The original version of this story appeared in Quanta Magazine.
In 1848, when Louis Pasteur was a young chemist still years away from discovering how to sterilize milk, he discovered something peculiar about crystals that accidentally formed when an industrial chemist boiled wine for too long. Half of the crystals were recognizably tartaric acid, an industrially useful salt that grew naturally on the walls of wine barrels. The other crystals had exactly the same shape and symmetry, but one face was oriented in the opposite direction.
The difference was so stark that Pasteur could separate the crystals under a magnifying lens with tweezers. “They are in relation to each other what