As Universe Comes Undone, Electrons Cling More Tightly to Protons

Northeastern scientists question the fundamental constants of nature

BOSTON, Mass. In this topsy-turvy world of changing trends and
stormy alliances, two Northeastern University scientists propose an answer
to why even the fundamental constants of nature don’t seem constant
anymore. The bond between electrons and protons, called the fine
structure constant, or alpha, may not be constant and may have been
200,000 times weaker about ten billion years ago. This is a recent
astronomy finding that is hotly debated because it departs from the
standard model of physics and may point to modifications introduced by
string theory — the modern “Theory of Everything” which attempts to
unify all forces in nature.

According to Drs. Luis Anchordoqui and Haim Goldberg of the Department of
Physics at Northeastern University in Boston, Mass., this apparent tiny
change in alpha through the years may mirror the apparent accelerating
expansion rate of the Universe, as if electrons and protons clung ever more
tightly together as the Universe began to fly apart. The scientists
describe this process in a recent issue of Physical Review D: Vol. 68,
083513 (2003).

“The apparent change in the fine structure constant remains controversial,
partly because it stands in contrast to standard field theory, the basis of
all the successes in atomic and nuclear physics, in which this constant is
an unvarying input to all calculations,” said Anchordoqui. “We find,
however, that the apparent change agrees with a variety of different types
of observations.”

Light signals from exceedingly bright and distant galaxies called quasars
seem to indicate that the bond between electrons and protons was weaker in
the early universe. Light left these galaxies about 10 billion years ago and
thus reflects the state of matter (and the laws of nature) from that epoch.
This apparent change in the fine structure constant has been observed in
several independent measurements.

On Earth, however, studies of a natural nuclear fission reactor which
operated in Gabon two billion years ago reveal no change in the fine
structure constant, down to an accuracy of one part in ten million. Thus,
if the fine structure constant has changed, it did not do so evenly through
the years. Anchordoqui and Goldberg attempt to reconcile this discrepancy.

They propose that the apparent change in the fine structure constant is
coupled to “quintessence.” This is a theory of dark energy in which a
mysterious universal repulsive force, once weaker long ago, now dominates
over the force of gravity and is causing the universe to fly apart at an
ever-expanding rate. Anchordoqui and Goldberg worked with one particular
model of quintessence proposed by Drs. Andreas Albrecht and Constantinos
Skordis of the University of California, Davis, in 2000. They found that
their own theory of the fine structure constant, when viewed in the context
of this quintessence model, provides agreement between the quasar data and
the Gabon data.

That is, the fine structure constant was measurably weaker ten billion
years ago, but as quintessence assumed dominance about eight billion years
ago, the force between electrons and protons became stronger and “more
constant.”

The strength of the electron-proton bond from any matter created anytime
within the last several billion years is essentially indistinguishable.

The reason for this lies in the peculiar behavior of the Albrecht-Skordis
model, in which the quintessence field has all but ceased its variation
during the present era. The model is also consistent with landmark data
collected by the NASA Wilkinson Microwave Anisotropy Probe, which has
determined fundamental properties of the universe, such as its age and
shape, an announcement made in February 2003. Anchordoqui and Goldberg said
analyzing the light from even more distant quasars will reveal a steady
decrease in electron-proton binding strength.

Also, they said their theory could be tested soon with just a ten-fold
improvement in sensitivity in measuring the acceleration of different
objects in free fall. This is because a variation in the fine structure
constant would imply a variation of this type of acceleration as the
chemical makeup varied, a violation in the equivalence principle introduced
by Albert Einstein in his general theory of relativity. Two proposed
space-based mission will have this sensitivity: the MICROSCOPE mission from
France’s Centre National d’Etudes Spatiales, expected to fly in 2005; and a
NASA-ESA mission called STEP, Satellite Test of the Equivalence Principle.
“We may be able to test this model of a ‘changing’ fine structure constant
within a couple of years with instruments on satellites,” said Goldberg.
“Or, we could continue observing alpha in lab experiments for another
several billion years to see changes on the order of the quasar values. I’m
counting on the satellites.” For more information, refer to Anchordoqui and
Goldberg’s journal article, “Time Variations of the Fine Structure Constant
Driven by Quintessence,” available at http://arXiv.org/abs/hep-ph/0306084.