Fairs, carnivals, festivals or anywhere you can buy helium-filled balloons, you’re sure to see at least one balloon rising into the sky after someone accidentally lets it go off.
在集市，狂欢节，节庆日，或是在任何可以买到氦气球的地方，你肯定能至少一次看到过一只气球在人们不小心松手时，飞向天空。
What happens to the balloon after it rises out of sight? well,that depends on how high the balloon goes!
气球上升到肉眼看不到的高空时会发生什么事呢？这个呢，就得看看气球升到哪个高度了！
When you inflate a balloon, you’re actually putting gases, mostly helium,in this case , into an elastic container.
当你让气球膨胀时，实际上是把气体，多数情况是氦气充到一个橡胶容器里。
As you add more gas, the pressure inside the balloon increases, and in response, the balloon expandsup to a point…
充气越多，气球内的压力也就越大。相应的，当气球膨胀到某一点时......
that is! If you put in too much helium, and the pressure inside the balloon gets too much higher thanthe atmospheric pressure on the outside of the balloon, the balloon will burst.
答对了！如果气球内的氢气太多，多到气球内的气压超过外部的大气压，气球就会爆炸。
So what happens to a rising balloon?
那么升到高空的气球会发生什么事呢？
Well, if it gets caught by an air current and is carried along level to the earth’s surface, it could go a long way,even across the ocean,if the winds arrived!
如果气球搭上了气流这个顺风车并沿着地球表面平移，它就会飘很长一段路，甚至能穿越海洋！
Of course, no balloon is perfectly sealed, no matter how tightly you tie it, so eventually the helium will leak out, and the balloon will sink.
当然，没有哪个气球是完全不会漏气的，无论扎的多紧，球内的氦气都会漏光，气球就掉了下来。
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