What it shows:
When sand in a balloon, just as atoms in a lattice, are close packed, they occupy the least possible volume. Any deformation, even compression, deforms this close-packed arrangement causing an increase in volume.
How it works:
The balloon is filled with sand, and black ink added allowed to percolate down and fill the air gaps. A capillary tube sticking out of the balloon indicates the ink level. When the balloon is squeezed the sand, which had settled down to a closely packed arrangement, is dislocated. Larger gaps...
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