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@krislogy

3 ай бұрын

Minor correction. Fact. Tu. Ality. Not Faculty. :)

@adamsheaffer

3 ай бұрын

But, what if an object travels so close to the speed of light that it travels across the entire observable universe in femtoseconds of proper time? Would the object continue on its trajectory until it hits into another object? Or would it wrap around the universe infinitely or stay in place in empty space as the universe expands so that the object HAS TO experience time?

@tokajileo5928

3 ай бұрын

where to get that t-shirt? XL size

@TriTr-qd2bd

3 ай бұрын

I was smoking a reefer last night and a thought came to me about how would the universe look if light didn't have a speed limit and then this video popped up on my feed, nicely nicely.

@petevenuti7355

3 ай бұрын

So when I'm playing chess with my computer and our kings wind up next to each other, and im pissed because the computer wont let me take its king saying its an illegal move but it's king takes mine‽ I shouldn't be learning chess from a computer.

man your topics are always so interesting i just have to watch

@Mahesh_Shenoy

3 ай бұрын

Thank you :)

@whykoks

3 ай бұрын

Do you have girl friend?​@@Mahesh_Shenoy

@arkdark5554

2 ай бұрын

No. At the speed of light…the time stops. According to Gödel's interpretation of Relativity.

@Dabmonger

2 ай бұрын

I'm with that line of thinking, but then if equations are allowed to be blown up do we assume that singularities exist?! Perhaps time not moving and singularities are connected in some way, at least in telling us that we're missing something major in our knowledge!

@kellyrobinson9564

2 ай бұрын

You don't understand inertial reference frames

If an object travels almost at c, from its reference frame the universe is traveling at almost c and is extremely contracted in the direction of the movement. So, from its perspective, it would traverse the entire universe almost instantaneously. I think looking this way we could say this object experiences almost no time, meaning it does not see the universe evolve in the very short time (from its perpective) it took to traverse the universe. If you think regular objects do not traverse the entire universe, but a smaller distance between object creation and destruction, for this object it existed during almost no time and was almost instantly destroyed

@QuantenMagier

3 ай бұрын

That is also how I see light, it's as if the photon was using a wormhole through space-but-not-time, and that wormhole is called the EM-field, but it's an imperfect wormhole due to redshift..

@Dabmonger

2 ай бұрын

I view light in the sense of limits and infinities, that blow up equations. Like singularities. We're clearly missing something significant in our understanding.

@petejohnston5880

2 ай бұрын

You're absolutely right. As every point in the universe sees light traveling at the speed of light relative to it, then light in turn sees every point in the universe moving at the speed of light relative to it self and hence the whole universe is length contracted to be infinitely thin in the direction of travel. The universe becomes an infinitely thin but very wide pancake. This means that the point in space where it starts its journey is the same point in space where it ends its journey and it take zero time from its perspective to travel from start to finish. So does light experience time, well its life is over before it has a chance to experience anything. We see light moving but for it, it all happened and finished it's journey before time even moved.

@Dabmonger

2 ай бұрын

​@@petejohnston5880It can be argued that light does not experience time, and a photon is in all places on its path at the same time.

@QuantenMagier

2 ай бұрын

@@Dabmonger Nope, photons are just the exchange particles, there exist no photons on the path of light, just electromagnetic waves, the photons are only created from those electromagnetic fields by interactions with matter.

I have a masters in Math, and your videos have allowed me to appreciate axioms, postulates, and modeling so much more.

I'm two minutes in and you are already blowing my mind about concepts I thought I understood. I absolutely love your videos, you are by FAR the best physics presenter and explainer since Feynman. Keep up the great work, I'm hanging on your every word now!

@Mahesh_Shenoy

3 ай бұрын

Wow, that’s super encouraging to hear. Thank you :)

@everythingisalllies2141

3 ай бұрын

I love it when people actually believe that they can really KNOW this stuff. They really have convinced themselves that they have actually understood what we can never possibly understand. Understanding what does light experience, is a classic case of over confidence. google the free ebooks, "Dave vs Hal 9001" for more information. You may change your mind about what you think is real and true.

@auriuman78

3 ай бұрын

@@Mahesh_Shenoy it's true my man, I look forward to seeing your presentations when they drop in my notifications. They're actually fun dude, you make science what it's supposed to be, awesome 👍

@Littleprinceleon

3 ай бұрын

​@@Mahesh_Shenoy, you help us to have some glimpses from the shoulder of science giants. That's the POV worth to achieve. Many thanks 🙏👍

@Robienko

2 ай бұрын

Because it's not correct

05:40 f _Looking from s.o.'s perspective basically means looking from s.o.'s reference frame._ I'd put it differently: By "looking from s.o.'s perspective" physicists mean *describing the scenario from a rest frame of her/ his.* ▪︎A frame in this context is a coordinate system which basically maps all of spacetime, so you can't really looking _out of_ it. Rather you express physical quantities in those coordinates. ▪︎Everything kind of has infinitely many rest frames with different orientations or origins. ▪︎Your reference frame is the frame you use to describe a scenario. This _might_ be a rest frame of yours but it _doesn't have to._ And in everyday life, it seldom is. Mostly we implicitly use a frame bound to Earth; otherwise, if I went to Cologne by train, I'd have to say "the train has come to rest (a very active rest like that of someone running on a treadmill) and lets Cologne approach it".

@everythingisalllies2141

3 ай бұрын

google the free ebooks "dave vs Hal 9001" you will be surprised what you will discover.

I read somewhere how we could imagine photon 'perspective'. From it's 'point of view' there is only act of creation and then instantaneous act of annihilation (when it interacts with some object). There is nothing in between for photon, it does not 'experience' time.

@Vexas345

3 ай бұрын

But why assume it's instantaneous?

@G0ldbl4e

3 ай бұрын

@@Vexas345 They experience infinite time and length contraction as per special relativity

@auriuman78

3 ай бұрын

Well as far as it (the photon) is concerned, it might as well be instantaneous, even if it took 13.8 billion years in reference to me? Zero time experience is pretty well instant right? Kinda baffles the logic of normal intuition when you realize that time is truly based around the fastest thing in the universe, that's how it ought to be reasoned at least, if you want to truly understand what time is. Base your reference at the fastest thing known, kind of like temperatures and zero. There's a limit and we reference from there in science, hence Kelvin. Why not do the same with light\photons\emr? I'm not trying to turn our time reference understanding on it's head, Just like we don't use Kelvin in everyday life. But for scientific matters, yeah 👍 I think it would simplify the problem of medium speeds not matching to do that way, cause it's all light speed, just different frames of reference right? I'm not gonna even attempt to address the things that would happen sub-planck though, haha, not qualified. It'd be weird for sure, in case this isn't weird enough for you. I am in no way certain there's anything meaningful below Planck pixel, but I'm certainly not opposed to it being more than not meaningful, so what if the Schwartzchild radius = black hole. Another thing we don't really know anything about other than they're there and they're doing something deeply interesting.

@Vexas345

3 ай бұрын

@@G0ldbl4e They do not. The math for time dilation/length contraction doesn't work for things moving at c. They don't have reference frames, so special relativity doesn't apply.

@auriuman78

3 ай бұрын

The very idea that the photon does not experience time, as far as it's concerned it's just sitting there, good Lord man what a concept. I mean really if you think about it 🤯 trillions of trillions of trillions of photons, all different amplitudes and wavelengths, interacting with different interferences to form stuff, all infinitely small and large at the same time, this is weird stuff seriously. It makes me pull back to the holographic model, you know what I mean, if it's just there then not, everything else around it being what's in motion... Which is also a bunch of other photons at rest, blipping on and off here and there. Kind of leads to the idea that maybe it is in some way intricately holographic. I mean it's pretty much all electrical\em. I learned that some years ago during a heroic experience that I did not plan on taking but accidentally did anyway. Idk I think a lot about stuff but this one I think is above human thinking. I'm definitely not smart enough to grapple with that one, but I'd be willing to bet my life that it's so ridiculously elegant and simple that we're just looking right over it. It's probably right in front of us 😅

I followed your recommendation in a party, and the dude telling the story punched me in the face!!!

@Mahesh_Shenoy

3 ай бұрын

What recommendation? :D

@rodschmidt8952

3 ай бұрын

@@Mahesh_Shenoy probably saying "you're breaking the rules, you cannot use SR to conclude anything once you've broken SR"

I always just thought about it like: If you're nearly at the speed of light (c) others would see your time go very, very slow. But for you in this reference frame your time goes "normal" but everything around you seems to be very, very fast. So if you would be at the speed of light for the others your time stands still (∞ slow) but for you everything around you would be ∞ fast. So for you the whole age of the universe would be over in 0 seconds. So you can't experience anything outside of your reference frame. And that's the problem that arises like you described the problem in another way.

@wailer27

3 ай бұрын

That's not how it works as you're skipping relativity. You see the universe moving slowly too as it is also moving relative to you, therefore your clocks would agree. Only when you accelerate or spend time in a gravitational field will your clock slow down relative to everything else.

As always these videos are amazing! By far the best most easily digestible explanations of physics concepts I’ve ever seen.

@johnmagnotta8401

2 ай бұрын

Hear hear

@johnmagnotta8401

2 ай бұрын

Or is it "Here, here?"

Excellent argument, your logic is very sound - it brings to mind constructor theory. Also love the chess analogy reminds me of Feynman's use of a chess analogy. Thanks very thought provoking.

@Mahesh_Shenoy

3 ай бұрын

Thanks, Jonathan. :)

@magnuszakrisson

19 күн бұрын

But you can have two kings next to each other in chess. That would have required an illegal move though but it can still happen. There has even been a real chess game where the judge ruled that the one who played a move after an illegal move lost, because it was illegal to to continue after this illegal position and create a new illegal position. When the player who made the first illegal move pointed that out the judge concluded that the last player who made an illegal move lost! ;) Not sure what conclusion we can draw about lights perspective from this though lol

Love watching floatHead Physics! Your enthusiasm is infectious and I will be showing my teen daughter your videos to help her intuition of physics. Thanks, Mahesh!

First, why are you so good at incorporating your sponsors in your videos? You're simply too good. Secondly, I totally agree with correcting people's understanding about certain subjects and misconceptions. Though, I would totally commend them for thinking about these things and being curious. I also can understand others telling others "click bait" concepts. I feel it is to get then intrigued and interested to learn more. Promoting education, critical thinking and scientific literacy is definitely a great thing to do.😊

Hypothetically, if I make a phone call to my friend who is near the sun, than he would recieve it after more than 8 mins 16 secs and we will have conversation at each interval of more than 8 mins 16 secs?

@silverrahul

3 ай бұрын

yes

@manasyadav1993

3 ай бұрын

Duh

@Farming-Technology

3 ай бұрын

I'd check with your mobile provider first to see if interplanetary calling is included in your package. Could be expensive 🤠

@ashutoshsethi6150

3 ай бұрын

He is toasted.

@Fluxikator

3 ай бұрын

The Interval would be double that. You Record your message and send it away. After 8min 16 sec your friend will recive it. He Records an answer and sends its back. After another 8min and 16 sec the answer has reaced you. So for you the time it takes from sening your message and getting an answer is 16min and 32 seconds. + the time he has used to reply to your message. Thus the interval is at 16mins and 32 seconds at a minimum.

Oh god I recognize your voice from khan academy

Thank you very much for your infectious enthusiasm about physics. I love it! Years ago I took an advanced physics course and you brought back fond memories.❤😊

I'd love to see a video where you focus on the reference frame more, with more than one observer. Observer 1 at rest, observer 2 moving at almost the speed of light relative to observer 1. Observer 3 accelerating at 1000 m/s/s relative to observer 2. Do this and show each observers perspective and how they experience light. I think it would make a fascinating video.

And you might say, mahesh - i always wondered if we could have a beer together. But einstein says yes, of course you can have a beer with mahesh.

What a video! I think this series is one of the greatest assistant to understand special theory of relativity

@Mahesh_Shenoy

3 ай бұрын

Wonderful to hear that :)

Mind duly blown. I had never considered that consequence of the second postulate. Wonderful. Thank you.

I really liked how you presented your understanding step by step emerging from your confessed confusion. Also loved how you made it a conversation between Mahesh, Einstein and Feynman chipped in, that made it both interesting and funny. A honest presentation full of excitement. Liked and subscribed!

Could you say that the faster you are moving, that the objects approaching you from the front seem to have their time speeding up (like a Doppler effect with a sound pitch getting higher)? And could you say that as you get arbitrarily closer to the speed of light, the passing of time of objects in front of you gets arbitrarily closer to infinitely fast? Or am I off base here?

@renedekker9806

3 ай бұрын

_"Could you say that the faster you are moving, that the objects approaching you from the front seem to have their time speeding up"_ - if you are asking about the light that you see from the objects that approach you, then that is fully correct, yes. That is mostly due to the Doppler shift of the light. If you asking about what you would conclude about the clocks of the others, then your conclusion would be that they tick slower than yours. That is due to the relativistic time dilation.

@Rationalific

3 ай бұрын

@@renedekker9806 I see... Thanks for the reply!

Thanks again great videos as usual. Love the energy!

@Mahesh_Shenoy

3 ай бұрын

Thanks, Donny :)

Now that the "experience" part is ingeniously taken care of, Shall we move to the next innocent but tricky term i.e, "Time"?. What is it? is there any intuitive sense of this term? Is it universal or it's just an emergent phenomenon as a statistical byproduct of entropy? I thought I almost got it from the Arvin Ash's video on the topic but would really love to have it reimagined with your enthusiasm and care. Great work brother, I absolutely admire your explanations. ❤

I needed this channel for so long and didn’t even know 😱 Finally instead of just knowing the right answer I can understand what is going on. TY so much, great work! 👍🏻👍🏻👍🏻

Awesome video Mahesh. I wish you pointed out that when an object approaches speed of light although it would experience proper time, if it eventually stops, its time would be behind the proper time for the non moving reference frame. That’s an important bit of info. Yes ?

@Mahesh_Shenoy

3 ай бұрын

Not sure how it would be relevant. If folks don’t already know it, it’s not that easy to make sense of it without diving deeper into it. I think.

@manasyadav1993

3 ай бұрын

Well you have the other awesome videos. So it makes sense that you didn’t specify it. There is nothing wrong with my understanding tough right?

@classicalmechanic8914

3 ай бұрын

@@Mahesh_Shenoy According to relativity it is equally valid to claim photon is travelling at the speed of light or photon is stationary and everything else is travelling at speed of light relative to a photon. Photon's perspective exist but it is not included in special relativity. If photon's perspective is not important is like claiming it is not important what happens to photons at the event horizon of a black hole. General relativity breaks down at the event horizon the same way as special relativity breaks at the speed of light. Einstein's theories break down at the speed of light which results in infinities that show up in physics when you are doing something wrong.

@kylelochlann5053

3 ай бұрын

It's not important as at no point are any clocks actually ticking slower. It is fundamental to relativity that all identical clocks tick away at the same rate, everywhere, and under all circumstances of motion and orientation. What you're alluding is that the integral over the accelerating clock's world-line is simply shorter (wrt the global coordinates) which is not meaningful here in any obvious way.

There is another counter-attack: how much time does an observer experience between photon emission and photon absorption, if he is tracing the same path as the light, travelling with a speed limiting to the speed of light? In that sense, you do get that the events (emission and absorption) happen basically immediately one after the other, leading to a loose statement that a photon doesn't experience any proper time. In "photon's frame", it is born and dies at the same time - by definition, because the space-time interval is 0 on a light-cone.

@Mahesh_Shenoy

3 ай бұрын

That’s because, from that frame, the emission and absorption locations were infinitesimally close to each other. If my neighbors house is infinitesimally close to my own, the moment I step out of my house, I would have stepped into the neighbor’s almost instantly. That doesn’t mean I don’t experience time, right?

@Simon-fg8iz

3 ай бұрын

@@Mahesh_Shenoy If you only exist while traveling from your house to your neighbour's house, and the threshold is infinitesimally narrow, you could say that you only exist for a single moment, not any finite interval of proper time during which you could experience anything. I'm thinking of neutrinos here, who do have "time" to oscillate during their flight. Again, of course, Einstein's argument holds that the limit c→∞ isn't strictly reasonable. p.s. Just keeping the back-and-forth discussion with Einstein here, the conclusion in the video is of course correct :)

@ramankhatri

2 ай бұрын

Photon experienced time but unfortunately nothing happens in that time as the space outside is not changing. It's as if it went out of the universe and popped right back in just before annihilation.

@lewis7515

2 ай бұрын

Isn't that just sophistry? You've just used different words to suggest the same thing as an imagined frame of reference that is travelling in equality to light.. The logical conclusion of SR is that there is no, "basically immediately, one after the other", by Light's terms - that is is fudge the conclusion for the convenience of human interpretation. The natural consequence must be that Light does _not_ perceived Time - because by Light's terms, there is no such thing as, "Time": and there is no such thing as, "Space". Those attributes only mean anything, to us and other entities of those dimensions... For Light, there is absolutely nothing. That is: Time and Space are emergent properties - dimensions in a Universe that Light, by nature, has no access to: because they and that Universe are, by nature, coiled up to zero and contracted out of existence. Every single thing, is beyond Lights event horizon - where Light, is it's own event horizon. That's why the question makes no sense - but to say that the question makes no sense isn't necessarily a mature or complete answer to be shared among adults. The simple answer is that no, Light doesn't experience Time. The expanded answer is that Light cannot experience Time l, even if it wanted to - because neither Time nor anything else actually exist on Light's side of Light's own event horizon. That is to say: if Light could communicate, it couldn't process a question on whether it experiences Time? It wouldn't - couldn't - even have any single idea, whatsoever, of what you were even talking about: "Time", and, "Space"?..... Utterly meaningless.

@leonardopizzini1443

2 ай бұрын

@@lewis7515 i don't realy get this. Why shouldnt light experience time if we see time as the change happening to matter in space . it should in my opinion. Giving light a perspectiv as a human doesnt make sense to me but looking at it from the outside its clear that change is happenig while it moves so how could it be different from the inside perspektiv of light? is it just a hypothetikal question that doesent realy apply to the real world?

Bhai re addict ho jata hu teri video ka Mat banaya kar aisi itni badhiya video Subah 5 baje teri video ko play kar diya dekhna nhi tha bas yuhi save karne ka irada tha Ab nahane nhi ja paa rha. Teri wajah se school jane me late ho jaunga😢 BTW I am physics teacher Feynman lecture ki book kharid ke rakhi thi padhne ka time nikalana bhul gya tha Ab tu aisi aisi chije lata hai to padhna padga😅

@Mahesh_Shenoy

3 ай бұрын

Ab bas bi Karo bhai. Rulayega kya?

"There comes a point in every man, woman, and child's life that they wonder - Does light experience time?" See, that's the mindset of a great theoretical physicist..

Light is a null vector of space time which mean that is proper time is always 0 . This is can be seen from the equation of proper time `dtau^2 = dt^2 - 1/c^2 dx^2' which is always 0 for a photon whatever is the reference frame. So saying that light as zero proper time is perfectly legit, and this in all reference frames.

@kylelochlann5053

3 ай бұрын

Well... not exactly. The equation you should have is general flat-space metric: ds^2=-dt^2+dx^2. It is only in the special case of a time-like curve that ds^2=-dτ^2. The proper time along a null curve is not 0, it is undefined.

@stephanevernede8107

3 ай бұрын

@@kylelochlann5053 Thanks for your comment. If I understand well your point, you agree that light is a null vector of space time and has 0 norm, but you point that this norm can not be called `proper time` but should only stick to `norm`. How is this more that a play on word ?

@kylelochlann5053

3 ай бұрын

​@@stephanevernede8107 Given a spacetime curve, S, in arbitrary spacetime coordinates with tangent vector, U, the "norm" is then the inner product on the tangent space, g(U,U). This would have nothing to do per se with how the curve is parameterized. For a time-like curve, the norm is a constant, g(U,U)=1, we can use a clock to measure off the distance along any time-like curve (if measurement shows that all identical clocks tick at the same rate, everywhere in the universe, and under all circumstance of motion and orientation). A null curve has no spacetime length, so in what sense can a clock be used to define time as a parameter to measure length along a length-less curve?

Dumb question perhaps.. if an object is traveling close to C does it appear colder to a stationary observer? My thinking is if time slows for that object including all particle momentum, average kinetic would appear lower. And I suppose all stationary objects would appear colder to the moving object too?

@Mahesh_Shenoy

3 ай бұрын

I think “colder” is a very lose word here. If you are specifically thinking about the temperature, then you will have to measure it in its rest frame, no? (I mean you need to stick a thermometer in there somewhere, and now the thermometer is in the rest frame of that object). But, the average thermal energy should slow down. So, that’s an interesting question. Let me add it to my list of topics to research more. Thanks for the question. It’s anything BUT DUMB.

@a64738

3 ай бұрын

That is actually a very interesting question...

@amaze2708

3 ай бұрын

@@Mahesh_Shenoy thank you for the reply. To expand on this.. remote observation of temperature is possible (we measure temperature of everything in space remotely). Also colder == more red shifted.. what if part of the red shift we observe from distant objects is because they are at relativistic speeds from our reference frame due to expansion? Obviously Doppler shift is still relevant. If we see their “clock” moving slower, we should also detect the temperature as lower; all time based events are affected, and temperature is time based. I just solved dark energy (Kidding).

Man you are the best. The concept best thing is that you use intuition for everything. Thanks man , helped me clear my curiosity

I was literally looking for a person who could explain things that comprehensively. The way you crack things, like the scientists who are much more eager to break apart the subatomic particles in the Large Hadron Collider to understand the behavior or laws of this Universe. The power of visualization and the interpretation you have mastered is just Astonishing. I don't have words for you, you are just limitless. Keep continuing the series I am learning a lot by opening different ways to visualize things for Better interpretation. My regards to you.

Mahesh sir please cover quantum mechanics stuff also......

@Mahesh_Shenoy

3 ай бұрын

Yes, yes! On my ever growing backlog of videos.

I really like your videos as a physics student. Especially the dialogue between you and Einstein etc. Keep up the great work!

Nice content! The moving clock ticking slower points directly to the twins paradox which has one of the hardest wikipedia pages I've ever seen lol

Sir another question why the speed of light is less in water if the speed of light is always same for all observer? Love your videos

@AdritoMitra

3 ай бұрын

And also if the speed of light is less than the speed of light then Photons will have mass. As you said in that video.

@Mahesh_Shenoy

3 ай бұрын

I think I should cover this in a separate video. Adding it to the list. Short answer is, it doens’t make sense to think of “speed of photons” inside a medium

@AdritoMitra

3 ай бұрын

​@@Mahesh_ShenoySir it will be very helpful for me because I can't find the answer. Love you and your videos from West Bengal ❤❤❤

@Farming-Technology

3 ай бұрын

​@@Mahesh_ShenoyI would look forward to that video. Some points of interest for me would be, is causality slowed in a medium? When you say vacuum do you just mean free from baryonic matter? Also how does the light accelerate¿ when entering vacuum from a medium? I don't know enough to ask the questions correctly but it is very interesting to me and the way you explain mathematics to us laypeople is some of the best I've seen.

@wynq

2 ай бұрын

@@Mahesh_Shenoy I also look forward to this video. Can you also include in that video an explanation of what's going on in the experiment where Hau and Harris "stopped" light in a cloud of ultra-cold sodium atoms? I'm having trouble understanding how the photon wouldn't see its own velocity as 0 instead of c.

I studied this subject some decades ago. My interpretation of this question was somewhat different. You are focusing on time for the photon and the photons rest frame. You don’t have to do that. Instead think of travelling ‘almost at the speed of light’ and what you will see is that your own time passes normally, but the entire rest of the universe is Lorentz contracted in distance. In other words, you will (due to length contraction) arrive almost immediately after you leave - as the distance to travel is minuscule - even light years would (if you go fast enough) shrink to millimetres. The reason light does not experience time is nothing to do with rest frames, but rather that at the speed of light it arrives at the same instance it leaves / because the ‘length’ of its travel has shrunk to zero. This is in a perfect Vacuum. If the vacuum is not perfect, then the light will experience some minuscule time.

@damc7456

3 ай бұрын

Excellent... Also, I think the video would better serve viewers by comparing clocks. If a photon were to look at its wristwatch, it would observe the hands moving in proper time. Sure, but an observer watching the photon go by would observe that the photon's wristwatch has hands that aren't moving at all. As you point out, this is explained by the photon observing that all the points through which it travels at the speed of light have contracted into one infinitesimal. I'm super curious how this topic relates to entanglement. Could it be that entangled pairs, despite potentially being separated by light years, "think" that they continue to occupy the same point because per their observation, zero time/space has passed between before they were split and when they become disentangled?

@Jim-uq1mc

3 ай бұрын

In a reference frame the observer is at rest; not the photon is at rest. The photon needs to travel at the speed c with respect to any observer - even if the observer would himself travel at c with respect to some other observer . . .

@Littleprinceleon

3 ай бұрын

​@@Jim-uq1mc two photons moving at the same direction: do they travel at c from each others' perspective?

@damc7456

3 ай бұрын

@@Jim-uq1mc In my comment I make the photon the observer. "If a photon were to look at its wristwatch..."

@kylelochlann5053

3 ай бұрын

Time cannot be applied to a null curve, that is, for a photon. Light in a medium will travel along a world-line (time-like curve) so there's no difference between us and light as far as time goes.

I watch a lot of these types of videos, and you just make things so much easier to understand than pretty much any other channel or there.

Love your content! Two questions… Would a frozen beam of light (like the pulse they froze for a full second) not be considered light at rest in an inertial frame (assuming it can be replicated in a vacuum)? In the chess game, am I wrong to think the rules don’t say you cannot move next to each other, they just say if you do you’ll die so you don’t? You’re allowed to move there… the game is just over if you do because whomever has the next move would simply win the game. People may not play out the final moves (they forfeit etc) but a King next to a King I don’t believe has a rule of not being allowed but rather a rule that it comes with a consequence. #highthoughts

@Mahesh_Shenoy

2 ай бұрын

Speed of light will ALWAYS be c in vacuum according to special relativity. No, that move is not allowed. Try it in chess apps :)

Mahesh I have a doubt ... Why pair annihilation doesn't takes place in mesons ? I surf the internet and found some answers..i know charged pi mesons don't annihilate because the quark and anti quark are different flavours but what about the neutral pi mesons? Some of them said annihilation is not a instantaneous process..we know that mesons are unstable so before annihilate..it's starts to decay into other subatomic particle...is that right explanation ? Which property differentiate the lambda -0 and Sigma -0 in elementary particle because both are made of up quark-1 down quark -1 and strange quark - 1 ? If anyone have the answer let's start discussion 😅😊

@Mahesh_Shenoy

3 ай бұрын

I have no clue about this. List most stuff in my life! But adding it to a list of my research topics

Can you constantly accelerate to closer to the speed of light such that, from an outside perspective, the light never reaches the top of the clock and ticks? I suspect from inside the vehicle, you would just see space continually contract such that you would arrive at any destination point before light had a chance to tick the clock.

@rodschmidt8952

3 ай бұрын

I like this question. I think you are right

I think you are confused by what a frame of reference is in physics. A frame of reference is a set of coordinates to describe a velocities of objects in that frame. A key feature of an INERTIAL frame of reference (the one we use in physics, which you are describing) is the frame is not accelerating, which does not mean that the speed is zero (which is also a “loose” term as describing velocity in respect to something, like the ground or earth)

@ToyyinnAuslander

2 ай бұрын

Exactly. At rest also extends to straight line, non-accelerated motion which is exactly how photons travel through the vacuum of Space. I think this explanation is inconsistent with the very foundational basis on which it claims to sit. In another video, he explains why everything at rest in the universe is moving through Time at the speed of light. Using that thought experiment, he goes on to agree that the faster one travels, the greater their displacement through Space and the less their displacement through Time, till, eventually, the particle in the thought experiment reaches c and employs all its speed in the spatial dimension with nothing left over for Time hence, objects travelling at c experience no time. This video appears to contradict that. 🤷🏾‍♂️

Okay, firstly, I can not get enough of your excitement and energy. I am always glad to see another one of your videos uploaded. Now onto the fun part. I think the better question is "what IS time for light?" I have thought about this a lot, and here is what I came up with. Light doesn't "experience anything except the start and stop of its travel. Say it is emitted from a lightbulb, travels to the surface of the moon, and gets absorbed by an atom in the moon rock. From the point of emission to the point of absorbtion, there is no interaction. As such, there is no "time". Time requires change, and for the photon, there is no change. So what does this "look like" for the photon? Nothing more than the series of interactions; emission, absorbtion, emission, absorbtion, over and over, with no "time" (change) to speak of in between. Thus, for the photon, time is nothing more than the series of interactions it has. To us there may be hundreds of years of travel in between, or a millisecond, but to the photon it is just event, event, event.... Does this perspective still seem to jive with special/general reletivity?

@kylelochlann5053

3 ай бұрын

No, the start and stop are the same instant i.e. the spacetime interval is zero, so there is no meaningful attribution of "time" to a photon (or along any null curve).

@klosnj11

3 ай бұрын

@@kylelochlann5053 if they are the same instant, does that mean all instants for a photon, from the start if the universe to the end, happen simultaneously? Parmenides is pleased! But in all seriousness, I dont think your statement is any different than mine. There is no "time" between each event for the photon. "Time" for the photon is just the list of events that occur. So you could only ask "how many events back did it get emitted from that atom?" But you couldnt ask "how many seconds ago was that".

@kylelochlann5053

3 ай бұрын

@@klosnj11 No, there is no list of events for a photon. In essence there isn't a photon, just an exchange between emitter and absorber that instantaneous in spacetime. If you can, see if you can find a paper by Willis Lamb (of Lamb effect fame) called "Anti-Photon."

@klosnj11

3 ай бұрын

@@kylelochlann5053 an interesting perspective. I will look into that.

hello sir I am really in love with your videos, as you are covering all these topics could also make a video on how to intuitively understand potential energy. it is one of the most complex topics in physics and I am eagerly waiting for your wonderful explanation.

I learn more from you in a 14 minute video than all my years of high school. Thank you sir!!

I love the way you break these concepts down in ways an average person can understand. I was a little bit disappointed in this video when I saw the asterisk though: *length contraction ignored. I have always been so fascinated by imagining what the universe might look like from lights perspective, and in my mind, I always assumed light (sorry Einstein, *an object moving *almost* the speed of light) would experience the universe as (almost) two dimensional in the direction of travel. Even if the clock is moving at normal speeds from that perspective, the way space dilates is still fundamentally different from our usual 3D perspective. I was really hoping to see an animated view where the cart was bouncing up and down while the light particle was stationary so we could see how the cart contracted in both the X and Y directions.

I think the more intriguing point with the "experience" of something moving "almost" at the speed of light is that it would experience ending up at any destination "almost" instantaneously. If it keep going without any destination it would experience ending up infinitely far into the future (whatever that means) "almost" instantaneously. If it could do this indefinitely it would for sure experience the clock ticking as usually. But that it would even have time to experience one tick of the clock before either smashing into something or getting to the end of times is not likely.

Great show! I suppose that one could make the argument, that light doesn't experience time precisely because photons going at the speed of light don't experience reference frames, so they couldn't experience time either. The only way they could experience time in the first place would be through a reference frame.

I think some of the confusion comes in trying to understand length contraction in this context. Traveling very close to the speed of light, you experience proper time, yes. But the distance between the start and end points would be much shorter and take less time than it would for an observer watching you or for a traveler going at non-relativistic speeds. That makes it sound like you'd experience "no time".

I have a rebuttal. To invent an idea that breaks rules does not necessarily mean all rules must be thrown out. A clear example: sqrt(-1) used to be thought of as a meaningless question that broke foundational rules, until certain mavericks said, "Let's do it anyway and see where it takes us!" They didn't have to reinvent all of math, they didn't have to get rid of "a negative times a negative equals a positive," they just invented a new abstract concept that turned out to not break math when implemented. A tweak to the rules (i.e. overturning the rule that there's no sqrt to a negative) was enough. Likewise, tweaking the postulate to say "all *sub-c* inertial reference frames" (it already has "inertial" as a qualifier, after all) allows for everything special relativity claims to remain the same (since it's already assuming all reference frames are sub-c), while allowing for mavericks to break the rules beyond the limits and see what happens. So I don't think you can really say (at least as it was presented here) that you can't tweak the postulate while retaining all its current predictions, just like the introduction of the seemingly-nonsensical *i* didn't undermine the math of real numbers in any way.

That asterisk "ignoring length contraction" is doing a lot of work here, since in "light's reference frame" the universe is 2-dimensional, and its velocity is zero in what we would call its direction of travel (because for a photon, that direction doesn't exist). But real photons don't travel in only one direction, they propagate with a probability cone. Might be some insightful math to be done there...

@lewis7515

2 ай бұрын

How have you concluded with such certainty that Light's universe is 2-Dimensional?..... Light's velocity is zero in its, "direction of travel" - purely from our, practically-useful, perspective, of Light's perspective. However, surely, Light only has a, "direction of travel", at all, from our perspective, of Light's perspective? That is: isn't it the case that Light's, "travel", is only perceived? Light doesn't travel, it cannot - we call how it presents in our Dimensions, "travelling", because it's intuitive and helpful. Meanwhile, isn't it actually the case that Light only simply _propagates_ - from the point that it manifests? If that is the case, then Light must propagate, at the speed of Light. If that is so, then Light simply propagates, from wherever it manifests, in every Dimension, in every direction, equally - which is: at the speed of Light. Wouldn't that then mean that every direction and every Dimension: is zero? Isn't the conclusion, then, that while there is no, "direction of travel", from Lights perspective - the exact same terms apply to all other, "directions": that it could only move to, at the speed of Light....So, wouldn't there, equally, be, no, "Direction" - in any non-direction it could move to?.. Must it not then be the case that there are no, "Directions", whatsoever - and, by that token, no, "Dimensions", in any non-direction, for Light to not, "travel", to? Isn't it the ultimate conclusion that, for Light, there is no, "Direction", at all, that it could travel to at anything less than the speed of Light - meaning there is no, "Dimension", whatsoever, to not, "traverse": with the result that there is no, "Space"; no, "Time"; no, "Thing"; no, "Where" - and there was not, is not, and never could be... Would it not be that, for Light, _all_ is simply null - and moot?

This was so much fun. I laughed all the way through. "That question is meaningless" but delightful!

I believe there's no term "wrong question" Questions and curiosity are diamonds

Great video, as always. You never fail to impress I have a follow-up question. If light had eyes, what would it see when it looked at us. If the answer is that we cannot use relativity, then what would it see at close to speed of light

This highlights an important distinction between pure mathematics and physics. Math is an excellent tool for describing the reality (maybe the best tool we have?) but still will never "be" reality itself. The hard part is knowing where the math diverges from the physics.

I also asked myself this question, and, hopefully, i have a similar answer to what Einstein would have given. I phrased the question like this: If I approach the speed of light relative to the centre of mass of the Milky Way, I see the Milky Way's length along my direction of travel as approaching 0. So I should cross the Milky Way in a length of my proper time that approaches 0. But an external observer (who is at rest with the Milky Way's centre of mass) will see my velocity as approaching c, and hence my length will approach 0, while the galaxy's stays "normal". So the external observer would see me cross the galaxy in a long amount of time, nowhere near 0.000...01 seconds. So whats the solution to this paradox? After 0.00..01 seconds have i, or have i not, crossed the galaxy? Who's right - me or the external observer? The answer i could come up with is this- There is no shared definition of "right now" between me, and the external observer "B". So while my journey takes 0.00...1s in my time, it takes some years in B's time. B and I, however, are using different standards to measure the distance between two events - me setting off, and me crossing the galaxy. That's why we don't agree on the time between those events. As you can see, until now, the situation is perfectly symmetrical and both of us are equally "right". So we just don't agree on the time between two events. But thats ok, it happens all the time in special relativity. Also B would agree on the length of *my* time it would take me to cross the galaxy because he sees my clock as very slow, approaching not ticking at all. So he would agree that it takes me less than a second of *my* time for me to cross the galaxy. I think it's beautiful how this fits so nicely - i measure so little time due to velocity which manifests as length contraction, while B measures the same length of *my* time, again, due to velocity, but this time it manifests as time dilation. And the result is exactly the same in both measurements. Maybe this shows the deep similarities between space and time, and why one can't be without the other, why we speak about spacetime together, not separately. But what if i turned around and came back to B, and we compared our ages? This is called the twin paradox. To come back, I'd have to accelerate. Time, space and simultaneity are relative but acceleration is absolute. So the moment i accelerate towards B, i break the symmetry. Now both of us have traveled thru spacetime, between two events - me leaving and me coming back. However my path was more thru my space and less thru my time, B's was more thru B's time and not at all thru B's space. So B has aged more than me when we meet again. And this comparison is only valid if and when we do meet up, otherwise you can't ask both of us how old we are right "now" because there is no meaningful way to define a shared right "now" for both of us.

@bobpower9189

2 ай бұрын

Supposing you were to introduce a third perspective into the twin paradox scenario. One in which a spaceship is always manoevred to be halfway between the two. Putting myself in this third perspective, I find it implausible that two people, always equidistant to myself, could be ageing at such dramatically different rates. Similarly, consider the graphics at 0:53 to depict time slowing down for a moving clock. The inverse would also be true, from the top clocks perspective, the lower clock would be ticking slower. Then consider a third perspective 'C' where the top clock 'A' travels west-east at the same speed that the lower clock 'B' travels east-west. A and B would see each other ticking slower. But C would calculate A to be ticking at the same rate as B. Logically, it would seem, this is truly a profound 'paradox' - or these presentations are a little muddleheaded.

@Krokodil986

2 ай бұрын

​​@@bobpower9189 you are correct - the middle clock, C, will see both A (who is at rest with the Milky Way) and B (who is crossing the Milky Way) as aging both slower than C and at the same rate as each other, as they are moving away from C at equal but opposite velocities. As you pointed out near the bottom of your comment, this situation is 100% symmetric. *If A and B are in relative motion, A sees B slow and B sees A slow.* That is, until acceleration happens, or more specifically, until one of these observer assumes a distinct inertial frame, and abandons his initial inertial frame. Everyone would agree on who changed their inertial frame and he would be found to have aged less when all three observers meet up again. This is consistent with the time animation you provided a timestamp to. Try drawing out a spacetime diagram for this accelerating observer. Initially, in the first inertial state, the light bounces off between two lines parallel to the proper time. But when the proper time changes direction, the light suddenly starts bouncing off much less frequently than before. So when your three observers meet up again, we can assert that B accelerated the least (didn't accelerate at all), C accelerated a little bit (less than A) and A, who travelled at nearly c, accelerated the most. Hence A ages the least, C a bit more and B the most.

@bobpower9189

2 ай бұрын

@@Krokodil986The effects of acceleration breaking time symmetry seem credible enough, but I could not imagine putting the 'pedal to the metal' for a duration of half an hour could result in years of age disparity, as is often presented. Presumably, different rates of acceleration yield different results. Also, have you ever come across any explanation whereby the effects of deceleration cancel, to any extent, the effects of acceleration. Just a thought - I've never come across it. How would this configure in a spacetime diagram.

@Krokodil986

2 ай бұрын

@@bobpower9189 amazing question So rate of acceleration is how much you are accelerating per second, "jerk". The lower the jerk, the slower the change to the new inertial frame, but also the more time spent in acceleration. So I think it cancels out (to be honest I'm not too sure about this) Deceleration is the same as acceleration, but viewed from a different perspective. Imagine me walking along the street. I can start running. I think I'll be accelerating, right? Well someone who is already running will think I'm decelerating, because I'll be decreasing the relative velocity between me and that person. But for me I'm still accelerating - so the effects of acceleration and deceleration must be the same, time dilates. Put in other words, the direction of acceleration does not matter because the universe is fair - it treats all directions equally. In a spacetime diagram, deceleration may be shown as acceleration to the left instead of to the right. Directions are equal, the universe is fair so it doesn't matter. The only thing that may change is simultaneity lines may bunch up or spread out depending if you're accelerating toward or away from an observer onto his world line But the only meaning of this spreading or bunching is it changes from what point in time causal action propagating from this observer can reach you in your own "right now". I didn't explain this last point very well, if you don't get it I'll try to explain it better, let me know

@Krokodil986

2 ай бұрын

@@bobpower9189 I've done some digging around... also let's define two velocities u and f let's say u -> c And f -> -c If you go from v = u to v = f, even if your change in velocity is instantaneous, ie delta t = 0, the age disparity will still approach infinity. In fact the quicker you get the acceleration part over, the quicker your two two inertial frames will reach their maximum difference. The quicker this happens, the longer they will be maximally different from each other. And the age disparity comes from this difference. So the longer the difference exists for, the larger the age disparity. So rate of acceleration does play a small part, but what's more important is the difference between the two inertial frames - ie the difference in initial and final velocity, rather than the time spend in transition.

Your more then a teacher, you make our heads float in to physics ;) Enjoyed it so much!

Interesting video Mahesh. I don't fully understand all the reasoning but my question is regarding Roger Penrose claim on that photons do not experience time (on the contrary to other particles with mass). It seems an important point in his view on the theory of conformal cyclical cosmology. Thanks!

I would have liked to hear about these points with the added perspective of time invaraiablity, but I suppose that's another layer of complexity. Love your work, thanks for the knowledge!

An amazing video I keep saved in my watch later playlist on you tube is called “Frames of Reference” it’s from the 50s or around there lol it’s in black n white. It explains this concept as well. It blows my mind every time I watch it! Thanx. This video was spot on at explaining this concept

Amazing video Mahesh. The production values are going up too. Nice!

I like this explanation, however I think quantum physicists use light experiencing no time to mean that it has no ability to change its state. Like an electron can flip it's spin because it travels less than the speed of light, but a photon can't change its state. That's my limited understanding anyway.

I would love if you there was some way you could further expand on this. Assuming it's fully correct that C has no reference frame (it's perspective at rest), that's still challenging to think about because we see that there is a substantial delay for us when say transmitting data from the sun to the earth, taking like 8 minutes. It sure seems like those electro-magnetic radiation waves are evolving through space, rather than instantaneously teleporting onto whatever observation instrument we are using. So, would it be it still be fair to say something like "light evolves through space but not time?" Or, another way I want to ask is "Are photons subject to entropy, from emission to absorption"?

Man, my physics teacher is going to LOVE these videos. Thanks for explaining all of these things so well!!

The way You explaining things is just mind blowing. Keep up the good work.❤❤❤😊

This reminds me of what you were saying in that one video about why time dilates as the forces causing motion are slowed down by the increased time it takes photons to travel in transmitting those forces. I have to wonder: how would we see light moving away from us at all? It seems like we could never detect light until it is reflected back to us. Is it possible that the light is moving slowly from our reference frame until it bounces back and is moving faster than the speed of light on the way back, and averages over the 2 distances to c? Is there any inconsistency in that model vs one in which c is a constant from all reference frames?

Dude these topics are so interesting . This type of analysis and critical thinking should be tought in schools . I am a 10th grade student ( like just passed 10th ) , the schools are just reducing syllabus so children dont gent stress but due to this our society , and country will face stress after some years. But i am here accepting you as my teacher to gain knowledge and pass it to others for benefitting my society and country .

Fascinating, so even if time is massively dilated (compared to our standard day-to-day reference frame) the experience of it is the same. It's interesting that time can subjectively pass quickly or slowly in a cognitive sense when the physics itself is rigid.

When light goes from A to B, we can compute the spacetime interval and corresponding "proper time" - for a photon it will be zero and it will be a valid computation. This is enough to say that time doesn't tick for a photon, and thus it "doesn't experience time". And it's an idea with practical measurable consequences: particles moving at light speed must not change along the way, they must be "frozen in time". That's why we now think neutrinos must move a bit slower than light, as they do change during their travel.

@kriiistofel

3 ай бұрын

Photons also change, their wavelength gets longer as they travel through spacetime

@thedeemon

3 ай бұрын

@@kriiistofel Not in special relativity ;) In GR yes, but there the topic gets more nuanced.

@kylelochlann5053

3 ай бұрын

No, the proper time for a photon is not zero - it's undefined.

@kylelochlann5053

3 ай бұрын

@@kriiistofel No, it is impossible for a photon to change, or have any intrinsic frequency/wavelength.

@kylelochlann5053

3 ай бұрын

@@thedeemon No, there is no distinction between SR and GR (SR is simply describes the ground state gravitational field).

But! If I am travelling arbitrarily close to c (don't ask relative to what!) then whilst my proper time will flow normally at 1s per second, space in my direction of travel will appear to contracted to virtually zero so I could travel from one side of the universe to the other in arbitrarily close to 0s (proper time). In that sense I would experience almost no time - coordinate time. Is that correct?

@kylelochlann5053

3 ай бұрын

Yes, because you traveled a short distance.

I have a doubt (not on this topic) : WHY DOES RESISTANCE DECREASE WITH INCREASE IN AREA? it may be a silly question, but how? when we increase area, the atoms are also more right? then resistance must remain same

@otaku-chan4888

Ай бұрын

my intuitive (disclaimer: I'm not a physicist or electrician) answer to this is: most of matter _is free space._ With an increase in area (and hence increase in the region where matter exists to provide resistance) there are more atoms but a LOT more free space as well. You'll understand it easier this way: imagine there's a tube with the free area of an atom inside. If there's atoms inside the tube's hole, the hole is blocked- except for the bit of space between the nucleus and the electron orbits. (assume) 40% of the 'stuff' inside can provide resistance. Now imagine the space increases to have a free area of two atoms inside the tube. Sure, there's one more atom- but twice the amount of free space. 80% out of 200% provides resistance, but a whopping 120% of 200% doesn't. Percentage wise nothing much's changed, but there's a lot more room for the same probability of resistance to _not_ play out.

Could this have any relation to the odd behavior photons present in QM? I mean, if there's no simultaneous POV for the light, at least in the regular sense, could it be why no two photons would be absorbed by an atom? So, in order to the photoelectric effect to happens, the same photon would have to be beyond a specific threshold (i.e. above a specif frequency), rigth? This is an honnest question, I'm really trying to understand these topics.

You have an amazing ability to clarify complex topics. Salut!

Hey Mahesh, nice one. Question: you explained moving photon clock slowing down in motion. Dioes the same hold true with a normal wrist watch and if so how?

Great video, Mahesh! This question has been on my mind lately and I've been trying to figure it out. You explained it perfectly! ...BTW, factuality is pronounced fac-tu-ality (you're saying "faculty" in the sponsor ad). Otherwise, your English is great.

Naturally, inside a reference frame, the speed of light remains c, regardless the reference frame's speed in relation to any other reference frame. The speed of light is actually the speed of causality. Inside any reference frame, it is constant. If we sit inside a space ship that travels very fast, approaching c, we still experience everything inside the space ship as normal. The issue is the relationship with other reference frames that are not traveling that fast. The imaginary photon that is bouncing up and down the cart, is indeed perceived as traveling at c inside that cart, constituting a reference frame. But, if we could somehow register that photon's movement from outside the cart, standing still, events inside the cart would seem to freeze. An imaginary particle that was moving at the speed of light inside the cart could not be perceived on one spot, moving laterally "up" and "down" with regard to the non-moving observer. That movement would be extended along the vector of the cart's trajectory. It's Special Relativity's space contraction that does the trick here. If the cart was moving very fast, approaching c, the imaginary particle at the speed of c inside the cart would actually not traverse the same distance anymore, as it would at a low speed. It's forced to traverse a much larger distance, as seen from the outside observer, whereas the inside observer in the cart still perceives the particle to move at c. This is exactly the core concept of Special Relativity. What an inside observer sees , while moving very fast, is not the same as what an outside observer sees, when standing still. So, light that travels through the Universe experiences space contraction so that all of Space becomes contracted into one point. Time dilation is stating the same mechanism here: to traverse a point does not take any time at all. A hypothetical space ship that approaches the speed of light is seeing the Universe as contracted into almost one point, a distance that takes almost no time to traverse. And that while inside the space ship, light still travels at the speed of c, without any contradiction.

Great & thought provoking video. However, one of the major problems I have with SOME scientific "conclusions" is the unprovable "fact". For example; if we cannot experience light's perspective, then we cannot say that it does or does not experience time. But on the other hand, special relativity is only relevant INSIDE of time & depends on the perspective of two or more subjects. Therefore, if we cannot use light as a subject in special relativity, then it is more likely that light does NOT experience time, and we must use quantum principles to determine its nature. ***I LOVE YOUR CHANNEL!*** Keep up the great content.

@narfwhals7843

2 ай бұрын

Using quantum principles doesn't change anything. Quantum Field Theory is based on special relativity.

So in that case, when you were talking about time dialation ..what is your reference plane..so in that case also if we consider the moving cart as the reference frame, then the time will be “proper time” right..?

Wow... i have seen many videos but no one explained like you did...hats off

you mate are fantastic at explaining things that I have had difficulty with over the years understanding

That is the best graphic explaining the relativity. I love your enthusiasm. I’m going to be checking out more. With metta, JTI

Your explanations and animations are fantastic. Best I've ever seen.

Nice explanation. I'm curious to see how light frame is for 2 photon going in same or opposite direction tho. Thanks nice job as usualy.

@thedeemon

3 ай бұрын

As v approaches c, length contraction makes all distances in the travel direction shorter and shorter, and with limit v=c they all turn to 0, space "collapses" into a 2D plane, so in this imaginary "frame" (which is formally invalid) two photons don't move anywhere at all, as there is no distance for them to move anywhere (and time doesn't tick too).

@dan_iversaire

3 ай бұрын

@@thedeemon thank you for the detailled answer, very interesting! This help a lot to understand

In the first animation, it was mentioned that length contraction was not included. What would it have looked like with length contraction? And mahesh can you please do a video on Lorentz transformation and the Lorentz equations derivations, as well as a video about how length contraction works? Love your videos

@juliavixen176

3 ай бұрын

The light would be length contracted to zero length along the direction of motion, but... this is still a nonsensical answer because the question is meaningless (see: video). I guess in a certain sense, you're going to be describing the 2D (space-like) surface of an expanding sphere of light... tracking a particular impulse wavefront. From the light's own perspective, it will "see" nothing behind it, because any light from behind it will never catch up. And due to the abaration of light, all light coming from any angle, will be concentrated into an Infitesimal point directly ahead... which is also kinda meaningless and not 2D like you might expect from the entire universe also being length contracted to zero length.... but it gets worse, because inbound light will be infinitely blue-shifted, which is extremely nonsensical. So light takes zero time to travel zero distance, and I will only see an infinitely energetic point directly ahead of itself, zero distance in front of it... the emission and absorption events occur at the same time and place from light's perspective. So.. in a certain sense, when you look at the sun, your eyes are touching the surface of the sun, from light's perspective. But also, this is a misleading way to describe momentum transfer through the EM field...

@juliavixen176

3 ай бұрын

Oh yeah, Eigenchris has a really good series of videos going over all the math for both Special and General Relativity (including Tensor Calculus).

Your channel is incredible. I really cant wait to see you at 1 million subscribers. I have little doubt.

Agree with all you're saying Mahesh and you have a great way of saying it. Maybe you could have added that for a Traveller, travelling at almost the speed of light, although his internal clock is ticking at 1 s per second, the rest of the universe would seem like aging billions of years in an instant...that is if he could see it...Even more mind blowing to me :)

Or, as we say in mathematics: You can't divide by zero, but you can take the limit as the denominator approaches zero. At v = c, you're literally dividing by 0 to get quantities like γ, length contraction, time dilation etc. So those quantities are no longer well-defined. This is where the next genius wonders what happens if one were to allow division by zero, and thereby revolutionizes math as we know it.

Thank you, Mahesh! I wanted to ask - do you think you’d talk about cases where an object is traveling at ~0.99*c in a vacuum, in parellel with a photon traveling at c’ in a denser medium’? E.g., if c’

@kylelochlann5053

3 ай бұрын

The wavefront would move slower than c in every frame.

sir i have a doubt on another topic. if i throw a ball in interstellar space, the ball goanna gives me an opposite force and i will accelerate backward. but i don't understand what force is going to affect me. if i accelerate the ball the ball come along to my hand and if i lose my hand there is no force acting by the ball on my hand. the ball just stays constant velocity. And i just understand what force going to make me accelerate backwards. will you please respond??

@Littleprinceleon

3 ай бұрын

Are you (and the ball in your hand) moving? relative to what? Is there absolute motion? What is a force anyway? Further things to consider... Good luck 🤞 with finding the answers

@adhithyakrishna00001

3 ай бұрын

@@Littleprinceleon if i am in space, and there is no force acting on me. if i throw a ball using my muscular force , the ball will move [gain uniform velocity after i loose the ball from my hand ] w.r.t my frame of reference right. then according to newtons 3rd law there will be equal negative force acting on me . but i cant find out what is that force that affect on me ????😔

@narfwhals7843

3 ай бұрын

​@adhithyakrishna00001 the force is coming from your muscles. Imagined the ball was the earth. The situation is essentially the same except that instead of pushing the ball you are pushing yourself simply because the ball has more mass than you. The same force is acting and it's coming from your muscles.

@adhithyakrishna00001

2 ай бұрын

@@narfwhals7843 that's helped . thank you 😊

@EJ-yy3wl

2 ай бұрын

Your muscles creates the force against the mass of the ball. Since your mass is greater than the mass of the ball, it will experience more acceleration than you. If this were not the case, then an astronaut on a spacewalk could push the space station out of orbit. But they can't because the space station's mass is so much greater than their's.

the funny thing about the 1 light year cube of space is you wouldnt know where that photon was until you observed it, you would have a general idea, sound familiar? the old uncertainty principal is just that, you have no idea where something is until its information transmits to the receiver, we need to either poke something or have it poke us.. you wouldnt see it until its light propagated out, so that photon would appear dark.. Like you have 3 things, that 1 light year cube of empty space, a photon and the ability control time, place the photon in the box and stand outside the box, for all observers its dark, no one can see it but its there, you wont see it for up to half a year until its energy ripples its way to you, but hit play on the remote and space unifies to spacetime, the photon disappears from its source, sends its information onto space and it ripples away in the dimension of time. You wont know if its worked for up to half a year as an outside observer, and inside you would just see a flash of light as it passes by you, but it goes in every direction at the same speed unless it is influenced by something else, another kind of energy field, and in an "empty" box there is nothing other than space for it to ripple time with its remnant the photon died the moment it transmitted its energy, it never moves and it never really hits the source with anything other than a ripple in spacetime which our eyes process as light, so yeah what we see is actually just a burp in space as time sends it flying our way, the spacetime excites our eyes into processing an image, but its all just illusions of the past, everything we see and touch based on that limited perspective, even typing now im not feeling the keys, im feeling the electromagnetic fields of energy push my fields away, things arent solid they have energy barriers and fields holding things together on the smallest of scales When i look at something that i consider yellow, its actually rejecting that colour, to it, it would say it is every colour but yellow. Our perspective and understanding of things makes it really hard to see the big picture, but its all fields, a field of space wrapped up with time and packets of energy in stable or non stable forms, everything is just trying its best to exist for as long as it can and transmit its information into the void. Hoping something hears it

We are the frame of reference- the observer? Every time I hear something is meaningless to ask regarding cosmology or physics, I realize it It’s probably one of the most meaningful questions you can actually ask.

"I don't know" is a simpler answer I noticed in the animation that a part of the light circle still moved in the Y axe, perpendiculary to the path of the car while it was moving at C, wich is a bit logical... at that speed, fire a laser beam in front of you, you should see no beam. Fire it perpendiculary to your movement, you should see a straight ray of light. Why ? Because in the X axe the car is already at C, but in the Y axe it is not. Therefore, according to this observation/deduction, we could suppose that in the frame of reference of light, time "SHOULD" tik normaly. p.s : Einstein says, speed of light is the same in all INERTIALS frames, not in ALL reference frames... therefore, light not being an inertial frame but rather an absolute one, I don't really see a problem for it to be equal to zero, in its own reference frame.

I woke up saw your video and now I am dead😂😂 I can see light reference frame now😂😂 By the way awesome video ❤❤

@Mahesh_Shenoy

3 ай бұрын

You are the chosen one!

@08scout

3 ай бұрын

Thanks Einstein 💓

I think the argument is that because all photons tend to have a finite life if we pretend the photon is a normal object with mass that is approaching the speed of light, its experienced lifespan (time between its creation and absorption) will approach 0. However a photon that flies away to infinity and never interacts with another object cannot be said to not experience time in the way most people mean.

I would have thought light doesn't experience time only now I understand my mistake in putting myself in lights shoes (as those shoes are never stationary in any reference frame so you can't do that). What does a beam of light see if it looks over at another beam of light? Another question we can't answer. At least, not yet. Infinities and 0s. usually indicate something incomplete in the theory and we have more to learn. And that's usually a good thing. Enlightening video.

1. I think "light does not experience time" is a good description of "proper time for light is meaningless". 2. There is still an affine parameter along any light-like geodesic, but there is no way to fix its unit (as we have fixed the second for proper time). 3. When gravitational lensing happens, you can connect two events by a family of time-like curves approaching a light-like curve in limit. In that case, proper time measured along those curves goes to zero as the curves approach the light. 4. Existence of singularities is proven using light-like geodesics, so even without proper time, the light can experience "something". 5. Not to mention interference and various electromagnetic interactions light can participate in.

How's the music called in the animation?

I love your channel. Thank-you so much for all your hard work and brilliant explanations. Light doesn't experience time when it's measured by an outside observer. When the car is moving at c it doesn't move in the car, correct. But you don't mention that the light experiencing time only appears that way to an outside observer because of time dilation and length contraction, not to any of the occupants in the car. They would experience time at a normal pace. It is the outside observer that sees things differently. Example. I proposed back in 2004 that the JWST would not be able to look back in time because light traveling at c to an outside observer would not experience time or distance. The telescope is always located inside it's EM field of "potential light information" coming from distant galaxies. Thus when an outside observer like the telescope measures their light it happens instantly, regardless of the distance because the photons in the galaxy's EM field are all entangled. To an outside observer like a telescope, the light information happens instantly, regardless of the distance. Meaning we should see the distant galaxy as it looks today, in our relative time, not how it looked in the past when the light left the galaxy. So, I proposed the JWST would find old, fully grown galaxies as far as the telescope is able to see, even further than 14 billion light years away. Sure enough, when the first CEERS survey was released guess what astronomers found? They found old, fully grown galaxies as far as the telescope was able to see, just as I suspected. Light inside the EM field becomes a potential in our slow mass time until measured. Then because of entanglement the light information is conveyed instantly because it's entangled in one EM field. It's as if the light information remains in limbo, outside our reference frame of space, distance, mass and time up until it's measured, observed or strikes something. It is the observer who plucks the potential light information from the EM field and into our space time. Light traveling at c to an outside observer doesn't experience time or distance. That's why the JWST is able to see old fully mature galaxies as far as it's able to see. It's not because of multiple universe, not because the constants in nature changed over time, not because of tired light, not because of a dark matter big bang occurring millions of years after the first big bang, not because of cyclical universes. It all boils down to light can't experience time or distance when traveling at c.

@kylelochlann5053

3 ай бұрын

No, you missed the entire point of the video. Technically, the null structure of the gravitational field is observer independent (give a space-time event, P, all events at light-like separation is independent of any choice of time-like curve). There cannot be time for light simply because light is always restricted to the null structure (e.g. the null structure in SR is the light cone).

I was ready to angrily type away in the comment section, defending the idea that light experiences no time. But you made such a compelling argument, now I have nothing to say but thank you for the informative video. 😂

@enriquea.fonolla4495

2 ай бұрын

most other videos say it doesnt...