"A long time" is not an acceptable answer to a scientifically minded 10-year-old. Overlooking the Grand Canyon, my father explained how it was made by the Colorado river eroding a plateau.
"How long did it take?" I asked.
"A long time," was his unsatisfactory reply. I decided to test it by leaving our hose running in a corner of the yard. It turns out that it takes longer for a Grand Canyon to form than it does for the neighbors to complain about their garden flooding.&n
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