In his 1976 Ph.D. thesis, Paul Worden proposed a satellite experiment that could possibly disrupt the physics world. Thirty years later, that project has grown into the Satellite Test of the Equivalence Principle (STEP) and is closer to being launched than it ever has been. On Tuesday, David King, the head of NASA’s Marshall Space Flight Center (MSFC) and John Horrack, Manager of Science and Mission Systems at Marshall, made an all-day visit to the STEP offices to see if NASA would consider giving them the funding they need to reach the stars.

Worden, now co-principal investigator for STEP, wanted to launch a satellite into space to test Einstein’s Theory of General Relativity, which had been questioned due to experimental inconsistencies. Today, STEP has designed a two-meter-long satellite that will remain in orbit for six months. STEP is now seeking the funds to build and launch the satellite.

NASA, which is funding STEP’s current research, grew more interested in giving further funding to the satellite after the launch of Gravity Probe-B (GPB), a previous collaboration between Stanford and NASA. Rodney Torii, co-principal investigator for STEP, felt that the visit went well.

“There are a number of projects at the MSFC, but David King is certainly very interested in seeing the science happen,” Torii said. “Since GPB is ending and I don’t believe that there are that many fundamental science measures planned for Marshall, he came out here to get a better idea of both Marshall’s role and Stanford’s.”

Torii was optimistic about King’s reaction.

“He was very interested and positive about the science, and it’s probably very safe to say that after coming to Stanford and seeing what it was all about, he’s still very excited about the STEP project,” Torii said.

The science involved is the Equivalence Principle (EP), one of the core facts about gravity that every schoolchild takes for granted. For Einstein, it was one of the planks of the Theory of General Relativity. Under the EP, the acceleration of a body in a given point in space due to gravity does not depend on its mass or shape. It is a lesson that Galileo learned when he dropped the two cannonballs off the Leaning Tower of Pisa.

However, Einstein’s theory of gravity breaks down at the quantum level, where it has to interact with very small particles. Torii said that the project is looking for information about the various competing theories.

“We’re basically studying gravity,” Torii said. “There is a grand idea that inertial mass and gravitational mass are the same thing even though they’re measured and thought of completely differently. If that grand idea is not true, then general relativity is not true. Now there are other theories of gravity, most of which rely on a violation of the equivalence principle.”

STEP proposes to give the principle its most rigorous test to date by placing two nested masses in a drag-free satellite in orbit around the earth. Since orbit is a state of constant free-fall around the earth, the satellite will fall for six months, allowing researchers to record even miniscule differences in acceleration.

According to Torii, ground-based experiments only measure differences up to 1 part in 10^13, since the earth’s magnetic field varies and minute seismic differences can skew the results. In space, the background noise is reduced by a factor of 1,000 and measurements are also 1,000 times more sensitive, allowing STEP to get up to 1 part in 10^18. Many alternate theories of gravitation state that the Equivalence Principle breaks down at around this level.

STEP has had to travel a long road to get this far. Initial research was funded by a seed grant from NASA, enough to support a few students, with the tiny possibility that it would someday become a satellite mission. After they started to run out of NASA funds in the 1980s, STEP looked to the European Space Agency, which was running a contest for scientific satellite missions. The mission made the final cut, but narrowly lost out to another project.

According to Worden, the team then went back to the drawing board and designed successively leaner and cheaper versions of the project.

“We came back to the states and redesigned the satellite that we had done for the European version of STEP in a simpler form with the intent of making it into a more doable experiment and saving a lot of money on it,” he said. “The version we came up with for the ESA had a lot of co-experiments on it to make it more sellable. It included several very esoteric physics experiments in addition to the basic STEP experiment, which made it very expensive.”

The team is approximately 18 months away from completing a flight prototype. Their transition afterward to the flight project, however, is stumped by a $100 million price tag, according to STEP’s Web site. Without continued funding from NASA, it will be impossible to fully proceed.