Derivation of Time Dilation in Special Relativity using a Light Clock | Doc Physics

We run into some pretty HUGE conceptual inconsistencies here. Get ready.

[@vince3139]

YO, you are one hell of a teacher.

[@DocSchuster]

Thank you, homey!

[@jenniferq5758]

or "ohmie" :)

[@gregorykarimian3813]

@@DocSchuster hahaha

[@voidisyinyangvoidisyinyang885]

@@DocSchuster Deal with it! zing....

[@frankdimeglio8216]

@@DocSchuster UNDERSTANDING TIME AND THE CLEAR MATHEMATICAL PROOF THAT E=MC2 IS F=MA ON BALANCE, AS ELECTROMAGNETISM/energy is gravity: ELECTROMAGNETISM/energy is gravity. The stars AND PLANETS are POINTS in the night sky. Gravity AND ELECTROMAGNETISM/energy are linked AND BALANCED opposites, AS ELECTROMAGNETISM/energy is gravity; AS “mass”/ENERGY IS GRAVITY; AS E=MC2 IS F=ma. Therefore, the planets will move away very, very, very slightly in BALANCED relation to what is THE SUN. (Also, carefully consider what is THE EARTH.) Great !!! This explains the cosmological redshift AND the “black hole(s)”. GRAVITATIONAL force/ENERGY IS proportional to (or BALANCED with/as) inertia/INERTIAL RESISTANCE, AS E=MC2 IS F=ma ON BALANCE; AS ELECTROMAGNETISM/energy is gravity. Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS E=MC2 IS F=ma ON BALANCE; AS ELECTROMAGNETISM/energy is gravity. Gravity IS ELECTROMAGNETISM/energy. “Mass"/ENERGY involves BALANCED inertia/INERTIAL RESISTANCE consistent with/as what is BALANCED electromagnetic/gravitational force/ENERGY, AS E=MC2 IS F=ma ON BALANCE; AS ELECTROMAGNETISM/energy is gravity. SO, the rotation of WHAT IS THE MOON matches it's revolution; AND objects fall at the SAME RATE (neglecting air resistance, of course) !!! Time dilation ULTIMATELY proves ON BALANCE that E=MC2 IS F=ma, AS ELECTROMAGNETISM/energy is gravity !!! It all CLEARLY makes perfect sense, AS BALANCE AND completeness go hand in hand. Balanced inertia/INERTIAL RESISTANCE is fundamental. Time is NECESSARILY possible/potential AND actual IN BALANCE, AS E=MC2 IS F=ma ON BALANCE; AS ELECTROMAGNETISM/energy is gravity !!! GREAT. Stellar clustering ALSO proves ON BALANCE that E=MC2 IS F=ma, AS ELECTROMAGNETISM/energy is gravity. By Frank DiMeglio

[@feelingzhakkaas]

The way explanation is done is marvelous. i have never come across more interesting and simple explanation. Hats off to you SIR.

[@jbradfield]

skwurr.

[@Chrisaaad]

Lmao!

[@voidisyinyangvoidisyinyang885]

"We Skwurred it." Hey now!!

[@aryansinha1181]

u are just too good!!! The concept of time dilation along with the effect of special relativity became really easy to understand with your help. The maths used made it great. love u r explanations!!

[@Codyyyyyyyyyy]

I don't think I've ever laughed so hard while learning about special relativity. Thanks for the video! It was very easy to understand.

[@DocSchuster]

I remember thinking that exact thing was a bit goofy the first time I saw this, too. Stay cool!

[@dillonberger4036]

16:50 "I said it, deal with it." It should be acceptable to use this interchangeably with QED.

[@KaanIsTooBased]

I feel like J-Roc is teaching me special relativity

[@hanzn6784]

Siiirrrrr speed of light nom sayin?

[@kinglarryIV]

oh geez, what's wrong with "squared". Why must you say squr???????

[@nityarajan9323]

this was incredibly fun to watch and now i am gonna make a smashing presentation

[@rogerahier4750]

The light not only takes longer, it's a lower frequency. The distance it travels is the same number of wavelengths in both cases, that can't change.

[@Ihazmuffiin]

Thank you. This was really clear and fun to listen to.

[@DocSchuster]

But you're forgetting that the outside observer thinks the light clock is moving to the right. That's why the light will have horizontal AND vertical velocity components as seen by our outside observer. How cool are you with vectors?

[@DocSchuster]

Gamma is the same for any angle between v and d, but THIS derivation only gives us a solvable gamma if that angle is 90 degrees.

[@atan5091]

This is the best time dilation video on yt

[@galileogalilei1086]

Classical Physics and Special Relativity Theory (SRT) state that uniform velocity is purely relative. If there is a relative uniform motion between two clocks, each clock is "moving" with respect to the other clock, when it is viewed from the position of the other. Therefore, each clock should measure a shorter interval of time when viewed from the position of the other, according to SRT. This result is known as the Clock Paradox, and can be also expounded in this way: If there is a relative uniform motion between you and me, following straight opposite directions, I see that your clock ticks more slowly than mine (and thus you are ageing more slowly than me), but you see that my clock ticks more slowly than yours (and thus I am ageing more slowly than you). As a consequence of Special Relativity, a single clock should measure two different times at the same instant, just when the observers and their clocks are passing very close (and when simultaneity cannot be considered relative): 1) the time that I read in my own clock, and 2) the "slowed" time that you are reading in my clock. In the same way, each person should have two different ages at the same instant … It is obvious that a real clock cannot make this miracle. Only the imaginary "light clock" invented by Albert Einstein could make it, assuming that the speed of light is constant in every reference frame. However, if the light-speed in vacuum is relative to the frame of reference (like the speed of any other thing in the physic world), the light clock would work like a real clock, measuring the same time at the same instant for every observer … Louis Essen was a very reputed physicist (an expert in the measurement of time and light-speed) who invented the cesium atomic-clock in 1955. He lived until 1997 but he never believed in the relativity of time. He criticized the Einstein’s theory and the experiments made with atomic clocks in an attempt to prove it. See en.wikipedia.org/wiki/Louis_Essen

[@SuperMagnetizer]

Excellent post, completely agree.

[@emotionalvideos6897]

Definelty, Special Relativity has very little logic. It is an irony that Albert Einstein criticized Quantum Mechanincs, being him the one who formulated both SR and GR..

[@MysticMD]

thank you soo soooo soooooo sooooooooooo soooooooooooooooooo sooooooooooooooooooooooooooo much for not only helping me do well in my physics class, but better understanding the physical world!!! yay

[@DocSchuster]

Your ability to calculate gamma does not affect gamma. Gamma does not depend on angle. Your ability to calculate gamma depends on angle.

[@gersonwazhur]

can some one give this guy a medal !

[@rewind9581]

It’s as if Ryan Reynolds is teaching me special relativity

[@nexioseptimus5099]

When I took physics, I assumed the TAs teaching the class were mangling the words "square" and "square root" - pronounced as "skwurr" and "squirt", respectively - the same way there were mangling many of the other words... I don't think I had a native-English-speaking TA until I was a junior. I commented on this to another prof, and said no, the TAs learned to say the words that way from the native-English-speaking prof whose course they were teaching, it's a math and science culture thing, not a geographic culture thing. Only you can break the cycle. (I taught myself math, in between dropping out of high school and going to university. I'd never heard anyone speak some of the words I was reading, so I ended up with some bad habits like calling ln(x) "lan x" and saying soh/cah/toa for sin/cos/tan.)

[@jill7578]

Studying for my final! @12:20 is where I got it! thanks again!

[@tannibaby5834]

youre amazing i like your way of teaching youre paragon of physics teacher

[@DocSchuster]

Great question. Boy, I hope my students read this exchange. I think the stationary observer would say that the left light beam is going c left (having covered half a light-second in half a second), and the right beam is going c right (by same argument). Their error would be in supposing that the left light beam would see the right beam as going 2c. It would just be going c. I'll have a video on relativistic addition of velocities posted by Friday, and I'd love to have your thoughts on that.

[@Tonicwine999]

This is the best explanation with the maths I've watched. Brilliant.

[@aliengrey1708]

One slight problem, the light beam was not directed diagonally so it's following the hypotenuse of that triangle. It's traveling vertically at the speed of light and also horizontally at the speed of the rocket, if we accept the premise that a light beam moves with an object. If we don't accept that premise then it's actually not hitting the mirror in the center but back a little, and not bouncing directly back to the emitter, but twice as far back as it had been from the middle of the mirror. Neither of those scenarios involves the beam traveling a longer distance. It's like if you drop an object from a stationary position 9.8 metres above the floor and the same distance above the floor from something traveling at 9.8 m/s horizontally. It takes the same 9.8 s to reach the ground in both cases, not 9.8 in the first case and 9.8 x sqrt 2 s in the other. If that would actually happen don't you think somebody would have noticed sometime in the history of mankind and commented on it? Einstein just had a very flawed understanding of how two velocities in perpendicular directions work, neither is altered by the other's presence. I know it's shocking but nonetheless true. Not faulting the maker of the video, they just repeated flawed logic, presumably for entertainment purposes rather than science education purposes.

[@joepierson3859]

Think of light as a wave and not a particle and then you understand how the light clock works.

[@williamwalker39]

Relativity is an optical illusion. Time and Space are absolute as stated by Galilean Relativity. Hi my name is Dr. William Walker and I am a PhD physicist. I have been working in on this topic for 30 years. The speed of light is actually instantaneous in the nearfield, and after about 1 wavelength, it reduces the speed of light. This is predicted from Maxwell"s equations by analyzing the propagating fields generated by an oscillation dipole source. This applies not only to the phase speed and group speed, but also the information speed of the fields. This has been experimentally confirmed by transmitting radio waves between 2 dipole antennas and measuring the time delay as the antennas are moved from the nearfield to the farfield. Both the theoretical calculation and the experimental verification has been independently confirmed by many researchers over the past 30 years. In addition, gravity has been shown to have the same behavior. This has been proven theoretically by analyzing the the propagating fields generated by an oscillating mass using General Relativity. The instantaneous nearfield was confirmed by Simone Laplace in the late 1700's from the stability of the orbits of the planets in the gravitational nearfield of the sun. The farfield speed of gravity was just confirmed to be the farfield speed of light c by Ligo. Again, this speed applies to not only the phase speed and group speed, but also the information speed. Note that for the very low frequencies, the instantaneous nearfield can extend to astronomical distances. So everything is interacting instantaneously via both gravity and light. For more information: Search William Walker Superluminal Because Special Relativity is based on light being a constant, then the Relativistic consequences of this is that effects of Special Relativity on time and space are an optical illusion. Instantaneous nearfield light yields Galilean Relativity and farfield light yields Einstein Relativity. This is because in the nearfield, gamma=1since c= infinity, and in the farfield, gamma= the Relativistic gamma since c= farfield speed of light. Since time and space are real, they can not depend on the frequency of light used. This is because c=wavelength x frequency, and 1 wavelength=c/frequency defines the nearfield from the farfield. Consequently Relativity is an optical illusion. Objects moving near the speed of light appear to contract in length and time appears to slow down, but it is just what you see using farfield light. Using nearfield light you will see that the object has not contracted and time has not changed. For more information: Search William Walker Relativity Since General Relativity is based on Special Relativity, General Relativity must also be an optical illusion. Spacetime is flat and gravity must be a propagating field. Researchers have shown that in the weak field limit, which is what we observe, General Relativity reduces to Gravitoelectromagnitism, which shows gravity can be modeled as 4 Maxwell equations similar in form to those for electromagnetic fields, yielding Electric and Magnetic components of gravity. This theory explains all gravitational effects as well as the instantaneous nearfield and speed of light farfield propagating fields. So gravity is a propagating field that can finally be quantized enabling the unification of gravity and quantum mechanics.

[@nigelgibson623]

Brilliantly presented! Kiitos!

[@fundemort]

For those who are still confused about time dilation. Let's take the Superhero Flash as an easy example. Just like in the movies, when he uses his his ability and runs very fast, near the speed of light, there are two way to see it: ONE: We see from our normal humans perspective: We see him moving very fast, that we almost can't see his human shape and only his trails of lights. Maybe it's safe to say, according to our eyes, he becomes almost massless. It's almost as if he's turning into beam of lights. TWO: We see from Flash's perspective: When he is moving very fast, he sees us, his surrounding, and all of objects, to be almost stationary (or moving but very slow), hence according to him, we must be having a much slower timeframe (hence age much less). So there you go. Hope it gives an easy understanding to some people. SIDENOTE: In some episodes, Flash is told to be able to move faster than speed of light, hence he can travel through time (this part is just pure sci-fi).

[@mustafaezberbozan8150]

I have watched many videos about special relativity, and this is absolutely ever best.

[@hades3909]

I'm watching this in 2022 and I'm fascinated... I actually had thought about this and this guy (teacher) has explained it fabulously👍🏿. +- i saw him reply to other comments but it seems he doesn't know how to reply on the specific comment just wanted to say that... Yeah

[@davecharbonneau751]

Love this, Crayola should sponsor your videos man. Get that marker money!! I always understand physics from your videos. Thanks

[@new-knowledge8040]

Everybody tends to use the vertical light clock in their explanations, the easy clock explanation. But it's a good presentation here. It would also be nice to see 2 horizontal light clocks instead. We would see them with both being at rest, and then see them with one being in motion. We would then explain how it is that to the observers moving along with the mirrors, it seems to take the light the same amount of time to go from one mirror to the other mirror, no matter if the light is traveling in the forward direction, or in the reverse direction. For instance, if the distance between the horizontal mirrors was 300,000 km, and then the mirrors were accelerated to a velocity of 260,000 km/s, an external observer would notice that the distance between the mirrors would have now contracted to a distance of 150,000 km. He would also see that the light takes about 3.73 seconds to go from the rear mirror to the front mirror, and he would also observe that it takes about 0.268 seconds to go from the front mirror to the rear mirror. Yet to observers that move along with the mirrors, it would seem as though it takes the exact same amount of time for the light to go in either direction from mirror to mirror. An explanation of this would be nice to see.

[@crowxe]

please read my comment about the experiment in this video. the setting doesnt make sense (and so my mind cant accept the result). your suggested experiment setting seems good but the results is bad on comparing between both observers perception

[@new-knowledge8040]

Check my collection of mini KZbin KSP SPECIAL RELATIVITY videos. It shows how any Joe blow can discover special relativity on their own.

[@wildzach]

I'm puzzled by the last part. I knew that the observer on Earth would see the spaceship's time running slowly, but the fact that the spaceship sees Earth's clocks running slowly is giving me trouble. Which party will actually age more slowly?

[@lioelbammalf7483]

The problem is the "relativity" bit, given time is relative there is no "actual" time for someone to age more slowly. However this is only special relativity, fine for situations where your systems are moving at constant velocities but when you add acceleration or deceleration to move into another person's reference frame that is general relativity. Moving to someone else's reference frame *will* change things.

[@stuckinastairwell]

WhiskeyFox The solution to the problem has to do with relative simultaneity. If time moves at different rates, we stop agreeing upon which takes place at the same time. If you fly back from your space trip, you will change the inertial frame and reverse the order future events will be experienced.

[@gamecoolguy619]

Please explain this concept relative to the universe hence it's objective. As although this is true(considered to be so far) it is also taking into consideration a form of clock. Hence you're not actually talking about time but rather motion of light subjectively named to be time(not that I know of it either). If particles slow down on higher curvature making you sense things at a lot slower rate would give same result, Of course biggest problem that raises which I'm quite sure Einstein thought about when coming up with this would be speed of light can not be constant.

[@starreachsocietybw]

I am a foreign Student in Russia and you can imagine how boring it would be learning about Einstein’s theory of relativity in a foreign language...you literally shed so much light in me 😭😭😭❤️❤️❤️

[@crowxe]

you explained more simple and better than other videos i seen , but the inputs and conditions are questionable :- 1. how did the light beam in the ship gained horizontal speed? 2. if the light beam in the ship is aimed with an angle to meet the upper mirror after distance, then the whole equation collapse please help me presuming another example: 1. stationary observer at 300,000 km from earth 2. space ship heading towards earth at half the speed of light and passing beside the observer 3. as the space ship pass beside the observer, it opens the high beam towards the earth expected output A. the earth will be illuminated after 1 second B. the space ship pilot will see the reflection after 1.333 seconds C. the observer will see the reflection after 2 seconds if the example is relative then can you put a video with the classic example but with the space light clock vertical instead of horizontal ? (i'm learning so take it easy please)

[@karantejas8645]

What happens if the velocity of the space ship is not perpendicular to the clock?

[@DocSchuster]

Love it. I just tried it (no triangles - yay!), and found that the light on the spaceship appears (to an Earth observer) to go d + vt/2 on the first half of a tick and d + vt/2 - vt on the second half of a tick. I think it seems to go only 2d total in that case, which doesn't help us derive anything (unless you already believe in length contraction...). Can you help me see how you solved for t? Your second equal sign is not true. Did you mean to type an addition in one of the denominators?

[@brianstrigel2241]

the reason you didn't solve it is because you need the triangles lol addtiionally "d + vt/2 on the first half of a tick and d + vt/2 - vt " that is incorrect! when adding the same quantities together you get the right result, but it also fucks up the rest of your math for the derivation. d = vt is basic mechanics and is a function not something you can do to d - vt = 0 because time is always changing linearlly with respect to v. D always increases with an increase in time proportionally.

[@chemickykanalpanatitrmana2392]

Simply awesome man

[@danabjornson7057]

Love your work!

[@tomc3213]

You are fantastic!

[@gototcm]

The second you mentioned vectors, the light bulb turned on. Now I get it - thanks much

[@sachinrathi4334]

nailed it man simply awesome👌👌👌👌

[@dilrukshiperera900]

exxxcelent lecture, i thought relativity was like for you know grandpas or wise old men or something

[@shylildude]

"squore"

[@jeremymorain]

Listening to him say what he thinks square and square root are is torture. I die a little inside every time.

[@siddarthsairaj9513]

Video made by Jim carrey

[@alleneverhart4141]

nice, just one small quibble. 1/0 is not infinity. it's actually an undefined expression, otherwise there would have to exist a number which multiplied by zero that gives you 1. so the gamma for light is undefined - don't apply time dilation to light.

[@zhunter007]

Hrmmm, so I rotated my light clock horizontally and came up with t= d/(c-v) + d/(c-v) = 2dc/(c^2-v^2). What gives?

[@DocSchuster]

We've discussed that in the other comments on this video. Read on!

[@Science_of_physics]

Now I’m wondering to know time slower for which one really which one of these to guy get older slower ? Great explanation Mr. I like your explanation

[@anishgade4050]

You are an awesome guy.

[@jakesky100]

You explained it better than Leonard Susskind. THANK YOU! YAY! WOOOOOOOO

[@DocSchuster]

No. Please see my discussion with zhunter007. He asked the same question.

[@pepedecoatza]

mind Blown explanation man! congrats :D

[@nathanbolingo9]

THE GENERAL FORMULA TO GET THE HYPOTENUSE IS: C*C=A*A+B*B+2ABcos(angle between A and B) OR C*C=A*A+B*B-2ABcos(angle between A and B) ANYWAY EINSTEIN SET angle A and B =90 DEGREES SO THAT cos(angle between A and B)=ZERO

[@AbdallahHegab]

great work thank you

[@nathanbolingo9]

THE TWO DISTANCES WHERE THE LIGHT BEAM TRAVELS ARE DIFFERENT WHEN C=V THEN GAMMA=SQUARE ROOT(2)

[@DocSchuster]

That's the case when v = 0 (and pretty much the case when v is small). So, that just puts you in the non-relativistic domain.

[@MoeBdeir]

I am a bit confused with you stating that the resultant distance traveled by the light in the spaceship is equal to c * (t/2), but I find that the diagonal resultant of that distance should be a combination of c and v since they both exert a velocity on the light, therefor dont you think that the distance should be sqrt(v^2 +c^2) * (t/2) I am comparing this to as if you are pointing a gun upwards on a train and shooting. If the bullet leaves the gun at a speed c and the train is going at v then the overall resultant velocity to an outside observer will be sqrt(v^2 +c^2) and not just c!! Please let me know the reason, I am quiet intrigued

[@DocSchuster]

Moe Bdeir The speed of light is constant to all observers. This experimental fact sits at the basis of and necessitates relativity.

[@berkkonak]

Doc Schuster I had the same confusion, I don't get why speed is relative for a bullet but not for a light, but I will research this on my own. I also have another confusion. V is a relative speed according to the observer on the world, and it is calculated by dividing distance that the rocket traveled by t0 right? In that case, triangle side should be calculated as V*(t0)/2, but you used t in the equation. Can you please explain why you used t instead of t0? Thanks in advance.

[@DocSchuster]

***** Great question. v is also measured as the speed of the planet as seen from the spaceship. And t (as distinct from t_0) denotes the time that the planet's observers think occurs between ticks of the spaceship's clock. I believe it's the right variable to use there. The spaceship sees the space clock running at t_0, just as the planetaries see the planet's clock running.

[@MoeBdeir]

***** Yes, After a little search it turned out to be a rookie question... but what to do, everyone starts somewhere.. thanks

[@okmarshall]

Where did you learn how to say square/squared like that? Couldn't concentrate on stuff when that word came up multiple times.

[@DocSchuster]

You are making a simple mistake consistently. Please read and reflect on the following words, copied from my previous discussion: "The stationary observer would say that the left light beam is going c left (having covered half a light-second in half a second), and the right beam is going c right (by same argument). Their error would be in supposing that the left light beam would see the right beam as going 2c. It would just be going c." Gamma is NOT determined by a light clock parallel.

[@teodelfuego]

WTF with the three-year-old's pronunciation of "square?" Is this supposed to be cute? It really detracts from this video.

[@terrymcclain9725]

You drew your picture as the spaceship is moving away, just as Einstein did. If you compare that to the spaceship moving toward you, the vector is positive as it moves away and negative as it moves toward you. Therefore the result of moving toward you is opposite of when it is moving away. When the ship passes you the instant that the time clock is even with you both clocks are running at the same time. This can be shown if the clock on the ship has a green beacon and a clock beside it. As it approaches you the beacon is blue shifted so the tick of the clock is faster just as the blue light has a faster frequency than the green. As the ship comes directly beside you the ship's beacon will instantly flash green, then will be red shifted as it moves away. When it is red shifted the beacon light frequency slows and the clock slows down to match. The frequency of the light and the frequency of the clock are locked together. They must correspond. Relativity, therefore is Point to Point, not Space to Space.

[@RiceLeeR]

Interesting triangle stuff indeed!

[@jrwarfare]

Amazing video

[@mathadventuress]

I’m at the gym and I can’t stop laughing This professor is hilarious hahahaha

[@wildzach]

"Notice how over here it gets really awesome" buahahaha

[@NicolasSchmidMusic]

What an amazing explanation !

[@pyrosplaylist1178]

best video i have ever seen 😂😂

[@B1SpkTKD]

Awesome explanation! Can someone help me? I don't have a solid background on maths, so I don't get why at 10:57 the denominator goes from c^2-v^2 to c*(root)1-v^2/c^2. I'll really appreciate any explanation. Thanks!

[@SirSticklebrick]

His "fancy" is that he multiplies the bottom bit by c^2/c^2. He can do this because any number divided by itself equals 1, so it doesn't change anything to multiply it by 1. So then instead of having c^2 - v^2, he has c^4/c^2 - v^2*c^2/c^2. Then he factors out the common c^2 but leaves the 1/c^2, to get c^2( c^2/c^2 - v^2/c^2 ). To finish up he turns the c^2/c^2 back to 1, and then applies the "sqroot" to the factored c^2, giving c * sqrt( 1 - v^2/c^2).

[@syw0112]

excellent !!!!!!

[@samGhugre]

Cool video. Just one thing ,the delta t which is considered is from which persons perspective , for the one in the space ship should not be seeing his clock moving horizontally away and how is the man on earth supposed to estimate delta t if he sees his clock apparently running faster. Playing with time must make it dinky

[@alloranovak1916]

Wow, this was awesome. Great explanation

[@anthonyconstanti]

Please... the video was good but please oh please, pronouce the word squared and not scwer

[@Restrictted]

i agree, im like wtf

[@Baal3033]

Awesome video! Really passionate teaching :)

[@emiliofernandezlavado279]

Amazingly well explained

[@hopethompson6940]

people who hate math should not watch this video. very good explanation, though! thumbs up

[@RaFaSoAp]

The videos, explanations, and drawings are fantastic. The only thing I can offer to make it better is to please tone down on the squr, its easier to follow if we hear the words we are used to ya know? Overall excellent though

[@chinghoelee9031]

Delta T =Delta To(gama) implies that the time of moving observer goes faster than that of stationary observer.it seems that u mix sth up in the triangular thing

[@nathanbolingo9]

FOR AN ANGLE OF 90 DEGREES THE LIGHT BEAM HAS TO TRAVEL (GAMMA)*D RELATIVE TO A STATIONNARY PERSON BEACAUSE OF V SPEED BUT IF THE ANGLE IS ZERO DEGREE THEN THE LIGHT BEAM HAS TO TRAVEL (V+C/C)*D RELATIVE TO A STATIONNARY PERSON SO GAMMA DEPENDS ON THE ANGLE BECAUSE THE PYTHAGORAS THEOREM DO NOT WORK FOR 91 DEGREES OR FOR 89 DEGREES

[@StuMas]

At 4:51, another reason why the DIAGONAL path doesn't take longer - because the HORIZONTAL motion of the spaceship makes up for the extra Time and Distance the light-beam has to travel. Can the author of this video, please explain why they insist otherwise?

[@GerryBHarris]

Is sound a mechanical exception to the relativity postulate of STR? A straight rigid rod could have the fixed length D with a sound emitter at one end and a sound receiver at the other end. For an observer riding the rod, sound would travel from the emitter to the receiver at the constant velocity c relative to the air. If the rod is at rest relative to the air, then the time t between an emission event and a reception event would be: t = D /c. If the rod is in motion parallel to its length at the constant velocity v through the air with the emitter as the leading end, then could the time between the events be: t = D /(c + v)?

[@nhatmandu]

What if the light clocked is turned 90 degrees and the velocity vector is parallel to the light direction?

[@TheLogmp]

The skwur thing drove me nuts. By far the most annoying touch to an otherwise clear explanation.

[@nathanbolingo9]

THE PYTHAGORAS THEOREM DOES NOT WORK WITH THE INFINITE NUMBER OF ANGLES WHICH ARE DIFFENT FROM 90 DEGREES SO GAMMA DEPEND ON THE ANGLE. THERE IS AN INFINITE WAY TO CALCULATE GAMMA ACCORDING TO THE ANGLE OF THE LIGHT CLOCK RELATIVE TO SPEED V

[@81546mot]

Very nice explanation!! AND you inject a little comedy into your explanation. Very Nice--and HD means we can actually see what you are writing....

[@MohamedGamal-rv3cm]

I like ur way of explaining Go ahead

[@nathanbolingo9]

WHAT WOULD HAPPEN TO GAMMA IF YOU SET THE DISTANCE D HORIZONTALLY INSTEAD OF VERTICALLY?

[@nathanbolingo9]

WHEN THE LIGHT CLOCK IS ORIENTED HORIZONTALLY THEN T=To*(C+V)*D/C THE LENGTH CONTRACTION AND THE TIME DILATATION WOULD HAPPEN IN A DIFFERENTLY BY THE FACTOR GAMMA=(C+V)/C IF V=ZERO THEN GAMMA=1 ALSO

[@zackallen3956]

You're hilarious, guy, don't listen to these haters.

[@39knights]

According to Lorentz doesn't the ship 'spaghettify'? So perhaps the 'triangle' trip is actually the same as the stable clock.

[@DocSchuster]

39knights Spaghettification would occur from tidal forces in an enormous gravitational field. Lorentz tells us that the ship will appear to be thinner to outside observers, but only in ONE dimension. The dimensions that are orthogonal to its velocity are unaffected. But the clock and the contraction both happen together, inextricably.

[@thefunfairvip]

Good job. Time dilation deniers explain how a particle with no mass, ie, a photon can travel from one point to another when it has zero kinetic energy. You will find from the perspective of the photon, no time passes. We say light from a star ten billion light years away takes ten billion years to get to us but since the particle has no mass it also has no kinetic energy hence it isn't moving anywhere. The particle experiences no time. No time passes for the photon even though we say it took ten billion years to get to us. At light speed the particle also experiences zero distance therefore all points in space are the same for the particle which is experiencing zero time between different point with zero distance between them, from the perspective of the massless photon.

[@DocSchuster]

Thanks! Why, though, Matt? Infinity has room for some numbers, don't you think?

[@anoirtrabelsi8645]

From the equation, we can see that Δt is greater than Δto so it means that the period of the clock that's in motion is longer than the one on earth so that's why it's time is running slowly from our perspective right ? Did I get it ? :'D Btw, we can derive the formula using trigonometry ! kzbin.info/www/bejne/rGnPq6aPnZh9iLs

[@nathanbolingo9]

LENGTH CONTRACTION AND TIME DILATATION WOULD HAPPEN BY GAMMA=(C+V)/C WHEN ORIENTED HORIZONTALLY IF WE USE THE HORIZONTAL LIGHT CLOCK AND THE VERTICAL LIGHT CLOCK TOGETHER WE 'LL NEVER KNOW THE TIME WHEN WE ARE MOVING AT V SPEED BECAUSE WE HAVE TWO GAMMAS

[@shivaniits]

You made me laugh but also a very clear explanation 👍🏻😊

[@annoloki]

But is time actually slowing down, or is everything simply running slower due to the fact that everything is made from mirror boxes aka time clocks? Eg, if you plot an orbiting electron around a moving nucleus, you see the electron has a lot further to travel in a single orbit... or, if you say the excitation in a quantum field bounces back 'n forth between bounds in the higgs and other fields, that's essentially the same thing as the mirror box clock... so an atomic clock used to time the ticks in the mirror box will slow down in the same way as the bouncing photon in the mirror box does... as soon as you do away with protons etc being particles, and instead they're bouncing excitations in fields, it no longer makes sense to say that time itself slows down, but that all vibrations in fields have longer wavelengths... right?

[@ismaelalaniz984]

How did Einstein derive it ? any references ?

[@trsomas]

Can we really treat a clock which uses pulse of light as stationary clock? The pulse of light is a part of the clock and this pulse is not at rest in any frame; rather it is moving at c. So how can we say that this is a stationary clock?