34 INTRODUCTORYbefore. Yet the theoretical structures now under investigation are not as simple
and economical as one would wish. The evidence is overwhelming that the theory
of particles and fields is still incomplete. Despite much progress, Einstein's earlier
complaint remains valid to this day: 'The theories which have gradually been
associated with what has been observed have led to an unbearable accumulation
of independent assumptions' [E8]. At the same time, no experimental evidence or
internal contradiction exists to indicate that the postulates of general relativity, of
special relativity, or of quantum mechanics are in mutual conflict or in need of
revision or refinement. We are therefore in no position to affirm or deny that these
postulates will forever remain unmodified.
I conclude this time capsule with a comment by Einstein on the meaning of the
occurrence of dimensionless constants (such as the fine-structure constant or the
electron-proton mass ratio) in the laws of physics, a subject about which he knew
nothing, we know nothing: 'In a sensible theory there are no [dimensionless] num-
bers whose values are determinable only empirically. I can, of course, not prove
that. .. dimensionless constants in the laws of nature, which from a purely logical
point of view can just as well have other values, should not exist. To me in my
'Gottvertrauen' [faith in God] this seems evident, but there might well be few who
have the same opinion' [E9].References
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E2. , The London Times, November 28, 1919.
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