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

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

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!

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

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

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

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 :)

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

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.

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.

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

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.

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

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

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!

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

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

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.

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

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.

very impressive! Glad that I've found you

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 ❤

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 👍👍

An absolute masterpiece. Thanks, uploader!

Very intuitive. All videos are amazing. Well done.

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

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

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

This channel is gold!

This is sooo underrated😥 The best explanation ive ever heard

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

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

This helped me to clarify some ideas :D

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

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)

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.

This channel is highly underrated.

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

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

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

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?

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.

A superb explanation of special relativity. Love the spooky sci-fi instrumental music in the background too!

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!

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.

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

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

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

The background music sounds like GTA V will load any moment

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

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

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

SR is really Hard.

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

This one video cleared out so many questions of mine. Kudos to the awesome creators!

Wow. Fantastic explanation. Love your videos!

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

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.

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

this channels general relativity video helped me finally understand it after watching so many videos and reading so many book explainations that i thought i would check out their special relativity one and it did not disappoint! thank you!

Crazy stuff! I hope more videos on this come out, as it takes some time to understand... Still, you explained it very well!

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

The best explanation video of its kind on KZfaq!

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

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?

Awesome video, great explanation!

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

Blows my mind every time.

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

Hello, congratulations for your videos! I wonder if it would be possible to arrange a series dedicated to the Maths of Special Relativity? Thank you so much!

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..

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

What a great video with explanation. 👍

Amazing video, thank you

Sometimes I have this question like you said about the example of the passenger in the space ship but how can one look at two different directions at the same time. But the example given by Einstein of a passenger in a train in that example it's about the effects of two thunderbolt like light and sound. So in this case is it about the reflection of light? I don't know.

Wonderful explanation

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

The best video Thankyou soooo much man

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.

congrats. best video on SR ever seen so far

Awesome videos Subscribed to your channel 👌👌👌

Best explanation I've ever had🔥

Your content is amazing

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

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.

So if I understand correctly, the front of the ship is behind in time compared to the back because the information from whatever is in the front of the ship reaches the observer before whatever is in the back, making it seem like the front is behind in time, is that right? But it would only be noticeable if the ship were moving really fast, like a significant percentage of light speed, right?

@ScienceClic English @6:34 Can you make a graphical representation of the ratio between the moving speed of an object and its contraction percentage (using accurate data)? You did a similar representation regarding the ratio between the speed through time vs the speed through space (it resulted in a cercle - see the "We all move at the Speed of Light" video). I wonder if analyzing and comparing the 2 graphs would help us find something interesting? Thanks!

Great video, thanks!

7.00 is fantastic. Thank you

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 .

Hello from Brazil! This vídeo -- as well all the others, btw! -- is awesome! But, at the 11:09 mark, it aays c = 299,792,458 m/s, when, in fact, the right value would be km/s. Anyway, keep up the good work!

I like your channel very intresting topics that you are talking about

Superb, Only now I can exactly learn both special and general relativity principles👍🏻

why this channel haven't reached 2mil yet?

very good explanation

Mind browing explanation 😮😮liked it most 😊😊

Hello, I always enjoy your videos and mostly are very educational. I do have a question for you here in relation to your video . An artificial uniform gravitational field is created by the ship which is caused by the motion of the universe,i.e,stars and galaxies ( einstein's equivalence principle). This gravitational should curve spacetime around the ship, but it is not real gravity.( created by mass-energy) So, is there a real spacetime curvature around the ship. Time dilates, we know that. Many physicists are confused on this subject. As a PHD physicist ,me too honestly. Appreciate any comments..

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).

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.

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?