Space-based experiment to test the theory of general relativity
"GP-A" redirects here. For other uses, see GPA (disambiguation).
Gravity Probe A
Diagram of the Gravity Probe A experiment[1]: 17
Mission type
Astrophysics
Operator
NASA
COSPAR ID
GRAVR-A
Mission duration
1 h 51 m
Apogee
10,224 km (6,353 mi)
Spacecraft properties
Spacecraft
GP-A
Launch mass
60 kg (130 lb)
Power
22 W
Start of mission
Launch date
18 June 1976 (1976-06-18)
Rocket
Scout[2]
Launch site
Wallops Flight Facility[3]
End of mission
Disposal
Decommissioned
Deactivated
18 June 1976 (1976-06-18)
Gravity Probe A (GP-A) was a space-based experiment to test the equivalence principle, a feature of Einstein's theory of relativity. It was performed jointly by the Smithsonian Astrophysical Observatory and the National Aeronautics and Space Administration. The experiment sent a hydrogen maser—a highly accurate frequency standard—into space to measure with high precision the rate at which time passes in a weaker gravitational field. Masses cause distortions in spacetime, which leads to the effects of length contraction and time dilation, both predicted results of Albert Einstein's theory of general relativity. Because of the bending of spacetime, an observer on Earth (in a lower gravitational potential) should measure a slower rate at which time passes than an observer that is higher in altitude (at higher gravitational potential). This effect is known as gravitational time dilation.
The experiment was a test of a major consequence of Einstein's general relativity, the equivalence principle. The equivalence principle states that a reference frame in a uniform gravitational field is indistinguishable from a reference frame that is under uniform acceleration. Further, the equivalence principle predicts that phenomenon of different time flow rates, present in a uniformly accelerating reference frame, will also be present in a stationary reference frame that is in a uniform gravitational field.
The probe was launched on June 18, 1976 from the NASA-Wallops Flight Center in Wallops Island, Virginia. The probe was carried via a Scout rocket, and attained a height of 10,000 km (6,200 mi), while remaining in space for 1 hour and 55 minutes, as intended. It returned to Earth by splashing down into the Atlantic Ocean.[4]
^"Fundamental Physics of Space - Technical Details - Gravity Probe A". NASA JPL. May 2, 2009. Archived from the original on September 18, 2011. Retrieved May 5, 2013.
GravityProbeA (GP-A) was a space-based experiment to test the equivalence principle, a feature of Einstein's theory of relativity. It was performed jointly...
GravityProbe B (GP-B) was a satellite-based experiment to test two unverified predictions of general relativity: the geodetic effect and frame-dragging...
GravityProbe may refer to: GravityProbeAGravityProbe B This disambiguation page lists articles associated with the title GravityProbe. If an internal...
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physics, gravity (from Latin gravitas 'weight') is a fundamental interaction which causes mutual attraction between all things that have mass. Gravity is,...
satellite GravityProbe B to a precision of better than 0.3%. Near a rotating mass, there are gravitomagnetic or frame-dragging effects. A distant observer...
refined by GravityProbeA and other experiments. Gravitational time dilation is closely related to gravitational redshift, in which the closer a body emitting...
Sample return: Parts of the probe return to Earth with physical samples Under Status, in the case of flybys (such as gravity assists) that are incidental...
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Archives Néerlandaises. 5: 253–78. Puri, A. (2015). "Einstein versus the simple pendulum formula: does gravity slow all clocks?". Physics Education. 50...
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gravitomagnetism. A group at Stanford University is currently[when?] analyzing data from the first direct test of GEM, the GravityProbe B satellite experiment...
improvement on these limits by a factor of about 100. The existence of gravitomagnetism was proven by GravityProbe B (GP-B), a satellite-based mission which...
in GravityProbe B during launch. Due to Earnshaw's theorem, no static arrangement of classical electrostatic fields can be used to stably levitate a point...
angular momentum of a gyroscope orbiting the Earth, as carried out by the GravityProbe B experiment. The geodetic effect was first predicted by Willem de Sitter...
the GravityProbeA satellite, launched in 1976, which showed gravity and velocity affect the ability to synchronize the rates of clocks orbiting a central...
to better than 0.5 milliarcseconds (1.4x10-7 degrees) over a one-year period" "GravityProbe B – Extraordinary Technologies" (PDF). Archived from the original...
in the 1970s included the Laser Geodynamics Satellite (LAGEOS) and GravityProbeA. In LAGEOS, laser beams from 35 ground stations are reflected by 422...
sensitive apparatus that rely on a perfectly uniform vacuum, such as Casimir force experiments and the GravityProbe B experiment. Critical apparatus...
This is a list of notable experiments in physics. The list includes only experiments with Wikipedia articles. For hypothetical experiments, see thought...
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