Newton, Einstein Lost in Space?
Beyond the edge of the solar system, something
has gradually dragged two of America's oldest space probes --
Pioneer 10 and Pioneer 11 -- a quarter-million miles off course.
Astrophysicists have struggled 15 years in vain to identify the
infinitesimal force at play. The Pioneer anomaly, as it is
called, throws a monkey wrench into celestial mechanics.
Slava Turyshev may have found the answer in
NASA's trash. Reconstructing decades of discarded spacecraft
data, the Russian-born astrophysicist and the private space
enthusiasts helping him say they believe they are on the verge
of solving a mystery of time and gravity that has perplexed a
generation of physicists and might have confounded Newton and
The anomaly officially materialized in 1988, 16
years after NASA launched Pioneer 10 toward the outer planets.
The 568-pound spacecraft had been designed to stay in radio
contact with Earth just 21 months, time enough for it to become
the first spacecraft to pass through the asteroid belt, the
first to fly past Jupiter and the first to visit the outer solar
system. The plutonium-powered probe, however, transmitted data
31 years until 2003.
As it sped through space, a specialist in
radio-wave physics named John Anderson at NASA's Jet Propulsion
Laboratory noticed an odd thing. The spacecraft was drifting off
course. The discrepancy was less than a few hundred-millionths
of an inch per second for every second of spaceflight,
accumulating year after year across billions of miles. Then
Pioneer 11, an identical probe escaping the solar system in the
opposite direction, also started to veer off course at the same
Ordinarily, such small deviations might be
overlooked, but not by Dr. Anderson. He monitored the
trajectories six years before calling attention to the matter.
"I'm a little like an accountant," Dr. Anderson said. "We have
Newton's theory and Einstein's theory, and when you apply them
to something like this -- and it doesn't add up -- it bothers
Not everything in the solar system adds up, of
course. The moon's actual orbit is off its calculated course by
about six millimeters a year. No one knows why. The standard
yardstick for length on an interplanetary scale, the
Astronomical Unit, grows by about seven centimeters a year.
Scientists have yet to agree on an explanation. At least four
recent planetary probes experienced such unaccountable changes
in velocity as they passed Earth, Dr. Anderson and his
colleagues reported this past March in Physical Review Letters.
None prompted the scrutiny given the Pioneer
anomaly. In hundreds of technical papers, Dr. Turyshev and
scores of other space scientists considered and eliminated most
mundane explanations, including fuel leaks, software bugs,
mechanical flaws, navigation errors, fading plutonium power,
planetary influences, the solar wind, even the effect of ocean
tides and local plate tectonics on the placement of ground
antennas. Others proposed more far-fetched scenarios: the tug of
dark matter, the accelerating expansion of the universe or a
breakdown of gravity's most fundamental laws.
Indeed, Dr. Turyshev at the Jet Propulsion
Laboratory and his colleagues around the world regard the
Pioneer probes as the largest test of Newton's law of gravity
ever conducted. By that axiom, refined by Einstein, any two
objects in the universe exert gravitational attraction on each
other proportional to their mass and affected predictably by the
distance between them.
"We would expect the two spacecraft to follow
Newton's law of gravity," Dr. Turyshev said, "but they in fact
fail to confirm Newton's law. If Newton is wrong, Einstein is
For 14 years, Dr. Turyshev sought a simpler
answer. He finally wondered whether heat radiating unevenly from
the probe might be the cause but lacked enough information.
Then, at JPL in 2002, he discovered 400 computer
tapes of Pioneer data gathering dust under a stairwell. In 2005,
he intercepted 70 filing cabinets of Pioneer engineering data on
their way to the junk heap at the NASA Ames Research Center, at
Moffett Field, Calif. The computer files held all of the Pioneer
mission data, but they were unreadable.
With no formal NASA funding, almost 6,000 members
of The Planetary Society, a space-exploration advocacy group
based in Pasadena, Calif., donated $220,000 to translate the
antiquated data into a digital format that a modern computer can
read. "This is not something that should be brushed away just
because it is old data," said society Executive Director Louis
Friedman. Victor Toth, a noted Canadian computer expert, donated
After six years of work, the researchers expect
to finish restoring the last data files next month. Based on a
partial analysis, Dr. Turyshev reported in April at a meeting of
the American Physical Society in St. Louis that at least 30% of
the force can be attributed to heat radiating from the probe.
"The rest is unknown," he said.
In the year ahead, Dr. Turyshev and his
colleagues plan to use the vintage data to create a computer
flight simulation of the two Pioneer missions with a precision
never before possible. That may finally lay it to rest.
"There is some hope that this would show a new
physics," Dr. Turyshev said. "With the Pioneers, we are
exploring uncharted territory."
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