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Black Holes

Einstein's theory of relativity was first put forward in 1916 and was continually discussed throughout his lifetime. In contrast to Newton's ideas on gravity in which space and time were fixed, Einstein thought that celestial bodies would cause a warp in ‘space-time’ and that gravity itself is a result of these bodies moving in a curved space-time. However, the movement would be so small, that Einstein himself did not think that it could be shown in any experiment. NASA has now released research that shows this movement of gravity caused by celestial bodies is in fact about the width of a human hair.

95 years on from Einstein's initial proposal on gravity, NASA has just revealed the results of its current mission, ‘The Relativity Mission’, which was designed to prove two of Einstein's key theories of relativity. Launched in 2004 the mission used Gravity Probe B to measure shifts with ultra-precise gyroscopes spinning in orbit 400 miles away from earth whilst a ‘startracker’ focused on a single star, IM Pegasi.

The movement that was measured in the gyroscopes has proven Einstein's ideas on the impact of gravity from orbiting bodies, including the planet Earth, and even proving later theories on how much space and time they pull with them whilst they move! One of the Professors from Stanford university involved in the project described the effect as if “the Earth as if it were immersed in honey. As the planet rotates, the honey around it would swirl, and it's the same with space and time.”

The ‘simple’ experiment has been planned since 1964 but the hugely accurate gyroscopes, telescope and satellite used were launched in 2004. The results were beginning to return to be analysed in 2007, and the satellite was decommissioned in December 2010. The ping-pong ball sized rotors used in the gyroscopes took ten years to develop and are now recorded in the Guinness Book of Records as the roundest man-made objects in the world. Scientists both inside and outside the project are now discussing the impact of the discovery and the technology developed to carry it out as having a lasting impact on the whole of astrophysics. One contributor has suggested that it could even help with measuring quasars, the enormously powerful distant galaxies that have super-massive black holes at their centre.

Definitions
Geodetic Effect
The amount by which the earth warps the local space-time in which it resides.
Frame-dragging Effect
The amount by which the rotating earth drags its local space-time around with it.
Gyroscope
A disc with a heavy rim mounted in such a way that its axis of rotation can adopt any position. Once the disc is spinning, the rotation axis remains fixed with reference to fixed stars, which makes the gyroscope useful for determining movement away from a fixed course.

Watch Black Holes to find out more about Einstein's theories.