cart adds up to the photons speed. Relativity solves this by the Lorentz transformation shown at 1:23, which indeed squishes and skews both space and time axes.

[@signorellil]

gamma is 1/sqrt(1-(u/c)), u is the measure velocity of the clock frame of reference, c is the speed of light. As c is a constant, gamma is a function (inversely proportional) to u - in your example the speed of the moving clock relative to you.

[@LeconsdAnalyse]

@raydredX There is (as i`ve already mentioned) 3-acceleration ONLY during take-off, turnabout, and landing. Given (say) δ: 0

[@CACBCCCU]

Let's say that SR means "subluminally-moving things should always appear to be moving subluminally, regardless of the observer's inertial frame" and let's suppose SR's space and time transformations can be treated separately. In the case of an oncoming train moving at a relative speed of 4/3c, let's suppose the transformations act to make the approach appear to be subluminal, because otherwise we'd never see what's coming, plus both trains are moving at subluminal rates, so maybe it'll work.

[@udiprod]

@magichristo It only seems so, since the cart is moving as well. Relative to the ground both photons are moving at the same speed (of light). It is 'proven' in the diagram that immediately follows this sequence, where you can see the photons` lines are both tilted by 45 degrees.

[@Timmerdetimmerdetim]

There's something bothering me: if both observers agree on the velocity v among their respective reference frames then I feel like they should agree on the rpm of the wheels on the train as well. So why does everything in the train seems to slow down but the rotation of the wheels do not?

[@sithsmasher7685]

This example is far more clear than the one with two lightning bolts striking a train at the same time (or not). Your example is a visualization of another train example where a lamp is placed in the middle of a compartment. I really love how you visualized the transformations. Since I never had a chance to study the math, this really made me help to understand why Galilean is wrong and Lorentz is right.

[@udiprod]

@65465468 You are right - relativity rules this out. Since no signal can travel faster than the speed of light, when you start pushing one end of the stick, it will take 4 seconds (or more) before the other end will start moving.

[@CACBCCCU]

A lot of the motivation to see time as dilated in moving frames (and yes, I know the impression is supposed to be mutual and it's all relative for any inertial frame) is that the path of the moving light-clock's light beam always appears as having further to go in one cycle than it did before the clock started to move. But looking at it from the perspective of the moving frame, the beam was taking a longer cycle before it supposedly started "moving" and the "moving" shortened the beam's path.

[@Unclevertitle]

Thanks! This is an excellent visualization. It really helps with me understand special relativity better and also, blows my freakin' mind. Seeing the photons travel at different rates through time (thus traveling at the same rate through space) just really puts the knowledge together in a way I didn't quite have it before.

[@niskat9044]

Simply amazing! Helped me a lot in understanding special relativity and twin paradox. The graphic representation is done nicely.

[@BCJ1985]

Yes that's pretty much the idea. Speed can only be measured in relation to another object. But no matter what speed you're travelling in relation to that object, a ray of light will always appear to travel in relation to you and the object at the same speed (300,000,000 m/s)

[@wowsa0]

Relativity only applies to velocity, not acceleration. There is no absolute velocity, but there is absolute acceleration. If you are in an accelerating frame of reference you can tell that it is you who is accelerating because the laws of physics for you will be different. Think of a car, while it is moving at a constant velocity there is no way to tell if you're really moving, or if it is just the earth moving. But if you are accelerating you know because you are pushed back in your seat.

[@danielcuricica]

Nice way to visualize the preservation of light speed. Nice job.

[@udiprod]

@dropyapants In final scence, the same phenomemnon occurs again. In the furtherst cart, which is the cart viewed from the ground (blue grid), both photons move at light speed **relative to the blue grid**, while the cart itself also moves relative to the grid. Try to ignore the cart, and just look at the photons relative to the blue grid.

[@signorellil]

Poincare and Lorentz derived the invariancy of the speed of light as a result of their calulculation to justify the failure of the Michaelson experiments, while Einstein had the same invariancy as an axiom - he STARTED from it, as a consequence of the Maxwell equation. It was conceptually a completely different attitude than those of Poincare and Lorentz.

[@GShock112]

I am 0 in physics but I think this video is really good. Thank you udiprod!!!

[@udiprod]

It's impossible to prove a physical theory. You can only strenghen the belief in it by validating its predictions in experiments. All the more so if it has suprising predictions. This is certainly the case for relativity. The experiment described in this video is indeed almost impossible to perform, but the principles it relies on were observed in other types of experiments.

[@udiprod]

@chinamanspeakenlis In the relativity scenes they move at the same speed - that's not an illusion (The illusion was that it seems as though the left one was faster, but it's not). However, they do not necessarily cover the same speed. In the cart frame of reference they do, but in the ground's frame (according to relativity), the left photon and the cart are moving toward eachother, and they meet after a shorter time and distance. This is clear from the diagram at 1:57.

[@TajgerTrzynascie]

This video is the best demonstration i've seen

[@signorellil]

The time dilation is a (actually quite simple) mathematical consequence. If you postulate that a) The law of physics MUST appear the same for anyone moving in a constant velocity and in a straight line IRRISPECTIVE OF THE VELOCITY and b) the speed of a beam of light will be measured with the same value by anyone doing that WHATEVER OF ITS OWN VELOCITY when you're trying to write down a simple transformation of coordinate the time dilation will simply appear by itself.

[@rebusd]

your model brings me one step closer to understanding the Lorentz trans and its application towards relativity. Correct me if I"m wrong, but the said transformations were postulated in attempt to explain light's defiance of galilean/newtonian mechanics (ie there exists an 'outside' to nature which serves as the 'absolute' frame of reference to all systems), and yet somehow redeemed itself through einstein... in other words, killer visualizations bro.

[@hughbreidenbach]

Man, that is SOOOO getting 5 stars. Did a little relativity at college (before I dropped out ahem) and this is outstanding. Highbrow critics- shut up.

[@pearlnaturalvision]

To those of you who don't understand or being confused -- simply "accept" the fact that the speed of light is constant... and that the "other things" are relative, otherwise you will be stuck at the beginning.

[@udiprod]

@dropyapants In the ground's frame of reference both photons are traveling at the same speed. Due to a bit of an optical illusion, since the cart is moving, it mistakenigly seems as though the rear one is faster, but you can see in the space-time diagram very clearly both photons trace a 45 degree line.

[@UniverseIsAwesome]

After I watched this video, I learned that there are two types of Relativity - General Relativity and Special Relativity.

[@Englishsea24]

Because he was fortunate enough to have Lorentz and Poincare try to tackle this problem before. But for some reason even Poincare could not completely solve it, so Einstein was just in the right place at the right time and building on Poincares work, he was able to properly visualise and thoroughly work it out.

[@firteandrei21]

Wow! Probably the best visualization of the problem... ever! Good job! You should do more of those!

[@CACBCCCU]

I guess a recent artical at Physics Today, "Moving mirrors make virtual light real" inspired me to to go on a very long rant about SR here. I guess I'd like to thank the uploader here for the tolerance shown to my longwindedness. Thank you.

[@JDoucette]

Wow, great. Never seen it like this. The last part is a bit confusing, and maybe you could throw a little less text all at once, but the 3D demonstration is a great idea, and works amazingly well. Good job. Sharing this one on facebook...