Alex McColgan

This has the effect of warping space in a way our brains don't really process well, but essentially means there's more and more space the further out you go, but exponentially so.

Other than that, travelling through this space obeys the same rules that travelling through 3D space uses, in terms of the physics rules involved.

Objects that start moving must be acted upon by another force or they will continue moving at the same rate.

Objects at rest remain at rest.

Conservation of momentum is maintained.

Now, let's imagine for whatever reason, there was some big expansion event in the past that sent us all moving in the upwards direction.

A big bang, if you will.

I wonder where one of those might have come from.

But this expansion was not simply in space, but in time too.

It's a 4D explosion.

We are now in motion, moving solely up at the top of this expanding bubble.

For now, we are not moving anywhere in space, we are simply moving forwards in time.

We travel consistently, and will continue to travel consistently until we are acted upon by another object or force.

But as we are new, and there is nothing but empty space above us, we are going to go up infinitely.

There's nothing up there to bump into.

Now, let's imagine for a second that we decide we no longer want to go straight up.

Let's try to change direction.

In physics, any change of direction is a form of acceleration.

This may not make much sense intuitively, but it becomes easier to understand if we split our vector into two components, our velocity in the x direction and our velocity in the y direction.

It then becomes easy to see that changing our direction comes about by decelerating with one of our values and accelerating with the other.