万物简史 第184期:爱因斯坦的宇宙(27)
Combining Leavitt's cosmic yardstick with Vesto Slipher's handy red shifts, Edwin Hubble now began to measure selected points in space with a fresh eye. In 1923 he showed that a puff of distant gossamer in the Andromeda constellation known as M31 was
万物简史 第185期:爱因斯坦的宇宙(28)
This was truly startling. The universe was expanding, swiftly and evenly in all directions. It didn't take a huge amount of imagination to read backwards from this and realize that it must therefore have started from some central point. Far from bein
万物简史 第186期:爱因斯坦的宇宙(29)
At all events, Hubble failed to make theoretical hay when the chance was there. Instead, it was left to a Belgian priest-scholar (with a Ph.D. from MIT) named Georges Lema?tre to bring together the two strands in his own fireworks theory, which sugge
万物简史 第187期:威力巨大的原子(01)
9 The Mighty Atom 第九章 威力巨大的原子 While Einstein and Hubble were productively unraveling the large-scale structure of the cosmos, others were struggling to understand something closer to hand but in its way just as remote: the tiny an
万物简史 第188期:威力巨大的原子(02)
They are also fantastically durable. Because they are so long lived, atoms really get around. Every atom you possess has almost certainly passed through several stars and been part of millions of organisms on its way to becoming you. We are each so a
万物简史 第189期:威力巨大的原子(03)
Above all, atoms are tinyvery tiny indeed. Half a million of them lined up shoulder to shoulder could hide behind a human hair. On such a scale an individual atom is essentially impossible to imagine, but we can of course try. 而且，原子很小确实
万物简史 第190期:威力巨大的原子(04)
It is of course the abundance and extreme durability of atoms that makes them so useful, and the tininess that makes them so hard to detect and understand. The realization that atoms are these three thingssmall, numerous, practically indestructiblean
万物简史 第191期:威力巨大的原子(05)
There, in a short chapter of just five pages (out of the books more than nine hundred), people of learning first encountered atoms in something approaching their modern conception. Daltons simple insight was that at the root of all matter are exceedi
万物简史 第192期:威力巨大的原子(06)
The work made Dalton famousalbeit in a low-key, English Quaker sort of way. In 1826, the French chemist P .J. Pelletier traveled to Manchester to meet the atomic hero. Pelletier expected to find him attached to some grand institution, so he was astou
万物简史 第193期:威力巨大的原子(07)
For a century after Dalton made his proposal, it remained entirely hypothetical, and a few eminent scientistsnotably the Viennese physicist Ernst Mach, for whom is named the speed of sounddoubted the existence of atoms at all. Atoms cannot be perceiv
万物简史 第194期:威力巨大的原子(08)
Physicists are notoriously scornful of scientists from other fields. When the wife of the great Austrian physicist Wolfgang Pauli left him for a chemist, he was staggered with disbelief. Had she taken a bullfighter I would have understood, he remarke
万物简史 第195期:威力巨大的原子(09)
Physically he was big and booming, with a voice that made the timid shrink. Once when told that Rutherford was about to make a radio broadcast across the Atlantic, a colleague drily asked: Why use radio? He also had a huge amount of good-natured conf
万物简史 第196期:威力巨大的原子(10)
In the beginning Rutherford worked on radio waves, and with some distinctionhe managed to transmit a crisp signal more than a mile, a very reasonable achievement for the timebut gave it up when he was persuaded by a senior colleague that radio had li
万物简史 第197期:威力巨大的原子(11)
In 1910, Rutherford (assisted by his student Hans Geiger, who would later invent the radiation detector that bears his name) fired ionized helium atoms, or alpha particles, at a sheet of gold foil. To Rutherford's astonishment, some of the particles
万物简史 第198期:威力巨大的原子(12)
Let us pause for a moment and consider the structure of the atom as we know it now. Every atom is made from three kinds of elementary particles: protons, which have a positive electrical charge; electrons, which have a negative electrical charge; and
