When it rains after a prolonged period of dry weather, there is a smell created. It's called Petrichor. A wonderful word, and utterly useless trivia item. The smell is caused by something call Geosmin, which is produced by bacteria in the soil. Humans can smell it at 5 parts per TRILLION. In contrast Sharks can detect blood at concentrations of 1 part per million. On this one substance, we have a better sense of smell than sharks do for blood. Humans are amazing!

@quixoticgeek
How important it must have been to our survival as a species, that we are so sensitive to it!

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