QUESTION: Why is Superman able to fly?

ANSWER: Comic books usually try to provide some quasi-plausible explanation for how a superhero flies. Iron Man has jets in his shoes. The Silver Surfer rides a magic surfboard. The Sub-Mariner has winglets on his ankles. Thor throws his hammer and, niftily defying Newtonian physics, gets dragged along by the wrist strap. But Superman just goes up, up and away.There is a historical answer to the question of why Superman is able to fly: Inflation of superpower. When Superman first appeared in Action Comics in 1938, he couldn't fly any more than could his Earth parents, Jonathan and Martha Kent. He was only able to "leap tall buildings in a single bound." His powers were modest: He could run about 100 miles an hour, bend steel with his hands, and withstand ordinary gunfire. And there was, by comic book standards, a reasonable "scientific" basis for those powers: He was from another planet, Krypton, where the gravity was several hundred times that of Earth. You needed superstrength (relative to Earthlings) just to stand up on Krypton.

Superman quickly became a phenomenal success, a mini-industry, and suddenly there were several Superman comics at once, plus a radio show, a series of animated cartoons and a daily newspaper strip, all produced independently and, unfortunately, incoherently. The varying writers tried to top each other with tall tales of Superman's powers. Bending steel wouldn't cut it anymore. Nor would leaping tall buildings. Doggone it, he'd have to fly. The exact moment when Superman got his wings is uncertain. According to the book "Superman at Fifty: The Persistence of a Legend," some people think Superman first flew in animated cartoons that played in movie houses. This was an extension of what happened in the comic books: "There were cases where he would leap off a tall building or swoop down, and at that point he would look like he was flying, I suppose," says Superman's co-creator, Joe Shuster.

The superpower inflation culminated in the late 1950s when Superman blew out a star with his Superbreath.

QUESTION: Why does the New York Times hype most, but not all, of its stories as "Special to The New York Times."

ANSWER: At other papers, saying "Special to . . ." means that the article was written by a free-lance writer and sold to the newspaper. The Times, however, puts it on a staff-written story that has a dateline - that is, any story written outside New York City (i.e., "ULAN BATOR, Dec. 31, 19--"). The Times, you see, is proud that it has a trench-coated correspondent rotting away in every conceivable backwater (Rangoon, Bombay, Little Rock). The only stories without a dateline (and thus, without the Special line) are those written in and about New York City itself, and stories so cosmic they could have been written in the Asteroid Belt.

QUESTION: Why can't you put a Xerox of a dollar bill into a coin changer or vending machine?

ANSWER: You can. It just won't work.

The bill "validators" inside the machines have 13 ways of recognizing a genuine U.S. buck, says Jim Douglass, vice president of marketing for the St. Louis-based Coinco, Inc. The cross-hatching around Washington's head is particularly hard to replicate on a photocopier, because the lines are so small. But let's say you did make an elaborate duplicate. You might even dye it green. It still wouldn't work: The primary characteristic the validator is searching for is magnetism. On a genuine dollar bill, some of the ink is magnetic. Some ain't. For example, the funky pyramid on the back is so magnetic you can lift paper clips with it. While you excitedly attempt this simple experiment at home let us quickly add that we are just having a little fun at your expense: we have no idea which parts are magnetic because no one would tell us.

Incidentally, we've also discovered why so often you put a perfectly good quarter in a soda machine and it falls uselessly into the coin return. The industry standard is that a machine should accept 95 percent of good coins on the first try and the other 5 percent on the second try. John Cunningham, vice president of sales for Mars Electronics, said there is great variation in the diameter, thickness and metal content of supposedly identical coins. In an electronic coin mechanism, the coin rolls through a narrow gap through which a current passes, and as it does the frequency of the current changes. A quarter will alter the frequency much differently from the way a nickel will.

But this "inductive sensing" gets confused when a coin is structurally aberrant, or even if it happens to roll through the mechanism quirkily. The same goes for mechanical - non-electronic - coin units. Unless the coin rolls down the rail just so, it'll get bounced down into the coin return. Another problem is dirt. Coins are filthy. The grime can throw off the calibration of both mechanical and electronic coin systems.