万物简史:PART III CH 9威力巨大的原子（13）
Neutrons and protons occupy the atom's nucleus. The nucleus of an atom is tiny—only one millionth of a billionth of the full volume of the atom—but [-1-] dense, since it contains virtually all the atom's mass. [---2---] It was this spaciousness—this resounding, unexpected roominess—that had Rutherford scratching his head in 1910.
It is still a fairly astounding notion to consider that atoms are mostly empty space, and that the solidity we experience all around us is an [-3-]. When two objects come together in the real world—[-4-]—they don't actually strike each other. "[-5-]," as Timothy Ferris explains, "the negatively charged fields of the two balls repel each other . . . [---6---]." When you sit in a chair, you are not actually sitting there, but levitating above it [---7---] one angstrom (a hundred millionth of a centimeter), your electrons and its electrons implacably opposed to any closer intimacy.