Placeholder Image

字幕列表 影片播放

  • [music]

  • [music] Narrator: If you looked at the moon over the course of a few weeks, you'd probably

  • notice that it looks slightly different every day. The change in its shadow is based on

  • where the moon is in its orbit. We call this cycle the phases of the moon, and it occurs

  • roughly once a month. At least twice a year, however, something quite different

  • happens. The moon passes through the shadow cast by the Earth, causing it to look extremely

  • unusual for a short period of time. From the earth, the moon will appear to

  • darken and turn a deep red before eventually returning to normal. This is called a lunar

  • eclipse. If we were to look at what happens from space during an eclipse, it would go

  • something like this. First, the moon passes through what's called the penumbra,

  • where the sun's light is only partially obscured. This results in only a slight darkening

  • of the moon. As the moon continues along its path, however, it enters what's

  • called the umbra, where all direct light from the sun is blocked. But if the sun is blocked,

  • why does the moon turn red? When light from the sun goes by the side of the Earth,

  • it passes through a long and thick layer of Earth's atmosphere. Shorter wavelengths

  • of sunlight, like blue, are scattered by the atmosphere, so by the time the light has finished

  • its trip to the moon, more of the longer wavelengths, like red, are left over.

  • On the Earth, the same thing happens at sunset as the ground you stand on gradually passes

  • into night. As the eclipse ends, the moon leaves the umbra, returns

  • to its normal color, and then leaves then penumbra, brightening and resuming its original

  • cycle. Overall, the whole process lasts only from a few minutes to a few hours,

  • so you'll have to be quick if you want to see it. But, as long as you're willing to stay awake,

  • you'll catch the moon as you won't see it too often.

  • [music, beeping]

  • [music, beeping]

  • [music]

  • [silence]



影片操作 你可以在這邊進行「影片」的調整,以及「字幕」的顯示

B1 中級 美國腔

NASA|月食要點 ◘月食全攻略 [CC字幕] (NASA | Lunar Eclipse Essentials ◐ 月食全攻略 [CC字幕])

  • 314 23
    劉瑞怜 發佈於 2021 年 01 月 14 日