York team marks Gravity Probe B’s year in space

Norbert Bartel, professor in York’s Department of Physics & Astronomy, was recently asked to mark the one-year anniversary of the flight of Gravity Probe B (GP-B) by talking about the work he and his team have contributed to the experiment to prove Einstein’s General Theory of Relativity mounted by California’s Stanford University and NASA. Bartel’s team at York includes researchers Michael Bietenholz and Ryan Ransom, and graduate student Jerusha Lederman.

GP-B was launched on April 20, 2004 and will continue collecting data until sometime this spring when the science portion of the mission will be complete. Researchers in Canada, the US and France, are contributing data to the final calculation which will eventually be released to the public. Here is Bartel’s report:

Nobert Bartel and Francis EverittNothing has seriously gone wrong yet, and that alone is exciting. The most difficult experiment ever done in space is working to near perfection – but that is about all we can say at this time.

Right: Norbert Bartel with Stanford University’s Francis Everitt

GP-B has been orbiting Earth now for one year, measuring the warping and twisting of space-time to figure out whether Albert Einstein was right or wrong. It had been 40 years in the making at NASA and Stanford University in collaboration with Lockheed Martin till the satellite could be launched exactly a year ago. It is just mind-boggling to think of the small spheres, called gyroscopes, as they freely fall around the earth while the satellite is just literally built around them to shelter them and to provide the experimental platform for the experiment. No touching, no contact between the spheres and the satellite is allowed.

Do the gyroscopes move as predicted by Einstein?

We do not know. We actually do not have the slightest inkling of an answer. The team at Stanford keeps extremely quiet as planned but does that mean they could perhaps already know the answer? They cannot know it. The final answer depends also on our work here at York which is done in collaboration with our colleagues at Harvard University. It is a double-blind experiment. At NASA and Stanford they measure the tiny motion of the gyroscopes relative to a star, and we at York and Harvard measure the motion of the star relative to the distant universe. No group is allowed to peek over the shoulder of the other so as to avoid any human bias, intentional or unintentional.

Above: York Gravity Probe-B team members, from left, Jerusha Lederman, Ryan Ransom and Michael Bietenholz (photos courtesy of Tatiana Ouvarova)

I am already anticipating with some nervousness the dramatic moment when our two numbers will be combined to give the final result.

A hundred years ago Einstein started a revolution in physics by redefining space and time. In commemoration of Einstein’s miraculous year in 1905 UNESCO has declared this the World Year of Physics. Here we are sitting and looking at this data point and that data point trying to make absolutely sure that our analysis is correct. No error allowed. But the larger picture is really that we are testing Einstein’s Universe. Space-time is at the heart of Einstein’s theory, and what can be more fundamental than space and time?

For more information on Gravity Probe B and Testing Einstein’s Universe, the DVD produced by Bartel to explain the experiment, visit the Astronomy Films Web site.