4th Dimension Explained By A High-School Student

The video begins by illustrating dimensions using a folder analogy. A one-dimensional world allows movement only linearly (forward and backward). A two-dimensional world, represented by a flat surface, allows movement in multiple directions (up, down, left, right) and is composed of an infinite series of one-dimensional worlds. Our three-dimensional world, with depth, length, and height, is similarly comprised of an infinite series of two-dimensional worlds.

We perceive our three-dimensional world two-dimensionally. For instance, a sphere appears as a circle, with light cues indicating its three-dimensionality. Similarly, a two-dimensional organism would perceive its world in one dimension. A four-dimensional creature, perceiving our world in three dimensions, would be able to see through objects. Mathematically, if a 2D world is made of infinite lines and a 3D world of infinite planes, a 4D world is made of infinite 3D objects, but not in a simple stacked way.

Building upon the progression from a line (1D), to a square (2D), to a cube (3D), the video introduces the basic four-dimensional shape: a tesseract. A tesseract is conceptually made of four cubes connected perpendicularly and in parallel, with four lines connecting to each vertex. It's acknowledged that a true tesseract cannot be visually represented or imagined in our three-dimensional perception.

A common misconception is that the fourth dimension is time. However, time is not spatial, and assuming it's the fourth dimension implies it's special, which doesn't align with the pattern of spatial dimensions. Every dimension incorporates time. The video notes that movement can slightly affect one's experience of time, as seen with astronauts traveling near the speed of light.

Many physicists and mathematicians propose that dimensions are subtly curved. A curved 1D line would eventually form a circle. A curved 2D square would form a sphere. Applying this to our 3D world, a slight curve would eventually lead to a 4D universe, implying our 3D world is contained within a 4D world, which is then within a 5D world, and so on. This raises the question of whether there's an infinite number of dimensions.