Special Relativity

[@maxwellsequation4887]

"With great speed comes great time dilation" -Albert Einstein

[@shaktikashyap6]

He didn't say that too..

[@LuisSierra42]

@@shaktikashyap6 How do you know?

[@dhruvpatel.1001]

Also, the *Length Contraction*

[@jd35711]

he's skinny and his clock runs a little slow, but gd can he move

[@epicvraj7736]

Ya

[@theshagg5091]

This video is so highly underrated I can't believe this.

[@velcro3105]

Agree 100%

[@JordanService]

I rate it highly! But its a newer channel.

[@parneetkaur8118]

Very true💯

[@crystalclear8813]

Time is time. Gtfo! #brainexplodes

[@LHSlash]

Well, its relatively underrated

[@theparadigmshift2461]

Thank you. Best explanation of SR I've ever seen.

[@ScienceClicEN]

🙏

[@gilgamesh310]

Yeah, these videos better help me understand the concept than any others of their kind. The visuals do a great job especially.

[@fritt_wastaken]

@@ScienceClicEN I think you were mistaken at the very end. Special relativity is well capable of describing any kind of motion with the help of calculus. General relativity is only needed when talking about gravity

[@sksamiruddin4599]

@@ScienceClicEN 🙏

[@dexter8705]

​@@ScienceClicEN I don't know.. dialect is giving him a run for his money now.

[@kayakutah]

Fortunately for me, I had watched "We all move at the speed of light" (Nov 8 2018) and "A new way to visualize General Relativity (which is brilliant, BTW!) before this, which helped understand this. These videos are fantastic!

[@thememaster7]

Why would the rear be in the future and the front in the past?

[@asadullahmaan3482]

@@thememaster7 Rear would be in the future only through the perspective of the observer who is observing the spaceship and is not actually on it. It would be in future because the light from the rear end of the ship is reaching the observer at a faster speed and for him the events occuring on it pass quickly e.g the age of the person in the rear of the spaceship,time. For people on the spaceship everything's happening at a normal rate. It is not a common phenomenon it would only occur if the spaceship is traveling at the speed of the light which is impossible.

[@Raye2797]

@@asadullahmaan3482 It wasn't because the light from the rear end of the ship is reaching the observer at a faster speed, remember that the light speed is an invariant.

[@VIPINKUMAR-gg6gn]

This is by far the best explanation I've seen after getting confused by watching 15+ videos about relativity. Thx bro :)

[@alwaysdisputin9930]

Why is the rear of the ship is in the future? u can't say. Therefore I don't think it's a very good explanation

[@justinmadrid8712]

@@alwaysdisputin9930 I think it's a bunch of nonsense.

[@eliasosterman1995]

How is it possible for this kind of channel to be so underrated. Amazing explanations, great graphics, beautiful content....

[@Doodle1283]

the idea that time itself is different on the front and the back of the spaceship to an external observer gave me a whole new perspective and intuition about the theory. I've never seen such an explanation. Thanks so much :)

[@tomekstanek]

In gravity between head and fits time is different. Your legs are in the future

[@saveearth9816]

​@@tomekstanekno your legs are in the past because time slows down near more gravity (earth) & time pass faster as we move away from earth (so our heads are on the future) ..... Head older than legs.....

[@cyberfunk3793]

@@tomekstanek In the example the spaceship isn't experiencing gravity or even acceleration and even if it was, they would be equal at front and back, so where does the difference in time dilation between front and back of ship come from?

[@tomekstanek]

@@cyberfunk3793from passing stationary observer. Front and back of the rocket will pas with the time difference

[@thebeastmeister3009]

Definition of Relativity: 0:11 Ball throw example into speed of light: 1:02 Two events occur differently depending on observer: 2:33 Previous scenario with time: 4:20 Length contraction: 5:38 Time dilation: 7:12 Summary example using muons(?): 9:03 Conclusion: 11:03

[@farbeyondbeautifuldesign9804]

This video is non sense and completely wrong. Explain how a person traveling the speed of light can shine a flashlight forward and see it hit a wall in front of them. You can’t! It would be a flat circle of light stretching horizontally across from the light then illuminating behind you. The light can not break the speed of light with an initial inertia like a baseball being tossed on a bus. You would be molecular frozen like at absolute zero temperature and couldn’t even put your hand in front of your face because your hand would then be moving faster than the speed of light to an outside observer.

[@fukovskipls]

@@farbeyondbeautifuldesign9804 Because the spaceship has mass that prevents it from travelling at the speed of light, so it can never be the speed of light. At that speed, time dilation causes the speed of light forward to appear to happen at the speed of light, while the universe speeds up around you.

[@atharvmishra5548]

Stumbled upon this channel and I think it has the best explanation on the entire internet

[@renscience]

Great as usual. One thing I would state differently and place it in the beginning. I never hear anyone making it this simple. “If you hold speed constant at all times no matter what the circumstance, something else has to give”. Given light’s velocity is based on distance (length and time), then if you hold light velocity constant in all observers views such that light stays constant in their reference frames and, also, if they look at some one else’s reference frame moving or not, then those who use light to observe find that something has to give. That would be length and time. Not sure if a similar construct could be applied to an observer using another method such as sound speed. If you hold the speed sound constant in all mediums, then the materials would require to offer the same impedance to sound. For example, air and water. Not so much. Light in vacuum travels with the impedance space time (ST) offers to propagation of electric and magnetic fields but as far as we know, ST does not vary in impedance or vary as a medium to affect c even when curved.

[@SparePlayss]

I'm 15 years old..and I understood this video fully.. what a great explanation!

[@jj6148]

I’m 14 and I did too

[@jaysalbhatt2501]

If you can explain a concept to a 15 year old in a simplified manner only then you have u understood it yourself

[@Eloblein]

I've been traveling at greater than light speed and thus, I haven't been born yet.

[@alwaysdisputin9930]

Why is the rear of the ship is in the future? u can't say. Therefore I don't think this video did give a "great explanation"

[@Tobi21089]

@@alwaysdisputin9930 it is in the future because of how light moves in the spaceship the light was slower on the front than the back therefore there are different time dilation in the ship. Because c=const it has to mean that from an outside standpoint time goes faster for the back so it will be constant and time moves slower in the front so c will still be c

[@elindauer]

Is it fair to say that length dilation is a physical manifestation of an object bending into the time dimension?

[@ScienceClicEN]

Yes ! The object gets "inclined" in spacetime, and that changes its apparent length in space

[@david203]

The object itself does not bend in the usual sense. If it is brittle, it would not break solely due to traveling fast (it might break due to other effects involving how it is accelerated).

[@elindauer]

@@david203 Yes thank you. Maybe I should have described in as a rotation into the time dimension instead.

[@david203]

@@elindauer This idea of "rotation into the time dimension" is, as far as I can tell, not part of standard physics. I did find an interesting proposal at www.physicsforums.com/threads/theory-underlying-sr-the-time-dimension-is-moving-relative-to-the-spatial-dimension.80559/, but since this has as yet to be accepted, it must be considered speculation. I'm not educated enough in physics to judge this theory.

[@flem1431]

@@david203 I took my master's in physics and in my experience, it seems pretty standard. There is one qualification though: the "distance" between two points in 4D spacetime is defined slightly differently than the distance between two points in a 4D space. This difference affects other geometric concepts such as rotation, angle etc. Consequently, a rotation into the time dimension behaves slightly differently than an ordinary rotation. In practises this means the trigonometric functions sin(x), cos(x) and tan(x) should be replaced with sinh(x), cosh(x) and tanh(x), but otherwise the equations look pretty much the same.

[@Seth-mu3wo]

Very well explained. You took a difficult concept, and made it easy for people to understand.

[@marianmusic7221]

The only way to progress in our quest to understand the universe and the life is to watch this kind of videos and renounce to our old common understandings. These videos are a real step toward that goal! Thanks!

[@cyberfunk3793]

This is the understanding since 1905 afaik, so what should we renounce?

[@arnold7726]

This is literally the type of video I want to visualise special relativity

[@hwh1946]

Really well done. I am re-reading brian Greene's book the "elegant Universe" and I am retired from being a chef. So these videos are a huge help.

[@new-knowledge8040]

Everyone always makes it complicated. They speak of the speed of light as being an invariant, and then proceed to relate everything to that one invariant alone. Well it is a heck of a lot easier to understand special relativity(SR) if you take into account the second invariant. Everything that exists within the 4D environment known as space-time, is in motion exactly as much as is light in motion across space. The only difference is that for mass particles, a percentage of that motion, is across the dimension of time. So the point is, since you are constantly on the move within space-time, all you can do is change your direction of travel. Now if you create a very simple geometric representation of that ongoing motion within space-time, you can use it to derive the SR mathematical equations, and complete this task in mere minutes. This task includes deriving the Lorentz transformation equations as well.

[@shawon265]

I'd argue that’s definitely not "easier way to understand SR". Because if you're explaining SR to someone, they probably don't have any idea what you're talking (including 4D space-time and every object's motion being a component of c). They are probably expecting you to explain what’s wrong with Galelian Transformation? Why do we need Lorentz Transformation at all? That’s why it's necessary to mention, we see light speed being constant which breaks Galelian Transformation. That’s why you need a new type of transformation that gives us a finite constant speed for light.

[@new-knowledge8040]

@@shawon265 I understand what you mean. I did not have the opportunity to acquire any physics education, so in my case I had nothing to compare to, to relate to, or to correct. In turn, I had nothing to hold me back, nor throw me off track. I simply analyzed "Motion" to determine what it is, and what it is that is required to make motion possible.

[@engywuck85]

Just watch the video „we all move at the speed of light“ on this channel!

[@vhil364]

The point about deriving the Lorentz function (more precisely, the reciprocal) from the constant spacetime speed is a very good one. Before I figured it out, the Lorentz function was just a some numbers and a variable, but afterwards it was just as abvious as why a cubes volume is a^3. Here's how to do it. Construct a 2-dimensional spacetime graph with 1 D of speed through time, v_t, and 1 D of the magnitude of the speed through space, v_s. Because v_t + v_s = c, the graph is part of a circle, which is the same as the graph for the reciprocal Lorentz function, γ = sqrt(1+(v_s)^2); you will see why soon. The circle in the spacetime graph can be described by c^2 = (v_t)^2 + (v_s)^2. C is the constant speed through spacetime and is the only objective speed, so we can set c = 1, and therefore: 1 = (v_t)^2 + (v_s)^2. Because the of way the reciprocal Lorentz function is defined, it describes the same thing as v_t: the speed through time. For example when γ = 0.5, your time elapses 0.5 as fast the person observing you; therefore: 1 = γ^2 + (v_s)^2 --> 1 - (v_s)^2 = γ^2 --> γ = sqrt(1-(v_s)^2). There is the lorentz factor!

[@jeremycleary2002]

The easiest way to understand special relativity is that it’s BS. A magic trick comprised of assumptions and disregard for the physics of light, producing a ridiculous conclusion.

[@unknownboy8833]

Your Way Of Teaching Is Extraordinary.... Everything You Tell Is Understandable❤️

[@luudest]

This channel is gold!

[@hizonopusdie]

This channel is highly underrated.

[@chamilasrimal3680]

This is sooo underrated😥 The best explanation ive ever heard

[@alwaysdisputin9930]

Why is the rear of the ship is in the future? u can't say. Therefore I don't think it's a very good explanation

[@vgry3624]

Watching this guy's videos for free literally feels illegal ngl. great content 😭

[@wolfbauer2338]

very impressive! Glad that I've found you

[@ScienceClicEN]

Thank you !

[@jeremydeveyra2462]

DUDE THIS IS SO MUCH EASIER TO UNDERSTAND THAN ANY OTHER VIDEOS! HOW COME THIS IS UNDERRATED?!

[@siroggak]

I love everything about your videos. Btw, your background music is perfect for contemplation Keep up the good work!

[@undergroundsociety1005]

I thought the same thing about the music. I wish I knew the soundtrack of it.

[@T3AMKILL]

A question that’s always been stuck on my mind regards SR: say there is a spaceship on a landing pad on earth. The spaceship blasts off at 99.9% the speed of light. 1. What would an observer on earth see (e.g. the ship instantly zipping, or not moving?); and 2. What would an observer on the spaceship looking out of the window see? You’ve explained everything so well but I can’t seem to answer this question. I need to rewatch a few more times :-). Thank you

[@mrcastor9514]

Well the spaceship can't instantaneously gain 99.5%the speed of C. It will be continuous increase in speed. Even though the time it takes could be very small. The observer will see a continuous contraction in length until the speed is constant. For greater acceleration the contraction will be faster for smaller acceleration the contraction will be comparatively slow.

[@Xphy]

Thank you !! By the way i'm a theoretical n mathematical physicist, can u give me the right to translate and dubbing your videos into Arabic language, there are a lot of people who need to feed their brains, please ❤

[@ScienceClicEN]

You can contribute to the subtitles on the French channel. Also I am planning to translate the videos to arabic, I have already done some voice tests ;)

[@Xphy]

@@ScienceClicEN you can speak Arabic too??, watching a scientific video with subtitle is not effective as watching a dubbed one. Thank you again!

[@Benoit-Pierre]

The french channel has more vids. Most channels allow community sub titles. Just work your subs. Maybe you could also copy your subs from the French channel to the English one. Visual content is.identical.

[@TheZenytram]

@@Benoit-Pierre not anymore that sucks :(

[@maxwellsequation4887]

You Sir, are a LEGEND!!!

[@AverageAlien]

I can't stop coming back to these eye opening videos. They allow you to actually understand these concepts at a deeper level

[@alwaysdisputin9930]

Why is the rear of the ship is in the future? u can't say. Therefore I don't think this video allows you to "actually understand these concepts at a deeper level"

[@gravitationalvelocity1905]

The description of length contraction being due to seeing the front, middle and end of the ship at different times is very important. Imagine of the ship was changing color very quickly in the ships reference frame. The observer on earth would see the contracted ship as rainbow colored.

[@thememaster7]

I don't get it. Why would the back of the ship be in the future and the front be in the past from the observer on Earth?

[@thememaster7]

Shouldn't it be the other way around?

[@marialuispinto8779]

@@thememaster7 "Rear would be in the future only through the perspective of the observer who is observing the spaceship and is not actually on it. It would be in future because the light from the rear end of the ship is reaching the observer at a faster speed and for him the events occuring on it pass quickly e.g the age of the person in the rear of the spaceship,time. For people on the spaceship everything's happening at a normal rate. It is not a common phenomenon it would only occur if the spaceship is traveling at the speed of the light which is impossible." > i had the same question, but someone else answered above :) and i got it ahah

[@thememaster7]

@@marialuispinto8779 Doesn't that mean the rear light reaches the observer sooner? Later is future.

[@thememaster7]

@@marialuispinto8779 I get it now. Thanks

[@jako_ronin]

Best science channel on youtube. If taking the younger/older example into account: what would happen if we collapse these realities in one place? If we land the ship on Earth, the people there would have to see one older and one younger, but the people inside the ship would have to see both at the same age (it's the same things for the clocks. would they be synched or not? it's the same example, afterall)

[@fritt_wastaken]

To land a ship on Earth you have to deccelerate it, and acceleration changing perspective. If they are in sync on the ship, they'll be in sinc on Earth, because they experienced the same acceleration

[@boukharroubamediane119]

understanding complex subjects of physics is necessary and not easy. Your videos are very clear and simple! Your efforts to prepare your videos are very much deserving of gratitude and recognition !! Thanks a lot. I subscribe, like and share. Good luck.

[@pc...430]

This channel is so amazing, I'm going to learn french, just to understand all videos uploaded on the french channel.

[@thehamsteryourparentssayra4816]

Hmm... I think I grasp the concept now. Since the speed of light is a unbreakable and fundamental law of physics, the lights on the space ship must reach the ends at the same time (if you are on the space ship) because it would be you that are stationary and the planet is moving backwards. However, if you observe the ship on the planet, the front light cannot reach the front end of the ship first because the ship is moving forward (relative to the planet) and that would mean it would have to break the speed of light in order for that to happen. So in order for the speed of light to remain the same, time must change when observed at a distance..

[@ardiankotori3149]

Thank you for this elegant explanation. Thanks to this I’ve got more thirst for knowledge and feel proud of myself. More beautiful videos like this please.

[@starryfolks]

Very intuitive. All videos are amazing. Well done.

[@gyanendrasingh4471]

Phenomenal video. I have watched several videos explaining special relativity, but I would rank this the highest in terms of ability to tech and make one understand the concept

[@parminderkaur4438]

OMG I HAVE BEEN TRYING TO UNDERSTAND THIS FROM SOO LONG!!! THANK YOU THIS IS THE BESTEST VIDEO

[@augijyotbali2131]

Try to improve your Grammar too ,btw which place from India are u,

[@parminderkaur4438]

@@augijyotbali2131 can you please point out my mistake cause I don't see any

[@augijyotbali2131]

@@parminderkaur4438 you had written form and bestest aint a word "best" is the superlative of "good"

[@parminderkaur4438]

@@augijyotbali2131 OMG update ur vocab u don't know this also bestest is a word (though informal) go search it on Google AND form was written by mistake I meant from

[@augijyotbali2131]

@@parminderkaur4438 whatever first know that grammar doesn't include ",slangs"

[@dawnmcqueen-shaw9693]

As I continue to watch this, it is seriously blowing my mind with "...in the past" with light ray ...in the future" light ray portion. I really never understood until I this video, it was explained so well! Thanks to my nephew for this link 👍👍

[@TheBrickagon]

This helped me to clarify some ideas :D

[@MominulShaon]

An absolute masterpiece. Thanks, uploader!

[@SandTheDoor]

6:57 This animation made me realize that length contraction is analogous to rotation in 4D spacetime. Holy shit.

[@tophan5146]

Wow

[@pvc988]

Does that mean that from photon's point of view, it travels from one point to another instantaneously? And, does it "see" the world around it as a flat projection in the direction of its movement?

[@ScienceClicEN]

Exactly yes!

[@EskoLuontola]

3:08 The flashlight example has a *fundamental problem:* The person holding the flashlights will not observe the light hitting the wall, at the exact moment when the light actually hits the wall, but only after the light reflects from the wall and reaches the eyes of the person. Only light's roundtrip time can be measured. See the video "Why The Speed Of Light Is Unmeasurable " by Veritasium .

[@EskoLuontola]

The spaceship and 2 flashlights example will need to discuss that at what speed the light travels in different directions relative to the spaceship. I haven't done the math, but I'm guessing that the lights will hit the walls at different times, but the reflections from the walls will reach the person's eyes at the same time.

[@lostmarimo]

the more i learn the scarier it gets..

[@m67esteban]

Thanks!

[@FelanLP]

one question I always failed to answer/understand: The ship is moving relative to the planet and the planet is moving relative to the ship, depending on the piont of view. Therefor both are efected by the same efects relative to each other. but why is the ships time moving in slow motion if I watch it from the planet but not the planets time if I watch it from the ship? Wait. Do I have to compare the speed of each systeme on its own to the speed of light? If so I have several other/new questions.

[@FelanLP]

@silverrahul the fact that you can "time-travel" into the future if you fly at high speeds. If you would slow down from the perspective of the ship both systems times would match up again if you bring them back in sync. But that's not the case.

[@FelanLP]

@silverrahul I didn't said that slowing down the ship would bring both systems back in sync. The slower flow of time is the reasons why the ship is traveling into the future. Less time is past for the crew at the ship compared to the time here in earth. *But* if this would just be a visual thing and both systems would look slowed down in time if you watch them from the other system, both time dilations would cancel each other out AND you could also observe a "fast forward" time movement on the other system if both systems starting to get back in sync IF time dilation would just be an illusion. Idk what you mean with different magnitude of time dilation. If I'm moving with 20km/h relative to you, you are also moving with 20km/h relative to me. If we both are effected by time dilation we would both be effected by the 20km/h equivalent of time dilation. But it's not possible that both systems are effected by time dilation relative to each other. We can measure it by sending a clock in a plane around earth and comparing it to another stationary clock after said trip. It's irrelevant if you were watching the clock from the plane or from the ground. The clock who traveled around earth traveled through less time at the same time the stationary clock did. Even though the stationary clock was traveling the same way, just in the other direction, relative the the clock on the plane. And that's what my question is about. Why is that so? Why is one system effected by time dilation relative to another, but not the other way around? Is it because of every systems own relative speed compared to the speed of light itself what says his much each system is accepted by time dilation? But if so, what if I slow myself down compared to the speed the earth is traveling through space?

[@FelanLP]

@silverrahul I know what you mean. But think about it. If the clock is send by a plane moves relative to the stationary clock with some speed the stationary clock moves relative to the plane clock with the same speed but just in the opposite direction. According to you both clocks would, watched from the POV of the other clock, slowed down in time and also by the same rate. But this is what doesn't happen. If the stationary clock would travel slower through time as the clock on the plane, the clock on the plane wouldn't be behind the stationary clock after landing. And if both clocks would see the other clock effected by time dilation, both time dilation effects would cancel each other out. Because A it was just a visual effect, what it is not, or B both would be slowed down at the same rate during this procedure, what also doesn't happen because the clock on the plane is in fact behind the other clock after landing. Same procedure with spaceships.

[@FelanLP]

@llDarkFlowll I know. But that time slowes for both systems from the other perspective IS what makes me asking why the clock of one system lacks behind after both systems merged together. For example riding a train plane or Spaceship makes your atomic clock lack behind after comming to a full stop relative to the earth. This was tested by sending an atomic clock on a plane around the world and proved that moving makes your clock ticking slower. But why, if this phenomenon is relative, does this not affect the earth clock, if you look it from the ships perspectice. If you start from Earth (maybe for example even in the opposite direction the earth is moving round the sun, so that the ship were moving slower trough the overall space itself) why does its clock still lack behind after "remerging" with system earth? I understand the basic conzept behint time dilation but the concept itself is causing many questions to me no time dilation explonation so far were able to answer. Where am I wrong? Or can this get explaned without having to be a physicist in the first place? Or is this even a question for another phenomenon? I don't know. And I don't know where to look for an answer.

[@_Caose]

Every time I watch a video about such concepts, I genuinely want to cry.

[@falcz]

4:33 I didn't quite get why the back of the ship is in the future and the front in the past. Is it related to the acceleration that got the ship to that speed? I can't find a way to visualize it. Magnificent video tho, it's one of the best on SR.

[@jaideepshekhar4621]

It's a consequence of the constant nature of lightspeed. Since the observer stood in the center and shot both beams of light at the same time, for him, they should strike the ends at the exact instant. But, since the spaceship is moving forward, the only way light can strike both ends at the same instant, is if the time in the back is less than the time in the front, since light has to cover a lesser distance to reach the back end, as speed must be the same.

[@PranshuSRaghuvansh]

One of the best visual demonstrations of Special Relativity out there, made me subscribe. Gonna start the GR series

[@fraznofire2508]

Why is the rear in the future? This part feels like there is no explanation, otherwise good video

[@ScienceClicEN]

From the outside of the spaceship, the rear seams to be in the future because the light ray reaches it before the front, while the two events were simultaneous inside the spaceship.

[@fraznofire2508]

ScienceClicEN ooh that makes sense, thanks

[@slash196]

@@ScienceClicEN Neither of those are "in the future" any more than the light from a distant lightning strike is "in the future" relative to the sound of the thunder. The spaceship is entirely within the past light cone of the outside observer, but events inside the spaceship reach the earth observer in a different order than they reach the observer in the spaceship. Nobody's seeing the "future" of anything. I consider this to be a serious philosophical mistake that has led to a lot of really unnecessary confusion. There's a difference between a clock ticking faster and a clock being "in the future".

[@ScienceClicEN]

Actually no, the relativity of simultaneity is *not* a visual illusion (like the lightning strike). The spaceship is *not* within the lightcone of the observer, and that's precisely why you can have different slices of simultaneity. When you have two events happening outside your lightcone, the order in which they occur in your frame of reference is not important

[@slash196]

@@ScienceClicEN I didn't say it was a "visual illusion", that was just to make my point clear. Special relativity shows that simultaneity is not an objective property, but that has been overstretched to conclude that there is no such thing as the past and future. That's a conclusion drawn from sloppy use of the word "future". There's a fundamental difference between "This thing in the past that happened after another thing in the past that also happened" and "The future relative to me, here, now or you, there, then". And I would disagree that spaceship is not within the past lightcone of the observer. How on earth am I to observe it if it's not in my past lightcone? Again, this stems from a sloppiness in clarity about who is seeing what when and how they're entitled to divide up the universe. I'm not blaming you, this is absolutely typical of textbook special relativity. Certainly the math works, but the interpretation of special relativity on a conceptual level has gone horribly wrong and led to a bunch of rather obviously silly conclusions.

[@hardikmistry7058]

Salute man! Such an eye opening explanation to an ordinary engineering student. Thank you.

[@nikitanosov8159]

and that is why i try to get seated at the front of the plane.

[@ryszardderejko9754]

I have been struggling to understand time dialation, but this video finally made sense to me!

[@themoddingprodigy577]

The background music sounds like GTA V will load any moment

[@Jmcdion]

Blows my mind every time.

[@tupaicindjeke275]

SR is really Hard.

[@from0the0ashes]

Great video! Just one point - In your explanation of simultaneous events, it should be noted that while the back of the ship is ahead in time compared to front of the ship (relative to the observer on planet), the amount by which the back is ahead of front remains constant through time. So a twin in the back will be older than a twin in the front, but they will both age at the same rate (again from the planet observer frame of reference). The first time I saw your video, I interpreted it that you were saying that time flows at different rates at different points in the ship (relative to planet observer), however this is not what you were saying at all.

[@surendrakumargaraga9169]

Great animations and content. the only channel in which General relativity and space time fabric made sense.

[@avtandiliturdziladze7184]

Thank you very very much, this channel is my favorite one! I am chemist and it gives me motivation to study Physics.

[@AndyLundeen]

This video was awesome. Shared it with my mom and dad who aren't well-versed in physics, and I was able to provide some color commentary for a night of a LOT of fun and learning!

[@tekblade]

Wow, your parents must be so proud...of your siblings.

[@Kazami101]

@@tekblade how rude

[@vesuvandoppelganger]

It is possible to derive 2 contradictory time dilation equations. The first paragraph below describes the situation with Sally aiming a flashlight straight up and down so that Sally sees the light moving straight up and down and John is outside the spaceship and sees the light forming a triangle with the floor of the spaceship. The second paragraph describes Sally aiming a flashlight towards the left while the spaceship moves to the right. Now the situation is exactly reversed. Sally sees the light forming a triangle with the floor and John sees the light bouncing straight up and down. Sally is in a moving spaceship. John is outside the spaceship. Sally is moving to the right at .6c. The height of her spaceship is .8 light-seconds. If Sally has a light clock with the light bouncing straight up and down the light will make a 3-4-5 right triangle from the viewpoint of John. If the change in time for Sally is delta T_o and the change in time for John is delta T then the following equation can be derived: delta T = delta T_o/((1-.6^2)^.5). So .8 seconds for Sally = 1 second for John. Now Sally has a light clock but this time she is holding a flashlight at an angle of 53.13 degrees above the horizontal and pointed to the left. Now the leftward movement of the light exactly matches the rightward movement of the spaceship from John's viewpoint. Now the light is bouncing straight up and down from the viewpoint of John and the light is making a 3-4-5 right triangle from viewpoint of Sally. If the change in time for Sally is delta T_o and the change in time for John is delta T then the following equation can be derived: delta T_o = delta T/((1-.6^2)^.5). So 1 second for Sally = 0.8 seconds for John. The 2 equations are in direct contradiction to each other. Special relativity is falsified.

[@muizlodhii]

The most simple explanation of the most complex concepts of time dilation & length contraction. Bravo!

[@alwaysdisputin9930]

Why is the rear of the ship is in the future? u can't say. Therefore I think this explanation is too simple i.e. it has been dumbed down

[@Dr_Hope]

The best explanation video of its kind on KZbin!

[@TheGiulz76]

congrats. best video on SR ever seen so far

[@bvsankar]

The best videos on SR and GR. Congratulations!

[@Ricardofromage]

What a fantastic channel to have found, watched 3 vids so far, fascinating, very well explained and produced, kudos 🙏

[@linhmaiinh4934]

why this channel haven't reached 2mil yet?

[@arundeeplotus4539]

wonderful! This is the video out of so many that explain relativity that I have understood perfectly. Finally I understood the core principle behind how relativity works. It's the principle 'the speed of light is constant' that makes relativity. Even from a moving vehicle, the speed of light doesn't increase like a ball thrown in a vehicle moving at a speed will add up with the speed of vehicle. but what if the speed of light also adds up with the vehicle speed? then the speed of light increases more. But who made research on it?

[@jackmahero96]

Wow! this's so educative.. Relativity, the mother of sciences!

[@MathPhysicsEngineering]

Absolutely incredible video, it deserves 10M views at least!

[@AdamCarter-n9o]

This is easier to explain with timing the bouncing of a tennis ball from the ground to back to the hand of someone on a moving train and an observer standing still outside the train measuring the time of the same event. The person on the train may time the event as .5 secs, while the observer, standing still out side the train as .6 secs. Because the ball on the train is covering more ground.

[@Accell_Auto]

Other channels tend to mystify the theory of relativity and evade clear explanations so that they can go back and forth on the topic and maintain viewership.

[@frutonana]

1:37 it affects the wavelength. Light expands or compress depending on our position, so we can say that light motion through us occurs with different pace (speed).

[@bhuvanjhamb2728]

Glad to find this channel buddy! Your content is simply too good.

[@DontMindRick]

this channel is too much underrated..

[@shadesmarerik4112]

One can very well calculate the movement of an object with constant acceleration in SRT. Its a false statement that u made, that srt doesnt apply to accelerations. But aside from that: great video! The reason why velocities over light speed isnt possible is causality, and not only finite amounts of energy.

[@ScienceClicEN]

You are completely right yes

[@ahuman32478]

5:25 Correction, the person on the right isn't younger, because you can't go back in time, you can only slow your travel through time. The person on the right would instead age SLOWER than the person on the left. The person on the right will be younger than the person on the left, but their final age won't be smaller than their starting age.

[@ScienceClicEN]

No beware there are two different phenomena at play. What you are referring to is time dilation, and you are perfectly correct that the person can't get younger due to time dilation. However here the video refers to something else : the fact that time gets "tilted" when you switch frames of references, such that synchronized clocks become desynchronized. This is explained more visually in my video about visualizing time dilation.

[@Cyfiero]

This is overall the best explanation on this topic I've found so far! Although unfortunately I still feel like there are a few gaps for me. One question I have is regarding the section on time dilation. I understand that for the stationary observer on Earth, the light would have to travel a longer distance to hit the ceiling. However, when other sources explain this using similar examples, they claim that the observer would actually witness the light moving in a zigzag pattern as a result. I always found this really confusing because I can't imagine I would actually see a zigzag motion as a stationary observer looking in. Your animation shows instead that the longer distance the light has to travel to the ceiling manifests as the light beam taking a longer time to directly hit the ceiling, as time itself slows. Your animation makes more sense to me, but I was wondering if it is telling us that that is what we would actually observe instead, as opposed to a literal zigzag motion.

[@aniketeuler6443]

That's a great explanation sir 👍👍👏👏👏👏👏

[@vesuvandoppelganger]

The triangle of lights paradox. There are 3 lights in the form of a triangle. A, B, and C are lights and are stationary with respect to each other. S1, S2, S3 are spaceships. S1 is moving from B towards A. S2 is moving from C towards B. S3 is moving from A towards C. A, B, and C flash simultaneously in the frame of reference that is at rest relative to these lights. So in the frame of reference of S1, A flashes first followed by B flashing. In the frame of reference of S2, B flashes first followed by C flashing. In the frame of reference of S3, C flashes first followed by A flashing. So the sequence of flashing is A, B, C, A. But wait! A flashed first. How can it flash last? How can A flash both first and last? It only flashed once in the frame of reference that is at rest relative to these lights. Therefore there is a paradox.

[@WallyMast]

Is time dilation only a *perception* by the stationary observer, or is it a physical change? E.g. if you fly an atomic clock around the planet, is the clock only *perceived* to slow down from the earth, or when you bring two initially synchronised clocks back together, while they show a permanent time difference? If so, does this mean that the vibration frequency of the clock atoms has *physically changed* due to kinematic and gravitational effects?

[@ScienceClicEN]

Good question. Yes, if you fly the clock around the Earth, when it comes back you will compare that the clock that stayed still has aged a little more. This has actually been verified experimentally with atomic clocks in airplanes. However saying that moving "changed" the way the clocks tick would be misleading : it's only that the two clocks have followed different paths through spacetime, and since these two paths are of different lengths, they measured different travel times. This will be clearer when my next video drops it's precisely about this

[@hhpoa]

After watching many videos and comments, it is the first time I see someone asking what I have tried fruitlessly to ask for some youtubers. It is the first answear too. But let's go to the other video by ScienceClic.

[@twally87]

Great explanation. Close to the end you describe how it is impossible for a mass to travel through space at the speed of light relative to another object because it would require infinite energy. Equally interesting, coming from special relativity, is that if in theory a mass *could* travel the speed of light, it would not experience time passing at all. If sometime in the distant future we could invent an Alcubierre/warp-drive that travels the speed of light, we could eliminate the time passed for passengers, even to distant stars and galaxies. Only problem of course being it would also consequently eliminate meaningful communication and cooperation between those passengers and those who didn't make the journey: hundreds, thousands, or even millions of years may have passed for everyone else, and all of civilization could be different or disappeared altogether, but quite literally in the blink of an eye for the travelers.

[@sarkauz]

This is my mind spa, absolutely love it. And for the background track I can listen to this over and over for days

[@Villager_art]

You're so great! Sir what's a best explaination ❤❤❤❤❤❤❤❤❤❤

[@marishkagrayson]

I enjoy these explanations of time dilation and lack of simultaneity, but the problem I have with these examples is they are for macroscopic effects: We and everything are “presumably” quantum, thus everything interacts with the speed of light so locality and spacetime geometry is different for a quantum object. Gravity may be a result of entangled objects. Local interactions like the moving spaceship example means that a signal sent will reach both ends of the spaceship in the same reference frame. A distant quantum object would perceive that signal as delayed from the “front” depending on the direction of motion of the entangled object (in this case a macroscopic spaceship). It would be interesting to map quantum objects in terms of relativity because it makes more sense to me to cancel out macroscopic features like time dilation and gravity and understand the perspective of a quantum object instead.

[@diamondsalam6894]

Best explanation I've ever had🔥

[@judyreyjumamoy]

best science teacher to date

[@salehrezq]

How can I imagine all these phenomena take place at the same time?! For earth observer, a) Light hit the side moving opposite to the light source first, because the rear wall is in the future, the front side is delayed. b) Length construction of the ship because the rear part is in the future, the front side is delayed to the past. c) The clock generally ticks slower inside the ship from earth observer perspective.

[@nigelgriffiths5747]

I always thought that time duration would ultimately prove 1 day that the multi universe is true. Physics is very complex and big I mean a big picture. Fascinating video love it, top marks, great stuff.🤸‍♀️😜🐎🤪🧐😇🤭👍

[@schmidtschmidt2776]

I can't understand it please help me. At 3:40 when you say: let's look at how it is "PERCEIVED" by the observer in the planet... what do mean by perceived? Do you mean the experience that occurs when the photons reach the observer? Or do you mean the mental experiment of imagining these events from an external frame of reference without really receiving photons?

[@dalejames486]

Good question

[@josebarria3233]

I was thinking about the rear and front of the ship being out of sync, when you made me remember the time formula from Lorentz transformations has an "x" in it. Thanks you gained a new sub

[@lucapianca2593]

Brillant animations! I will share your videos with my Italian friends, nice job!

[@ScienceClicEN]

Grazie Luca !

[@hamzasusam3790]

In the ship two opposite side light experiment, we think observer see them at same time is a paradox but actually it is not. If observer sees them, two lights has to travel back to observer. This makes two lights to travel same distance. For backward light it is for instance 49m + 51m and the forward it is 51m + 49 m. If observer needs so see different results then the ship needs to accelerate. If the ship is accelerating two lights would reach the walls different time.

[@spec_wasted]

I've read this in a book called Space Time and Einstein, but was having hard time visualising it Thanks a lot

[@theos4960]

Best explanation of SR!

[@alwaysdisputin9930]

Why is the rear of the ship is in the future? u can't say. Therefore I don't think it's a very good explanation

[@TheLethalDomain]

It's almost like time is just a universal conversion quantity for energy to exist at a given point in space, and it's connection to causality provides the speed limit that causal links may exchange new information without a paradox. At the point that perhaps the energy of electromagnetism matches that of gravity, there is only a single point in space-time upon which all else may spill out and appear as an evolving system when observed from a different interval of mass. I'm not sure what this field would be called so I will call it a Planck field. From our perspective, it would be an expanding universe. In terms of General Relativity, we would call it a white hole whenever time explicitly flows forward from it. This would exist as one hypothetical particle existing as a probabilistic outcome of infinite possible universes. So imagine looking at the universe from the "outside." There would be no forward or backwards, just a probability density for what ends up actually happening.

[@wilsongomes3360]

Wonderful explanation

[@aden6427]

At around 8:20 in the vid, would the light emitted by the flashlight not have inherited the same motion of the spaceship (to the right)?

[@vesuvandoppelganger]

"In May and November, the Earth is moving at "right angles" to the line to Algol. During this time we see minima happening regularly at their 2.867321 day intervals. However, during August, the Earth is rapidly moving towards Algol at about 107,229 km/hr as explained on my How Fast Are We Moving? page. (The Earth moves approximately 202 times its own size in one day.) So in 2.867321 days the Earth moves about 7,379,039 km closer to Algol. _But the varying light from Algol doesn't know this - its light waves left Algol 93 years ago and are travelling at a constant speed._ The result - we "catch a bunch of minima early" during August as shown on Chart 2. Exactly the opposite happens during February - the Earth is moving away from Algol that fast and it takes longer for the group of minima to reach us so we see them taking longer between events. How long? 7,379,039 km divided by the speed of light 299,792.458 km/sec is 24.61382 seconds. So in May and November when we are not moving towards or away from Algol - the period seems constant. It is our rapid movement towards or away from the events in August and February that causes the timing differences." I assume that light is passing the earth at c when the earth isn't moving towards or away from Algol. In February the earth is moving away from Algol and the time between the eclipses is 2.8675875347 days and the light is passing the earth at 186,265 mi/sec. In May and November the earth is not moving towards or away from Algol and the time between eclipses is 2.867321 days and the light is passing the earth at 186,282 mi/sec. In August the earth is moving towards Algol and the time between eclipses is 2.8670608912 days and the light is passing the earth at 186,299 mi/sec.

[@dijkstra4678]

This should be the standard at every learning institution