第1552期:Why leap years aren’t every 4 years

第1552期:Why leap years aren’t every 4 years

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2020 is a leap year, and as we all know leap years happen every four years, right? Wrong. That extra day in February is designed to keep the Earth in sync with the astrological or seasonal year. But, what you might not realise is that the maths isn’t that simple and occasionally we have to wait eight years.

2020年是闰年,众所周知,闰年每四年发生一次,对吧?错误的。2 月额外的一天旨在使地球与占星术或季节年保持同步。但是,您可能没有意识到数学并不是那么简单,有时我们不得不等待八年。


The method behind calculating when leap years occur might be a bit more complicated than you think. Way back in 1582 the calendar we now use was first implemented. The Gregorian calendar was named after the pope at the time, Gregory X1V. The people who created it realised it wasn’t perfect to just add an extra day every four years.

计算闰年发生时间的方法可能比您想象的要复杂一些。早在 1582 年,我们现在使用的日历就首次实现了。公历以当时的教皇格列高利 X1V 命名。创建它的人意识到每四年增加一天并不完美。


Here’s where the maths comes in. A day, of course, is measured by the amount of time it takes for the Earth to complete one full rotation on its axis. A year is the number of days it takes the Earth to orbit the Sun, which most people assume is 365. However, the Earth actually takes just under 365 and a quarter days to complete one full revolution around the Sun.

这就是数学的用武之地。当然,一天是根据地球绕其轴完成一整圈所需的时间来衡量的。一年是地球绕太阳公转一周所需的天数,大多数人认为是 365 天。然而,地球实际上需要不到 365 天又四分之一天的时间完成绕太阳一周的运行。


So, every four years we get an extra day, which falls on the 29th February. However, as mentioned earlier, it is in fact just under a quarter of a day. So, by rounding it up, we put the calendar out of sync again – which means that after a while we have too many days.

因此,每四年我们就会多得到一天,即 2 月 29 日。但是,如前所述,实际上不到四分之一天。因此,通过四舍五入,我们再次使日历不同步——这意味着一段时间后我们的日子太多了。


That imbalance has to be readdressed, otherwise after 400 years you’d end up with three extra days. So back in 1582, they realised that every turn of a century should skip their extra day to subtract those three extra days. This is why the years 1700, 1800, and 1900 weren’t leap years.

这种不平衡必须重新解决,否则在 400 年后你会多出三天。所以早在 1582 年,他们就意识到每个世纪都应该跳过额外的一天来减去这三天的额外时间。这就是为什么 1700、1800 和 1900 年不是闰年的原因。


But wait, there’s more. The year 2000, the millennium, was a leap year. That’s because over a period of four hundred years we only need to remove three days. So, every 400 years the turn of the century is a leap year. This means the next time you hear someone saying ‘leap years happen every four years’ you can tell them why they’re wrong.

但是等等,还有更多。2000年,千禧年,是闰年。那是因为在四百年的时间里,我们只需要除去三天。所以,每400年世纪之交就是一个闰年。这意味着下次你听到有人说“闰年每四年发生一次”时,你可以告诉他们为什么他们错了。


词汇表

in sync 同步的

astrological 占星学的
seasonal year 一年四季
calculate 计算
calendar 日历
measure 测量
rotation 旋转一圈
axis 轴线,中心线
orbit 轨道
revolution 旋转
round up 把数字调高成为整数
out of sync 不同步
imbalance 不均衡
turn of a century 世纪之交
millennium 千禧年



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