We are all moving at the speed of light

You've probably heard that nothing moves faster than the speed of light. But did you know nothing moves slower than the speed of light? We are all moving at the speed of light.

Einstein's special relativity forces us to think of time as a dimension we travel through - just like we travel through the three dimensions of space. The unit of measurement of this space-time is called the 'proper distance' and it supersedes both meters and seconds. Because meters and seconds are unified by the proper distance, speed loses it's meaning. We are only in control of the direction we travel through space-time. Fast moving objects appear to be ageing slowly - they are moving almost entirely through space and very little through time. Slow moving objects age quickly - they are moving almost entirely through time and very little through space.

Transforming between frames of reference moving at different speeds is very much like a rotation. In fact it IS a rotation - a hyperbolic rotation. In the context of special relativity however, it is called a Lorentz transformation.

Animation done using manim - a software created by Grant Sanderson of 3blue1brown.

[alexsloan]

Acceleration is the change in the angle, a force is what changes the angle, and mass is resistance to changing the angle

[semplar]

At first I thought it's going to be like "from perspective of light, we are moving backwards with the speed of light, so we can say we're moving at the speed of light relative to light itself", but no, this is super nice explanation!
So basically, spending energy for acceleration is exchanging time movement for spatial movement, and when we decelerate, we stop moving spatially and move in time direction! Of course time movement slows down by very unnoticeable little amount at everyday speeds.

[fahimullah]

The use of geometry to explain this was elegant. Keep the good work up! Expect to see more from you :)

[bitparity]

This video is an excellent supplement to the PBS space time videos. I think the notion of "we're always moving at exactly the speed of light" then suddenly makes more sense, and simultaneously explains why nothing else can accelerate to the speed of light.

[mospusthespider]

This is such an elegant explanation of this concept!

[Bassotronics]

Simple question. If something tries to travel at the speed of light, it gets ‘squashed’. But what about an object that’s spinning stationary almost at the speed of light. Does it get almost infinity small?

[MrOvergryph]

Facts: Light speed in a vacuum doesn't change. It is a constant value. Interesting notes about this video: 0:11 This video claims, "we are ALL moving at light speed (which is a constant value), " and 0:47 "Now, Alice and Bob are in a drag race. Alice is moving faster than Bob." And 1:57 "This is called time dilation and it's really only noticeable when 2 objects are moving at very different speeds. And Alice and Bob ARE moving at very different speeds." Title of the video: "We are all moving AT the speed of light." Okay. So Light speed is moving faster than Light speed. I think I got it now! I suggest changing the title of the video to, "Light is always moving at the speed of light, " because that's what you're actually saying in this video.

[liamgallagher]

Does this guy have another channel or something?? I really hope he starts posting videos again!! They're incredible.

[MinecraftMasterNo]

Note, the axis where the video is referencing the direction of travel is time. We do not move through space at the speed of light. Only time.

[russellstephan]

In other words, *_nothing_* travels through spacetime at a different rate than the speed of causality -- nothing is faster or slower.

[Chakshu]

This thought came to my mind and I searched youtube and only could find this video. Its so well explained.

[seb_]

That light sound -.-
Great Video anyway

[jebjosh]

Top quality content and great animations!

[Trashley]

Everything moves at the same speed. 1 second per second.

[optimusimperat]

your videos are very good. easy to grasp.please continue making more.


i wish to submit a challenging problem for you since you seem to be comfortable solving and explaining physical problems in a mathematical way, by using vectors. some mathematicians seem too allergic to touch physics problem:


assume a 2-spool cassette tape arrangement (coplanar), spool1 and spool2 are connected by a tightly wound inelastic tape of constant thickness without slack.
define spool1 to be the left spool centered at a fixed point1 and can rotate at an axis perpendicular to the plane of rotation
define spool2 to be the right spool centered at fixed point2 and can rotate at an axis perpendicular to the plane of rotation
define the minimum size of the spindle of the spool1 to be of radius r1 from point1
define the minimum size of the spindle of the spool2 to be of radius r2 from point2

define a fixed distance d between point1 and point2
define inelastic tape of constant thickness k
define an arbitrary fixed length of tape to be L
let the tape be wound around spool1 and spool2 and let the tape leave(wind/unwind) spool1 at some point p
let the tape be wound around spool1 and spool2 and let the tape leave(wind/unwind) spool2 at some point q
define the radius of the tape from spool1 at point p be R1 at some arbitrary time t
define the radius of the tape from spool2 at point q be R2 at some arbitrary time t
define Rmax to be the maximum radius of the spool when they are completely wound; Rmin = r1 or r2 if they are completely unwound
define a constant frictional coefficient that the tape makes to be f


initial conditions:
let spool1 be completely wound with tape; it shall be the driven spool; R1=Rmax at time t=0
let spool2 be completely unwound with tape; it shall be the driver spool; it is to rotate clockwise at a constant angular velocity w2; R2=Rmin=r2 at time t=0


constraints:
d > R1 + R2


define the vector V as the linear velocity of the tape at a point m between p and q
define an angle alpha at m as the angle made by the tape relative to the axis of the containing point1 and point2


define the angular velocity of spool1 to be w1
define the angular acceleration of spool1 to be a1
define the angular acceleration of spool2 to be a2


find:
V at any time t
what is the angle alpha at any time t
what is the angular velocity of alpha at any time t
what is the angular acceleration of alpha at any time t
calculate the length of L such that you can run your cassette for a total time of T; how many rotations theta2 will spool2 make to completely unwind spool1
what is the distance between p and q, is it always constant at any time t

[AbuSayed-ervs]

Thank you very much for this video.I already knew that as the norm of 4 velocity of anything is always “c”, but never found any video like that...

[aliengrey]

Objects in relative motion are also always moving in opposite direction at 180 degrees from each other. Just draw a line between Alice and Bob. See how it gets longer as they move? You could view it as them moving in opposite directions with their heads and bodies angled 45 degrees toward each other. If Alice rotated herself 45 degrees to her right and Bob rotated himself 45 degrees to his left, they would realize they were moving 180 degrees from each other on a straight line, assuming they were in outer space with no other objects around them for reference. Thus, the Lorentz grid would be rendered meaningless, because they're not on x and y axes, they're both on the same axis. Not only that, but if they had each been moving from the intersection of the x and y axes at say 300, 000 km/s, they're really each moving at slightly over 212, 132 km/s from the center of the straight line between them.

[Josdamale]

This helps with the Twin Paradox, because from A's perspective B is taking 2.2 sec compared to her 2 sec, while from B's perspective A is taking 2.2 sec compared to his 2 sec. So which is it?

I have not seen anyone thus far explain the Twin Paradox correctly, namely that the underlying explanation is that a THIRD perspective is required relative to both A and B.

If this third perspective is stationary in space with regards A, then B will be the one moving in relation to the three point of view system.

As the number of points of view increase, it becomes clear to see which object is moving relative to the others. But this is still relative to the local time and space relative proximities.

The universe is too large to determine a universal view on absolute position in time and space relative to the universal.

Nevertheless, every point of view is the centre of spacetime and the universe.

The point above is that it is not acceleration that resolves the twin paradox, but a third perspective stationary relative to either A or B.

Using acceleration already assumes a third perspective and which of the two is moving in terms of that relative three perspective system.

The third perspective moves the time lines of A and B off of the origin, and it is this then that allows the third perspective to determine which of the other two is moving relative to it and thus to each other.

When you perform the transformations between A and B in the coordinate system of the third perspective, you will see that relative differences then emerge between A and B, such that they will agree on their relative times when they meet again.

They will both agree as to the younger and the older.

Just as space requires at least three angles to form a closed object system, so time requires the same.

At least three perspectives are necessary to resolve relative spacetime.

[helifynoe]

A better use of geometry, is to combine with your usual Time and Space axes, a combination of a motion vector, and a length scalar. The motion vector represents your constant "c" motion within the 4D space-time environment. Tied to the end of that motion vector, is a scalar which represents the length of your object that is in motion within space-time. Change the direction of which the motion vector is pointing, and the objects length scalar will follow, and thus rotate. Using basic logic, one can then use this simple geometry to derive the special relativity mathematical equations, and complete this task in mere minutes. See for yourself if interested.

[crystal.oceanic]

I really like your videos! You have a clear way to explain things.