Relativity of Simultaneity | Special Relativity Ch. 4
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- เผยแพร่เมื่อ 25 เม.ย. 2018
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Mark Rober's youtube channel: / markrober
The previous videos in this series:
Chapter 1: Why Relativity is Hard • Why is Relativity Hard...
Chapter 2: Spacetime Diagrams • Spacetime Diagrams | S...
Chapter 3: Lorentz Transformations • Lorentz Transformation...
This video is chapter 4 in my series on special relativity, and it covers how things that appear simultaneous from one perspective in our universe aren't simultaneous from other moving perspectives - that is, from inertial reference frames moving at different speeds. This is explained via the Lorentz transformation of coordinates of the events in question, enacted with a mechanical minkowski diagram, aka mechanical Lorentz transformation, aka spacetime globe.
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Created by Henry Reich - วิทยาศาสตร์และเทคโนโลยี
This is a relatively good video
I think your comment happened before this video was posted. I SAW IT FIRST!!
Get out.
Actually, it's equally good in all inertial frames
Bayardo Pinzon No, it happened simultaneously. You're just moving too fast.
Mercy!
This series has already given me more intuition for relativity (especially simultaneity problems) than I got from two physics degrees.
acapellascience oh hi
Yo!
That's an interesting way to say you have 2 degrees in Physics lol
Same
It's really quite amazing how this channel (and it's sister channel, Minute Earth) manages to repeatedly outdo our educational system in that regard.
“Simultaneously spontaneously combust” is fun to say.
Mister Apple It is, isn't it?
That is a pretty good one. I also enjoyed the title. Relativity of Simultaneity. Just saying it out loud is worth it once or twice, lol.
At 3:10 I was expecting "simultaneously spontaneously" for some reason, probably because I'm used to hearing these two together
Or is it?
Correct.
Why do people simultaneously claim to be first? Maybe because in their worldlines they are first while they are in fact simultaneous to some other observer? Who knows....
Good one :D
can you uphold a beat simultaneously to a relatively polyrhythmic beat?
watch?v=eQ3x2NSasg4 if you're bored with 3 against 4 and haven't got time for 4 against 7
I’d venture it’s because these individuals’ lives are so mundane and dull that something as insignificant as being the first to reply on one of the billions of videos on TH-cam enables them an artificial feeling of accomplishment and self-worth that they feel should be acknowledged by complete strangers on the internet. But that’s just my hypothesis...
Thomas Chow Maybe due to data compression, the space/time on TH-cam servers is not linear!
A more pertinent comment, I suspect, than you imagined, since both the relativistic effects described in the video and what you describe are as a result of the fact that the dissipation of information (including information as to whether somebody else has yet posted a comment) takes time.
"The takeaway here is that our universe has neither an absolute notion of time..."
I tried explaining that to my boss last time I was "late" for work.
Needless to say, it fell on deaf ears.
Relatively speaking
@@vishnuvarma8019 Exactly, but that argument didn't work either.
jk
But there is 2 axis so that means no absolute notion of distance either. Both time and distance shrink or expand to accommodate relativity
My mind is officially fucked up now
For me, the "oh, I get it now" moment was at 2:18, when he connected relative event-time to relative position. Well done.
I love this relativity series. It’s awesome that you’re making relativity accessible to people who would otherwise know nothing about it
Seeing stuff like this always makes me feel we are just living in an amazingly advanced graphic engine! : )
To an extent, we are :)
If you are talking about the quantum level…technically…you’re not wrong
"Moving perspective" is a thing that changes location relative to another thing. I understand why some people don't get it, because they didn't watch and understand the previous video's.
Great video on this topic, easy to follow and visually apealing.
Space Time Grids should one day be as common as globes
Agreed.
I was thinking that throughout the entire video, it makes everything so much clearer having that physical guideline!
Someone (not me) should connect with the other TH-camr guy who built it, make it more mass-producable, and it'll have a niche in all those science-gizmo stores and probably hasn't classrooms.
Come to think of it, maybe I'll try to do it after all.
@@bend.manevitz8261 Are you serious about doing it?
@@ASLUHLUHCE I'd love to, but I don't even know where to begin
@@bend.manevitz8261 I found this today and FYI I would buy one for $100. MAKE THEM!
I like how the square thing moves stuff
Fantastic job on these videos, I'm thoroughly enjoying them! As a student who took AP Physics 1 and is prepping for the AP Physics 2 test, this is an incredibly helpful review for one of the most confusing and unintuitive topics covered. My mind was blown when you made the comparison between the relativity of time to the relativity of velocity! Keep up the good work!
This is a great series! You make great content.
Take that, people who comment 'first' !
You win today's Internet!
Agreed, Jeremy McMahan
‘first’ !
Blue shirt kid ?
i'm learning so much from this series, I'm always checking your channel for new episodes. thank you for making this so simple to understand
You quoted Mark Rober but it felt more like rewatching PBS Spacetime's episodes about spacetime all over again, even down to the diamond shaped grid you used to represent spacetime. Also "relativity of simultaneity" best phrase ever!
I understood everything but from 0:00 I LOST IT
Einstein was great
But your videos are awesome
th-cam.com/video/mAOZ3XjHqsI/w-d-xo.html
How can you say
If he's so smart, how come he's dead?
The Table you've made is incredible!
Great work
man that's a really neat Lorentz transform mechanism
Yay.. finally. I was waiting for this video from long time. Seemed to me like an year. Maybe I am too fast.
HettGutt, Henry is slow or maybe he is heavy.
I'd love to see how Mark made that space-time globe!
This is an amazing serie, thanks for all off this important and educate work!
this idea hit me while studying pdes in the context of fluid mechanics. glad to see other people thinking about it ☺️🙌🏽
If I play this video at half speed do I understand twice as much or cut my learning over time in half?
Yes.
Yes
so, did Han shoot first?
That depends on whether you view that event from the theatrical perspective or the special edition perspective.
Cause and effect still apply, so Han either responding to Greedo firing, or preemptively attacking, would still have to be a "One or the other" sort of thing I'm afraid. Relativity isn't going to bring the fandom together. =p
That's assuming we know the causal structure of what happened. If we are trying to determine the sequence from observation alone, then we still don't know who shot first. :)
Anant Dixit True, but Han’s perspective gives us a far more relevant answer. :p
It's pretty nice that this chapter is short and exists on its on. Because it gives us viewers time to let those concepts to sink in
Space Time Globe.. Nice!
The first time for me to see such a "complex/mindboggling/hard to grasp" matter illustrated in such an easy/intuitive way.
Brilliant is what it is.
Thanks for that!
Do the boxes not burn at the same time but it just takes light longer to reach the other person to 'notify' him of this since the boxes are not the same distance away from him?
How out of sync will events be when observed from 10 billion light-years away or on opposite sides of the observable universe? Since objects at this distance have incredibly high redshifts (i.e., they're moving away from us incredibly fast), how does this affect the apparent distortion? How successfully have astronomers and astrophysicists incorporated these effects into their observations, calculations, theories, etc.?
Expansion of the universe is governed by general relativity equations, not Lorentz transformations, so the effects are different there. There is indeed some time dilation (and it was observed for distant galaxies), but I'm not sure how simultaneity is affected. Good question!
i love space time grids so much! i have studied simultaneoity and time dilation ect., had understand somewhat.. BUT this representation was great, so clear! thank you so much for this.
As a first year physics student, this visual representation is very, very helpful. I liked this video before I was studying it, now I REALLY like this. Thanks! :)
Lovely video, Henry. But I CAN'T believe you didn't give us the full story. Relativity of simultaneity only works for causally unconnected events. If event A causes event B, then all frames of reference will agree that event A happened before event B. In terms of spacetime diagrams, relativity of simultaneity applies only to those events that lie outside an observer's lightcone. This basically means that these are (causally) irrelevant events and it doesn't matter (to you) which event happened before which, because neither event can affect you.
I'm pretty sure in previous videos he mentioned that no mass can move at or faster than the speed of light, and as you stated, causality is preserved in all inertial reference frames so long as velocity does not equal or exceed c.
Also he avoided acceleration which is good
Some things are not too hard to understand until somebody tries to explain them.
Consider c the speed of causality, represented by the 45° lines (or rods of the globe), which never change regardless of transformation. You can now look at the different boxes, and see what events could have been causally linked in your original perspective, and which ones could not have been; and you can see how these relation of possible and impossible are preserved after the transformation.
I have a question: when we say two simultaneous events are no longer simultaneous from a moving perspective, do we then mean that
A: they actually happen at different times
or
B: They still happen at the same time, but the light from the events hits us at different times?
Both of your answers are correct - given relativity, the time that it takes for light to reach us defines how we view simultaneity. So, if two things happen the objectively same time then they given some viewpoint can happen at different times. Hope this helps, not sure if what I said makes much sense.
@@colejohnson260 Hahaha mad person too
Yeah, I was confused about this too. Because if you would be traveling towards the moon from Earth at c/2 as soon as the explosions would happen simultaneously from a viewpoint on earth wouldn't they also be simultaneous from the moving perspective because of the light having to catch up to you?
I litteraly can't stop thinking about relativity anymore which is the reason I went back to this video. It's driving me nuts...
Outstanding and most enjoyable way to take in such a generally difficult subject. What teaching skills! I can only imagine the time and energy expended to have developed and created this 3.47 Minute video, but as one in the audience i greatly applaud you for having done it. Thanks very much. Whatever it is you do for a living i sincerely hope it has something to do with teaching :)
I really love these videos - and I love the amazing Lorentz-transforming device.
So, if from perspective α, two events can be simultaneous and yet not simultaneous from perspective β, then it also follows that a scenario can be arranged whereby, from perspective α, event A occurs first followed by event B, whereas from perspective β, event B occurs first, followed by event A.
Does this introduce problems with causality? Could the scenario be such that someone with perspective α reasonably conclude that events A and B are related, and that, since they are related and since A occurred first, then A _caused_ event B? If so, then such a claim would be nonsense to perspective β, since it is a premise of basic causality that effects cannot precede their causes.
This seems vaguely reminiscent of the sorts of paradoxes that arise when one hypothesizes reverse time-travel, wherein one could take an action to cause or prevent something that had already happened.
No. If there are two events, A and B, separated such that A is before B and something could move from event A to event B at some speed slower than light (or put another way, there is a valid frame of reference where A and B happen at the same location), then A will precede B in all reference frames. The time between them may change but it will always be greater than 0. Conversely, if the relative ordering if events A and B is frame dependent, then there is no valid reference frame where A and B happen at the same location. It is the difference between spacelike separation (first situation) and timelike separation (second situation). The border between them is lightlike separation, events that can be neither in the same location nor occur simultaneously (and for which the order in time is not relative).
Arkalius80
Thank you for the excellent answer!
*Pretends to understand whats going on*
Have you watched the previous videos?
me 'n' pure thank you for clearing that up for us
I think its hard to grasp not because of the math involved or the concept. Its trying to picture the same event appearing to happen in two different times.
Azmen thx for making it clear.
I have a PhD in understandology.
Your videos are amazingly intuitive! Thank you so much
Thanks so much. After scraping my mind off the walls watching fermi lab's description of time both space compressing and synchronous stuff being out of sync, I just HAD to see it on the Spacetime Globe (TM) to get my head around it.
Great stuff.
Fun fact, Lorentz transformation is a matrix of rotation with hyperbolic sinus and cosinus.
What is sinus
Oreole1
I don't know in some other modern language than English, but in English, any mathematical use of sinus and cosinus are incorrect snobbish affectations, apparently derived from some Latin mistranslation of a medieval Arabic math term.
Oreole1 a sinus is a bone cavity which gets filled with snot when you have a cold. Glad I could help :)
When will paradigm (i think that was the channel's name) be available to other countries?
never.
Wait, what are you talking about?
Fons the Magnificient minutephysics new show is region locked to th US
WTF? That's ridiculous.
You made this concept very easy to understand, and, the best part is, it seems so simple.
I NEVER KNEW THIS AND I'VE BEEN WATCHING PBS SPACETIME TO LEARN LARGER CONCEPTS BUT IM MISSING FUNDAMENTALS LIKE THIS BECAUSE THERE IS JUST SO MUCH TERRITORY TO COVER. AHHH THANK YOU ❤️❤️❤️❤️
> “world line”
>steins;gate confirmed
Well, steins;gate took inspiration from physics
Physics are a Jojo reference
I think that literally every time he says World line XD
guaymaster Za Warudo line.
Mmmmmm i think i saw weeaboo here
This is some crazy shit
I really appreciated your special relativity series. Thank you so much for the time you put into it. Let's not get into who's viewing the time though. ☺
Thank you very much! You can explain very well complicated things in no time!! I love your videos !
I've never been so early... or so confused...
DysnomiaFilms ya same here
What specifically didnt you get? Its a bit of a mindfuck, but if you take the assumptions it should be easier
Minutephysics, a question, shouldn't the universe in its early state have merged into several black holes considering that it was so dense?
Yusef Daniel Hassoun Harmouch It was like a black hole in the sense it was a singularity. But, weirdly it was not a black hole. Do you have a background in General Relativity?
Yusef Daniel Hassoun Harmouch
The universe didn't end up like that, this means that the expanding force was to big for it to happen. But several blackholes did form in the early stages of the universele though, hence the supermassive black holes in the center of galaxies. However no one really knows exactly what happend, it all is just a theorie after all. We may discover something new that changes our theorie.
Ouma Shu not really, but i understand more or less some of the stuff, is it necessary to understand the answer?
Yusef Daniel Hassoun Harmouch it's always cool to know.
Mr. J_Krr_ that's my motto! (not really, but from now on i will say it is)
This video and the space time globe are awesome! Helped me better understand special relativity, and it's just fun to watch and listen to these videos. Thoroughly enjoyed this 😁!
I am loving this Special Relativity Series! Awesome! This should be a Grade 6 Physics 101. Much needed for the modern science kid.
Isn't Lorentz transformation similar to Eigen vectors and Eigen value?
no
A transformation is not "similar to" some vectors and values, that's comparing apples to oranges. The word you're looking for is "related". The Lorentz transformation is a linear transformation that has eigenvalues and eigenvectors, and its eigenvectors correspond to light rays, which is expected since speed of light should be constant under this transformation.
this hurts my brain
Man, I love this series
Might be my favorite video from this channel.
If relativity ruins simultaneity, does it also ruin causality? If two events take place right after each other in time from one worldline, could the order of the events be reversed after transformation to another worldline? What if the object, said events happened to, was moving?
This is where the speed of light comes in. MinutePhysics hasn't covered it much/at all, but on the "globe" the x=t line is the speed of light. Causality is preserved for all events that are within this "light cone" in the region between x=t line and the t axis. You can only observe a change of order for things that would require FTL signals (which we assume are impossible, preserving our idea of causality)
causality is a basic principle of physics that must not be affected by the reference frame
so even though the order of 2 completely unrelated events might be reversed depending on your own movement relative to the events
a event that happens because of the event before will always be seen as after
iirc it is because for there to be an "influence" of the first event to the second information has to travel from the first place to the second (with max the speed of light) meaning that the time between the events themselves is at least the time it takes light to reach the second place after the first happened
That would happen only if you went faster than light. This is one of the problems with FTL travel - a spaceship with warp drive would seem to arrive at a destination before It left (from some frames of reference)
This is a fantastic question. It relates to the geometry of flat space-time and the invariance of a distance metric, called the spacetime interval, under Lorentz transformations. The sign of the spacetime interval indicates whether two events could be causally related to each other. If two events can be causally connected (light has enough time to travel between the two), then the order of these two events is the same in all reference frames. If two events cannot be causally connected (light does not have enough time to travel between the two), then there exist reference frames where one event occurs before the other and vise versa.
Good question! The replies don't really answer the question (IMHO): If A observes two events as simultaneous, A can conclude that Event 1 did not cause Event 2 because "c". But if B observes Event 1 occurring before Event 2, then to B it would be possible for Event 1 to cause Event 2. Also, is there a frame of reference where everything is simultaneous? Would that occur if the observer is travelling at "c"?
is there a game where these effects are exaggerated?
www.testtubegames.com/velocityraptor.html
gamelab.mit.edu/games/a-slower-speed-of-light/
Just finished velocity rapter, good gosh that mind fuck
Very good to spit such hard concepts in this pace. It makes suddenly science super clear and so easy to understand. The funny thing with those videos is that they give the sense the explanation was friendly but you understood zero.
Very nice visualisation!!
Time to make .myself feel smart by noding my head while he says big words
My tiny brain doesn’t get it
Thats because its pseudoscience that has been falsified
Amazing explanation! Now I have some intuition of special relativity; can't wait to see general relativity
One of the very few videos on TH-cam I have to watch at reduced speed!
For people who don't quite understand, I find it helpful to think of time propagating at the speed of light. This is in essence true, since the fastest information about an event can travel to you is the speed of light. For example, if we look at a distant galaxy, we are effectively looking back in time.
CozmicK G Yeah, you might have it easier in that way, but you might get a bit stuck later. Consider this. The Lorentz transformations are very very symmetrical in space and time. If time moves at the speed of light, then so does space, but that messes things up. Doesn't it?
Being a physicist, let me tell you something. Forget that there is something called a flow of time. Just think of time as a coordinate. That will actually help.
You can even explain simultaneity like this! If you are stationary, you are more in time, and less in space (your world line does not move on the space-axis). Now, someone is moving wrt to you. He is less in time and more in space. This mismatch of relative time and space causes things to be not simultaneous for him if it's simultaneous for you.
Cool isn't it?
German Pepe Exactly. See, it explains more than just meets the eye. It even explains why light bends twice as much around the sun as it should be.
97% of people don’t understand
Biniam_ Boss i lost him at 0:00
does that mean i am in that 3 percent.
i know i am genius
"it's science so it's difficult to understand"; come on guys :D
Say you don't understand. Don't push it on other 96.99999% people.
Please be joking
This brilliant machine makes relativity much easier to understand. Thanks to your both.
This certainly helps with understanding of general movement. Although we can't witness events happening ever at a time that can be considered 'true' surely we must be able to say that two directly-controlled events happened at the same time, even if that can't be factually agreed upon by observers. Unless I'm mistaken this is specifically speaking of observation of motion, not actuality of motion. Which I'll admit is also susceptible to frame of reference, but kind of like how c is so large as to not matter, generalized location should be exact enough to be able to work out for actual movement, rather than observed. I think the difference is important.
e: Reading about superclusters this quote seems to make sense to my point "The biggest cluster in the observable universe is called the Great Attractor. Its gravity is so strong that the Local Supercluster, including the Milky Way, is moving in a direction towards it at a rate of several hundred kilometers per second. Speeds at this cosmic scale are measured relative to the Hubble flow frame of reference." It seems specific frames of reference are considered more exact, kind of like different methods of dating artifacts are more specific or exact.
Can this comment Stay up
I swear its my assigntment
HELP ME!!
Hey are you the lost poo!
First
To like my own comment 🤣
But... I.... You didn't...
The reply to your comment has more likes that the original comment about liking your own comment... or something.
Jake Miller No longer true
Depends on your frame of reference
First
To hate you!
Just kidding, I am fifth.
I love that box! Very creative and intuitive. I want that globe
it helps if you visualize the events that are moved horizontally on the time axis as all being present on the time axis. so the box isn't a bit to the left and further up, it's just further up. same with the person, you can see how relatively, less time passes in one second for blue than for red, because blue's instances are closer together.
we can do this because time is one dimension in our universe, not two, so events can only be on the w-axis.
1.10 its not the box on right that combusted first, its my mind , my mind got blown watching this. I do not have any words to describe it. Just amazing...
Guys, I thought you were good before but this video brings it to a new level. Thank you for sharing knowledge in such a simple, efficient and funny way.
Im amazed at that box dude. Way to simplify something hard to grasp.
2:15 That helped me so much in understanding this.
Man, this is awesome!!!
Feed me more! These are great!
I would have never understood special relativity if I hadn't had this video, cause I don't have the time or the resources to study physics in college. So thank you MinutePhysics. Thank you VERY VERY much!
I LOVE this channel.
Loved it as usual 😀
Your space-type globe really needs to became a teaching accessory.
Nice work
Love your channel
I liked the series very much as a student who knows very less about special relativity but please use the position on y axis and time on x axis as it gets very confusing otherwise and I think many people like me would have faced the same problem.Please try to implement that in future videos. Amazing series though 😀
I LOOVE THIS SERIES
Excelente explicación del relativismo, simple y al punto.
simultaneously spontaneously. When you said that I almost had a seizure. Nice.
I like the way u did your Xs in this. Its minor. But it's a nice change to make reading it a bit easier.
how did you make this so easy to understand, youre a genius. well we all knew that already
Mark Roger is dreamy!
MInd blown...I got goosebumps watching this video because I was able to understand.
Nice work as usual! But... I suspect a lot of people are going to misunderstand an important part of what's going on here, and conflate the concept of light propagation delays for what the Lorentz transform really means. It's very easy to write it off as "what appears simultaneous for me appears not for you because you're at a different _distance_ ". If two supernova go boom, and I'm in the middle, it _seems_ simultaneous for me, but obviously if you're closer to one of the big badda-booms, that one _seems_ to come first. I think you need to make it a little more clear that spatial distance is irrelevant... if the 2nd observer is whooshing past you at significant speed and barely grazes your elbow (so you're both basically at the same position, but with a different velocity) they will STILL see the ka-booms happen at different times. Isn't that the key point that causes sane people to question their entire concept of reality, and you hear the delicious sound of brains breaking? Not "I was over here and I saw something different" but "How can we be disagreeing when I WAS THERE TOO?" ...did I get that right?
You were right, most people here are confused about that point.
I understood that time appears different when you go fast but I never understood why till this video thanks can’t wait for the next one
I really which you explained that moving box thing better. I had to watch multiple times before I realised I was supposed to be paying attention to the centre line to see the frame of reference.
The spacetime globe is amazing in its ability to physically show you these things; it comes off so simple and easy to understand. He should patent the design because these belong in every classroom.
Here's a kind of digital one you can play with ibises.org.uk/Minkowski.html
Great Video. Thanks!
love the series
yay more of this!
It is incredible to me that some people still disbelieve SR (and by extension GR). It seems like a deliberate effort to ignore intuition, like they want a more complicated explanation
because of this explanation, i now feel like im on top of the world!, thanks to you and mark!