SAT阅读中的科学文章

SAT阅读中的科学文章了解了SAT阅读中常考的黑人、女人以及亚非拉等生活在美国的少数名族等题材之后，并不意味着SAT阅读所有的背景知识就全部掌握了，这就要说到很多中国考生为之色变的一类题材——科学了。

由于社科教育在中国一直不被重视，导致很多考生碰到科学类题目便毫无头绪。

巴斯德的曲颈瓶实验，美洲大陆人类的迁徙过程，恐龙化石，地下湖的成因……这些文章是很多考生的“噩梦”。

生物学、人类学、考古学、地质学……林林总总的长篇大论，考生读完文章后一头雾水。

而且近些年来SAT阅读也不仅仅只是停留在过去的科学成就上，某一个学科或现象的发展、最新科学研究和发现出现得越来越多。

所以要是大家能够在平时的生活中多关注最新科学发展动态，并适时积累，对于SAT阅读考试中的科学类题目无疑是可以有很大的帮助。

今天，2月29日，在这个四年才一次的特殊日子里，许老师要跟大家分享一篇自己在《华尔街日报》上看到的关于计量时间的文章，让大家一起来了解一下地球自转速度怎样导致了闰年（leap year）、闰日（leap day）、闰秒（leap second）的出现，以及现今的计时方式使春分、秋分（spring and autumn equinox）这些现象产生了怎样的变化。

文章内容：The Drama of Measuring the Days of Our LivesHumanity's efforts to impose order on time don't always go like clockwork.There was the Y2K computer-programming fiasco, as the world entered the year 2000. Then there are the seconds that have to be added to the clock occasionally—the next one is in June—to make our definition of a day match the ever-so-slight slowing of the Earth's rotation. And spare a thought for the Swedish couple who married 300 years ago but whose anniversary has never appeared on any calendar.写在4年来最不寻常的一天 <wbr>2月29天Sven Hall wed Ellna Jeppsdotter in Ystad, Sweden, on Feb. 30, 1712—a day that existed only because of Protestant Europe's fumbling transition from the Julian calendar system to an approximation of the Gregorian system. Sweden had tried to change gradually before realizing it was out of sync with everyone else, says Bengt Danielson, assistant archivaldirector of the Demographical Database for Southern Sweden. The nation tried to get back in line by adding two leap days to 1712. But it was four decades before Sweden made the wholesale switch from the Julian calendar.In the centuries since, society has improved its reckoning of time and synchronization of watches across borders. But it continues to use a relatively ancient system for tweaking time by adding leap days—such as next week's Feb. 29—that some astronomers say isn't the ideal mathematical solution to the problem that a year is a bit longer than 365 days. Add in the unpredictable variability in the length of years, and the calendar continues to defy simple computation."The calendar isn't a mathematical thing," says Robert Poole, a historian at the University of Cumbria in Lancaster, England, and author of a book on calendar reform in England. "All attempts to systematize calendars are misguided."Yet history is dotted with attempts to systematize calendars. The Julian calendar was named for Julius Caesar, who instituted it in 46 B.C. after recognizing that the time it takes for the Earth to orbit the sun isn't neatly divisible by the time it takes for the Earth to rotate about its axis.Caesar added a leap year every four years, which was almost right. But the almost added up. Those extra leap days made the average year too long, shifting annual phenomena—such as the spring and autumn equinox—earlier than their normal seasonal dates by 10 days by 1582. Since the date of Easter is tied to the spring equinox, Pope Gregory XIII sought to overhaul the calendar, skipping 10 days and then removing three leap years every 400 years.In Gregory's time, England had just emerged from a schism with the church and wasn't eager to follow papal authority. Enter John Dee—"variously listed as an astronomer, mathematician, magician and mystic; today one might even call him a crackpot," says Geoff Chester, a spokesman for the U.S. Naval Observatory, which plays a key role in counting world time today.写在4年来最不寻常的一天 <wbr>2月29天Petr Skala walking on a ledge Friday during his weekly maintenance of the famous astronomical clock in Prague, Czech Republic. The clock was first installed in 1410, making it the third-oldest astronomical clock in the world and possibly the oldest one still working.Dee suggested to Queen Elizabeth a cycle of eight leap years every 33 years. The leap years would come every fourth year starting with the fourth of the cycle, putting a five-year gap between the last leap year of the cycle and the first of the next cycle. Dee didn't invent the system, says Duncan Steel, an astronomer at the Australian Centre for Astrobiology and author of a book about calendar history. A variant of the system remains in use in Iran today, a millennium after Persians first used one like it.The average year in the Gregorian system lasts exactly 365.2425 days, compared with the average year in the Dee system of a touch over 365.2424 days. The latter is closer to the actual time it takes the Earth to rotate around the sun, about 365.242 days, says Dr. Steel.Still, Dee was ultimately unsuccessful, and most of the world eventually fell into line with a uniform calendar.But that hasn't run out the clock on calendar problems. Another complication is that years are measured in days, and days are getting longer as tides create friction and slow the Earth's rotation. The length of the second has been fixed to the oscillation frequency of Cesium-133, using a duration that once corresponded to 1/86,400th of a day. But today—and tomorrow—are longer than the 86,400 seconds clocks world-wide include in a day by about one or two milliseconds—the gap changes daily.To rectify that shift, the world's timekeepers have agreed to add so-called leap seconds whenever the drift nears a second, typically at midnight London time—the minute starting at 11:59 p.m. has 61 seconds.As the day grows longer, somewhat unpredictably, there are fractionally fewer days in the year, and so eventually, in the very longrun, today's calendar may need to be amended once more. But then, that should be expected, says Steve Allen, an astronomer at the University of California who maintains a website with research about the leap second."It is extraordinary hubris for any civilization to presume that its calendar will still be in use in 1,000 years," he says.看完这篇文章，很多同学可能会觉得比较难，其实大家仔细找的话会发现里面没有特别复杂的词汇。