Here are the first and second sentences from Jeans' essay.

Because of the way it came into existence, the solar system has only one-way traffic, like Piccadilly Circus. The traffic nearest the center moves fastest; that further out more slowly, while that at the extreme edge merely crawls, at least by comparison with the fast traffic near the center.

Notice how the second sentence picks up and expands on the image of the traffic. It uses Piccadilly Circus as an analogy and explains the analogy. Piccadilly Circus in London is a "roundabout," a large circle of traffic, all moving in one direction, with roads leading away in various directions. A driver moves around the circle until coming to his or her exit. Jeans compares the movement of the planets in our solar system to the movement of traffic on a roundabout.

Now, read the first two sentences again and try to predict what Jeans will write about next. What has he led you to expect? What do you need to know next? When you think you know, click on NEXT.

Because of the way it came into existence, the solar system has only one-way traffic, like Piccadilly Circus. The traffic nearest the center moves fastest; that further out more slowly, while that at the extreme edge merely crawls, at least by comparison with the fast traffic near the center. NEXT