Why nothing can travel faster than the speed of light.

[@kellycommaroy]

Thank you. I tried to conceive it as a TED talk but didn't quite get there. The laughter was culled from several of those lectures.

[@animatorguy2]

That canned laughter was painful

[@Njderig]

I was wondering what they were laughin it. The jokes werent even funny

[@finn_underwood]

Njderig It's called polite laughter. Scientists and such giving speeches, or just anyone on any type of stage, really, is bound to be at least a bit nervous. Stage Fright. So, an audience showing their appreciation; though applause or laughter or whatnot can be a huge confidence booster and motivator. Even if it's just the littlest thing, it helps. besides, if you're in a 'boring' lecture hall, the smallest joke becomes much funnier, thus making it easier to laugh.

[@stuffandthings7146]

's a reading of a reddit post, not a ted talk

[@johannathorn6652]

He styled it like a lecture or Ted Talk, though, hence the laughter. It's perfectly in line with what he's trying to convey with this video.

[@peterdietrich8810]

I like how he threw out special relativity and then immediately talked about spacetime.

[@DangleBlampy]

that part made me cringe. its like he knew if he brought it up he would be wrong

[@DrProctorr]

I did get the sense you say you were intending to have in the video, especially with the "thank you" at the end. The only thing missing is the utter expression that the TED talkers have, as well as some slightly noticeable nervousness many of them have. Also, it was very "quiet" while a TED talker, in their excitement about their subject is prone to having to speak very loud, especially to keep those in the back engaged.

[@qwertyfingeryeah]

I actually think you nailed the TED talk effect! Granted, some laugh tracks were off, but aren't they always? :D

[@reeceagodwin]

Your Title, "nothing" can travel faster than the speed of light really? nothing must be really really fast then

[@WantEpicMusic]

You can never outrun entropy

[@thedoublessymbol]

Entropy consumes all...

[@PollexTheCat]

vacuum decay

[@isecream]

One word. Big Rigs: Over the Road, Under the Road, Around the Road Racing.

[@fissetis6427]

you are a genius

[@overlordghs1081]

holy fuck this has got to be the most convoluted explanation ever, please give the people who read or hear this a little bit of credit.

[@C4ssi4an0]

Hey Roy Kelly, where can I find his explanation about ''the arrow can never stretch or shrink''? He says he would ''save it for another time''.

[@graywolf7237]

Cassiano Barcellos it can never get wider or skinnier.

[@user-74652]

I didn't like the random laugh tracks here and there, but other than that, the original text was very interesting, and you read it rather well.

[@KingHalbatorix]

Random user #74652819 it's just like a TED talk

[@JOhnDoe-nl4wj]

The easy explanation: Acceleration requires energy. The energy needed to accelerate a moving object (or any piece of matter) is rising exponentially with it's speed. Simply accelerate anything close to the speed of light would require more energy then available. Acceleration past the speed of light would require even more energy then what is available in the observable universe.

[@christopherh760]

One thing to add: You may have heard that traveling faster than the speed of light would theoretically cause you to travel back in time. This is best understood with the two-axis graph he was talking about. When we start traveling less through time and more two space, the arrow which was pointing up in the future-ward direction starts pointing less future-ward and more forward. The arrow is basically rotating clockwise (or counterclockwise, depending on how you visualize the graph. Once it points horizontally, you are theoretically traveling at maximum speed through space but not traveling through time. Since the arrow cannot stretch, the only way to attempt to travel faster would be continue to rotate the arrow clockwise, right? But of course, if you do that, you aren't really traveling faster than light. You are however traveling through time again, but the arrow is now pointed toward the past-ward direction instead of the future-ward, so you're going back in time. Thus, if you hear the misconception that going faster than light turns back time, just know that you aren't really going faster than light, just turning the theoretical arrow past the speed axis so it starts doing the opposite: as it rotates your space-speed decreases and your time-speed increases (into the past). What I find fascinating about this model of the universe is that it shows that space and time are not just related, but that they are possibly the same thing. Just thought I might share this.

[@ChaseSkylark99]

And that 'same thing' of space and time is what has received the name 'spacetime'. ^^

[@toasega]

I always took it as "You need energy to move mass, but the faster you move, the more energy you need", like how you physically can't run faster than what is humanly possible because you lack the energy and the strength to pull it off. Even adrenaline only keeps you running LONGER, but not necessarily faster. In the same way, in order to have a space ship travel faster than light, the faster the ship moved, the more energy you would need to surpass the speed you were already traveling, like how you can hear your car straining more and more as you pass 60 MPH, 80 MPH, 120 MPH, and so on. There's only so much power you can generate to go a certain amount of speed, and getting not only TO light speed, but BEYOND it, requires more energy than any known science or technology can give us. That's why people talk about things like wormholes, as they kind of "cheat" the system by bending space time; it would be like crossing the street, but instead of walking the whole way, you just push both sides of the street together and step onto the other side. But the problem with that is that you'd need something on both sides to create such a thing; how are you going to push the OTHER side of the street towards you without physically being there to push it?

[@dmaster254]

says he hates the term space-time. then uses it repeatedly

[@stokesa3122]

ROY I LOVE YOU PLEASE COME BACK

[@0xCAFEF00D]

So in the end he didn't explain at all. In my opinion almost any explanation is better than one that dodges the question.

[@saltysaty8686]

6:45 through the end he said that nothing can be straighter than straight.... by horizontal he is talking about the maximum speed in the universe which is light... he said it and if you dont get it just read......

[@0xCAFEF00D]

saty chap But he introduced the arrow concept without explaining why four-velocity can't change really. It's skipping the explanation for why the arrow cannot stretch essentially. So the question is unanswered. He explained four-velocity quite well but there's no explanation to the question. He simply states that the arrow can't stretch. Which is basically "you can't move faster than the speed of light". It's not intuitive either because in our 3D universe velocity changes. Then he states "Now there are some mysteries here. Why can four-velocity vectors only rotate and never stretch or shrink? [...] But I've rambled on quite enough here,". So he even admits he hasn't actually answered the question and then he appeals to the reader to accept that that's the way it is. I can understand the idea that you might not be able to explain complicated things in a limited amount of space. But I feel that it's important to make the distinction that this isn't a complete answer. It's just an explanation of what four-velocity is as a concept (and how it relates to the speed of light to some degree). I see how my comment may have come off as insulting (, maybe). Claiming that he's doing a disservice by "dodging the question". And I hold that I do think he does a disservice by posting this as an answer to "Why exactly can nothing go faster than the speed of light?". But that doesn't mean the post is useless obviously. Give it a different label and it's fine. Maybe I'm missing something here and so did the OP, but I doubt it.

[@karekarenohay4432]

MrSnowman You are absolutely right. This "explanation" explains nothing.

[@Andoxico]

long story short as you speed up you gain mass. a larger mass requires a larger force to make it accelerate.

[@karekarenohay4432]

The Andoxico Yes. I know about the Lorentz Fitgerald Transformation. But that doesn't explain why the speed of light is an absolute limit, or why this speed of light is an absolute in any frame of reference. Please, understand that i'm not questioning Relativity, but asking for a good solid explanation. Every explanation I could get comes from the Michaelson Morley Experiment, but this is not enough for me. The M.M. Experiment can be (and was) explained from the Lorentz Fitgerald Transformation, without (and before) Special Relativity.

[@Sanjidub]

you should add the "TED talks" intro or outro

[@ShermPWilliams]

To this day, i send this to people and blow their minds. I think it’s got a few things I somewhat disagree with for personal reasons but I think this is the best explanation on why you feel time goes faster when you are sitting down having a meaningful conversation with your friends.

[@haridoessports]

Wow! Youve made all my doubts clear! Thank you Sir!

[@JaretDawson]

I think that I first heard this explanation in a work of Brian Greene.... This is my favorite explanation, and it's beautifully done here.

[@lodziklocPL]

Good point. Although you'd have to be really stressed to feel like everything is in slow motion, like you're about to be killed and you need to react quickly to defend yourself or something. Calmly walking around doesn't seem like a good enough reason to feel like time is slowing down.

[@DanasaVFX]

i found a new favorite youtube channel

[@oatstralia]

As far as my HSC physics knowledge goes, "the way it is" is often analogised also with a rail-car scenario. As stated in the video, we shouldn't be able to judge our speed without an external point of reference (outside the window). However, if you were travelling at the speed of light 'c', and if 'c' could vary relative to your speed, light would appear to stop moving, and hence you would know that you were travelling at 'c'. Since this would violate this postulation, 'c' must be constant.

[@MasterAsra]

From your perspective you will still be living the same amount of time though.

[@anomoly26]

After watching a bunch of your narration videos, everything I think is in your voice. Not sure if this is a good or a bad thing.

[@ElizabethBones]

Thank you so much for this, I felt kind of alone.

[@gama343]

Much simpler explanation is that it would take infinite force to make anything with mass travel at light speed, and if you did manage to reach light speed through some sorcery you could never pass it because the moment you did you would travel back in time to a moment just before that, trapping you at light speed until you stop applying your magical infinite energy source to your space craft of choice.

[@ultimaterusemaster]

About the whole "nothing can go faster than light because that would be like trying to go more horizontal than horizontal", if horizontal is space and vertical is time, and we can observe that light moves (how else would we see?), would that not mean that light is not "purely horizontal"? From my understanding, if something were to go purely horizontal in this context, it would not move through time whatsoever, and that isn't the case since we can see objects like the sun, where it takes minutes for the light to reach us. Pure horizontal motion would essentially be teleportation, right? From this point of view, light isn't really horizontal exactly, but close to being horizontal, at least much closer than anything we know of. So then, in theory, wouldn't it be possible to go "faster than light", tilting a bit more to the horizontal direction than light is? On the other end, if someone were to somehow escape the gravity of the earth, solar system, galaxy, and whatever is using gravity to drag them along, so that they would be "near motionless", or pointing near vertically, could it then be said that they are traveling faster through time, but to an extent where it would be almost to "any point in time", like with teleportation mentioned earlier?

[@TempuraFriedJoystick]

ultimaterusemaster So, this comment is two months old, but I feel I can explain. When it's talking about an object's movement through time, we're talking about the object's PERSPECTIVE of its own movement through time. When you move extremely fast, you PERCEIVE time to be moving slower - because, to you, it is. The rest of the universe does not see this; only the object in motion is able to perceive the change. From our perspective, light takes eight minutes to reach Earth from the Sun - from the perspective of something moving much faster, they would perceive that eight minutes as being four minutes, for example. Now, no laws are being broken here - light is always moving at the same speed, traveling through a particular distance in a certain amount of time, it's just that the perception of it changes. So let's look at it from light's perspective. Light is completely massless, and it is moving through space as fast as it is physically possible to go in our universe. This means that its perceived value of time is 0. This does not mean that the light exists outside of time somehow - merely that it can't see it. From the perspective of a beam of light, there is no such thing as time - its past, present, and future all exist simultaneously. From the perspective of a beam of light, the very concept of time would be baffling - to a beam of light, one single, instantaneous moment is all that exists, its entire journey (no matter how long) compressed into such an incomprehensibly short time that time ceases to be a thing that actually exists... From light's perspective. This is why nothing with mass can move faster than the speed of light - by its very nature, light experiences its entire trip in one single instant, and so it MUST travel at one single speed the entire time - there is no "time" for it to accelerate or decelerate! Therefore, the speed of light is, and must be, constant.

[@ultimaterusemaster]

***** Oh ok, that helps a lot, I didn't see it from that perspective (pun intended), thank you.

[@Ennendra]

Huh...this could potentially explain a phenomenon I always wondered about; Music playing at a slower tempo when moving yourself at a fast speed.

[@christianramdial8026]

Remove the aspect of time. Time is an equation of man , Time is a man made restriction. When you sleep you cant tell time. That why the brain give you dreams to feed your purpose. events is not time. Fruit trees don't bear base on time they bear on climate.

[@jamesharford9788]

But climate is indeed based upon time.

[@barisstormcloak]

@SamuelHorler to put it as simple as possible, almost all equations to do with working out an object's velocity in mechanical physics involve mass, and photons (the physical representation of light) have no mass, making it's approx value of 3x10^8m/s the value of the infinity of velocity.

[@pandabearhana3956]

Best science lesson I've ever gotten.

[@charshii3745]

This is really good... But why is light speed the most horizontal? Who ever said it was... Like this video basically said that light speed is the fastest you can go and here is why you can't go faster. But I want to know why light speed is the fastest you can go?

[@Ambidextroid]

The flying spaghetti monster decided

[@charshii3745]

Ambidextroid I guess so .-.

[@runon8710]

Draw the graph out yourself. Y axis representing time, X axis representing movement through space. The arrow you draw can only move further through space and further through time, so in this case never go down or left, only right and up. This means, if you cant reverse time/movement through space, which you can't, then you can never move more through space than light it, which is not moving through time at all.

[@Ambidextroid]

Rufus Barnes I think he's asking why 299,792,458 m/s is the speed of light and thus the limit of the universe and not, say, 299,792,459 m/s. And this I don't think anyone knows.

[@charshii3745]

Ambidextroid Exactly! Cheers And also how do we know that light is the fastest, just cause we have never seen anything move faster that light doesn't mean that there is nothing out there can't

[@greygrey6517]

I think this explanation actually helped me to understand the theories about why going faster than the speed of light would actually let you move backwards in time. Once you go past the horizontal line and go into negative y (time), you would be moving forward in space but backwards in time. I don't think this is very practice to think about because I think you would end up seeing/colliding/diverging with your "past self" who is moments away from breaching lightspeed. And if light cannot escape a black hole, does that mean the gravity well is so strong that it brings time to a standstill. Maybe black holes actually have a mass large enough to exceed the speed of light and they send it through time somehow? I should change my major, this is more fun to think about than java.

[@stantrien8106]

You can't go past the horizontal axis though. Think of the reverse, if the line went all the way vertical. Going past vertical would require going slower than not moving at all. You try taking negative 2 steps in any direction...doesn't make sense does it?

[@codygraefser22]

I know you didn't write the comment, you just read it, but maybe a better analogy than the graph would be a video game stat point distribution. You have a set number of points to put in the four dimensions, and any unused ones go into the fourth by default.

[@mattkradelman1369]

Why does he sound like he's having a general conversation that makes sense when it seriously doesn't?

[@mrice102888]

Say you built a machine at the exact center of the universe holding the rod out pointing at the edge of the universe. At this time, the machine begins to spin at a very high rate of speed. The part of the rod that is closest to the machine is traveling around the center of the machine at as close to the speed of light as physically possible. How fast is the tip of the rod moving around the center of the machine? Otherwise, what is the maximum speed of the rod closest to the machine?

[@GFCOLCQuote]

This really did feel like a Ted talk, and if what that statement says is true than the information gathered from it was very insightful. I'm actually very glad I watched this all the way through as it felt very informative.

[@hellozere1]

The problem here is that you have to realize photons lack mass. When something approaches light speed, its mass increases/time around it slows down.This is essentially the universe pulling two barriers down on you to keep from moving faster. When a particle that has mass moves almost as fast as light, time slows down lengthening the life of the particle, but drawing out it's movement. Its mass also increases, making it harder to accelerate.

[@TheTexasDice]

Queen can.

[@Chizypuff]

Well that's not a very satisfying ending to the explanation. If you rotate the arrow so it is only pointing in the forwards direction, it is no longer traveling futureward. So the length of the arrow doesn't matter, since your speed is just a ratio between your direction futureward and your direction forward. Any number divided by 0 would still have instantaneous travel, which we know that light does not have. Unless he's saying you can only go as quickly forward as you can futureward, but that wouldn't account for the time dilatation.

[@Kyrari22]

wow I think that was one of the best thing I've learned from youtube since I started here...... I don't know what to say...

[@lodziklocPL]

Going as fast as light stops the time. You can't erase the arrow to not move in any direction. You have to point the arrow somewhere.

[@95FatAsses]

The speed of light limit is a limit placed on objects that move within spacetime. However, the universe IS spacetime. It is a separate entity (for simplicity's sake) that itself is not an object living within itself.

[@Gameguy602]

Literally my next thought though. If the line is horizontal, then you aren't moving forward in time at all. How can something be said to be moving through space at all if it's not moving through time to get to the new position in space?

[@stantrien8106]

Because time is relative. A thing with a horizontal value wouldn't experience any time, the trip would be instant, but anyone watching at a lower speed would see the person take some time to make the trip. That's why going to the next galaxy and back at near light speed would be seconds for the traveler, but they would get there long after earth was swallowed by the sun.

[@Ennendra]

Good point...still, I've always been confused with why music seems to slow down when moving around a lot. My only other hypothesis is simply the brain working faster than it normally does (perhaps some adrenaline-related thing makes everything seem slower?)

[@sp33d4l0l]

That's 38 MPH IN A SINGLE DIRECTION, at least, I assume it is. When light travels through a dense material it will have to evade all particles in its way, and since those particles bend space around it a bit and such the light actually has to travel further than when it's moving through, say, a vacuum. The time it takes for it to get from one side to the other will be equivalent to that of something moving at 38 MPH, but its actual velocity is not. I hope this is understandable and correct.

[@justuspickle]

there are so many different aspects to the speed of light and so many different ways to visualize it that for every person there has to be at lease _one_ that they can understand... but... that might be wishful thinking. it's hard for an entity to understand the functions at the edge of it's own existence

[@jamesharford9788]

The speed of light is neither profound nor arcane. Speed is simply change in position divided by change in time. Taught to us in elementary school. The big surprise is that for physical massive objects, there is an upper limit. This is just a discovered fact, like Antarctica. There is nothing inevitable about it. It just happens to be true. Now why? That is not yet known. Sorry.

[@Monkeyheadtpc]

It is. It can be directly deducted from the fact, that light is always measured at the same speed, regardless the viewers movement towards or away from it.

[@Tewfen1337]

I know that gravity and velocity cause time to move slower for you, so if you were to go the speed of light time would stop for you? If you were traveling traveling at the speed of light from point A to point B by the time you get to point B your journey would have already started. Meaning that you would have arrived instantly to your destination (in time). Please correct me if I'm wrong.

[@TornicTL]

arriving from point a to point b in an instant is teleportation. Traveling at the speed of light means. "Sun at a distance of about 150 million km. Light moves at 300,000 kilometers/second. Divide these and you get 500 seconds, or 8 minutes and 20 seconds." Also answering to your movement question-Faster you move the faster the people around you move for you it might only be one second but for others it might have been hundreds of years. But because you move so fast, time slows down for you particularly which technically mean you would age slower, but the time would never stop, unless you have no mass that is. This is because photons have no mass they can travel at the speed of light, humans will never be able to travel at the speed of light. Although they can bend the universe, just like if you to bend a paper, (creating warmhole) and arrive at any point in universe instantly.

[@Neonmonkey42]

Not to mention the fact that the laser is light so it traveling faster than the seed of light would, as he stated in the video, be like saying "more horizontal than horizontal".

[@Mekose]

I liked the lecture/presentation idea a lot to break up the speech a little bit but I think it was too frequent and distracting. For some reason it just came off as really irritating because I was so interested about what you were talking about, I wanted them to shut up so you could continue. I really loved your voice and the writing was very informative. I've asked that question a lot and this is the best answer I've ever heard. (credit to whoever wrote it and your awesome reading!)

[@0cheeseburga]

Oh my god, *thank you* that actually made sense to me! :D

[@Aazdremzul]

I thought it was basic to explain it like: Light has no mass, and anything with mass can never achieve the speed of something that is has no mass. The less mass you have the faster you can go as long as you have the potential to go faster. Since light has no mass, it has the potential to go extremely, and unbelievably fast.

[@rundom32]

And that is why I love reddit.

[@seltonejock]

really this is more of an explanation for things not being able to move faster than time rather than light

[@OlCapitain]

That is the idea, the closer to the speed of light you go, the slower time moves for you. Meaning if you were to travel at the speed of light, you would arrive everywhere instantly, the only difference is that time would have passed for everyone else.

[@theragingwarcat1410]

The trick is figuring out how to mess with the piece of paper

[@9786Gdeadpoolmod]

I'm surprised that most people don't know this, but there is something that has traveled faster than the speed of light. There are these things called nuetrinoes (nutrinos? nuetrinose? I don't remember) I learned about them in my science class. They traveled .00006 of a second faster if my memory is correct.

[@KamiKagutsuchi]

This is really good, but the laugh track makes it so cringe worthy..

[@morezombies9685]

That's the entire point of the laugh track. It's mocking awful jokes at scientific lectures... So many people in these comments have no clue what satire is and what this video is satirizing...

[@notascientist709]

@@morezombies9685 yeah they clearly have no idea what satire is and defiantly just dont catch that its being satire

[@ProtusMose]

@@notascientist709 I can't tell if you meant definitely or not. Both work in different ways and I kind of love it.

[@KalishKovacs]

At the speed of light, Time stops for you personally, Hence the use of "relativity" Fyi, People stopping time in movies annoys me. Every time someone stops time in a movie, I imagine the perspective of the normal people around them, as an object moving the speed of light moves past them. Hint: The meteor in russia was moving a tiny tiny fraction of the speed of light, and it was a fireball.

[@leo12chandu]

I have the exact question. how can the arrow be moved down to horizontal when the speed of light is constant. The horizontal sounds more to me like going at an infinite speed. I am not convinced yet. But thanks for taking time to explain.

[@BandNerdcp]

Wait.. soo.. if you're completely "Horizontal" then you're no longer moving in the "futureward" direction.. Soo.. would going at the speed of light stop time (well at least for yourself)? And theoretically if you could go faster than light, would you would begin moving back in time?

[@Karian345]

very clever way of playing the terminology of the speed of light

[@asteroceras]

Photons in a vacuum travel at the speed of light, c, by definition.

[@Fjolvarr]

But what if I can point into the past or future?

[@oneiromancing]

So, through general relativity, could There be a way to turn that arrow all the way past the horizontal line, and through to the pastward-facing line? I mean, if there would be a way to do the opposite of sitting in 'rest' without being in motion? And, more importantly, would that technically make someone travel pastward? By turning that metaphorical car around, can you travel toward the pastward direction

[@BlueCosmology]

Light was thought to have mass for a long time before we could even measure the mass of any atoms, let alone fundamental particles and bosons. There are many theoretical reasons now that light has no mass, if light had mass then the fact that so many things (such as time dilation, gravitational lensing, length contraction) were experimentally verified would be insane. They are all reliant on the fact that light has no mass.

[@alexk12271]

Even in science fiction, faster-than-light travel is not done by 'breaking the light barrier'. If one accepts the possibility of alternate dimensions, or parallel planes of spacetime, it is theoretically possible to EFFECTIVELY cover distances faster than light would. This is not achieved by exceeding the speed of light - rather, it is achieved by entering one of the said alternate dimensions and reentering 'our' dimension at a point far distant to the original location. By exiting our dimension and travelling in a parallel one, you effectively 'teleport' - IE, disappear from existence in this dimension, and reappear at a different location. This is the concept behind faster-than-light travel in many works of science fiction, including star wars, star trek, and halo.

[@runakovacs4759]

Or just warp drives. Mass cannot move faster than light, but space can.

[@blazedraven1470]

My eyes have been opened

[@CasualGraph]

Wait... so if the arrow is pointed horizontally, then doesn't that mean that it's not traveling through time at all? We already have a set speed for light, so that means it's not completely horizontal. If something could be pointing entirely right, then that would be an instantaneous traveling method since you would accelerate up to horizontal and then slow down to reenter into the dimension of time.

[@ChaseSkylark99]

Yup! However, that last point, at the 99.9999% (repeating, of course) of light, takes a nigh-infinite amount of energy to get to the full 100%, and decelerating would take the same amount of energy. That instantaneous travel is why, in the perspective of a photon, it is both emitted and absorbed in the same instant.

[@aSStronaut111]

If you had enough energy to reach light speed to go somewhere you would complete the trip instantaneously because time wouldn't be flowing anymore so the moment you reached light speed you would arrive.

[@matty808pyro8]

so instead of traveling through time, why dont we just change the rate at which everything moves slower or faster? like watching a video you rewind and fastforward.

[@CodeumOfficial]

Oh my god that clicked so easily! the question now is, how to rotate the arrow further than horizontal and more backward.

[@sixstanger00]

If I understand this correctly, there's a finite "speed" that can be applied to time and/or space, and can be distributed among the two, yes? OK, that just means that TOTAL speed available for distribution is the ultimate determining factor. So if the TOTAL speed available could be increased, wouldn't this allow for X,Y,Z speeds faster than C? Think of this way: Imagine a magic meter from an RPG, and it's 50% full. Imagine a health meter, that's also 50% full. Magic can be used to restore health, and vice versa, but you only have the total length of one of the two bars' worth to work with. Now imagine you get a power-up in the RPG that extends your magic and health bars. You now have MORE to work with than you did before. Alternatively, based on the "arrow on a x-y plane" model, wouldn't time simply start to run backwards at above C? This may sound nuts, but isn't that possible? We're "stuck" moving FORWARD in time, so technically, we can't experience anything that's running BACKWARDS, except for the nanosecond we and the backwards-moving object both exist in a "present." After that, we've moved on to our future, and they've moved on to our past (their future). So riddle me this: Isn't is possible that faster than light travel could very well be a universal norm, and that we as forward-time travelers can only experience 50% of the universe? If we are moving through time FORWARD at 100% speed when at rest, doesn't that mean that it's also possible for someone to move BACKWARD in time at 100% while they're at the TRUE cosmic speed limit?

[@Linguz]

***** If there was a way to increase total speed, you could go faster than C. Unfortunately, there is no way to increase total speed (that is known). Likewise, we have no idea how to turn the arrow past the speed of light (to get into negative time speed).

[@sixstanger00]

Linguz If I understand the principle correctly, then traveling at C is how you'd get the arrow level on the horizontal plane. (Max speed thru space, zero speed thru time.) According to Einstein, any speed _above_ C would cause you to reverse your direction in *time.* (The arrow is now past the speed of light, pointing into the lower right-hand quadrant). However, this is where the whole thing breaks down: If Einstein is correct, and there's a limited amount of "speed" that can be distributed between your movement through space and your movement through time, then: At 0% speed through *space,* you are moving at 100% speed through *time.* At 0% speed through *time* you are moving at 100% speed through *space.* (presumably at C). But if you *exceed* C, at say, 120% through space, how could you be *moving* through time in *reverse?* None of your speed is being distributed to your movement through *time,* so under this model, I can only draw 2 conclusions: 1) Time doesn't actually stop a C, but is likely to be moving at a mind-bogglingly slow pace (This would agree with what we know about trying to accelerate objects to C thru space; we can forever *approach* C, but never actually reach C. Basically, this lends credence to Einstein's theory that space and time are one of the same. Likewise, we can forever approach a stop in time, but never actually reach it). 2) The model holds up as presented, and any attempts to *exceed* C would actually result in time moving in reverse at X speed, and your movement through space reduced to Y speed. Yes - I meant that - I'm saying that if you were to attempt 120% speed through *space*, you actually reduce your speed to 80% and start moving backwards in time at 20% speed. In this case, as nonsensical as it sounds, everything is abiding by the laws of physics as we currently understand them.

[@jamesharford9788]

Yes, that is the "length" of the arrow, which by definition is the speed of light, c. Its computation, however is not the pythagorean square root of the sum of distance squared plus time squared, but the square root of their difference, which is something entirely different from what the video misleadingly suggests. Better to stick with the venerable speed varying relativistic mass than this absolutely misleading and ultimately confusing explanation

[@fleabag500]

The rod would bend, like how spinning galaxies drag and form spirals. This is because of inertia i.e how objects at rest prefer not to gain momentum.

[@LCDRformat]

Actually, I read an article on the Harvard website where a team of physicists used different pieces of matter to slow light down to about 38Mph. Just something to think abut.

[@jamesharford9788]

Speed of light in a vacum is what Special and General Relativity is about.

[@scarrjumpstyle]

So explain why muon-neutrinoer is faster than light particles?

[@ritzshetty3913]

This might sound weird but considering just the example of the train from 2:20 to 4:00 I'd like to comment on this. So basically imagining the train is the time and stations are today and tomorrow, we might take time from moving from 1 station to another (today to tomorrow) but generally we use our cell phones to inform another person waiting for us in another station(Tomorrow station) through call or text. I'm trying to say is although we cant travel faster than the speed of light but we could or should have a device projecting a ''light of information'' in the form of text or call to ourselfs in the future and also receiving 1 back from the future our self using the device. I'm not really a science student yet, so sorry in advance if I break any laws(Let me know if there were any in the comments). But this is just an idea I want to contribute to the experts.

[@davidwave4]

+Ritz Shetty Not sure if you broke any laws, but you inadvertently wrote the plot to Steins;Gate.

[@ritzshetty3913]

davidwave4 Steins Gate? The anime ? Lol. Now i might watch that.

[@jamesharford9788]

In 1985 Lewis Carroll Epstein wrote a book, "Relativity VISUALIZED". In chapter 5, titled "The Myth", he said the following: "There is afoot an erroneous idea. It is that in physics the ultimate reality is a mathematical prescription, an equation. In fact, the ultimate reality is a little story or myth. To demonstrate this, I wil privide a myth for the Special Theory of Relativity, which will eventually come to be taken as the reality". Prophetic words, for the myth is the story given by this video. And although comforting and taken by many as reality, it is -- as the author admitted -- a myth.

[@theflexintexan2152]

This uses ideas of special relativity to explain why nothing can travel faster than light. Didn't Einstein invent special relativity in the first place under the assumption that nothing travels faster? Even though the predictions of special relativity have been experimentally vindicated, this is still a huge logical no no.

[@theflexintexan2152]

Is it true that anti-particles are normal particles traveling backwards in time?

[@mortemapparatus4088]

michael warner I would think that this would mean that the future itself has an ending. Which might question whether or not the universe we live in now is going to live on for an eternity or not. I honestly don't think that anti-particles are particles moving backwards in time because then we'd have to ask how far back to they go and where do they originate from. I honestly thing 'anti' matter is just the yin-yang policy of the universe to put it bluntly, but I'm really just typing up what pops up into my head so take what I say with a level head and a fair amount of doubt prepared.

[@vine01]

@@theflexintexan2152 this one is quite easier to "answer, explain" than the first question :) it has to do with CPT symmetry, principles that govern all matter that we know of, the events that can occur for any of the Standard model of particles. It says that all laws of nature apply the same way to everything, if we change Charge or Parity of the object. Change of Charge means if you replace electron with positron (particle of same mass, only + on electric charge), laws of nature will apply the same as to electron. Parity change means change of spatial coordinate. Basically roughly i think if an object changes position, it does not change the way the laws of nature apply to it. We have already found some events and particles that violate either of those. T symmetry is a time symmetry. 2nd law of thermodynamics states that energy can only disperse as time advances. Entropy rises with time, all eventually dissipates (is spread uniformly in spacetime). It has been theorized there could be particles or events that violate this T symmetry, but we have not found them yet. So all in all anti-particles do not travel in time. They just have one of their "properties" inversed to their "normal" particle counterpart. Electron Positron, Proton Antiproton, and atoms made of those. Neutron has Antineutron buddy. Quarks and Antiquarks. They are all out there. Or very near, antiparticles are produced in fission reactors all the time. Hypothetical time traveling particle should be called Tachyons.

[@mtext]

I thought the laugh-track was a bit distracting, but everything else was wonderfully well-read, as always.

[@Asadron]

Wait, you mean it's not a public speech/talk? Wow, and I thought it was a recording of a video with just the audio lol.

[@gregtaylorlives]

fundamental nature of the universe, there is no explanation deeper

[@siddhantsinha7807]

what if we rotate our four-velocity arrow in 4 quadrant.That means we have some component in pastward direction and some in horizontal. So can we travel in past in that case?

[@Andrew-kw3kz]

+siddhant sinha The arrow would never pass into the negative horizontal axis (which indicates pastward movement). It is limited between the default position (upwards = futureward movement) and the reciprocal (horizontal = no movement through time), which happens to be orthogonal to the default.

[@siddhantsinha7807]

Ok ty

[@stantrien8106]

Moving past-ward is as silly a concept as going slower then standing still, because really they're one and the same. Imagine the graph moving with the line as it progresses, (0,0) being the present, so that he past is always in the negative.

[@Troselingasher]

The point about "can't be more horizontal than horizontal" is flawed in its assumption that light is that horizontal apex

[@sean..L]

I actually got up to put the kettle on, while I was listening to this.

[@TheGrubslaughterhous]

hello existential dread

[@Mezcal2008]

first question, what is light? particles or waves, or both combined? and if light is made of particles, then in one second on a straight line of 186,000 miles, how many other particles does it have to hit on its way? does it create like a barrier or wall to have to go trough it? hope somebody has the answers, empty space is not really empty, is fill with gravity, particles and waves, it's like a ocean of particles, maybe that's why light has a limit.

[@insearchfortheapple]

I don't think that the term "speed of light" can only be taken as a reference to how fast light can move. An easier way of thinking of it is the maximum speed for everything, and we just use the speed of light as a term to describe it. There is a maximum speed and light just so happens to travel at that speed. So to answer your question, light can be both a particle and a wave. That is why I emphasized that the fastest speed is light through a vacuum. Light travels at different speeds through different atmospheres when it is acting as a particle. That is because it is colliding with all of the particles. But the presence of other particles is not why there is a limit. If particles caused this limit then, in a perfect vacuum, light could travel at an infinite speed, and it doesn't do that. In the perfect vacuum and with the perfect conditions for light to travel at its fastest speed it would still hit a limit.

[@pheadrus1999]

Okay, I may not be the best person to talk about this, but I think it's safe to say that light is made of both particles and waves. This aspect of light is called the wave-particle duality. So basically, light can act either as a wave, or as a mass of particles, depending on the situation in which it resides. This characteristic delves into quantum mechanics, and is somewhat related to Schrodinger's cat. Light is composed of BOTH particles and waves, and only differentiates it one of the two once we start to observe it. There is an important experiment called the "double-slit experiment" . I can't explain all of the details here, but the wikipedia link is here: en.wikipedia.org/wiki/Double-slit_experiment Basically, the experiment showed that light was able to be split into two or more separate beams or light, something that could only happen if it was made by waves. But strangely, some of the light was also absorbed, which indicates it is also composed of particles. Light is also dispersed throughout space by the particles and matter in it's way. The reason why the ocean and sky is blue is that light scatters when is penetrates the atmosphere and water. visible light can be split up into colors based on wavelength. Due to the size of it's wavelength, blue gets scattered easier, and becomes visible away from the original source of light. Kind of hard to explain without a drawing, so here's another link: math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html tl;dr: Light is both a particle and a wave, and is dispersed by matter, depending on the density of the object. If anything in here is wrong, call me out on it. I got all of this from my Chemistry 1 course, and that was a year or so ago, so my memory is kind of iffy. Thanks for asking this question, it was a really good refresher!

[@TempuraFriedJoystick]

You To be perfectly clear, even when moving through an object, light is still moving at the speed of light - its speed doesn't change. It's merely taking a longer path, since it's bouncing off all of the objects in its way. For example, if I have a Lamborghini drive down a straight track at 120 mph, and a bumper car travel through an obstacle course at 120 mph - they both had the same speed, the same starting and ending point. But one of them traveled more distance, because it took a longer path. The speed was constant, but measuring purely from time and distance from start to endpoint, it appears to have traveled slower.

[@SamuelHorler]

So I now understand the theory, but still, why is it that light of all things is the fastest moving thing through physical space? The only thing related to that I got from this video is "nothing moves faster than light because it just doesn't"... what's the evidence for it? Anyone?

[@leo12chandu]

Thanks Mike for the reply. But it still means we cannot prove that nothing can go faster than light.

[@95FatAsses]

This is exactly why I believe that time travel is not possible. Also E=mc2 proves we cant go faster than light or even at the speed of light. Light Moving at the speed C is massless. Anything maoving at the speed of light has to be massless. When mass is 0 in the equation, E is 0 meaning it requires no effort to move a massless particle at the speed of light because that is its natural speed. But the second you have a defined amount of mass that is not 0, E increases dramatically. Try it.

[@coollotion5884]

The fact that I don't even smirk at the laugh tracks makes me feel stupid. Although, the grades I receive produce the same feeling.

[@thomasconnolly2128]

You CAN get to another place faster than light can travel there. You would merely need to open a whole in the universe and travel to another universe with the same or similar constants, but with the speed of light higher than previously. The problem with this is obviously that in order to open a wormhole, you would need something that has some pretty massive amount of power (equivalent to around 50 million atomic bombs), a universe where the constant of the speed of light is infinite (nearly impossible due to how a Universe would have to exist under some presupposition of law based upon how Universal Relativistic Theory works), and a vehicle that can already go the speed of light in the new universe (which we are incapable of doing because we are unable to go faster than this Universe's Light Constant.) This was actual explained (momentarily) in one of the Ender's Game books, but that theory still has problems because it presupposes a Universe with nothing in it.

[@atomheartother]

No one ever said you couldn't get somewhere faster than light can - because that is beyond whatever science knows so far. But nothing can go faster than the speed of light in this universe.The word "go" doesn't mean "get to somewhere", it's a measure in velocity.

[@thomasconnolly2128]

I'm not trying to dissuade people from thinking this is science fact. I just though I qould share an interesting bit of science fiction that could actually work in the natural world (with the correct presuppositions).

[@DiabloLOT1976]

You can't go faster than light, and so you can't escape from the black hole

[@legoboy1707]

So...if I were somehow able to move at the speed of light, would time...stop? If I am going entirely in the horizontal direction, wouldn't time stop for me? I'm so confused...but a bit less so than I was before.

[@neztkeres]

+Legoboy yes it would

[@GOmegaPHD]

+Legoboy Yeah but you'd probably die well before then from accelerating to said speed lol

[@Gindaman999]

Time=0 relative to you when you are travelling at the speed of light.

[@Sontraid]

Actually it means, you dont experience time. Ofcourse Time wont stop around you.

[@Tewfen1337]

I know that gravity and velocity cause time to move slower for you, so if you were to go the speed of light time would stop for you? If you were traveling traveling at the speed of light from point A to point B by the time you get to point B your journey would have already started. Meaning that you would have arrived instantly to your destination (in time). Please correct me if I'm wrong

[@holopengin]

Wait, does this mean that light would move instantaneously through a true vaccum, and the "speed of light" is really a misnomer?

[@dominickjohn7762]

vacuum*

[@Buildings1772]

***** but why to the observer does the object appear to not travle any faster than the speed of light. if indeed what is described in the video is true then it would appear to the observe as an instant as well.

[@stantrien8106]

***** Because as stated in the video to move in space is to give up speed in time, going "The Speed of Light" is to completely go to the right "space" vs going forward "time", and time is relative, so someone going fast in space "moving" experiences time slower then someone going faster in time "standing still".

[@jamesharford9788]

It is an analogy that does not bear scrutiny. The arrow of constant length has a horizontal component (distance) and a vertical component (time). Speed is the ratio of those two components, distance/time. When the arrow is vertical, distance =0 and speed is zero. When the arrow is horizontal, the time component is zero and the speed is distance /0 = infinity. So the analogy fails right there. It is just a story to make you feel like you understand. Don't be satisfied that easily!

[@online12plus]

So if i somehow go the speed of light and the arrow is as horizontal as it can be, then is time frozen, or is it nonexistent? Or am i just simply not experiencing time? if so how does one not experience time? what would it look like to not experience time?

[@SpartakMs83]

+online12plus Effectively you would no loner be traveling through time. A photon of light for example does not experience time. From its perspective its entire existence from emission until it strikes an object happens all in the same moment. I would imagine it is like a coma or memory less sleep. For you no time would pass, you wouldn't even age.

[@masterchef1837]

but even a moment is a period of time.

[@MatiProbably]

"Because that's the way it is" doesn't answer my question. If anything it makes it worse.

[@95FatAsses]

But where would you get the energy to do that. I highly doubt that humans or any entity in space time for that matter could perfectly harness the energy released in a Types 1b, 1c, and Type 2 supernovae. Those kind of supernovae have such high densities that electrons cannot prevent degeneration by combining with protons into neutroons. This creates a supernova that releases more energy than the entire Universe combined (Of course without other similar supernovae included.)

[@OktoberSunset]

In a vacuum. If it's travelling through the right medium, a snail can go faster than light.