Alex McColgan

But before we get to that, we have to begin with one foundational idea.

Time is actually another dimension.

Now, before you double check that you haven't logged into some sci-fi channel by mistake, let's discuss what I mean by dimensions.

While in popular culture, different dimensions are often described as parallel worlds that are very similar to ours, yet subtly different, in this context, when we talk of different dimensions, we are referring to the dimensions of space, as in three-dimensional space, or 3D space, which may be far more familiar to you.

This is by no means trivial though.

3D space is all around you, it is the around you, and is very relevant to our topic.

Let's begin by making sure we understand the 3Ds and the relationships between them before we add the fourth D.

Broadly speaking, 3D, or three-dimensional space, simply refers to space that can be measured in three different perpendicular directions.

The perpendicular nature of these dimensions is important, but we'll get to that later.

Three-dimensional space is usually described as having height, width, and depth, and they all have 90 degree angles between them.

Simply put, objects like us that exist in 3D space can move left and right, up and down, and forwards and backwards.

We are comfortable with this kind of space.

Using this as our basis, it becomes much easier to imagine what we mean by 2D space and even 1D space.

To move from one space to another, all we need to do is remove or add an extra dimension of measurement or movement that must be a 90 degree angle from all previously existing angles.

So, 2D objects move in a plane that's bounded by the x and y directions, or the x and z directions, or the y and z directions, but not all three at once.

1D objects can only move either along x or y or z.

Imagine a person who lived in such a 1D world.

Their whole existence would be found either moving one way or the other.

All of reality would exist either to the left or to the right of them, and would appear as a singular dot.

They could not move or see in any of the other directions, and probably could not even comprehend such directions as even existing.