Ah, yes! Well I was going to tell you a bit more about Sigñor del Carpio, but I've just remembered my promise to share with you a way to visualize the Fourth Dimension.

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Step 1:

Right, make sure you're sitting comfortably. And in your mind, I want you to picture a floor with a white circle drawn on it. Let's make it outside. If you went to a school with a concrete playground: picture the playground, with a circle drawn on it.

Step 2:

Now, the idea is to materialise a worm, and place it in the centre of the circle.

You watch the worm for a while, and quickly realise that as soon as it started moving, it was moving towards the edge of the circle. It couldn't really do any different. The worm could only make use of two dimensions: he could move along the forward/backward axis, or the left/right one. And going forwards, backwards, left or right, from the centre of the circle the only way for him to go, is towards the edge of it.

Step 3:

Search in your mind and find a bird. Make it a nice and colourful one. Place it in the centre of the circle. Now watch.

The bird you've chosen is a very clever chap, and has latched onto the concept of your experiment. He assesses the situation, abandons the idea of walking around, and flies. Straight up. Away from the edge of the circle. That was the only choice he could have chosen. Moving any other way (besides downwards) he would have been moving towards the edge of the circle. In moving upwards, he made use of the Third Dimension available to him: he moved along the up/down axis.

Step 4:

Keep the same bird. Now, I want you to materialize a spherical cage around him. Make it out of metal bars so you can still see him from your position outside the cage.

He's hovering there in the middle of the cage, and whichever way he decides to move, he'll be moving towards the cage. The only way for him to move away from all sides of the cage at the same time, is for him to make use of the Fourth Dimension.