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Collapse of matter into a black hole


Quantum ideas. Quantum foam. Max Planck and Karl Popper
John Wheeler Scientist
Comments (1) Please sign in or register to add comments
Sunday, 29 December 2019 09:51 AM

"为量子引力做出最大贡献的科学家是约翰·惠勒(John Wheeler),一位横跨20世纪物理学的传奇人物。他是尼尔斯·玻尔在哥本哈根的学生兼合作者;是爱因斯坦移居到美国后的合作者;身为教师,他的学生中有像理查德·费曼这样的知名人物……惠勒始终身处20世纪物理学的核心。他在想象力上独具天赋,是他发明了“黑洞”这一术语,并使其流行起来。他的名字与早期关于如何思考量子时空的深入考察联系在一起,经常比数学还要直观。他吸取了布朗斯坦的经验,明白引力场的量子性质意味着在微小尺度上需要对空间概念进行修正。惠勒在寻找有助于构想这种量子空间的崭新观念,他把量子空间想象为一群重叠的几何物体,就像我们把电子看作电子云一样。 想象你正从非常高的地方看海:你会看到巨大辽阔的海洋,平坦蔚蓝的海面。现在你往下降了一些,更近地注视它,能开始看清风吹起的海浪。继续下降,你看见海浪散开,海平面是波涛汹涌的泡沫。这就是惠勒想象出的空间的样子。" 从《现实不似你所见》注释链接找过来的中国读者。2333

Oh well, one tries to see what qualitative features there are. And nobody who deals with radiation or molecules can be unaware that in a molecule, say a hydrogen molecule, with two hydrogen atoms, even at the absolute zero temperature, those two hydrogen atoms are not sitting quietly at a fixed separation from each other, they're 'wiggle wagging'. The so-called zero point energy, a minimum, irreducible energy that can't be got rid of. And that same feature of minimum, irreducible activity, obtains for the electromagnetic field through space, and the gravitational field, this 'wiggle waggling' all the time. What we think of as smooth, simple space, is really a 'wiggly' business. I don't know any better image for it than the look of the ocean as one comes down from a plane high above the ocean, that seems to be a perfectly smooth surface. You come down closer, you see the waves, and as you get still closer you see the waves breaking and you see foam. I think it must be the same in the geometry of space, for all our everyday experience, the geometry of space is smooth and flat. But as we examine it more closely, it must show oscillations. And still more closely, it must show foam, a foam-like structure. And that means that down at the very smallest distances, this idea of before and after really lose their meaning. Very small distances means what? It's so interesting that Max Planck, the great German physicist who had done so much to understand radiation and set us on the track to the quantum, had, in the study of radiation, recognized a new constant of nature. And that constant, combined with the known constants of nature, the speed of light and the constant of gravitation, define a certain standard of length, certain standard of time and certain standard of mass. Planck's notation is not quite in tune with today's, but you tune it into accord with today's notation you find yourself led to a length and a mass and a time which I called the Planck length, the Planck Mass, the Planck Time. And it's at that enormously small scale, fantastically small scale, that space must have this foam-like character. Will we see any evidence of that in time to come? We surely will, but I'm not bright enough to see where the first key test will show up. I like the idea of Planck and of Karl Popper, the philosopher of science, Popper saying that the test of a scientific idea is: a) its surprise, and b) its success in surviving tests.

John Wheeler, one of the world's most influential physicists, is best known for coining the term 'black holes', for his seminal contributions to the theories of quantum gravity and nuclear fission, as well as for his mind-stretching theories and writings on time, space and gravity.

Listeners: Ken Ford

Ken Ford took his Ph.D. at Princeton in 1953 and worked with Wheeler on a number of research projects, including research for the Hydrogen bomb. He was Professor of Physics at the University of California and Director of the American Institute of Physicists. He collaborated with John Wheeler in the writing of Wheeler's autobiography, 'Geons, Black Holes and Quantum Foam: A Life in Physics' (1998).

Duration: 4 minutes, 59 seconds

Date story recorded: December 1996

Date story went live: 24 January 2008