Đang tải... (xem toàn văn)
các cuộc cách mạng trong vật lý hiện đại
Book 6 in the Light and Matter series of free introductory physics textbooks www.lightandmatter.com [...]... about Einstein’s theory of relativity, but Einstein also began a second, parallel revolution in physics known as the quantum theory, which stated, among other things, that certain processes in nature are inescapably random Ironically, Einstein was an outspoken doubter of the new quantum ideas that were built on his foundations, being convinced that the Old One [God] does not play dice with the universe,”... any difference in the speed of light beams traveling east-west and northsouth The motion of the earth around the sun at 110,000 km/hour (about 0.01% of the speed of light) is to our west during the day Michelson and Morley believed in the ether hypothesis, so they expected that the speed of light would be a fixed value relative to the ether As the earth moved through the ether, they thought they would observe... her point of view, the argument goes, her homebody sister is the one who travels backward on the receding earth, and then returns as the earth approaches the spaceship again, while in the frame of reference fixed to the spaceship, the astronaut twin is not moving at all It would then seem that the twin on earth is the one whose biological clock should tick more slowly, not the one on the spaceship The. .. velocity after the collision would seem to be the result of a magical change in the mass, as if the mass of two combined, hot blobs of putty was more than the sum of their individual masses Now we know that the masses of all the atoms in the blobs must be the same as they always were The change is due to the change in γ with heating, not to a change in mass The heat energy, however, seems to be acting as if... mirrors in a spaceship If we didn’t believe in the principle of relativity, we could say that the light just goes faster according to the earthbound observer Indeed, this would be correct if the speeds were much less than the speed of light, and if the thing traveling back and forth was, say, a ping-pong ball But according to the principle of relativity, the speed of light must be the same in both... thoroughly intertwined in physics 1.1 The Principle of Relativity By the time Einstein was born, it had already been two centuries since physicists had accepted Galileo’s principle of inertia One way of stating this principle is that experiments with material objects don’t come out any different due the straight-line, constant-speed 2 3 14 Chapter 1 Relativity Fred Jerome, The Einstein File, St Martin’s Press,... speeds in the RHIC accelerator in Long Island, New York, which went on line in 2000 The gold nuclei would appear nearly spherical (or just slightly lengthened like an American football) in frames moving along with them, but in the laboratory’s frame, they both appear drastically foreshortened as they approach the point of collision The later pictures show the nuclei merging to form a hot soup, in which... observe an effect on the velocity of light along an east-west line For instance, if they released a beam of light in a westward direction during the day, they expected that it would move away from them at less than the normal speed because the earth was chasing it through the ether They were surprised when they found that the expected 0.01% change in the speed of light did not occur Although the Michelson-Morley... The paradox is resolved when we recognize that the concept of fitting the bus in the garage “all at once” contains a hidden assumption, the assumption that it makes sense to ask whether the front and back of the bus can simultaneously be in the garage Observers in different frames of reference moving at high relative speeds do not necessarily agree on whether things happen simultaneously The person in. .. education in late-nineteenth-century Germany was neither modern nor liberal He did well in the early grades,1 but in high school and college he began to get in trouble for what today’s edspeak calls “critical thinking.” Indeed, there was much that deserved criticism in the state of physics at that time There was a subtle contradiction between the theory of light as a wave and Galileo’s principle that