所以ballistic的原意其实是球的行进路线吗？！好吧……
哦哦哦哦哦！又学到新东西了。
The world’s first ballistic missile was the V-2 rocket, designed by a team of German scientists under the leadership of Wernher von Braun and used by the Nazis during World War II, primarily against England. As the first object to be launched above Earth’s atmosphere, the bullet-shaped, large-finned V-2 (the “V” stands for Vergeltungswaffen, or “vengeance weapon”) inspired an entire generation of spaceship illustrations. After surrendering to the Allied forces, von Braun was brought to the United States, where in 1958 he directed the launch of Explorer 1, the first U.S. satellite. Shortly thereafter, he was transferred to the newly created National Aeronautics and Space Administration. There he developed the Saturn V, the most powerful rocket ever created, making it possible to fulfill the American dream of landing on the Moon.
Errr, OK??? 所以说美国人登月计划的总设计师，为纳粹工作过？哇哦，我有点佩服美国人。这才是任人唯贤吧？
THE MOST EXTREME example of an elongated orbit is the famous case of the hole dug all the way to China. Contrary to the expectations of our geographically challenged fellow citizens, China is not opposite the United States on the globe. A straight path that connects two opposite points on Earth must pass through Earth’s center. What’s opposite the United States? The Indian Ocean. To avoid emerging under two miles of water, we need to learn some geography and dig from Shelby, Montana, through Earth’s center, to the isolated Kerguelen Islands.
Now comes the fun part. Jump in. You now accelerate continuously in a weightless, free-fall state until you reach Earth’s center—where you vaporize in the fierce heat of the iron core. But let’s ignore that complication. You zoom past the center, where the force of gravity is zero, and steadily decelerate until you just reach the other side, at which time you have slowed to zero. But unless a Kerguelian grabs you, you will fall back down the hole and repeat the journey indefinitely. Besides making bungee jumpers jealous, you have executed a genuine orbit, taking about an hour and a half—just like that of the space shuttle.
Yes. This totally makes sense. And indeed very interesting.
Fearing the entire solar system was unstable and would eventually crash its planets into the Sun or fling them into interstellar space, he postulated, as we will see in Section 9, that God might step in every now and then to set things right.
So THAT is all the "Newton went religious" all about.
呃，后面的也想截下来的，但是太长了。就是说银河系的中心是个黑洞，无限接近黑洞却没有被吞噬的恒星会极大加快速度。然后离银河系最近的星系会和银河系相撞。嗯。
