NASA confirms Einstein's theory of relativity

The "Gravity Probe B" experiment, the American agency and physicists have proven that space and time can be distorted.

Einstein's general theory of relativity was verified by an experiment by NASA and American physicists who were able to measure with great precision the effects of the Earth's gravity on space and time. "Imagine our planet as if it were immersed in honey and it was turning on its axis in orbit around the Sun, the honey around it would deform," explains Francis Everitt, a physicist from Stanford University in California ( west), adding: "It's the same with space and time."

He conducted the experiment called "Gravity Probe B", which consisted of using four ultra-precise gyroscopes aboard a satellite launched in April 2004 to measure two key postulates of the famous theory published by Einstein in 1905. The first is the so-called geodetic effect, or the deformation of space and time around an object exerting a gravitational force. The second is the amount of space and time that an object affects by turning on itself. The satellite was pointed at a single star, IM Pegasi, while being in a polar orbit around the Earth.

Measurable Changes

If the earth's gravity had not affected space and time, the four gyroscopes placed in the satellite would always have pointed in the same direction. But these gyroscopes, drawn by earthly gravity, underwent measurable changes in the direction to which they pointed, confirming Einstein's theory of relativity.

A gyroscope consists of a wheel or a circular mechanical part rotating about an axis passing through its center and which, once thrown, tends to resist changes in its orientation. "The GP-B experiment confirmed two of the most important postulates in Einstein's theory of the universe, with implications for all astrophysics research," explains Francis Everitt. "The decades of technological innovations that are behind this mission will have lasting effects in research on Earth and space," he added.

Nobel prize

The advances made possible by the "Gravity Probe B" (GP-B) project initiated in 1959 by Leonard Schiff, then head of the Department of Physics at Stanford University, were used in the satellite positioning system (GPS). Technologies from the preparation of this experiment have also been applied to the NASA COBE (Cosmic Background Explorer) mission to study the electromagnetic radiation emitted shortly after the big bang, according to the theory. These measures have supported this theory. They were performed by John Mather of NASA who obtained for this work the Nobel Prize in Physics.

"The results of the GP-B mission will have an impact on the work of physics theorists for many years," said NASA astrophysicist Bill Danchi. "Any challenge to Einstein's general theory of relativity will have to get even more precise measurements than the remarkable precision produced by the GP-B," he said. The results of this experiment - one of the longest conducted by NASA - to which hundreds of researchers have worked, are published in the American journal Physical Review Letters.

Who are you satellite PROBE-B?

Gravity Probe B (GP-B, or GPB) is the name of an astronomical satellite operating between 2004 and 2005 and launched to measure the gravitational field of the earth with extreme precision in order to test the theory of general relativity 'Albert Einstein.

Positive results were announced in May 2011 by Stanford and NASA.

Gravity Probe B is a mission of NASA, with the help of the Department of Physics of Stanford University in the United States, and the company Lockheed Martin as the first subcontractor. This mission is considered the second gravity experiment in space after the successful launch of Gravity Probe A (GP-A) in 1976. The final report of the results obtained by Gravity Probe B is expected for the special session of the assembly General of the American Physical Society, April 14, 2007. The GP-B mission is the most accurate attempt to verify some of the predictions of general relativity.

The purpose of the mission is to test two still unverified predictions of this theory:

• It was planned to verify, with extreme precision, the tiny changes in the direction of rotation of four gyroscopes caused by the mere presence of the Earth. More precisely, gyroscopes had to measure how the gravitational field of the Earth was "trained" with it. This very low effect in the vicinity of the Earth is called Lense-Thirring (orgravitomagnetism) effect.
• The second prediction to be verified by GP-B is the geodetic precession. This effect, much more pronounced, is caused by the curvature of space-time due to the mass of the Earth.

The launch of GP-B was scheduled for April 19, 2004 at the Vandenberg Air Force Base in the United States, but was delayed 5 minutes before launch due to changing winds in the upper layers of the atmosphere. One of the peculiarities of this mission is that it had only one second of launch window because of the precise orbit required by the experiment. On April 20, at 16:57:23 UTC, the satellite was launched with gpb.jpgsuccess. It was placed in orbit at 18:12:33 UTC after passing over the South Pole. The mission lasted 16 months. The reason for the narrowness of the launch window is that the satellite orbit had to be done in a plane containing a star reference guide, IM Pegasi. This star was to be used as a reference to measure the deviation of the gyroscopes embarked. In order to do this, extreme precision had to be attained in locating the position of the star. For this purpose, the guide star had to radiate in the microwave domain so that it could be observed by VERB interferometry (VLBI), which is the most accurate technique to this day, but unable to operate, for technical reasons, in the visible range, but at longer wavelengths.

Analysts at Stanford and NASA announce on May 4, 2011 that the data received from Gravity Probe B confirms two forecasts by Albert Einstein.