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....
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...
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.
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 it was the combusting box. I always struggled with this. I still don't understand one thing though- are the boxes combusting at the same time no matter what, but the light from that event just takes longer to reach me if I'm further away/moving away from it, so the photons take longer to actually get to me? Or are the boxes actually combusting at different times from the POV of an external observer? Ie- if two boxes combust at the same time, and nothing is moving, but one box is closer than the other, I'll see the closer box explode first from my perspective. However, someone at a different position that is equally far away from each box would see them combust simultaneously.
"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.
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.
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!
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!
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. :)
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! :)
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!
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.
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...
1:30 "...Simultaneous events don't appear to happen simultaneously...": But this isn't because the speed of light is constant for all observers. It's because of the same effect that causes parallax. The speed of light is constant because that's the natural speed of a electric field leap-frogging a magnetic field and propagating in some direction (or all directions simultaneously as in the case of an omni-directional antenna). Depending on my speed and direction in observing it can make it appear to be different... i.e. it's the same regardless of who observes it... but it won't "appear" to be the same. If I move two antennas toward each other at 1/2 the speed of light, the signal will reach the other antenna as if it were traveling at twice the speed of light. Conversely, if they are moving away from each other at 1/2 the speed of light, the signal will never reach the other antenna. Now within that leapfrogging is an oscillation that our eyes sense and distinguish as color.. and radios distinguish as field oscillations (magnetic and/or electric). A prism can slow down the propagation and make the colors appear more blue. Or, as astronomers claim, an expanding universe causes the colors to appear more red (the red shift). Or oscillating the magnetic field in the case of an electric motor can change the speed of the motor. But it makes no difference at what speed the motor's platform is moving as long as the generator is moving with it. If the speed of light was not dependent on the speed of the platform from which it emanates or the platform from which it is observed, where can this color shift come from? It can't come from a change in vibration. It must come from a change in propagation... i.e. a change in the speed of light. 2:45 "...happen at different times...": Wrong. They happen when they happen... which may be the same time. They are observed when they are observed... which may not be at the same place, the same distance, or the same time. Depending on where they happen or where they are observed they my appear to happen out of sync... or if you're moving away at the speed of light relative the speed of the platform from which they emanate, they aren't observed to happen at all. Well, I watched all four videos. I see nothing that disputes my comments. Try this experiment. Have one mass moving in the +x direction at v. Have another moving in the -x direction at v. Their momentum is 1/2 mv2 each. They collide perfectly and stop simultaneously. The total momentum goes from mv2 to zero. They get hot. If v = c does m = E? Does m disappear...or spread out a whole lot?
So at 2:45 if say the orange guy crossing t3 represent him pressing the button to "instantly" ignite the boxes, from blue guy perspective the 'righ't box wile ignite before orange guy press the button ?
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 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 ❤️❤️❤️❤️
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?
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).
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.
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.
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.
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!
2:30 Is this due to a Lorentz or a Galilean transformation here? Or is there a combination of both here? Actually I think I answered my own question by going back to 1:56. you can see that the expression for x_new is just a Galilean transformation but scaled by the Lorentz factor which, unless you're going ludicrous speed, is ~1 and there's isn't really anything out of the ordinary happening. When you start going relativistic speeds, the Lorentz boost would make it seem you're moving away slower then from the normal Galilean transformation (I think you can see this at 1:14, the orange man is moving at less than 1/3c away from the blue man). Is this a result of "distances get shorter and times get longer, so speeds get slower"?
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...
Here's something that the light globe suggested might happen but was not clearly addressed in the video. In my world view with stationary objects at a large distance from me, in the perspective of a person moving away from me extremely fast, are those objects still stationary with respect to me, or is there essentially dilation of the distance between me and the objects, indicating that from that other perspective those objects are NOT stationary with respect to me? If so, that might be the key that might help me intuitively understand how simultaneous events from stationary objects at large distances from me might not appear as simultaneous from a rapidly moving perspective.
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.
Get's a bit confusing to me at 1:04. Are we talking about what the blue guy observers or what me I, the viewer, who is at the same distance away from the boxes observes? Even if the blue guy is not moving relative to the red guy, he observers the right box to combust first - because it is closer. What I'm getting at here is, pretend you are blind and you can only hear which of the boxes "explodes" first. You hear first the closer one, then the one further away because it takes a while for the soundwave to reach you - and so does the light. At 1:31 he says the according to the orange guy all 3 boxes combust simultaneously, which is true only for me, the orange guy would perceive the furthest box to combust the latest. So the box is twice perceived as being out of sync, once because it is further away, and second because of special relativity? At 2:03, If I put speed of the observer zero, I get the result that tnew=told, removing special relativity alltogether, which is not what I would actually observe.... So we are not talking about what is observed at the same time, but what would be observed at the same time if I could magically insantly sense both phenomena regardless of the disantce?
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 :)
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
*raises hand* I have a question, it looks like the x-axis is being measured in the distance light travels in 1 second. Being one unit. But when two objects(or perspectives) are at the same Ttime but different Xdistance (lets say 1 unit away) and 1 object turns a flash light on. On the grid it looks like they would be perceiving that light at the same time, although it should take 1 second for the light to reach the other object. (The 45° angle) Again this is assuming the objects are 1 unit apart, but not moving over time In the example you show at 1:31. You state that the orange person would perceive the 3 burning boxes simultaneously. I am not sure how that can be the case. Am I missing something?? Also love your videos
So if the situation is like here 1:30 then combustion of bouth boxes to the left of the orange guy is happening simultaneously for him. But will he see a delay between combustions of these boxes one of which placed farther apart from the guy?
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.
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!
Will the boxes actually combust at different times when considering a moving frame of reference OR will they combust at the same time, but it is just that the light of combustion is going to take longer to reach you...creating the illusion that they are combusting at different times? It is akin to saying that Betelgeuce has gone supernova, but since it is 800 ly away from us, we just haven't seen it yet.
2:00 What if you're moving towards the moon from the earth at c/2 as soon as the explosion on Earth happened. Wouldn't this mean that the explosions would be in sync for you too because of the light catching up to you?
even if you are travelling at (1/2)c, light is still travelling at c, this constant speed. see, light doesn't catch up to you, as the light is travelling at a constant velocity to both observers. therefore the transformation still holds up - remember, in this video each tick mark in the x direction is ~ 300,000,000 m, and forms that 45° angle with the origin, whilst you, travelling at (1/2)c form a 67.5° angle with the origin. as long as the angle you make is not equal to or less that 45° in the x direction light doesn't "catch up" to you, and the lorentz transformation and its implications are not violated.
Consider the scenario when the red man sees two combustion at the same time in his frame of reference and the blue man sees two combustion at different points of time in his reference frame. Suppose, if the blue man says "right" when the first box combusts for him in his frame of reference, and then later says "left" when the second box combusts according to him. Then what according to the red man, are the words said by blue man when both the boxes combust simultaneously for him (the red man) in his frame of reference?
1:59 So if a friend of mine is in middle path between the mars and Jupiter and she turn on magic flashlights on each planet at the same time From my perspective, when I receive both lights and discount the time of the light travel, mathematicaly, the flashlight on Jupiter has been turned on BEFORE the light on Mars?
Do they actually happen at different times for the moving perspective or does the moving perspective only perceive it as such because light has to travel to show the event?
the latter, that's the only way to maintain continuity. For example you could stop box B from combusting if you knew box A combusted and you knew they would do so at the same time. That's not the reality because the speed of light is constant. long story short box A and B combust at the same time but the light from box A hits you first
1:26 this has nothing to do with how far the information has to travel right ? It literally happens later in his perspective not because it takes more time for it's information has to come but because of him moving shifts the space-time diagram. If so in real life, we (as the blue guy) would see the furthest box to burst in to flames much more later then what we have calculated because it happened later and the information also traveled a really long distance. Right ?
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.
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.
Wait a second... If I have two for C events A & B happen for an observer C left of him at the same time, e.g. A at -1 and B at -2 (something), wouldn't those two events have to happen simultaniously for an observer D drifting apart from C? As the information moves with speed of light, sure, but if both signals from A & B reach C at the same time, don't they have to reach also D at the same time, as they always move with speed of light independent of the perspective themself? For a Spacetime diagram, 45° is usually the speed of light, right? So for the two events A & B to happen at the same time for observer C, don't you need to put A at e.g. (5.-1) and B at (4,-2) so that the information of the event A has time to catch up to B in order to reach C simultaniously at (6,0)? And then also the events keep happening at the same time for an observer D, as the angle of 45° does not change. I mean, at 0:58 the two events do happen at the same time for the observer in the middle, but not because they are on the same horizontal line, but because they also have the same distance to the observer, thus the meeting point of their diagonal lines is also at the position of the observer. Would the right event be further away from the observer, it would have to happen earlier so that the information can reach the observer at the same time as the event at the other box (or on the time globe that the diagonals meet at the same point, which are gladly also the iron bars of the globe).
@silverrahul But my question was how it is if the signals of A and B reach C at the same time... Also no, just because A is closer to C than B doesn't mean its signal reaches C first. If A happens after the signal of B surpassed A, clearly the signal of A will reach C after B. Because the signal of A clearly would need to travel faster then light in order to reach C before B. In all perspectives.
@silverrahul They shall happen at the same time only for C. If A happens right when the signal of B passes A both signals should reach C at the same time. Therefore, B ofc has to happen before A. Thats my whole point about the video at aprox 2:40. He says that all three events happen simultaneously. And that might be true for himself as an observer perpendicular to the room axis, but for C afaik the further right event happens after the events closer to it, as its signal reaches C later.
@silverrahul Yes, but from the perspective of C both events happened at the same time, so whats the difference to saying they happened simultaniously in the C frame? I mean in that system it is not like C has any way to get other information then the signals reaching it.
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.
WAIT A MINUTE -- how do you track how things look relative to a moving object thats going in curvy directions. Do you do a squiggly Lorenz transformation, making the T axis a squiggly line?
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. ☺
0:57 Think this way The match that lights is actually lighting at the same time but the light (information) of it happening can be delayed if the distances are larger and if the object is accelerating nearly the speed of light, so for person(a) near the match can see it almost instantly but for person(b) moving at 60% the speed of light, the light(information) takes time to reach that person and hence. It almost looks like the event didn’t happen at the same time. “THE RELATIVITY OF SIMULTANEITY” Edit : This was later discussed in the new chapters: True Time
That is not true, the math of the signal traveling is already taken into account, the events do not only reach you at different times, but also happen at different times.
@@creativenametxt2960 Thank you for this clarification, I was struggling to understand how the time difference from the point of the moving observer wasn't simply a result of the difference in position. I think this should have been explained more clearly in the video, and to me Einstein's train thought experiment seems to be better suited to explain this difference in perception.
But then why does the universe wants keep the speed of light same and not the time when it comes to choose? Wouldn’t it be much simpler? And it’s hard to grasp that when it comes to light it won’t change it’s speed but rather change time (which looks like unchangeable in everyday life) how can my time be shorter than someone else’s time (not talking about biological time) I mean if I see someone for one second while travelling at the 60% the speed of light and then he is like “you saw me for more than one second”. How can you break 1 sec = 1+(some number) sec. this breaks maths in my head. EXPLAIN IF YOU CAN SO THAT I CAN UNDERSTAND @CreativeName Txt
@@javedansari-nb2pk "the Universe has no obligation to make sense to you" -somebody smart, probably If we assume that we can move our coordinate system and no physics laws changes, rotate it and even mirror it And also we can move time axis and nothing changes Then either Newtonian mechanics apply or special theory of relativity, it is just measured that Newton's laws don't quite work and special relativity does. Special relativity follows from those rather simple assumptions, if that's what you wanted as an answer to your question.
Question: 0:40 there are objects which are not moving relative to each other, so no relativistic effect should be existing between them, from my understanding. However, once we move the globe so that one of the outer edge objects like the box is at the center to see what's up from their reference frame, we see the other objects happening before from that object's perspective. How is that possible if no relativistic effect is present when dealing with static objects, relative to each other? The only answer that I can find to my question is that, if the objects are separated by a certain distance, then moving the pieces of the globe to fit the perspective of one of the observer does not show what event is happening first (from its perspective), but which one is "detected" first, due to the "latency" created by the finite speed of light (the amount of time the light takes to reach the observer). Someone, please enlighten me (pun intended)!
Thanks a lot for this instructive video! I still have questions and I hope that maybe someone in the public of this channel can give me some pointers to solve them. My main problems are (1) with the notion of « observer » and (2) with the rule that no frame of reference has more value regarding physical truth than another. (1) is the relativity of simultaneity a question of "observation" ? I understand that it is not a question of « observation » in the psychological or biological sense (i.e. cognitive bias or eye structure do not play a role), but even with this meaning of observation out of the way, I still don't really understand. If the relativity of simultaneity is explained by a difference in the reception of a signal, like it seems to be the case a first sight, in what way is it fundamentally different to some sort of illusion ? Two clocks, one linked to a camera and one to a recording device will register a difference between lightning and thunder but no one thinks that it means that the events producing the light and the sound wave are actually separated in time. Or two clocks linked to two cameras but very far apart will also register different times for the same lightning, but once again, it does not mean that this lightning « happened » at two different moments. If it is not explained by a difference in the reception of a signal, why is all the vocabulary centered around the « observation » and the « observer » ? Is it just a bit of a misnomer ? And, beyond vocabulary, then what does it mean ? (Which leads to my second problem). (2) Why isn't the frame of reference in which the event actually happens considered to be the real and privileged one ? If two lightnings strike two points in the same inertial referential frame and we have put two « lightning sensitive clocks » which both give the same time and have been triggered by the actual physical event (the lightnings striking the ground) why would any other referential frame be equally relevant ? Unless it's a question of « observation » (i.e. « reception of a signal », which brings me back to my first question). Thanks a lot for any future answer or help !
If you will point at a horizon with one index finger and trace a circle in the air by bringing your two index fingers together at twelve o'clock high. What can you do to eliminate the gap between your two fingers, which is part of the circle. For me pi is a physical event of simultaneity, but everybody just sweeps it under the rug and time transforms on.
just wondering, but from the perspective of the moving observer, are things no longer simultaneous (with respect to the non-moving observer) because the information that the further box has combusted takes a significant amount of time to travel to the moving observer, which causes the moving observer to perceive that the closer box has combusted first? also, in astronomy, i'm assuming the same thing happens when looking at 2 different supernovae for instance, where we might perceive 1 supernova to happen earlier than another, even though if we were in an unmoving reference frame, they might have happened at the same time. so how do we currently account for this difference and determine which supernova really occurred first? i'm assuming doppler shift only accounts for the expansion of space, but does it account for movement in space as well, and can we tell the difference?
If there are two combustion events and you clocked when signal (light) from them came to you, and you know how far away they happened, then you can calculate at what time (by your clock) they both happened: t_event = t_register - distance / c. And when different observers do such calculations, when exactly by their clocks events happened, then different observers may get different results, if the two events are not causally connected. So it's not just about observation, it's about assigning space and time coordinates to events.
Okay Question: about the set up with the rocket and the stationary man. you claim that the stationary man perceives the events as simultaneous and that from the frame of the rocket the events will appear in sequence. Heres the question, say that the stationary man has transmitting equipment , he transmits a 1 if he perceives the events as simultaneous and a 0 if he perceives the events as sequential. you are in the rocket. which of the following do you perceive and why? :: 1) you perceive the events as sequential and receive a transmission of "0" 2) you perceive the events as sequential and receive a transmission of "1"
So is this caused by the fact that objects in space can accelerate and decelerate relative to each other and light cannot? Which means when you move away from an object the light stays a constant speed but objects will move faster or slower relative to light? Causing the light from the object to take longer or shorter and effect your perception of when an event occurred?
guys I have a question, at 1:09 from the perspective of a moving person, the box on the right combust first, is it because it 'happens' first in his point of view or because he sees it first due to the object is closer so him so the light travels to his eye before the box on the left? basically what i'm asking is the difference in time happens for real or the light from the box on the right hits his eye first bacause it travels shorter, like if the moving person didn't look at the boxes would the boxes lit up at different time still?
okay honest question, how much of the misalignment of time is due to an actual shift in chronology, and how much is due to the time required for light to travel allowing us to perceive that something has happened. by that i mean, similar to stars in the sky going supernova, to our perspective we are only seeing it happen rigth then, but the stars exploded eons ago, and even if we had tried to travel to them they would no longer have been there by the time we arrived. so how much of the misalignment in chronology due to perspective is due to a true shift in time, and how much is simply due to increased travel time of light to allow us to perceive that the event has occured?
Let's say you have an individual who at the beginning of Your World line is 2 units to the right but stationary. How would you boost the perspective to be in this other individual world line? Would it still be a lorentz transformation or was you just shift the graph over?
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.
Can the simultaneity difference by perspective be explained just by the fact that information travels with the speed of light? So, correct me if I'm wrong: In our case, for blue: box2 combustion happens "later" than box1's merely because box2 combustion info travels at c and hence it takes extra time to reach blue who moved meanwhile.
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.
Some things can be illustrated with sound, yes, but there are important differences. Sound propagates with certain speed relative to air and wind, so when you're on a plane, sound from a static source will propagate in different directions with different speeds relative to you, and you can even move faster than sound. With light not so, in SR light speed is the same for all observers and no one can go faster than light.
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 😀
Okay, I was following until you mentioned things getting out of spacial alignment. For some reason simultaneity of events being broken makes some intuitive sense if you're familiar with time dilation. But, I'm really struggling to comprehend how moving will make two objects appear to be in different locations. Is there an actual example phenomenon of this? Maybe in like the large hadron collider? Which brings up another question, do particles obey relativity?
You're overthinking it. In your frame of reference your position x(t) does not change, x(0)=0, x(10)=0, but in a coordinate system of a moving car, your position x'(t) (with 0 meaning the car itselt) does change with time: like x'(0) = 2, x'(10) = 22. That's all, it's just ordinary motion, change of position as time passes.
hoping someone can help me out here. does the relativity of simulataneity arise from the fact that the speed of light is constant to all observers? or does it manifest as long as things are going fast enough? in the original train thought experiment, would things look different if the observer on the train had fired cannonballs instead of a light beam?
so do the boxes combust at the same time or at different times? dont they combust at the same time but the reason they look different to the moving observer is that it takes less time for the light from the closer box to reach the observer than the further box?
Hey Minutephysics I have a question for you What happen if we are at the edge of universe and look at our universe? Did we see big bang? If yes then if we go with expanding of universe can we see big bang rewinding?
1-We are at the "edge" of "someone's" universe and we can see the big bang, or at least close to the big bang in their position (the cosmic microwave background). 2- I dont understand what you mean in the second question.
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.
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!
I love this relativity series. It’s awesome that you’re making relativity accessible to people who would otherwise know nothing about it
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
“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.
For me, the "oh, I get it now" moment was at 2:18, when he connected relative event-time to relative position. Well done.
For me it was the combusting box. I always struggled with this. I still don't understand one thing though- are the boxes combusting at the same time no matter what, but the light from that event just takes longer to reach me if I'm further away/moving away from it, so the photons take longer to actually get to me? Or are the boxes actually combusting at different times from the POV of an external observer?
Ie- if two boxes combust at the same time, and nothing is moving, but one box is closer than the other, I'll see the closer box explode first from my perspective. However, someone at a different position that is equally far away from each box would see them combust simultaneously.
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.
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 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?
@@ASLUHLUHC3 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!
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!
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 like how the square thing moves stuff
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
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?
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! :)
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
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!
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...
Take that, people who comment 'first' !
You win today's Internet!
Agreed, Jeremy McMahan
‘first’ !
Blue shirt kid ?
1:30 "...Simultaneous events don't appear to happen simultaneously...": But this isn't because the speed of light is constant for all observers. It's because of the same effect that causes parallax.
The speed of light is constant because that's the natural speed of a electric field leap-frogging a magnetic field and propagating in some direction (or all directions simultaneously as in the case of an omni-directional antenna). Depending on my speed and direction in observing it can make it appear to be different... i.e. it's the same regardless of who observes it... but it won't "appear" to be the same.
If I move two antennas toward each other at 1/2 the speed of light, the signal will reach the other antenna as if it were traveling at twice the speed of light. Conversely, if they are moving away from each other at 1/2 the speed of light, the signal will never reach the other antenna.
Now within that leapfrogging is an oscillation that our eyes sense and distinguish as color.. and radios distinguish as field oscillations (magnetic and/or electric). A prism can slow down the propagation and make the colors appear more blue. Or, as astronomers claim, an expanding universe causes the colors to appear more red (the red shift). Or oscillating the magnetic field in the case of an electric motor can change the speed of the motor. But it makes no difference at what speed the motor's platform is moving as long as the generator is moving with it.
If the speed of light was not dependent on the speed of the platform from which it emanates or the platform from which it is observed, where can this color shift come from? It can't come from a change in vibration. It must come from a change in propagation... i.e. a change in the speed of light.
2:45 "...happen at different times...": Wrong. They happen when they happen... which may be the same time. They are observed when they are observed... which may not be at the same place, the same distance, or the same time. Depending on where they happen or where they are observed they my appear to happen out of sync... or if you're moving away at the speed of light relative the speed of the platform from which they emanate, they aren't observed to happen at all.
Well, I watched all four videos. I see nothing that disputes my comments.
Try this experiment. Have one mass moving in the +x direction at v. Have another moving in the -x direction at v. Their momentum is 1/2 mv2 each. They collide perfectly and stop simultaneously. The total momentum goes from mv2 to zero. They get hot. If v = c does m = E? Does m disappear...or spread out a whole lot?
I understood everything but from 0:00 I LOST IT
So at 2:45 if say the orange guy crossing t3 represent him pressing the button to "instantly" ignite the boxes, from blue guy perspective the 'righ't box wile ignite before orange guy press the button ?
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?
like position, the universe has no notion of absolute time either. it's always relative to something
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 ❤️❤️❤️❤️
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.
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!
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.
this idea hit me while studying pdes in the context of fluid mechanics. glad to see other people thinking about it ☺️🙌🏽
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.
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.
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!
2:30 Is this due to a Lorentz or a Galilean transformation here? Or is there a combination of both here?
Actually I think I answered my own question by going back to 1:56. you can see that the expression for x_new is just a Galilean transformation but scaled by the Lorentz factor which, unless you're going ludicrous speed, is ~1 and there's isn't really anything out of the ordinary happening. When you start going relativistic speeds, the Lorentz boost would make it seem you're moving away slower then from the normal Galilean transformation (I think you can see this at 1:14, the orange man is moving at less than 1/3c away from the blue man). Is this a result of "distances get shorter and times get longer, so speeds get slower"?
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...
The Table you've made is incredible!
Great work
If I play this video at half speed do I understand twice as much or cut my learning over time in half?
Yes.
Yes
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.
Here's something that the light globe suggested might happen but was not clearly addressed in the video. In my world view with stationary objects at a large distance from me, in the perspective of a person moving away from me extremely fast, are those objects still stationary with respect to me, or is there essentially dilation of the distance between me and the objects, indicating that from that other perspective those objects are NOT stationary with respect to me? If so, that might be the key that might help me intuitively understand how simultaneous events from stationary objects at large distances from me might not appear as simultaneous from a rapidly moving perspective.
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.
Get's a bit confusing to me at 1:04. Are we talking about what the blue guy observers or what me I, the viewer, who is at the same distance away from the boxes observes?
Even if the blue guy is not moving relative to the red guy, he observers the right box to combust first - because it is closer. What I'm getting at here is, pretend you are blind and you can only hear which of the boxes "explodes" first. You hear first the closer one, then the one further away because it takes a while for the soundwave to reach you - and so does the light.
At 1:31 he says the according to the orange guy all 3 boxes combust simultaneously, which is true only for me, the orange guy would perceive the furthest box to combust the latest.
So the box is twice perceived as being out of sync, once because it is further away, and second because of special relativity?
At 2:03, If I put speed of the observer zero, I get the result that tnew=told, removing special relativity alltogether, which is not what I would actually observe.... So we are not talking about what is observed at the same time, but what would be observed at the same time if I could magically insantly sense both phenomena regardless of the disantce?
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 :)
One of the very few videos on TH-cam I have to watch at reduced speed!
man that's a really neat Lorentz transform mechanism
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
*raises hand*
I have a question, it looks like the x-axis is being measured in the distance light travels in 1 second. Being one unit.
But when two objects(or perspectives) are at the same Ttime but different Xdistance (lets say 1 unit away) and 1 object turns a flash light on. On the grid it looks like they would be perceiving that light at the same time, although it should take 1 second for the light to reach the other object. (The 45° angle)
Again this is assuming the objects are 1 unit apart, but not moving over time
In the example you show at 1:31. You state that the orange person would perceive the 3 burning boxes simultaneously. I am not sure how that can be the case. Am I missing something??
Also love your videos
That is a factor in real life, but that's unrelated to what's happening here
So if the situation is like here 1:30 then combustion of bouth boxes to the left of the orange guy is happening simultaneously for him. But will he see a delay between combustions of these boxes one of which placed farther apart from the guy?
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.
Does this effect causality?
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!
Will the boxes actually combust at different times when considering a moving frame of reference OR will they combust at the same time, but it is just that the light of combustion is going to take longer to reach you...creating the illusion that they are combusting at different times?
It is akin to saying that Betelgeuce has gone supernova, but since it is 800 ly away from us, we just haven't seen it yet.
2:00 What if you're moving towards the moon from the earth at c/2 as soon as the explosion on Earth happened. Wouldn't this mean that the explosions would be in sync for you too because of the light catching up to you?
even if you are travelling at (1/2)c, light is still travelling at c, this constant speed. see, light doesn't catch up to you, as the light is travelling at a constant velocity to both observers. therefore the transformation still holds up - remember, in this video each tick mark in the x direction is ~ 300,000,000 m, and forms that 45° angle with the origin, whilst you, travelling at (1/2)c form a 67.5° angle with the origin. as long as the angle you make is not equal to or less that 45° in the x direction light doesn't "catch up" to you, and the lorentz transformation and its implications are not violated.
Consider the scenario when the red man sees two combustion at the same time in his frame of reference and the blue man sees two combustion at different points of time in his reference frame.
Suppose, if the blue man says "right" when the first box combusts for him in his frame of reference, and then later says "left" when the second box combusts according to him. Then what according to the red man, are the words said by blue man when both the boxes combust simultaneously for him (the red man) in his frame of reference?
Your space-type globe really needs to became a teaching accessory.
1:59 So if a friend of mine is in middle path between the mars and Jupiter and she turn on magic flashlights on each planet at the same time
From my perspective, when I receive both lights and discount the time of the light travel, mathematicaly, the flashlight on Jupiter has been turned on BEFORE the light on Mars?
Do they actually happen at different times for the moving perspective or does the moving perspective only perceive it as such because light has to travel to show the event?
the latter, that's the only way to maintain continuity. For example you could stop box B from combusting if you knew box A combusted and you knew they would do so at the same time. That's not the reality because the speed of light is constant. long story short box A and B combust at the same time but the light from box A hits you first
I'd love to see how Mark made that space-time globe!
This is a great series! You make great content.
I am loving this Special Relativity Series! Awesome! This should be a Grade 6 Physics 101. Much needed for the modern science kid.
1:26 this has nothing to do with how far the information has to travel right ? It literally happens later in his perspective not because it takes more time for it's information has to come but because of him moving shifts the space-time diagram. If so in real life, we (as the blue guy) would see the furthest box to burst in to flames much more later then what we have calculated because it happened later and the information also traveled a really long distance. Right ?
That obviously is a factor, but what he's referring to in the video indeed has nothing to do with that.
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.
Im amazed at that box dude. Way to simplify something hard to grasp.
Wait a second... If I have two for C events A & B happen for an observer C left of him at the same time, e.g. A at -1 and B at -2 (something), wouldn't those two events have to happen simultaniously for an observer D drifting apart from C? As the information moves with speed of light, sure, but if both signals from A & B reach C at the same time, don't they have to reach also D at the same time, as they always move with speed of light independent of the perspective themself?
For a Spacetime diagram, 45° is usually the speed of light, right? So for the two events A & B to happen at the same time for observer C, don't you need to put A at e.g. (5.-1) and B at (4,-2) so that the information of the event A has time to catch up to B in order to reach C simultaniously at (6,0)? And then also the events keep happening at the same time for an observer D, as the angle of 45° does not change. I mean, at 0:58 the two events do happen at the same time for the observer in the middle, but not because they are on the same horizontal line, but because they also have the same distance to the observer, thus the meeting point of their diagonal lines is also at the position of the observer. Would the right event be further away from the observer, it would have to happen earlier so that the information can reach the observer at the same time as the event at the other box (or on the time globe that the diagonals meet at the same point, which are gladly also the iron bars of the globe).
@silverrahul But my question was how it is if the signals of A and B reach C at the same time... Also no, just because A is closer to C than B doesn't mean its signal reaches C first. If A happens after the signal of B surpassed A, clearly the signal of A will reach C after B. Because the signal of A clearly would need to travel faster then light in order to reach C before B. In all perspectives.
@silverrahul They shall happen at the same time only for C. If A happens right when the signal of B passes A both signals should reach C at the same time. Therefore, B ofc has to happen before A.
Thats my whole point about the video at aprox 2:40. He says that all three events happen simultaneously. And that might be true for himself as an observer perpendicular to the room axis, but for C afaik the further right event happens after the events closer to it, as its signal reaches C later.
@silverrahul Yes, but from the perspective of C both events happened at the same time, so whats the difference to saying they happened simultaniously in the C frame? I mean in that system it is not like C has any way to get other information then the signals reaching it.
@silverrahul Aah ok, yeah thats right. Now I also understand how it is meant in the video, thx!
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
WAIT A MINUTE -- how do you track how things look relative to a moving object thats going in curvy directions. Do you do a squiggly Lorenz transformation, making the T axis a squiggly line?
Might be my favorite video from this channel.
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. ☺
0:57 Think this way
The match that lights is actually lighting at the same time but the light (information) of it happening can be delayed if the distances are larger and if the object is accelerating nearly the speed of light, so for person(a) near the match can see it almost instantly but for person(b) moving at 60% the speed of light, the light(information) takes time to reach that person and hence. It almost looks like the event didn’t happen at the same time. “THE RELATIVITY OF SIMULTANEITY”
Edit : This was later discussed in the new chapters: True Time
That is not true, the math of the signal traveling is already taken into account, the events do not only reach you at different times, but also happen at different times.
@@creativenametxt2960 Thank you for this clarification, I was struggling to understand how the time difference from the point of the moving observer wasn't simply a result of the difference in position. I think this should have been explained more clearly in the video, and to me Einstein's train thought experiment seems to be better suited to explain this difference in perception.
But then why does the universe wants keep the speed of light same and not the time when it comes to choose? Wouldn’t it be much simpler? And it’s hard to grasp that when it comes to light it won’t change it’s speed but rather change time (which looks like unchangeable in everyday life) how can my time be shorter than someone else’s time (not talking about biological time) I mean if I see someone for one second while travelling at the 60% the speed of light and then he is like “you saw me for more than one second”. How can you break 1 sec = 1+(some number) sec. this breaks maths in my head. EXPLAIN IF YOU CAN SO THAT I CAN UNDERSTAND @CreativeName Txt
@@javedansari-nb2pk "the Universe has no obligation to make sense to you"
-somebody smart, probably
If we assume that we can move our coordinate system and no physics laws changes, rotate it and even mirror it
And also we can move time axis and nothing changes
Then either Newtonian mechanics apply or special theory of relativity, it is just measured that Newton's laws don't quite work and special relativity does.
Special relativity follows from those rather simple assumptions, if that's what you wanted as an answer to your question.
Does this imply that time is subjective but space isn't?
Question: 0:40 there are objects which are not moving relative to each other, so no relativistic effect should be existing between them, from my understanding. However, once we move the globe so that one of the outer edge objects like the box is at the center to see what's up from their reference frame, we see the other objects happening before from that object's perspective. How is that possible if no relativistic effect is present when dealing with static objects, relative to each other?
The only answer that I can find to my question is that, if the objects are separated by a certain distance, then moving the pieces of the globe to fit the perspective of one of the observer does not show what event is happening first (from its perspective), but which one is "detected" first, due to the "latency" created by the finite speed of light (the amount of time the light takes to reach the observer).
Someone, please enlighten me (pun intended)!
Thanks a lot for this instructive video! I still have questions and I hope that maybe someone in the public of this channel can give me some pointers to solve them.
My main problems are (1) with the notion of « observer » and (2) with the rule that no frame of reference has more value regarding physical truth than another.
(1) is the relativity of simultaneity a question of "observation" ?
I understand that it is not a question of « observation » in the psychological or biological sense (i.e. cognitive bias or eye structure do not play a role), but even with this meaning of observation out of the way, I still don't really understand.
If the relativity of simultaneity is explained by a difference in the reception of a signal, like it seems to be the case a first sight, in what way is it fundamentally different to some sort of illusion ? Two clocks, one linked to a camera and one to a recording device will register a difference between lightning and thunder but no one thinks that it means that the events producing the light and the sound wave are actually separated in time. Or two clocks linked to two cameras but very far apart will also register different times for the same lightning, but once again, it does not mean that this lightning « happened » at two different moments.
If it is not explained by a difference in the reception of a signal, why is all the vocabulary centered around the « observation » and the « observer » ? Is it just a bit of a misnomer ? And, beyond vocabulary, then what does it mean ? (Which leads to my second problem).
(2) Why isn't the frame of reference in which the event actually happens considered to be the real and privileged one ?
If two lightnings strike two points in the same inertial referential frame and we have put two « lightning sensitive clocks » which both give the same time and have been triggered by the actual physical event (the lightnings striking the ground) why would any other referential frame be equally relevant ? Unless it's a question of « observation » (i.e. « reception of a signal », which brings me back to my first question).
Thanks a lot for any future answer or help !
If you will point at a horizon with one index finger and trace a circle in the air by bringing your two index fingers together at twelve o'clock high. What can you do to eliminate the gap between your two fingers, which is part of the circle. For me pi is a physical event of simultaneity, but everybody just sweeps it under the rug and time transforms on.
just wondering, but from the perspective of the moving observer, are things no longer simultaneous (with respect to the non-moving observer) because the information that the further box has combusted takes a significant amount of time to travel to the moving observer, which causes the moving observer to perceive that the closer box has combusted first?
also, in astronomy, i'm assuming the same thing happens when looking at 2 different supernovae for instance, where we might perceive 1 supernova to happen earlier than another, even though if we were in an unmoving reference frame, they might have happened at the same time. so how do we currently account for this difference and determine which supernova really occurred first? i'm assuming doppler shift only accounts for the expansion of space, but does it account for movement in space as well, and can we tell the difference?
If there are two combustion events and you clocked when signal (light) from them came to you, and you know how far away they happened, then you can calculate at what time (by your clock) they both happened: t_event = t_register - distance / c. And when different observers do such calculations, when exactly by their clocks events happened, then different observers may get different results, if the two events are not causally connected. So it's not just about observation, it's about assigning space and time coordinates to events.
You made this concept very easy to understand, and, the best part is, it seems so simple.
Okay Question:
about the set up with the rocket and the stationary man. you claim that the stationary man perceives the events as simultaneous and that from the frame of the rocket the events will appear in sequence.
Heres the question, say that the stationary man has transmitting equipment , he transmits a 1 if he perceives the events as simultaneous and a 0 if he perceives the events as sequential.
you are in the rocket. which of the following do you perceive and why? ::
1) you perceive the events as sequential and receive a transmission of "0"
2) you perceive the events as sequential and receive a transmission of "1"
It's 2). In your frame of reference events are not simultaneous, but in the frame of reference of that equipment they are, so you'll get "1" signal.
I see okay so there is a objective "Reality" its just things seem different from different frames.
2:15 That helped me so much in understanding this.
This is an amazing serie, thanks for all off this important and educate work!
So is this caused by the fact that objects in space can accelerate and decelerate relative to each other and light cannot? Which means when you move away from an object the light stays a constant speed but objects will move faster or slower relative to light? Causing the light from the object to take longer or shorter and effect your perception of when an event occurred?
This brilliant machine makes relativity much easier to understand. Thanks to your both.
guys I have a question, at 1:09 from the perspective of a moving person, the box on the right combust first, is it because it 'happens' first in his point of view or because he sees it first due to the object is closer so him so the light travels to his eye before the box on the left?
basically what i'm asking is the difference in time happens for real or the light from the box on the right hits his eye first bacause it travels shorter, like if the moving person didn't look at the boxes would the boxes lit up at different time still?
They actually do happen at different times
okay honest question, how much of the misalignment of time is due to an actual shift in chronology, and how much is due to the time required for light to travel allowing us to perceive that something has happened.
by that i mean, similar to stars in the sky going supernova, to our perspective we are only seeing it happen rigth then, but the stars exploded eons ago, and even if we had tried to travel to them they would no longer have been there by the time we arrived. so how much of the misalignment in chronology due to perspective is due to a true shift in time, and how much is simply due to increased travel time of light to allow us to perceive that the event has occured?
Let's say you have an individual who at the beginning of Your World line is 2 units to the right but stationary. How would you boost the perspective to be in this other individual world line? Would it still be a lorentz transformation or was you just shift the graph over?
If they are stationary relative to you, then it's just a shift. You can still use Lorentz transformation with v=0, it would be the same.
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.
Man, I love this series
MInd blown...I got goosebumps watching this video because I was able to understand.
simultaneously spontaneously. When you said that I almost had a seizure. Nice.
Can the simultaneity difference by perspective be explained just by the fact that information travels with the speed of light?
So, correct me if I'm wrong:
In our case, for blue: box2 combustion happens "later" than box1's merely because box2 combustion info travels at c and hence it takes extra time to reach blue who moved meanwhile.
I'm wondering the same thing.
how did you make this so easy to understand, youre a genius. well we all knew that already
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.
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.
I haven’t been getting my notifications for this channel in months. YT, fix it!!!
Isn't sound a good starting intuition for synchronization over distances? Or is what we call "speed of sound" due entirely to special relativity?
Some things can be illustrated with sound, yes, but there are important differences. Sound propagates with certain speed relative to air and wind, so when you're on a plane, sound from a static source will propagate in different directions with different speeds relative to you, and you can even move faster than sound. With light not so, in SR light speed is the same for all observers and no one can go faster than light.
2:25 its harder to visualize that points in space also are affected and appear to be moving rather than events
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 😀
Is this visual perspective? Like particles move faster when observed then not? Or time and space apart?
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
Okay, I was following until you mentioned things getting out of spacial alignment. For some reason simultaneity of events being broken makes some intuitive sense if you're familiar with time dilation. But, I'm really struggling to comprehend how moving will make two objects appear to be in different locations. Is there an actual example phenomenon of this? Maybe in like the large hadron collider? Which brings up another question, do particles obey relativity?
You're overthinking it. In your frame of reference your position x(t) does not change, x(0)=0, x(10)=0, but in a coordinate system of a moving car, your position x'(t) (with 0 meaning the car itselt) does change with time: like x'(0) = 2, x'(10) = 22. That's all, it's just ordinary motion, change of position as time passes.
hoping someone can help me out here. does the relativity of simulataneity arise from the fact that the speed of light is constant to all observers? or does it manifest as long as things are going fast enough? in the original train thought experiment, would things look different if the observer on the train had fired cannonballs instead of a light beam?
so do the boxes combust at the same time or at different times? dont they combust at the same time but the reason they look different to the moving observer is that it takes less time for the light from the closer box to reach the observer than the further box?
Where can I buy a Space-Time Globe?
Hey Minutephysics
I have a question for you
What happen if we are at the edge of universe and look at our universe?
Did we see big bang?
If yes then if we go with expanding of universe can we see big bang rewinding?
1-We are at the "edge" of "someone's" universe and we can see the big bang, or at least close to the big bang in their position (the cosmic microwave background).
2- I dont understand what you mean in the second question.