[SQUEAKING]
你还记不记得 Do you forget the difference between a solar and lunar
日食和月食的区别？ eclipse, too?
一个是像这样 One looks like this.
晴天突然就阴暗下来 And the sunny day suddenly becomes dark.
另一个则是一轮满月逐渐晦暗 And the other is a full moon that gets darker and darker.
月食是由于月亮遮住了 A lunar eclipse is when the moon is blocking the light
来自太阳的光 from the sun.
来自太阳的光 Wait a minute.
不行 No.
我改主意了 I changed my mind.
瞧 See?
不只是我们记不住 It's not just us.
这儿有三种方法来记住二者的差别 Here are three different ways to remember which is which.
有些困惑可能来源于 Some of the confusion probably comes
不知道“食”这个字是什么意思 from not knowing exactly what the word eclipse means.
它的意思是遮挡住了天体的光 It's an obscuring of the light from one celestial body.
所以日食和月食的名字意味着 So the name of the eclipse tells you
是哪一个天体显得暗淡无光 which one is getting darker.
在日食现象中 太阳 或者说拉丁语里的Sol 会变暗 In a solar eclipse, the sun or Sol in Latin, get darker.
而在月食现象里 月亮 或者说拉丁语里的Luna 会变暗 In a lunar eclipse, the moon or luna in Latin, gets darker.
日食之中 日无光 Solar eclipse, sun is eclipsed.
月食之中 月无光 Lunar eclipse, moon is eclipsed.
简单吧 Easy.
日食和月食的名字还表明 The name of the eclipse also tells you
观测现象的时候该看哪个天体 which thing to look at if you want to see the eclipse.
如果我想看一次日食 If I want to see a solar eclipse,
那么我就该观察太阳并戴上特殊定制的眼镜 I look at the sun with specially designed glasses
这样才不会灼伤视网膜 so I don't burn my retina.
如果想看的是月食的话 If I want to see a lunar eclipse,
我直接盯着月亮看就好 I look at the moon with my bare eyes.
裸眼就行 That's fine.
如果你就是记不住名字 If you just can't remember the names,
而且又很想知道 and you really want to know what's
日食月食的时候发生了什么 现在就来解释一下 going on with a solar and lunar eclipse, here's what.
日食是太阳被遮住了光 A solar eclipse is when the sun gets
因为月亮从地球和太阳 blocked because the moon is passing
之间经过 between Earth and the sun.
月球遮住了阳光 并向地球投射了一道阴影 The moon blocks light from the sun, casting a shadow on Earth.
你甚至都可以在家里模拟一下 You could even do this at home.
拿两个球状物来代表月球和地球 Get a ball for the moon and the Earth and a flashlight
再拿一个手电筒来代表太阳 to represent the sun.
从地球上看 要想遮住来自太阳的光 Looking from Earth, we want to block the light from the sun
月球就必须位于二者之间 so the moon must pass between the two.
看到了吗 See that?
能看见地球上的投影 You can see the shadow cast on Earth.
当然从地球上也能看见太阳被遮挡 And from Earth, of course, we would see an obscured sun.
所以日食的时候 天体排列的顺序为 太阳 月亮 地球 So during a solar eclipse, the order goes sun, moon, earth.
月食是指月亮的光被遮挡 A lunar eclipse is when the moon gets darker,
因为地球从太阳和月亮之间经过 because the Earth passes between the sun and the moon.
从而使地球的阴影投射在月球上 So Earth's shadow is cast on the moon.
也可以在家里模拟一下月食 只要让地球 Try this at home by passing Earth between your flashlight
从月球和手电筒之间通过就好 and the moon.
从地球往月球上看 Now looking from Earth to the moon,
我们就能看见地球的阴影了 we see the shadow of Earth.
在月食过程中 天体的顺序是 During a lunar eclipse, the order of the bodies
太阳 地球 月亮 is sun, earth, moon.
这样就有一个简单的小口诀 So now you have a useful little chant.
日食日月地 月食日地月 Solar SME, lunar SEM.
抱歉 Sorry.
现在你知道什么食是食什么了 Now that you know which eclipse is which,
我们就能聊点酷炫的东西了 we can talk about the cool stuff,
如果你站在月球上 like the fact that if you were on the moon,
月食就应该叫日食 a lunar eclipse would be a solar eclipse.
什么 What?
仔细想想 Think about it.
如果你住在月球上 If you were on the moon, and the Earth
地球从你和太阳之间经过 passed between the sun and you, you
你就会发现太阳被遮住了 would see the sun go away, because you'd
因为你正处于地球阴影的笼罩之中 fall into Earth's shadow.
要我说的话 这其实就是日食 But now from your point of view, that's a solar eclipse.
有点酷炫 不过比不上接下来的事 Pretty cool, but not as cool as the stuff
你其实能推测出日食或者月食发生的时候的自然周期 you can figure out if you know when
比如当时的月相是什么 an eclipse is happening, like what phase the moon will be in.
在整个月食的过程中 处于什么月相呢 During a total lunar eclipse, what phase is the moon in?
会是满月吧 Ah, it'll be a full moon.
满月 I guess full.
那么在日食中呢 WOMAN: What about during a solar eclipse?
新月 It's a new moon.
接下来会是新月吧 So the moon would have to be new.
还可以推测出潮汐周期 You can also figure out what the tide will be.
月食的时候 潮汐处于什么位置呢 During a lunar eclipse, what are the tides doing?
达到潮高最大值 They are maximal.
所以月食的时候一直是高潮吧 During a lunar eclipse, still gonna be high tide.
差不多每29天出现一次满月 So a full moon happens every 29 days or so.
那我们为什么不总能看见月食呢 Then why don't we see lunar eclipses all the time?
好吧 月球公转的轨道和地球公转的轨道之间 Well, the orbit of the moon is on a slight tilt
有一个细微的倾角 compared to the orbit of Earth around the sun.
所以就算满月的时候 So at this time of year, when the Earth
地球位于月球和太阳之间 is between the moon and the sun, it
三者也未必能连成一条直线 won't be a direct line between all three.
不过地球运转到这个位置的时候 When the earth moves over here, though,
这轮满月才能与太阳和地球形成一条直线 the full moon position creates a straight line,
使之完全被地球所遮挡 putting the moon right in Earth's shadow.
同样的情况还发生在地轨的这个位置 The same happens when we move Earth over here.
如果一年里有两次月食 If there are two lunar eclipses in the same year,
它们之间应该隔了六个月 they happen about six months apart,
因为这是两次月食发生的位置之间 because that's this time between the correct positions
地球运转的时间 for a lunar eclipse
很酷吧 Cool, huh?
但其实并不是精准的六个月 But it's not exactly six months in between.
事实上 一般会有177天 In fact, it's always about 177 days.
为什么不刚好是六个月呢 Why do you think it's not exactly six months?
好吧 OK.
再来个问题哈 One more question for ya.
全日食和全月食 There are about the same number of total lunar
发生过的次数基本一样多 and total solar eclipses that happen, about 60 every 100
都是差不多每一百年60次 years or so.
不过我们看见过的月食要频繁得多 But we see lunar eclipses so much more often.
这是为什么呢 Why is that?
这和月食和日食的过程中 Well, it has to do with the size of the shadow involved
行星影子的大小有关 in the eclipse.
地球比月球大这么多 The Earth is so much bigger than the moon
以至于地球的影子投射至月球的时候 that when it's shadow is cast on the moon,
处于夜晚的那半球 the entire nighttime side of the Earth
全部能看见月食 除非被云层遮挡 can see the eclipse unless it's cloudy.
月球的影子 On the other hand, the shadow cast by the moon
其实也是这样 is more like this.
但它要小很多 It's a lot smaller.
所以日食只能被月球阴影下的 So the solar eclipse is only visible to this small portion
那一小部分地区的人看见 of the Earth, the part in the moon's shadow.
事实上 这种事发生的概率极其之低 In fact, it's so unlikely for this to happen,
同一个地区的人要看一次全日食 the same part of the Earth will see a total solar eclipse
差不多要隔375年 about once every 375 years.
这是2017年即将发生的 This is what the path of the upcoming eclipse in 2017
日食观测区域的样子 will look like.
只有这块狭小条域里的人 Only those within that narrow band
才能看见这次全日食 will be able to see the total solar eclipse.
这就是有关日食月食的有趣知识啦 That's it for sweet facts about eclipses.
[SLURPS] Real sweet.
要了解更多有趣的物理知识 你可以订阅 For more fun physics, you can subscribe.
在推特和脸书上搜我的名字吧 Find me on Twitter or Facebook.
感谢收看 Thanks for watching!
[MUSIC PLAYING]