听力文摘：气球不见之后发生了什么?（在线收听）

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，嘉年华，节日聚会还有任何其他地方你都能买到氢气球，你至少能看到一个气球由于有人没有拿好，意外让气球飞向高空的情况。

What happens to the balloon after it rises out of sight? Well,that depends on how high the balloon goes!气球飞到看不见的地方会发生什么呢？嗯，这取决于气球飞到多高的地方！

When you inflate a balloon, you’re actually putting gases, mostly helium,in this case , into an elastic container. As you add more gas, the pressure inside the balloon increases, and in response, the balloon expands…up to a point, that is! If you put in too much helium, and the pressure inside the balloon gets too much higher than the atmospheric pressure on the outside of the balloon, the balloon will burst.

当你给气球充气的时候，你充的一定是气体，大多是氢气，到一个有弹性的容器内。你加入的气体越多，气球内部的压力也随之增长，相应地，气球变大了……到了一定的大小，就是那个状态下，如果你充入更多的氢气，气球内部的压力就比气球外面的大气中的压力大，气球就会保障。

So what happens to a rising balloon? 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! 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.

所以一个不断向上升的气球会怎么样呢？嗯，如果它遇到气流被带到地球表面，这样可以走很远。如果有风，它甚至可以越过海洋！当然，不论怎么扎紧气球，没有气球是完全不会漏气的。因此最终氢气会泄露，气球会下沉。