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凯西女士 托福听力 sat gre 第七年
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5.43 Did the sunspots cause the geomagnetic fields or did the geomagnetic fields cause the sunspots? Or is there some other thing that caused both? And astronomers did eventually figure out what
sunspots had to do with magnetic fields. And the fact that sunspots are magnetic fields accounts for their dark appearance.
5.44 They took on a life of their own and they inspired the medieval imagination, spurred on the age of discovery in the 14th and 16th centuries. When famous explorers like Columbus and da Gama and Magellan left Europe in their ships, they weren’t looking for a new world.; they were looking for spices. .
5.45 Now, what’s interesting is that birds have different levels of performance of these distraction displays. They don’t give their top performance, their prime time performance, every time. What they do is they save their best performances, their most conspicuous and most risky displays, for the time just before the baby birds become able to take care of themselves. And they time it that way because that’s when they’ll have made the greatest investment in parenting their young. So they’re not gonna put on their best performance just after they’ve laid their eggs because they haven’t invested that much time or energy in parenting yet. The top performances are gonna come later.
5.46 So we have to ask---- could these points have served another purpose? Maybe they weren’t just tools. Look at it that way. When the Clovis people first arrived in the Americas, they had a lot to learn about their new environment. Over time, they would have begun to recognize some places as special, important for some reason. Maybe there was always water available there. Or the hunting was especially good. So maybe the caches was a way to mark the place as significant.
5.47 But when you have a large population, well, the whole population can't just get up and move to follow a wild herd of animals. So you need sophisticated technologies to produce enough food for everyone. And there is an increase need to resolve social problems that arise as people begin to compete for resources. To manage intensified food production, to collect, store and distribute food, you need centralized decision-making, centralized decision-makers.为了集中管理食物，收集和分配食物，你需要集中的做决定，集中的决策者
5.48
Of course part of what made this find so unusual is that the Antikythera Mechanism is constructed of bronze. Now, it is not that bronze was all that rare in Greece then, it is just that bronze was valuable and could easily be recycled. It would have been relatively easy for a person with knowledge of metals to melt down bronze objects and forge them into…well, say, coins. Bronze was used to make money back then. Or mold the bronze into anything else of value for that matter. We are very fortunate that the device ended up under water, because otherwise it probably would have ended up recycled into…who knows what.我们很幸运这个仪器被水淹没，不然的话它有可能被循环成了别的什么东西
5.49 Ok. Now I need to mention another thing about photosynthesis. I didn’t explain how different wavelengths of light affect photosynthesis. When a plant absorbs light for performing photosynthesis, it only absorbs some wavelengths of light and reflects others.吸收一些波长的光而把其它波长反射出去 Plant absorb most of the red light that hits them, but plants only absorb
some of the far-red light that hits them.They refelt the rest. Remember this, because it is going to be relevant in an experiment I want to discuss.
This fascinating experiment showed that plants not only detect and react to specific wavelengths of light, plants can also detect and react to changes in the ratio of one wavelength to another. This experiment was called the Pampas experiment.
The idea behind the Pampas experiment had to do with the response of plants to changes in the ratio of red light to far-red light that the plants sense with their photoreceptors.Some biologists hypothesize that a plant will stop growing if it’s in the shade of another plant, a reaction that’s triggered when it senses an unusual ratio of red light to far-red light.如果一株植物在另外一株植物的阴影下它会停止生长，因为它感受到了一个红外线和远红外线的不正常比率
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