地球的质量与运动轨迹

Albert Einstein wins again. A new study has confirmed another prediction of his theory of general relativity. The corroboration appears online in the journal Physical Review Letters. [Francis Everitt et al., citation to come.]

Einstein’s theory recognizes that massive objects warp the very fabric of space and time. If the theory is true, then the Earth should stretch the spacetime in which it sits, like a bowling ball would deform a trampoline. What’s more, the Earth’s rotation should also produce a drag on local spacetime, like a marble spinning in molasses would pull the goop around it.

To measure these minor deformations, scientists sent four gyroscopes into space in a mission called Gravity Probe B. And they found that after circling the Earth some 5000 times the gyroscopes’ angle of spin had changed, ever-so-slightly, in response to the Earth’s gravitational pull. Which proves that the old man was right.

Gravity Probe B was first conceived in 1959. [1976 paper envisioning the experimental setup] And the technology created to make the mission fly has been applied in work on the big bang theory—the real theory, not the TV show—and in GPS. Which Einstein would have loved. Because even a genius can get lost on the highway.

—Karen Hopkin