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Einstein
Wins Again as 50-Year-Long Test Ends
by
Robert Piccioni
June 1, 2011
NASA’s Gravity Probe B (“GP-B”)
just announced the results of a 50-year-long project to test Einstein’s
theory of General Relativity. This may well be the longest running
scientific experiment in history.
This is a story of
heroic efforts to achieve the seemingly impossible, consuming vast
financial and human resources, with only modest success.
NASA spent at
least $750 million on GP-B, almost canceled it on seven occasions, and
finally cut off all funding three years ago. Money to complete GP-B was
raised from private individuals—an executive at Capital One and the
Saudi royal family, who have a lot more money than NASA.
Over the
half-century since GP-B was first proposed, several scientists spent
their entire careers on this experiment. More than 2000 contributors
witnessed the 2004 launch. Principal Investigator, Dr. Francis Everitt
of Stanford University, devoted 49 years to GP-B, and one of the “new”
guys, Dr. John Mester, who invested “only” 19 years, said: “We’re
basically done. None of us have a job anymore.”
Why devote so much
money, time, and effort to test Einstein’s theory?
It must be
admitted that GP-B, like the Charge of the Light Brigade, is more about
valor than reason. Other experiments, done in different ways, have
tested the same predictions of Einstein, consumed far less time and
money, and gotten results that are at least as valuable.
But the goal is
undeniably important. Relativity is one of two pillars of physical
science; quantum mechanics is the other. Everything else is based on
these two theories. Yet we know both are imperfect and not entirely
consistent with one another. Finding exactly where these theories fail
is essential to developing better theories.
Beyond pure
academic interest, science and technology are foundations of our
economy. Almost every product we buy relies on knowledge that didn’t
exist 100 years ago. These advances are incorporated into, used to
create, or used to transport nearly everything. As just one example,
the GPS system, now integral to our commerce and our defense, would be
worthless without General Relativity. We need to know just how much we
can trust Einstein’s theories.
GP-B tested and
confirmed two major predictions of General Relativity: spacetime
wrapping and frame-dragging. Both predictions were tested in Earth’s
gravitational field by precisely monitoring the rotation of gyroscopes
on a satellite in a polar orbit 400 miles above Earth.
Einstein said
space and time are curved (“wrapped”) by the presence of mass and
energy. Generally, the primary effect is that time flows more slowly
where gravity is stronger. Earth’s mass is quite small on a cosmic
scale; it wraps spacetime by only one part in a billion. In the
conditions tested, this wrapping changed the direction of the
gyroscopes’ axes by 1/500th of a degree per year. GP-B measured this
“precession” to 0.3% of its value, and precisely confirmed Einstein’s
theory.
Frame-dragging
(illustrated below) is the twisting of spacetime caused by a rotating
massive body. As the world turns (sorry) once every 24 hours, Earth
twists the surrounding space into a vortex. But space twists much more
slowly than Earth spins—only 1/90,000th of a degree per year. GP-B was
able to measure this effect to 19% of its value, again confirming
Einstein.
Sketch
of “frame-dragging”, spacetime being twisted by a spinning massive body.
GP-B scientists had hoped their measurements would have been 20 times
more precise. To achieve that, their gyroscopes had to be ten million
times better than any others ever made. The 1.5 inch gyroscope balls
are the roundest things ever made by man, deviating from spherical
perfection by less than 30 billionth of an inch. By comparison, an
equally round ball the size of Earth would have no hills or valleys
exceeding 8 feet. But even that wasn’t good enough. Microscopic bumps
on the balls and their housings created torques 100 times larger than
expected—“It was a horrible shock” said Everitt.
It took an extraordinary effort to understand and correct for these
imperfections, and reach a respectable result. Yet, scientists are
generally skeptical of experiments requiring so much “massaging” of raw
data—everyone prefers “cleaner” experiments.
Many other experiments have also confirmed the predictions of
Einstein’s General Relativity. A 1978 NASA experiment called
Gravity Probe A confirmed time wrapping to 7 parts in 100,000. An
Italian-American collaboration confirmed frame-dragging to 10%
precision, and with a new launch, they hope to improve their
measurement to 1% precision.
Einstein made precise predictions for phenomena that no one else had
even conceived of. After nearly 100 years, his theories of Special and
General Relativity have been confirmed by literally tens of thousands
of experiments—no deviations have ever been found!
And while GP-B will never be the most definitive test, “We honor the
charge they made.”
Regards,
Robert
* * * * * * * * *
* * * * * * * * * * * * * * * * * * * * * * * * * * *
* * * * * * * * * * * * * * * *
Dr Robert
Piccioni,
Author of "Everyone's
Guide to Atoms, Einstein, and the Universe"
and " Can Life Be
Merely An Accident?"
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