This article graciously provided by


Space Probe to Test Einstein's Views on Gravity, Time and Space
By Glennda Chui

Posted on Mon, Feb. 11, 2002

What may be the single most expensive scientific experiment in history, at a cost of $650 million and counting, is about ready to start after 40 years of preparation at Stanford University. It's been canceled and revived seven times, praised for its technological brilliance and reviled for its high cost.

In October, if its current run of luck continues, it will be blasted into space to test some of Albert Einstein's zany-sounding predictions about the nature of space, time and gravity.

``I think we'll know in two years whether it was worth it or not,'' said Richard Packard, a physicist at the University of California-Berkeley who has been involved in reviewing the project for the National Academy of Sciences.

``This is the most technologically difficult experiment ever done,'' he said, ``and if they pull it off, it will be a tour de force. There are so many things that are pushed far beyond where we thought the technology could go.''

The mission is called Gravity Probe B, and the best way to describe it is with superlatives.

It boasts:

• The longest development time in the history of the American space program --or, quite possibly, any space program. The National Aeronautics and Space Administration spent its first buck on the mission in 1964.

• The most nearly perfect spheres ever manufactured. They're about the size of pingpong balls, made of quartz coated with a thin layer of the metal niobium. If Earth were as smooth as these spheres, its tallest mountain would be just eight feet high.

• The four most precise gyroscopes ever made. A gyroscope is a wheel that spins on an axis; once it's set spinning, it will keep pointing in the same direction so long as it is not disturbed.

• A huge thermos bottle of shiny metal, officially called a Dewar, in which 607 gallons of liquid helium can be kept very, very cold -- at minus 456 degrees, just above absolute zero -- for two years.

All this is packed into a spacecraft that, fully loaded, weighs 7,500 pounds and measures about 2.8 meters around and seven meters high. The packing took place at Lockheed Martin Missiles & Space in Palo Alto. On Saturday, the whole contraption was lowered into a special NASA transport truck and driven, under heavy police escort, to another Lockheed facility in Sunnyvale, where it will be put through a final round of tests to make sure it can hold up under the rigorous conditions of space.

The goal of the mission is to test two predicted effects of Einstein's general theory of relativity that have never been directly measured.

Back up about three centuries to the time of Sir Isaac Newton. In his classic view of physics, gravity was a force that was transmitted instantaneously over enormous distances. A gravitational attraction exists between any two objects in the universe, no matter how far apart they are. If one of them suddenly blows up -- poof! -- the strength of that attraction changes in an eye blink.

This view of things stood for 200 years, until Einstein came along and proposed that nothing could travel faster than the speed of light. If he was right, how could gravity operate instantaneously?

In 1916, Einstein solved the problem. He proposed that space and time form a sort of fabric. A massive object, such as Earth, distorts the fabric, like a bowling ball plopped onto a soft bed. This warping of space-time is what we experience as gravity.

Two years later, a pair of scientists came to an even more startling conclusion: If a massive object is rotating, it should drag space and time along with it. This phenomenon, known as frame dragging, may underlie processes that power distant quasars, among other things. But near Earth, it would be very weak and hard to measure.

So how to detect it?

In 1960, two physicists -- Leonard Schiff of Stanford and George Pugh of the Defense Department -- independently suggested that these effects could be measured by putting gyroscopes into space.

If the universe operated according to Newton's rules, a perfect gyroscope, set spinning and pointed at a distant star, would keep pointing in the same direction forever.

But if Einstein were right -- if space and time are warped and dragged around by the rotating Earth -- then the spinning gyroscope would drift imperceptibly so that it no longer pointed right at the star. Over the course of a year, it would change direction by the equivalent of the width of a human hair as seen from 10 miles away.

For four decades, Stanford scientists and engineers tried to figure out how to make this experiment work.

``They sort of started ahead of the technology, and in fact they had to invent a lot of the technology from scratch,'' said Clifford Will, a physicist at Washington University in St. Louis who served on the National Academy of Sciences review committee.

The gyroscopes -- with the perfect, spinning spheres at their hearts -- had to float inside a vacuum chamber, chilled to near absolute zero and shielded from any outside influence, including the jittering of the spacecraft.

And all of it had to work in the harsh environment of space, where temperatures fluctuate hundreds of degrees.

Hundreds of students have worked on the project over the years -- about two-thirds of them engineers, the rest physicists. Ninety-one people have earned doctorates helping to solve the many engineering problems and elucidate the science.

As the schedule for the mission slipped and the costs escalated, the mission was canceled seven times. Each time, Stanford physics Professor Francis Everitt persuaded NASA and Congress to give it another chance.

``This thing has had the longest history of any NASA program,'' said Michael Salamon, the program manager for the mission at NASA headquarters. ``It's been threatened with extinction a number of times, but like a phoenix, it's come back and survived. It's really an amazing tale of tenacity and endurance.''

He gives much of the credit for keeping Gravity Probe B alive to Everitt, ``a remarkable man,'' who became a master at lobbying Washington on its behalf.

This rankled some scientists, who complained that Gravity Probe B was siphoning money from more worthy projects.

And unlike other high-priced NASA missions designed to explore the cosmos, this one would perform only a single experiment.

Worse, as the project dragged on, other experiments nibbled away at the problems of frame dragging and the warping of space-time. While none measures these phenomena directly, as Gravity Probe B would, the combined results make it more and more likely that the mission will simply confirm what scientists already suspect -- that the theories of general relativity are correct.

``It's a wonderful experiment,'' said Jonathan Arons, a physicist at UC-Berkeley. But if it turns out as most people think it will, he said, ``those of us who are more interested in discovering new things, and being surprised, will be disappointed.''

Supporters of the mission counter that Gravity Probe B would be the first to directly measure some of the fundamental properties of the cosmos, and with astounding accuracy. If it works, they say, it will have a place in high school textbooks as one of the classic experiments of physics.

For his part, Everitt said, ``I'm not going to make any prediction about which way it will come out. I'm an experimentalist; I want to find out what the experimental truth is. If you prejudice your mind, you may get the result you want to hear.''

Now that the known technical problems have been worked out and the mission is on the verge of flying, much of the carping among scientists has died down, observers say.

Gravity Probe B is scheduled for launch aboard a Delta II rocket from Vandenberg Air Force Base in Southern California on Oct. 30 at 8:14 p.m., plus or minus one second. If it misses that narrow launch window, NASA will wait 12 hours and try again. The mission must be launched at precisely the right time to put it into orbit over Earth's poles.

As the time approaches, Everitt -- who has devoted virtually his entire career to Gravity Probe B -- says he is not nervous. Not yet.

``It sounds strange, but I don't very much think about it,'' he said last week. ``I think about what are we going to do in the next day, and the day after that, and on down the track. There's too much to think about to worry about the future.''

Contact Glennda Chui at gchui@sjmercury.com or (408) 920-5453