In fact, this was accepted as the most accurate measurement of the speed of light for the next forty years, at which point Michelson measured it again. The next lecture is on the Michelson-Morley experiment to detect the aether.
The United States declared war on Germany on April 6, 1917. There was two major reasons. First off, the German U-Boats sank 3 passenger ships carrying US civilians and citizens.
By adhering to the pledges, Germany averted war with the United States in 1915 and 1916. In January 1917, however, Germany decided to resume unconditional submarine warfare, fully aware that renewed surprise attacks on merchant and passenger ships would likely prompt the United States to declare war.