Speaking of gravity, I've come across an interesting article in the Wall Street Journal that suggests gravity may not quite be the fact we think it is.
From the article:
Indeed, Dr. Turyshev at the Jet Propulsion Laboratory and his colleagues around the world regard the Pioneer probes as the largest test of Newton's law of gravity ever conducted. By that axiom, refined by Einstein, any two objects in the universe exert gravitational attraction on each other proportional to their mass and affected predictably by the distance between them.
"We would expect the two spacecraft to follow Newton's law of gravity," Dr. Turyshev said, "but they in fact fail to confirm Newton's law. If Newton is wrong, Einstein is wrong too."
For 14 years, Dr. Turyshev sought a simpler answer. He finally wondered whether heat radiating unevenly from the probe might be the cause but lacked enough information.
...Based on a partial analysis, Dr. Turyshev reported in April at a meeting of the American Physical Society in St. Louis that at least 30% of the force can be attributed to heat radiating from the probe. "The rest is unknown," he said.
Who says science is boring? ;)
HT "Grandma" O'Leary @ Colliding Universes