Concept of the dimensions

When in our daily lives, we talk about 2D or 3D, what do we really mean by that? When we describe the physical nature of the universe or our world, we also describe about dimensions. In schools, students learn about 2D, or 2 dimensional shapes and 3D shapes like cubes, cone, pyramid etc. What do they really mean?

Our world is made up of four dimensions, of which three dimensions are spatial or, related to space. The other one is distinct one of which I shall tell later in this article. In normal geometry which kids learn at school, the three spatial dimensions are called length, breadth and height.

All the spatial dimensions are perpendicular to one another. To understand the concept of the dimensions, we will use an example. Let us suppose our universe is made up of only one dimension (a spatial dimension). Then our world will be like a line which has an infinite length. That would imply that only the smallest particle in the universe can live there and can move forward or backward and if any organism existed there then it would be like a long thread moving in any one direction.

Now let us assume that the universe is of two dimensions. That means we add a dimension perpendicular to first one. Now the particle has a freedom to move sideways also. If we imagine this universe it would appear to us as a flat screen where everything is flat. In one of Stephen Hawking’s lecture, I found an interesting example he mentioned. Suppose an animal in a two dimensional want to swallow or engulf a food then it cannot because the food will cut through it. The animal is a flat thing in this world and no hollowness is present there so nothing can go inside the animal.

Now we think of a world of three dimensions. We need to add one more dimension perpendicular to the both the other dimensions. Now if we view to world in finite way we can understand it would look like a box. In which the particle can now move forward, backwards, sideways and now also upwards and downwards. Thus it seems to be like the world in which we live in. Now we understand the meaning of the three spatial dimensions of the world.

Now I shall tell you about the other distinct dimension. It is time. Time is also a dimension. It was thought to be an absolute quantity which was same for everyone but now we know that time is a relative quantity. Albert Einstein proposed this concept in his Special Theory of Relativity that time is relative quantity and that for all observers time was not the same. We know that time is part of a four dimensional entity -space-time.