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172 ✸ Galileo and the Leaning Tower of Pisa 10 A Myth about the Speed of Light instein kept some secrets,and he often shunned attention as if the details of his life were quite inconsequential. He wrote:“the essential in the being of a man of my type lies precisely in what he thinks and how he thinks, not in what he does or suffers.”1 Although he was a relatively self-isolating person, people flocked to him, reporters and photographers chased him around for decades, converting him into an icon. We see him in posters, magazines, toys, postage stamps, cereal boxes.As he complained in 1949:“my accomplishments have been overvalued beyond all bounds for incomprehensible reasons. Humanity needs a few romantic idols as spots of light in the drab field of earthly existence. I have been turned into such a spot of light. The particular choice of person is inexplicable and unimportant.”2 Still, there were some fair reasons why he first won attention, one of which is that he managed to convince many people of some seemingly unbelievable ideas. Suppose that you sit on a spaceship traveling in a straight line, say, at 160,000 miles per second. According to Einstein’s physics, the length of planet Earth as judged by you will be about half of its original length. And, allegedly, this is not an optical illusion. Does the entire planet really contract when you move? Suppose also that as you’re zipping away from Earth at 160,000 miles per second (mps), you aim a flashlight in the forward direction and turn it on. Light shoots out at about 186,282 mps away from you. How fast does that same light ray move away from Earth? We might expect that since it moves at 186,282 mps away from the ship and the ship moves at 160,000 mps away from Earth, the light moves at about 346,282 miles per second away from Earth. But according to Einstein’s physics, that ray E 172 of light moves at 186,282 mps away from Earth. We might think that the light ray must move away relative to Earth at a greater speed, and we’d expect that just flying away on a rocket cannot possibly cause the contraction of the entire planet. Otherwise, the world is bizarre. Common sense seems to fly out the window as physics becomes unbelievable and esoteric. Such notions crystallized in Einstein’s theory of relativity and they became accepted by many physicists. His theory was all based on the idea of the relativity of time, the relativity of simultaneity. Yet for centuries , philosophers had theorized various ideas about time, without generating any intense public interest. For example, according to one source, the prominent religious leader and philosopher “Pythagoras believed that time is the encompassing sphere.”3 In the late 1700s, Immanuel Kant denied that time had any absolute or objective reality.4 In 1902 the prominent mathematician Henri Poincaré echoed a growing conviction that “There is no absolute time.”5 While such various arguments did not generate widespread attention, somehow, the imaginative conjectures of a lowly patent clerk in 1905 eventually generated immense public acclaim. Einstein reached his theory by a long and complicated trajectory, but instead of tracing a broad overview, let’s take a close view of just one of its seminal aspects: the relations between speed, time, and length. I’ll discuss the kind of explanation that we don’t find in a physics class.Then in the next two chapters, I will discuss some controversial and historical speculations—myths— about the origins of Einstein’s theory. How did Einstein come to think about relativity? For ten years, from 1895 until 1905, Einstein was trying to understand the motion of light.6 Physicists conceived of light as an electromagnetic wave in an invisible medium, like air, but much more subtle and intangible, which they called“the ether.”When Einstein was just sixteen years old, he was puzzled because he wondered what a light wave would look like if one could catch up to it.7 It’s analogous to waves in the ocean; you constantly see them moving. Why don’t we ever see a stationary mountain of water on the ocean? One would be perplexed to see such a thing, a standing bump of water.Yet if you fly alongside a wave at A Myth about the Speed of Light ✸ 173 its same speed, and look...


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