Imagine that you once again have an observer standing on a railway embankment as a train goes roaring by. Because the lightning strikes are the same distance from the observer, their light reaches his eye at the same instant.
So he correctly says that they happened simultaneously. Meanwhile, another observer on the train is sitting at its exact midpoint. From her perspective, the light from the two strikes also has to travel equal distances, and she will likewise measure the speed of light to be the same in either direction. But because the train is moving, the light coming from the lightning in the rear has to travel farther to catch up, so it reaches her a few instants later than the light coming from the front.
Since the light pulses arrived at different times, she can only conclude the strikes were not simultaneous—that the one in front actually happened first. Once you accept that, all the strange effects we now associate with relativity are a matter of simple algebra.
Einstein dashed off his ideas in a fever pitch and sent his paper in for publication just a few weeks later. Einstein kept obsessing on relativity all through the summer of , and in September he sent in a second paper as a kind of afterthought. It was based on yet another thought experiment. And now imagine that it spontaneously emits two identical pulses of light in opposite directions. Now, said Einstein, what would this process look like to a moving observer?
From her perspective, the object would just keep moving in a straight line while the two pulses flew off. With a little more algebra, Einstein showed that for all this to be consistent, the object not only had to lose energy when the light pulses departed, it had to lose a bit of mass, as well. Or, to put it another way, mass and energy are interchangeable.
Einstein wrote down an equation that relates the two. All rights reserved. Share Tweet Email. Why it's so hard to treat pain in infants. This wild African cat has adapted to life in a big city. Animals Wild Cities This wild African cat has adapted to life in a big city Caracals have learned to hunt around the urban edges of Cape Town, though the predator faces many threats, such as getting hit by cars.
India bets its energy future on solar—in ways both small and big. And Einstein was the ultimate symbol of that. The physicist and science historian Abraham Pais has described Einstein similarly. Here was a jovial, mild-mannered man with deep-set eyes, who spoke just a little English. He did not yet have the wild hair of his later years, though that would come soon enough. With his violin case and sandals—he famously shunned socks—Einstein was just eccentric enough to delight American journalists.
Newspapers were flourishing in the early 20th century, and the advent of black-and-white newsreels had just begun to make it possible to be an international celebrity. As Thomas Levenson notes in his book Einstein in Berlin , Einstein knew how to play to the cameras. He was the first scientist and in many ways the last as well to achieve truly iconic status, at least in part because for the first time the means existed to create such idols. Not everyone loved Einstein, of course.
Various groups had their own distinctive reasons for objecting to Einstein and his work, John Stachel, the founding editor of the Einstein Papers Project and a professor at Boston University, told me in a interview. Some American philosophers rejected relativity for being too abstract and metaphysical, while some Russian thinkers felt it was too idealistic.
Some simply hated Einstein because he was a Jew. He was hated as a Jew, as a pacifist, as a socialist [and] as a relativist, at least. Fortunately he was on a working holiday in the United States when Hitler came to power. He would never return to the country where he had done his greatest work. For the rest of his life, Einstein remained mystified by the relentless attention paid to him. What could have produced this great and persistent psychological effect?
I never yet heard a truly convincing answer to this question. Today, a full century after his ascent to superstardom, the Einstein phenomenon continues to resist a complete explanation. According to the theory, the structure of this mesh would be revealed in the bending of light around distant stars.
To everyone at the time, this seemed implausible, for physicists had long known that light travels in straight lines. Yet in observations of a solar eclipse revealed that on a cosmic scale light does bend, and overnight Einstein became a superstar.
Einstein is said to have reacted nonchalantly to the news that his theory had been verified. The theory is correct. What made him so secure in this judgement was the extreme elegance of his equations: how could something so beautiful not be right? A quest for beauty has been a part of the tradition of physics throughout its history.
And in this sense, general relativity is the culmination of a specific set of aesthetic concerns. Symmetry, harmony, a sense of unity and wholeness, these are some of the ideals general relativity formalises. Where quantum theory is a jumpy jazzy mash-up, general relativity is a stately waltz. As we celebrate its centenary, we can applaud the theory not only as a visionary piece of science but also as an artistic triumph.
Lots of answers have been proposed to this question and many more will be given. A provocative response comes from the poet-painter Merrily Harpur , who has noted that "the duty of artists everywhere is to enchant the conceptual landscape". Rather than identifying art with any material methods or practices, Harpur allies it with a sociological outcome.
0コメント