What is the purpose of underground nuclear testing? Do governments actually learn something from these explosions? Or is it just a deranged form of political muscle-flexing? –Dave Hines, Chicago

What, you think nuclear weaponry is a mature (I use the word loosely) technology? Well, it isn’t, and considering the untold billions we’re spending on nuclear weapons research, it better not be. The purpose of underground nuclear testing is to: (1) help build better bombs, (2) test the old models to see if they still work, and (3) see what happens to something if you drop an atom bomb on it. The U.S. is thought to have conducted more than 900 nuclear tests since 1945, all but 10 of them at the Nevada Test Site, a vast federal reserve about 100 miles north of Las Vegas. These tests have helped make nuclear weapons the sophisticated, reliable instruments of destruction they are today.

Many people are surprised to learn that serious nuclear weapons research is still under way. What’s the point, if we’ve already got enough bombs to destroy the world several times over? This thought is so naive. Strategic planners assume that most of our nuclear weapons won’t survive a first strike and we’ll have to wreak what havoc we can with what remains. Thus the search for better bombs.

This is not necessarily a bad thing. Early nuclear weapons were big and dumb. The idea basically was to get them within fireball distance of a major city, industrial complex, or military facility, on the theory that if you obliterated every work of man for ten miles around you were bound to take out a few targets of military significance. Strategic planners finally realized this was a waste of good neutrons and ever since have been trying to build bombs and warheads that could be delivered more efficiently.

For example, one project being considered in the late 80s was the strategic earth penetration warhead, or EPW. These “are designed to penetrate some tens of feet underground before detonating,” says my bomb guide. “The principle underlying EPWs is that a warhead exploded underground couples more of its energy to the earth than does one exploded in the air or on the earth’s surface, creating more ground shock per kiloton of explosive yield.” Perfecting one of these babies will require tests, as will Star Wars fantasies such as nuclear-pumped X-ray lasers, should they ever be built.

Another reason for nuclear testing is to make sure that bombs already in service will work. In 1981 the government became concerned that model W80 warheads, which had been deployed the previous year, would fail at low temperatures. You can imagine the reaction if we nuked our enemies one frosty morning only to have the stupid things drop like rocks into somebody’s kitchen without going off. As a consequence of testing, the problem was headed off at the pass.

In another case in the early 60s, scientists switched the chemical explosive on the W52 warhead because it was prone to premature detonation. (Chemical explosions are used in atom bombs to trigger the nuclear ones.) But an underground test revealed that the new chemical explosive resulted in a distressingly low-wattage atomic blast. Designers came up with a fix, did another test, and were pleased to find that the desired lethality could now be achieved.

So there you go. A nasty business, I agree. But the bomb jockeys say, and it’s hard to argue with them, that if you’re going to have nukes, they might as well work.

How did “left” and “right” come to represent the ends of the political spectrum that they do? –Lisa Martinovic, Lafayette, California

The Oxford English Dictionary explains it thus: “This use originated in the French National Assembly of 1789, in which the nobles as a body took the position of honour on the President’s right, and the Third Estate sat on his left. The significance of these positions, which was at first merely ceremonial, soon became political.” If it’s good enough for the OED, it’s good enough for me.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.