It's a century late, but Einstein's still right on time

Time, as we all know, is relative: good experiences seem to fly by, whereas
bad ones seem to drag on forever.
"After two hours, I looked at my watch," a reviewer of Wagnerian opera is
said to have written. "I found that 17 minutes had gone by."

In 1905, Albert Einstein wrote his own treatise on the relativity of time,
famously theorising that time speeds up or slows down according to how fast
an object is moving in relation to another object.

Thus, according to his hypothesis, a clock which is in motion ticks more
slowly than an identical clock which is at rest -- a phenomenon that
Einstein called time dilation.

In a study published on Sunday, the most accurate experiment yet into time
dilation has proven the great German physicist to be bang on target.

An international team of researchers used a particle accelerator to whizz
two beams of atoms around a doughnut-shaped course to represent Einstein's
faster-moving clocks.

They then timed the beams using high-precision laser spectroscopy and found
that, compared with the outside world, time for these atomic travellers did
indeed slow down.

"We were able to determine the effect more precisely than ever before," said
lead researcher Gerald Gwinner of the University of Manitoba in Winnipeg,
Canada.

"We found the observed effect to be in complete agreement."

The experiments, said Gwinner, confirm the technology aboard US military
satellites that provide the signals for the Global Positioning System
(GPS) -- the "satnav" network that is used as a navigational aid around the
world.


GPS satellites have precise atomic clocks on board in order to send out
synchronised signals that are then transcribed by trigonometry to give one's
position.

"GPS uses satellites to measure the position of objects on the ground, but
it needs to take into account the fact that the satellites themselves are in
motion at high speeds as they orbit the Earth," said Gwinner.

"Our test validates the theory used by the devices to compensate for the
satellites' motion."

The experiments took place at the Max Planck Institute for Nuclear Physics
in Heidelberg, Germany, and include researchers from that organisation, the
Max Planck Institute for Quantum Optics in Garching, and Mainz University.

http://www.physorg.com/news114010680.html

The findings were published online Sunday by the journal Nature Physics.

The first measurement of Einstein's time dilation took place in 1938, when
US scientists used the Doppler effect -- the change in pitch when a sound
and the person hearing it are moving apart or closer together -- as the
measuring tool.

Einstein's theory of relativity has become the basis for innumerable science
fiction tales, for it opens up the prospect of bending and distorting time.

If one of two identical twins were launched into space at very high speed,
when he returned home, he would be younger than his earthbound twin.

© 2007 AFP

-- 
Ken

"Buddhism elucidates why we are sentient."
"Buddhism follows thought throughout the Universe."
"Karma means that you don't get away with anything."