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
For more information about the space-time vortex and what it means to us on
Earth, visit Science.nasa.gov
Visit http://science.nasa.gov/science-news/science-at-nasa/2011/04may_epic/ for
the full story.