National Geographic : 1957 Dec
fTwilight zone 2 (One week later) 3 (Two weeks later) 4 (Three weeks later) Tilting Orbit Reveals the Satellite to Moonwatchers in Many Latitudes Because of gravity's more powerful effect at the earth's bulging Equator, the satellite's orbit precesses, or pivots, like a child's top slowing down. These sketches show the effect of precession on the baby moon's visibility. Figure 1 pictures the satellite (white dot) as it orbits at a 450 angle to the Equator. On this course it enters the twilight zone-the only point at which it can be seen-over the southeastern Pacific. Figures 2, 3, and 4 show the same satellite's orbit at weekly intervals. In each case the tilt, proceeding in opposite direction to the earth's rotation, has caused the satellite to cross the twilight zone farther north. The process is reversed on the opposite side of the globe. + These diagrams show visibility of satellites launched on four different courses. Orbit 1 gives a view of the speeding sphere only to residents of the Tropics. Orbits 2 and 3 add spectators in the Temperate Zones. Orbit 4, from pole to pole, reveals the moon to the entire rotating world. It is said that if a fully instrumented satel lite can stay up a year, it should gather enough data to keep scientists busy for years just to fit in the new facts with what we know. The more interest mounts among both be ginning and mature scientists everywhere, the better the chances will be for a veritable quan tum jump in scientific endeavor-what is sometimes unfortunately called a break through. I don't like this word, because it sounds too much like something that went ac cording to plan. I prefer to talk about a fall through. You fall through the ice of ignorance where it happens to be thinnest-and satellites will help thin a lot of that ice. To help make sure that they do, we will publish the U. S. satellite data as quickly as we can, so that they can be readily consulted by scientists anywhere in the world. We know from experience how much the prompt publication of scientific findings can do for us. We have already given out freely the upper-atmosphere information obtained by research rockets.* In consequence, theo retical physicists in countries unable to launch rockets themselves have worked on this mate- 807 rial and in their turn published results that we ourselves were in no position to work out at that time. To sum up, then, let me say that the odd music of the satellite represents the culmina tion of a long chain of human dreams and achievements: Lucian, the Greek satirist, fan tasticated about a naval vessel carried to the moon by a whirlwind; Benjamin Franklin's kite drew electricity from a cloud; the U. S. Army Air Corps-National Geographic So ciety's research balloon Explorer II rose to 13.7 miles in 1935; and Chinese rockets of the 13th century foreshadowed today's sky piercing giants. Dawn of the Space Age Last, but surely not least, satellites lead us to intriguing thoughts about man's chang ing place in the scheme of things. Once man thought his earth the center of the universe. Then science taught him that he was merely hurtling through space on one * See "Rockets Explore the Air Above Us," by New man Bumstead, NATIONAL GEOGRAPHIC MAGAZINE, April, 1957.