PAUL SOLMAN:

Now, if some of us don't ebb as we age, Glashow is a good bet to be one of them. At age 78, he debunked a much-publicized experiment claiming that particles could move faster than the speed of light.

For most of us, though, cognitive function shrinks with our height, our abs, our libido. In work by Harvard economist David Laibson and others, skills like word recall and counting backward from 100 by sevens declines steadily throughout life. But, as we age, we gain experience. Our so-called experiential capital rises. And the net effect is positive. People become better decision-makers as they age, up to a point.

But the negative effects start to dominate in our '50s. And by the '70s, the decline steepens for the average person.

Steve Trachtenberg is 75.