Jazz music, by its nature, has to be heard to be understood and appreciated. In an earlier time, it might have remained a regional or ethnic niche music for some time, but thanks to the phonograph, one musician or band could teach jazz to millions.

Jazz has its roots in a number of other musical forms: band music, spirituals, blues, and ragtime.

After years of warlord infighting, some of the major factions were exhausted, while striking workers agitated for reform. It was time for the United Front to make its move, but the untimely death of Sun Yat-sen complicated the picture.

Warren Harding was very much a hands-off kind of leader. This worked well when he appointed capable cabinet secretaries, especially Secretary of State Charles Evans Hughes. Meanwhile, America experiences the Tulsa Massacre, the worst single episode of racial violence in its history.

Gandhi returned to India during the Great War, but needed some time to reacquaint himself with the country after being away for so long. The British promise more self-rule, but the ruthless killing of hundreds of peaceful, unarmed civilians in Amritsar is for many Indians the last straw.

Mohandas Gandhi went to South Africa to represent an Indian business in a legal dispute. He stayed for 23 years, practicing law, advocating for equal rights for Indians, and developing his theory of resistance, which he called satyagraha.

By the beginning of the twentieth century, astronomers had some idea of the size and shape of our galaxy, though the consensus was that the galaxy represented the entirety of the Universe. But in the decades that followed, it became clear that the Universe was much more.

By the beginning of the twentieth century, the younger generation of nationalists had become impatient with its elders' polite political agitation and sought ways to increase the pressure on the British to grant Indians more autonomy.

Britain's control over India was not the main reason the UK rose to become the superpower of the 19th century, but the wealth extracted from India preserved British supremacy for decades longer than otherwise would have been possible, but at a terrible cost to the Indians.

In 1858, the British government took direct control over India. This was supposed to cure the injustices of Company administration, but life in India grew worse, not better.