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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

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