clifford_a-_pickover_surfing_through_hyperspacebookfi-org

6-
surfing through hyperspace
Figure 1.2 A fly in a tube has one degree of freedom and lives in a 1-D world.
(Drawing by Brian Mansfield.)
"Sally, you've got it. Likewise, a fly in a tube still lives in a 1-D world,
even if you curve the tube into a knot. It still has only one degree of freedom—its
motion back and forth. Even an intelligent fly might not realize
that the tube was curved."
You trip over a Rubik's cube that you had left on the floor and bump
into Sally's chair.
She pushes you away. "Ugh, you made me crush the fly." She tosses it
into a wastebasket.
You wave your hand. "It doesn't matter." You pause and return to the
discussion. "As I'll show you later, the space we live in may also be
curved, just like a twisted tube or a curved piece of paper. However, in
terms of our degrees of freedom, we are living in a 3-D world."
Sally holds her fist in front of you, as if about to strike you. "Let me
see if I get this. My fist can be described by three numbers: longitude,
latitude, and height above sea level. We live in a 3-D world. If we lived
in a 4-D space, I would have to specify the location of my fist with a
fourth number. In a 4-D world, to find my fist, you could go to the
correct longitude, latitude, and height above sea level, and then move
into a fourth direction, perpendicular to the rest."