celebrity status is traceable to November 1919 as major news outlets such as The Times (of London) and The New York Times reported on the scientific breakthroughs. Einstein was at times uncomfortable with his celebrity status, as it compromised his privacy. However, he used his fame to advance social causes for which he had strong conviction, such as Zionism, nuclear disarmament, civil rights, and pacifism. Astronomer Fred Hoyle rose to prominence by 1950, especially in the United Kingdom. He hosted a series of radio broadcasts by the BBC entitled, "The Nature of the Universe". Hoyle was for a time among the most popular broadcasters in the United Kingdom, and the book version of his radio broadcast was a bestseller. In the latter part of the 20th century and early 21st century, cosmologist Stephen Hawking achieved celebrity status. This was initially through his research publications on black holes and other aspects of cosmology. In 1988, he published A Brief History of Time, which was a book that provided insight into cosmology for the general public. Hawking's celebrity status grew rapidly, and his involvement in popular culture was perpetuated through television and radio appearances, biographical books, and being the subject of a movie, The Theory of Everything. At times, Hawking suffered from public scrutiny of his private life. Lists of notable English language popularizers of science and of science communicators are available. The Sagan Effect Carl Sagan was an accomplished researcher in the field of planetary science by the time he published his 1977 book The Dragons of Eden, on the evolution of human intelligence, targeted for general, non-scientific audiences. With this book, Sagan earned the Pulitzer Prize and became famous. In 1980, Sagan hosted the television series Cosmos: A Personal Voyage, which cemented his status as a scientific celebrity. Time Magazine called Sagan "America's most effective salesman of science". He also received significant financial rewards for his books, television shows, and television appearances. However, Sagan was also a university professor at the time that he first achieved celebrity status. Influential academic peers perceived Sagan as a popularizer of science and not a serious scholar. He was denied academic tenure at Harvard University, although he later became a full professor at Cornell University, despite his significant achievements as an independent researcher. Science historian Michael Shermer termed this the "Sagan Effect", since this form of academic snobbery applies to some other scientific celebrities.