Image: Space-time warp
James Overduin, Pancho Eekels, Bob Kahn
An artist's conception shows Gravity Probe B measuring the curved space-time around Earth.
updated 5/4/2011 11:00:36 PM ET 2011-05-05T03:00:36

A NASA probe orbiting Earth has confirmed two key predictions of Albert Einstein's general theory of relativity, which describes how gravity causes masses to warp space-time around them.  

The Gravity Probe B mission was launched in 2004 to study two aspects of Einstein's theory about gravity: the geodetic effect, or the warping of space and time around a gravitational body; and frame-dragging, which describes the amount of space and time a spinning objects pulls with it as it rotates.

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"Imagine the earth as if it were immersed in honey," Stanford University physicist Francis Everitt, Gravity Probe B's principal investigator, said in a statement. "As the planet rotates, the honey around it would swirl, and it's the same with space and time. GP-B confirmed two of the most profound predictions of Einstein's universe, having far-reaching implications across astrophysics research." [6 Weird Facts About Gravity]

Gravity Probe B used four ultra-precise gyroscopes to measure the two gravitational hypotheses. The probe confirmed both effects with unprecedented precision by pointing its instruments at a single star called IM Pegasi.

If gravity did not affect space and time, the probe's gyroscopes would always point in the same direction while it was in polar orbit around Earth. However, the gyroscopes experienced small but measurable changes in the direction of their spin while Earth's gravity pulled at them, thereby confirming Einstein's theories.

"The mission results will have a long-term impact on the work of theoretical physicists," said Bill Danchi, senior astrophysicist and program scientist at NASA Headquarters in Washington. "Every future challenge to Einstein's theories of general relativity will have to seek more precise measurements than the remarkable work GP-B accomplished." [Top 10 Strangest Things in Space]

A long time coming
These results conclude one of the longest-running projects in NASA history. The space agency became involved in the development of a relativity gyroscope experiment in 1963.

Decades of research and testing led to groundbreaking technologies to control environmental disturbances that could affect the spacecraft, such as aerodynamic drag, magnetic fields and thermal variations. Furthermore, the mission's star tracker and gyroscopes were the most precise ever designed and produced.

The Gravity Probe B project has led to advancements in GPS technologies that help guide airplanes to landings. Additional innovations were applied to NASA's Cosmic Background Explorer mission, which accurately determined the universe's background radiation left over from shortly after the big bang.

The drag-free satellite concept pioneered by Gravity Probe B made a number of Earth-observing satellites possible, including NASA's Gravity Recovery and Climate Experiment. These satellites provide the most precise measurements of Earth's shape, which are critical for navigation on land and sea, and understanding the relationship between ocean circulation and climate patterns.

Gravity Probe B's wide reach
The Gravity Probe B mission also acted as a training ground for students across the United States, from candidates for doctorates and master's degrees to undergraduates and high school students. In fact, one undergraduate who worked on the mission went on to become the first female astronaut in space, Sally Ride.

"GP-B adds to the knowledge base on relativity in important ways, and its positive impact will be felt in the careers of students whose educations were enriched by the project," said Ed Weiler, associate administrator for the science mission directorate at NASA Headquarters.

Gravity Probe B completed its data collection operations and was decommissioned in December 2010. The probe's findings were published online in the journal Physical Review Letters.

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Interactive: Testing Einstein

Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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