String theory postulates ten or eleven dimensions, only three of which we can “travel” in. Time is a fourth dimension that we experience “now” and can experience “the past” through memory, but we have no knowledge of “the future”.One could say that we traveling in only one direction on the time dimension, and cannot reliably control our transit through time. (Although when one is bored, time certainly approaches stopping!)The other six or seven dimensions are often referred to being “curled up” in a microscopic manner so that we cannot experience them. This is not something that is intuitive, and is tough to keep straight.
One alternative to envisioning these other dimensions as curled is to postulate a brane – a flat surface that is analogous to an infinitely large and thin piece of paper, but in two (or more) of the “other dimensions”. Any entity that inhabited a brane would have no or little knowledge of anything the might exist outside of the brane.
The existance of branes, facilitates string theory to describe gravity, and could be the source of missing “dark matter” and where particles in an adjacent brane reduce gravity to the weaker than expected effects of recent experiments.
