认识夜空的朋友：月亮是谁？

你有没有一个特别好的朋友，每天晚上都会在天上对你眨眼睛？对啦，那就是我们的月亮！

Every night, have you noticed a special friend twinkling at you in the sky? That's our Moon!

今天，我们要一起去认识这位神奇的朋友。月亮看起来像一个大大的、圆圆的白色灯球，挂在黑黑的夜空中。可是你知道吗？月亮其实并不是一盏灯哦！它不会自己发光。那么，为什么我们能看到月亮亮亮的呢？

Today, we're going to get to know this magical friend. The Moon looks like a big, round, white ball hanging in the dark night sky. But did you know? The Moon isn't actually a lamp! It can't make its own light. So why can we see the bright Moon?

让我们来做一个小实验吧。找一个手电筒，再找一个白色的球，比如乒乓球。把手电筒打开，让光照在白球上。你会发现，白球被照亮的一面变得亮闪闪的，而另一面还是暗暗的。月亮就是这样工作的！太阳公公发出超级超级亮的光，这些光照到月亮身上，月亮的表面就像一面超级大的镜子，把太阳光反射（fǎn shè）回来。反射的意思就是像弹皮球一样，把光"弹"回我们的眼睛里。所以，我们看到的月光，其实是太阳光的"回声"呢！

Let's do a little experiment. Find a flashlight and a white ball, like a ping-pong ball. Turn on the flashlight and shine the light on the white ball. You'll see that the side of the ball facing the light becomes bright and shiny, while the other side stays dark. That's exactly how the Moon works! The Sun gives off super, super bright light. When this light reaches the Moon, the Moon's surface acts like a giant mirror, reflecting the sunlight back. "Reflecting" means bouncing light back, like a bouncing ball. So the moonlight we see is actually the "echo" of sunlight!

你知道吗？太阳光从太阳跑到月亮上，再从月亮跑到我们眼睛里，只需要大约1.3秒钟！光的速度可快啦，一秒钟能跑30万公里呢。30万公里是多少呢？那相当于绕我们地球跑7圈半那么多！所以呀，光的速度真的是快得惊人。

Did you know? It only takes about 1.3 seconds for sunlight to travel from the Sun to the Moon, and then from the Moon to our eyes! Light travels incredibly fast - 300,000 kilometers per second! How far is 300,000 kilometers? That's about 7.5 times around Earth! So light is really, really fast!

现在让我们来聊聊月亮离我们有多远。月亮可是住在很高很高的地方哦！从地球到月亮的距离，大约是38万公里。这是什么概念呢？

Now let's talk about how far away the Moon is. The Moon lives way, way up there! The distance from Earth to the Moon is about 384,000 kilometers. What does that mean?

想象一下，如果你的脚有魔法，能一直走一直走，从来不用休息，也不用睡觉吃饭，你觉得走到月亮那里需要多长时间？科学家叔叔阿姨们算过了——大约需要242年！242年啊！如果你从现在开始走，一直走到公元2267年才能到达月亮。242年前的中国，还是清朝呢！那时候的人还在坐马车、点蜡烛，现在的你已经在走路去月亮啦！不过别担心，我们现在有火箭，只需要三天左右就能飞到月亮上。但是走路的话，确实需要242年呢。

Imagine if your feet had magic powers and you could keep walking forever without stopping to rest, eat, or sleep. How long would it take to walk to the Moon? Scientists have calculated it - about 242 years! 242 years! If you started walking now, you wouldn't reach the Moon until around the year 2267. 242 years ago in China, people were living during the Qing Dynasty! They were riding in carriages and using candles, while you would be walking to the Moon! But don't worry - we have rockets now, so we can fly to the Moon in only about three days. Still, if you walked, it would really take 242 years!

我们再来做一个好玩的想象。如果地球是一个篮球那么大，那么月亮有多大呢？大约只有一个网球那么大！月亮比地球小很多很多。具体来说，如果把月亮切成小块，要79个月亮才能装满一个地球那么大。79个月球堆在一起才等于一个地球！这个数字听起来是不是很惊人？不过，虽然月亮比地球小很多，它对我们来说已经非常非常大了。晚上的时候，月亮看起来好像只有盘子那么大，但实际上，它的直径有3476公里。如果月亮是一个披萨，我们可以把它切成3476公里那么大的好多好多片呢！

Let's do another fun comparison. If Earth were the size of a basketball, how big would the Moon be? About the size of a tennis ball! The Moon is much, much smaller than Earth. Specifically, if you cut the Moon into little pieces, it would take 79 Moons to fill up the volume of Earth. 79 Moons stacked together equal just one Earth! That number sounds pretty amazing, right? Though the Moon is much smaller than Earth, it's still really, really big to us. At night, the Moon looks about the size of a dinner plate, but actually, its diameter is 3,476 kilometers. If the Moon were a pizza, we could cut it into so many slices that each slice would be 3,476 kilometers big!

地球的直径是多少呢？大约12742公里。12742公里！如果你坐飞机从地球的最这边飞到最那边，需要飞多久呢？大约需要14个小时！飞机飞14个小时才能穿过地球，而月亮只需要用脚走242年就能跨过去——当然，这只是一个很有趣的比较啦。

What's Earth's diameter? About 12,742 kilometers. 12,742 kilometers! If you took a plane and flew from one side of Earth to the other, how long would that take? About 14 hours! A plane needs 14 hours to fly across Earth, while the Moon... well, it would take 242 years to walk across - though that's just a fun comparison!

月亮还有一个特别有趣的地方，那就是它总是用同一面朝着我们。什么意思呢？想象一下，如果有一个朋友，你绕着他转圈圈，但始终让他看到你的正脸。不管你转到左边还是右边，右边还是后面，你的脸总是对着他。月亮就是这样！月亮绕着地球转，但它总是把同一面朝向地球。所以，我们人类在地球上永远看不到月亮的背面。这是为什么呢？

Here's something really interesting about the Moon - it always shows us the same face. What does that mean? Imagine you have a friend, and you walk around them in a circle, but you always keep your face pointing toward them. Whether you go left, right, or behind, your face is always facing them. That's exactly what the Moon does! The Moon orbits around Earth, but it always keeps the same side facing Earth. So people on Earth can never see the far side of the Moon. Why is that?

这是因为月亮绕地球转一圈的时间和它自己转一圈的时间刚好一样长！月亮绕地球转一圈需要大约27.3天，它自己转一圈也需要大约27.3天。就像你在玩一个有趣的游戏：你一边转圈，一边绕着你的朋友转，而且转得刚刚好，每次你的正脸都对着你的朋友。

This is because the time it takes for the Moon to orbit Earth is exactly the same as the time it takes the Moon to rotate once on its axis! The Moon takes about 27.3 days to orbit Earth, and it also takes about 27.3 days to rotate once. It's like you're playing a fun game: you spin around while walking around your friend, and you spin at just the right speed so your face is always toward your friend.

这个有趣的现象叫做"潮汐锁定"。潮汐就是大海的涨潮和退潮。月亮用它的引力（就是那种看不见的、拉东西的力量）拉着地球上的海洋，让海水一会儿涨上来，一会儿退下去。而且，因为月亮总是用同一面对着地球，所以月亮背面发生的事情，我们完全不知道呢。直到1959年，苏联的宇宙飞船第一次飞到月亮背面，人类才第一次看到月亮背面长什么样子。

This interesting phenomenon is called "tidal locking." Tides are the rising and falling of the ocean. The Moon uses its gravity - that invisible force that pulls things - to pull on Earth's oceans, making the seawater rise and fall. And because the Moon always keeps the same side facing Earth, we have no idea what's happening on the Moon's far side. It wasn't until 1959 that a Soviet spacecraft flew to the far side of the Moon for the first time, and humans finally saw what the back of the Moon looked like.

月亮背面是什么样子呢？那里有很多很多大大小小的坑，叫做"环形山"或者"撞击坑"。这些坑是几百万年甚至几十亿年前，宇宙里飞来飞去的石头撞到月亮上留下的。月亮没有空气，没有水，也没有风，所以这些坑一直保存在那里，从来不会被"磨平"。而在地球上，风吹雨打会让高山变矮、大石头变小。但月亮上永远是安安静静的，那些古老的撞击坑就像时间的档案馆，记录着很久很久以前宇宙里的故事。

What does the far side of the Moon look like? There are lots and lots of big and small holes there, called "craters." These craters were made millions or even billions of years ago when rocks flying around in space crashed into the Moon. The Moon has no air, no water, and no wind, so these holes have been preserved there forever, never getting "worn down." But on Earth, wind and rain can make mountains shorter and big rocks smaller. The Moon is always quiet and still, and those ancient craters are like a time archive, recording stories from the cosmos long, long ago.

说完了月亮的大小和距离，让我们再来看看月亮为什么有时候是圆圆的，有时候是弯弯的，有时候甚至看不见。这就要说到月亮和太阳玩"捉迷藏"的游戏了！

Now that we've talked about the Moon's size and distance, let's look at why sometimes the Moon is round, sometimes it's a crescent, and sometimes we can't see it at all. This is where the Moon and Sun play their "hide and seek" game!

太阳、月亮和地球，这三个好朋友每天都在玩追逐游戏。地球待在原地不动，绕着太阳妈妈转圈圈，同时，月亮又绕着地球转圈圈。当月亮转到太阳和地球中间的时候，如果它们三个刚好排成一条直线，月亮就会把太阳光挡住——这就是"日食"。日食的时候，大白天会变得黑黑的，就像突然到了晚上一样。

The Sun, Moon, and Earth - these three good friends play a chasing game every day. Earth stays in one place, orbiting around the Sun, while the Moon orbits around Earth. When the Moon moves between the Sun and Earth, if they line up in a straight line, the Moon blocks the sunlight - this is called a "solar eclipse." During a solar eclipse, daytime suddenly becomes dark, like night has come early.

当地球转到太阳和月亮中间的时候，地球的影子落在月亮上，月亮就会变得暗暗的，这就是"月食"。月食的时候，我们能看到月亮慢慢变暗，好像被什么东西遮住了一样。这两种"食"都是因为太阳、月亮和地球在玩排队游戏呢！

When Earth moves between the Sun and Moon, Earth's shadow falls on the Moon, and the Moon becomes dark - this is called a "lunar eclipse." During a lunar eclipse, we can watch the Moon slowly darken, as if something is covering it. Both types of "eclipses" happen because the Sun, Moon, and Earth are playing a lining-up game!

但是呀，太阳和月亮的"捉迷藏"游戏可不只是发生日食和月食的时候。我们每天晚上看到的月亮形状都不一样，这才是真正的"捉迷藏"呢！月亮有时候圆圆的，像一个大大的白色披萨；有时候弯弯的，像一把银