A preview of an upcoming post.

When you have salt or some other granular substance, you will notice that as you tilt the container, the surface must get to a certain angle before everything suddenly slips and levels out at another angle. If you continue tipping, you see the same thing happen again and again. Moreover, that angle is held constant within the material. It does dependencies on certain physical characteristics such as humidity and coarseness, but so long as these things are held invariant, the angles can be relied upon.

This is called the angle of repose.

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