Myths
Full explanations for these myths are complex and in a few cases still open for debate. Here are some simplified answers.
1. Some of the perceived color of lakes and oceans is due to reflected light from the sky, and the amount of this reflection depends on the angle of the observer to the water. But lakes and oceans sometimes remain blue even when the sky is gray. The more precise explanation is that water itself is slightly blue. The more water you look through, the deeper the blue.
2. There are only 91 elements now known to occur naturally on Earth. Two elements between 1 (hydrogen) and 92 (uranium) do not occur naturally: technetium (element 43) and promethium (element 61). Trace amounts of naturally occurring plutonium (94) were discovered in the 1970s. So there are 91 elements known to occur naturally on Earth. But leave Earth and all bets are off: Technetium has been detected by spectral analysis in some stars.
3. If Franklin flew a kite in a thunderstorm and drew a spark from a metal key hanging from the string, the source of the electric charge was not a lightning bolt but the electric charge in the air. If Franklin’s kite had been struck by lightning, he probably would have been killed.
4. Electric current is the flow of electric charge, and both protons and electrons possess charge. Although individual electrons constantly wiggle at high speeds within metals, electrons as a group flow very slowly. In fact, in alternating current electrons vibrate in place—they do not have to move forward in order to transmit electromagnetic energy. Electromagnetic energy, like sound, is a wave phenomenon. While electromagnetic energy does flow at nearly the speed of light, this energy is not the flow of individual electrons any more than sound waves are the flow of wind.
5. Airplanes stay aloft because wings deflect air downward. If wing shape were solely responsible for lift, then airplanes could not fly upside down, and symmetrical airfoils would not work. To feel the lifting effect of deflected air, stick your hand, palm down, out the window of a moving car and tilt the front edge of your flat hand slightly up.
Miscalculations
1. The 10 percent savings does not accumulate. If it did, then in three years the family would have saved more than 100 percent. The correct statement is that the family continues to save 10 percent of the total cost as they buy more wine.
2. The percentage increase in speed does not equal the percentage of time saved. If it did, a 100 percent faster computer would reduce work time to nothing. The correct statement is that if a Power Mac runs 50 percent faster than a previous computer, it saves 33.33 percent of waiting time. Why? The faster computer runs at 150 percent of the slower computer’s speed. The ratio of the older to the newer computer’s speed is 100/150, or 2/3, so the new computer finishes in two-thirds the time, saving one-third (33.33 percent) of the waiting time.
3. A temperature of 7 degrees Celsius does equal 44.6 degrees Fahrenheit, but a rise of 7 degrees Celsius does not equal a rise of 44.6 degrees Fahrenheit. If that reasoning were valid, a rise of 32 degrees Fahrenheit would equal a change of 0 degrees Celsius. Translating from Celsius to Fahrenheit involves adding a constant (32) as well as multiplying by a constant of proportionality (1.8). When converting a change in temperature, just multiply by the constant of proportionality. Thus, a rise of 7 degrees Celsius equals a rise of 12.6 degrees Fahrenheit (1.8 x 7 = 12.6).
Eyesores
1. In any sequence of gears, successive gears turn alternately one way, then the other. If the number of gears in a loop is odd, then the gears fight each other and won’t turn at all.
2. Of course, this diagram is stylized, with raindrops much bigger than actual size relative to the cloud. The scientific error is the teardrop shape, which is correct for tears sliding off a cheek but not for falling raindrops. Actual raindrops are basically spherical. As they gain size, they flatten out into bulbous disks, then eventually split into smaller spheres.
