Why the Speed of Light is the Ultimate Speed Limit | The Physics of the Universe 

UFO= not exactly name,g because they can out gravity, right call space ship travel speed of light, the pilot is human, allein or et,,,,,100% handsome and pretty ,100% kindly

I don't think we know. But I think his videos on Fermilab will give more advanced ideas at least than this video. edit:I added my speculation in another comment

Let's don't see it as speed of light, or even as a limit, it isn't a limit, it is just a speed that we humans have calculated it to be relative to our understanding. But what it really is simple - The more you move in space, the less you move in time, the more mass you have the less you move in space with the same energy, and light don't have any mass, so it doesn't move through time but is moving through space infinitely, you see, relative to a particle of light, it hasn't aged a day since the big bang. Think of it like, you can move through space and time, but only when the sum of it is 1. So maybe you can move through space 0.4 and through time 0.6 but never more than that, the Universe will limit you from doing so, if you reach the speed of light time slows down so you only move so much, so that casaulty is maintained.

@@crewrangergaming9582 I understand all that. My complaint is the clickbait nature of the title. It didn’t even address it’s own question.

I don't think he knows why.

@@joebloggs396 Of course we know, though I'm confident Don Lincoln doesn't know.

Fundamental constant...we don't know for many...but faster you move thru space slower time is going for you (its proven, with observations everywhere) and at 100% speed of light time would stop for you, literally. Yes ik what ou have in mind even if you know relativity but it seems its physical constant like many others and we simoly don't kbow why, how it just works-like quantum mechanics, we don't know why and how we just know it works and all technology since 50s is at one point based in QM

@@gasperstarina9837 why does time slow down ?

That's great explanation, for a six year old.

Good explanation. It doesn't seem to prove the speed of light is constant for all observers.

What medium? There is no medium.

fancy words never convinced me .

@@colleendougherty4475do the predictions of: Time dilation Length contraction Antimatter Black holes Non static universe Frame dragging Shapiro delay Convince you?

@@DrDeuteron No.

I knew you were alive!

@@Rasta426 How did you know?

@@AmyWinehouse.914 when is youre next single coming out?

@@Rasta426 The day after you become funny.

Exactly. I suppose nobody can answer the question posited by the title. Unclear why it is titled wrong given how smart the content seems to be. Clickbait, I suppose?

Das ist genau die Hilflosigkeit, die versucht, eine Behauptung so lange mit immer neuen Thesen zu untermauern, bis sie gesichert scheint.

I'm an average person and I try to understand what my pea brain allows me to. I find all things about the universe quite interesting... I am not smart enough to understand even a small percentage but I do try

What if there is simply a speed limit in our universe for light or anything and that is what we see in the experiment and not that light is the same speed for all observers?

@@jamesh9174 Boundary not limit and yes space has a time dilation ratio compared to us of 9*10^70 seconds for our one second observed.

For anyone having trouble understanding why the speed of light even exists read the following: No matter which theory of relativity we use (The two most famous ones are Galilean and Einstein’s relativity). We always need a way to preserve causality That means -> that we need a way to be able to put EVENTS in causal order (we need to know which event caused which other event and at what order.) To do that, we always need to have some quantity that is absolute. For Galilean and Einstein’s relativity, those quantities are a certain specific speeds. For Galilean relativity, our speed through time is that quantity. Its absolute. Which means that is 1) invariant and 2) constant. 1) Invariant means, that the value of the speed doesn’t depend on any observer or their own speeds. 2) Constant means that its value can’t change. It’s a set value and there is nothing we can do to change that. For Galilean relativity, that quantity - our speed through time - is therefore constant and invariant and equal to 1s/s. Which means, that every object is aging at 1 second per second no matter who is observing or what their speeds are. That also means that there is nothing you can do, to travel in time faster than 1 second every second! (That by the way, shows us that Galilean spacetime is Euclidean). NOW! For Einstein’s relativity that has changed. An objects speed through time is not absolute anymore, and its not constant and its not invariant. We know this - because we have seen that our spacetime is not Euclidean as we once thought. Its hyperbolic and its depicted by the Minkowski metric. So the nature of spacetime - being hyperbolic - makes our speed through time to not be constant and or invariant as we once thought! So now we need a new relativity, Einstien’s relativity, which does 2 things. 1) Preserves causality. And 2) has speeds through time that are not constant or invariant anymore. So how can we do that? Well, Einstein comes up with a new quantity that’s absolute that does those 2 things. That new quantity is our speed through spacetime. And for Einstein - its absolute. Which means that its 1) constant 2) invariant and equal to 1ls/s (one light-second per second). That means, that every object moves through spacetime at the speed of 1ls/s which is the speed of light So… An object can move in spacetime with ONLY one speed. The speed of light. Me, you and everything is right now, moving in spacetime AT the speed of light relative to nothing. We don’t need relativity to say that, because the speed of light ISNT relative - its absolute, and its equal to 1ls/s. So now, just like you couldn't age faster than 1second per second in Galilean relativity. Here you can't travel in spacetime faster than 1 lightsecond per second. Just like it didn't make sense for an object to age faster in Galilean relativity, here again its meaningless to travel faster than 1ls/s in spacetime. Why? Well, lets take a look what means to travel at a certain speed in space. Since our speed in spacetime is the speed of light... That speed in spacetime is always the combination of our speed through space and our speed through time. If our speed through space is C then our speed through time is 0. And if our speed through time is C then our speed through space is 0. The 1st where our speed through space is C, is the case for light. All of its speed in spacetime is allocated in just space, and time doesn't pass for it. The 2nd case, where all our speed is in time, is freefall! Because that's what freefall is! To stay stationary in space and age at the speed of light. Anything in between is the speeds that everyday objects have. Some of it will be in space some of it will be in time but when combined they will give us C as a net result. That means! That the speed of light IS effectively infinity. At least for a hyperbolic geometry that is. Becuase when you travel close to the speed of light, time for you passes very slowly (your speed in time is very small). Which means that you can reach very far away distances withought time passing for you... So you can reach a 1light year away star in just 1 week because you didn't experince time. If you go closer to the speed of light in space still - then you can reach that 1 lightyear way star in 1 day! Closer? 1 hour... Closer? 1 second... Etc... So when you go AT exactly the speed of light in space, your speed in time is zero. So you can reach any position in space infinitely fast (in zero time). (For you at least...). So to answer you initial question: You can't go faster than C, because you can't go faster than infinity.

If you listen you can hear the answer to that "the speed of light is the same " if it wasn't you and I would see light differently

Oop wrong spot sorry about that

What matters is the ‘size’ of the peak or trough. The brightness is dependent on the size squared. So A trough is the same as a peak in size - and brightness - just out of phase. The dark patch is where a peak is cancelled out by a trough, giving a size of zero.

@@-_Nuke_- Do you need hyperbolic geometry for the speed of light being constant as in special relativity?

Thank you, Maur! We'll share your comments with the professor!

The geometry of the gravitational field requires that the electron measures the speed of light to be c. There is no way to render a different result consistent with the results we obtain in the lab.

@@kylelochlann5053 ok, but I don't see that in the line of reasoning in this video. I'm just saying that from presented reasoning and experiments we cannot say that the source of light, traveling in the same direction as that light, perceive it's velocity as c. I would really like to see explanation on that. The fact that emittion of light is not the same as throwing a ball from the train is far more obvious.

What if there is simply a speed limit in our universe for light or anything and that is what we see in the experiment and not that light is the same speed for all observers?

@@darkososyt Correct, the video presumes a basic understanding of relativity, which isn't obvious to anyone who has not studied it sufficiently. The constancy of the speed of light is owed to the local structure of the gravitational field and originally taken as a postulate by Einstein on the assumption that the electromagnetic equations of Maxwell are correct. Nowadays the local constancy of the speed of light is taken as a consequence of the spacetime interval being null for light, i.e. ds=0.

@@kylelochlann5053 that's very interesting... For some reason I'm trying to understand this, and the more I watch videos on the subject the more questions I have :) Anyway, as much as appreciate people that make these kind of videos, seems to me that there's always something missing in line of reasoning. And often there is a mix of things like "light between mirrors on a train" and some math equation which already have many other thing hidden in it. I'm a mathematician by education, so to me, if we assume something and then make equations that are the consequence of those assumptions, even if the equations proves right, that doesn't mean that our assumptions are true. Logically, from false assumptions you can deduce right conclusions. So I'm trying to learn what exactly are facts and what are assumptions, or consequences of assumptions. I mean, if we knew everything, there would be no need to question anything...

It’s because mass grows and becomes infinite at the speed of light. So if you shot a BB gun at the Earth at the speed of light it would destroy Earth according to Einstein and that kid from “A Christmas Story” who stuck his tongue to the flag pole. I think they both would agree. Hopefully without swearing. Thanks 🙏🏻 I hope this helped you out, but I thought it did say why, so I don’t know 🤷‍♀️ If you have any more questions I am ready. Thanks 🙏🏻

The speed of light is completely a function of the medium it traversed. Specifically as Maxwell showed in 1860 = 1/(sqrtf(u0)**2 * sqrtf (e0)**2). With u0 magnetic permeability and e0 electrical permittivity. These last two may vary depending upon medium eg free space supports faster speed than water.

@@utee72 so say the medium is the quantum realm then light could have a different speed limit there🤔🤷🏽‍♂️

@@BlackPDigitalMedia No the "realm" is our universe's free space and thus the speed of light is constant there. Quantum objects in our universe cannot defeat this restriction. Note again that different "media" eg water will transmit light slower as they have different u0 and e0.

@@spiralsun1 In EM radiation what is moving through space? If it is the photon, it have the energy h when it is emitted by an electron. Then the mass of a photon is h/c^2. If the photon is moving at the speed c then too it's mass have to increase towaards infinity. But it is not happening. It remains constant. Why?

No, in the frame of the electron the photon still moves at c. Of course, the explanation of Don Lincoln is wrong, as usual.

@@kylelochlann5053 Also in the frame of the electron, the electron and photon do not arrive simultaneously. Relativity of simultaneity.

From my probably messed up understanding, it must be due to time dilation at the speed of light from the electron perspective vs the outsider perspective with no time dilation.v

Yes, there is a limit.

Thank you for your nice feedback.

What if there is simply a speed limit in our universe for light or anything and that is what we see in the experiment and not that light is the same speed for all observers?

@@jamesh9174 That is in fact true. Light travels at the maximum speed that the universe will allow, and so do gravitational waves.

We can never know the one way speed of light, no matter what the method is. Let along with the method mentioned here. I feel you, bro.

We did both in Physics lab. as well as the Cavendish experiment.

Why? They aren't using any energy to travel. Surely they are set in motion when they are released from matter, then maintain that motion until they collide with something.

@@AORD72 Wouldn't they have collided with lots of stuff if they've travelled 7.5 billion light years? 7.5 billion light years is 300,000,000 x 60seconds x 60 minutes x 365 days x 7,500,000,000. That's a lot of metres (something with approx 25 zeros after it; more than a billion quadrillion metres!) Wouldn't there be friction involved?

Well said.

What if there is simply a speed limit in our universe for light or anything and that is what we see in the experiment and not that light is the same speed for all observers?

@@jamesh9174 Well, there is - but then we would measure different values for the speed of light from different frames of reference - and we don't (!!!), which is very counter intuitive and weird. So something else "has to give" so to speak for that to be true - namely the concept of a universal time and fixed spatial dimensions. They (now) depend on the frames of reference of the observers. From the frame of reference of the photon it reaches our eyes INSTANTANEOUSLY from the light source, since no time is passing for it, as the spatial dimension along its direction of "travel" is contracted to zero length ( v = c, in the Lorentz factors ) - or its "presence" ( the projection of its length dimension ) is reduced to zero, as I prefer to see it 😉

@@Bjowolf2 I like this "something has to give"! This is exactly how I have thought about these matters. Nothing shrinks or expands but the measurement of these parameters. It is not necessary to think of a an object actually shrinking in the direction of motion, only that the measurement of such changes with relative velocity. Of course, my view here raises the question of whatever "actually" means in these contexts.

@@daviddeutsch3392 Thank you 🤗

It is our pleasure!

What if there is simply a speed limit in our universe for light or anything and that is what we see in the experiment and not that light is the same speed for all observers?

Dr. Don Lincoln has his own yt channel, in case you are interested in more of what he has to say.

Nothing would happen and time (and all else) would be normal for you. You would be moving traveling a negative length and this doesn't make physical sense, and you'd be able to send messages to yourself about events that haven't happened yet. So, it's not so much a problem as that it is meaningless.

Once you go faster than light, there are frames where you are teleporting instantly (to outside observers), and more in which you are going backwards in time. Just say no.

@@baberoot1998 work on people? I was just describing my point of view.

Why do you believe that? And why might the nice man in the video believe it?

@@matthewphilip1977 Well the short answer is I don't know, yet. Another thing that makes me wonder is photos traveling at the speed of light apparently do not experience time. If I figure it out I'll let you know or you'll hear about it when I pick up my Nobel prize. 🤣

The Speed of Light (C) is constant because the Doppler Effect is altering Frequency (F) and Wave-length (WL) C = F x WL

@@terryrogers8965drop that photons don’t experience time. There are no reference frames for light, so it is meaningless, and adds no understanding.

@@robertvangeel3599 In any relativity calculation, you begin by assuming that "you" are stationary; you cannot travel at 99.99%, or 0.000000000000000000001%, of the speed of light. See 0:49 in this very video.

I advocate jail time for directors who do this. They would occupy cells near the people who do countdowns for everything.

What it tells us is that frequency and wavelength are not properties of light. They are consequences of the frame in which the light is observed. It really is that simple.

I think the distance to GRBs are taken from the galaxy in which they occur.

Thank you for your feedback, Peo.

Hello. If you and the beam of light were in a race over a very long distance would you be covering half of the distance that the beam was covering?

All propagating modes are transverse, but it works for near field effects too, it’s just that studying those fields only adds difficulties, not elucidation

Because there are no tachyons, and you don’t need to know that to describe experiment .

@@DrDeuteron I guess there was no Higgs Boson either...until there was. Be patient.

You start up saying that they all flash simultaneously. Then each traveler will only see one flash from each point but at different times. The travelers speed only matter to make it possible to see any difference in when the light flashes arrive and possibly also the color of the flashes.

Is this a joke?

You seem to be describing what different observers see and then asking how they can see different things. Relativity accepts that events that look simultaneous to one observer need not look simultaneous to another. Also, you could do this same experiment with Newtonian physics, or so it with sound. Or BBs.

@@vesuvandoppelganger You started up by saying that they flash simultaneously and by that I understand that if seen from a point with equal distance to all three points they would be seen as flashing simultaneously. Any person at anywhere else around will see the flashes when they come to them. Time = c/distance. None of them will see more than one flash from each point. It is my belief that if an electromagnetic impulse (in this case photons) is emitted from a point in the universe this point is fixed meaning it doesn't move even though it is emitted from a moving object. Any movement can be noticed in the frequency of the signal but not the speed. An example it speed radar. I believe that you can't tell any difference if you check the speed of a house if tested from a moving car or if you are standing at the house and testing the speed of the car. Another example is the redshift from far away stars that supposedly move away from us. Some people say that electromagnetic waves (including light) are moving in some quantum field. My question is: Isn't that just another name for the eather that has been disproved to exist? I believe electromagnetic pulses (photons) are energy pulses or quanta's that can exist on their own just like a small space ship. They are pulsating giving them the appearances of waves. This in my opinion would explain the double slid performance. That free electrons supposedly also show up as both particles and waves in a double slid setup would indicate that they are also wavy particles. They are much bigger and have gained mass and as such can be accelerated but also move at much lower speed.

The most distant thing we can see in EM is the CMB, and that will always be the case. The stars we a losing now are made from that stuff (plus or minus some distance, idk what that is), so there’s kind of a time lag at play

The constancy of the local speed of light for all inertial observers is a consequence of the causal structure of the gravitational field and not something that can be covered in this video.

@@kylelochlann5053 OK, so shall I infer from your comment that this video does not show that the speed of light is same for all observers?

@@hanumantd That's right, it doesn't. and I disliked it for the clickbait title. Based on his other videos, I'm confident Don Lincoln never took a course in relativity and doesn't know the answer. EDIT: Lincoln would have used relativity in his course work and professionally. In grad school the high energy group (the particle physics kids) could often calculate things in relativity quicker than we could, but they had no idea why anything was the way it was (and often had hilarious explanations of what they thought the physics was about).

Yes! I wondered the same. It is my understanding, that we can only measure the "two-way" speed of light. This video seems to suggest different, that the "one-way" speed of light can also be measured. I believe that is in error. Great observation. 👍

The standard method is Einstein synchronization.

You just use the NIST signal.

Ikr, big fail for les SI units. Really, though sqrt(10) giga meter per second might be even better.

To the stationary observer it might travel at .1 mph less than c. To you, 100mph because of length contraction and time dilation.

@@AMC2283 To you, 100mph; to the stationary observer it might travel at .1 mph less than c because of length contraction and time dilation.

"It drives me crazy when people say never" reffering to us never being able to reach the speed of light or go beyond it! I too had the same reaction when I first learned special and general relativity. In this text bellow I will explain why this is indeed impossible! Lets start: ------------------------------------------------------------------------------------------------------------------------------------------------------------------ No matter which theory of relativity we use (The two most famous ones are Galilean and Einstein’s relativity). We always need a way to *preserve causality* That means -> that we need a way to be able to put EVENTS in causal order (we need to know which event caused which other event and at what order.) To do that, we always need to have some quantity that is absolute. For Galilean and Einstein’s relativity, those quantities are a certain specific speeds. For Galilean relativity, our speed through time is that quantity. Its absolute. Which means that is 1) invariant and 2) constant. 1) Invariant means, that the value of the speed doesn’t depend on any observer or their own speeds. 2) Constant means that its value can’t change. It’s a set value and there is nothing we can do to change that. For Galilean relativity, that quantity - our speed through time - is therefore constant and invariant and equal to 1s/s. Which means, that every object is aging at 1 second per second no matter who is observing or what their speeds are. That also means that there is nothing you can do, to travel in time faster than 1 second every second! (That by the way, shows us that Galilean spacetime is Euclidean). NOW! For Einstein’s relativity that has changed. An objects speed through time is not absolute anymore, and its not constant and its not invariant. We know this - because we have seen that our spacetime is not Euclidean as we once thought. Its hyperbolic and its depicted by the Minkowski metric. So the nature of spacetime - being hyperbolic - makes our speed through time to not be constant and or invariant as we once thought! So now we need a new relativity, Einstien’s relativity, which does 2 things. 1) Preserves causality. And 2) has speeds through time that are not constant or invariant anymore. So how can we do that? Well, Einstein comes up with a new quantity that’s absolute that does those 2 things. That new quantity is our speed through spacetime. And for Einstein - its absolute. Which means that its 1) constant 2) invariant and equal to 1ls/s (one light-second per second). *That means, that every object moves through spacetime at the speed of 1ls/s which is the speed of light* So… An object can move in spacetime with ONLY one speed. The speed of light. Me, you and everything is right now, moving in spacetime AT the speed of light relative to nothing. We don’t need relativity to say that, because the speed of light ISNT relative - its absolute, and its equal to 1ls/s. So now, just like you couldn't age faster than 1second per second in Galilean relativity. Here you can't travel in spacetime faster than 1 lightsecond per second. Just like it didn't make sense for an object to age faster in Galilean relativity, here again its meaningless to travel faster than 1ls/s in spacetime. Why? Well, lets take a look what means to travel at a certain speed in space. Since our speed in spacetime is the speed of light... That speed in spacetime is always the combination of our speed through space and our speed through time. If our speed through space is C then our speed through time is 0. And if our speed through time is C then our speed through space is 0. The 1st where our speed through space is C, is the case for light. All of its speed in spacetime is allocated in just space, and time doesn't pass for it. The 2nd case, where all our speed is in time, is freefall! Because that's what freefall is! To stay stationary in space and age at the speed of light. Anything in between is the speeds that everyday objects have. Some of it will be in space some of it will be in time but when combined they will give us C as a net result. That means! That the speed of light IS effectively infinity. At least for a hyperbolic geometry that is. Becuase when you travel close to the speed of light, time for you passes very slowly (your speed in time is very small). Which means that you can reach very far away distances withought time passing for you... So you can reach a 1light year away star in just 1 week because you didn't experince time. If you go closer to the speed of light in space still - then you can reach that 1 lightyear way star in 1 day! Closer? 1 hour... Closer? 1 second... Etc... So when you go AT exactly the speed of light in space, your speed in time is zero. So you can reach any position in space infinitely fast (in zero time). (For you at least...). So to answer you initial question: You can't go faster than C, because you can't go faster than infinity.

@@-_Nuke_- Trust me, I understand the theory behind the why. As Neil deGrasse Tyson put it, you can't undo what's already been proven. However, there is a lot we still don't understand about the universe. A vast chunk of the predicted mass and energy in the universe doesn't line up with what we see. What that means is for laureates to discuss and ponder as students earn their PhDs. So again, to stick to this notion that what we know is absolute is absurd. Far too many times a person has come along and upended our understanding of our world around us. FTL as we know it isn't possible. But there is sooo much we do not know...

@@Benson_aka_devils_advocate_88 If special relativity is supplanted by something in the same way that special relativity supplanted Newtonian mechanics, then sure. But you should also realize that a lot of the things people said we'd never do -- get to the moon, fly heavier than air craft, etc. -- were thought intractable engineering problems, not violations of established natural laws.

Hi Alberto, yes we do.