One cold, winter night, a young woman was waiting in vain for the bus. She started to walk to keep from freezing. The omnibus traveled at about 40 mph. The earth traveled around the sun at about 70,000 mph. The solar system drove the celestial highways of the galaxy at close to 600,000 mph. The galaxy traveled at a speed of up to 700,000 mph. The local cluster of galaxies traveled at almost double that speed at 1,340,000 mph. One day, some 4 billion years into tomorrow, her galaxy would crash into another galaxy–it was heading into the collision at a speed of 240,000 mph. She could only walk about 4 mph, but the possibility of a stray motorist driving into her at 20 to 50 times her speed was not improbable. More than 12 people a day died that way. Though the wind was sharp, the traffic lights and shop windows made her feel warm in her heart. The manholes looked like black holes. A dark sea of stars glowed in the northern sky. All the iced, black sidewalks had been covered with the pale blue sparkles of salt. The salt splashes looked like galaxies and constellations of stars, some dim and some bright, giving the illusion of varying distances. She could not escape the temptation to count and build a puzzle as she walked. There seemed to be about 5 galaxies of salt per square of pavement. The more she walked, the more she counted. There were about 40 paved squares per block. Block after block, her vague math seemed to confirm the estimate. There were about 10 blocks per mile, and thus 400 paved squares per mile. She knew from the city’s published records on engineering and maintenance that there were some 90 miles of sidewalk, which meant there were about 36,000 paved squares. To summarize, there were about 200 galaxies per block, 2000 galaxies per mile, and thus about 180,000 galaxies of salt on the sides of the city streets that night, if all had been salted just like the blocks she had walked till now. In those days, scientists thought there might be about 500,000,000,000 galaxies in the universe. Cities like hers, with a population of 150,000 or more, only numbered 5,000. There were not enough cities on earth. She would need almost 600 times more cities with frozen, salted streets to mirror the heavens above.