You hear people say all the time, "If they could put a man on the moon, how come they can't cure cancer?" Or make decaffeinated coffee taste good? And so forth.

In the days after a deadly coal-mine collapse in Utah last month, the Washington Post newspaper published a long article about mining disasters, by Jeff Goodell, who has written a book about mine safety. In the newspaper, he asked a man-and-moon-type question: "Why, at the beginning of the 21st century, when we can download real-time images from Mars onto our laptop computers, has no one figured out a way to track or communicate with coal miners underground?"

It's a question that Congress itself asked last year while enacting the most comprehensive mine-safety act in generations. The measure directed the secretary of Labor to require wireless two-way communications and an electronic tracking system in underground mines within three years. They would permit rescuers on the surface to locate persons who are trapped.

Fine, but you cannot require something that hasn't been figured out yet. Despite lots of money and brainpower, nobody has yet solved this simple problem. Sound waves zip merrily through the air, as do radio waves through the non-air of outer space.  But they just can't penetrate solid rock very far, as you may have discovered if you've tried using a cellphone in a long tunnel. No matter how much you amplify the signal, it gets weaker and weaker the more rock or coal gets in its way.

You could string telephone cable. But that's impractical and prohibitively expensive. And it goes without saying that a frail wire doesn't survive underground moisture, drilling, blasts or cave-ins very well.

So while men and women now routinely chat with us from space, and many kinds of cancer are almost certainly curable if caught early, the mining industry has so far dug deep without success, seeking a simple way to keep in touch from not very far away.