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This entertaining follow-up to DK's popular Go Figure!, Why Pi? presents even more mind-bending ways to think about numbers. This time, author Johnny Ball focuses on how people have used numbers to measure things through the ages, from the ways the ancient Egyptians measured the pyramids to how modern scientists measure time and space.
Johnny Ball has hosted more than 20 UK children's television series about math and science. He is known for making math not just easy to understand, but genuinely fun and fascinating. His shows and videos earned him a New York international EMMY nomination, a BAFTA, and 10 other awards. He has written five children's books, including DK's Go Figure!, and an educational musical. His academic credentials include three honorary science doctorates and fellowship of the British Mathematical Association.
to predict the weather is to measure air pressure. We use a device called a barometer to do this. Some barometers even come with a prediction printed on the pressure dial. When weather forecasters talk about “highs” and “lows,” they mean areas of high and low pressure. High-pressure areas are usually calm and sunny, while areas of low pressure usually have bad weather. y Squid −10,000 ft (−3,000 m) Forecasting the weather dr 500 bar 300 bar Ozone Layer 50,000 ft (16,000 m) 1,000 bar r
a week, but a week was 3 days longer so that meant only one day off in 10! Internet time The Poles The world’s time zones meet at the North and South poles. By walking around the poles themselves, it’s possible to travel through all the world’s time zones in a matter of seconds. Time travel Instead of time zones, everyone in the world could use the same time but start and finish the day at different points. That’s the idea behind Internet time. A day is made of 1,000 units and time is simply
rate is £1 = $1.50, then the British pound has more spending power and might be overvalued (which means it could tumble in value in the future). Hobo power This is a measure of how bad something smells. It ranges from 0 (no smell) to 100 (lethal). A robust fart is about 13 hobo. At 50 hobo, the person doing the smelling would definitely vomit. Yuck! Calorie The calorie (also called kilocalorie) is used to measure how much heat energy food releases when it burns. The more energy the food
triangle is simply half a rectangle. 5 7 3 So you multiply the length by the width and divide by two. Then you simply add up all your triangles. 5 × 7 = 35 35 ÷ 2 = 17.5 Puzzle Using the technique above, see if you can work out the area of this four-sided shape, assuming each gray square is one square centimeter. The answer is at the back of the book. I’m a frayed knot. 21 (c) 2011 Dorling Kindersley, Inc. All Rights Reserved. The ancient world It’s all Greek Measuring angles The
trig is learning the jargon—the technical words like sine, cosine, and tangent. These words tell you the ratio of any two sides. Fortunately, there’s an easy way of remembering them all... ot se Opposite H Trigonometry has all sorts of uses in the modern world, from calculating the force a pair of pliers can exert to digging tunnels. In 1905, builders used trigonometry to build the Simplon tunnel through the Alps mountains. They dug from both ends, but they couldn’t set a course by looking