Communications of the ACM

I was chatting with Alex Wolf, vice president of ACM, at an Executive Committee meeting that took place shortly after the spectacular announcement of the confirmation of post-Big Bang inflationary expansion of the Universe—a notion that had been posited in 1980 by Alan Guth. Alex pointed out that scientific measurement and confirmation of the theory took 34 years to materialize. His observation struck a chord. Too often one gets the impression of tacit expectation that scientific research has to produce results within some predictable time or it is not useful or relevant.

I was immediately reminded of two other predictions that took some time to confirm. The most recent before the inflation result was the discovery of the Higgs boson that propagates the Higgs Field, conferring mass upon subatomic particles. Peter Higgs had predicted the existence of this particle in 1964. Nearly 50 years later, the Large Hadron Collider at CERN was able to measure clear evidence of the existence of a massive particle matching the Higgs boson’s anticipated characteristics.

The other is the discovery of the
pi muon or pion. From Wikipedia
( http://en.wikipedia.org/wiki/Pion) we
learn: “Theoretical work by Hideki
Yukawa in 1935 had predicted the
existence of mesons as the carrier
particles of the strong nuclear force.
From the range of the strong nuclear
force (inferred from the radius of the
atomic nucleus, Yukawa predicted
the existence of a particle having a
mass of about 100MeV. Initially af-
ter its discovery in 1936, the muon
(initially called the “mu meson”) was
thought to be this particle, since it
has a mass of 106 MeV. However, later
particle physics experiments showed
that the muon did not participate in
the strong nuclear interaction.

“In 1947, the first true mesons, the
charged pions, were found by the col-
laboration of Cecil Powell, César Lattes,
Giuseppe Occhialini et al., at the Univer-
sity of Bristol, in England. Since the ad-
vent of particle accelerators had not yet
come, high-energy subatomic particles
were only obtainable from atmospheric
cosmic rays. Photographic emulsions,
which used the gelatin-silver process,
were placed for long periods of time
in sites located at high altitude moun-
tains, first at Pic du Midi de Bigorre in
the Pyrenees, and later at Chacaltaya in
the Andes Mountains, where they were
impacted by cosmic rays.”
These are by no means the only ex-
amples of the delay between theoretical
prediction and practical discovery, but
they serve to illustrate the point that
it may take some time to validate the
results of theoretical research. In some
cases, the delay results from the lack of
instruments to discover corroborating
measurements. I am reminded of the
so-called Ice Cubea experiment in Ant-
arctica funded by the National Science
Foundation. It required an enormous
effort to construct the 5,000 sensors
buried deep in the ice and designed
to detect powerful cosmic ray neutri-
nos originating in galactic and extra-
a http://www.nsf.gov/news/special_reports/sci-
ence_nation/icecube.jsp
galactic supernovae while ignoring low
power solar neutrinos. This work was
rewarded by the detection of more than
two dozen extremely energetic neutri-
nos, the most powerful of which were
named after Sesame Street characters:
Bert, Ernie, and Big Bird. (Even serious
scientists have a sense of humor!)

The endless pas de deux between theory and practice is well illustrated by these examples. In some cases, measurement corroborates theory and in others it contradicts the theory. Once other possible sources of measurement error are discarded, scientists may be forced to alter theory to explain measurement. This is the essence of scientific principle: corroboration of theory with measurement, duplication of results by others to confirm observations, and revision of theory to explain measurement. That these confirmations or refutations may take decades to achieve is part of the long-term process of scientific investigation. As debates about the utility of scientific research ensue during annual budget-setting exercises, we would do well to remember the story of the Higgs boson, the pi muon, and the cosmic background measurements confirming inflationary expansion after the Big Bang. Sometimes it takes time, patience, and a lot of effort to establish and confirm scientific theory. It is worth the wait and the expense.

Vinton G. Cerf, ACM PRESIDENT Copyright held by Author.

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