January 25, 2005

A Pocket of Near-Perfection

A story over at SpaceWeather reminded me of an article I saw at the NASA Websitelast year about a very beautiful experiment in space. The SpaceWeather (good place to check for Aurora activity) site said: bq. The solar explosion that sparked auroras over Europe also zapped NASA's Gravity Probe B satellite, temporarily causing it to lose track of its guide star, IM Pegasi. Gravity Probe B is no ordinary satellite--it's one of the most exquisite physics experiments ever attempted. Physicists are monitoring gyroscopes inside the spacecraft for wobbles that would indicate a subtle space-time vortex around Earth predicted by Einstein's theory of relativity. Good news: Solar activity has ebbed and Gravity Probe B is back to normal. I had forgotten just how beautiful this project was. From the project website at NASA bq. The idea behind the experiment is simple: Put a spinning gyroscope into orbit around the Earth, with the spin axis pointed toward some distant star as a fixed reference point. Free from external forces, the gyroscope's axis should continue pointing at the star--forever. But if the region of space through which the gyroscope orbits is slightly twisted, as Einstein's theory predicts, the direction of the gyroscope's axis would drift ever-so-slightly over time. By noting this change in direction relative to the star, the subtle frame-dragging effect can be measured. And the gyro in question? bq. The gyroscopes in GP-B are the most perfect spheres ever made by humans. These ping pong-sized balls of fused quartz and silicon are 1.5 inches across and never vary from a perfect sphere by more than 40 atomic layers. That means that if these gyroscopes were the size of the Earth, the elevation of the entire surface would vary by no more than 12 feet! Visit the NASA site for more of the well engineered tech and thought that went into this little bird. A gorgeous piece of design for an elegant experiment... Posted by DaveH at January 25, 2005 10:28 PM