Test of Einstein's Theory of Gravity Hits a Snag The longest-running project in the history of NASA will have to run a little longer. The $750 million satellite experiment known as Gravity Probe B was designed to test Einstein's theory of gravity. But small electrical charges have thrown off the test's precision instruments.
NPR logo

Test of Einstein's Theory of Gravity Hits a Snag

  • Download
  • <iframe src="https://www.npr.org/player/embed/9682351/9682352" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript
Test of Einstein's Theory of Gravity Hits a Snag

Test of Einstein's Theory of Gravity Hits a Snag

  • Download
  • <iframe src="https://www.npr.org/player/embed/9682351/9682352" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

MICHELE NORRIS, Host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Michele Norris.

ROBERT SIEGEL, Host:

NPR's David Kestenbaum was there.

DAVID KESTENBAUM: Testing Einstein is notoriously difficult, and this experiment has been in the works for so long that some of the scientists involved aren't alive anymore. Others are eligible for social security, like George Pugh. He's how old?

GEORGE PUGH: Let's see if I can figure it out. Well, I can tell you when I was born. I was born in January 1926.

KESTENBAUM: A weird thought - to think of space being dragged.

PUGH: Absolutely. And if you wanted to measure whether space was rotating or not, how on earth could you do it? Nothing to grab on to, how would you know it was rotating?

KESTENBAUM: On board, four super-precise gyroscopes, each with a spinning sphere the size of a ping-pong ball. The Guinness Book of World Records lists them as the most perfectly round objects ever manufactured. The project's spiritual and actual leader is Francis Everitt, a physicist at Stanford University.

FRANCIS EVERITT: My present age is 73. When I began on Gravity Probe B, I was 28 years old.

KESTENBAUM: Everitt now has gray hair down to his shoulders, some of which could be due to the job. In recent years, other scientists have found other ways to observe the subtle warpings of space predicted by Einstein. So for this experiment to be counted as a success, it has to do what it set out to: make very, very precise measurements. Over the course of a year, they hoped to be able to detect tiny shifts in the gyroscopes, less than one millionth of one degree.

EVERITT: That is the width of one of your hairs seen at a distance of about 10 miles.

KESTENBAUM: The team had planned to release its results around now, but there have been problems.

EVERITT: This is a prophecy that people make to you before you launch a spacecraft. Well, you're going to find that all things you knew were going to be impossibly difficult will work perfectly. And some things that couldn't possibly cause you any trouble will be the real issue.

KESTENBAUM: And there are issues. The results so far are 1,000 times less precise than what the team had designed for. Much of the unexpected trouble came from the gyroscopes. The spheres inside carried small patches of electric charge, which suddenly disturbed their motion. Everitt says he thinks the team will be able to subtract the disturbance and correct the data, improving the overall accuracy by a factor of a hundred.

EVERITT: I am completely confident. Of course, a critical person should ask, is my confidence justified?

KESTENBAUM: Everitt presented his results at the conference. One physicist, Eanna Flanagan from Cornell, sat with a notebook and a selection of fine-point pens for writing out equations. He is withholding judgment.

EANNA FLANAGAN: I'm hopeful that they can push to the levels of activity, which they said they could, because that was a very expensive experiment. A lot of resource went into it, it would be a shame if (unintelligible) it's essentially a failure. But I don't think it's disappointing yet.

KESTENBAUM: David Kestenbaum, NPR News.

Copyright © 2007 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.