N-COUNT Sunspots are dark cool patches that appear on the surface of the sun and last for about a week. 黑子; 日斑
Anyway, Wolf went though all records from various observatories in Europe and put together a history of sunspot observations going back about 100 years.
不论如何,沃尔夫查阅了欧洲各个天文台的所有记录,并把大约100年前的太阳黑子观测历史整理在一起。
On Earth, among the surest indications of sunspot cycles are believed to be the rate that trees grow, as seen in the rings visible in the cross sections of their trunks.
在地球上,人们认为,表明太阳黑子周期最可靠的迹象之一是树木的生长速度,就像树干横截面上可见的年轮一样。
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