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Question: Why do we use Arabic numerals instead of Roman numerals?

Answer: Many of you probably didn't realize you use Arabic numerals. Some of you may think this explains why you have so much trouble with math - the numbers are in a different language! How can you divide 73 by 13 when the numbers aren't even English?Actually, we don't use Arabic numerals. We use Hindu numerals. Western nations call them Arabic because Europe got the numerals from the Islamic world, which got them from the Hindus. (People used to pay less attention to the subtleties of multiculturalism.)

The switch from Roman to Arabic numerals took place in the Middle Ages, propelled by a book in the 13th century by the mathematician Leonardo Fibonacci in which he discussed the merits of the Hindu-Arabic numeral system. Islamic mathematics was not a far-off, exotic concept at that point, because for much of the Middle Ages the Muslims had ruled Spain, Sicily and North Africa, and when they were finally driven out by Europeans they left behind mathematical treatises. We tend to forget that Islam was a more powerful culture, and more scientifically advanced, than European civilization in the centuries after the fall of the Western Roman Empire.

"If you had landed from Mars in the year 800 A.D. and wanted to go to the center of mathematical learning on Earth, you'd go to Baghdad," says Bill Dunham, author of a new book, "The Mathematical Universe."

Many accountants in the Middle Ages retained Roman numerals instead of switching. The reason is that addition and subtraction can often be quite easy in the Roman system. Let's say you want to subtract 16 from 68. In the Arabic system, you plop the 68 on top of the 16, subtract 6 from 8, and 1 from 6, to get your answer, 52. But in the Roman system you'd just whack an X and a V and an I from LXVIII to get LII. It's subtraction by meat-cleaver.

But Arabic numerals are more graceful in other ways. Their main advantage is that they have a "place" system, in which the value of a numeral is determined by its position. This is one reason why it's so much easier to write 1994 than MCMXCIV. In the Roman system, the numerals are intransigent. An X is always 10, a C is always 100, and so on. (XC is 90, but the X still represents 10 and the C still represents 100.)

The Hindus also invented a 0, one of the great inventions of all time. No one knows who came up with this idea. Originally the 0 was probably just a placeholder, for use between, say, a 5 and a 7 in the number 507. Eventually it grew to be the number we know and love so much now, one unit less than 1, the number that most perfectly represents the social skills of the average Why staffer.

Our advice to everyone is to revert, whenever possible, to cuneiform numerals. These were invented by the Sumerians and Chaldeans about 5,000 years ago, and were devised on a base 60 system (as opposed to our base 10). They used little wedges as symbols and the direction the wedge pointed determined the number.

For extra credit you might want to try the Egyptian system in use about 4,000 years ago, in which 100 was represented by a chain, 1,000 by a lotus flower, 10,000 by a pointed finger, 100,000 by a tadpole and 1 million by a man with his arms outstretched.

Admit it: What math needs these days is fewer irrational numbers like pi or the square root of 2, and more tadpoles.

Question: Why do you always close your eyes when you sneeze?

Answer: We had always assumed that you had to close your eyes when you sneezed in order to keep your eyeballs from popping out onto your cheeks. But we are reliably told by Robert Naclerio, otolaryngologist at the University of Chicago, that there's no pressure behind the eyes when you sneeze because the bony eye sockets aren't connected to the nasal passages in any way.


Unfortunately we haven't found a good "why" explanation for the closing of eyes during a sneeze, and the "how" is pretty vague too. We know that the sneezing reflex is controlled by the trigeminal nerve. (Just as the planet is secretly governed by the Trigeminal Commission.) The movement of eyelids is controlled by a separate nerve called the facial nerve. The two nerves are close together and both lead to the base of the brain. There's some crosstalk, or "synkinesis," between the two nerves, so that when one reflex takes place the other happens too.

The whole dramatic convulsion of a sneeze strikes us as anti-Newtonian. Your head moves forward and down even as you emit this powerful blast of air. It seems like your head should go back, in keeping with the laws of rocketry. Naclerio explains that when you move your head forward and down, you alter the geometry of the pharynx and nasopharynx, and increase the amount of air passing through the nose. "It better directs the air through your nose than through your mouth," he says. That advances the purpose of a sneeze, to clear the nose of an offending agent.

So perhaps you close your eyes as a self-protection measure. Your head is hurling forward in order to better direct air through your nose. But your eyes are such sensitive organs, you don't want to hurt them in the middle of a sneeze. Maybe humans have developed this evolutionary trait of sneezing only with their eyes closed.

Then again, maybe we're thinking too hard. The Why staff compulsively tries to find order and logic in the universe, but some things are just random, meaningless quirks of nature. Boy it hurts to admit that.