Science:
Gravity Probe B, launched in 2004, has confirmed two
predictions derived from Einstein's theory of general
relativity. The satellite, which circled Earth from pole to
pole for 17 months, used gyroscopes to measure the geodetic
effect caused by Earth's mass creating a dimple in spacetime;
the circumference of a circle around Earth should be slightly
shorter than 2
π times the circle's radius.
Gravity Probe B measured the 2.8-centimeter decrement
to 0.25% precision. The satellite's measurement of the
frame-dragging effect, in which Earth twists the surrounding
spacetime as it rotates, fell short of expectations and
achieved 19% precision. The gyroscopes were geometrically the
roundest objects ever manufactured—but trapped charges in
their niobium coating made them far less precisely round
electrically. Those imperfections combined with ones in the
gyroscope's housing to create uncertainties that took five
years to correct. In 2004 Ignazio Ciufolini (University of
Salento in Lecce, Italy) and colleagues used data from less
expensive satellites,
LAGEOS and
LAGEOS II, to measure the frame dragging effect to 10%
precision. Whether
Gravity Probe B merely confirms those results, or has
additional importance, is a matter of perspective.
Skip Nav Destination
© 2011 American Institute of Physics
Gravity Probe B proves Einstein right Free
5 May 2011
DOI:https://doi.org/10.1063/PT.5.025283
Content License:FreeView
EISSN:1945-0699
Q&A: Tam O’Shaughnessy honors Sally Ride’s courage and character
Jenessa Duncombe
Ballooning in Albuquerque: What’s so special?
Michael Anand
Comments on early space controversies
W. David Cummings; Louis J. Lanzerotti