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PHVSICS OF THE IMPOSSIBLE
In addition to higher dimensions, there is another parallel universe predicted by string theory, and this is the "multiverse."
THE MULTIVERSE
There is still one nagging question about string theory: why should
there be five different versions of string theory? String theory could
successfully unify the quantum theory with gravity, but there were five
ways in which this could be done. This was rather embarrassing, since
most physicists wanted a unique "theory of everything." Einstein, for
example, wanted to know if "God had any choice in making the universe." His belief was that the unified field theory of everything should
be unique. So why should there be five string theories?
In 1994 another bombshell was dropped. Edward Witten of Princeton's Institute for Advanced Study and Paul Townsend of Cambridge
University speculated that all five string theories were in fact the same
theory-but only if we add an eleventh dimension. From the vantage
point of the eleventh dimension, all five different theories collapsed
into one! The theory was unique after all, but only if we ascended to
the mountaintop of the eleventh dimension.
In the eleventh dimension a new mathematical object can exist,
called the membrane (e.g., like the surface of a sphere). Here was the
amazing observation: if one dropped from eleven dimensions down to
ten dimensions, all five string theories would emerge, starting from a
single membrane. Hence all five string theories were just different
ways of moving a membrane down from eleven to ten dimensions.
(To visualize this, imagine a beach ball with a rubber band stretched
around the equator. Imagine taking a pair of scissors and cutting the
beach ball twice, once above and once below the rubber band, thereby
lopping off the top and bottom of the beach ball. All that is left is the rubber band, a string. In the same way, if we curl up the eleventh dimension,
all that is left of a membrane is its equator, which is the string. In fact,
mathematically there are five ways in which this slicing can occur, leaving us with five different string theories in ten dimensions.)
PHVSICS OF THE IMPOSSIBLE
In addition to higher dimensions, there is another parallel universe predicted by string theory, and this is the "multiverse."
THE MULTIVERSE
There is still one nagging question about string theory: why should
there be five different versions of string theory? String theory could
successfully unify the quantum theory with gravity, but there were five
ways in which this could be done. This was rather embarrassing, since
most physicists wanted a unique "theory of everything." Einstein, for
example, wanted to know if "God had any choice in making the universe." His belief was that the unified field theory of everything should
be unique. So why should there be five string theories?
In 1994 another bombshell was dropped. Edward Witten of Princeton's Institute for Advanced Study and Paul Townsend of Cambridge
University speculated that all five string theories were in fact the same
theory-but only if we add an eleventh dimension. From the vantage
point of the eleventh dimension, all five different theories collapsed
into one! The theory was unique after all, but only if we ascended to
the mountaintop of the eleventh dimension.
In the eleventh dimension a new mathematical object can exist,
called the membrane (e.g., like the surface of a sphere). Here was the
amazing observation: if one dropped from eleven dimensions down to
ten dimensions, all five string theories would emerge, starting from a
single membrane. Hence all five string theories were just different
ways of moving a membrane down from eleven to ten dimensions.
(To visualize this, imagine a beach ball with a rubber band stretched
around the equator. Imagine taking a pair of scissors and cutting the
beach ball twice, once above and once below the rubber band, thereby
lopping off the top and bottom of the beach ball. All that is left is the rubber band, a string. In the same way, if we curl up the eleventh dimension,
all that is left of a membrane is its equator, which is the string. In fact,
mathematically there are five ways in which this slicing can occur, leaving us with five different string theories in ten dimensions.)