Broca's Brain by Carl Sagan Read Free Book Online

warned that the relativity theory “cloaked the ghastly apparition of atheism.” This alarmed a New York rabbi who cabled Einstein: “Do you believe in God?” Einstein cabled back: “I believe in Spinoza’s God, who revealed himself in the harmony of all being, not in the God who concerns himself with the fate and actions of men”—a more subtle religious view embraced by many theologians today. Einstein’s religious beliefs were very genuine. In the 1920s and 1930s he expressed grave doubts about a basic precept of quantum mechanics: that at the most fundamental level of matter, particles behave in an unpredictable way, as expressed by the Heisenberg uncertainty principle. Einstein said, “God does not play dice with the cosmos.” And on another occasion he asserted, “God is subtle, but he is not malicious.” In fact, Einstein was so fond of such aphorisms that the Danish physicist Niels Bohr turned to him on one occasion and with some exasperation said, “Stop telling God what to do.” But there were many physicists who felt that if anyone knew God’s intentions, it was Einstein.
    One of the foundations of special relativity is the precept that no material object can travel as fast as light.This light barrier has proved annoying to many people who wish there to be no constraints on what human beings might ultimately do. But the light limit permits us to understand much of the world that was previously mysterious in a simple and elegant way. However, where Einstein taketh away, he also giveth. There are several consequences of special relativity that seem counterintuitive, contrary to our everyday experience, but that emerge in a detectable fashion when we travel close to the speed of light—a regime of velocity in which common sense has had little experience ( Chapter 2 ). One of these consequences is that as we travel sufficiently close to the speed of light, time slows down—our wristwatches, our atomic clocks, our biological aging. Thus a space vehicle traveling very close to the speed of light could travel between any two places, no matter how distant, in any conveniently short period of time—as measured on board the spacecraft, but not as measured on the launch planets. We might therefore one day travel to the center of the Milky Way Galaxy and return in a time of a few decades measured on board the ship—although, as measured back on Earth, the elapsed time would be sixty thousand years, and very few of the friends who saw us off would be around to commemorate our return. A vague recognition of this time dilation was made in the motion picture
Close Encounters of the Third Kind
, although a gratuitous opinion was then injected that Einstein was probably an extraterrestrial. His insights were stunning, to be sure, but he was very human, and his life stands as an example of what, if they are sufficiently talented and courageous, human beings can accomplish.
    EINSTEIN’S LAST public act was to join with Bertrand Russell and many other scientists and scholars in an unsuccessful attempt to bring about a ban on the development of nuclear weapons. He argued that nuclear weapons had changed everything except our way of thinking. In a world divided into hostile states he viewed nuclear energy as the greatest menace to the survival of the human race. “We have the choice,”he said, “to outlaw nuclear weapons or face general annihilation.… Nationalism is an infantile disease. It is the measles of mankind … Our schoolbooks glorify war and hide its horrors. They inculcate hatred in the veins of children. I would teach peace rather than war. I would inculcate love rather than hate.”
    At age sixty-seven, nine years before his death in 1955, Einstein described his lifelong quest: “Out yonder there was this huge world, which exists independently of us human beings and which stands before us like a great, eternal riddle, at least partially accessible to our inspection and thinking. The contemplation