NASA's Gravity Probe B (GP-B) mission has confirmed two key predictions derived from Albert Einstein's general theory of relativity, which the spacecraft was designed to test.The experiment, launched in 2004, used four ultra-precise gyroscopes to measure the hypothesized geodetic effect, the warping of space and time around a gravitational body, and frame-dragging, the amount a spinning object pulls space and time with it as it rotates.
GP-B determined both effects with unprecedented precision by pointing at a single star, IM Pegasi, while in a polar orbit around Earth. If gravity did not affect space and time, GP-B's gyroscopes would point in the same direction forever while in orbit. But in confirmation of Einstein's theories, the gyroscopes experienced measurable, minute changes in the direction of their spin, while Earth's gravity pulled at them.
When I flew on my reduced-gravity flight (the experience of which is chronicled, my flight was a total of 32 parabolas 30 microgravity parabolas, plus one lunar and one Martian parabola where we felt what gravity feels like on those worlds. That’s the “typical” experience in the NASA Reduced Gravity Flight Program where students design, build and fly an experiment for reduced gravity.
When writing recently about students from the University of Nebraska-Lincoln, who participated in the program in 2009, I noticed right away a major difference between their experiences than mine: their experiment tested the flow rates of several different kinds of soils under lunar gravity conditions. They needed to test their experiment in lunar gravity one-sixth gravity instead of the microgravity on my flight. While my flight gave me a feel for what it’s like to be on the space shuttle or International Space Station, these students got a much longer feel for what’s like to be an astronaut on the moon.
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