if you looked at the moon over the course of a few weeks 当你持续几周观察月亮
you probably noticed that look slightly different every day . 你会注意到月亮每天都会略有不同
the change in its shadow is based on where the moon is in its orbit. 月之盈亏与它在轨道上的位置有关
We call the cycle the phases of the Moon, and it occurs roughly once a month. 这就是月相，周期为一个月
At least twice a year,however,something quite different happens . 一年至少会发生两次完全不同的事情
The moon passes through the shadow cast by the earth. 此时月球将会经过地球的影子
causing it to look extremely unusual for a short period of time from the earth, 在地球上我们能看到非常短的时间内
the moon will appear to darken and turn a deep red before eventually returning to normal 月球会变暗，变成深红色,最终恢复正常
This is called a lunar eclipse . if we were to look at what happens from space during the eclipse, 这就是月食,假如我们从空间看在这次月食
it would go something like this. first, the moon passes through what's called the penumbra 它会像这样：首先,月球将经过
where the sun's light is only partially obscured . this results in only a slight darkening of the moon. 太阳光被地球部分遮挡的半影区.此时月球轻微变暗
as the Moon continues along its path, however ,it enters what's would call the Umbra, 月球继续运行，它将会进入地球的本影
where all direct light from the sun is blocked ,but if the sun is blocked, 此时 太阳光会被完全遮挡
why does the moon turn red? when ligth from the sun goes by the side of the earth, 为什么此时月亮会变红？因为当来自太阳的光，
it passes through a long and thick layer of earth's atmosphere. shorter wavelengths of sunlight ,like blue, 穿过地球厚而长大气层，太阳光中的短波，如蓝光
are scattered by the atmosphere ,so by the time the ligth has finished a trip to the moon, 会被地球大气散射掉，最后抵达月球是
more the longer wavelengths ,like red,are left over. 剩下像红光那样波长比较长的光
on the earth, the same thing happens at sunset as the ground you stand on gradually passes into night, as the eclipse ends, 在地球上，在傍晚时分随着太阳逐渐下落我们会看到类似的现象
the moon leaves the Umbra, returns to its normal color ,and then leave the penumbra 随着月全食结束，月球离开本影恢复正常颜色，之后离开半影
brightening and resuming its original cycle. 月球变亮并恢复正常周期,
overall,the whole process lasts only from a few minutes to a few hours, so you will have to be quick if you want to see it. 总之，整个过程持续仅从几分钟到几小时，所以你会一定要快速，如果你想要看到它
but ,as long as you're willing to stay awake ,you'll catch the moon as you won't see it too often. 但是，只要你愿意保持清醒，你就会赶上月亮，因为你不会太经常看到它