时差N小时:为什么冰不滑

Try telling someone who has just fallen on a patch ofice that ice is not slippery and they'll think you'recrazy. But, in fact, ice itself isn't slippery because itis a solid. One quality of solids is that when twosolids are together there is friction between themthat will keep them from slipping.

告诉某个刚在冰上滑倒的人冰其实不滑，那人肯定会觉得你疯了。不过事实的确如此，冰本身并不滑，因为它是固体。固体的一个特点就是当两个固体接触时会产生摩擦防止打滑。

So how can your shoe slip on ice? The answer lies in two peculiar properties of ice. The first isthat as water freezes, its molecules move farther apart. The molecules of most substancesmove closer together as they freeze, making them shrink at lower temperatures.

因此，为什么你的鞋子会在冰上打滑?原因在于冰具有两种特性。第一种特性就是水结冰时，水分子分离得更远。但多数物质在结冰时，分子会紧密聚集在一起，温度一降低物质就会收缩。

But water molecules move farther apart at temperatures below 39 degrees Fahrenheit, makingwater expand as it freezes. That is why frozen water pipes burst, and a tray of ice cubes willfreeze over its top if you fill it too full. The second peculiar property of ice is directly linked toits first peculiarity.

但当温度低于39摄氏度时，水分子会分散开来，因此结冰后冰的体积大于水的体积。这就是为什么水管会冻裂，用盘子盛满水，结冰后冰面会超过容器的平面。冰的第二种特性与第一种特性是直接相关的。

When subjected to pressure, ice melts. Remember that the molecules in ice are farther apartthan the molecules in water; therefore ice molecules are vulnerable to pressure whichpushes them closer together, causing the ice to change into water.

冰在压力作用下会融化。记住冰的分子比在水的状态时更分散，受压后导致分子聚集，此时冰会变成水。

So when you step on a patch of ice, you exert pressure on the ice, which causes itsmolecules to move closer together. That makes them revert to their more dense state, whichis water. If you slip on a patch of ice, then, you in fact are slipping on a thin layer of waterthat the pressure from your weight has created. And, unlike solid ice, water, as a liquid , isquite slippery.

所以，当你踏在一块冰上时，会对它产生压力，这个压力导致分子相互间靠得更近，使之恢复到更加紧密的形态——水。如果你在冰面上打滑了，实际上是你在一层薄薄的水面上打滑了，而这些水正是因为你体重带来的压力导致的。跟固态的冰不一样，液态的水是相当滑的。