Relativity of Simultaneity | Special Relativity Ch. 4 

This series has already given me more intuition for relativity (especially simultaneity problems) than I got from two physics degrees.

This is a relatively good video

“Simultaneously spontaneously combust” is fun to say.

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....

I love this relativity series. It’s awesome that you’re making relativity accessible to people who would otherwise know nothing about it

"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.

For me, the "oh, I get it now" moment was at 2:18, when he connected relative event-time to relative position. Well done.

Seeing stuff like this always makes me feel we are just living in an amazingly advanced graphic engine! : )

"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.

I like how the square thing moves stuff

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

The Table you've made is incredible! Great work

Space Time Grids should one day be as common as globes

This is a great series! You make great content.

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 an amazing serie, thanks for all off this important and educate work!

so, did Han shoot first?

Yay.. finally. I was waiting for this video from long time. Seemed to me like an year. Maybe I am too fast.

this idea hit me while studying pdes in the context of fluid mechanics. glad to see other people thinking about it ☺️🙌🏽

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.

I'd love to see how Mark made that space-time globe!

Einstein was great But your videos are awesome

Your videos are amazingly intuitive! Thank you so much

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

I understood everything but from 0:00 I LOST IT

If I play this video at half speed do I understand twice as much or cut my learning over time in half?

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 !

Take that, people who comment 'first' !

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?

I really love these videos - and I love the amazing Lorentz-transforming device.

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 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?

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.

You made this concept very easy to understand, and, the best part is, it seems so simple.

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.?

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.

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!

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 :)

When will paradigm (i think that was the channel's name) be available to other countries?

Fun fact, Lorentz transformation is a matrix of rotation with hyperbolic sinus and cosinus.

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!

Man, I love this series

*Pretends to understand whats going on*

> “world line” >steins;gate confirmed

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 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 ❤️❤️❤️❤️

I've never been so early... or so confused...

This is some crazy shit

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.

Amazing explanation! Now I have some intuition of special relativity; can't wait to see general relativity

Minutephysics, a question, shouldn't the universe in its early state have merged into several black holes considering that it was so dense?

Isn't Lorentz transformation similar to Eigen vectors and Eigen value?

This brilliant machine makes relativity much easier to understand. Thanks to your both.

One of the very few videos on RU-vid I have to watch at reduced speed!

this hurts my brain

is there a game where these effects are exaggerated?

Im amazed at that box dude. Way to simplify something hard to grasp.

I am loving this Special Relativity Series! Awesome! This should be a Grade 6 Physics 101. Much needed for the modern science kid.

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?

Time to make .myself feel smart by noding my head while he says big words

Might be my favorite video from this channel.

2:15 That helped me so much in understanding this.

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.

97% of people don’t understand

I love that box! Very creative and intuitive. I want that globe

man that's a really neat Lorentz transform mechanism

Can this comment Stay up I swear its my assigntment HELP ME!!

First To like my own comment 🤣

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.

simultaneously spontaneously. When you said that I almost had a seizure. Nice.

Excelente explicación del relativismo, simple y al punto.

Just watched this before heading off to my physics final. Thanks for the last minute help, Henry!

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.

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.

because of this explanation, i now feel like im on top of the world!, thanks to you and mark!

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.

how did you make this so easy to understand, youre a genius. well we all knew that already

I LOOVE THIS SERIES

Very nice visualisation!!

Nice work Love your channel

Feed me more! These are great!

Your space-type globe really needs to became a teaching accessory.

yay more of this!

love the series

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...

Man, this is awesome!!!

Loved it as usual 😀

That globe is so cool! I hope to have one sometime...🙃

I know this channel for three years. But I didn't see this till now!! How of this are still there??

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.

Thank you so much! I finally get it :)

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!

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?

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 😀

Thanks! Good series! ; )

How many parts are you planning on doing? I want to watch all of them at once after you're done but I don't know when to start watching lol

MInd blown...I got goosebumps watching this video because I was able to understand.