Einstein's theory is getting a new test, while Darwin's theory of evolution has gotten new proof.

The Gravity Probe B, due to launch April 17, will test Einstein's theories on the nature of space and time by measuring slight changes in gravity from 640 km (400 miles) up. (Picture of the probe is from a BBC story on the mission.)

Once the four quartz balls inside the satellite start to spinning, there should (if Einstein was right) be slight changes in their orientation or "spin axis." This twisting effect, called frame dragging, has yet to be measured, but if it exists this experiment should (assuming the quartz spheres are as perfect as claimed) find it.

And what of Darwin?

Darwin's theory of evoluation also relates to time, but more directly. Given enough time, and environmental stress, anything can evolve from anything. We might be descended from, say, fish.

And that's exactly right, according to Neil Shubin of the University of Chicago. His story is told in a recent Scientific-American. (The picture is taken from that story.)

What Shubin found, by a Pennsylvania highway, was a 365 million year old humerus, or arm bone, that was attached to a fish-like creature in the late Devonian period. The bone, and its attached muscle, would have allowed the creature, which looked distinctly fishy, to prop itself up. It could skitter across a nearly-dry riverbed, even get its head up above the water.

Looking at the age and complexity of this fish's arm, the idea that men and apes had a common ancestor does not sound nearly so loony. It sounds, in fact, quite modest.