A story, oft repeated among engineers, claims that the Tennessee
state legislature once voted to make pi equal to 3. I hope this
story is an urban legend.
A story, oft repeated among engineers, claims that the Tennessee state legislature once voted to make pi equal to 3. I hope this story is an urban legend. Every geometry student knows that pi, the ratio of a circle’s circumference to its diameter, does not equal three.
Most of us remember that pi to two decimal places is 3.14. My husband bothers to remember that pi to four decimal places is 3.1416. Our daughter Anne, who has peculiar ideas of fun, has memorized pi as 3.14159265358979323846264 … but even that is only 23 decimal places.
One-half, expressed as a decimal, is .5. It stops. One-third, expressed as a decimal, is .333 repeating 3 … the 3s repeat forever. One-half and one-third are rational numbers. Pi is an irrational number; the digits go on forever without ever stopping or repeating themselves. It boggles the mind. No surprise if the Tennessee legislature decided to call it 3.
Except that it doesn’t work. If pi were 3, a circle with a diameter of 7 would have a circumference of 21. Actually, that circle’s circumference is almost 22. Pi isn’t 3, however convenient it would be if it were. If engineers and physicists pretended that pi was 3, to suit the fiats of legislators, bridges and airplanes would fall.
So engineers go on using pi equals 3.14159265358979323846264 …, or designing calculators to remember it for them, and the bridges stand. That’s science; a little inconvenient sometimes, but real, even if it doesn’t seem rational to laymen.
I remembered the story of legislating pi to be 3 when I read The Dispatch’s editorial of July 29th. Apparently the EPA has announced that it will not be ready to set a federal standard for safe levels of perchlorate until 2010.
Ephraim King, the EPA’s director of water standards, is quoted as saying: “We are doing studies on perchlorate, we care tremendously, and we’re moving as fast as we can. We can’t start the formal rule-making process until all the data is on the table.”
That’s not good enough for the editorial board of The Dispatch. The editorial board wants a standard set now, and they advise their readers to lobby our senators to legislate a standard.
Never mind that there hasn’t been enough time to do longitudinal studies, following individuals to see what troubles emerge following long-time perchlorate ingestion. Never mind that the epidemiologists are already hard at work, finding populations that have ingested perchlorate contaminated water, and comparing their medical histories with control populations. Never mind that the only person who has begun testing vegetables for perchlorate pick-up is a San Martin amateur, Bob Cerruti (and kudos to him for investigating.) The Dispatch wants a standard set, and they “can’t wait till 2010 to find out.”
Pi equals three, anyone?
At least this editorial is on the Opinion Page, where it belongs. For months, The Dispatch has been editorializing in its news articles, with constant references to perchlorate poisoning. Granted, it’s an attractive, snappy alliteration, but the word poison strongly suggests malicious intent. The Dispatch’s vital function of reporting truth, of holding Olin’s toes to the fire of public opinion, is too essential to be squandered on this sort of yellow journalism. But I digress.
What if we set a standard now, before all the data are in?
We could set it high, at 400 ppb. Olin would stop cleaning up. More people would drink contaminated water. In a few decades, thyroid problems might show up in San Martin residents.
We could set it low, at 1 ppb. No water in the state would meet this standard, because our current technology only measures down to 4 ppb. So we could all drink distilled water… but that practice carries its own set of health risks.
We could choose a number in between, 100 or 50 or 20 or 5. We don’t have sufficient data to pick a number scientifically, so we might as well throw darts to pick it. Who among us, right now, is ready to tell a pregnant woman that drinking 5 ppb of perchlorate will not harm her baby?
I’m not. Neither is the EPA. As soon as the data are in, we’ll set a standard. In the meantime, drink bottled water. Even if it takes till 2010.
