Relativity: how people get time dilation wrong

[@voranartsirisubsoontorn9010]

As a sixty years old lady with no prior physic education, I mostly can understand your words, that is great to me, Thank you.

[@eskiltester3913]

Yeah he's an amazing narrator Even I understand it somewhat 😂

[@GP-qb9hi]

I'm a 3-months old infant and understood it on my first watch.

[@DragonFanngg]

I'm a 9 y.o. panda and don't even understand the idea of human communication and articulation, I still was able to comprehend most of the things he talked about. Cheers!

[@kensonwesley]

ship

[@raptorm8242]

Ok boomer

[@danheidel]

I really enjoyed this video, as it cleared up some of the ambiguities I had about relative reference frames and relativity. However, I would make some suggestions on how it's presented. The constant use of Observer 1 and Observer 2 and quickly jumping back and forth between who sees was was almost impossible to follow, It quickly just becomes noise stew. I had to rewind and rewatch some sections several times to make sense of what you're saying. E.g.: what you're saying at 9:32 - it's extremely hard to parse: "That means that the transformation of what Observer 2 sees compared to what Observer 1 sees depends on location. Observer 2 sees more time elapsed than Observer 1 sees at Observer 1's location, but sees less time elapsed than Observer 1 sees at Observer 2's location." That would be fine in written material but is very hard to follow when listening to a voice while also watching the animations and trying to read the text. I would recommend you use actual names like Alice and Bob rather than numbered people. The viewer is already having to follow the equations, adding in numbered people and locations is too much numeric data to have to listen to all at once. Here's a suggestion for an easier to parse phrasing: "That means that the transformation of what the two observers see depends on location. Bob sees more time elapsed at Alice's location than she does. However, Bob sees less time elapsed than Alice does when looking at his location." Using the pronouns helps to avoid the rapid repetition of Observer1 and Observer 2 to the point they all just blend together.

[@geoffb1418]

Very helpful. Thanks

[@frankdimeglio8216]

@@geoffb1418 THE ULTIMATE, TOP DOWN, BALANCED, THEORETICAL, AND CLEAR MATHEMATICAL PROOF OF THE FACT THAT E=MC2 IS F=MA: The BALANCE of being AND experience is essential. Consider what is BALANCED BODILY/VISUAL EXPERIENCE. (SO, think about what is THE EYE.) The orange Sun is lava ON BALANCE !! THINK. Think about what is THE MAN who IS standing on what is THE EARTH/ground. Think about TIME. NOW, think about what is THE MAN who IS in what is outer "space". (Very importantly, outer "space" involves full inertia; AND it is fully invisible AND black.) Think about what is THE SUN. The stars AND PLANETS are POINTS in the night sky. Carefully consider what now follows, as E=MC2 is CLEARLY and NECESSARILY proven to be F=ma ON BALANCE. Time dilation ultimately proves ON BALANCE that E=MC2 IS F=ma, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Time is NECESSARILY possible/potential AND actual IN BALANCE, AS E=MC2 IS F=ma; AS ELECTROMAGNETISM/energy is gravity ON BALANCE. Gravity is ELECTROMAGNETISM/energy. Great !!!! QUANTUM GRAVITY !!!! E=MC2 IS F=ma. This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual IN BALANCE. What are THE EARTH/ground AND THE SUN are CLEARLY E=MC2 AND F=ma IN BALANCE. Very importantly, outer "space" involves full inertia; AND it is fully invisible AND black. The stars AND PLANETS are POINTS in the night sky. GRAVITATIONAL force/ENERGY IS proportional to (or BALANCED with/as) inertia/INERTIAL RESISTANCE, AS E=MC2 IS F=ma; AS ELECTROMAGNETISM/energy is gravity. Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS E=MC2 IS F=ma; AS ELECTROMAGNETISM/energy is gravity. BALANCE AND completeness go hand in hand. It does ALL CLEARLY make perfect sense. GOT IT !!!! THE SKY is BLUE, AND THE EARTH is ALSO BLUE !!! Great !!! NOW, think about WHAT IS THE MAN who IS standing on what is THE EARTH/ground. Perfect !!!! Gravity AND ELECTROMAGNETISM/energy are linked AND BALANCED opposites, AS E=MC2 is CLEARLY proven to be F=ma ON BALANCE; as ELECTROMAGNETISM/energy is gravity. Gravity is ELECTROMAGNETISM/energy. It all CLEARLY makes perfect sense. (Balanced inertia/INERTIAL RESISTANCE is fundamental. Energy has/involves GRAVITY, AND ENERGY has/involves inertia/INERTIAL RESISTANCE.) "Mass"/ENERGY involves BALANCED inertia/INERTIAL RESISTANCE consistent with/as what is BALANCED electromagnetic/gravitational force/ENERGY; as E=MC2 is CLEARLY proven to be F=ma ON BALANCE; as ELECTROMAGNETISM/energy is gravity. Accordingly, ON BALANCE, objects (AND WHAT IS the falling MAN) fall at the SAME RATE (neglecting air resistance, of course); as E=MC2 IS CLEARLY F=MA ON BALANCE !!!!! It also makes perfect sense that the PLANETS move away very, very, very slightly in relation to what is THE SUN. (The stars AND PLANETS are POINTS in the night sky.) Great. E=MC2 is CLEARLY proven to be F=ma ON BALANCE. Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS E=MC2 is CLEARLY F=ma; AS ELECTROMAGNETISM/energy is gravity. Great !!!!!! Carefully consider what is THE MAN who IS standing on what is THE EARTH/ground. Touch AND feeling BLEND, AS ELECTROMAGNETISM/energy is gravity. Magnificent !!! E=MC2 is CLEARLY proven to be F=ma ON BALANCE !!! By Frank DiMeglio

[@frankdimeglio8216]

TIME dilation ULTIMATELY proves ON BALANCE that ELECTROMAGNETISM/energy is gravity. This necessarily represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual IN BALANCE !!! Indeed, TIME is NECESSARILY possible/potential AND actual IN BALANCE; as ELECTROMAGNETISM/energy is gravity ON BALANCE !!!! Great !!!! By Frank DiMeglio

[@vaishnavi2608]

Thanks for this That was exactly the point in the video where my brain went into a loop trying to figure out the statements

[@alchemy1]

Oh really? So what did he prove in one sentence? You gonna tell me or not?

[@Bassotronics]

time dilatation can be observed when your wife says she needs 5 minutes to get dressed. On your watch it passed 45 minutes, but for her it's still 5 minutes.

[@Enderia2]

wow she runs fast

[@sono1951]

So there's just wife jokes everywhere for this time thing huh.

[@JustMe-vz3wd]

"wife jokes" are another channel, bro...

[@ludvighp6235]

@Martin willemse No one read that, if you truly understand it Then you can explain it shorter

[@popscola2574]

@Martin willemse plz make shorter version

[@arnesaknussemm2427]

A bold attempt but just as confusing.

[@dreamdiction]

It will always be confusing because relativity is bullshit.

[@darkseid856]

@@dreamdiction why the fuck you even decided to open a video with "relativity" clearly written on the thumbnail and title .If you think it's bullshit then don't come here . Go and make "theories" with your flat earther buddies .

[@cinegraphics]

@@dreamdiction Thank you for having brain. Finally someone. Eight billion people on the planet and only a dozen of them have brain. Yes, relativity is bullshit. And I like to visit places that "explain" relativity and call it bullshit. Just to interfere with the propaganda. Science should equal to truth. But it has turned into propaganda. That's not real science.

[@wav2806]

@@cinegraphics "I'm too stupid to understand it therefore bullshit."

[@DM-rc4yu]

@@cinegraphics So when did this turning into propaganda happen? With theory of relativity being over 100 years old and you writing this on a computer or a phone thanks to science and all...

[@ThoughtShaman]

Thanks for the video However, the use of the word "sub" constantly creates a lot of auditory noise detracting from the content at hand making it harder to concentrate. "t 1" conveys the same meaning as "t sub 1" without the noise.

[@haldial2459]

ThoughtShaman I think a further communication problem is the lack of direction given in the tone of voice. Often the words and labels are less important than the intonation to help the listener follow the arguments.

[@ronclass1782]

But that's not the right way to say it. T sub 1 is the right way.

[@ZeroG]

Ron Class There is no right and wrong way to say it. He makes a valid point. The word “sub” adds no helpful meaning to the explanation.

[@melgross]

Zero-G it’s the proper way to say it.

[@renx81]

@@melgross What is "proper" depends on your goal. If you goal is to be pedantic, then sure, but in the context of educational content such as this your goal should be to be as easy to follow as possible. Everyone can follow the formulas on screen without the excess use of the syllable "sub".

[@Laceykat66]

Wow, good thing I watched this. I was GOING to be "cavalier" about using Relativity just this weekend, but the video was ample warning. Thanks

[@Hambone3773]

Lol.

[@TerryProthero]

@Laceykat66 Yeah, when I was younger I went through a rebellious phase where a I did a lot of sloppy physics. It's not something I'm proud of.

[@dmitrysofronov8624]

@Laceykat66 But you were right, weren't you? This video doesn't prove anything.

[@lhommedieu5489]

Abolutely knew this comment would be here.

[@chrisbarringer9886]

Haha

[@jonskowitz]

I'm wondering how many times I'll have to watch this before it 'clicks'

[@EpicBunty]

Its relative, but the faster you watch it the more confused u will be.

[@AstroRamiEmad]

y times if you run at the speed of light ... I've tried it

[@KuK137]

@Justa Fool 0/10000 troll, matey

[@flyonbyya]

jonskowitz I thought the EXACT same thing!!! I’d certainly require some upfront education before I’d even attempt it

[@marianskodowski8337]

A great deception in physics started with Lorentz, no doubt ... but it is the whiskery troll who's trolling physicians for 100 years now

[@deadringer-cultofdeathratt8813]

**observer 3** “You wanna know what I think?”

[@evilcowboy]

lol

[@richardlinsley-hood7149]

Ah, the triplet paradox raises its hand.

[@spring9603]

@deadringer-cultofdeathratt8813 😂😂😂 ❤

[@christianott1586]

First time using the 0.75 speed setting - totally worth it

[@bornafarazmand]

What you answered was totally different from what you asked!! You questioned the reciprocality of time dilation, but ended up calculating twice from observer 1's perspective. "how observer 2 sees what observer 1 sees at observer 2's" is not the same as "what observer 2 sees of observer 1".

[@shiken69420]

I mean it was clearly written on the slide, he just said it wrong but it should click ,his explanation was marvelous as it cleared a lot of misconceptions

[@silentwraith506]

Me and my pal did a shot everytime he said T sub 1... He is now dead!

[@justsomeguy892]

F

[@prg54]

ajajajajaja

[@Nevir202]

Is that because you experienced time dilation and he didn't?

[@mrloop1530]

RIP your pal

[@jameslane2326]

Everyone always told me I was smart, then i watched this video and found out that everyone was wrong :(

[@corwin-7365]

Or... perhaps... the explanation just wasn't that good (given your starting knowledge).

[@demandred1957]

Exactly..

[@potencjau6571]

dude, its relative XD

[@cloudv9879]

@@potencjau6571 🤣

[@gtab1268]

@pyropulse That's pretty cool man!

[@christopherfernandes4401]

I took physics at university over 40 years ago and still had to watch this 4 times before I could grasp all of this lecture. Helps that I am still good at math. But as a senior it does take longer than it would at university. years ago.

[@LemarFrench]

Question...as it's being professed as REALITY...what examples are there of this effect in nature? In nature, the faster I travel through space...will always reduce my time of travel...theoretically, time dilation works, but realistically...it doesn't

[@zenastronomy]

​​@@LemarFrencheverywhere. astrophysics, gps, satellites etc all require time dilation to be taken into account every day and satellites adjusted otherwise none of them would work. within a day all gps would be out of sync and accuracy anything travelling fast or over great distances usually anything in space man made or natural

[@roberthambrook150]

What is that line from Big Bang Theory that Penny says to Sheldon. Something like "I know you think you are explaining things Sheldon but your really not".

[@aimzf20]

@pyropulse it's not, it just was made unfunny by the amount of laugh track used in later seasons. Also you sound like an insecure pedantic asshole

[@pintificate]

This bloke has mastered the art of making simple concepts sound unbelievably complicated.

[@control21]

If you think that the subject of the right application of the concept of time dilation is simple, then you just don't undestand it.

[@stargazer7644]

@@control21 It may be detailed, but it isn't really complicated. You just need to keep your p's and q's straight.

[@shiken69420]

What he explained ain't so simple dude concepts dude, he cleared s big misconception a lot of beginners encounter in theory of relativity

[@pronounjow]

Definitely need to rewatch. Thanks for posting this video. I've been confused about this.

[@jessstuart7495]

I've always struggled with coordinate transformations. I think the use of the standard configuration (1 space dimension instead of 3) adds additional confusion for beginners. It isn't obvious to me how you would extent this back to the 4-D world. Can you just treat each velocity as the component velocities directed along the x, y and z directions? Does the time Lorentz equation depend on just the magnitude of the velocity? Or are the velocity components combined in a different way? Granted, I've never taken a course on Special Relativity, but I think most students are fed a dumbed-down version of special relativity, which actually makes it harder for people who really want to dig into the details to follow the math and understand what is going on.

[@Ni999]

Jess Stuart I'm pressed for time in real life, wanted to cover some tips, and don't want you to feel like my curt responses are condescending - just in a hurry over here. Dumbed down? Maybe. But more like just getting the degenerative cases clear first. Courses I took always stressed the importance of that because as you add conditions, the gotchas come fast and strong unless the basics are crystal clear. Over the years I've had to return to the basics myself - it's amazing how quickly you can overlook something if you take for granted that you remember the basics. I see at least three questions in your overall question about positioning (and fwiw, I think you are asking the right questions). Let's concentrate on 3D motion in space (in 4D with time). One of the most basic things to remember is that cases such as the one in this video must not include acceleration for the observers, only constant velocity relative to each other. You can believe that you are (relatively) stationary even if you are at a constant, uniform velocity but if you are accelerating in any way, you can look down at the inertial navigation unit that I installed by your clock and then know that you are accelerating - the case shown here does not apply to you. Next case - ok, you are not accelerating. From your point of view, you are not moving. If the one you are observing is moving in 3 space dimensions relative to you and is on a straight line - turn your head. You're a point, they're on a line, by definition you must both share a common plane so there can be no third spacial dimension to worry about. If they are accelerating along that line, the constant velocity form shown here does not apply. If you cannot fit yourself and their track of motion along a single plane, change in direction must be occurring. Change in direction means by definition that there's an acceleration involved. Either acceleration means that the case shown here does not apply. Getting spacetime world lines right is a pain in the neck - three space dimensions become a single dimension describing change. I recommend the 3blue1brown math channel to really help with visualizing coordinate transformations. It creeps into a lot of his videos and you'll probably get hooked, watch them all, and not miss anything. Then you'll have a whole new set of questions lol. The good Dr. here always tries to either point out or at least remind that he's working with simpler forms. Sometimes it can go by quickly, but it's there, and you are right, these cases are simplified so that only a few terms in more complex relativity math can be brought into focus. But that's OK because you gotta start with the basics and even the basics can get you into heavy lifting in no time. Don't discount the possibility that I screwed something up in this long but hurried response. Hopefully someone will chime in quickly if I did - otherwise, I think I have you pointed in the right directions even though I probably didn't answer anything in detail. (And yes, the inertial navigation unit I installed is magical - it is convinced that it's stationary so long as there is no acceleration on any of the three axes and it's doing that without the gyros drifting or showing it to precession and it's immune to the local gravity because you're not on a planet - you're on a plane in Imagination Land so it's OK for the nav unit to be a little magical. Whether magical or not, real world or not - you can measure to determine if you are accelerating.)

[@howardOKC]

I rewatched 3 times and planning to do another 10 times.

[@farid7080]

Jo Reven0]

[@cinegraphics]

Of course you're confused. It's not correct. It appears that observers have symmetric views on the other observer's clock... but they don't. Because when they meet up, one of them will have his clock really slower. So one of them was right. The other was wrong seeing the opposing clock slower. It's not symmetric. In reality, it's asymmetric.

[@JamieRChamberlain]

I wish I would have had someone like you as my physics instructor as a teen. I could see my life having taken a seriously different direction. I was a number crunching machine and had such an open imagination. 😊

[@91722854]

May Physics always be one with you!

[@stephenphilbin3919]

His job is to make the subjects of the video be as comprehensible as possible; a _"Teacher's"_ job is to make the simplest of concepts seem as incomprehensible as possible in order to make teaching it take weeks, rather then the hours it ought to take.

[@neelmodi5791]

I cannot express the extent to which I agree with you.

[@sinisamilisavljevic8833]

Keep going. Leave bad teachers behind. They were not there to be followed. Every teacher somehow hopes that his students will be better than he was. That s why they teach in the first place. At least that's why I was teacher for 11 years, until civil war in former Yugoslavia interrupted it. I know what mistakes I made. Your teachers also know their mistakes, and they wish they never made them. But you are here to correct those mistakes on yourself. Go your way and don't worry about some previous steps on that road long time ago.

[@Bissonnette754]

no you're just smarter than the average and a teacher need to move at the speed of the majority.

[@tarmaljed1609]

Mixing labels is very confusing. T_moving is the time of the stationary guy whilst T_stationary is the time of the Moving guy (this is why when someone reads your equation T_moving is greater than T_stationary, it goes against what we usually read). At 2:43 when you refer to "time of someone moving" it is in fact not T_moving at all, but T_stationary you refer to (which can only be noticed by people who are not targeted by the video). This is even more confusing knowing you can apply the reasoning in reverse (that's the point of relativity). You can FEEL smarter by making others feel dumber, or you can BE smarter by making others feel smarter. That's also relativity.

[@josephmoore4764]

There are two good ways to resolve the paradox that "Both observers see that their own clock is running faster than the other observer" The first is that there is no notion of simultaneous with two reference frames of different velocity. What one frame considers to be "now" is in the future of another reference frame. The second only helps in getting over the mental hurdle. There is a third frame of reference where both observers are moving away from each other with equal speeds. At this frame of reference both would have clocks that seemed to be ticking at the same rate.

[@KirigakureM]

Or the twin brothers paradox is not a paradox if you consider that all your internal functions are also altered by gravity and velocity so one can age way slowly than others depending on those factors.

[@chrismcgraw2112]

This actually helps a great deal, Joseph. Thank you.

[@WallysBro369]

@@chrismcgraw2112 kzbin.info/www/bejne/qafaiH6fbtiGd6M

[@Dislob]

So you're saying its relative? MINDBLOWN

[@shields765]

​@DolphinsWIthIgloos Thanks, it makes sense to me that in the twin scenario, the reason that the traveler ends up younger has to be related to the change in his situation (acceleration, force, kinetic energy, or whatever). Otherwise you could just say that they each traveled away from each other and then back together, from their respective points of view. But this video didn't really explain that, right? Or did I just not follow it (which is likely).

[@dariscar5218]

"begin by putting up the most basic and general equations of relativity" *Head explodes*

[@potencjau6571]

actually in somewhere around half of film all become a bit clearer

[@what2a8guy]

pyropulse I’m willing to bet you came here to the comments section just to try to find someone like this guy who admitted to not understanding the concepts in the video so that you could leave a stuck up comment like that and feel good about yourself. Grow up man😂 it’s comments like yours that make youtube comment sections such a mind fuck to read.

[@epitaphboi4816]

What aGuy For real, fuck pretentious assholes.

[@benjaminfeddersen7937]

A pet peeve of mine: Mathematical equations don't explain WHY we make certain observations. They are formalizations of WHAT we should expect to see when we look. The Lorentz equation doesn't explain the WHY of time dilation, it merely describes the WHAT. Why the Lorentz equation and not some other equation? THAT's the "why" question.

[@GasperRazdevsek]

It's not that hard. You just have to be ultra mega extremely careful when doing the math :D

[@SimonClarkstone]

Watching Wikipedia's animation of the Lorenz transform helps too.

[@KCLBrunel]

Yes, be mega mega careful and remember it's super subtle. He's easy to joke about, but he's pretty good too.

[@alphagt62]

So, basically, everything is moving, even if it doesn’t seem so from our perspective. It’s all relative. So this explained time dilations due to speed, but what about time dilations due to gravity? The closer you are to a massive object, the slower your clock moves, even if both locations appear stationary. The clock on GPS satellites runs faster than clocks on the ground, and must actually be adjusted to stay accurate. Even though they are in Asynchronous orbit, and stay stationary over the same spot on the ground.

[@nicolez581]

Does that mean that time speeds up the further away from a massive object you are (earth for example), so does that mean you'd age faster the further away from a massive object?

[@KCLBrunel]

@@nicolez581 Yes, but that's as seen by an observer on Earth. You would still age at your usual rate in your frame of reference. It's just that if you compared your age with people on Earth (who would also age at their usual rates in their reference frame) they would seem to age slower, when observed from your reference frame. Anyway the difference would be trivial in the case of the Earth (not enough mass).

[@StanleyKowalski.]

Dr Lincoln, you are a great teacher, thank you

[@neillibertine3044]

Basic tenets of natural philosophy are; 1. Law of entropy is fundamental law and it is unification of gravotational force, electric force, black-body radiation law, divergence law, law of motion, structure of fundamental elements. 2. General theory of relativity and Quantum mechanics are description of phenomenon without entropy or no loss or perpetual motion. They are same and there is no need of reconcilation of these theories. 3. Phenomenon are in classical domain, general theory of relativity and quantum mechanics are ideal case and thus not observable. Theory of relativity needs many assumptions which are contradictory or unprovable thus false theory. 4. There are no two types of charge like two types of matter which arises when one solve Laplace's equation, field without source but that lacks time component. In nature only force without energy loss is magnetic force. There is electric force but it like thermodynamic pressure eventually die out. 5. Entropy is decaying of force or ceasing motion. Only way to counter entropy is cyclic or periodic motion that negate volume expansion and restore system but introduce temporal component, frequency. More the frequency more the entropy. 6. Without force there is no continue motion, mechanical force is due to heat and electric due to charge. Conservation of energy is not correct but equality of power as it is product of force applied and rate. Both force and rate can increase entropy but in cyclic only rate.

[@neonsilver1936]

This was my first introduction into those basic lorentz tranformation equations. Honestly, this (literally just talking a bit about the math involved and explaining it unambiguously) was one of the most helpful introductions I think I could have found. Thanks!

[@swde4793]

This guy im so proud of. look how much better he has gotten since his early vids.

[@IntraFinesse]

I thought Dons early videos were excellent.

[@danny5018]

If you need it to be more simple think of it like this. Physically draw a S (Swiggle) on a piece of paper and then draw an I (Straight line). "S" is the shape of the route that the first beam takes. "I" is the shape of the route of the second beam. The start of S is equal to the start of I just as the end of S is equal to the end of I. They are both moving at the same speed, the letter (which I used as a picture to illustrate the path or route of the beam) is an optical illusion because the distance per second covered is the same.

[@dejanatanackovic909]

I really like your videos and I watch them regularly.. You make most videos understandable to most people (it is, of course, expected that viewers have some "basic" knowledge about the thematics) .. But this video really left me with scratching my head.. When i expected you to explain how the 2 clocks may both seem to run faster/slower the video pretty much ended.. A confusing video, or maybe I'm just to sleepy right now to "digest" it :) .. Keep up the good work!

[@BainesMkII]

The problem is that the explanation given doesn't really work as a regular person's explanation of what exactly is going on. It just says "this is why the math says it isn't a paradox," which can even have the undesired effect of making it all look even more esoteric and confusing. In that regard, it is pretty lacking in comparison to some other relativity videos, including some other Fermilab videos.

[@nachannachle2706]

+Dejan A. Well, it is a matter of PERSPECTIVES. Both observers observe that their times are different as an intrinsic effect of their "displacement" in space. I do think that it is important to keep in mind that although SR makes sense mathematically, it become more understandable empirically ONLY in the light of GR. It's not that their clocks tick at slower/different rates, its more that they are traveling on different world lines in space-time.

[@Theo0x89]

Let me illustrate what I said in another comment about how relativity of simultaneity is the crucial feature that is ignored in this paradox. The moving clocks at 6:26, synchronous for the moving observer, are out of sync for the resting observer, which looks like this at t=0s (every number represents position and reading of clocks viewed by the resting observer, clocks at the position of the observers are in parentheses, negatives are black): 　➅　➂　🄞　❸　❻ 　Ⓞ　Ⓞ　🄞　Ⓞ　Ⓞ At t=2s (1s for the moving observer): 　　　➆　➃　⑴　➋　❺ 　➁　➁　⑵　➁　➁ Now you can check that time dilation is mutual. It is obvious for the resting observer looking at the moving clocks. To see that the resting clocks are ticking more slowly for the moving observer, simply notice that ➃ (moving) coincides with ⑵ (resting), so the moving observer sees the resting clocks ticking at half-rate. This is a depiction of the math from the video that solves the paradox and can be understood without manipulating the formulas of the Lorentz transformation.

[@KasiusKlej]

I found this lecture indigestible, sorry to say. Remembered how Feynman once said in one of his lectures, and it gave me some comfort. Sometimes it's not the student that does not understand, it's just that the professor does not understand it either. Yet this Lorentz formulas seem to understand the twin paradox. Professor says the formulas solve the paradox. Well I still don't get it. It's confusing how one state the way about explaining the paradox. Because in this twin paradox, first it's the twin who travels around accelerating about all over, that's youthful. Then professor just throws the formulas on the table. That explains it. So now I'm looking at the formulas wondering why it's not the other twin that's youthful. I'm not very good at physics. Couldn't the professor point out certain factor in the formulas that solves this twin paradox. The youthfulness side of the equation, please.

[@ABaumstumpf]

Kasius Klej - that goes to show you didn't understand it and you have an inflated ego. Some things need effort on YOUR side to understand. And this video explained it correctly: both observers see time flow slower for the other party. That is what is happening. The flow of time is not a universal thing - it depends on the reference frame - hence the name relativity.

[@Skunkwerx]

Einstein came up with this 105 years ago. 105 years later, with all the technology and education thats come with it, and I still can’t wrap my head around basic math, if only to enable me to understand that mans genius in its true entirely.

[@AstroRamiEmad]

I GOT REALLY CONFUSED about the position! I rerun the video many times. And I do understand the concept of relativity. This have me go crazy. Please explain to us in a deeper conceptual video about what the x is doing there

[@9twisted]

I'm in yr 7 but me and my friend go to a yr 11 and sixth form tutor to talk about what u talk about and he teaches us new things too! U just earned yourself a new sub!

[@wcottee]

Even though I love these videos, I hate when people use equations to "explain" things. Equations are a DESCRIPTION and not an EXPLANATION.

[@ryanhill906]

Right, because the Lorentz transforms really just make the equations result in what we see (i.e. approaching light speed but not reaching it). Not that I'm saying they're *wrong* they just don't explain it.

[@JonathanDLynch]

Thank you for this comment.

[@chemicallystimulated476]

But for people who are good with math it can be satisfying as the explanations

[@chemicallystimulated476]

But for people who are good with math it can be satisfying as the explanations

[@garbles46151]

I’m the opposite. The equations help me “see” things more clearly than using imprecise words. Math is an exact language for the most part and helps remove ambiguity.

[@DavidJones-hk1uj]

Unfortunately this does not provide any resolution to the paradox. If time dilation due to motion were a real effect then it would be possible to bring clocks 1 and 2 together and observe a difference due to them running at different rates (otherwise the effect is virtual rather than real). However, at 10:08 the speaker says that both observers see the remote clock as running more slowly, which, if the effect is real, is a paradox. When bringing them together they would read the same time, since for one to read less than the other would require that clock's reference frame to be in some way absolute - which violates the postulate of Special Relativity which say that all reference frames are relative and equally valid, and that no absolute reference frame exists. So, there is still a paradox, which indicates that time dilation due to motion is a virtual (observed) effect, rather than a real one.

[@AMC2283]

One is subject to accretion one isn’t

[@hyawill8944]

David, You are correct in my opinion. And there is one universal frame of reference where time flies at its highest velocity/rate.

[@briansummit3818]

Conclusion of the video: "Further, they both agree that the remote person’s clock is slower." Isn't that the troubling paradox described at the beginning of the video? How can each see the other's clock as slower without creating separate timelines? (Enjoyed the video and math, but would love to know how the paradox is resolved!)

[@corwin-7365]

Reality is what you can perceive and measure... If I hit you with a shrink-ray, I'd say that I remain unchanged and you shrunk to a small size. But you, with your tiny shrunken measuring sticks, would say the you were normal and that I (and the rest of the universe) had grown large. We'd each see the universe in different, apparently contradictory ways ("I'm normal size and you are tiny," says I; "No, I'm normal and you are huge," says you). Yet, our interactions will all be consistent. So it is with Special Relativity. A moving thing (whether it is a person or a rock) becomes time-slowed, shrunken in its direction of travel, and is moving relative to the space through which light travels at a constant speed. That means that if I (who are stationary and normal) saw you moving past me all shrunken, time-slowed, etc then I'd know that the way you perceive and measure me and the universe would be distorted. What would perceive (i) yourself, (ii) the speed of light, and (iii) me (and the universe) looking like through your distorted eyes and measuring devices? It turns out (when you do the sums) that: (i) You see/measure yourself as normal sized and normal timed ((no big surprise there, since the clocks you are carrying with you are time-slowed the same amount as you, and your measuring sticks are likewise shrunken)). (ii) You see the speed of light as the same in all directions ((a little weirder, but if I do the sums using your slow clocks, short measuring sticks, etc that's what you get)) so you consider yourself as stationary. (iii) You perceive me (and the rest of the universe) as coasting past you with the same velocity that I saw you going, but in the opposite direction, AND you measure me to be time-slowed, shrunken, etc. To summarise: I know that I am normal and stationary, and that you are moving and distorted. But when I do the sums to work out how you see the universe through your distorted eyes and measuring devices, it turns out that YOU think your are normal and stationary instead, and that I am distorted!!!

[@adr3ns]

@@corwin-7365 the problem is measurement itself. Humans agreeing on a standard of measurement doesn't make that standard truly objective. The example you give would play itself out much differently if you could isolate a human from inflation. The universe would expand around them & they would objectively stay the same size while the universe objectively expanded around them. So in that context the shrinking person would be objectively correct & the subjective perception of those expanding with the universe would be objectively false. 😊

[@SimonClarkstone]

The differently-moving observers have different ideas of what simultaneity is. In everyday physics you are accustomed to different observers disagreeing on where two events at different times happened in the same place. If I'm on a moving train traveling rapidly north and tap on the north edge of the window then the south edge, I think the second tap is south of the first tap. An observer outside will measure the tapping position relative to the ground and because the second tap was a few seconds later the second tap actually 100m *north* of the first tap. We disagree on which event happened north of the other because we are moving at different speeds and the events were at different times. Relativity keeps that but also does the same thing with time and space swapped: observers can disagree on which event happened before another because they are moving at different speeds and the events were at different places. (Incidentally, if no-one is exceeding the speed of light, then if any observer sees the events happening at the same place then all observers will agree in which order they happened in time, and if any observer sees the events happening at the same time then they'll all agree which order the events are positioned in space.) I recommend you look at Wikipedia's animation of the Lorenz transform too.

[@ryanhill906]

@@SimonClarkstone We wouldn't disagree though, because to determine which was north and south, even in the train you'd have to first plot your position on a map, relative to when you tapped each time. Otherwise train-you is making things up without any frame of reference. Thus, we would agree which was north of the other.

[@FrancoisBothaZA]

I encountered this "paradox" on my own when I was 17 and couldn't figure out the solution by myself. When I eventually met a physics professor he told me it was due to acceleration being applied only on 1 object. That totally didn't make sense to me. There is no acceleration to speak of. In the end, this fatal moment made me decide to study actuarial science instead of physics after school. It's a decision I kind of regret and I still wonder what would have happened if I got a satisfactory answer from that professor.

[@azlastor]

His professor was wrong and didn't comprehend the question, also he clearly knows about twin paradox already.

[@makego]

To bad the professor didn't make clear the distinction between special and general relativity. General relativity includes acceleration, special relativity is an inertial (constant velocity) frame of reference, no acceleration. The (non) paradox in this video is SR, no acceleration.

[@stephanverbeeck]

You got it right, the guy in this video knows there is a problem but again explains it wrong. The professor you talked to also explained it wrong. Did the same at about the same age and got from the professor at the unif in Hasselt a reference to a book that I should read. He to did not grasp time paradox not being possible. The simple truth is that when the rocket RETURNS relative time goes faster and that when the rocket goes AWAY relative time goes slower. It is the same thing as the sound frequency of a passing train with EXACTLY the same formula, Though everybody thinks it must be something different.

[@moiquiregardevideo]

That is exactly how I resolve the twin paradox ; as electrical engineer, think about the Dopler shift of back/forth radio transmission. All the slow time when the rocket was flying away from earth is catching up when the rocket makes the U turn and the two twin meet again with not age difference... except the cell damage from drinking your own piss filtered with something.

[@twirlipofthemists3201]

@@moiquiregardevideo You misunderstand the physics. Take Don's advice and apply the Lorentz equation. One twin really does experience more years than the other, and truly is years older - his diary has more days in it - when his brother returns. Your model isn't all wrong, though. It's almost right for how the two twins SEE each other. But it's not right for how local time passes for each. What you're missing is the space dilation that goes along with time dilation. The fast twin sees himself travel a shorter distance than his stationary brother sees him travel. (That effects everything.) And they're both correct. And a third twin (triplets now) moving at a third speed would disagree with both his brothers, and he would be right too. Not just velocity, but also position. Stationary brothers at different places will measure everything their relative way (non-simulataneity), and no one is ever wrong.

[@thegustavodag]

7:14 Why does he always skip the part where positions are relative?

[@chrisofnottingham]

I actually understood this already but I found the presentation very difficult to follow. As far as I'm concerned the key points are that from symmetry, each relatively moving inertial observer "deduces classically" that the other has a slow clock and a short ruler. And the solution to how this can be is that they can never compare clock or ruler directly because they can only be at the same place at the same time once. To meet again, one of them must go non-inertial, and that breaks the symmetry. I also like the childish analogy that two distant observers each think the other looks very tiny.

[@felipelopes3171]

Hi Dr. Lincoln, wouldn't it be better to use spacetime diagrams? The way I understand this is: if you want to compare clocks at two different points in space, you need to specify a frame that will give you the orientation of the time axis in the spacetime diagram, and this axis is changed by a Lorentz boost. This way you can see the ambiguity in a very clear geometric way.

[@kingmiura8138]

Thanks Don for causing more confusion and adding complexity. Why not simply state that anyone who travels near the speed of light for a significant time period will return to an earth that has clearly aged faster than the person who traveled near the speed of light?

[@john2001plus]

I wondered about the paradox for 40 years. I tried to ask my Physics professor about it, but never got an answer that I was satisfied with. I still don't understand it.

[@IndicDarshan]

u are not alone. Actually this guy has played a trick only. And actually what has he proved is that if a clock is moving opposite direction as the observer 2' clock (which is moving to the left w.r. to observer 1)) is seen faster rather been dilated. Anvd it's a weird conclusion this prof seems to have reached at. : - D. Einstein was clever to avoid such paradoxes,

[@riraldi]

@@IndicDarshan The key is: if your clock in your hand compares with clocks that are ticking in front of you, then it seems that the clocks in front of you are going faster. but if with synchronized clocks you see a particular clock that moves and goes from one clock to the next etc, then that clock goes slower.

[@IndicDarshan]

​@@riraldi It is interesting you brought up the phrase 'seems to be' or 'appears to be' making SR some kind of illusion, However, one of the guys in motion w.r.t each other has to age actually slower or faster or equally w.r.to the other. As this Prof in video does not bring any history of acceleration then it's a symmetric problem. Whatever one guys sees for other's clock the other guy must see the same for the first one's clock. For example if one sees the oner's clock going slower then the other must see the same for the clock of the first one unless one uses the direction of motion top resolve or distinguish the two cases or break the symmetry because both guys can not age slower or faster w.r.to each other IR in other words both clocks can not go slower or faster w.r.to each other unless it's an illusion or time is illusory. My blame here is this prof is using the direction of motion of the clocks or of the two observer to break this fundamental symmetry (and hence the paradox) of SR. Most of the professors use history of acceleration to resolve this paradox but this prof is trying to do the same without invoking any acceleration.

[@IndicDarshan]

Now coming to your explanation is also just avoiding the paradox by bringing in one more scenarios of what seems to appear with individual clock in front and the series of clocks synched in the other frame. Does it resolve the fundamental symmetry or the paradox? Nope because whatever the one of the observer seems to see about the other's clocks (both with clock in front of and w.r. to the series of synched clocks in the other frame) has to be symmetrically true vice versa for other observer about the clocks of the first one. Unless either you invoke the history acceleration or the direction of motion.

[@IndicDarshan]

@@riraldi SO, as the prof in video resorted to the direction of motion to resolve this symmetric case of SR without or in absence of invoking the history of acceleration, You with your explanation will also need the same if at you seem to have broken the symmetry, like indeed only one guy will age faster than the other. If you do not claim to have resolved this symmetry i.e whatever one observer sees fo the clocks of one frame the other observer will also sees for the clocks of the first frame then we both are on the same page w.r.to breaking the symmetry. Provide that you are unnecessarily doing two type of comparison for each observer : one with the clock in front and the other withe series of clocks encountered. I have no objection with bringing two types assessment for each observer. My objection is that the same has to seen or seems to have been seen by other observer w.r.to the earlier one.

[@amirhesamnoroozi3741]

The main problem with this video for me is that how to interpret the following statement: "How observer 2 sees what observer 1 sees at observer 2's location."

[@manthansingh8036]

Same problem here

[@xiaoxiao-kg5np]

@@manthansingh8036 and analyzing some Observers SUBJECTIVE view point of some remote event is NOT doing Physics. Physics is OBJECTIVE, not experiential, and subjective. Two real Physicists doing any experiment MUST always make sure that BOTH observers use the same standards, same have pre agreed origins and synchronized timing etc. All this talk about who is moving should never enter into any actual experiment in Physics.

[@JohannBaritono]

@@xiaoxiao-kg5np Does the word "relativity" ring a bell? Observations will always depend of your frame of reference .

[@xiaoxiao-kg5np]

@@JohannBaritono Subjective Observations might depend on your physical conditions, but the actual motions of physical objects do not depend on who is watching from what location and what HIS own motion may be. "Frames of Reference" are 100% imaginary, and play NO PART at all in the actions of physical systems.

[@JohannBaritono]

​@@xiaoxiao-kg5np Just as seeing a 6 or a 9 depends on your position, the same is true for physical phenomena. One easy example: The strength of a magnetic field will depend on your distance (or the distance of your frame of reference) with respect to the field. Seeing an object in motion or at rest, will totally depend on your movement with respect to the object. And to make it even more complicated, if we use quantum mechanics, the existence or not of an entity or phenomenon, will totally depend on the observer, not the entity itself.

[@yankeedoodle8749]

At the end you say they both agree that the remote person's clock is slower. Isn't that exactly the paradox you were trying to clear up? Both their clocks can't be slower (or faster) than the other. One has to be faster and one has to be slower.

[@new-knowledge8040]

I find that knowing exactly what is occurring, and thus excluding any math assistance, makes it a heck of a lot easier to understand. Once understood, you can derive all of the SR mathematical equations, along with the Lorentz Transformation equations, and do so even if you have never ever seen them before.

[@RandomPerson-yq1qk]

@@RIPxBlackHawk It has nothing to do with you seeing something in the literal sense. The two postualtes are simply put that a) all refrence frames are equal and b) speed of light is the same in all refernce frames Given just some very minor assumtions you can conclude the Lorentz transforms because of Maxwells euations for electromagnetism. Once you have the Lorentz transform time dilation is a necessity. The thing about how you see clocks came either from somone who didnt really understand relativity, a bad phrasing, or somone who wanted to explain it in a more easy to digest as an analogy.

[@RandomPerson-yq1qk]

Actually I think that you dont need Maxwells equations once you have postulated that speed of light is absolute. The absoluteness of c that comes from electromagnetism is a key point in relativity.

[@frankdimeglio8216]

@@RandomPerson-yq1qk Generally relativity is political in accordance with maximum money making agenda “physics”. Galaxies disprove Einstein. Gravity is ELECTROMAGNETISM/energy. Here is the proof. WHY IT IS IMPOSSIBLE TO SEPARATE inertia/INERTIAL RESISTANCE, gravity, AND ELECTROMAGNETISM/energy, AS ELECTROMAGNETISM/energy is gravity; AS E=MC2 IS clearly F=MA IN BALANCE: Gravity is not fully and accurately described or accounted for by the idea of “curved” “space”. Consider the man who IS actually in what is outer “space”. Think about TIME. Consider what is THE MAN who IS standing on what is THE EARTH/ground. E=MC2 is CLEARLY proven to be F=ma ON BALANCE, as ELECTROMAGNETISM/energy is gravity. Gravity is ELECTROMAGNETISM/energy. TIME dilation ULTIMATELY proves (ON BALANCE) that E=MC2 is CLEARLY F=ma ON BALANCE, as gravity AND ELECTROMAGNETISM/energy are linked AND BALANCED opposites; as gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE; as ELECTROMAGNETISM/energy is gravity; as GRAVITATIONAL force/ENERGY IS proportional to (or BALANCED with/as) what is inertia/INERTIAL RESISTANCE. “Mass”/ENERGY involves BALANCED inertia/INERTIAL RESISTANCE consistent with/as what is BALANCED electromagnetic/gravitational force/ENERGY, as E=MC2 is CLEARLY proven to be F=ma ON BALANCE; as ELECTROMAGNETISM/energy is gravity. This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual IN BALANCE. BALANCED inertia/INERTIAL RESISTANCE is fundamental. Energy has/involves GRAVITY, AND ENERGY has/involves inertia/INERTIAL RESISTANCE. Carefully consider what is THE SUN. Think about TIME. Consider what is the speed of light (c). The stars AND PLANETS are POINTS in the night sky. It all CLEARLY makes perfect sense. BALANCE AND completeness go hand in hand. Gravity is ELECTROMAGNETISM/energy ON BALANCE. By Frank DiMeglio ABSOLUTE MATHEMATICAL PROOF THAT ELECTROMAGNETISM/energy is gravity, AS E=MC2 IS clearly F=MA ON BALANCE: The balance of being and experience is essential. THE SELF represents, FORMS, and experiences a COMPREHENSIVE approximation of experience in general by combining conscious and unconscious experience. GREAT !!! Think. ELECTROMAGNETISM/energy is gravity, as gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE; as E=mc2 is F=ma. Accordingly, the rotation of what is the Moon matches it's revolution. GRAVITATIONAL force/ENERGY is proportional to (or BALANCED with/as) inertia/INERTIAL RESISTANCE, as gravity AND ELECTROMAGNETISM/energy are linked AND BALANCED opposites; as E=mc2 is F=ma ON BALANCE. Carefully consider what is the speed of light (c). The stars AND PLANETS are POINTS in the night sky. Accordingly, ON BALANCE, the PLANETS will move away very, very, very slightly in relation to what is the Sun. THE EARTH/ground AND what is the Sun are CLEARLY linked AND BALANCED opposites, as E=mc2 is F=ma !!! “Mass”/ENERGY IS GRAVITY. ELECTROMAGNETISM/energy is gravity. BALANCED inertia/INERTIAL RESISTANCE is fundamental. Energy has/involves GRAVITY, AND ENERGY has/involves inertia/INERTIAL RESISTANCE. THE EARTH is blue, AND the sky is ALSO BLUE ON BALANCE. Gravity is CLEARLY proven to be ELECTROMAGNETISM/energy on balance. E=MC2 is CLEARLY proven to be F=ma ON BALANCE. This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual IN BALANCE, as ELECTROMAGNETISM/energy is gravity; as objects fall at the SAME RATE (neglecting air resistance, of course). Gravity is ELECTROMAGNETISM/energy. TIME dilation ULTIMATELY proves ON BALANCE that E=mc2 is F=ma, as ELECTROMAGNETISM/energy is gravity. INDEED, TIME is NECESSARILY possible/potential AND actual IN BALANCE; as E=mc2 is F=ma ON BALANCE; as ELECTROMAGNETISM/energy is gravity !!! It all CLEARLY makes perfect sense, AND BALANCE AND completeness go hand in hand. GREAT !!! By Frank DiMeglio

[@tapan6985]

@@RandomPerson-yq1qk Q

[@frankly5171]

I think you are presenting this in a more complicated manner than necessary.

[@gnyszbr4187]

If you say that v in - direction times t1=x, then you should say that the observer2 (t2) is seeing the first observer’s displacement as -x or you should have said -x at first. Hence, the first observer’s time dilation formula will also change and the problem will still remain. You can’t just play around with the equation and change the result somehow. Negative values doesn’t matter in common format since the v is squared.

[@gnyszbr4187]

@silverrahul lorentz transformation equation? Normally vector directions as - and + doesn’t matter because the vectorial variable is squared. And the mistake he made was that he changed t1=t2γ to t1γ=t2 by changing x with -vt1. But x isn’t a positive value here it should be -x=-vt1 because displacement also is vectorial and he defined left as -.

[@gnyszbr4187]

@silverrahul Honestly I don’t think this problem can be solved as long as relativity (not lorentz transformations and time dilation) is accepted to be true.

[@gnyszbr4187]

@silverrahul Which is the non squared variable in (1-v²/c²)^(-1/2)? Also again, he said that observer at top sees observer at below moving at -v. And then he multiplies -v and t1, gets x as displacement and changes with x in equation. In equation x and v is at the same direction, but in his explanation they are not mathematically since one is negative and one is positive. He should multiply -vt1 with -1 because -vt1 is actually equal to -x.

[@gnyszbr4187]

@silverrahul my conclusion is that he gave direction symbols wrong. I don’t know if it was on purpose or not but it definitely caused lorentz factor’s value to change and seemed like it’s solved.

[@gnyszbr4187]

@silverrahul “ _I dont think there is any unsolved problem here_ ” What do you think does break the symmetry in two inertial frames? Any solution that can show one experienced more time can be used for the other observer too. Even if I made a mistake on previous comments about direction thing (which may be but I don’t see any mistakes) this solution still can be applied for the observer at below and same results (longer time passed) for it.

[@davidwilkinson8431]

Love the Isaac Newton / Iron Maiden T-Shirt

[@jaybingham3711]

It might have been worthwhile to make use of Bob (T-bob'sPOV) and Alice (T-alice'sPOV) in lieu of Observer 1 and Observer 2. The audio load of processing and staying oriented with so many utterances of "Observer (x)" might be better accommodated via a bit of personalization. Minor point. It's still yummy. Keep 'em coming! Thanks.

[@chrisbohr9115]

I don't get the so called paradox here. In the beginning you said 'they can't both see other's clock being quicker than the other', but at the end you said both see each other moving slower. Why is this not a paradox?

[@otakurocklee]

You are making this way more complicated than it needs to be.

[@starrmusiclive]

They do that to intimidate and seem superior. All of science is much simpler than these guys make it.

[@T1000-s4j]

@@starrmusiclive Yeah that's why you have PhDs in mathematics and physics.

[@olasek7972]

Daniel Starr it is actually a lot harder, this is an introduction for ignoramuses

[@otakurocklee]

@@olasek7972 The concepts are hard. But the way he's explaining things in this video is more convoluted than it needs to be (mostly because of notation choices, not physics). Basically there are 2 concepts in special relativity. Time dilation, and relativity of simultaneity. It "seems" paradoxical that each observer sees the other observer's clock ticking more slowly when you look at time dilation alone. But the paradox disappears when you understand that two events that are simultaneous in one frame, aren't simultaneous in the other frame.

[@realitynowassigned]

"lets make this simple" Shows masters levels physics for 5 minutes "So now you see how simple that is. But we're not done yet"

[@jezz439]

Dont mean to bash your jokes but Im here cause Im a first year physics student and we are rambling through these things right now :D

[@realitynowassigned]

@@jezz439 advanced math? Honestly i always felt there was a disconnect with the simple math. Understanding the theory without the math is profound in itself. Understanding the math seems to trivialize what you're mathemetizing

[@chuckgreygoodman4478]

I watch Dr Lincolns videos over and over

[@rocren6246]

I don't think this is going to convince many people without explaining how "the Lorentz Transformation equations" comes to be.

[@RodneyD]

Roc Ren Exactly

[@davidhunter6766]

Pulled it out of their ass! Thats how they happened!

[@Dislob]

I hate these types of videos that try to popularize complexe concepts by using math. The ONE THIING I dont find intuitive in life is math. PLEASE use different exemples. Like you have to start where everyone can understand. You have to describe relativity but making comparisons to Newtonian physics because that is more what our intuition is like. It's a slow process. Its not gonna "click" like eureka!

[@guilhermefurquim8179]

@@Dislob Then it will be easy to understand, but wrong. There's no way to understand it without maths.

[@donkeyhole2782]

I think I got older watching this relative to someone who didn't watch it.

[@fondueeundof3351]

"Tmoving is the time experienced by someone who sees the clock moving, Tstationary is someone who doesn't see the clock moving." I think already with this sentence you lose a large number of viewers. Tmoving is a) not the time *experienced* and b) in any case not by just anybody who sees the clock moving. Tmoving is the time *observed* on the moving clock by the stationary guy, and Tstationary is the time *observed* on the stationary clock by the same stationary guy. It is unfortunately very common in this context to use the verb "to experience", which should be avoided, it is only about observation, not about experience. The experiences of time for the moving guy as well as the stationary guy are exactly the same: for both time passes at the same speed as ever, neither of them experiences time passing in slow motion or fast forward.

[@sakuranooka]

@silverrahul Of course there is no physical experiment that would allow us to say who's stationary and who isn't, even the question itself makes no sense. However, you can pick randomly either of the two and say this is the stationary guy *by definition*. Ultimately, it might be even less confusing to just name the two guys Alice and Bob. That being said, it's irrelevant with respect to my more linguistic/didactical statement.

[@fondueeundof3351]

@silverrahul Here, as long as both the "stationary" and the "moving" guy sit in inertial reference frames, these words are just labels. You could as well label them the "green" and the "red" guy or whatever, it makes no difference to my statement, which is that neither of them "experiences" a time slow-down.

[@ericpilkington6298]

The most interesting about this video is that it actually never explained the paradoxical outcome of the simple twin age scenario by using the twin age scenario :D 3:45 You obviously still have the problem with different ages of the twins when they both observe exactly the same thing happening.

[@octavohombre2]

He explained the twin paradox in another video.

[@ericpilkington6298]

@@octavohombre2 I have checked. Its not explained.

[@SimonClarkstone]

I hoped that that big row of clocks would be seen from the other observer's point of view, showing them squashed and *desynchronized*.

[@noorhashmi2009]

Have you come across any explanation video on youtube where *desynchronization* of clocks in moving frame of reference is discussed ? If not, I think this is a treasure of knowledge hidden in plain sight.

[@JohannBaritono]

I would probably be mistaken, but I think that the equation on 7'19'' should be X(2) = -V(1) . T(1), as we are measuring Observer's 2 position from the perspective of number one.

[@tuoratoo]

After watching this attempt at 'explanation' going back to Einstein was a relief.

[@samuelmcdonagh1590]

It was a good explanation you’re just a stupid kid

[@worldaviation4k]

The problem i found watching other's videos was they never say if it's the physical graviational pull on the clock parts that makes it harder for the hand to move, making it tick slower. No-one cleared that up for me. Like if i fall with a rain drop i can say the rain has frozen if i'm at the same speed

[@worldaviation4k]

@ritemoelaw_books83 is it like say rain just stopped because the wind is blowing it back. An observer would see like the rain has paused in time but really time hasn't even changed at all? This is the type of stuff that made me not want to fly because I didn't want to go back in time out of touch with family.

[@worldaviation4k]

@ritemoelaw_books83 it confuses me but I don't think we travel into the past 😊

[@HG-us6qc]

ritemoelaw_books83 then this doesnt have to do with time slowing down its entirely persepctive (what we see). Like how bodies underwater appear warped to us but it doesnt mean the body is actually deformed. Its just refraction. With the black hole thing its just the light being manipulated that affects what we see, not actual time slowing. Time is absolute

[@multimalware5325]

@@HG-us6qc thats different that is light being warped time dilation is not a warping of time its just the your relative velocity changing your prospective of time from what i understand you can't change time in any way all you can do it male time "feel" faster or slower

[@Dislob]

@@samuelscalise9686 This is a quote from the channel PBS space time on KZbin: "You should watch as many videos about special relativity as you can no matter whos made them. This is for your benefit, to prime your brain. This stuff is unintuitive so every little bit of osmosis helps." It doesn't make sense at first but you still understand some things. Each time you hear about relativity or read about relativity, it should consolidate your bases. I recommend you start with this video : archive.org/details/frames_of_reference (its on the website archive dot org. Look up frame of reference)

[@richardlinsley-hood7149]

My latest table which I think deals with all the questions For speed of light = 10 units/second, Actual velocity = 1.0 Apparent velocity = 1.111 At time points : 0,1,2,3,4,5,6,7,8,9,10 seconds Actual distance: 10.0, 9.0, 8.0, 7.0, 6.0, 5.0, 4.0, 3.0 ,2.0, 1.0, 0.0 units Apparent distance: ???, 10.0, 8.888, 7.777, 6.666, 5.555, 4.444, 3.333, 2.222, 1.111, 0.0 units Apparent velocity = 1.111 unit/second Actual velocity =1.0 unit/second For speed of light = 10 units/second, Actual velocity = 2 Apparent velocity = 2.5 At time points : 0,1,2,3,4,5 seconds Actual distance: 10.0, 8.0, 6.0, 4.0, 2.0, 0.0 units Apparent distance: ???, 10.0, 7.5, 5.0, 2.5, 0.0 units Actual velocity = 2.5 unit/second Apparent velocity = 2.0 unit/second For speed of light = 10 units/second, Actual velocity = 5 Apparent velocity = 10 At time points : 0,1,2 seconds Actual distance: 10.0, 5.0, 0.0 units Apparent distance: ???, 10.0, 0.0 units Actual velocity = 5.0 unit/second Apparent velocity = 10 unit/second For speed of light = 10 units/second, Actual velocity = 8 Apparent velocity = 40 At time points : 0, 0.5, 1 seconds Actual distance: 8.0, 4.0, 0.0 units Apparent distance: ???, 20.0, 0.0 units Actual velocity = 8.0 unit/second Apparent velocity = 40.0 unit/second For speed of light = 10 units/second, Actual velocity = 9 Apparent velocity = 90 At time points : 0, 0.5, 1 seconds Actual distance: 9.0, 4.5, 0.0 units Apparent distance: ???, 45.0, 0.0 units Actual velocity = 9.0 unit/second Apparent velocity = 90.0 unit/second For speed of light = 10 units/second, Actual velocity = 9.5 Apparent velocity = 190 At time points : 0, 0.5, 1 seconds Actual distance: 9.5, 4.75, 0.0 units Apparent distance: ???, 95.0, 0.0 units Actual velocity = 9.5 unit/second Apparent velocity = 190.0 unit/second For speed of light = 10 units/second, Actual velocity = 9.9 Apparent velocity = 990 At time points : 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 seconds Actual distance: 9.9, 8.91, 7.92, 6.93, 4.95, 3.96, 2.97, 1.98, 0.99,0.0 units Apparent distance: ???, ???, ???, ???, ???, ???, ???, ???, ???, 99.0, 0.0 units Actual velocity = 9.9 unit/second Apparent velocity = 990.0 unit/second ??? Means an entry for which there can be no reading. N.B the 1st result in all the Apparent distance lines will be ??? as the light has not yet reached the observer. Once velocities get very high, the point at which that occurs moves closer and closer to the observer.

[@thomasthompson5613]

God dang it, I do not understand a single thing about this video, but I loved it

[@itsReallyLou]

I appreciate your very nice presentation. I would also like to believe that with even more effort, the concept(s) could be conveyed with even less math, and ultimately with no math.

[@corwin-7365]

It can.

[@sadderwhiskeymann]

AMEN!

[@tylerdurden3722]

The maths behind the basic idea is actually simple. The simplicity is beautiful. A beauty that can only be expressed in one language. Math. Using words and analogies turns something beautifully simple into a complicated, confusing mess.

[@hosh1313]

I have 2 clocks together and synced. I move them apart in a completely mirror image of each other and then bring them to rest at a distance, again, in a mirror image way. i.e. all accelerations, decelerations and constant velocities happen at exactly the same time and for the same duration in opposite directions. Relativity says one must be slower and the other advanced - but which one is which? From the frame of reference of the starting point, both dilated identically and are thus still perfectly synced? From the frame of reference of either clock however, the other clock is slower? Hmmmm................

[@TheApostleofRock]

This is beautiful. Thank you. I finally have some knowledge of these Lorentz transforms I've heard about. Pretty much everything in this video was new.

[@Earthspirit1147]

"Maybe!!!" he sez. Maybe, I'll have to run the video over again... MAYBE!!! He sez... LOL

[@badlydrawnturtle8484]

You didn't actually address the paradox, though. "Observer 2 sees more time elapsed than Observer 1 sees at Observer 1's location, but sees less time elapsed than Observer 1 sees at Observer 2's location." is just a restatement of the paradox in slightly more rigorous terms. Each observer sees time ticking faster for the other observer's location than for their own, which still doesn't make sense. I'm sure there's a way to address this paradox, but this video isn't it.

[@badlydrawnturtle8484]

@silverrahul From the perspective of the space twin's inertial frame, the Earth twin moves away and back, and hence the Earth twin's clock ticks slower and hence the Earth twin is younger when they reunite. Paradox.

[@badlydrawnturtle8484]

@silverrahul "The space twin's frame is NOT inertial" It is for most of the journey. The paradox originally under discussion in the video makes this clear by not having any acceleration involved at all. One person is moving, one person isn't. Both are inertial frames.

[@badlydrawnturtle8484]

@silverrahul "not true. The standard twin paradox orginally under discussion DOES have acceleration involved during the turnaround." Did you watch the video? This isn't about the twin paradox. Try addressing the paradox presented in the video.

[@badlydrawnturtle8484]

@silverrahul "well then dont talk about the twin paradox then." You're the one who brought it up. And yes, in the video, there's a paradox. I know. That's my entire point for commenting.

[@badlydrawnturtle8484]

@silverrahul So you have no solution the paradox in the video. It's actually a paradox, and relativity is thereby falsified?

[@Twobarpsi]

If this guy were my teacher in high school, I would have been a genius!

[@Mnemonic-X]

No. You would have been more stupid than a child.

[@smokey04200420]

Now we’re gonna look at how observer 1 sees the clocks ***Does a bunch of math but doesn’t show what the clocks read for observer 1***

[@NiteshPrasad91]

This is my new favourite science channel

[@GrantZPrice]

the reason there's a paradox is due to our limited understanding of linear time confined to our dimensional perspective. IF we stop thinking of time as a universal constant, we stop having this problem.

[@relativityman6196]

now that you understand linear time can you answer questions in this clip? //kzbin.info/www/bejne/joHNYmeQr5ajbbs

[@yingyang1008]

Lol, but time doesn't even exist - how the hell can it dilate?

[@bernieflanders8822]

General and special relativity are actually quite easy to understand once you get your heads around it. Just wait till you try to get your head around quantum mechanics and string theory. The problem is, most people don't get it straight away so they ignore it and latch on to some conspiracy theories that "explain reality" easier albeit complete and utter fiction. I wish conspiracy theorists would immerse themselves into actual reality as I pity the fact they are wasting their lives by believing in a story invented in a youtubers basement that " debunks" all our hard work and experiments yet they have no experiments to prove their "theory" on reality. It's a shame.

[@dimitri1515]

I'm not sure if this is the right video but acceleration does play a key in determining how to apply gamma. Without this, you could never truly determine who has a velocity > 0

[@tonreuvekamp2515]

This derivation proves that the time passes slower at observer 2 compared to observer 1. But since all movements are relative we could swap the two observers and asume observer 1 is moving. Aplying the same derivation as before now all of a sudden time passes slower at observer1. So the paradox still remains.

[@tonreuvekamp2515]

@Håkon The twin paradox cannot be solved using special relativity. We have to use general relativity, because acceleration is involved. See other youtube videos on this subject.

[@tomcass240]

Absolutely no intuitive understanding can be gained from this video, whatsover he literally just regurgitated the equations and said "there is no paradox because lorentz transformations equations say there aren't". Makes me think the narrator doesn't really understand anything outside of the maths, in which case he shouldn't be trying to teach physics. I've seen far more elegant explanations than this that don't just dive straight into equations that only people with an advanced maths education are going to properly understand.

[@jeromehattkronen2305]

Also he's saying a number of times that according to the LorentzTransform the moving clock must tick faster thn the stationary. Suggests the entire video may actually be intended to cause confusion rather than to clear it up.

[@santanudutta2555]

I wonder if time dilation can be explained in the following way, based on simple classical Physics. Imagine a clock comprising an binary counter with two, states: 1 and 0. Every second, the counter changes state. Both Jack and Jill have one of these clocks. The clocks are synchronized when the are together on the Earth. Then Jack gets on a space ship and travels away at a speed of v. He sends Jill a radio signal upon each clock transition. Let’s take the case of one such transition: Jack’s clock going from 0 to 1 at time T_Earth. This is also when Jill’s clock goes from 0 to 1 as the two clocks are synchronized. However, Jill sees Jack’s clock transition T1 s later than her own, where T1 = D1/(c) where c is the speed of the radio wave (same as light) and D1 is Jack’s distance from Jill at the time the transition occurred. 1 s later according to Jack’s time, his clock goes from 1 to 0 and he sends another radio signal to Jill. However, relative to her time, Jill will receive the second signal at (1+T1+delta), where delta = v/c is the time dilation. It is the time required by the radio signal to cover the additional distance, v, that the signal has to travel as Jack is now at a distance of D1+v from Jill. Is this correct?

[@mayhem8166]

I dunno, I was pretty ok with the whole relativity thing before I watched this video but I'm more confused by the t sub1 being the gamma of the t sub 2.... it may well be right, but to me this explanation is as clear as mud. Sorry.

[@bpo1975]

mayhem8166 What, you mean you don't have a PhD in Physics?

[@MarkDavis77]

I believe the key is at 9:31. Basically (and I could be effing this up, it's been a while) consider a person traveling at the speed of light to Alpha Centauri. That will be observer 1. Observer 2 is the person watching Observer 1 travel to Alpha Centauri. If it takes 1 light year to travel to AC, Observer 1, from their perspective, will travel to AC FASTER in his POV than that 1 year. This is what he means when he says "observer 2 sees more time elapsed at observer 1's position than observer 1 sees" - Observer 2 would see, from observer 2's position, the ENTIRE year elapse before observer 1 gets to AC, but observer 1 would see LESS than that 1 year. However, that 1 year is still LESS time than Observer 1 would see elapsing at observer 2's position during Observer 1's travel to AC - this is the second part where he says O2 would still see less time at O1 than O1 would see at O2 (eg. O2's 1 year would be less time than O1 would see if they looked back at O2 while on the way to AC). The second part is when the equations would probably be needed to figure out exactly the amount of time. Then again, this could be totally incorrect.

[@twirlipofthemists3201]

It's hard to follow, made harder by the choice of terminology, which all sounds alike. It's been a while, but I used to do these equations for sort-of fun / curiosity, and so I think I probably(?) know what he's explaining, and I'm even more sure Dr. Don is probably right, but I still couldn't follow it. Word soup. It's unintuitive stuff. You need to do the math yourself and/or need really good diagrams and examples.

[@MrJonsonville5]

@@MarkDavis77 a light year is a measure of distance, not time.

[@MarkDavis77]

@@MrJonsonville5 you misunderstood me...

[@TheWarmupLap]

I think my brain just peed itself

[@rickpontificates3406]

It will never cease to amaze me that time, this thing we cannot touch or see, is affected by gravity and velocity. The fact that warping spacetime changes the relativistic passage of time makes me wonder how “dark matter” might be connected to time and spacetime.

[@blinzy7282]

Did he just say at 10:07 in the video that "both observers agree that the remote person's clock is slower"? I don't see a clear explanation of what is going on here. It's sad when smart people aren't very good at explaining things. This may just be a trick by Fermilab to get us to keep re-watching their video, lol. He had my hopes up that there would finally be a good explanation for this apparent paradox, but instead I feel more confused. So is time actually moving slower for both observers in respect to the other being observed, but it is just an illusion of causality shifting in the direction of travel? For instance this is in the example where lightening hits the front and back of the train, the guy on the train sees the lightning his the front first if he is half way between both events and the observer watching the train sees both happen at the same time. This can also be reversed so that the guy on the train see 2 simultaneous events happen in front and behind a non moving observer on the ground, but the guy on the ground would have seen them happen at different times.

[@Scolecite]

I want this background so I can say anything technical and people will believe me.

[@oldjoec3710]

Hard to conceive of a more confusing way to state the frames of reference. You say t moving is the time experienced by the person who sees the clock moving, who is however really the person standing still. So t moving is definitely NOT the time experienced by the person who is moving. After that, I'm so lost that everything else loses meaning.

[@richardturietta9455]

Great video, I will re-watch several times, I think to nail home the concepts for myself. I love relativity, and my physics degree helps, but, as you say, there are subtleties!

[@vijinv5279]

Fermi lab: Relativity Me:Man I can't wait to see the comment section

[@rasraster]

Final complaint: why do you use x1, t1 in a way that is not referring to the position and time of Observer 1? You use it, for example, for how Observer 1 sees his own t and x, AND for how Observer 1 sees Observer 2's t and x. I think you are using the subscript 1 to just indicate some definite data point that gets taken, but that's super confusing.

[@harryr.6744]

Relativity double talk confusion at its best. Gets award for best obfuscation of science ever.

[@timearly5226]

So, we're having teas at 1. I'll be a bit late (in your reference frame)

[@RichardWilkin]

Noted: Early will be late.

[@timearly5226]

@@RichardWilkin Of course! It would be redundant if Tim Early arrived early.

[@TeodorAngelov]

Kudos for the spirits. I haven't studied relativity in university so I don't know the people that get time dilation wrong in this way. The scope of this video was much smaller than I expected. The twin paradox was only mentioned and not resolved. I also found the description much more confusing than it has to be.

[@blib3786]

I've never understood why the "Twin Paradox" is referred to as such. There isn't anything paradoxical about it.

[@oscargr_]

Xeyn W. It's named a paradox, but paradoxically it isn't one?

[@Gringohuevon]

No..each observer sees the other clock running slower..there is no paradox. Each clock has its proper time in the reference frame of each observer

[@corwin-7365]

Indeed. :-)

[@michaelstark2832]

...each observer 'sees'... Aye,there's the rub.

[@adrianoaxel1196]

Congratulations on the initiative of the videos and, of course, the choice of T-shirts in many of the videos! :)

[@yuyurtrtrt2160]

pbs spacetime is simpler but less in depth if anyone is confused.

[@robertfletcher3421]

I'm confused

[@trewq398]

simpler but less in depth?

[@Zebimicion]

PBS Spacetime focuses too much on equations and less on the applications of them in the real world. And that's fine for the initiated, but they forget the majority of the viewers don't have a degree in math or physics so their channel is becoming more and more dull.

[@vampyricon7026]

PBS Spacetime is more for people who are prepared to work hard to understand the theories. They are for people who want a more in-depth view of QFT and GR without being forced to work without math.

[@GulfsideMinistries]

Agreed. I have a much easier time (I think! I could be more lost than I realize ;)) with Fermilab than Spacetime.

[@cenaloh4714]

🤯and 😵 rewatch after my brain calm down

[@cptechno]

This presentation and others by Dr. Don Lincoln says something that was never clearly articulated before: 1) Time is already progressing at its maximum speed that is C. It can only be slowed down because it's at it maximum. 2) Just like there is a maximum speed in our space-time universe, time has its maximum rate of progressing and again it's C.

[@AureliusL]

Nice "Iron Maiden" Shirt ;)

[@mastertek383]

I learned about time dilation from "Interstellar"

[@aboriginalunderground4958]

Nubbins That’s what made me look up the theory of relativity.

[@mastertek383]

@TheWeeaboo Yeah I know Mathew Mahogany would have been stretched out and mashed like fly guts but just lemme have my sci-fi . My good sci-fi films and my kitty cats is about all I have left

[@aboriginalunderground4958]

No one knows anything about black holes. They’re totally made up. When a human beings from planet earth can actually go to one, go inside and witness it, then return to earth with proof of the discovery besides just math equations or studying the characteristics of the space around them through a telescope, then there can be a true discussion. It’s all theory guys. Though I admit it is very entertaining.

[@sparkz015]

@@aboriginalunderground4958 we know black holes exist, but not completely whats in them

[@physicshacks6349]

@@mastertek383 I think you are talking about spaghettification in which a person perceives gravity more on head region than feet while passing through blackhole and which streches him apart . Also blackhole is more unstable than wormhole because black hole has more energy than wormhole. Yeah it just a sci-fi movie and not taking account of real science

[@donr7327]

Careful - most texts refer to the frame that sees the motion as stationary (e.g. the observer at the station) and the other as moving (e.g. the observer on the train). This video does the opposite. The “primed frame” is conventionally the moving rather than the stationary. So in the video the Lorentz equations are the reverse of what you’ll usually see. Most texts: t’ = gamma (t - v / c^2 x) (t’ is the moving frame) Here: t’ = gamma (t + v / c^2 x) (t’ is the frame that sees the moving)

[@davidburns1753]

Thought I was pretty smart ... now I feel really dumb ... thanks.

[@egwuekwechima4463]

Time dilation is a paradox in itself in that the more you try to understand it, the more you don't. In order not to confuse myself further, I've taken just the basic points and not stressing myself further. The points are: 1. Gravity is basically caused by how the mass of object bends and distorts the space around it. Thus, almost every object has a universal 'pull' or 'push' on other objects around it, no matter how infinitesimal. 2. It's almost like time is a construct that exists outside of space. It doesn't want to be where space is. Space and time are inversely dependent on each other. The more space you experience or pass through, the less time passes for you relative to someone at rest (who isn't moving through space). Vice versa is the case too. 3. Going back to point 1, this would mean that an object experiencing a large gravitational pull will be stretched out in space more than one experiencing lesser gravity. Thus, time will literally pass slower within that object. 4. Lastly, the way I see it is that, within the universe, exists an anti-universe. In that anti-universe, time is the physical seeable construct while space is 'abstract'. Dark matter is visible while matter and light isn't and this anti-universe inversely complements and exists mutually with our normal universe. Would love to see this from other people's perspective, so I can know where I'm wrong. Thanks for reading.

[@pigofapilot1]

Interesting and mostly I would agree but I would like to expand on point 2. Yes, even light takes time to get from point 'a' to point 'b' and time (t) is relative to velocity and space (distance) or (v=s/t). However, there is motion and also 'relative motion'. That is because in space there is no fixed reference point by which you can measure velocity. In other words, where two objects are moving relative to each other there is no way to determine which one (or even both) is actually moving. The only thing that you can be sure of is that there is relative motion between the two objects (unless acceleration is involved). This is different from two objects moving at the same relative velocity. It is this 'relative motion' that is relative to time(t) and which creates time dilation between two objects. This does not apply to two objects with the same constant velocity and no relative motion, which are considered to be 'at rest' with each other and do not experience time-dilation, except to a third object which does have a relative motion through space (and therefore time). I hope that helps.

[@prg54]

TOTALLY confusing naming the 2 observers as "moving" and "not moving".

[@olasek7972]

prg54 not confusing at all

[@prg54]

@@olasek7972 , I understand why naming the guys (" t moving" and "t stationary") according to how they see the 2 clocks but the Fermi lab guy could have used a simpler label for both, as several have suggested here, without losing sense.

[@justicegaminginc]

The reason one clock has a different tick speed than the other is because we measure time wrong, we still use some form of swinging object or particle depending on the clock which is a problem because swinging parts or bouncing particles become inaccurate when in motion such as being in orbit or traveling in space offsetting the tick speed. Until we can come up with a better solution to avoid time dilation which is only due to how we measure time the best thing to do would be to send a constant live feed to a ship or station of the exact time and date on earth with the lowest latency possible.