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This article originally published in
Everitt is 58; he wears his black and silver hair down to his shoulders, and he
sports a bushy Einsteinian mustache. Speaking in an authoritative British accent,
he says, "If you ask me to speculate-Will we confirm or will we deny general
relativity? -I must say I’m an experimentalist; all I’m interested in is the
truth."
Isn’t that rather too modest?
"Well, surely it’s the right kind of scientific modesty in this
circumstance," he replies. "If I were completely modest, or if any of us
were completely modest, we wouldn’t do an experiment of this kind. But on the other
hand, you know, we are undertaking a rather difficult enterprise, which seems
worthwhile from many different points of view."
In a nutshell, what the experiment will attempt to do is measure two effects
that Einstein’s general relativity theory predicts. That theory contradicts
Newton’s vision of gravity as a force instantaneously traversing great distances
and redefines it as a field that warps the space-time fabric. If space and time
are woven together the way Einstein envisioned, then the shape of that fabric
should be affected by the gravitational forces exerted by rotating bodies.
A comparatively small body like Earth won’t affect the space-time fabric
very dramatically; nonetheless, GP-B will try to determine if Earth is exerting
the two primary effects Einstein hypothesized. The first is the geodetic
effect, the degree to which a planet’s mass bends space-time. The second is
frame-dragging, the degree to which a planet’s rotation drags space-time around.
Both should be observable in fractions of a milliarc-second, aptly described
by one graduate student as "a gnat’s whisker of a measurement."
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