http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html
Scientists funded by the European Space Agency have measured the
gravitational equivalent of a magnetic field for the first time in a
laboratory. Under certain special conditions the effect is much larger than
expected from general relativity and could help physicists to make a
significant step towards the long-sought-after quantum theory of gravity.
Just as a moving electrical charge creates a magnetic field, so a moving
mass generates a gravitomagnetic field. According to Einstein's Theory of
General Relativity, the effect is virtually negligible. However, Martin
Tajmar, ARC Seibersdorf Research GmbH, Austria; Clovis de Matos, ESA-HQ,
Paris; and colleagues have measured the effect in a laboratory.
Their experiment involves a ring of superconducting material rotating up to
6 500 times a minute. Superconductors are special materials that lose all
electrical resistance at a certain temperature. Spinning superconductors
produce a weak magnetic field, the so-called London moment. The new
experiment tests a conjecture by Tajmar and de Matos that explains the
difference between high-precision mass measurements of Cooper-pairs (the
current carriers in superconductors) and their prediction via quantum
theory. They have discovered that this anomaly could be explained by the
appearance of a gravitomagnetic field in the spinning superconductor (This
effect has been named the Gravitomagnetic London Moment by analogy with its
magnetic counterpart).
Small acceleration sensors placed at different locations close to the
spinning superconductor, which has to be accelerated for the effect to be
noticeable, recorded an acceleration field outside the superconductor that
appears to be produced by gravitomagnetism. "This experiment is the
gravitational analogue of Faraday's electromagnetic induction experiment in
1831.
It demonstrates that a superconductive gyroscope is capable of generating a
powerful gravitomagnetic field, and is therefore the gravitational
counterpart of the magnetic coil. Depending on further confirmation, this
effect could form the basis for a new technological domain, which would
have numerous applications in space and other high-tech sectors" says de
Matos. Although just 100 millionths of the acceleration due to the Earth's
gravitational field, the measured field is a surprising one hundred million
trillion times larger than Einstein's General Relativity predicts.
Initially, the researchers were reluctant to believe their own results.
We ran more than 250 experiments, improved the facility over 3 years and
discussed the validity of the results for 8 months before making this
announcement. Now we are confident about the measurement," says Tajmar, who
performed the experiments and hopes that other physicists will conduct
their own versions of the experiment in order to verify the findings and
rule out a facility induced effect.
In parallel to the experimental evaluation of their conjecture, Tajmar and
de Matos also looked for a more refined theoretical model of the
Gravitomagnetic London Moment. They took their inspiration from
superconductivity. The electromagnetic properties of superconductors are
explained in quantum theory by assuming that force-carrying particles,
known as photons, gain mass. By allowing force-carrying gravitational
particles, known as the gravitons, to become heavier, they found that the
unexpectedly large gravitomagnetic force could be modelled.
"If confirmed, this would be a major breakthrough," says Tajmar, "it opens
up a new means of investigating general relativity and it consequences in
the quantum world."
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