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since it was formulated in the early decades of the 20th century by
physicists such as Max Planck (1858-1947), Niels Bohr (1885-1962),
Werner Heisenberg (1901-76), Albert Einstein (1879-1955), and Er-
win Schrödinger (1887-1961). But quantum mechanics differs from
the much earlier formulations of Sir Isaac Newton (1642-1727), which
dominated physics for hundreds of years and continues to be used in
many applications. As noted in the sidebar on pages 20-21, large ob-
jects such as footballs and planets seem to behave in precisely predict-
able ways, described by Newtonian physics, but tiny particles such as
atoms do not.
Quantum mechanics allows researchers to understand particle be-
havior on an atomic and molecular level. The equations are accurate
but only provide probabilities for the state or path of any given particle,
rather than a rigidly determined quantity, as in Newton's laws. Yet if
researchers formulate the equations for a collection of interacting par-
ticles, such as chunks of matter, the probabilities as given by quantum
mechanics describe the overall behavior to a high degree of precision.
The problem is that the equations of quantum mechanics are difficult
to solve, and when there are many equations, as there must be when
formulating the behavior of a group of interacting particles, research-
ers must use computers to provide solutions. When the equations are
coded in programs that run on fast machines, the resulting computer
simulation—a computer program that mimics an event or process—can
give a detailed picture of the behavior of a piece of matter.
G. Malcolm Stocks, at the Oak Ridge National Laboratory in Ten-
nessee, and Yang Wang at the Pittsburgh Supercomputer Center in
Pennsylvania, have used quantum mechanics and computer simula-
tions to analyze the magnetic behavior of small bits of materials such
as iron-platinum alloys. The materials and properties these researchers
and their colleagues are investigating are related to the storage of infor-
mation. Computers, certain music players, and other devices store data
in binary digital bits—a 1 or 0—the value of which is often governed by
the direction of the magnetic field of a small region of magnetized ma-
terial on a plate or disk. The quantity of information that can be stored
in a given size of disk depends on how small can be each 1 or 0 region.
Even a modest computer today can store gigabytes (billions of bytes,
which are eight-bit chunks of data); yet as video and other data-rich
applications have increased—and the physical size of computers has
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