2 things science and human progress accomplished on this date.
1849
Ivan Pavlov is born
Ivan Pavlov, the Russian physiologist who discovered classical conditioning, was born in Ryazan. He showed that a dog could learn to link a sound with food and then salivate at the signal alone. His work opened the scientific study of how animals and people learn.
When a Soviet warning system reported American missiles inbound, duty officer Stanislav Petrov judged it a false alarm and refused to pass the alert up the chain. He was right: sunlight glinting off high clouds had fooled the satellites. His calm may have spared the world a nuclear catastrophe.