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There are actually twenty-two naturally occurring amino acids known on Earth, 实际上，地救上有22种天然存在的氨基酸， and more may await discovery, but only twenty of them are necessary to produce us and most other living things. 更多
万物简史
Particles can come into being and be gone again in as little as 0.000000000000000000000001 second (10-24). Even the most sluggish of unstable particles hang around for no more than 0.0000001 second (10-7). 粒子可以在短达0.000 000 000 000 000 0
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Particle physics, in short, is a hugely expensive enterprisebut it is a productive one. Today the particle count is well over 150, with a further 100 or so suspected, but unfortunately, in the words of Richard Feynman, it is very difficult to underst
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Hubble realized that this could be expressed with a simple equation, Ho = v/d (where Ho is the constant, v is the recessional velocity of a flying galaxy, andd its distance away from us). Ho has been known ever since as the Hubble constant and the wh
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It is all, as you can see, just a little unwieldy, but it is the simplest model that can explain all that happens in the world of particles. Most particle physicists feel, as Leon Lederman remarked in a 1985 PBS documentary, that the Standard Model l
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On its website, a history of the company makes no mention of leador indeed of Thomas Midgleybut simply refers to the original product as containing a certain combination of chemicals. 在它的网站上，公司的历史没有提及铅──也没有提
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Absurdly, he was excluded from a 1971 National Research Council panel appointed to investigate the dangers of atmospheric lead poisoning even though he was by now unquestionably the leading expert on atmospheric lead. 荒唐的是，一个美国研究委
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As always, however, nothing was quite as straightforward as such a breezy description makes it sound. Meteorites are not abundant and meteoritic samples not especially easy to get hold of. Moreover, Brown's measurement technique proved finicky in the
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Rather than restate every one, scientists decided to keep the inaccurate constant. Thus, Tim Flannery notes, every raw radiocarbon date you read today is given as too young by around 3 percent. The problems didn't quite stop there. It was also quickl
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Buoyed by the success of leaded gasoline, Midgley now turned to another technological problem of the age. Refrigerators in the 1920s were often appallingly risky because they used dangerous gases that sometimes leaked. One leak from a refrigerator at
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As Sharon Bertsch McGrayne notes in her absorbing history of industrial chemistry, Prometheans in the Lab, when employees at one plant developed irreversible delusions, a spokesman blandly informed reporters: These men probably went insane because th
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But there were many technical difficulties to overcome. Holmes also neededor at least would very much have appreciatedsophisticated gadgetry of a sort that could make very fine measurements from tiny samples, and as we have seen it was all he could d
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Lead is a neurotoxin. Get too much of it and you can irreparably damage the brain and central nervous system. Among the many symptoms associated with overexposure are blindness, insomnia, kidney failure, hearing loss, cancer, palsies, and convulsions
万物简史
10 Getting The Lead Out 第十章 把铅撵出去 In the late 1940s, a graduate student at the University of Chicago named Clair Patterson (who was, first name notwithstanding, an Iowa farm boy by origin) was using a new method of lead isotope measur
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Remarkably, the phenomenon was proved in 1997 when physicists at the University of Geneva sent photons seven miles in opposite directions and demonstrated that interfering with one provoked an instantaneous response in the other. 令人惊叹的是，这
万物简史
Neutrons and protons occupy the atom's nucleus. The nucleus of an atom is tinyonly one millionth of a billionth of the full volume of the atombut fantastically dense, since it contains virtually all the atom's mass. As Cropper has put it, if an atom
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In 1907, or so it has sometimes been written, Albert Einstein saw a workman fall off a roof and began to think about gravity. 1907年，反正有时候书上是这么写的，有个工人从房顶上掉了下来，爱因斯坦就开始考虑引力的问
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In 1919, now aged thirty, he moved to California and took up a position at the Mount Wilson Observatory near Los Angeles. Swiftly, and more than a little unexpectedly, he became the most outstanding astronomer of the twentieth century. 1919年，他已
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Howeverand heres the thingpeople on the train would have no sense of these distortions. 然而问题就在这里车上的人并不觉得自己变了形。 To them, everything on the train would seem quite normal. 在他们看来，车上的一切似乎
万物简史
You might not think there would be that many people in the world prepared to devote lifetimes to the study of something so inescapably low key, 你或许会认为，世界上不会有多少人愿意花毕生的心血来研究那个不起眼儿的东西
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