We All Move At The Speed Of Light… Kind Of. 

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I feel so lucky to live in a time period where I can learn relativity from someone for free! You assume the watcher knows little but can explain it in such simple terms. I love your content so much, you are a gem to have on youtube.

One of the reasons I like this channel so much is the fact that complex ideas are explained in a simple way so you don't need much math or physics background to understand them.

I’ve been arguing this for years. Now I can just point people to this video instead of explaining it poorly myself 🙏

I had a thought about this recently. I tried to imagine what it would look like if something stopped moving through time. Let's say we have a box at rest. Even if it looks motionless, it's still moving through time because at one instant, it's there and at another instant, it's still there. But let's say it stopped moving through time. What would happen? One instant, it's there. The next, it isn't. And it's not like the box went somewhere else because that too would require motion through time. No, in this case, the box just up and disappears. It's literally erased from the universe, violating conservation of mass and energy, which isn't possible. Which is why everything must always be traveling through time, because otherwise conservation of mass/energy wouldn't be valid. It's also interesting how this line of thinking hints at the underlying connection between time and mass/energy conservation. Of course, we know it's really energy conservation that stems from time symmetry so it's kind of easy when we already know what to look for 😀

7:03 Note that when he said "a loss in temporal speed," what he meant is that as the rock moves faster, the proper time of the rock (𝜏) passes more slowly. However, since we defined the temporal speed as dt/d𝜏, the denominator of the derivative becomes smaller as the rock moves faster. This implies that both dx/d𝜏 and dt/d𝜏 approach infinity as proper time passes more slowly. What he intended to convey is that more time passes for us than for the rock. As the rock approaches the speed of light, both dt/d𝜏 and dx/d𝜏 approach infinity. This also means that you cannot use the Pythagorean theorem to add velocities. In spacetime, you have to use the Minkowski metric, which is: ds² = c² d𝜏² = c² dt² - dx² it means the total velocity is c² = c² dt²/d𝜏² - dx² /d𝜏² = c² (Uᵗ)² - (Uˣ)² if you define the temporal velocity in spatial unit then c² = (Uᵗ)² - (Uˣ)²

My son, 9, is gonna be so stoked there’s a new video! We watch these in bed at night before sleeping. Keep up the good work. (I’m excited too).

Always learn something worthwhile from your videos no matter how much advance knowledge I already had! This one had a slight vibe of your older videos in pacing which seems to blend nicely with your currently more visual content. Will re-watch one or two more times, as it went really deep. Love it!

This is the video i was looking for! I dont think ive seen anyone else explain this. I believe you mentioned it was coming soon. Thanks for the many explanations, one of my favorite science channels.

always happy to see a good video on relativity posted

When I saw the title, I thought it was about us moving at the speed of light relative to an observer on the cosmological horizon.

I heard about this idea a few months back and, while I’m sure I don’t fully grasp all the subtleties, it’s the first picture of the universe that makes me *believe* nothing can go faster than the speed of light. I accepted it before but always with a “…but what if…” tacked on. But if the speed of light is the speed everything is going in 4-space, then nothing can go faster than C in 3-space because there’s no place for that extra velocity to come from.

A friend told me about this and I've been waiting eagerly for a great explanation from yours truly

Thank you Nick Lucid!🌈

Good to see you in motion!

Another great video...I'll have to watch it again to really grasp it crazy for life!

So if we stop moving, we get to experience more time? Time to go lay down on the couch! 😁

I always get excited every time you upload a new video...

Everything comes back to circles and trig. There's no escaping it. Speaking of getting different sources of information, I have heard about this stuff about moving at the speed of light before, but it was great to finally hear your take on it as well.

8:59 .... DAYYYYYUM. He's not wrong, though.

Great video! Also, Ground News is amazing, thank you!

I liked this explanation a lot. I learned a lot of this through the in-variance of the interval concept. That and c = 1. But this gives a good perspective where it clears up who's time is it anyway.

Nice breakdown , seen the circle explanation on scienclic and you defo warm us up to that from a more beginner level . Awesome job on a really complex subject that is just there to shoot people down . I found it tricky to follow first time when I wasn’t watching the screen but your graphics really helped . Have a wonderful Xmas to you , the clones and your amazing wife 👨‍🔬👩‍🔬

A new perspective on understanding the speed of light

On another tangent… you mentioned your book. I need a copy, preferably signed! Thanks for continuing to make interesting content that expands our crazy minds!

I absolutely LOVE this relativity stuff, especially when we go TO THE TIMELINE!! Seriously, relativity does interest me the most...even if I am a geologist.

That was one hell of a smooth transition

Yep. Matt on Spacetime taught me that as matter I’m traveling through time at the speed of light.

Incredible video as always!

This is such a good explanation. I wish my undergraduate classes had shared this, and 4-d thinking had been introduced earlier. The explanations of spacetime diagrams were more confusing that enlightening, and these were foundational to understanding later work.

Great explanations as usual!

I picked this up in The Elegant Universe but Nick always has a great way of teaching

Videos about light are my FAVORITE 🎉 it can be so trippy and exciting!!!

I've been trying to tell people this for years, usually they just stare at me blankly, but now I can show them this video instead!

Science is Bonkers, thanks for all your great shows, Have a wonderful Christmas and New year. PEACE AND LOVE TO EVERYONE ❤❤.

Loved this on Nebula ❤

Love the Eye of Sauron shout out...

Yes! I have thought about it!

I see the edges of it, but I think I'm missing a few connections. Maybe the cake just needs to bake a little longer. These videos have opened my eyes. Thx!

Who can't love this guy?

Everything moves with the speed of light. We gain massful particles, by enclosing a massless particle, which is moving with the speed of light, into a confined space, like a quark or an electron. These particles act like a clock, where every so called “oscillation” of that massless particle is a “tick”. If we move the massful particle in space, the massless particle in it needs to move along, and less of its speed is spent on “ticking”. Therefore time slows down. And since all of the particles in our body is built like that, including our brain, everything slows down.

8:20 "If a factoid sounds simple, it's probably at least a little wrong." Occam's lesser-known electric razor.

That's a great way of thinking about spacetime. So much simpler than a ball bouncing as a train goes by 😉 Thanks for sharing 👍

So essentially, everything always moves at the speed of causality through space-time, and if you want to move faster through the spatial dimensions, that necessarily means you move slower through time, otherwise causality would be violated.

I used this explanation once during a bar argument. I was too many beers in to go into the Lorentz transformation, length contraction, infinite energy, etc, etc. I feel vindicated! Although I don't actually remember whether I won or lost the argument, or why we even got into the discussion in the first place. 😅

"How can you move at the speed of light??" Me: 'Cause it's the only speed there is, baby.

Best segway to the sponsor's message yet. I do not (yet) have an opinion on the content. I think three or four views will be needed before I "get" it. And reference to my copy of your book.

Man, Ground News are sponsoring every video in my timeline this month

Amazing as always!! I’ve always thought about what it would be like him. We had two or three temporal dimensions and what that would potentially cause we’re how it would make our physics equations and things completely different, as well as real world, stuff and technology.. very very neat stuff!!

only seen 30 seconds and i already love this video!

I was confused by the thought I should be traveling at the speed of light from the perspective of a photon, but since photons don’t experience time or space, such perspective shouldn’t exist.

you explain nicely.

Brilliant 🤩

"Because of a weird quirk of reality," is gonna be my new favorite answer I give to questions about basically anything.

Hard to imagine a world without the Cartesian coordinate system.

Going into this blind I’m guessing some percent of our total speed is invested in movement through time. Edit: friggin called it.

Fun fact: Rail Track Engineers refer to straight sections of track as ‘tangent track’!

New Asylum dropped?!?! Im here for it.

Hi. You are a genius. ❤the most complex stuff made simple. Never banal… ❤❤❤❤

Whoa dude this is deep

How did I not discover this channel sooner

Thank you for addressing this. Too often I see people asserting that lightspeed is a barrier that can be crossed, and that time travel exists on the other side of that line, because they have this fundamental misunderstanding of the nature of C. They don't conceptualize space-time as a singular structure and still try to talk about space, time, and speed/velocity as though they're all separate things. And these aren't just simple members of the science laity. These are actual science communicators and otherwise well educated people who should know better. There is only one other science channel I've seen address this concept, and I share their vid every time I see someone make the flawed claim that C is some kind of barrier that can be crossed if you just have enough kinetic energy.

Now all we need is a case for or against the video topic with regards to space-time expansion.

I enjoy looking at this as an intuitive explanation of how falling objects get their speed from gravity. A falling object looks like it accelerates for no "good" reason-- nothing is pushing on it; where is the energy for movement coming from? When we think of gravity as representing the curvature of spacetime, and conceptualize all massive objects as moving through spacetime at c, it becomes apparent that a falling object isn't getting its acceleration from "nothing"-- it's just changing the direction of its 4-velocity, from entirely through time to mostly through time and a little bit through space.

This video kind of blows my mind, because in trying to understand general relativity, I often imagined us traveling through time at the speed of light, and every time we gained some speed in the other 3 dimensions, is lowered out speed through time by the same amount.

What happened to your channel? You are one of my favorite science education RU-vidrs. You inspired me to start making pop-sci videos. But why is your channel now receiving fewer views, and I haven't seen your videos recommended by RU-vid for almost half a year?

Seeing that circular spacetime diagram at the beginning gave me one of the biggest "holy shit" moments ever

This is very interesting. Right before this video, I read an alternative theory about the expansion of the universe. He explains that the universe has an expansion rate of the speed of light. But then only in the 4th dimension. Thus the space we see is 3d, but as a surface on a 4d sphere. Not does not explain the expansion rate we have found in the 3 space dimensions. But if we use that 73 km/s per Mpc, we can use it to calculate the age of the universe. Which then ends up roughly the same as what scientists have discovered so far. Maybe this "out of the box" theory, if correct, can be linked to what you explained in this video.

Actually the faster an object moves through space the faster it also moves through time as spacetime is anti euclidean, meaning that the square of the spacetime distance is equal to the square of the distance through time minus the square of the distance through space. When an object moves faster through space it actually has to also move faster through time in order to maintain the same speed through spacetime, in contrast to what one would expect from normal euclidean geometry.

The whole, "generalize things to death" joke is _awesome!_

The accurate use of the verbal metaphor is much closer to the literal than you think, being a comment which begins from a single point of connection with the initial subject in a direction which will never again return to intersect the initial subject however far you follow it forwards or backwards

I've always thought of it as you travel the speed of light through time and space. The slower you move through one the faster you move through the other.

Going off on a tangent about tangents.

Not on the weekends, pal. ... That's when I move at the _speed of beer!_

I prefer just to think of velocity as the angle between two lines on a spacetime diagram (or rapidity as the hyperbolic angle).

So we can say we are all moving "fast, fast"

1:15 had me rolling

I love how the astronaut wasn't presumptuous "him"

Have you considered putting your catch phrases on your merch? I was looking for a "Fast fast!" t-shirt

Someone asked me what speed do time travelers move at and I was thinking about this idea of change in time being inversely related to speed to some extent. Sorta made sense for me intuitively, but makes it concrete

I don't think time without motion is even possible. Time is a measure or description of motion. Also, in terms of our physical brains time is a sensory and conscious perception that can only exist as a result of molecular motion.

Youve broken my mind and its gonna take time to fix it lol

Maybe a pov thing. Consider the twin paradox. Earl stays on earth, while his twin Rocky takes off in a rocket close to speed of light. They meet up in 10 years earth time. Earl has aged 10 years, but Rocky has only aged 5 years due to time dilation. So Rocky has traveled 10 years in only 5 years. He clearly was moving faster through time. He was also moving faster through space. They could not both have been moving at the same speed. Therefore they were not both moving at C.

That 4-V is an important clue in how gravity works. Give light a reason to slow and Time has to change with it, which changes the accelerations in all the subatomics in every bit of normal matter.

I know plenty of people who spend the majority of their 4-velocity temporally.

I am experiencing my reality at the speed of light.

You don't know how right you are. We are moving with the speed of light and light moves with a speed ... zero.

Aren't we traveling faster than the speed of light? From a distant galaxys perspective - we are at the edge of their visible universe - and as such, we are moving away from them faster than the speed of light. The space surrounding us is expanding and we are being carried along with it, faster than light speed.

Yep... I always try to explain this to my collegeas. But they look like they see a burning bush.

Although it's common to use the Special Relativistic equation that's in hyperbolic form c²t² - x² = c²τ² which leads to the imaginary coefficient i when you take the square root of the negative term, as Nick did, I think that's a mistake in this context. It makes more sense to subtract the negative term from both sides of that equation to arrive at the Pythagorean form of the equation: c²t² = c²τ² + x² Next, divide both sides by t² to get c² = c²τ²/t² + x²/t² That's more relevant in the context of the "speed" through 4-dimensional spacetime, because τ/t is the traveler's rate of aging from the perspective of the stationary observer (the floating astronaut), and x/t is the traveler's speed through 3-dimensional space from the perspective of the stationary observer. Together those two terms provide the traveler's "speed" through 4-dimensionsal Minkowski spacetime, from the perspective of the stationary observer. The c² coefficient in the c²τ²/t² term is just the conversion factor between the arbitrary units of time & length, and is equal to 1 if the units are chosen appropriately: c² = τ²/t² + x²/t² Note that it's a Pythagorean equation, where the square of a right triangle's hypotenuse equals the sum of the squares of the triangle's other two sides. The hypotenuse is the "speed" of the traveler through 4-dimensional Minkowski spacetime (which has the time dimension orthogonal to each spatial dimension, which means the triangle is a right triangle). So the square root of the left side is the traveler's "speed" through Minkowski spacetime... it equals c, the same as the speed of light through 3-dimensional space (and it equals 1 in the appropriate units of time & length). This equation works for any kind of traveler, including light. And it does NOT have the imaginary coefficient i that Nick mentioned, assuming the travel through 3-d space isn't faster than light. The equation also tells us the rate of aging of a traveler that's moving through 3-d space faster than light. It's not negative... it's the square root of a negative number, so it's imaginary. But it's unclear whether aging at an imaginary rate has any physical meaning, so it might be impossible to travel faster than light (in Minkowski 3-d space).

But spacetime is hyperbolic! (4 velocity)² = (temporal velocity)² - (spatial velocity)² = c² The magnitude of this 4 velocity is always c (using the (+,-,-,-) metric) So the faster you move through space, the faster you move through time.

Come on, the Marty McFly clip of "yeah i have a real problem with that" was right there

Love it when you show anti-intuitive concepts. Because all matter has to experience time, it can't ever put all it's velocity into space. Because light has to always travel at c, it can't ever experience time.

Can you make a video going in depth on how photons work?

For tachyons that travel faster than light, the arrow will point downward and time goes backward

Man, Dwayne Johnson is really involved in relativity.

The speed of light is really only limited by the speed of causality for which everything (seemingly?) happens instantly. But 'particles' that interact with mass (such as us) travel much slower than the speed of causality and therefore experience time. I tend to think of our current experienced reality as existing in slow motion relative to the actual 'speed of time' (speed of causality/light).

where is the music Nick 😭😭. They make your videos so iconic

Interestingly, you'll get very similar stuff if you switch to Planck's scale and assume the world works as in some kind simulation with pixels and clock ticks, where in each tick of a 'proper clock' you can move either by one pixel or one tick of local time.

Oh my goodness, time speed and space speed are traded for each other, oh my goodness the relationship is quadratic-hyperbolic, thats why things at the 100% speed of light do not really experience time, theyre like, at the limit