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Thursday
Nov182010

The Spinning Carpet

According to the General Theory of Relativity, the space around a massive planet or star is distorted and curved due to the energy content of the planet or star. The distance between two fixed points in space changes when the two points find themselves in the vicinity of an astrophysical object such as the Earth; and this effect is what is perceived by us as Earth's gravitational pull. Things get much more interesting when an astrophysical object is spinning… The fabric of space is dragged around by the spinning object - pulling with it nearby probes. The effect is known as frame-dragging and is expected to be particularly dramatic near the surface of black holes. Near a spinning black hole - a rather common scenario - the space is spun so violently that a nearby spaceship, planet or star is forced to spin with the black hole, whether it wants to do so or not! This same frame-dragging effect is also present close to our spinning planet. But the Earth's gravitational pull is much weaker and the corresponding frame-dragging effect is rather subtle. Despite this, recently, a group of experimental physicists attempted to measure this phenomenon using a special satellite. 

The first video talks briefly about the general aspects of frame-dragging near a black hole. The video starts with a very interesting and somewhat related recent phenomenon involving a jet from a supermassive black hole blowing through another galaxy… The remaining three videos (they are 3 parts of a 25 minute long documentary) present a detailed discussion of the recent experiment that studied frame-dragging near the Earth's surface - the so-called Gravity Probe B experiment.

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