万物简史 第244期:马斯特-马克的夸克(16)
This uncertainty applies, incidentally, to relatively nearby things as much as to the distant edges of the universe. As Donald Goldsmith notes, when astronomers say that the galaxy M87 is 60 million light-years away, what they really mean (but do not
万物简史 第245期:马斯特-马克的夸克(17)
At least the names for the two main possible culprits are entertaining: they are said to be either WIMPs (for Weakly Interacting Massive Particles, which is to say specks of invisible matter left over from the Big Bang) or MACHOs (for MAssive Compact
万物简史 第246期:马斯特-马克的夸克(18)
This is counter to all expectations. It appears that the universe may not only be filled with dark matter, but with dark energy. Scientists sometimes also call it vacuum energy or, more exotically, quintessence. Whatever it is, it seems to be driving
万物简史 第247期:大地在移动(1)
12 The Earth Moves 第十二章 大地在移动 In one of his last professional acts before his death in 1955, Albert Einstein wrote a short but glowing foreword to a book by a geologist named Charles Hapgood entitled Earth's Shifting Crust: A Key to
万物简史 第248期:大地在移动(2)
Taylor came from a wealthy family and had both the means and freedom from academic constraints to pursue unconventional lines of inquiry. He was one of those struck by the similarity in shape between the facing coastlines of Africa and South America,
万物简史 第249期:大地在移动(3)
Wegener developed the theory that the world's continents had once come together in a single landmass he called Pangaea, where flora and fauna had been able to mingle, before the continents had split apart and floated off to their present positions. A
万物简史 第250期:大地在移动(4)
There was also the problem, demonstrated by Rutherford and Soddy early in the century, that Earthly elements hold huge reserves of heatmuch too much to allow for the sort of cooling and shrinking Suess suggested. And anyway, if Suess's theory was cor
万物简史 第251期:大地在移动(5)
When it was realized that ancient tapirs had existed simultaneously in South America and Southeast Asia a land bridge was drawn there, too. Soon maps of prehistoric seas were almost solid with hypothesized land bridgesfrom North America to Europe, fr
万物简史 第252期:大地在移动(6)
To be sure, Wegener made mistakes. He asserted that Greenland is drifting west by about a mile a year, which is clearly nonsense. (It's more like half an inch.) Above all, he could offer no convincing explanation for how the landmasses moved about. T
万物简史 第253期:大地在移动(7)
Elsewhere, however, the new theory drew steady if cautious support. In 1950, a vote at the annual meeting of the British Association for the Advancement of Science showed that about half of those present now embraced the idea of continental drift. (H
万物简史 第254期:大地在移动(8)
There was one other major problem with Earth theories that no one had resolved, or even come close to resolving. That was the question of where all the sediments went. Every year Earth's rivers carried massive volumes of eroded material500 million to
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It was scored everywhere with canyons, trenches, and crevasses and dotted with volcanic seamounts that he called guyots after an earlier Princeton geologist named Arnold Guyot. All this was a puzzle, but Hess had a war to take part in, and put such t
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A very little of this had been known for some time. People laying ocean-floor cables in the nineteenth century had realized that there was some kind of mountainous intrusion in the mid-Atlantic from the way the cables ran, but the continuous nature a
万物简史 第257期:大地在移动(11)
That explained where all the sediment went. It was being returned to the bowels of the Earth. It also explained why ocean floors everywhere were so comparatively youthful. None had ever been found to be older than about 175 million years, which was a
万物简史 第258期:大地在移动(12)
but in the 1950s Patrick Blackett of the University of London and S. K. Runcorn of the University of Newcastle studied the ancient magnetic patterns frozen in British rocks and were startled, to say the very least, to find them indicating that at som
