You Are Traveling at the Speed of Light Right Now

[@SciShow]

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[@classicalmechanic8914]

Science: Only photons can travel at c because they have no mass. If you could travel at c, time would stop. Also science: You are travelling at c right now.

[@ryvyr]

..... please do not become one of those low hanging fruit mid-video non-adsense channels :( In *mutual respect,* plenty people watch non-adsense if at very front/back/both, rather than skip/click off =/

[@Lesserthannone]

Finally! An adequate excuse for my partners dissatisfaction with regard to our nightly quantum entanglments ...

[@davidbarela5279]

He knows 😳 1:19

[@personwithcommonname]

Pink shorts, leopard print slippers. Nice choice!

[@Aragorn7884]

💩💩💩

[@danielsykes7558]

Lol

[@RolandoGarza]

Is it not the best place for enlightenment?

[@christiana9039]

Called! OUT!

[@michaelwall9882]

They call me Mr Fahrenheit, I’m traveling at the speed of liiiight! - F. Mercury

[@UltraZelda64]

That is literally exactly all I could keep thinking of when watching this video. I think I wanna listen to some Queen now.

[@Laochraiceann]

Freddie was way ahead oh his space and time.

[@TheMysticOne27]

@@Laochraiceann yes, but Brian May is a literal astrophysicist

[@Andrewdeank]

Don’t. Stop. Me. NOWWEW

[@ikebeckman1074]

I wanna make a supersonic man outta you!

[@deawinter]

According to Pokémon Go I am always going too fast

[@graphixkillzzz]

people still play that? 😳

[@Bear551590]

Deep cut!!

[@JayHamster]

I'm going so fast not even the ban wave can catch me 😉

[@JayHamster]

@@graphixkillzzzNo, people don't play it any more, they spoof it.

[@queztocoaxial]

If only another 10,000,000 people had Pokemon Gone To The Polls 😕

[@svenmorgenstern9506]

🎶 C is for lightspeed And that's good enough for me! 🎶

[@just_kos99]

"186,272 miles/second -- it's not just a good idea, it's the law." A favorite bumpersticker of mine, from years ago.

[@davechurch9354]

I'm off to watch sesame street

[@davechurch9354]

And eat cookies love the comment❤❤

[@davechurch9354]

I'm from New Zealand where you

[@davechurch9354]

Who you calling a c😂😂

[@samstarlight160]

It's so cool hearing about all these other people involved in the process. It's a reminder that even people who we think of as lone, super geniuses in pop culture still stood up on the shoulders of those before them in order to make their contributions

[@mikerouch416]

Hendrik Lorentz and Henri Poincaré developed principle relativity and Einstein took their research and patents and credit.

[@culwin]

@@mikerouch416 That's not true.

[@raythegardener]

If the cops find out about this, speeding tickets are going to go crazy.

[@raythegardener]

Dude, you were going 670,616,629 in a 30 zone

[@theswiv]

But if they know how fast you were going, how do they know where you were?

[@danielsykes7558]

Excuse me sir, do you know how fast you were going?

[@sion8]

​@@theswiv Unfortunately we are not particles…

[@Hotshot2k4]

If those cops could read, they'd be very upset.

[@RobinDSaunders]

There's a mistake near the end (the bit starting around 9:40), as some others have mentioned. Yes, the observer will measure a larger amount of movement through space, but there's a minus sign in front of that term! So the amount of time they measure has to be higher, not lower.

[@GSBarlev]

💯 Though it gets confusing, because we're talking about "distance in time per unit of proper time." And, in terms of intuition, what ends up happening is that the relationship gets inverted. That is, the core observation is: *the faster you observe something moving through space, the **_slower_** you observe their clock will be ticking.*

[@just_kos99]

"Now the universe itself keeps on expanding and expanding, in all of the directions it can whiz! As fast as it can go, the speed of light you know, 12 million miles a minute and that's the fastest speed there is...." -- "The Galaxy Song" written by Eric Idle of Monty Python (it was in "The Meaning of Life" and has a really cute video of it on KZbin). The song is remarkably accurate, actually. He rounded up to the 12 million miles a minute, however (it's 11-something million really).

[@TKBarnes]

I'm pretty sure I've seen the "butthurt version" with Brian Cox or Dara O'Brien or Neil Tyson, singing along and being "scientifically accurate." and it was funny as hell. :D EDIT: I remember I'm on youtube, found it: kzbin.info/www/bejne/lXqpeHtnZtqrl6s

[@jtjames79]

Makes you feel so, so, unsignificant, doesn't it? Can we have your liver then? 💀

[@rafaelperalta1676]

I'm pooping at the speed of light!

[@jacebeleren429]

C is for poopy, that’s good enough for me.

[@MMPAspergerian]

LoL explosive diarrhea is faster than the speed of light

[@five-toedslothbear4051]

1:24 OK, but what if I’m sitting on the toilet watching this on my Vision Pro, and I have the immersive environment of the Vision Pro set to the surface of the moon, which is one of the options? Yes, one of the benefits of having a Vision Pro is that you can take a dump on the moon!

[@MarxMin]

😅😅

[@omerkaya545]

You're not, you're moving away from the poop at the speed of light.

[@DragoniteSpam]

Another fun way to think about it: your movement through spacetime can be thought of as a 4-dimensional vector with magnitude of c. If you're sitting perfectly still you have zero motion in the space dimensions and your motion through time is just c, while if you have some significant motion through the space dimensions your motion through time must be reduced so that the magnitude of the vector is still c. Hence, time dilation.

[@garrenosborne9623]

Wow nice explanation

[@theundone777]

This is exactly how I picture it.

[@JasonB808]

Almost correct. Remember time and space are one. It’s hard to us to wrap our brains around this concept because if we sit still we still in the same place on earth, our reference point was only the Earth, that would be true. But just rewind back to earlier to January of this year. The earth isn’t in the same place it was around the sun as now. Thus we moved in space and in time if the Sun was our reference point. It gets even crazier. We are getting close to starting a new year. So that means Earth will be the same place it was when it was last year in January. Yes, but only if you’re looking at the Sun as reference point. Zoom out to the galaxy as a reference point. The sun is moving around the Milky Way so the also is moving through space and time. That means that the earth is never in the same place in space time. It has moved with the sun around the Milky Way since creation. The same thing happens when you zoom out to universe as a reference point where time and space between galaxies is expanding. Your example only sees earth as reference point but not the sun, or the galaxy which at those reference point totally shows that we are always in motion in time and space. It’s only when we look at the universe as a reference point do we realize everything moves at the speed of light.

[@Bluhbear]

@@JasonB808 Almost correct. 😉 There is no absolute universal reference frame as you're describing. Motion and position only have meaning in relation to other objects, and the Earth or your toilet are as valid as any of them.

[@Ceelvain]

If I understand the formula, we have (ds^2+dx^2+dy^2+dz^2)/dt^2 = c^2. That does not make it a euclidian 4D space xyzt.

[@BadgerMole_]

scishow goes hard

[@ThaBeatConductor]

This is why I prefer to call c the Speed of Causality.

[@firstnamelastname9918]

YES! YES! YES! YES! I have an ally here!!!!!! You're now my new friend. (EDIT: been preaching this for years)

[@teaoanimar]

Same

[@x-r-s]

+1

[@raymondwall8187]

Isn't that why it is "c?"

[@BrackenStrike]

Had this exact conversation in Physics 2. I asked my professor if there was such a thing as a rate of travel through time and he disagreed with me because he didn't think there were units that could describe such a thing. I'm like, "dude, the universe doesn't even care if we have the units figured out."

[@mcv2178]

I travel through time at the rate on one second per second. : )

[@-danR]

Sometimes actual profs are wiser than ten youTubers who think that the phrase "travel through time" is even semantically, let alone physically, cogent.

[@MrAlanGrey]

9:42 I get you're trying to simplify it, but an increase in distance in space must be accompanied by an increase in distance in time, not a decrease. It's subtractive, not additive. If t - x = s then (t + 1) - (x + 1) = s t + 1 - x - 1 = s t + x = s t goes up, x goes up.

[@philp4684]

I'm replying to boost this comment higher. I've just said the same thing before checking to see if anyone else had already said it. (BTW, you meant "t - x = s" in the last line, not "t + x = s".)

[@maxi4251]

yea lol, that line confused the heck outta me.

[@NotSoMuchFrankly]

Yeah, they showed a formula where something on one side of the equation is inversely related to the other thing on the same side of the equation. That works in multiplication but not in addition/subtraction. If add to the amount you subtract, the other value has to put back what's being subtracted by also going up. I don't know what they were thinking and trying to say.

[@jamesinman9262]

They're squaring both components. This turns a quantity (x + a)² into x² + 2ax + a² This would turn the quantity (x - a)² into x² - 2ax + a² So an increase in distance correlates to adding 2ax + a² to the original value. To conserve the quantity, the time² must decrease by an amount that offsets this to make it the same.

[@Fayanora]

Someone I once talked with years ago had this theory called "the stillness of light." His theory was light didn't move at all, but somehow everything else moved slower than light did. That's all I remember about it, and I don't believe it, but I still think about that from time to time.

[@Science4Real]

We always assumed only light could be that fast, but it turns out everything in the universe is the same on a journey through spacetime that we’ve never even realized

[@megamcee]

Well, relatively speaking we're traveling faster than c, because to someone outside of the range of our observable universe, our point in space would be moving away from theirs faster than c (hence the "outside of the observable universe range")

[@ericcummins5910]

I was thinking the same thing when he was talking about frame of reference, he just didn't extrapolate out far enough

[@enadegheeghaghe6369]

I thought the "universe" includes everything that exists. How can anything be outside it?

[@ericcummins5910]

@@enadegheeghaghe6369 that's a great question, and not one that can really be covered in a few sentences. The key is we are talking about our observable universe, which extends to about 46 billion light-years in all directions. Outside of that 90 billion light-year bubble the rest of the universe is receding away from us at, or faster, then the speed of light. There are galaxies that we will never see simply because they are on the other side of our bubble and their light will never reach us.

[@bosslca9630]

My thought experiment for this is to define three frames of reference. First to fire a photon/lightwave along a vector/numberline X starting from X=0. This is reference 1. From a Stationary perspective, reference 0, the Lightwave is moving some speed in a postive X direction. The Lightwave arguably can view itself traveling in a positive X direction. That Lightwave, immediately once fired, fires it's own Lightwave behind itself, creating reference 2, in the X vector in a negative X direction. So from the stationary reference 0, Lightwave 1 is traveling +X and Lightwave 2 is traveling -X. From Lightwave 1's perspective while traveling positive, Lightwave 2 is at X=0. And from Lightwave 2's perspective while traveling negative, Lightwave 1 is at X=0. As such, the only way to rectify how both photons can 'see' the other as stationary is to apply time dilation to such a degree that time has effectively 'stopped' for the other in their perspective. In other words, Photons travelling at the speed of light do not 'age' in reference to other Photons. So I ask the question. From the persepective of itself, does a Photon age? and if so, what does it experience? Does it travel to the infinite 'end' of the X vector in one infantesimially small duration of time? A photon from a distant star travels a vacant path till it happens to excite an electron in the cluster of mass that is a Human eye in a degree of time? If a Photon does not 'age', then the distance between the star and the human eye is a non-factor and from a photon's perspective, we still exist inside the singularity?

[@axle.student]

It is a difficult question and has no answer in relativity, other than to say massless particles have NO concept of time or time dilation according to Mr Albert :) Time dilation can only be applied to particles and objects of mass. > So officially does a photon experience zero time or does it experience time is an invalid question. . It is an interesting thought though and even bothered old Mr Albert somewhat when he was working it out, and even later in life :)

[@philp4684]

The explanation of time dilation at 9:45 is completely wrong. An external "stationary" observer measures a LARGER time interval than the "moving" observer measures. For the "moving observer", in their own reference frame, ds^2 = (cdt)^2, as previously explained correctly in the video. But for the external observer, dx^2 + dy^2 + dz^2 is non-zero. For ds^2 to remain the same, the external observer's (cdt)^2 must INCREASE by the value of dx^2 + dy^2 + dz^2.

[@jozefff7911]

I think the possibility that someone living on planet earth has the equation to explain the entire universe is unbelievably small. No matter if your an infant or if your Einstein. An ant cannot walk from Paris to Barcelona, it is just out of his reach. We must accept that a lot if not all lies beyond our imagination

[@LambdaTF2]

Yes, I have a feeling that for every thing we discover about physics, another mystery will be revealed. An applicable theory of everything will never be possible. It shouldn’t stop us from trying to find out though. For some people the meaning of life isn’t about actually finding an answer but rather the continual search for an answer in a world without meaning.

[@goldentrout4811]

probably the best host for scishow! thank you Stefan!

[@Fomites]

Brilliant. One of SciShow's best!

[@joeywall4657]

I'm sitting in rush hour traffic on I-95 approaching Washington dc. I ain't moving at the God damn speed of light.

[@pdxmusl1510]

😂

[@jeaniebird999]

Actually, all of you guys are _not moving_ at the speed of light.

[@WeChallenge]

Been there done that for 2 years down to exit 15 then up to Philly for my second stop and final stop in Trenton NJ. 2 years was all I could handle of it, and I usually got in there before morning rush hour.

[@MySerpentine]

And that's why it seems to take longer :D

[@IceMetalPunk]

In college, I took an advanced physics class unintentionally, due to a clerical error at the registrar. The only thing I actually understood from that class was special relativity... and that professor still never explained the whole "time dilation happens because we're all moving at the same speed through spacetime" concept. I only learned about it a few years ago, from another KZbin video, and my mind? Fully blown 🤯 Science is so cool!

[@peterhansen5804]

Bravo! Nicely formulated

[@dinobirddoodles]

bro moving at any speed while pooping is terrifying thank you for putting that mental image in me brain

[@xnossisx5950]

I am really enjoying these newer episodes (such as the one on optics) that go a bit deeper into the science than most of the past couple years of this channel!

[@user-ex6xc5ox3k]

Stefan Chin looks and sounds like and secretly is the third Green brother

[@hacked2123]

Glad to see this video reaching the masses. Most people haven't thought this through to understand it

[@homerodysseus4203]

As someone with existential anxiety, I don't need this right now scishow 😂

[@laiika511]

Nah, take it in. It can help

[@jacebeleren429]

It’s not like you have agency over this.

[@Thraeryn]

You exist. One day, you won't. Eventually, there will be no record of your mistakes. Do your best.

[@Fomites]

​@@ThraerynHow bleak 😬 but true.

[@HOMBREooDEooACERO]

How does reference frame relative to speed triggers your existential anxiety? Pretentious

[@djayjp]

I feel like this did a good job specific to the point it was trying to make, but then completely failed to square/reconcile it with the fact that massive objects can never travel at the speed of light/causality.

[@Zergdragon]

On some level every time I hear / learn more about things like relativity, the more I come to a conclusion that in the grand scheme of things none of it matters... while also being extremely important.

[@spindash64]

6:10 train the scientists in literary skills so they can translate their findings for the press, and train writers in the sciences so they _stop clickbaiting with titles that say the opposite of the research findings_

[@IceMetalPunk]

Journalist: "Scientist discovers black hole in his bathroom." Scientist: "STOP BEING A PEEPING TOM!"

[@LogicalThinking-p2s]

If you travel against the rotation of something pulling on time like a a planet or galaxy itself flying against the rotation of the galaxy . at light speed . You'd travel as far back on time as time is moving forward.

[@juliagoetia]

Neat!

[@Bangers_mostly]

I can count on SciShow to Brighten my day 🤣

[@douglaswilkinson5700]

As I recall from physics class: everything travels through spacetime at the same velocity.

[@stevedrane2364]

Very good . . Thank you 👍

[@Hrocdol]

Woah. I've been hearing about spacetime and relativity in various science and science fiction contexts for years, and this is the first time someone has managed to present the math in a way that my intuition could glue up and connect with. Thanks, SciShow.

[@matthewjoseph4508]

Fun fact: technically we don't know if light travels at the speed of light, it could potentially travel ever so slightly slower (photons could potentially have a very small mass that we cannot currently measure). But it would be to such a small degree that it doesn't really effect our understanding of the universe if it is slower.

[@matthewparker9276]

That would break quantum mechanics.

[@CollaateraL]

Wow this was a top notch episode thank you so much.

[@fraliexb]

I'm going to need a Space Talk with Neil and Lord Nice to discuss this.....

[@mcdade7489]

Good idea.😊

[@pdxmusl1510]

😂😂😂😂 Neil has actually covered this multiple times. He presents it differently. By saying there's a way of interpretation of the space time interval like this.

[@michaelmoorrees3585]

Chuck got knighted !?

[@RyanSandorRichards]

It’s like watching SpaceTime but instead of being incredibly confused I am only partially confused 😂

[@l.ijspeert9040]

As has been pointed out, there is a mistake at 9:40. The time the Andromedan measures needs to be larger to make invariant interval the same. This makes sense if you recall the classic thought experiment of someone observing a person on a fast moving train: they will see the watch of the person on the train run slower than their own. In other words, the observer is measuring a larger time change in their own reference frame than the person in the train is measuring in their reference frame.

[@TheMooseNextDoor]

Interesting video! 👍 Thank you

[@robertkelly5025]

LOVE this episode!!! Love most of them, am causally friends with others but letting us know the giants on whose shoulders Einstein stood is fantastic. Also, do you need to live in Missoula or is the whole staff relocated there? Where is the video showing how the great Missoula floods are part of the reason the wines of Oregon and Washington are so fantastic?

[@deathraygonzo6339]

0:36 People already keep telling me that and you too, Internet?!

[@vladdangel]

No, we're not traveling at c because there needs to be a recent frame outside that's traveling at c relative to us. The only thing that does this is light which does not experience time and therefor does not have outside reference frames. Light is a dimension lower than everything else.

[@axle.student]

Time has no actual spacial distance. 'ct' is a pseudo spacial convention to make math calculations easier :) < Because photons are our messengers (information carriers) for everything in the universe we have to mathematically calculate out the time blur due to the slow photon to find some concept of 3D space. And we cant find any actual 3D space from a 2D snapshot, or the 4D derivatives of that snapshot.

[@sandragoodman2059]

This is the first SciShow video I couldn't follow.

[@Etimespace]

The universe works exactly the way it works and its operation is based on eternal recycling. There is no separate matter and no separate four separate forces. There is only one and the same physically concretely existing thing that is already a pushing force in itself. The density of this physically concretely existing thing varies from region to region in infinite space according to how it recycles itself. It can be compressed to be denser by external pressure, i.e. a pushing force. It can disperse less dense in space outward into the already existing space due to internal pressure, i.e. also a pushing force. Recycling does not require four separate forces. Recycling does not require anything other than the matter that is being recycled. I cannot help you if you are unable to grasp and understand this extremely simple thing. Thanks to you, I understand how Galileo felt trying to explain to his friends that it is not the Sun that moves in the sky even though it appears to move. It is at least as difficult for me to explain to you that a falling apple is not actually moving towards the center of the Earth. The expanding apple is moving away from the center of the expanding Earth, but more slowly than the surface of the expanding Earth. However, this is too much for you, so you can happily continue to worship your god / space, which does tricks. For me space which play tricks is naked emperor. .

[@chadb9270]

When you see the C just think causality. So, the speed of causality. Which also happens to be the speed of light and gravitational waves.

[@_andrewvia]

Stefan does a great job. Thanks Stefan. Savannah's shirt is REALLY LOUD !!!!! It's a great shirt. They have good taste in haute couture - ishness. Thanks Savannah.

[@livingbeings]

This is my favorite type of scishow video

[@JordanBeagle]

Strangely enough, this actually helped me understand black holes better

[@zachsharp4564]

Great minds like Copernicus and Einstein (this also kind of reminds me of Kant, in philosophy)-not only were they geniuses, but they had a particular genius for coming up with completely non-intuitive theories of natural phenomena with massive explanatory power. I know no advancement is made in isolation or absent prior discoveries, but it never ceases to amaze me that one person could sit down and theorize something like special and general relativity.

[@mossworksmedia]

i love this because it implies the existence of something that experiences no movement through time and is just an immovable mass in space

[@kreynolds1123]

l=l'×sqrt(1-v²/c²) length contraction t=t'/sqrt(1-v²/c²) Time dilation m=m'/sqrt(1-v²/c²) relativistic mass increases as relative velocity increases.

[@Carewolf]

"You are so dense, you must be moving relatively fast"

[@kreynolds1123]

@Carewolf 🤣

[@Jwinius]

Not gravity, but matter shapes the space-time continuum. Gravity is the effect that matter has on space-time, not the cause. Remember Wheeler: matter tells space-time how to curve and space-time tells matter how to move.

[@chaosopher23]

I don't think nerding-out like this will get me out of a speeding ticket, but I can try!

[@TheRealBatabii]

Or am I standing still Beneath the darkened sky Or am I standing still With the scenery flying by Or am I standing still Out of the corner of my eye Was that you Passing me by?

[@FakeReallity1]

Best episode I’ve seen.

[@AndreaDingbatt]

Okay, My Minds just Blown!! BOOM 🤯💥!!

[@LinthusOriginal]

I always bring up in conversation about those kind of things that "we are always moving at 1 'second' per second in space-time"

[@RudeMcRude]

I think it would be better to tell people how 'c' isn't the speed of light but the speed of causality, since Causality/Constant/celeritas are all valid representations for the letter c. Since nothing can travel faster than c, as in the effect can not happen before the cause, (The light doesn't turn off before you hit the light switch) Causality is the Constant Celeritas everything adheres to.

[@fraliexb]

Holy hell, I needed to take that edible before that one.

[@AnimilesYT]

I appreciate that you're using meters per second so no one actually has a good understanding of how fast it is

[@enadegheeghaghe6369]

What would you prefer? Football fields per second?

[@VictoriaEMeredith]

I almost had a two second period in which I understood the space-time equation. Then it faded and I’m confused again. But it gives me hope that with enough study, I COULD one day understand it. 😁

[@gordonthorn2049]

Yeah it's inward and outward. So time is matter scaled along with XYZ. The more XYZ, the longer the shape inward, the longer its timeline is. The more matter, the more complex the shape, the longer, and massive the particle is. 4d is static, 3d is intersecting relative wavefronts. Particles exist through their whole timeline, but are only matter at relative sizes along their shape. We exist next to particles past positions at sizes we can't detect, unless extreme lengthening of their shape such as extreme cosmic events registered as LIGO occourances. But yeah I think inward and outward is the missing link, a particle isn't only in 3d, just observed because an observation has to be an intersection of same sized wavefronts to be matter, so along a particles timeline during the scale differences of inward and outward, we find areas where they intersect with other particles to form matter. Nothing moves, all particles path inward are constant, matter only exists at wavefront intersections of relative size, and it's all one complete finished design. Why? I don't know but I guess maybe consciousness is a waypoint system for a 5th dimensional object to be forced to travel through the combined neural output wavefronts of brainwaves as a sort of trap, inescapable unless the brainwaves are distegulated due to sleep, drugs or death. Once this planned occourance happenes the 5th dimensional can exit the static path, at the specific time space expected.... How else would you travel in 4d without getting lost? Copy and paste into gpt for a refined version of this. It's interesting to hear it's take on this idea.

[@militantpacifist4087]

E=mc^2 is the faster you move through space the slower you move through time.

[@Blackmark52]

[9:45] (The bigger the distance, the shorter the time) Exactly opposite human intuition.

[@protocol6]

That c² isn't a velocity in that context, it's a unit conversion so its presence says nothing about your velocity in space-time. And that expression isn't a velocity, either, you'd need to normalize it. Divide both sides of ds²=c²dt²-dx² by d𝜏² (ds² is equal to c²d𝜏² or proper time converted to a length so you are left with c²=c²dt²/d𝜏² - dx²/d𝜏²) then you'll have squared velocities along each axis with respect to proper time. Now you have a squared unit vector where the norm is c which says the velocity is the speed of light in some arbitrary direction. Since the spatial directions are all zero, that means you must be moving at c in the time direction. That's equivalent to saying you are moving one coordinate second per proper second, just with that dimensionless value multiplied by the speed of light so it has familiar units that make sense. I'm using x as a 3-vector above just to avoid having to write out the y and z parts but it's a good strategy generally since Minkowski space-time is equivalent to hyperbolic quaternions (their norm is the Minkowski metric) and a split-complex number with a 3-vector as one of its coefficients is equivalent to a hyperbolic quaternion. Same sort of thing goes for regular Euclidean quaternions and complex numbers. It greatly simplifies both the notation and how you think about 4D algebra. The only tricky bit is you use the dot product instead of the cross product for the vectors in the real part of the result (so you get a scalar result) when you multiply two of them. Anyway, ds=||cdt+dxj|| is much nicer to work with is all I'm saying.

[@axle.student]

To the best of my knowledge 'ct' has a pseudo space dimension (so not real space). It's a misnomer to suggest that we are "Moving in space" at the speed of light. Causality 'c' has no spacial dimension. It's more like a maximum rate of change without distance. > It creates a lot of confusion within the core of relativity when we suggest that 'ct' is a real spacial dimension because we end up with weird concepts of living in some 4 dimensions of space like tesseracts. > Most will argue not, but I am very confident that the universe "actual" is 3D, and we need the time part to explain the slow latency of a photon or ability for objects to move is 3D space. We just need that 4thD 'ct' as a pseudo distance measurement so we can calculate how the universe looks to us as the viewers/observers. It's just a mathematical convention to remove the time blur when we look out and back in "photon time".

[@protocol6]

@@axle.student The problem with that interpretation is there is no one t axis. Every observer moving relative to other observers has their own t axis in the same 4D space-time. Your t axis could be someone else's x axis. Though, to be fair, one of you would have to be stuck at the event horizon of a black hole for that to happen so mostly it'll be their t axis is somewhere between your t and x axes. But you are correct that nobody is moving through space at the speed of light. What we are doing is always moving through space-time at the speed of light.

[@axle.student]

@@protocol6 I know this is a common interpretation. But I reject the idea that 4D is a physical universe. 4D is just an observer perspective or a mathematical measurement system. The common interpretation forces time to be an omnipresent spacial like direction, so making time "real" rather than just a measurement on a clock device. This conflicts with the same interpretation that also states that time is not "real". Both ways, or using either concept of time will still work from what I can tell, accept for quirks at an event horizon (or boundaries). . It's just a quirk/ambiguity that exist at the core of space time between Mr Einstein and Mr Minkowski in how distance/time is constructed or interpreted in the geometry. > I am not an indentured physicist so I am not going to attempt to assert that you are incorrect or anything. It just something that often comes out as a problem, but is rarely talked about and never explained anywhere that I can find. . It's one of those things that leads to this idea such as we are some how are "physically" moving moving through the universe at the the speed of light when at rest. It just means that the clock (measuring device) always appears to be turning. No one physically move anywhere when at rest in space. And a person at rest in space doesn't physically move in space time, only the clock turns.

[@MedievalMan]

Im so glad there is finally a common KZbin channel that gave credit to other scientists, besides overrated "Einstein" all of the time.

[@pascallavoie8417]

Wow, this video made me understand general relativity way better, thank you.

[@BK557SC]

This doesn't look like pbs space time?

[@KurtQuad]

It makes sense since for a traveler is going at say 99.9% the speed of light the distance between two points gets shorter. Say the length for the observer in the rest frame is 1,000,000 meters but for the traveler moving relative to the rest frame they've only traveled 42,885 meters. If you could conceivably get to those speeds it would make light years a heck of a lot shorter for those who are on the space ship. The more .99999's the shorter the distance. Just have to invent star trek like shielding and fusion power for your ship and we are good to go.....lol.

[@douglaswilkinson5700]

Fraser Cain interviewed an engineer whose team was looking at ways to achieve relativistic velocities. Only anti-matter has the energy density high enough to potentially propel a spacecraft to relativistic velocities.

[@KurtQuad]

@ well if we survive as a species long enough maybe that will be figured out in a few hundred years. I do like Fraser Cain. I need to find that episode.

[@TerryBollinger]

This was a nice intro to relativity. The graphic showing curved space for Minkowski is not right, though, since his space was flat. Curved space came many years later, and was entirely Einstein's idea

[@user-ge2hp3qw3j]

Hmm... This means an object with velocity C through XYZ dimensions has 0 velocity through time?

[@pdxmusl1510]

Basically. Its gets more nuanced with an expanding universe.

[@tomdibble8983]

If the d[xyz]^2 terms are all subtracted from the dt^2 term, then if d[xyz]^2 increase, doesn't dt^2 have to *increase* to keep ds^2 constant?

[@matthewuzhere]

yeah, i was confused about that as well.

[@oninoyakamo]

I've always wondered if time dilation is the reason the clocks in my cars over the years progressively fell out of time after being reset

[@jerrodplummer6850]

Here's the real kicker... people were doing whatever they wanted way before someone wrote down that we could say whatever we wanted and called it a rule.

[@Bonbon1948]

Light does not slow down when going through air or water. The speed stay the same. The light which is traveling at straight lines get bent in these situations and therefore the path is longer. So it takes more time. The speed does not change. Its fundamental to special relativity. TY Einstein ♥

[@mrmoose1599]

That what he said 😂

[@netkissa]

I read in a book that c is not actually the speed of light. C is the speed of massless particle and it just so happens that light is a massless particle. I do have to admit that c as the speed of causality (as mentioned in several comments) is far easier for me to understand.

[@pdxmusl1510]

Yep. Basically. C is not about light.

[@axle.student]

'c' is the maximum rate of 'c'ausality or change :)

[@jackielinde7568]

SciShow: How fast do you think you're going right now? Me: (Starts singing the Galaxy Song by Monty Python) SciShow: NOPE! You're wrong! Me: Awe...

[@culwin]

I think another way to say this, is that instead of thinking of speed relative to a minimum speed of 0, everything is relative to a maximum speed (c).

[@chaffejcarraway]

Just from that extraordinary intro I was like, "this is going to be a good one"

[@poshrat993]

Awful thing to say to someone who’s panic high

[@tcf70tyrannosapiensbonsai]

I understand less than before. You rush through a labyrinth with such confidence, as if You'd know it since birth. All of a sudden we travel on lightspeed, but we're still bound through gravity? My goodness

[@Mockturtlesoup1]

I've always wondered about us, or earth, or other things with mass, and why it doesn't violate any laws of relativity/physics to use a photon or other object traveling at light speed as reference frame A, and consider the earth to be reference frame B, with earth moving at light speed, and the photon being considered stationary.

[@rabidL3M0NS]

Does air and water really slow down light or is its path just longer and winding from being bumped around? Straight path vs windy path?

[@crewrangergaming9582]

If anything with a mass can't travel 100% of C in the space dimension, does that mean anything without a mass can also reach 99.999999..9% in the time dimension but not 100%, but we have not observed that? For light or mass less particles they always move 0% in time and 100% in space.

[@TimmMix]

wat.

[@BadgerMole_]

real

[@MBSfilms77]

real

[@best-fx-trader-2016]

C

[@MBSfilms77]

real

[@zionsemaan3127]

real

[@leonhardtkristensen4093]

I do not agree with this for the mere fact that length contraction will make every thing having zero length at speed c. I am believing in Louis de Broglie's postulation that every thing are waves and that matter or particles are an almost stationary collection of waves. As waves are oscillations I believe it is quite easy to prove by calculation that these oscillations slow down when they are moved. This then points to that time is a localised thing in every object. It also points to that there is an absolute zero speed just like that there is an absolute zero temperature. Sabine Hossenfelder basically said the same thing today in her video as she said that the background radiation has to be compensated for the earths movement.

[@MrRofl131]

I hate it when my favorite youtubers correctly guessing what I'm doing while wachting videos. It happens quite often lately. SuperGT also guessed correctly that is was trying to sleep, and now on the toilet.

[@tinycnyc]

It's like having a certain amount of energy and when you start moving around in space energy gets used from the time

[@philosophical.traveler]

I watched a video recently that discussed the fact that tone is just a result of percussion being sped up to the point that humans perceive it as as a continuous tone. Is it possible that time actually is a fourth dimension of space but we move so quickly through it that we experience it differently than the other dimensions of space?

[@stevehorne5536]

Warning - possible complete misunderstandings and fallacies follow... There's another sense where everything is traveling at (at least) the speed of light. The universe is expanding, and the expansion is accelerating. For objects far enough away, the distance between you and that object is at least the speed of light. As a result, the light you're emitting now will never reach those objects and the light those objects are emitting now will never reach you. This distance defines the "visible universe". Relative to anything outside the visible universe, you're traveling at or faster than the speed of light. You can argue that this isn't real speed - space is expanding while you and the object each potentially remain still. But space isn't an object, and doesn't in itself define any frame of reference to measure either your or the objects velocity relative to. I don't know what this means, if anything - I don't understand relativity that well. But I think in essence, once something's outside your visible universe, you're causally disconnected from that thing, and it no longer makes sense to measure your movement relative to that thing. Though in some ways the edge of the visible universe seems to be an event horizon, similar to the ones you get around black holes - I think that means that e.g. if you observe an object very close to that edge, it will be red-shifted to the point that it's nearly black, and it will appear to be experiencing virtually no time. Actually, as the expansion is accelerating, objects close to the edge are accelerating away from us. I wonder how much acceleration that works out as - it would be interesting if it turned out to be the same as the inward acceleration of an object near the event horizon of a black hole, but outward.

[@KaliFissure]

Everything everywhere is always traveling at the speed of light. It's the RELATIVE speed of this part to that part which gives things their character. Time is a compact dimension. This is why there are limits. Limits of energy. Lambda and event horizon. Minima and maxima. The gradient from minima to maxima is gravity. And limit theorem dictates that the closure is between the limits, that the limits connect. In at event horizon, out in deep void. Quantum Cyclic Cosmology. Inevitable because geometry requires it. 🖖

[@JacquesMare]

Actually there's an easier why to come to the same conclusion. The spectrum of galaxies at the edge of the universe in every direction in space you look, gets redshifted as it speeds up with distance, and eventually out of our bubble of the observable universe . So, an alien looking back at us from across this bubble will see us too traveling, and then disappearing from the universe as we approach the speed of light..... all of this based only on observations of many countless galaxies at various distances displaying this curious phenomenon of increased speed away from the observer as the universe expands uniformly in all directions away from every observer anywhere in the universe.

[@grantbmilburn]

So we're all traveling through time at c, but if we want to travel through space as well, we have to steal from our c-ration, so to speak, thus slowing our progress through time. Hence the twin paradox, which I first encountered as a teenager, reading Heinlein's Time for the Stars.

[@NoxDiablo]

We all radiate light, so we all move at the speed of light swirling around each other. As we all are different waves of Light swirling in time