Einstein’s theories of relativity hold that space and time are
woven together into a four-dimensional fabric, and that a
weighty body like a planet or a star depresses that fabric, like
someone sitting on a chair or a trampoline. Gravitational
attraction is really just objects following the warped path.
What’s more, the rotation of a massive body would also affect
the fabric, so that a distant observer would perceive objects
close to a gravitational body as being dragged around. Think of
Earth sitting in a vat of liquid — as the planet rotates, the
liquid starts to swirl, too, and so does everything near the
Earth. If this is true, the axis of a gyroscope would change
when compared to the light from a faraway star. This is what
GP-B was designed to do. Orbiting 400 miles above the Earth in a
polar orbit, GP-B contains four gyroscopes made of quartz-
silicon spheres that are considered nearly perfect — they’re in
the Guinness Book of World Records. It has a telescope that
stared at a single star, IM Pegasi, whi