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PHVSICS OF THE IMPOSSIBLE
centuries because a direct test was impossible. In 1939 Einstein even
wrote a paper showing that such a dark star could not form by natural
means. The criticism was that these dark stars were inherently
untestable because they were, by definition, invisible. Yet today the
Hubble Space Telescope has given us gorgeous evidence of black
holes. We now believe that billions of them could lurk in the hearts of
galaxies; scores of wandering black holes could exist in our own
galaxy. But the point is that the evidence for black holes is all indirect;
that is, we have gathered information about black holes by analyzing
the accretion disk that swirls around them.
Furthermore, many "untestable" theories ultimately become
testable. It took two thousand years to prove the existence of atoms after they were first proposed by Democritus. Nineteenth-century physicists such as Ludwig Boltzmann were hounded to death for believing
in that theory, yet today we have gorgeous photographs of atoms. Pauli
himself introduced the concept of the neutrino in 1930, a particle so
elusive it can pass through blocks of solid lead the size of an entire star
system and not be absorbed. Pauli said, "I have committed the ultimate
sin; I have introduced a particle that can never be observed." It was
"impossible" to detect the neutrino, so it was considered little more
than science fiction for several decades. Yet today we can produce
beams of neutrinos.
There are, in fact, a number of experiments that will provide,
physicists hope, the first indirect tests of string theory:
• The Large Hadron Collider (LHC) might be powerful
enough to produce "sparticles," or superparticles, which are
the higher vibrations predicted by superstring theory (as
well as by other supersymmetric theories).
• As I mentioned earlier, in 2015 the Laser Interferometer Space Antenna (LISA) will be launched in space. LISA
and its successor, the Big Bang Observer, may be sensitive
enough to test several "pre-big bang" theories, including
versions of the string theory.
• A number of labs are investigating the presence of
PHVSICS OF THE IMPOSSIBLE
centuries because a direct test was impossible. In 1939 Einstein even
wrote a paper showing that such a dark star could not form by natural
means. The criticism was that these dark stars were inherently
untestable because they were, by definition, invisible. Yet today the
Hubble Space Telescope has given us gorgeous evidence of black
holes. We now believe that billions of them could lurk in the hearts of
galaxies; scores of wandering black holes could exist in our own
galaxy. But the point is that the evidence for black holes is all indirect;
that is, we have gathered information about black holes by analyzing
the accretion disk that swirls around them.
Furthermore, many "untestable" theories ultimately become
testable. It took two thousand years to prove the existence of atoms after they were first proposed by Democritus. Nineteenth-century physicists such as Ludwig Boltzmann were hounded to death for believing
in that theory, yet today we have gorgeous photographs of atoms. Pauli
himself introduced the concept of the neutrino in 1930, a particle so
elusive it can pass through blocks of solid lead the size of an entire star
system and not be absorbed. Pauli said, "I have committed the ultimate
sin; I have introduced a particle that can never be observed." It was
"impossible" to detect the neutrino, so it was considered little more
than science fiction for several decades. Yet today we can produce
beams of neutrinos.
There are, in fact, a number of experiments that will provide,
physicists hope, the first indirect tests of string theory:
• The Large Hadron Collider (LHC) might be powerful
enough to produce "sparticles," or superparticles, which are
the higher vibrations predicted by superstring theory (as
well as by other supersymmetric theories).
• As I mentioned earlier, in 2015 the Laser Interferometer Space Antenna (LISA) will be launched in space. LISA
and its successor, the Big Bang Observer, may be sensitive
enough to test several "pre-big bang" theories, including
versions of the string theory.
• A number of labs are investigating the presence of