If a set of scales is arranged so that one scale is kept dark, and Light is allowed to fall on the other, the lighted scale will sink slowly.
Light has "weight". The pressure of light on the Earth's surface is calculated as two pounds per square mile.
如果将一架精确的天平一头放在黑暗中，另一头让光照到，照到光的那一头会慢慢往下沉。
光有“重量”。据计算，光对地球表面的压力为每平方英里2磅。
- 2平方英里约为5.18平方公里，2磅约为0.91千克。换算成我们熟悉的单位，就是光对地球表面的压力为每平方公里0.17千克。
图片来自网络
Perfectly still water can be lowered to temperatures several degrees lower than the freezing print and remain liquid.
绝对静止的水，温度可以降到冰点以下好几度而仍然保持液态不结冰。
The hardness of ice is similar to that of concrete.
冰的硬度和混凝土相仿。
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