Sir Terry Pratchett (1948-2015) was an English author of fantasy novels, especially comical works, best known for his extensive Discworld series. He was the UK's best-selling author during the 1990s and from 1983 to 2015, he averaged about two books per year. Pratchett was knighted for his services to literature in 2009 and received the World Fantasy Award for Life Achievement in 2010. In 2007, he announced he had been diagnosed with early-onset Alzheimer's, the disease that would eventually take his life in March 2015.

Pratchett was beloved not just for his prolific works of fiction, but also for the imaginative spirit he inspired in others. Imagination was key to Pratchett's personal philosophy, as evidenced by the quotation below:

"Imagination, not intelligence, made us human."

Below, science-fiction writer Catherine Asaro explains how hard science fiction based on theoretical physics can also spur the imagination. After all, it takes one heck of an imagination to understand theoretical physics:

Photo: Silverlutra~commonswiki / CC BY-SA 3.0