2001-07-14
Instead of saying one-ten-millionth of a second, wouldn't have been easier
to say 100 ns?
John
Keiner ist hoffnungsloser versklavt als derjenige, der irrt�mlich glaubt
frei zu sein.
There are none more hopelessly enslaved then those who falsely believe they
are free!
Johann Wolfgang von Goethe (1749-1832)
----- Original Message -----
From: "James R. Frysinger" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[EMAIL PROTECTED]>
Sent: Saturday, 2001-07-14 11:55
Subject: [USMA:14382] Distant clock
> Here's a clock that's even farther away than Boulder, CO. This is from
> Science magazine's Online pages.
>
> Jim
>
> 12 July 2001 7:00 PM
>
>
> Pulsar Precision Shows Space's Curves
>
>
> Albert Einstein could only imagine the effects of a gravitational field
> on a high-precision clock. But now researchers have turned his thought
> experiment into a reality, and the new observations vindicate Einstein's
> theory.
>
> The high-precision clock that made the new study possible is a rapidly
> spinning neutron star called a millisecond pulsar that's orbited by a
> compact white dwarf star. The pulsar, known as PSR J0437-4715, is about
> 450 light-years away.
>
> A research team led by astrophysicist Willem van Straten of the
> Swinburne University of Technology in Hawthorn, Australia, monitored the
> arrival times of the brief radio beeps emitted by the pulsar, allowing
> the team to figure out the shape and orientation of the orbit very
> precisely. They managed to measure the position of the pulsar in the sky
> to within one-hundred-thousandth of an arc second--the angle subtended
> by a pixel on your computer monitor as seen from a distance of some 8000
> kilometers.
>
> But the most important result, says van Straten, is their measurement of
> the so-called Shapiro delay. When the white dwarf is on the near side of
> its orbit, the pulsar's radio signals travel through the white dwarf's
> gravitational field. According to general relativity, space in a strong
> gravitational field is curved, so the radio pulses have to travel a
> slightly longer distance than you would expect, resulting in a delay in
> their arrival time of about one-ten-millionth of a second. The team
> reports this delay in the 12 July issue of Nature.
>
> Earlier studies just showed that Einstein's general relativity theory is
> self-consistent, says Frank Verbunt, a theoretical astrophysicist of
> Utrecht University in the Netherlands. "But in this case, it's a real
> independent test of the validity of general relativity," says Verbunt.
>
> --GOVERT SCHILLING
>
> --
> Metric Methods(SM) "Don't be late to metricate!"
> James R. Frysinger, CAMS http://www.metricmethods.com/
> 10 Captiva Row e-mail: [EMAIL PROTECTED]
> Charleston, SC 29407 phone/FAX: 843.225.6789
>
