History of the Universe eBook. 398 pages, 300 illustrations only $2.99
When Robert Brown observed the rapid random motion of pollen grains and other small particles floating on liquids in 1827, using the newly invented microscope, he was unable to explain why they moved. It was Albert Einstein who finally proved mathematically that this motion is caused by the motion of the molecules of the liquid. The energy for this motion is the heat which the liquid contains.
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