Relativity tested on a shoestring budget
Justin Mullins

18:00 20 October 04

A NASA mission costing $600 million, which aimed to be the first to
measure an esoteric prediction of Einstein's theory of general relativity,
has been pipped to the post by a pair of scientists on a shoestring budget.

Einstein's famous theory says that a massive rotating body should drag
space-time around with it. The phenomenon - known as the Lense-Thirring
effect - would cause the axis of spin of a gyroscope orbiting the Earth to
go out of alignment by an angle of about 42 milli-arcseconds per year,
equivalent to the width of a human hair seen from a kilometre away.

To test for this effect, NASA and Stanford University physicists
conceived Gravity Probe B - which carries high-precision gyroscopes - in the
early 1960s but technical and financial problems delayed the launch until
April this year.

Meanwhile, Ignazio Ciufolini, a physicist at the University of Lecce
in Italy, and Erricos Pavlis from the Joint Center for Earth Systems
Technology in Baltimore have been quietly measuring the Lense-Thirring
effect using data from two NASA satellites that were sent up on an entirely
different mission.

The LAGEOS satellites, one launched in 1976 and the other in 1992, are
small shiny balls that reflect laser range-finding signals back to Earth.
The reflections, which reveal small changes in the orbits of the satellites,
are used to map variations in Earth's gravitational field.


Full Text at New Scientist
http://www.newscientist.com/news/news.jsp?id=ns99996552

--
Posted by
Robert Karl Stonjek

Robert Karl Stonjek wrote:

Relativity tested on a shoestring budget
Justin Mullins

18:00 20 October 04

A NASA mission costing $600 million, which aimed to be the first to
measure an esoteric prediction of Einstein's theory of general relativity,
has been pipped to the post by a pair of scientists on a shoestring budget.

There are two effects. Lense-Thirring frame dragging is by far the
larger and less controversial. Gravity Probe-B will measure it at
least ten times more accurately as a by-product of its main quest.

Einstein's famous theory says that a massive rotating body should drag
space-time around with it. The phenomenon - known as the Lense-Thirring
effect - would cause the axis of spin of a gyroscope orbiting the Earth to
go out of alignment by an angle of about 42 milli-arcseconds per year,
equivalent to the width of a human hair seen from a kilometre away.

Yeah, it's huge. Nobody doubted it would be there

[snip]

Full Text at New Scientist
http://www.newscientist.com/news/news.jsp?id=ns99996552

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