2 things science and human progress accomplished on this date.
1747
The first controlled clinical trial begins
Ship's surgeon James Lind divided scurvy-stricken sailors into groups and gave some of them oranges and lemons, proving citrus was the cure. His experiment founded the modern science of clinical trials.
Seventeen nations signed the Metre Convention in Paris, creating a shared international standard for the metre and the kilogram. It gave science and trade a common language of measurement that most of the world still uses.