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).

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.

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

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

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!

A new perspective on understanding the speed of light

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.

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.

Thank you Nick Lucid!🌈

always happy to see a good video on relativity posted

That was one hell of a smooth transition

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

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.

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.

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

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

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

Good to see you in motion!

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

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.

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

Love the Eye of Sauron shout out...

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.

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

Loved this on Nebula ❤

Incredible video as always!

Great explanations as usual!

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 👨‍🔬👩‍🔬

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.

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!

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

Hard to imagine a world without the Cartesian coordinate system.

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

Yes! I have thought about it!

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

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

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!

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!

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.

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.

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.

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.

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

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.

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.

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.

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?

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

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

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

Brilliant 🤩

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.

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.

only seen 30 seconds and i already love this video!

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

Going off on a tangent about tangents.

1:15 had me rolling

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

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

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.

Man, Dwayne Johnson is really involved in relativity.

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

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!!

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.

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

Whoa dude this is deep

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).

I finished high school, went to university, and got married. I got two kids by the time this man posted his next video, but it was worth the wait

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

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

I remember learning about this before. Our total sum of movement adds up to the speed of c.

you explain nicely.

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

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

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

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).

Skill slot unlocked. +2 segue proficiency

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

6:51 "In relativity, the faster we see something moving, the slower we see its personal time pass" Here's what I don't understand. If you're the astronaut, then in your view, the rock's time is moving slowly. So one second for the rock is equal to several seconds for the astronaut. That means from the rock's perspective, the astronaut's time is moving really fast (many seconds pass for the astronaut while only 1 second passes for the rock). BUT that doesn't make sense, because from the rock's perspective, the astronaut is moving really fast and thus the astronaut's time should be moving slower.

It’s actually way more trivial. Speed (or frequency) is whatever you’re counting (milles, meters, ticks, seconds, etc) divided by a standard time unit, eg seconds. All matter travels through time at a speed of one second per second. If you measure your own speed through time, you’re actually measuring your own clock’s rate, which is always a trivial 1 (s/s). This is also the constant speed of the 4-velocity. Saying that the 4-velocity speed is ic, is technically the same, based on the idea that a time unit is an imaginary distance, like one second equals i lightseconds. It’s just a more complicated way of saying it. Personally, I prefer to think of it the other way around: time is real and spatial distance is imaginary time, so a lightsecond is an imaginary second and c = i.

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

How did I not discover this channel sooner

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

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. 😅

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.

Everything moves at the speed of light... ...except light.

Wow, didn't know the Rock has his own time.

I am experiencing my reality at the speed of light.

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

This is why we always measure light in a vacuum at the same speed. If we move faster through space in spacetime then we will move slower in the time dimension. More correctly, we're always traveling through time as fast as physically possible dependant on our velocity through spacetime.

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.

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