Of all the events in the 20th century that would have been "absurd" by the standards of the 19th century, not a single one - to the best of our knowledge - violated the law of conservation of energy, which was known in 1850.

::nitpick:: Nuclear reactions violate the 1850s version of the law of conservation of energy. We get around that today by redefining mass as a kind of energy via Einstein's famous equation E=mc^2.

Transmutation of chemical elements? Absurd! ::end nitpick::