Astronomy Picture of the Day

Explanation: Does gravity come in chucks? A theory known as Quantum Mechanics tells us about how the universe works on the smallest scales, while Einstein's General Theory of Relativity tells us about how gravity and the universe works on the largest scales. So far, no complete theory has been able to encompass them both. A possible step indicating that gravity really is a quantum field came recently in France with a claim that the Earth's gravitation field itself has been seen as quantized. In an experiment by Valery Nesvizhevsky and colleagues at the Laue-Langevin Institute, carefully dropped neutrons were seen to appear at only discrete heights. Scientists the world over will wait to see if such experiments are confirmed independently. Picture above is a false-color surface that might be created by the evolution of a one-dimensional string. By describing fundamental particles as tiny strings, many physicists are working toward the creation of a truly quantum theory of gravity.