[FPSPACE] GPB and "redundant" science

LARRY KLAES ljk4 at msn.com
Sat Oct 23 12:25:27 EDT 2004


Since the money has already been spent and the satellite is in orbit, we might as well make use of its data.  Besides, in science it is always good to have more than one or two data points.

As for $700 million, the government wastes that much on a daily basis.  At least GPB is doing some real science.  And should I mention how much Americans spend on chewing gum every year?  $3 billion.  And we'll get to see some of it chewed during the World Series over and over. up close no less.  At least Game 4 will have the total lunar eclipse.  I wonder if the network will aim the cameras upward once in a while, if they even know about it?

Larry


Date: Fri, 22 Oct 2004 14:55:41 -0400 (GMT-04:00)
From: DwayneDay <zirconic1 at earthlink.net<mailto:zirconic1 at earthlink.net>>
Subject: Re: [FPSPACE] Monitoring 2 NASA satellites for 11 years
proves frame-dragging
To: fpspace <fpspace at friends-partners.org<mailto:fpspace at friends-partners.org>>
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-----Original Message-----
From: LARRY KLAES <ljk4 at msn.com<mailto:ljk4 at msn.com>>

*************************
Spinning Earth twists space
news at nature.com<mailto:news at nature.com<mailto:news at nature.com<mailto:news at nature.com>> October 20, 2004
*************************

"Frame-dragging," one of the last
untested predictions of general
relativity, has been confirmed by
the first reasonably accurate
measurement of how the rotating
Earth warps the fabric of space.
Researchers charted the path of two
NASA satellites over 11 years with
laser range-finders with the
precision of a few millimeters. The
effect dragged...

*********

This is what critics of Gravity Probe B claimed would happen--that before that spacecraft could return its results, the theory would essentially be proven by other research.  Ultimately, NASA spent $700 million on GPB.  As a colleague of mine once suggested, the people running the GPB project somehow proved to be excellent lobbyists, thwarting every effort to cancel it.




DDAY





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Message: 7
Date: Sat, 23 Oct 2004 11:48:36 -0400 (GMT-04:00)
From: DwayneDay <zirconic1 at earthlink.net<mailto:zirconic1 at earthlink.net>>
Subject: Re: [FPSPACE] Monitoring 2 NASA satellites for 11 years
proves frame-dragging
To: fpspace <fpspace at friends-partners.org<mailto:fpspace at friends-partners.org>>
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<14546796.1098546516873.JavaMail.root at waldorf.psp.pas.earthlink.net<mailto:14546796.1098546516873.JavaMail.root at waldorf.psp.pas.earthlink.net>>
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-----Original Message-----
From: Nick Watkins <nww62 at yahoo.co.uk<mailto:nww62 at yahoo.co.uk>>
Sent: Oct 23, 2004 9:49 AM

>Was "frame-dragging" the *specific* effect GPB was designed to test ? 

As I remember (I would have to look it up and I'm too lazy for that), GPB was designed to test for two effects and frame dragging was one of them.  The article below explains that this test was conducted several years ago with a 20% error rate, and was recently refined to 5-10%.  GPB should provide evidence down to about 1% accuracy.

As I recounted here awhile ago, GPB was initially conceived in the late 1950s by three naked professors in a Stanford swimming pool.  But it was not possible technologically until the 1990s.  However, the spacecraft requires extreme precision and due to some screwups, it was delayed multiple times, with costs rising.  It was only launched this year, which is several years late.  Its critics claimed a long time ago that by the time GPB was flying, they would probably already have proof, and the spacecraft was therefore redundant.  My own view is that we probably could have found a better space science project to spend this $700 million on.



http://www.washingtonpost.com/wp-dyn/articles/A52713-2004Oct21.html<http://www.washingtonpost.com/wp-dyn/articles/A52713-2004Oct21.html>

Theory of Relativity Evidence Found 
By Guy Gugliotta
Washington Post Staff Writer
Friday, October 22, 2004; Page A03 

By measuring variations in satellite orbits, scientists have found the first direct evidence of one of the hallowed tenets of Albert Einstein's theory of general relativity -- that the Earth and other large celestial bodies distort space and time as they rotate.

Researchers reporting yesterday in the journal Nature said improved satellite data had enabled them to show the effect known as "frame-dragging" with a degree of precision never previously possible.

"We improved our accuracy by orders of magnitude," said geodesist Erricos C. Pavlis of NASA's Goddard Space Flight Center in Greenbelt and the University of Maryland at Baltimore. "In a while, we should be able to do even better."

Scientists expect that the results of the experiment, by Pavlis and Ignazio Ciufolini of Italy's University of Lecce, will be reinforced by NASA's ongoing Gravity Probe B, a satellite mission designed to measure frame-dragging and another Einsteinian effect by a different method -- calculating gyroscope deviations over time.

"Gravity Probe B is less systematic, but will provide higher accuracy -- within a margin of error of less than 1 percent," said Michael Salamon, NASA's discipline scientist for fundamental physics. "What this research [yesterday's report] means is that GPB may not in fact provide the first direct evidence of frame-dragging."

In the early 20th century, Einstein theorized that the gravity of large bodies such as the Earth distorts space and time, much the way a bowling ball would stretch a rubber sheet held aloft on all four corners.

Frame-dragging occurs, he said, because the Earth's rotation pulls space-time along with it. Salamon likened the effect to dipping a spoon into a cup of honey and turning it. Close to the spoon the honey twists, but the effect dissipates with distance.

Scientists have wanted to prove Einstein's theory since the dawn of the space age. Gravity Probe B, conceived more than 40 years ago, is measuring frame-dragging from a satellite by focusing a telescope on a distant "guide star" and measuring how the axes of gyroscopes deviate from their original positions pointing directly at the star.

Pavlis and Ciufolini used satellites in a completely different way. They closely tracked the orbits of LAGEOS and LAGEOS2, passive satellites covered with "retroreflectors" that reflect laser beams from ground stations, giving precise measurements of distance from the station to the satellite.

The satellites' orbits are slightly distorted -- not perfectly circular or elliptical -- because irregularities in Earth's surface jog them. But even after subtracting this surface-caused "noise," the researchers were still left with orbits that deviated slightly from what they should have been. The difference, they said, reflected frame-dragging.

"The satellite orbits are not perfect because the Earth is not perfect," Salamon said. "So subtract them out, and what you're left with are the effects of space time. The results are better with two satellites, and three would have been even better."

The key to the experiment's success was better data on Earth's gravity field -- a better map of the Earth-induced orbital distortions. This information, collected by another new satellite, enabled Ciufolini and Pavlis to shrink their margin of error dramatically from the 20 percent they obtained from an earlier attempt.

"There was a tremendous amount of criticism then, and a lot of people said 20 percent was on the edge of being acceptable," Salamon said. "This result, between five and 10 percent, is a lot cleaner."


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