“Roger Penrose discovered that if you launch the object at a clever angle and make it split into two pieces as figure 6.4 illustrates, then you can arrange for only one piece to get eaten while the other escapes the black hole with more energy than you started with. In other words, you’ve successfully converted some of the rotational energy of the black hole into useful energy that you can put to work. By repeating this process many times, you can milk the black hole of all its rotational energy so that it stops spinning and its ergosphere disappears.”