【英语时差8,16】糖罐子里的秘密(下)(在线收听

Now put a spoon in and smooth the surface of the sugar: all those evenly-spaced crystals will be packed down into an uneven arrangement, filling the empty spaces. The result is still a 60 – 40 ratio, only now we have a lower level of sugar, with the empty space moved up top. It’s the same with soil. Rainwater and passing feet press the soil down so that the grains lie closely together with little empty space, called “pore space.” When the shovel pulls the soil up and scatters it in a big pile, the soil grains fall into a pattern closer to the way they were before being packed down. Once the hole is refilled, all you have to do to make it level is get rid of that pore space — which can easily be done with the back of a shovel.
 
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