00:00Imagine that this folder is a dimensional plane.
00:04Now, assuming that it is no height and no depth, what would this mean?
00:08It would mean that it is a one dimensional world.
00:11So if, hypothetically, an organism was living inside of it,
00:14it would only be able to move in a linear path forward and backwards in a straight line.
00:19Now, if we go to the second dimension, we have two dimensions.
00:24We have width and we have length.
00:26So hypothetically, if an organism lived inside of here,
00:29then it would be able to move up, down, left, right, and anywhere else in between.
00:34And a two dimensional world is comprised of an infinite series of one dimensional worlds stacked upon each other.
00:42Just as our three dimensional world, which has depth and length and height,
00:48is comprised of an infinite series of two dimensional worlds.
00:52So, now that I have stacked many folders upon each other, we have three dimensions.
00:57We have depth, we have length, and we have width.
01:00Now, what happens if you keep going on from here on out?
01:03We would have a four dimensional world, but what exactly is a fourth dimension?
01:07In order to understand this, we need to understand how dimensions are perceived.
01:11We live in the three dimensional world, but despite that, we actually view things to be two dimensionally.
01:18Take a perfect sphere, for example.
01:20If you're looking at a sphere, it looks just like a regular two dimensional circle.
01:24The only way that you can tell it's an actual sphere instead of a circle is because of the hues of light down.
01:30So, just like in a two dimensional world, if an organism in the two dimensional world was looking upon a circle,
01:37the light would make it appear to be lighter at one end and darker at the middle.
01:43Also, if an object is moving closer and farther away from you, you don't actually perceive that it's getting closer and farther away.
01:51You see that it's getting smaller or larger, and then you assume that it's getting either farther away or closer.
01:58But, let's say that an object was to grow in perfectly equilibrium so that it was growing at the same speed that it was shrinking as you move it farther away.
02:08Then you would not be able to tell without any lights or if there were details on the object that it's moving or growing at all.
02:16You may have assumed that since we perceive things to be in two dimensions, that a two dimensional organism would see in one dimension.
02:25So, as we're watching this rubber band expand, as it moves farther away from this little organism in the two dimensional world,
02:34it does not actually perceive anything that's happening to it because it's growing at the same speed that it's moving farther away.
02:41But 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.
02:50The 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,
02:58just how we, three dimensional creatures, see things in two dimensions.
03:02So, in a way, we don't really see our world the way it truly is.
03:06A four dimensional creature, however, seeing our three dimensional world in three dimensions would be able to see through things.
03:13It 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.
03:24You would be able to see inside houses. You would be able to see inside of people.
03:28So, if a two dimensional world, a flat surface, is just made of an infinite amount of, uh, lines,
03:34then the 3D world is just made out of an infinite amount of planes.
03:39So, the 4D world, logically, is made out of an infinite amount of 3D objects.
03:45Though they're not just put together like, um, you would, like building blocks.
03:50That's, that's not how the 4D world is. That would just be 3D again.
03:55So, in order to understand this, we need to understand the logical progression of mathematics in our world.
04:02Imagine that this connects piece represents the first dimension.
04:07It's simply a straight line, which is basically what the first dimension looks like.
04:11And, if you add three more of these straight lines, and connect them so that adjacent sides are perpendicular,
04:21and opposite sides are parallel, then you have the basic shape of the second dimension.
04:26You have a square.
04:27Now, if you keep going from here, and you add four, add it so that there's a total of four squares,
04:33and all adjacent sides are perpendicular, and all opposite sides are parallel,
04:38then, you end up with, obviously, a cube.
04:44So, if you tried to keep going from here, and you would have a four dimensional basic shape,
04:52you would have a, what's called a tesseract.
04:55Now, I cannot show you a tesseract, but you need to understand that it's basically four cubes,
05:02that are within each other, that, um, have all adjacent sides perpendicular,
05:07and all parallel, and all opposite sides parallel.
05:12Yet, there are three lines, uh, four lines connecting to each vertex.
05:17So, a tesseract would look somewhat like this picture.
05:21Now, that, that's not exactly what it looks like, because this is a two dimensional depiction,
05:26and obviously, not all the lines are straight.
05:29So, I cannot show you what a tesseract actually looks like,
05:33because we cannot perceive things in the third dimension.
05:36You cannot even imagine what a tesseract looks like.
05:39You cannot physically, you cannot in your mind, picture the fourth dimension,
05:44or a fourth dimensional shape.
05:46And you can keep going on from the fourth dimension, even.
05:48You can go to the fifth dimension, the sixth dimension, the 71st dimension, it doesn't matter.
05:53Theoretically, there are an infinite amount of spatial dimensions.
05:57A common misconception of the fourth dimension is that the fourth dimension is time.
06:02Now, while some argue that by going forward and backwards in time,
06:07if you move forward the same distance and backwards the same,
06:10then you would end up in the same place you started, just like in the fourth dimension.
06:14And while that may seem logical, if you think about it, it really doesn't make sense.
06:18If you imply that the fourth dimension is actually time, well, first of all, time is not spatial.
06:24There's a difference between space and time, quite obviously.
06:27And assuming that all dimensions are according to a pattern, then that doesn't really make sense either,
06:34because saying the fourth dimension is time, every dimension has time in it.
06:40So that would mean that the fourth dimension is special in some way, which doesn't really make any sense.
06:46Another reason this doesn't make sense is that we very, very, very slightly travel through time whenever we move
06:54due to the distance that light takes to get to our body.
06:58Now, 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,
07:05then they would, and they went around in this impossible, nearly the speed of light spaceship for a few months,
07:13and then afterwards they returned to Earth.
07:15They would find that Earth had actually progressed a few years, so they had moved forward in time by moving that quickly.
07:24Another interesting concept involving the fourth dimension is that many physicists and even mathematicians
07:30may say that the dimensions are very, very slightly curved, because if you really think about it,
07:36nothing can be truly, absolutely infinite.
07:39So imagine that the first dimension, the line, is just very, very slightly curved, so that after a very long time,
07:48it will end up creating a circle.
07:52So, as suggests by many physicists, if you keep going in the same direction,
07:57then you will end up where you are, where you started, after a very, very long amount of time, obviously.
08:04And the same thing would happen to the second dimension, if it's just a square,
08:08and then you extend it very, very slightly in a curve, and it will eventually make a sphere.
08:14And the same thing happens in our dimension, except it will form a very, very slightly curved, um, third dimension,
08:22which will form a four-dimensional universe, basically.
08:26So what this kind of means is that our three-dimensional world is within a four-dimensional world,
08:32and the four-dimensional world is within a fifth-dimensional world, and so on.
08:36Now, I did say that nothing can be truly infinite, but if this is true,
08:40and a dimension is really within another dimension within another dimension within another dimension,
08:45then I'm implying that there's an infinite amount of dimensions, which is the only problem I really have with this theory.
08:51I'm not sure if it ever stops, or if infinity is really even possible. We don't know that.
08:59Thanks for watching my video, and I hope this gave you a better idea of what the fourth dimension is.
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