托福听力天文学：太阳黑子

　　在托福听力考试中，天文学的内容相对来说难度比较大。因此大家在复习的时候，可以多参考一些译文，帮助大家更好的来了解相关的内容，供大家参考。下面就是关于“太阳黑子”的背景知识。

　　We are going to start a study of sunspots today, and I think you'll find it rather interesting. Now I'm going to assume that you know that sunspots, in the most basic terms, are dark spots on the Sun's surface. That will do for now.

　　The ancient Chinese were the first to record observations of sunspots as early as the year 165. When later European astronomers wrote about sunspots, they didn't believe that the spots were actually on the Sun. That's because of their belief at the time that the heavenly bodies, the Sun, Moon, Stars, and Planets, were perfect, without any flaws or blemishes【test point】. So the opinion was the spots were actually something else, like shadows of planets crossing the Sun's face. And this was the thinking of European astronomers until the introduction of the telescope, which brings us to our old friend, Galileo.

　　In the early 1600s, based on his observations of sunspots. Galileo proposed a new hypothesis. He pointed out that the shape of sunspots, well, the sunspots weren't circular. If they were shadows of the planets, they would be circular, right? So that was a problem for the prevailing view. And he also noticed that the shape of the sunspots changed as they seemed to move across the Sun's surface. Maybe a particular sunspot was sort of square, then later it would become more lopsided, then later something else. So there is another problem with the shadow hypothesis, because the shape of a planet doesn't change. What Galileo proposed was that sunspots were indeed a feature of the Sun, but he didn't know what kind of feature. He proposed that they might be clouds in the atmosphere, the solar atmosphere, especially because they seemed to change shape and there was no predicting the changes, at least nothing Galileo could figure out. That random shape changing would be consistent with the spots being clouds.

　　Over the next couple hundred years, a lot of hypotheses were tossed around. The spots were mountains or holes in the solar atmosphere through which the dark surface of the Sun could be seen. Then in 1843, astronomer named Heinrich Schwa be made an interesting claim, Trobe had been watching the Sun every day that it was visible for 17 years, looking for evidence of a new planet. And he started keeping tracks of sunspots, mapping them, so he wouldn't confuse them, so he wouldn't confuse them with any potential new planet. In the end, there was no planet, but there was evidence that the number of sunspots increased and decreased in a pattern, a pattern that began repeating after 10 years, and that was a huge breakthrough.

　　Another astronomer named Wolf kept track of the Sun for an even longer period, 40 years actually. So Wolf did 40 years of research, and Trobe did 17 years of research. I think there is a lesson there. Anyway, Wolf went though all records from various observatories in Europe and put together a history of sunspot observations going back about 100 years. From this information, he was able to confirm the existence of a pattern, a repeating cycle but Wolf detected an 11-year cycles? Dose that sound familiar to anyone? No? Well, geomagnetic activity, the natural variations in Earth's magnetic field, it fluctuates in 11-year cycles. Well, we'll cover this later in this semester, but for now, well, scientists in the late 19th century were aware of geomagnetic cycles, so when they heard that the sunspots' cycle was also 11 years, well, they just had to find out what was going on.

　　Suddenly, everyone was doing studies of the possible relationship between the Sun and the Earth. 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. That's because magnetic fields reduce the pressure exerted on the gases inside of them, making the spots cooler than the rest of the Sun's surface. And since they are cooler, they are darker.

　　今天我们将要学习的主要内容是太阳黑子，我觉得你们应该会觉得这非常有趣吧!接下来我将会假定你们对太阳黑子的认识，说得通俗些，就是太阳脸上的黑斑。这个理解现在还说得通。早在公元165年，中国人就第一个观测并记录了太阳黑子的活动。等到后来欧洲天文学家谈论太阳黑子的时候，他们不敢相信，这些斑点真的就在太阳上。那是因为，当时他们认为，天上飘动的天体，包括太阳、月亮、行星，是完美的，没有任何缺点和污渍。所以，当时他们的看法是，那些黑点肯定是别的什么东西，比如其他行星经过太阳时留下的阴影。并且，当时欧洲的天文学家们大部分都这么认为。直到望远镜引入——这让我们想到了我们的老朋友伽利略——之后才发生变化。在公元1600年早期，在伽利略长期对太阳黑子的观测经验的基础上，他提出了一项新的假设。他指出，太阳黑子的形状并不是正圆的。但如果它们真的是行星的投影的话，它们当然应该是正圆形的，不是吗?

　　所以这个问题，对先前的认识提出了挑战。并且，伽利略还指出，太阳黑子似乎在太阳表面移动，而且在移动中形状不断发生变化。这个观点，对太阳黑子为投影说又提出了另一个问题，因为一个行星的形状是不变的，它影子的形状也似乎不变的。不过，伽利略提出的理论，总体上把太阳黑子归结于太阳自身的特征;他自己并不知道这个特征到底是什么。所以，他又认为，太阳可能有大气，而且大气中可能存在云层。他这项假设特别重要的根据是太阳黑子的形状是变化的，变化方式是不可预计的，或者说，这种变化的模式至少是伽利略观测不出来的。伽利略认为，太阳黑子的随机性变化与它们作为太阳大气云层这一假设是一致的。之后的几百年里，又有一大批理论被提出来。透过太阳暗色的表面，人们观测到了太阳黑子是太阳大气中的山或者洞穴。然后，在1843年，一个叫海因里希舒华的天文学家提出了一个有趣的假设。卓伯在能够观测到太阳的期间，连续观测了太阳17年，本来他这种努力，是想要寻找一颗新的行星。之后，他开始追踪太阳黑子的变化，并记录它们的变化轨迹，这样一来，他就能把太阳黑子一颗一颗认出来，不会把它们误认为是新的行星。最后，他没有观测到行星，但他发现，太阳黑子消长是非常有规律的，以10年为一个重复周期，这项发现无疑是一个非常重大的突破。

　　另一位叫做沃尔夫的天文学家观测太阳的时间更长，达到了惊人的40年。沃尔夫观测了40年，卓伯观测了17年，我觉得这对我们来说，是一个模范。沃尔夫查看了欧洲各种观测记录，综合了他之前100年到他生活时代的材料中关于太阳黑子的运动历史，得出了一个新的运动周期，和卓伯不同，沃尔夫把这个周期定为11年，这你们听上去熟悉吗?不熟悉?嗯，地磁运动，即地球磁场的自然运动，它的周期就是11年。嗯，这个部分的内容我们会在这学期讲到，现在我们就稍微简单的提一下吧!嗯，19世纪的科学家们已经知道了地磁圈的存在，所以，当他们听到太阳黑子的运动周期是11年时，他们就必须要知道背后的事实是什么。一时间，几乎所有人都把目光放到了太阳和地球之间的关系上：是太阳黑子引发了地球磁场，还是地球磁场引发了太阳黑子?或者，有第三者的存在，它同时引发了地球磁场和太阳黑子?最终，天文学家发现了太阳黑子与地球磁场之间的关系。事实是，太阳黑子解释了为何太阳表面在观测中呈现出深黑色，原因是太阳地磁场减轻了它们内部的气体施加的压力，使得太阳表面的黑子比其余地方的温度低。当然，温度越低，在观测中颜色也就越深。

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