Alex McColgan

Now, adding extra directions of movement is what's needed to move things up from 1D to 2D to 3D.

So, in theory, we can predict what we need to do if we were to jump to 4D.

However, here we hit a snag.

While it's easy to draw a line that's perfectly perpendicular to a single other line, or to draw another line on top of those lines that is perpendicular to the two previous lines,

How would we draw a fourth line that's perpendicular to all three?

Surely such a thing is impossible.

Well, within 3D space, such a thing is impossible.

The best we can do is draw approximations.

For instance, it's possible to draw an approximation of a 3D shape on 2D paper by doing something like this.

These lines are all two-dimensional, but we look at this and our brain recognises that this is a picture of a 3D shape.

So, in the same way, we could probably do something similar to what a 4D object might look like using just 3D lines.

Mathematicians have attempted to do this, although their results tend to be a little confusing.

Although this is mathematically sound as a basis for a 4D object, I personally don't find my understanding of 4D space deepened by looking at it, so I won't focus on it in this video.

There is some evidence, however, that a fourth direction exists, and we are moving along it right now.

That fourth direction, or dimension, is time.

Einstein predicted this connection when he linked space and time into one unified space-time in his theories of relativity.

According to him, time and space are two parts of the same thing.

To me, this connects with 4D space very nicely.

Just as there is no real difference between the z and the x or y directions,

So too would there not be any difference between time and space if time is just another direction, albeit one that we can't see.