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A Space Time Vortex Around Earth - presented by Science@NASA
Would you believe Earth sits in the middle of a space-time vortex?
Einstein predicted this almost a hundred years ago, and it turns out
to be true.
On May 4th, 2011, researchers announced that NASA's Gravity Probe B
spacecraft has detected the vortex and its shape precisely matches
the predictions of Einstein's theory of gravity.
"The space-time around Earth appears to be distorted just as general
relativity predicts," says Stanford University physicist Francis Everitt,
principal investigator of the Gravity Probe B mission.
Time and space, according to Einstein's theories of relativity, are
woven together, forming a four-dimensional fabric called
"space-time." The mass of Earth dimples this fabric, much like a
person sitting in the middle of a trampoline.
If Earth were stationary, that would be the end of the story.
But our planet spins, and the spin should pull the dimple around into
a 4-dimensional swirl.
This is what GP-B went to space in 2004 to check.
The idea behind the experiment is simple: Imagine trying to spin a
toy top on the dimpled surface of that trampoline.
It's going to wobble, right?
Something similar happens when you try to spin a gyroscope in curved
space-time.
Its spin axis will drift or "precess." Gravity Probe B carried some
super-spherical gyros into Earth orbit to see what they would do.
In practice, this simple idea is extremely difficult.
According to calculations, the twisted space-time around Earth should
cause the axes of the gyros to drift by a tiny amount - really tiny.
It's like measuring the thickness of a sheet of paper held edge-on
100 miles away.
Even the slightest disturbance could ruin the experiment.
"We had to invent whole new technologies to make this possible,"
says Everitt.
The Gravity Probe B team developed a "drag free" satellite that could
brush against Earth's atmosphere without disturbing the gyros.
They figured out how to keep Earth's magnetic field from penetrating
the spacecraft.
And they created a device to measure the spin of a gyro - without
touching the gyro.
Pulling off the experiment was a big challenge.
But after a year of data-taking and nearly five years of analysis,
the Gravity Probe B scientists appear to have done it.
The gyros precessed; the vortex is real; and we are in it.
Einstein was right again.
For more information about the space-time vortex and what it means to
us on Earth, visit Science.nasa.gov