The braneworld model of the universe adds a fifth dimension
to Einstein’s general relativity spacetime model. The extra dimension in the braneworld model
is a (fourth) spatial dimension. Interestingly,
the braneworld model opens the door to (and perhaps requires) a varying speed
of light and parallel universes! Mathematical
physicists are working out plans to test for the presence of this fourth
spatial dimension based on the theory that while matter and light would be
limited to the standard three spatial dimensions, gravity would not. The hope is to locate objects which defy the laws
of gravity (such as Newton’s inverse square law) applied to a universe with just
three spatial dimensions.

Perhaps the whole world will one day realize what *Twilight Zone* fans have long known – Rod
Serling was a visionary!

[For those who somehow missed out altogether on either the
original TV series (1959-1964) or the perpetual airing of late night reruns of
the sci-fi TV classic *Twilight Zone*,
Rod Serling (narrator, host and most frequently the writer of the show) would open
each episode with the monologue:

**There is a fifth
dimension, beyond that which is known to man.**

It is a dimension as vast as space and as timeless as
infinity. It is the middle ground between light and shadow, between science and
superstition. And, it lies between the pit of man's fears and the summit of his
knowledge. This is the dimension of imagination. It is an area which we call
the Twilight Zone.

Actually, this was only the opening to *most* of the episodes in the first season. The opening monologue kept getting tweaked
after that first season.]

But why stop with adding just one extra spatial dimension to
a cosmic model? In fact physicists refer
to the braneworld model as a 4-brane model and refer to the model with *p* spatial dimensions as the *p*-brane model. (And yes, it’s pronounced **pea-brain**.)

http://en.wikipedia.org/wiki/Brane_cosmology

http://en.wikipedia.org/wiki/Brane

http://en.wikipedia.org/wiki/Spacetime

http://en.wikipedia.org/wiki/The_Twilight_Zone