This photo from 1902 shows French knife grinders. They would work on their stomachs in order to save their backs from being hunched all day.
They were also encouraged to bring their dogs to work to keep them company and also act as mini heaters by having them rest on their owners’ legs.
They were also called ventres jaunes (“yellow bellies” in English) because of the yellow dust that would be released from the grinding wheel.
The behavior of a steel ball bouncing on a hardened steel anvil demonstrates the exponential decay of the motion and the corresponding increase of the frequency of the bounces.
An avalanche at the Tibetan Plateau
With an average elevation of 4500 metres above sea level, the Qinghai-Tibet Plateau is one of Earth's highest points with mountains such as Mount Everest and K2, often referred to as "the Roof of the World".
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