Movin' and Shakin'
Everything is moving.
You may be sitting quietly in your armchair, but you are far from motionless. I don't mean merely that your heart is beating, your blood is coursing through your veins and you are panting at the prospect of learning so many fascinating things from this book. In short, I don't mean simply that you are physically and mentally alive.
I mean that while you are sitting there so peacefully, Earth beneath your feet is spinning you around at about 1,000 miles per hour (1,600 kilometers per hour). (The exact speed depends on where you live; see p. 119). Mother Earth is simultaneously hauling you around the sun at 66,600 miles per hour (107,000 kilometers per hour). Not to mention the fact that the solar system and all the stars and galaxies in the universe are racing madly away from one another in all directions at incredible speeds.
Okay, you knew all that. Except maybe for the exact speeds. But we're still not done.
You are made of molecules. (Yes, even you.) And all your molecules are vibrating and jiggling around to beat the band, assuming that your body temperature is somewhere above absolute zero (see p. 82). In motion also are many of the atoms of which your molecules are made, and the electrons of which the atoms are made, and the electrons, atoms and molecules of everything else in the universe. They were all set into motion about 12 billion years ago (see p. 175) and have been quivering ever since.
So what is motion? In this chapter we'll see how everything from horses to speeding automobiles, sound waves, bullets, airplanes and orbiting satellites move from one place to another.
Horsing Around on the Highway
Why do they drive on the left in some countries and on the right in others?
It goes back to the fact that most humans are right-handed.
Long before we had modern weapons such as guns and automobiles, people had to do battle using swords and horses. Now if you are right-handed, you wear your sword on the left, so that you can draw it out rapidly with your right hand. But with that long, dangling scabbard encumbering your left side, the only way you can mount a horse is by throwing your free right leg over him. And unless you are in a Mel Brooks movie and want to wind up sitting backward on your steed, that means that the horse's head has to be pointing to your left. To this day we still train horses to be saddled and mounted from their left sides.
Now that you are mounted, you will want to stay on the left side as you start down the road, because anyone coming toward you will be on your right, and if that someone turns out to be an enemy, you can whip out your sword with your right hand and be in position to run the scoundrel through. Thus, prudent horsemen have always ridden on the left side of the road.
This left-side convention was also honored by horse-drawn carriages in order to avoid annoying collisions with horsemen. When horseless carriages made their appearance, some countries continued the habit, especially during the overlap period when both kinds of carriages were competing for road space.
So why do people drive on the right in the U.S. and many other countries?
When swords went the way of bows and arrows, the need for defending one's right flank disappeared and traffic rules were suddenly up for grabs. Younger or less tradition-bound countries migrated to the right, apparently because the right-handed majority feels more comfortable hugging the right side of the road. It quickly occurred to left-handed people that it was unhealthy to argue with them.
Some countries that I've been in must have large populations of ambidextrous people, because they seem to prefer the middle of the road.
Why do highway and freeway intersections have to be so complicated, with all those loops and ramps?
They enhance the traffic flowfrom construction companies to politicians' campaign chests.
They allow us to make left turns without getting killed by oncoming traffic. It's a matter of simple geometry.
When freeways and superhighways began to be built, engineers had to figure out how to allow traffic to make turns from one highway to an intersecting one without stopping for red lights. Because we drive on the right-hand side of the road in the U.S., right turns are no problem; you just veer off onto an exit ramp. But a left turn involves crossing over the lanes of opposing traffic, and that can cause conflicts that are better imagined than expressed.
Enter the cloverleaf. It allows you to turn 90 degrees to the left by turning 270 degrees to the right.
Think about it. A full circle is 360 degrees; a 360-degree turn would take you right back to your original direction. If two highways intersect at right angles, a left turn means turning 90 degrees to the left. But you'd get the same result by making three right turns of 90 degrees each. It's the same as when you want to turn left in the city and encounter a "No Left Turn" sign. What do you do? You make three right turns around the next block. That's what the loop of a cloverleaf does; it takes you 270 degrees around three-quarters of a circle, guiding you either over or under the opposing lanes of traffic as necessary.
The highway interchange is a four-leaf clover, rather than a two- or three-, because there are four different directions of trafficgoing, for example, north, east, south and westand each of them needs a way to make a left turn.
For readers in Britain, Japan and other countries where they drive on the left, just interchange the words "left" and "right" in the preceding paragraphs, and everything will come out all right. That is, all left. You know what I mean.