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CHAPTERS BY WACEK KIJEWSKI |
# CHAPTER X: EstimationWe are surrounded by numbers. We count, measure, calculate, compute, estimate... Numbers quantify information; there are essential to understand facts events, processes, laws... Once information is quantified, they can carry specific meaning. They are becoming interesting or puzzling or shocking. We should develop a habit to use numbers in our judgment or assessment to verify information quickly and efficiently. In the last chapter, we stressed how important it could be to assess result of our measurement and to present the final result with a smallest uncertainty possible. Very often, however, we do not need such a degree of accuracy or such a degree of accuracy is not possible to obtain on the basis of the data available. Still, an estimation of a quantity, often known as “order of magnitude” calculations, may be sufficient to verify the correctness of our reasoning or observation. A student, while learning to present measured or computed numerical values of quantities in SI units, often does not “feel” whether, for example, an order of magnitude of 10-2 with a unit of m3 is correct for a volume of an eraser he uses, whether an order of magnitude of 10¹ with a unit of kg is correct to express mass of air in a physics laboratory, whether in order to replace four tiles (10 cm × 20 cm) in his bathroom, he should order 0.8 m² of the tiles, whether a mass of cement ordered for a passage from a street to his house is not 10 times too high, whether it could be true that a spy in a film escapes with a 100 million dollars' worth of gold in a suitcase etc., etc. A quick rough estimation of the result could verify our calculations and provide us with useful information. Consider the numbers that we are confronted with every day: the number of people affected by the HIV virus, the population of India, the USA deficit, the billions spent on stealth bomber, the value of German exports, the size of the Milky Way, the number of stars in the largest galaxy, the number of chess plays programmed in the Deep Blue computer while playing against Kasparov, the number of genes in our body, the number on neutrinos in our universe etc. But can we imagine what such big numbers mean? Most of us cannot. Our understanding and feeling of big numbers have not developed yet. DID YOU KNOW ???? HOW HEAVY IS A SIN? If we carry our sins all the time, sooner or later, we will not be able to carry on, the burden becoming increasingly heavier. The only solution is to break with all sins: no matter how light they may be. on, the burden becoming increasingly heavier. The only solution is to break with all sins: no matter how light they may be.
Do you like anecdotes, interesting and challenging problems, fun facts, puzzles, jokes related to metric system and measurement? Read them in the 2006 on-line edition of "SI Units, Conversion and Measurement Skills",186 pp.
Wacek Kijewski About the Author Wacek Kijewski: born in Poland, studied electronics, telecommunication, acoustics and pedagogy. He taught science in Poland, Hungary and became Lecturer and Principal Tutor in Nigeria and Botswana. Dr. L.S. Molema, English Dept., UB: “Students speak warmly of him, especially his capacity for making them understand and feel confident in a subject that they had previously been inadequately prepared for and were therefore scared of. I have just finished editing the proofs of his new book: “S I Units, Conversion and Measurement Skills” in which his teaching style, so popular with his students, is evident.” |
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