- MSNBC -- Is gravity broke? Or is it just the spacecraft? For whatever
reason, far-flung probes such as Pioneer 10 and 11 are showing an anomalous
slowdown effect. If the observations are correct, that could force a revision
of Einstein's theories.
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- THE EFFECT, reported Wednesday by New
Scientist magazine, has been showing up for years in analyses of telemetry
from Pioneer 10 and 11, which were launched in the early 1970s.
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- "It's just recently that it became
unambiguous, and we have no explanation for it," said John Anderson,
a planetary scientist at NASA's Jet Propulsion Laboratory and a principal
investigator on the Pioneer team.
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- Pioneer 10 is about 6.5 billion miles
away from the sun, and Pioneer 11 is more than 4.5 billion miles away.
Anderson explained that Pioneer 10 should have reached escape velocity
but readings from the spacecraft show that the probe is decelerating by
a tiny, constant amount.
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- "If this force continues, then eventually
it would just stop and fall back toward the sun," he said. "We
thought this thing would go off into interstellar space."
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- In fact, the Pioneer probes bear plaques
that would serve as a greeting to extraterrestrials who might happen upon
them.
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- The "drag" also appears to
affect the Ulysses spacecraft, which is in a polar orbit around the sun,
at a distance of about 490 million miles, Anderson said. An analysis of
data from the Galileo spacecraft, currently swinging around Jupiter, was
less conclusive, he said.
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- Anderson and his colleagues have ruled
out fuel problems, aerodynamic drag from the interstellar medium and the
effects of celestial bodies. Also, the anomaly hasn't been observed in
the movement of the planets or other objects of substantial mass in the
solar system.
-
- Currently, Anderson said, the prime suspect
in the mystery is "something in the hardware that we haven't found"
something that would systematically skew the data coming from the spacecraft.
But the spacecraft's operators haven't been able to find such a fault,
even though they've looked for years.
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- If the effect is real rather than a glitch,
astronomers and mathematicians would have to tinker with gravitational
theories that have held up for decades.
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- "It could have cosmological significance
somehow," Anderson said. "It could be distorting space and time
somehow."
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- For now, Anderson sees that as a "low-percentage"
possibility. He's prepared a formal paper on the anomalies that has been
accepted for publication by the Physical Review Letters. And he's looking
forward to new deep-space missions, such as the proposed Pluto-Kuiper Express,
which will have a better tracking system and thus could provide more clues
in the mystery.
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- "I think it will be something that
we'll be working on over the next decade," he said.
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