English transcript

Imagine that this folder is a dimensional plane.

Now, assuming that it has no height and no depth, what would this mean? It would mean

that it's a one-dimensional world.

So if, hypothetically, an organism was living inside of it, it would only be able to move in a

linear path, forward and backwards, in a straight line.

Now, if we go to the second dimension, we have two dimensions: we have width and we have

length. So hypothetically, if an organism lived inside of here, then it would be able

to move up, down, left, right, and anywhere else in between.

And a two-dimensional world is comprised of an infinite series of one-dimensional worlds stacked upon each other.

Just as our

three-dimensional world, which has depth and length and height, is comprised of an

infinite series of two-dimensional worlds.

So this, now that I have stacked many folders upon each other, we have three dimensions. We have depth, we have length, and

we have width. Now what happens if you keep going on from here on out? We would have a four-dimensional world.

But what exactly is the fourth dimension? In order to understand this, we need to understand how dimensions are perceived.

We live in the three-dimensional world, but despite that, we actually

view things to be two-dimensionally.

Take a perfect sphere for example. If you look

at a sphere, it looks just like a regular two-dimensional circle. The only way that you can

tell it's an actual sphere instead of a circle is because of the hues of light on it.

So just like in a two-dimensional world, if a... organism in the two-dimensional world was looking upon a circle, it would... the light would make it appear

to be lighter at one end and darker in the middle.

Also, if an object is moving farther... closer and farther away from you, you don't actually perceive that it's getting closer and farther

away. You see that it's getting smaller or larger. And then you assume that it's getting either farther away or closer.

But let's say that an object was to grow in perfect equilibrium so that it was growing at the same speed that it was shrinking as you move it

farther away. Then you would not be able to tell, without any light or if there were

details on the object, that it's moving or growing at all.

You may have assumed that since we perceive things to be in

two dimensions, that a two-dimensional organism would see in one dimension.

So as we're watching this rubber band expand as it moves farther away from this little

organism in the two-dimensional world, it does not actually perceive anything is happening to it, because it's growing at the same

speed that it's moving farther away. But since we can actually see it from the three-dimensional world and perceive things

to be in two dimensions, we can see things for how they actually are. The reason that

the two-dimensional organism doesn't see things the way they really are is because

the two-dimensional organism sees things in one dimension, just how

we, three-dimensional creatures, see things in two dimensions.

So in a way, we don't really see our world the way it truly is. A four-dimensional creature, however, seeing our three-dimensional world in

three dimensions, would be able to see through things. It would be able to see

absolutely everything, just as we could see if there was

several organisms spread along a 2D... environment on your floor. You would be able to see inside houses, you would be able

to see inside of people. So if a two-dimensional world, a flat surface, is just made

of an infinite amount of lines, then the 3D world is just made out of an infinite amount

of planes. So the 4D world, logically, is made out of an infinite amount of 3D objects. Though they're not

just put together like you would...

like building blocks. That's not how the 4D world is. That would just

be 3D again. So in order to understand this, we need to understand the logical progression of mathematics in our world. Imagine that this

K'Nex piece represents the first dimension.

It's simply a straight line, which is basically what the first dimension looks like.

And if you add three more

of these straight lines and connect them so that adjacent sides are perpendicular and

opposite sides are parallel, then you have the basic shape of the second dimension. You have a

square. Now if you keep going from here and you add it so that there's a total of four

squares, and all adjacent sides are perpendicular and all opposite sides are parallel, then you end up with,

obviously, a cube.

So if you tried to keep going from here, then you would have a four-dimensional basic shape. You would have what's called a tesseract.

Now I cannot show you a tesseract, but you need to understand that it's basically four

cubes that are within each other that have all adjacent sides perpendicular and all parallel... and all opposite sides parallel. Yet there are three lines...

four lines connecting to each vertex.

So a tesseract would look somewhat like this picture.

Now that's not exactly what it looks like because this is a two-dimensional depiction,

and obviously not all of the lines are straight.

So I cannot show you what a tesseract actually looks like because we cannot perceive things in the

third dimension. You cannot even imagine what a tesseract looks like.

You cannot physically... you cannot in your mind picture the fourth dimension or a four-dimensional shape. And you can keep going on from the fourth dimension even. You can go to the fifth dimension, the sixth dimension,

the seventy-first dimension, it doesn't matter.

Theoretically, there are an infinite amount of spatial dimensions.

A common misconception of the fourth dimension is that the fourth dimension is time.

Now, while some argue that by going forward and backwards in time, if you move forward the same distance

and backwards the same, then you would end up in the same place you started, just like in the fourth dimension. And while that may seem

logical, if you think about it, it really

doesn't make sense. If you imply that the fourth dimension is actually time, well first of all, time is not spatial. There's a difference between space and

time, quite obviously. And assuming that all dimensions are according to a pattern, then

that doesn't really make sense either

because saying the fourth dimension is time, every dimension has time in it.

So that would mean that the fourth dimension is special in some way, which doesn't really

make any sense. Another reason this doesn't make sense is that we very, very, very slightly

travel through time whenever we move due to the distance...

that light takes to get to our body.

Now, if a group of astronauts were to get in a spaceship and they were to go very, very, very close to the speed of light, then they would... and they went around in this...

impossible, nearly the speed of light spaceship for a few months, and then afterwards they returned to

Earth, they would find that Earth had actually progressed a few

years. So they had moved forward in time by moving that quickly.

Another interesting concept involving the fourth

dimension is that many physicists and even mathematicians may say that the dimensions are very, very slightly curved. Because if you really think about it, nothing

can be truly absolutely infinite.

So imagine that a... the first dimension, the line, is just very, very slightly curved so that after

a very long time, it will end up creating a circle.

So, as suggested by many physicists, if you keep going in the same direction, then you will end up where you are...

where you started after a very, very long amount of time, obviously.

And the same thing would happen to the second dimension. If

it's just a square, and then you extend it very, very slightly in a curve, then it will eventually make a

sphere. And the same thing happens in our dimension, except it will form a very, very slightly curved

third dimension, which will form a four-dimensional universe, basically.

So what this kind of means is that our three-dimensional world

is within a four-dimensional world, and the four-dimensional world is within a fifth-dimensional world, and so on.

Now I did say that nothing can be truly infinite, but if this is true and a dimension is really within another dimension within another dimension within another dimension, then

I'm implying that there's an infinite amount of dimensions, which is the only problem I really have with this theory.

I'm not sure if it ever stops or if infinity is really even possible. We don't know

that. Thanks for watching my video, and I hope this gave you a better idea of what the fourth dimension is.