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If you ever look up at the moon at night sky, say, before you go to bed,
如果你曾经仰望夜空看月亮，比如，在你上床之前这样做，
you've probably noticed that, as the days and weeks go by, the moon looks like it's changing shape.
就可能注意到，随着日子一天天过去，月亮看起来一直在改变形状。
Some nights, it's a little sliver.
某些晚上，它就是一小片。
And some nights, a few weeks later, it's a big bright circle!
几周后的一些夜晚，它就是一个明亮的大圆！
Well, the moon doesn't actually change shape.
但事实上，月亮没有改变形状。
But our view of it does. Why?
而是我们视野中的它在变化。为什么会这样呢？
Well, the moon, just like the Earth, has a day side and a night side,
月球和地球一样，有光面和背阴面。
a part that's facing the sun, and a part that's not.
即一部分向阳，一部分不向阳。
So when we see a little sliver of bright moon,
所以当我们看到一小片明亮的月亮时，
we're seeing a little part of the moon that's facing the sun, while the rest of the side that's facing us, is dark.
我们看到的是月球向阳的一小部分，而其他面向我们的部分是暗的。
And the size and shape of that little sliver of lit-up moon changes, because the moon orbits, or moves around Earth.
而这一小片照亮的月球因为围绕地球旋转，它的大小和形状也发生了变化。
It takes the moon about one month to make a one full orbit around the Earth.
月球绕地球一周大约需要一个月的时间。
And as it moves around our planet, the day-time side of the moon, the side that's lit up from the sun,
当它围绕地球旋转时，它的阳面即被太阳照射的一面，
is facing in different directions, as we see it from Earth.
正面向不同的方向，正如我们从地球上看到的那样。
This means that, every night we get a slightly different view of the moon!
这就意味着我们每晚看月球的角度会有细微的变化！
And during its month-long trip in orbit around the Earth,
在月球围绕地球旋转长达一个月的周期中，
the bright part of the moon appears to grow, and then shrink, from right to left!
月球的光面似乎在生长，然后收缩，都是从右到左！
The different shapes that we see of the lit-up part of the moon, are called phases.
我们看到的月球光面的不同形状，叫做月相。
And there are eight phases of the moon.
月相分八个阶段。
The first phase is the new moon.
第一个阶段是新月。
This is when the nighttime side of the moon, the side that's facing away from the sun, is what we can see from Earth.
这是月球的背阴面，即月球远离太阳的一面被我们从地球上看到。
The moon is still up there!
月球仍在那里！
But because its dark side is facing us, we can't see it during the new moon phase!
但因为它的背阴面面向我们，所以我们在新月时期看不到它！
The next phase is called the crescent phase.
下一阶段叫做峨眉月阶段。
This is when the moon looks like a little sliver, kind of like the tip of your fingernail!
这一阶段的月亮看起来是一个小片儿，有点儿像你的指尖！
After the crescent comes the quarter moon, this when the moon looks like half-circle!
峨眉月之后是上弦月，这时期的月亮像半圆！
The next phase is called gibbous.
下一阶段是渐盈凸月。
A gibbous moon is when it's missing just a little sliver of light, and it's almost full!
渐盈凸月阶段是它仅仅失去了一点儿光，差不多圆满了！
And that's what's next! The moon is at its brightest at the full moon.
接下来是什么？月亮最亮的满月期。
That's when the fully-lit side of the moon is facing us, so we see a big, bright circle.
这时月球的光面面向我们，所以我们看到了一个大而明亮的圆。
But we're only halfway through our phases!
但这只是月相的一半！
After the full moon, the lit-up part of the moon appears to shrink.
满月之后，月球的光面开始缩减。
And just like how it grew from right to left, the sunny side of the moon will shrink from right to left too!
就像月球的阳面从右向左变多一样，它也从右向左开始缩减。
So, after the moon is full, it starts to shrink back down to a gibbous moon.
所以，满月之后，它开始缩减至渐亏凸月。
But this time, you'll notice that the left side is shining bright instead of the right!
但这时，你会注意到是月球的左边闪闪发亮，而不是右边。
And after the gibbous phase, the moon will look like half circle, when it reaches the quarter moon phase again.
月亮在渐亏凸月时期之后再次到达弦月阶段，它看起来像半圆。
And then after a few days, it shrinks down to a little sliver again...the second crescent moon.
几天后，它又开始缩减至一小片，第二次的峨眉月阶段。
After that, the tiny sliver shrinks all the way down until the lit-up side of the moon can't be seen at all.
此后，小片一直缩减，直到月球的光面完全看不到为止。
Now, the moon is a new moon again. It's the same old moon!
现在，月亮又是新月了。同旧时月一样！
But it's gone through a month-long cycle of phases, and is ready to start all over.
但它经历了长达一个月的周期，准备好从头开始了。
Like I said, it takes a month for the moon to go through all eight phases.
正如我所说，它经历八个阶段需要一个月。
In fact, our word "month" comes from the word "moon",
事实上，单词“month”就是从“moon”上衍生出来的，
because it takes a month for the moon to go from new moon, through all of its phases, and back to new moon again.
因为月球从新月经历整个过程再次回到新月阶段需要一个月的时间。
So, tonight, before you go to bed, take a look out the window.
所以，今晚上床前，看看窗外。
If the sky is clear, can you see the moon?
如果天气晴朗的话，你能看到月亮吗？
If you can, what phase is it?
如果能，它是什么阶段呢？
Is the bright part on the right side or the left side?
它的阳面是右边还是左边？
As the days go by, keep an eye on it and watch how the moon looks like it's changing shape.
随着时间的流逝，密切关注月球变化形状的样子。
You can even make drawings to keep track of how it changes from day to day.
你甚至可以一天天地画画，追踪它的变化。
Now you know that the moon doesn't really change shape.
现在你知道月球不会改变形状了。
We just see different amounts of the sunny side of the moon, as it makes its monthly trip around the Earth.
随着它围绕地球的周期变化，我们看到的只是月球光面的多少而已。
Thanks for joining us today!
感谢您的收看！
We love getting questions here at the Fort!
我们喜欢在沃斯堡收到问题！
So if you have one...ask a grownup to help you leave a comment down below,
所以你有问题的话，找个大人帮忙在下方留言，
or send us an email to kids@SciShow.com!
或发邮件至kids@SciShow.com！
Thank! We'll see you next time!
感谢您收看！我们下期见！
