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One of the best parts of our day here at the Fort is checking our email.
我们在沃斯堡中的最好时光就是查看电子邮件。
We get so many awesome science questions!
我们收到很多很棒的科学问题！
Even though we can't answer them all,
即使我们不能全部回答，
today Squeaks and I wanted to answer a few!
但今天我和吱吱想回答几个！
Okay, our first question come from Kelsey.
我们的第一个问题来自凯尔西。
Kelsey wants to know, "Why is it harder to run uphill and easier to run downhill?"
凯尔西想知道“为什么下山容易上山难呢？”
Interesting question, Kelsey!
有趣的问题，凯尔西！
It's easier to run down a hill than up a hill because of gravity,
下山比上山更容易是因为重力，
which is a force that pulls you, and everything else on the planet toward the ground.
重力是把你和地球上的其他所有物体都拉向地面的力。
Forces are the pushes and pulls that happen to us and all around us every day.
我们身上或周围每天都有拉力和推力。
When you push a block along the floor or roll a ball, you're putting a force on it!
当你沿着地板推一个障碍物或者滚一个球时，你在给它施加一个力！
Gravity is a force, too, and it's pulling on us all the time, even though we can't see it.
重力也是一种力，它一直推着我们，即使我们看不到。
But we sure can feel what gravity does!
但我们确实能感觉到重力的作用！
Like, when I jump into the air …like that ...
比如，我向空中一跳，就像这样...
I don't stay up for very long because gravity pulls me right back down to the ground.
我不会停留很长时间，因为重力立刻把我拉回到地面。
The reason I was able to be in the air for even a little bit is because of another force:
我之所以能在空中停留一会儿是因为另一种力：
the push I made against the floor with my legs.
腿向下踩地板产生的推力。
I pushed down with my legs hard enough to overcome gravity, but only for a second.
我用腿使劲往下推，以此克服重力，但只能停留一秒。
Now, if I push down harder, I can jump higher...But it takes more work.
现在，如果我往下推得越用力，就可以跳得更高……但它需要更多努力。
The same kind of thing happens when we run up a hill.
爬山也一样。
Our legs are trying to push our bodies up, while gravity is pulling us down.
我们的腿试图把身体推高，但重力往下拉我们。
We have to work hard to fight the pull of gravity, and more work means we get tired faster!
我们必须努力对抗重力，付出更多努力意味着我们疲惫得更快！
The opposite happens when we run down the hill.
下山时情况相反。
This time, we get a little help from gravity,
这时，我们获得了重力的一点儿帮助，
since gravity is pulling us down, the same direction that we want to go.
因为重力往下拉我们，与我们走得方向相同。
We're not fighting against the gravity, so it doesn't feel like we're working as hard.
我们不再对抗重力，所以不必那么努力。
Thanks for your question, Kelsey!
凯尔西，感谢你的提问！
Our second question is from Matty.
第二个问题来自马蒂。
Matty asked us, "How can insects climb walls and be upside down?"
马蒂问我们：“昆虫怎么能爬上墙且能上下颠倒呢?”
That's an awesome question!
这是一个很棒的问题！
If I tried to climb a wall, gravity would pull me right back down!
如果我试着爬墙，重力会把我拉下来！
So how do flies and other insects do it?
那么苍蝇和其他昆虫是怎么做的呢？
Gravity pulls on everything, even the tiniest fly!
重力拉一切物体，甚至小苍蝇！
Well, some insects have special body parts that help them to climb up walls and across ceilings.
有些昆虫有特殊的身体部位，帮助它们爬上墙壁、越过天花板。
Because a wall or ceiling that looks or even feels pretty smooth to us, really isn't.
因为墙壁或天花板看起来甚至感觉起来很平滑，但其实不是。
If we could look at a wall really closely, we'd see that they have lots of little bumps, cracks and pits.
如果我们能近距离观察一面墙，会发现它们有很多小凸起、裂缝和凹坑。
And what seems like a tiny bump to us can look like a comfortable place to stand for a tiny fly!
对我们来说是小凸起的东西似乎是小苍蝇站立的舒适区。
Some insects have little claws or hairs on the ends of their legs,
有些昆虫的腿末端有小爪子或毛，
which they use to help them grab onto the bumps in the wall or ceiling.
用来帮助它们抓住墙上或天花板上的凸起。
There are also some insects that make an oily liquid that helps them to stick to a wall or ceiling.
还有一些昆虫会制造一种油状液体，帮助它们粘在墙上或天花板上。
It's sticky enough to keep their bodies from falling down,
它的粘性足以支撑它们的身体掉不下来，
but not so sticky that they get stuck in one place!
但不至于让它们卡在一个地方!
Thanks for your awesome question, Matty!
谢谢你的问题，马蒂！
We love getting comments and mail!
我们喜欢收到评论和邮件！
So if you have a question for us, ask a grown-up to help you leave a comment below,
如果你有问题，找个大人帮忙在下方留言，
or to send us an email tokids@scishow.com!
或发邮件至kids@scishow.com！
We'll see you next time, here at the Fort!
我们下期见，沃斯堡等你哦！
