Biology Reference
In-Depth Information
ers elsewhere since the war). By 1952, however, the laboratory had the
MANIAC (Mathematical Analyzer, Numerical Integrator, and Com-
puter), which had been constructed under the direction of Nicholas
Metropolis. Between 1952 and 1954, Metropolis worked with Enrico
Fermi, Stanislaw Ulam, George Gamow, and others on refi ning Monte
Carlo and other numerical methods for use on the new machine. They
applied these methods to problems in phase-shift analysis, nonlinear-
coupled oscillators, two-dimensional hydrodynamics, and nuclear cas-
cades.
35
Los Alamos also played a crucial role in convincing IBM to turn
its efforts to manufacturing digital computers in the early 1950s. It was
the fi rst institution to receive IBM's “Defense Calculator,” the IBM 701,
in March 1953.
36
When attempting to understand the motion of neutrons inside a hy-
drogen bomb, it is not possible to write down (let alone solve) the equa-
tions of motion for all the neutrons (there are far too many). Instead,
it is necessary to fi nd ways of summarizing the vast amounts of data
contained in the system. Goad played a central role in Los Alamos'
work on this problem. By treating the motion of neutrons like the fl ow
of a fl uid, Goad could describe it using well-known differential equa-
tions. These equations could be solved by “numerical methods”—that
is, by fi nding approximate solutions through intensive calculation.
37
In
other cases, Goad worked by using Monte Carlo methods—that is, by
simulating the motion of neutrons as a series of random moves.
38
In this
kind of work, Goad used electronic computers to perform the calcula-
tions: the computer acted to keep track of and manage the vast amounts
of data involved. The important result was not the motion of any given
neutron, but the overall pattern of motion, as determined from the sta-
tistical properties of the system.
When Goad returned to his thesis at the end of 1952, his work on
cosmic rays proceeded similarly. He was attempting to produce a model
of how cosmic rays would propagate through the atmosphere. Since a
shower of cosmic rays involved many particles, once again it was not
possible to track all of them individually. Instead, Goad attempted to
develop a set of equations that would yield the statistical distribution of
particles in the shower in space and time. These equations were solved
numerically based on theoretical predictions about the production of
mesons in the upper atmosphere.
39
In both his work on the hydrogen
bomb and his thesis, Goad's theoretical contributions centered on using
numerical methods to understand the statistics of transport and fl ow.
By the 1960s, Goad had become increasingly interested in some
problems in biology. While visiting the University of Colorado Medical
