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.