Nature of Time and Simultaneity

Nature of time and simultaneity according to Albert Einstein's Theory of Relativity.

[@EugeneKhutoryansky]

To see subtitles in other languages: Click on the gear symbol under the video, then click on "subtitles." Then select the language (You may need to scroll up and down to see all the languages available). --To change subtitle appearance: Scroll to the top of the language selection window and click "options." In the options window you can, for example, choose a different font color and background color, and set the "background opacity" to 100% to help make the subtitles more readable. --To turn the subtitles "on" or "off" altogether: Click the "CC" button under the video. --If you believe that the translation in the subtitles can be improved, please send me an email.

[@SazzadHissain]

Hi Eugene, at 01:50 you said from Adams perspective the all three clocks are reading exactly same time. But I think in reality they will be a bit different even with Adams perspective. The 1st and the 3rd ships clock will be a bit different than the 2nd ship where Adam is seating because the ships already had traveled far ahead and lags far behind of Adams positions respectively. However, the rate of all three clocks will be definitely same as the speed of all three ships are now same. Correct me if I am wrong. ❤❤

[@EugeneKhutoryansky]

@@SazzadHissain I am always referring to what each observer believes to a clock to be reading, after the correction is applied to take into account the time it took the light to reach their eyes. Hence, this is not really about what they see with their eyes, but the space-time coordinates according to their coordinate system. Different observers have different space-time coordinate systems. Thanks.

[@SazzadHissain]

Hi Eugene, at the time the first ship goes ahead of Adams own ship would there be a bit change of time in both ships (Adams ship and the first ship) clock or not as the distance is so long? Just asking to realise the theory precisely for myself. Thanks.

[@EugeneKhutoryansky]

@@SazzadHissain From Adam's point of view, all three ships are standing still, and the clocks on the three ships are always reading the same time.

[@EugeneKhutoryansky]

In case, you have not already seen them, I also uploaded several other videos recently. As always, for each video that you like, you can help more people find it in their KZbin search engine by clicking the like button, and writing a comment. Lots more videos are coming very soon. Thanks.

[@ivanmakaris8986]

Eugene Khutoryansky Love your videos on relativity. You are one of the only one making these on KZbin. MORE!!!

[@ctrinity]

Eugene Khutoryansky I second Ivan Makaris. More!!!!

[@veezee9256]

Eugene Khutoryansky me third, seen them all, keep'em coming. TY

[@KarnikBadvaganyan]

Can someone expain me why exactly this is happening. They appear to watch different events when sara is standing still and adam is moving. Why for adam right structures fall first?

[@EugeneKhutoryansky]

Karnik Badvaganyan This is necessary so that both Adam and Sarah will both measure the same speed for light. I go into more details about this in my main video on Einstein's Theory of Relativity.

[@mechkota]

this channel is gold!

[@EugeneKhutoryansky]

Thanks for the compliment.

[@VeganoGuy]

Thanks Eugene for these videos. It took me several views of all of them to feel that I had a good grip on the concepts. I have no formal education in the topic and I would certainly recommend your videos to anyone who is interested.

[@EugeneKhutoryansky]

Thanks. I am glad that you like my videos.

[@dariushmilani6760]

Thanks Eugene, Great video and a great back ground music. Keep up the good work. Thank you for sharing.

[@inertiaforce7846]

Another thing I love about your videos is the music. The classical music playing while you describe all these crazy alien effects of space, time, distance, simultaneity, and inertia, makes me laugh. Hahahahaahahahahahahahahahahahahahahaahahaahaha.

[@miradeem9479]

I have always loved your videos. You explain everything so nicely.

[@stigrynning]

Does this mean that the age of the universe isn't the same everywhere and for everyone?

[@dromulus18]

+Stig Rynning yes. and even crazier: from a photons point of view there is no big bang and the whole universe is still in the same location

[@mtcovington1]

It's only your perspective that changes. But the Universe still moves at the same speed regardless of our opinions. Hope that helps!

[@alephmorricone7207]

yeah but what is to say that except the biological beings no other entity has the reception of what is known as time? so in a way the frame of the multi verse never starts nor ends coz there is no such thing as time which helps navigate our perception from one point to the another

[@blacktigershearthstoneadve6905]

@@alephmorricone7207 It is even more weird actually. Since without an observer nothing really exists (or rather exists in superposition state) and there is only one observer (you) as other people are also observed objects from your point of view... well, because of it, nothing really exists beyond your observer range. In fact nothing really exists that you knew at some point, but then forgot about, it basically just disappears and may reappear in a different form as long as this form does not contradict information you currently have.

[@sylvainbrosseau6239]

I don't know any other physicist who dared explain that particular aspect of relativity. I think other physicists learn physics through Eugene's videos. Jokes aside, Eugene's videos and coverage of physics are unmatched.

[@EugeneKhutoryansky]

Thanks for the compliments.

[@minutlight]

Great video. Very well understood

[@tiagofranca2660]

One more amazing video! Thank you!

[@EugeneKhutoryansky]

Theenerd ジェームズ Thanks. I am glad you liked it.

[@brajeshnandanjha1146]

Thanks sir, My 12 year son likes and wait for your video and explain me these things in very easy way. Thanks once again.

[@EugeneKhutoryansky]

Brajesh Nandan Jha, that's great to hear. I am glad that your son likes my videos. Lots more videos are on their way.

[@QNeona]

I’d love to have an update on your son

[@dev_ratn_29]

@@QNeona me too.

[@luizcantu]

Your videos are very clear, with these examples I have understood a lot of concepts that othewise would be too confusing. Thank you! Keep up the good job

[@EugeneKhutoryansky]

Luis Cantu Thanks for the compliment. Yes, lots more videos are on their way.

[@Tiago211287]

So can I already be dead from an alien perspective elsewhere?

[@dromulus18]

+Tiago Bruno Castro jup

[@lexgotham]

And not born yet from somewhere else's perspective.

[@kennethlippencott8693]

Well, your lifespan is absolute tiny. To understand the full implications of this, there are other reference frames where the earth has not even formed yet. There are other ones for which our sun has not formed, and is still a cloud of cosmic dust.

[@garrytalaroc]

only when you are not born yet

[@EverythingInane]

@@robinnapoleon3065 schrodingers cat works on another principle, but this one is correct, since relativity implies that all of time exists concurrently. So I guess you can potentially have a cat who's both dead and alive at the same time twice. Well, if schrodingers cat experiment really works that way in reality at any rate..

[@TheRolemodel1337]

The "Train in a Tunnel" thought experiment would be a nice visualisation aswell. great vid :)

[@EugeneKhutoryansky]

***** Perhaps I can include the train in a tunnel paradox in a future video. I had considered showing it in this video, but I decided against it because that would involve explaining length contraction, and in this video I just wanted to focus on simultaneity, as this is something that a lot of people have been asking me questions about. And thanks for the compliment about the video.

[@StephenGillie]

"Now" is the integral of local gravity variations across time. Areas of low gravity are hills in this graph, and high gravity areas are as valleys. And so local gravity is the derivative of this slope at different points.

[@oleg5730]

AS usual ur very good explanation. Its interesting that since there can not be an absolute "same time and space" from our perspective, since as humans we always moving relative to each other ( even when just sitting and speaking to each other, we still move a few nm coz breathing, shiting, eyeball movement, etc). so we technicaly never meet same person with same atomic structure as before, its always slightly altering not only because of biological reasons but because of relativety.

[@joet7830]

Great vids! Really love them. Keep up the good work!

[@EugeneKhutoryansky]

Joe T Thanks. Lots more are on their way.

[@vanderkischk]

Excellent videos!

[@EugeneKhutoryansky]

Erik Vanderkolk Thanks. I am glad you like them.

[@MadHatProduction017]

Our world works in a beautiful way... thanks for showing that to us

[@EugeneKhutoryansky]

MadHat Production Thanks.

[@dariushmilani6760]

Thank you sir, That is what I thought but was not sure. All the best.

[@vijayakumarhiremath4288]

Wery well narration madam, thank you,

[@EugeneKhutoryansky]

Thanks.

[@Delibro]

I love the narration, Kiras voice is both good to follow and pleasant and so distinct. "muuch more information ... ... when new videos are reddy"

[@EugeneKhutoryansky]

Thanks.

[@prakashpaudel2708]

Marvellous video again!!! Eugene, I wanna see how you look? How can I see your face? in your original video to explain time dilation, you said light pulse after reflecting from mirror reached Adam's ship at different times for Adam and Sarah. then why didn't they agree that it reached Adam's ship at the same time. what is the basic difference between mirror video and this three ship video?

[@TheThePinkPrincess77]

Great video that helps sort out the confusing stuff. I have a better understanding of the law, but I don't understand how they were derived, can't wait to take upper level physics classes soon!!!

[@EugeneKhutoryansky]

TheThePinkPrincess77 The derivation of this is just based on the principle that all observers will measure the same speed for light, even under the assumption that they are standing still. When Adam fires a light signal to the two other ships, from his perspective, they both receive the signal at the same time. From Sarah's perspective, the left ship will receive the light signal first, because it is moving towards the signal, whereas the right ship is moving away from the light signal. Since Adam and Sarah must agree what the clock on each ship is reading when it receives the light signal, this means that Adam and Sarah will disagree on whether or not the clocks on the left and right space ships are reading the same time.

[@vinnv226]

Great video as always, Eugene. I've been thinking about this video in particular and am having some difficulty reconciling a few things. For example, suppose that I am near a concrete wall and I throw a ball at the wall, which then hits the wall and bounces back to me. Then a certain observer who is moving relative to me could see the ball hit the wall before I throw the ball. How is it possible for them to see the ball hit the wall, and then to see me throw the ball? How can they reconcile this sequence of events?

[@EugeneKhutoryansky]

vinnv226 For another observer to see the ball hit the wall before you throw it, he would have to be moving relative to you faster than the speed of light, which is not possible according to Einstein's Theory of Relativity.

[@vinnv226]

Eugene Khutoryansky Ah I see. So there are certain pairs of events A and B such that every observer agrees that A occurred before B? What distinguishes these types of events from the kinds of events in the video, where different observers disagree about the order of events?

[@RicardoSilva-zd9nm]

In this case A (you throw the ball) causes B (the ball hits the wall), therefore there is an order in which the events occur, the order of causality

[@EugeneKhutoryansky]

You can help translate this video by adding subtitles in other languages. To add a translation, click on the following link: kzbin.info_video?ref=share&v=ruRrVWHcgws You will then be able to add translations for all the subtitles. You will also be able to provide a translation for the title of the video. Please remember to hit the submit button for both the title and for the subtitles, as they are submitted separately. Details about adding translations is available at support.google.com/youtube/answer/6054623?hl=en Thanks.

[@stenarsk6877]

Beautifully simple explanation of physics + Classical Music. Pure gem

[@EugeneKhutoryansky]

Thanks.

[@stenarsk6877]

@@EugeneKhutoryansky No, I should say thanks :)

[@b00gi3]

Great as usual ! keep going .

[@EugeneKhutoryansky]

+SixSixSix, thanks. Lots more videos are coming.

[@physicslover1950]

Oh wow 😨 This is mind blowing. My mentor! Will you please make a video on this senerio and explain this in terms of Minkovski space-time diagram?

[@israelg99]

Amazing job! Thank you for uploading these!

[@EugeneKhutoryansky]

Thanks. I am glad that you liked my videos.

[@cgaccount3669]

It seems like with gravitational lensing, relativity, dark matter and energy, quantum weirdness that it's hard to say anything we see is like we think it is. I'm amazed how astronomers can even make any sense of their observations

[@Imran52Feb]

It is so counterintuitive but true ! Thanks . It takes time for the concept to sink in. Threre is no possibility of c-v or c + v here because in the speed of light there can not be any addition or subtraction.

[@Daz19]

Thanks for the video, is there a way to speed it up?

[@stepheneubanks8814]

love the videos keep it up

[@EugeneKhutoryansky]

Stephen Eubanks Thanks. Lots more videos are on their way.

[@user-og6ol2im7v]

The cat driving the mini cooper is my favorite event.

[@Fixundfertig1]

How do you match this with the Big Bang Theory? Theoretically, where and when happened the BB? Can every observer agree with that?

[@ctrinity]

Thank you so much for making this video, Eugene!

[@EugeneKhutoryansky]

carol h Thanks. I am glad you liked it.

[@ctrinity]

I like them all, Eugene. Tagged you on my FB wall on this one. ;)

[@EugeneKhutoryansky]

carol h Yes, I saw that. Thanks.

[@XtroTheArctic]

YAAAYY!! Now we have realistic explosion effects :)

[@martijnbouman8874]

As always, great video. I have a question about this: Would it be possible for an observer at a specific location in space to determine the maximum time any fictional observer being at his location (but travelling at different speeds) would argue has past since the moment of the Big Bang? If this were the case, then one could define a 'Universal time' with this, violating the principle you discussed in your video. (People would still differ in their experience of time, but at any location everyone could agree on this 'Universal time', so one can place clocks at any location that tell this 'Universal time'. People at different locations would see this 'Universal time-telling clocks' running at different rates, sure, but they will just say that the Universal time is not ticking at the same speed for them in different places.) If this were not the case, then there could theoretically be particles that experienced an infinitely long period of time since the moment of the Big Bang. Where are my mistakes?

[@UltraTM]

Martijn Bouman You could once set these clocks up but after moving around a little they would slowly but surely get out of sync, making them useless.

[@Aztecu818]

Your videos are awesome, interesting, and easy to understand. :D

[@EugeneKhutoryansky]

Aztecu818 Thanks. I am glad you like them.

[@simoputtonen2799]

Another amazing video! Wish you had more subscribers :)

[@EugeneKhutoryansky]

Simo Puttonen Thanks for the compliment about the video. Hopefully there will be more subscribers as I continue to upload more videos.

[@bartkwezelstaart9306]

Eugene Khutoryansky Don't give up if it starts slow, it's not a linear process. Maybe you could ask at the end of every video to like, subscribe and to share it on facebook aswell.

[@alexandrugheorghe5610]

Eugene Khutoryansky You could also write the address to your channel instead of letting Mrs. (?) Vincent say "on this channel", or leave the voice but print the URL. I don't want to give off competition but you could take some inspiration from other popular channels like PbsSpaceTime and/or SciShow space.

[@theuniverse5096]

Is wish the lady wouldn't take too much time.between her narrations.Awesome video.I love it.All of.ur vids are Awesoome.I understand very clearly.thanks a lot

[@EugeneKhutoryansky]

I deliberately added the pauses between the sentences, so that people would have more time to think about each concept before moving on to the next one. Thanks for the compliment about the video. I am glad that you liked this video, and all my other videos to. Lots more are on their way.

[@ariav6582]

Well, you see, I'm a cyborg, and I'm programmed to take long pauses. I'm also programmed to accept blame.

[@alexandrugheorghe5610]

Kira V I LOVE you! Would you marry me? No, really! Great work and so many thanks! Especially the educational videos where concepts are summarized at each end of the mini chapter and also underlined again for the important points. Very helpful!

[@ariav6582]

Alexandru Gheorghe Aw, Thank you! :)

[@williamreidboyd2944]

Thanks for this. I love these videos!

[@EugeneKhutoryansky]

Thanks. I am glad you like my videos.

[@dariushmilani6760]

Hi Eugene, why is it that from Sarah's Perspective the clock on the left spaceship ticking faster that the one at the right? Best regards

[@EugeneKhutoryansky]

+Dariush Milani, it is not. They are both ticking at the same rate. It is just that one of them is ahead of the other, and the amount by which it is ahead stays constant. This is necessary so that both Adam and Sarah will measure the same speed for light, under the assumption that they themselves are standing still.

[@aliengrey1708]

An interesting thing about this is that neither person would be able to tell which frame the light was generated in, unless they could see the generators. If two flashes just appeared in one of the frames with no apparent source, as in the train and lightning thought experiment but in outer space with two astronauts and no train or ground, the person in the frame that the flash generators were located in, call him red astronaut, would see the flashes simultaneously and assume that the other person, blue astronaut, was moving toward one and away from the other, because they would see him lit up by the flashes from two different directions at two different times. The blue astronaut would see the two flashes occur separately at different times and would see the red astronaut lit up from both directions simultaneously, and assume that the red astronaut was moving away from the first flash and toward the second flash. Interestingly, if the flash generators were located in a third frame between the two astronauts and the red astronaut was moving in one direction from it and the blue astronaut was moving in the opposite direction from it at the same velocity, both astronauts would see sequential flashes and see each other lit up sequentially and on the same sides in the same order, nothing would appear to happen simultaneously, even though the flashes actually did in the generators' own frame, but nobody was there to see it.

[@viniciusfernandes2303]

Thanks for the video!

[@EugeneKhutoryansky]

Thanks.

[@ambikakumari96]

brilliant work like always! There couldn't have been better illustration

[@EugeneKhutoryansky]

Thanks for the compliment.

[@aslhan8254]

is there a specific reason about why the left side is always has a priority from sarah's perspective,is it about distance btw sarah and left/right side or am I just out of concept?

[@asdfghjklasdfghjkl4973]

please make a video on exponential series.

[@dariushmilani6760]

Hi Eugene, Can you explain why from Sarah's perspective the clock from the left space ship ticking faster than the one on the right space ship? Best regards.

[@EugeneKhutoryansky]

+Dariush Milani, it is not. They are both ticking at the same rate. It is just that one of them is ahead of the other, and the amount by which it is ahead stays constant. This is necessary so that both Adam and Sarah will measure the same speed for light, under the assumption that they themselves are standing still.

[@user-mt9uh2zv8m]

@@EugeneKhutoryansky sorry i think u cant understand relativity.when the space between the planes be high sarah will see diferences higher because light will reach in long time.

[@c34211]

I don't fully understand the part with the 3 spaceships. I get that it is necessary so they each receive the light at the same time, but I thought the clocks would only change if they were moving at different velocities or were in different strengths of gravity. Also, if the clocks move at the same rate but one is ahead of the other, when exactly does it get ahead? Does it just blink ahead at some point?

[@EugeneKhutoryansky]

They don't have to be at different strengths of gravity, but only at different locations along the gravitational field, even if the gravitational field is constant. When the spaceships accelerate, Adam will think there is an external gravitational field causing the clocks to run at different speeds. After the acceleration is over, Adam can recalibrate the clocks on all three ships to read the same time again. However, from Sarah's perspective, this gravitational field never existed, and the three clocks continued to read the same time as each other. But, when Adam "recalibrated" the clocks to read the same time in his frame of reference, Sarah will then see the clocks reading different times.

[@SilentAtheistt]

These are great videos. ;)So I have a question: if there's no universal time, why do we keep saying that our universe is about fourteen billion years old? We know it might be an edge of time but is it possible for anyone to say correctly that our universe is less or more than fourteen billion years?

[@UltraTM]

SilentAtheistt Well here we have the principle of "everybody is equally correct". From our point of view it is fourteen billion years old, but that must not be correct for all observers.

[@valentinopopa1686]

FRAME OF REFERENCE my friend

[@johnhowell7371]

That's a really good question!

[@N0Xa880iUL]

For us on earth 🌎

[@markostojiljkovic7100]

Just EPIC!!!!

[@EugeneKhutoryansky]

Marko Stojiljkovic Thanks. I am glad you liked it.

[@alexnes5534]

So, when an object moves, the time of the rear side of the object is slightly ahead compared with the time of the front side of the object.

[@whoatemyhummus]

Yes! New video by Eugene!

[@EugeneKhutoryansky]

whoatemyhummus And lots more videos will be available very soon.

[@massimilianodellaguzzo8571]

Hi Eugene Khutoryansky , nice video! (... all your videos are cute and interesting ) In my opinion the relativity of simultaneity is just an illusion, and I would like to explain my opinion to you by talking about " the correspondence principle ". The correspondence principle is related to Lorentz Transformations. (and to Galileo's Transformations) Maybe you know this principle, ... and there is something strange. .................................................................................................................................................................................................. The two main Lorentz transformations are:: a) x '= gamma * (x - v * t) b) x = gamma * (x '+ v * t ' ) The other two Lorentz Transformations: c) t '= gamma * (t - vx/c^2) and d) t = gamma * (t '+ vx '/c^2) are obtained from a) and b) In this case it is enough to consider the two Transformations a) and b), because c) and d) depend on a) and b) At low speeds the Lorentz factor (gamma) is a number very close to 1, and so the two Lorentz transformations a) and b) become: a_1) x '= x - v * t b_1) x = x ' + v * t ' Substituting a_1 in b_1 we obtain: x = x - v * t + v * t ' v * t ' = v * t t ' = t " THE CORRESPONDENCE PRINCIPLE " IS SATISFIED: x '= x - v * t t ' = t (At low speeds, Galileo's Transformations are obtained) And it is not the same, if we consider the two Lorentz Transformations a) and c) a) x '= gamma * ( x - v * t ) c) t '= gamma * (t - vx/c^2) At low speeds, the two Lorentz transformations a) and c) become: a_1) x ' = x - v * t c_1) t ' = t - vx/c^2 But if we consider large values of x, then t ' is not equal to t. (and Galileo's Transformations are not obtained) And the strange is that in this case it is enough to consider the two Transformations a) and c), because b) and d) depend on a) and c) In my opinion the main Lorentz Transformation is a) a) x '= gamma * ( x - v * t ) If a) holds, b) also holds. ... because b) is the symmetric of a) ... b) x = gamma * ( x '+ v * t ' ) The transformation c) depends on a) and on b) ( the Transformation c) comes later ! ) ... But if we consider a) and b) the Andromeda paradox (at low speeds) makes no sense. (because t '= t) ... The Lorentz transformation t '= gamma * (t - vx/c^2) makes sense if x = v * t Substituting x = v * t into t '= gamma * (t - vx/c^2) we get: t '= t / gamma. (and at low speeds t '= t) ... And the relativity of simultaneity is just " an illusion ". .............................................................................................................................................................................................................................. I think about the Lorentz Transformation c) t '= gamma * (t - vx/c^2) ... ... If t ' = 0 then t = vx/c^2, it's really strange!

[@yuko3258]

My ape brain is broken lol. The video was too good. This is a great channel!

[@EugeneKhutoryansky]

Thanks.

[@abcbadpassword]

Why does Sara see it as if the left clock is ahead of the right clock?

[@dpo357]

I'm confused by the segment from 1:00 to 1:30.. What I see is that the first particle (either left or right) "sends" the information about the spin to the second particle at the speed of light, instead of being spookily instantaneous, what am I missing here? :S

[@EugeneKhutoryansky]

+Diego Pomares, the information is being sent instantaneously. I was just trying to illustrate that which event is the cause, and which one is the effect, is different from the perspectives of the two observers.

[@yonathan6682]

when the buildings are falling, let's say that when Sarah is watching, and the buildings break at the same time, the debris from the two buildings collide with each other when falling and the debris ends up landing in a certain way. but from Adam's perspective, the buildings feel at different times, and therefore the debris doesn't collide with each other like in Sara's situation. so when the two look at the debris after the buildings are fully done falling, will it be layed out differently for the two observers?

[@UltraTM]

Yonathan Gamous No this is just because the animation is inaccurate, actually it would look even stranger than this. The right side of the buildings falls before the left side does, therefore distorting the whole image but that would be quite hard to follow.

[@UltraTM]

Yonathan Gamous Therefore anything colliding will happen the exact same way for both observers since the precise parts of the buildings that are colliding will be then pretty much at the same place in spacetime.

[@MrBottlecapBill]

The video just did a bad job of explaining it. The same events happen in the same order from both perspectives, they just happen slower or faster. You won't see one building fall completely apart and lay on the ground before the other does because the rate at which the debris falls also slows down. They just didn't capture that aspect very well in this animation. It's more like one person is watching a movie in slow motion, and another is watching it at normal speed. If you time the length of the slow motion movie it will be a longer movie, but the content remains the same as the content in the movie at normal speed. If this makes sense.

[@shankarvarma5759]

I need more videos on theory of relativity and about spacetime .,,,.,,,please upload!

[@ingridmittmannsgruber4320]

Good videos, but I find the music irritating. The only background music I liked was the one played to the video of quantum mechanics. The Viennese waltz is particularly annoying. Perhaps it could be toned down or replaced with something else?

[@Dyslexic-Artist-Theory-on-Time]

+Ingrid Mittmannsgruber Me too!

[@PranabPoonia]

could anyone clarify this ???.... Let us imagine that the all 3 Rockets are spaced at the distance of x Km . And they all are moving at the same constant speeds The rocket on the left most side is travelling in the opposite direction of light. Therefore effective distance would be less for the rocket to receive the light. Let us suppose it receives the light in 10 seconds. Now, the rocket on the right most side is moving in the same direction of the light therefore light has to travel more distance to reach to Right most rocket. Let us suppose that it receives the light in 11 seconds. It means the clock on the left most is running slower than that of clock on the Right, contrary to what has been described in the figure. * All this is from Sarah's perspective

[@EugeneKhutoryansky]

No, Sarah will see all three clocks run at the exact same speed. But, she will see the clock on the left as constantly ahead of the clock on the right by the exact same constant amount. This way, even though Sarah will see the left ship receive the light before the right ship, she will see both clocks read the exact same time when they receive the light signal. This is necessary because Adam will see both clocks read the exact same time when they receive the light signal, and what a clock is reading when it receives a light signal is something that both Adam and Sarah have to agree on.

[@ankitkaliraman5356]

@@EugeneKhutoryansky this is the only thing confusing me. What's the reason of that clock being constantly ahead of the right clock. And how being constantly ahead of the right clock fixes the problem that dude asked in this comment.

[@Antoine7881]

Do you plan on making any videos about black holes or gravitational lensing?

[@EugeneKhutoryansky]

Antoine OBannon Eventually I would like to get to gravitational lensing and black holes, but I have many other topics I would like to make videos on first. Thanks for the suggestion, though.

[@charlesbrightman4237]

Eugene Khutoryansky Is chemical element #119 (8s1) inside black holes? My analysis would say "yes".

[@deveshmathur634]

How can the clock on left spaceship be ahead of clock on right spaceship (2:09) unless the spaceships are travelling in a line and goes past Sarah one after another.

[@robertbrandywine]

That's exactly what I see them doing.

[@N0Xa880iUL]

Flew over my head. Especially because the ships have a constant velocity and are not accelerating.

[@EugeneKhutoryansky]

You may want to watch my main video on Relativity at kzbin.info/www/bejne/m6ecq6WqlMSfm8U

[@N0Xa880iUL]

@@EugeneKhutoryansky Thanks.

[@peterm.souzajr.2112]

please do a video on planck and speed of light relation

[@Cosmalano]

So does this have to do with events being either time-like, space-like, or light-like? And why does the clock on the left run ahead of the clock on the right? Regardless, thanks for the upload. I am studying the mathematics necessary for the theory relativity rigorously and your videos help to visualize the implication of this mathematics.

[@bencassidy45]

electrocat1 To *try to* answer your second question, it's to do with the speed of light from sarah's perspective. Look at the animation at 3:11; this shows adam's perspective, where both photons travel the same distance, and therefore take the same amount of time. In sarah's perspective, at 3:28, the left photon travels a shorter distance, and therefore takes less time than the right photon. The photon hitting the left ship's clock and the left ship being at 9 o clock are same-time same-place events, they are also same-time same-place events in Sarah's perspective as well. The same logic can be applied to the right photon, which also hits the clock when the clock is at 9 o clock, something also universally agreed upon.

[@Cosmalano]

Ben Cassidy thank you.

[@msundaram2407]

Why is that the clock on the left spaceship is always ahead of the clock on the right spaceship? Sorry if its a lame question..

[@EugeneKhutoryansky]

This is necessary so that Adam and Sarah can each think that they are the ones who are standing still, and still measure the same speed of light, and also both agree on what the clocks on each space ship were reading when they received the light pulses. I go into more detail about this in my main video on Relativity.

[@kzone1234]

Does it means if i stay at the core of the earth, i can receive electronic signals earlier than people in the surface, so that i can buy and sell stocks before everyone know it future price? I can be rich! (is LHC doing the same thing?)

[@EugeneKhutoryansky]

JJJacky, no. Even though different observers will disagree about if two events happened at the same time, it is still not possible to send information back in time to yourself.

[@anjanisingh5873]

What will happen if just after first set of ballon burst, Adam saves the second set of ballon. What Sarah would see in this case because she was supposed to see both pillars of ballon bursting at same time?

[@kisore20gp]

Please read simultaneity theory fully before watching this, so that u can think and analyze about the topic. Also 5:40 was a paradox for me and now it have been cleared by thus video

[@cameronspalding9792]

In order for a disagreement on wether 2 events happened simultaneously or at different tiles happens when the vector between 2 events in space time is space like

[@mikkel715]

When one cannot ask about "now" in another galaxy. How does that relate to Quantum Entangled particles collapsing their wave function instantaneously? Great videos👍👍👍

[@EugeneKhutoryansky]

I address the relationship to Quantum Entanglement in my video at kzbin.info/www/bejne/rGeYaIyirM1glc0

[@mikkel715]

@@EugeneKhutoryansky Great! to see the relativity explanation along Bell's Inequality. You should do a Loop Quantum Gravity video. Guess it will answer, Quantum moves and distortion to quantized fabric of space by "traveling" in relativistic point of views.

[@moubhattacharya9370]

Very important video

[@EugeneKhutoryansky]

Thanks.

[@sambaldwin8797]

The clock scenario assumes Sarah looks at the clock on the right first. Sarah needs to understand that it takes time for the spaceship on the left to reach the position of the spaceship on the right. If she notes the time of the clock on the right as it crosses an imaginary boundary, starts her stopwatch, then notes the time of the clock on the left as it crosses the boundary and adds the time of her stopwatch to that of the latter clock she'll be satisfied that the clocks agree.

[@EugeneKhutoryansky]

It does not matter which clock Sarah looks at first, and the other comments written above are also not the case. I cover this in much more detail in my main video on Relativity at kzbin.info/www/bejne/m6ecq6WqlMSfm8U

[@humbertojimmy]

What about events that necessarily *need* to be temporally tied? For example: could it be possible for someone to see a missile travel towards an asteroid and blow it, while someone else at another location actually see the explosion *before* the missile got to the asteroid? and if so, wouldn't that automatically *prove* the illusion hypothesis (since we know that it could only explode after being hit by the missile)?

[@EugeneKhutoryansky]

In order to see what you described, the observer would have to be moving faster than the speed of light relative to the objects he is observing, which is impossible based on our present understanding of physics.

[@UltraTM]

Jimmy David Additionally to describe what you could actually see in your described situation is that the time between the two events shrinks for your perception, therefore making it look like the missile was shot and *almost* instantaneously hit the asteroid, but you will never see the two events happen in reversed order.

[@Delibro]

Also important is, that such events that are temporally tied are (always?) also spaciously tied. And then all observers will agree on simultaneity.

[@humbertojimmy]

@@Delibro What i meant was different. I was trying to say that changing perception could in some cases be a paradoxical change in reality itself... I'll give another example: reality says that if you go faster you reach your destiny faster. But let's imagine a pilot on a far away galaxy travelling to Earth. His brother is sick and only has a month to live, and the pilot wants to get back in time to still see his brother alive, so... he steps on the "gas". He makes his calculations and the only way he can make it in time is if he travels near the speed of light. So he does. But as he travels at such speed, the universe around him starts aging faster than him... which means that, depending on the precise math, there will be a distance/speed (in)balance there that will make it always impossible for him to see his brother alive anyway (destroying the simple truth that going faster means you get home sooner). At this point it's no longer just "perception", we really are building tangible paradoxes. I'm sorry if i still wasnt clear enough. It's hard to explain it.

[@humbertojimmy]

@@EugeneKhutoryansky 6 years later, but since someone decided to ressurect this, i'll answer late (sorry). It's perfectly possible to see the explosion before seeing the missile hit it. All depends on light and perception. If the missile is travelling towards the asteroid from the opposite direction of the observer, the light reflecting from the missile travels longer than the light coming from the point of (incoming) impact. So, depending on precise distances, it's quite possible that the light from the impact reaches you faster than the light refelcted off the travelling missile. And there are other possible reasons, if there's a thick nebula in the way of the observer, that too could slow light down enough to allow another light source reach the observer first (even if the EVENT happened later).

[@tesla4623]

I don’t understand why the left spaceship’s clock is ahead of right. Can anyone help me out?

[@Guoenyi]

because eistein said c is constant for all observers. Simply, apparent velocity of light to sarah is lower than to adam , but distance is also shoter, ct=d, t goes down by advancing the last ship's clock, and d goes down to v remains unchanged. Hope that helps.

[@aghaanantyab]

the key is the speed of light is always the same for all observers. so if you shoot a laser, then the person who is moving really fast must see the speed of light is the same as the speed of light seen by you. therefore, to be consistant, the rate between your time and his time must run differently

[@tuhinchoudhury1795]

pls someone explain this....the two replies does not clearify this question //???kzbin.info

[@jackt4274]

Speed = distance / time, if for 2 persons traveling at different speed yet they still measure the same speed of light, based on the equation the time is also a variable that changes to keep the speed of light constant.

[@johnrubensaragi4125]

kzbin.info/www/bejne/m6ecq6WqlMSfm8U

[@En_theo]

@4:10 Should not Adam see the clock on the left fall down first ? He's coming from left and going "towards right" ; he should see the event on the left first, right ? :)

[@EugeneKhutoryansky]

+TheSamsanca, no. This has nothing to do with whether he is moving towards or away from the objects, but in what direction they are moving relative to him. I go over this in more detail in my main video on Relativity.

[@En_theo]

+Physics Videos by Eugene Khutoryansky I didn't mean that his movement was the problem, but that he's on the left compared to to both events (I described the movement to represent what I see in the video) . He still should see the left part before the right one.

[@EugeneKhutoryansky]

+TheSamsanca, No. Whether or not he is on the left or the right of the events is irrelevant, because this does not change the reference frame. This phenomena happens so that the light will be measured to have the same speed in all reference frames. Therefore, what matters in this situation is the relative velocities of the different reference frames, not what position in the reference frame Adam is located. Imagine that half way between the two towers, there is a light source, and that it emits a light beam to each of the two towers. The moment each towers receives the light beam they start falling. Sarah will see the two towers receive the light beams at the same time. Adam will see the tower he thinks is moving towards the light start falling before the tower he thinks is moving away from the light beam.

[@En_theo]

+Physics Videos by Eugene Khutoryansky Then why Sarah sees (@3:00) the left clock being ahead ? What's the difference with Adam ?

[@summeranne3652]

Why is the left spaceship so bloody? What is happening under Adam's jurisdiction?! He's acting suspicious for an intergalactic brigadier general and they need to report this to the lieutenant right away. Thanks for the great video I learned a lot but you really gotta watch what your animations do with their free time.

[@seanshubin2075]

Another great video. I like the pacing, it gives me a chance to imagine what is going to happen and then see if I am right.

[@EugeneKhutoryansky]

Sean Shubin Thanks. I am glad you liked the video, and the pacing.

[@raahimhadi4905]

very nice

[@bumblebeestudio2816]

Why the speed of light is not related? I mean why it(our view point) does not effect the speed of light?

[@TheyCallMeNewb]

Is it the case, that we witness the measurement of entangled particles - measured in the same direction presumably, with Khutoryansky cats watching on. ?

[@EugeneKhutoryansky]

TheyCallMeNewb, yes that animation was showing entangled particles having their spin measured in the same axis. I was showing how different observers will disagree on which particle was observed first, and therefore, they will disagree on which particle caused the other particle to change its spin.

[@RoseJetExhaust]

Mr. Therapist: "What are your dreams trying to tell you?" You: "I don´t know!" *the dreams:* 1:12

[@j9dz2sf]

Is it possible that, for two Inertial frames of reference A and B, the event E1 is before E2 for A and the event E2 is before E1 for B ? Problem of cause and effect ?

[@EugeneKhutoryansky]

For that to happen, you would have to move faster than the speed of light.

[@j9dz2sf]

@@EugeneKhutoryansky If, in some given reference frame, two events E1 and E2 are simultaneous, they can be not simultaneous in another refence frame. Which one can be before the other ? E1 before E2 or E2 before E1? How do we know?

[@EugeneKhutoryansky]

Whether E1 is before or after E2 depends on what reference frame (coordinate system) we wish to use. There is no universally correct answer to this question.

[@j9dz2sf]

@@EugeneKhutoryansky I would like to understand why, if in some reference frame, E1 is before E2, it is impossible that, in another reference frame, E2 is before E1. In still another, they can happen at the same time, but why not possibly E2 before E1? I know it is not possible, I know enough special relativity to know that (I am a scientist, rather in maths, but having been in university where I learnt SR, GR and QM), but I don't understand the dissymmetry between E1 and E2. An explanation with a space-time diagram and light cones could be interesting.

[@EugeneKhutoryansky]

This becomes obvious if we think about it with Minkowski diagrams. If you are not familiar with Minkowski diagrams, I have a video on this at kzbin.info/www/bejne/sITGn2aqi56Mhrc

[@Specialeffecks]

Wait a second, Eugene...let's say that Sara set up the 'colored' collapsing towers to collapse at slightly different times and in a certain order, say the "red" tower on the right collapsed first, leaving the debris of the left "green" tower, collapsing next, to cover the red tower's debris (leaving 'green' debris on top). If Adam moves in such a direction that he 'sees' that the green tower collapsed first (which would leave red debris on top), how do you reconcile the 'fact' that when Adam returns - the 'green' debris is on top? (Have we created 'two universes' one - which Sara meant to leave the red debris on top and one for the green?) What am I missing?

[@UltraTM]

Chris Retzinger What you are missing is that the animation is slightly inaccurate. You have to take into account is that the towers don't fall to the ground as one chunk, but for Adam even the right side of the right tower falls before its left side, the towers have to be seen as almost infinitely small pieces (or slices) that each fall at their own rate. So in your new experiment Adam sees again the right side of the right tower fall to the ground first, but the right side of its neighbor to the left (which fell first from Sarah's point of view) falls earlier than does the left side of the right tower, therefore the further left a tower is, the further "down" its debris is going to be laying.

[@xiaoxiao-kg5np]

Your not missing anything. The simple fact is that modern Physicists are too proud to admit that their hero Einstein was an idiot. And we have been talking a bunch of drivel ever since. How can they now admit that they were all too stupid to see it? And so the BS continues, but its not important, as none of this plays any part whatsoever in our real universe. Its all make believe.

[@MrBrendan20004]

So based on the nature of time, could it be said that the rate at which we perceive time to be flowing in the universe, AKA. the average rate that humans perceive time to be flowing, is dictated by the velocity of the Earth?

[@EugeneKhutoryansky]

InternetCannonFodder Every observer will always perceive their own time to be flowing "normally". The rate at which we perceive the time of another observer flowing depends on the relative velocity between us and that other observer. In reply to your question, the Earth does not have an absolute velocity, as there are no absolute velocities according to Einstein's Theory of Relativity. There only exists a relative velocity between two different objects, meaning how much one object is moving if we assume that the other object is standing still.

[@MrBrendan20004]

Eugene Khutoryansky Exactly right! So my lack of absolute velocity, if flying in a spaceship at near the speed of light, would cause me to see the universe whizzing by at a ridiculously fast rate.. With time around me moving faster than the time I'm experiencing. If we were to picture the Earth as a spaceship moving through space, would that not mean that if we wanted to, for whatever reason, get to a later point in our universe's existence.. We should somehow accelerate the Earth to near the speed of light?

[@TemmyTube]

Great video. It makes me wonder why people tend to see quantum mechanics as more counter intuitive than the theory of relativety. Why is enganglement so weird if there is no now? I guess the answer is that i ask the wrong question and dont really understand it :-)

[@EugeneKhutoryansky]

TemmyTube Perhaps this is simply because quantum entanglement has received far more media attention recently, and hence more people are aware of it, whereas not as many people are aware of the consequences for Einstein's Theory of Relativity.

[@bonetiger8]

from sarahs perspective all three space ships are have the same flow of time, why does the clock on the ship at the rear of adam seem to be ahead of time ? sorry I am new to physics and from a layman understanding :)

[@EugeneKhutoryansky]

+bonetiger8, it is so that both Adam and Sarah will see the same speed of light, under the assumption that they are standing still. I go over this in more detail in my main video on Einstein's Theory of Relativity. Thanks.

[@bonetiger8]

+Physics Videos by Eugene Khutoryansky Thank you for such a fast reply. Its great that your site is actually active :}

[@rodrigoappendino]

The left ship accelerate first, then the distance between them shrink. Bit what if the ships slow down?

[@EugeneKhutoryansky]

Then the left ship will slow down first, and the distance between them will increase, as is seen by an outside observer. This way, when the space ships come to a complete stop, the distance between them, as seen by an outside observer, will be the same as before the space ships started moving.

[@LendriMujina]

To me, this stuff raises the question of, how does time flow if there are *no* observers? Like after there's only black holes left in the universe, or after even they're gone? Or is the very concept of "after" so geocentric that it's meaningless?

[@Mysoi123]

if there are no observers, there still be reference frames. the order of events are reference frame dependent.

[@tscoffey1]

If Sarah sees one tower fall and cause the other tower to fall (by knocking it over), how could another viewer ever see them fall simultaneously? Would that not violate causality?

[@UltraTM]

tscoffey1 What you are missing is that the animation is slightly inaccurate. You have to take into account is that the towers don't fall to the ground as one chunk, but for Adam even the right side of the right tower falls before its left side, the towers have to be seen as almost infinitely small pieces (or slices) that each fall at their own rate. As soon as these slices get into contact with each other they are almost in the same location in space time and can interfere with each other.

[@ovdtogt1]

This describing is a non-synchronous time dilation due to a deceleration of the approaching velocity and is caused by a shift in the angle of view from Sarah's perspective. As the spaceships approach Sarah, the rate at which the spaceships approach her slows down causing a time-contraction. When they have passed Sarah, their distancing velocity increases, which continues the time- contraction. From Sarah's perspective the clocks do not run synchronous. The spaceships start of with maximum time-dilation when the separating distance is infinite. As they approach Sarah their time will dilate from Sarah's perspective and achieve maximum time dilation when spaceships are once again an infinite distance removed.

[@EugeneKhutoryansky]

That is not the way time dilation works. I know you have posted several comments about this, but this is a misconception. In this example, there is no acceleration involved. With constant relative velocity, it does not matter whether the two observers are moving towards or away from each other. What matters is the relative velocity between the two observers. The reasons for this were explained in my main video on Relativity at kzbin.info/www/bejne/m6ecq6WqlMSfm8U Keep in mind that all the observations discussed in all my videos are after we correct for the fact that it takes time for light to travel to the observer.

[@ovdtogt1]

@@EugeneKhutoryansky Okay. I get the 3 spaceships analogy whereby the middle spaceship sends light to front and back spaceship and for them to arrive simultaneously (from Sarah's perspective) the clock on the rear spaceship is running ahead in time compared to middle and front spaceship because light has less of a distance to travel.

[@EugeneKhutoryansky]

The clock on the left ship does not run "faster" than the clock on the right ship. The clock on the left ship is just always ahead of the clock on the right ship, always by the exact same constant amount.

[@ovdtogt1]

Noted.

[@joesands3350]

Define time: "duration of motion in space" or "relationship b/w 2 motions" or "numerical order of events" ALL occurring in 3D space Amrit Sorli's work which re-formalizes Einstein's relativity equations in terms of 3D space NOT 4D space-time. Time is defined as: "the duration of motion in space" - it only requires memory & motion. So the time we measure with the clocks is the numerical order of events. The fundamental unit of time is Planck time. Every elapsed time (duration) is the sum of Planck time: t = tp x n, where n is a finite natural number. Taken from the article: " In their paper, Sorli and Fiscaletti argue that, while the concepts of special relativity are sound, the introduction of 4D Minkowski spacetime has created a century-long misunderstanding of time as the fourth dimension of space that lacks any experimental support. They argue that well-known time dilation experiments, such as those demonstrating that clocks do in fact run slower in high-speed airplanes than at rest, support special relativity and time dilation but not necessarily Minkowski spacetime or length contraction. According to the conventional view, clocks run slower at high speeds due to the nature of Minkowski spacetime itself as a result of both time dilation and length contraction. But Sorli and Fiscaletti argue that the slow clocks can better be described by the relative velocity between the two reference frames, which the clocks measure, not which the clocks are a part of. In this view, space and time are two separate entities. “With clocks we measure the numerical order of motion in 3D space,” Sorli told Phys.org. “Time is 'separated' from space in a sense that time is not a fourth dimension of space. Instead, time as a numerical order of change exists in a 3D space. Our model on space and time is founded on measurement and corresponds better to physical reality.” p.s. one comment re: measurements (that many physicists use, incorrectly, as evidence for understanding) - just because we have measured a parameter e.g. the gravitational constant to the nth degree does NOT mean we understand its physical derivation.

[@rovrola]

Excellent video! I'm really enjoying your relativity series. Does the direction of travel have anything to do with the ordering of the time difference between the clocks relative to the Sarah's perspective? What would it look like if Adam made a loop near Sarah? Or if the polarization measurement was repeated while the ginger cat circled nearby? Another question: Is it possible to imagine a coherent perspective from which "now" includes events from the Big Bang simultaneous with events succeeding it? Thanks

[@TheAnantaSesa]

+rovrola There is a video ("Space and Time into a single Continuum") that says that if you go one direction then you are slicing time to include the future in that direction and the past in the direction behind you. you might find that interesting.

[@rovrola]

Thanks! Will check it out

[@lowersaxon]

It doesn’t matter if anyone far away agrees on „ now“. Here is where misunderstandings begin. We ask: dear Alien, what did you do on 01/23/2019? It doesn’t matter if we disagree on „ now“. Tricky relativistic bending of questions.

[@VarunPatel1709]

at 4:05, why does adam see the right tower break before the left. It should be the other way around. If sarah saw them happen at the same time from a far reference point, for adam the information from the left tower should have reached him first and then the right tower.

[@EugeneKhutoryansky]

The way it is shown in the video is correct. This is not an effect of how long it takes the light from an event to reach us, but due to how time transforms from one reference frame to another in Relativity. I cover this in more detail in my main video on Relativity at kzbin.info/www/bejne/m6ecq6WqlMSfm8U

[@augijyotbali2131]

But why the clocks at left go ahead in time ?