  The linear mathematics of quantum mechanics gives many versions of reality
instead of the single version we perceive, with the perceived version chosen at
random according to a probability law. Because of these peculiarities, the
theory requires an interpretation to be fully understood. Over 50 years ago,
Everett proposed in his many-worlds interpretation that these characteristics
could be accounted for if the mathematics itself, with no collapse or hidden
variables, was carefully analyzed. We show this is incorrect; the linear
mathematics cannot account for the probability law. Thus the many-worlds
interpretation is not viable. Some mechanism, such as collapse or hidden
variables, must be added to obtain a satisfactory understanding of the physical
universe.
