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Foiling flats, Arabic numbers are Indian

Q: How do the new tire-pressure sensors work? They’re supposed to display tire pressure inside the car. How do they manage that? (George, Sarnia, Ontario, Canada)

A: One of these clever devices is mounted on the wheel well or tire stem of each wheel. It senses pressure and temperature and then broadcasts results to a central receiver located near the front of the car. The receiver computer analyzes the information from each tire and displays it to the driver — either as pressure and temperature values or as an "overpressure" or "underpressure" condition.

How tire pressure monitors work: The red boxes depict the pressure sensor at each tire and its radio transmitter. The transmitters send pressure data to the central receiver (blue box) near the car front for display to the driver. [Drawing from Motorola’s tire pressure monitoring system description.]

Typically, a tire-pressure system contains a pressure sensor, a tiny radio transmitter, an antenna, a long-life battery, a microcontroller (the intelligence), a wakeup switch (to conserve power), and a temperature sensor.

According to Mechanical Engineering magazine, the monitors (not including the receiver and instrument panel display) cost about $12 to $15 now and may drop to about $5 a wheel as manufacturers produce millions of them to keep up with a safety-requirement demand.

In the fall of 2000, Congress passed the Transportation Recall Enhancement, Accountability, and Documentation Act — a weird title that goes by its presumably deliberate acronym: TREAD. At some, as yet unspecified date, the law says all new vehicles under 10,000 pounds must have such tire monitoring systems. This will affect some 17 million new cars and trucks each year. These vehicles will need 70 million sensors — one for each wheel and perhaps the spare.

Congress passed the law because several Ford Explorers rolled over due to under-inflated tires.

Further Surfing:

Mechanical Engineering Magazine: Pumped up, by John DeGaspari

Motorola: Tire pressure monitoring sensors

Freescale: Tire pressure monitoring system overview

Q: Why are our numbers called Arabic? Where did they really come from? (Mary, Downey, California and Kevin, Compton, California)

A: Your implied suspicions are well founded. Hindu mathematicians in India invented the so-called Arabic numbers at least 1,700 years ago. The Arabs played an essential part in passing the number system to us. Their own number system also stems from the Hindu figures.

By about 1500 years ago, the Arabs had a translation into Arabic of a Hindu text describing the nine-number system.

Our "Arabic" numbers and the original Hindu symbols. I’ve also included the Arab symbol for "2" for comparison. [Adapted from Wikipedia]

Arab mathematician Mohammed ibn-Musa al-Khowarizmi helped to get the book into European hands. Around 850, while teaching mathematics in Baghdad, he wrote an arithmetic book that explains the Hindu number system. By chance, merchants carried the manuscript to Europe where scholars translated it into Latin — Algoritmi de numero Indorum, meaning, "On Hindu number calculations."

We’ve lost the original Arabic text and only have a Latin translation.

Reading the Latin version but noticing the book had been translated from Arabic, Europeans jumped to the conclusion that Arabs invented these numbers. But this, of course, wasn’t the case.

By the way, a raised index finger that seems so naturally "one" to us has meant "one" for a long time. At least five thousand years ago, ancient Egyptians painted the symbol " | "on pottery and cut it in stone. People lifted two fingers " | | " to denote "two." If you lay the two marks on their side (like sticks laid down to count) you get two horizontal marks. Then, if you write the two horizontal marks fast, you get something like "Z" or, eventually, our "2".

Further Reading:

James R. Newman, The World of Mathematics, "Numbers and Numerals" by D. Smith and J. Ginsburg, Vol.1, pp 442 - 464, New York: Simon and Schuster, 1956.

University of North Carolina at Chapel Hill: Roman and "Arabic" numbers by Russ Rowlett

University of Wolverhampton, UK: Hindu-Arabic numerals by D. Wilkinson

University of St Andrews, Scotland: The Arabic numeral system by J J O'Connor and E F Robertson

(Answered Aug. 12, 2005)