万物简史 第605期:冰河时代(2)
Spring never came and summer never warmed: 1816 became known as the year without summer. Crops everywhere failed to grow. In Ireland a famine and associated typhoid epidemic killed sixty-five thousand people. In New England, the year became popularly
万物简史 第606期:冰河时代(3)
They knew there was something odd about the past. The European landscape was littered with inexplicable anomaliesthe bones of arctic reindeer in the warm south of France, huge rocks stranded in improbable placesand they often came up with inventive b
万物简史 第607期:冰河时代(4)
Local peasants, uncontaminated by scientific orthodoxy, knew better, however. The naturalist Jean de Charpentier told the story of how in 1834 he was walking along a country lane with a Swiss woodcutter when they got to talking about the rocks along
万物简史 第608期:冰河时代(5)
He lent Agassiz his notesthen came very much to regret it as Agassiz increasingly got the credit for what Schimper felt, with some legitimacy, was his theory. Charpentier likewise ended up a bitter enemy of his old friend. Alexander von Humboldt, yet
万物简史 第609期:冰河时代(6)
William Hopkins, a Cambridge professor and leading member of the Geological Society, endorsed this view, arguing that the notion that ice could transport boulders presented such obvious mechanical absurdities as to make it unworthy of the society's a
万物简史 第610期:冰河时代(7)
Doubtless it helped that he had settled in New England, where the long winters encouraged a certain sympathy for the idea of interminable periods of cold. It also helped that six years after his arrival the first scientific expedition to Greenland re
万物简史 第611期:冰河时代(8)
Croll was the first to suggest that cyclical changes in the shape of Earth's orbit, from elliptical (which is to say slightly oval) to nearly circular to elliptical again, might explain the onset and retreat of ice ages. No one had ever thought befor
万物简史 第612期:冰河时代(9)
Part of the problem was that Croll's computations suggested that the most recent ice age occurred eighty thousand years ago, whereas the geological evidence increasingly indicated that Earth had undergone some sort of dramatic perturbation much more
万物简史 第613期:冰河时代(10)
Happily this was precisely the sort of repetitive toil that suited Milankovitch's temperament. For the next twenty years, even while on vacation, he worked ceaselessly with pencil and slide rule computing the tables of his cycleswork that now could b
万物简史 第614期:冰河时代(11)
The cause of ice ages, Koppen decided, is to be found in cool summers, not brutal winters. If summers are too cool to melt all the snow that falls on a given area, more incoming sunlight is bounced back by the reflective surface, exacerbating the coo
万物简史 第615期:冰河时代(12)
The Milankovitch cycles alone are not enough to explain cycles of ice ages. Many other factors are involvednot least the disposition of the continents, in particular the presence of landmasses over the polesbut the specifics of these are imperfectly
万物简史 第616期:冰河时代(13)
For most of its history until fairly recent times the general pattern for Earth was to be hot with no permanent ice anywhere. The current ice ageice epoch reallystarted about forty million years ago, and has ranged from murderously bad to not bad at
万物简史 第617期:冰河时代(14)
Before fifty million years ago, Earth had no regular ice ages, but when we did have them they tended to be colossal. A massive freezing occurred about 2.2 billion years ago, followed by a billion years or so of warmth. Then there was another ice age
万物简史 第618期:冰河时代(15)
Throughout all this the tubeworms and clams and other life forms adhering to deep ocean vents undoubtedly went on as if nothing were amiss, but all other life on Earth probably came as close as it ever has to checking out entirely. It was all a long
万物简史 第619期:冰河时代(16)
For a long time it was thought that we moved into and out of ice ages gradually, over hundreds of thousands of years, but we now know that that has not been the case. Thanks to ice cores from Greenland we have a detailed record of climate for somethi
