#6. Why does the 'Cosmological Constant' have the value that it has?
Is it zero and is it really constant?
Until recently cosmologists thought the Universe was expanding at a
Steady clip. But recent observations indicate that the expansion may be
getting faster and faster. This slight acceleration is described by a number
called the cosmological constant. Whether the constant turns out to be zero,
believed, or some very tiny number, physicists are at a loss to explain why.
According to some fundamental calculations, it should be huge - some 10 to 122
times as big as has been observed. The Universe, in other words,
should be ballooning in leaps and bounds. Since it is not, there must be some
mechanism suppressing the effect.
If the Universe were perfectly supersymmetric,
the cosmological constant would become cancelled out entirely.
But since the symmetry, if it exists at all, appears to be broken,
the constant would still remain far too large. Things would get even
more confusing if the constant turned out to vary over time.