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tions are extremely difficult to calculate, and therefore
only a part of them have been tested.
The third important element of the Standard
Model is the so-called Higgs boson,which is responsible
for generating the masses of all the other particles.
Although predicted by the model, the Higgs boson
has not yet been experimentally detected.
However, such a particle must exist if the Standard
Model is to remain consistent with itself.
Despite its astonishing success, the Standard
Model must be viewed as physically incomplete. For
example, it has so far proved impossible to explain
the force of gravity within its framework. Although
the model offers a good approximation of what happens
at energy levels and particle densities that are
relatively low, it must ultimately be replaced by a
better and more comprehensive description. The
Standard Model also contains a large number of
seemingly arbitrary “natural constants,” which it
cannot explain. The more comprehensive model required
must not only solve this problem; it must also
describe the early stages of the universe and unify
the three as-yet independent kinds of forces and
force particles into just one “primal force.” Physicists
expect that supersymmetry will have an important
role to play in any solution.
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