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Perseverence Is Paying Off for a Test of Relativity in Space
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By GUY GUGLIOTTA STANFORD, Calif. — For 46 years, Francis Everitt, a Stanford University physicist, has promoted the often perilous fortunes of Gravity Probe B, perhaps the most exotic, “Star Trek”-ish experiment ever undertaken in space. Finally, with emergency financial help from a pair of unusual sources, success is at hand.
Conceived in the late 1950s, financed by $750 million from NASA and launched into orbit in 2004, the Gravity Probe B spacecraft has sought to prove two tenets of Einstein’s theory of general relativity. The first, called the geodetic effect, holds that a large celestial body like Earth will warp time the way a rubber sheet stretches when a bowling ball is placed on it. The second, known as frame-dragging, occurs when the rotation of a large body “twists” nearby space and time; turn the resting bowling ball, and the rubber sheet twists. To measure these phenomena, Dr. Everitt and his Stanford team equipped Gravity Probe B with a special telescope attached to several gyroscopes. They pointed the telescope at a “guide star,” IM Pegasi, and then spun up the gyros with their axes also fixed on the guide star. If Einstein was right, the gyros would drift slightly over time to follow the space-time distortion. The Stanford team collected 11 ˝ months’ worth of transmissions from Gravity Probe B, but tiny unforeseen drift in the gyros fouled the results. Dr. Everitt had to ask NASA for extra time and money so his 11-member team could figure out how to scrub the data. Four painstaking years later, the team has confirmed the geodetic effect and put a credible frame-dragging result within reach. Nevertheless, NASA was forced to stop financing the project last May. This 11th-hour catastrophe might have been terminal, but Dr. Everitt, long known for his tenacity as well as his charm, had nursed Gravity Probe B through several near-death experiences over the years. To persevere into 2008, he had already won a $500,000 contribution from Richard Fairbank, the founder and chief executive of Capital One Financial and the youngest son of his old mentor, the Stanford physicist William Fairbank. Richard Fairbank stipulated that Stanford and NASA each match his contribution, and they did. But by mid-2008, that $1.5 million was running out. That is when Dr. Everitt turned to Turki al-Saud, vice president for research institutes at the King Abdulaziz City for Science and Technology in Saudi Arabia and a member of the Saudi royal family. Dr. Saud, who has a doctorate in aeronautics and astronautics from Stanford, arranged a $2.7 million grant. The work goes on. “I didn’t imagine I would ever visit Riyadh,” Dr. Everitt said. “We will need more money, but $2.7 million by itself is really helpful. We now have a clear end in sight.” The Gravity Probe B experiment was conceived at the dawn of the Space Age by the Stanford physicist Leonard Schiff and George E. Pugh of the Defense Department. Dr. Schiff brought William Fairbank into the project in 1959, and in 1962 Dr. Fairbank induced the British-born Dr. Everitt to come for a visit. Now 74, Dr. Everitt has directed Gravity Probe B ever since. While the experiment itself was relatively straightforward, the engineering demands were unprecedented. The theoretical distortion in space-time for the geodetic effect was 6,614.4 milliarcseconds per year; for frame-dragging it was only 14 milliarcseconds per year. A milliarcsecond is about one four-millionth of a degree of arc. To make measurements that fine using an object as large as Earth, the spacecraft’s gyros had to be virtually friction-free and unaffected by heat, magnetic fields or unpredictable movements. The pristine environment of space made the attempt possible. But success was not guaranteed. Arcane, often unprecedented technologies were needed. The four fused-quartz, Ping-Pong-ball-size gyroscopes, coated with the metal niobium, were the most perfectly spherical objects ever created by humans. A coffin-size lead “bag” shielded the gyros from Earth’s magnetic field. A large thermos-like container called a dewar contained 645 gallons of liquid helium to be cooled to within two degrees of absolute zero. The helium held the niobium coating at superconducting temperatures, so the metal could track the deviations in the gyros’ spin axis. By the time the 21-foot-long, 3-ton spacecraft was launched on April 20, 2004, Gravity Probe B had become a very expensive tool designed to prove something that many scientists over the years had come to accept as already proved by theoretical physics and some previous experiments. That argument has no heft with Dr. Everitt. “We are doing a measurement with a massive object, and this is valid,” Dr. Everitt said. “This is what the general theory of relativity says, and this is the experiment.” The mission, however, did not go according to plan. The niobium coating on the gyros and their housings was slightly uneven, causing tiny unpredictable electrical torques that made the gyros drift. The mission ended in 2005, but since then the Stanford team has been mapping niobium anomalies on each gyro, finding the patterns of distortion and subtracting the noise from the data. NASA had budgeted money for a year’s worth of post-flight data analysis, but Dr. Everitt needed a lot more time, and NASA financed the project through 2007. That, it seemed, would be the end. Richard Fairbank, whom Dr. Everitt had known since he was a child, thought differently. “Nearly 50 years ago, my father had talked with me about the integrity of a bold quest and never giving up,” Mr. Fairbank said. “I just felt that the project was on the 1-yard line.” The financing brought about by his contribution took the project into 2008, but in May, Gravity Probe B went before NASA’s senior review, where an independent committee of scientists rates continuing agency projects to determine financing priorities. “We ended up dead last,” Dr. Everitt said. That month, however, Dr. Saud visited Stanford and spoke briefly with Dr. Everitt. Saudi Arabia, which has built 12 small satellites, “was interested in forming partnerships” for future space missions, Dr. Saud said in a telephone interview, and has since done so with Stanford and NASA. Dr. Everitt met with Dr. Saud in London in July, and Gravity Probe B received $2.7 million. The team has forged ahead. In August, graduate students made a breakthrough in data analysis to bring the frame-dragging deviation within 15 percent of the predicted result. Dr. Everitt hopes to get it within 3 percent by mid-2010. The geodetic effect is currently within 1 percent of the predicted result and is expected to go even lower. “They fly the mission and have what seems like an insurmountable problem,” said Michael Salamon, program scientist for the Physics of the Cosmos Program at NASA and a staunch supporter of the project despite the senior review decision. “Then they do this. It’s spectacular, frankly, and when it’s done we are going to have a press announcement.”
Source: http://www.nytimes.com/2009/02/17/science/17gravity.html?_r=1
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