LONDON, ENGLAND - JUNE 15: Astronomer Royal Martin Rees speaks at Professor Stephen Hawking's memorial service at Westminster Abbey on June 15, 2018 in London, England. The world renowned physicist and author of A Brief History of Time, died early in the morning of 14 March 2018, at the age of 76. Professor Hawking's ashes will be laid to rest close to Sir Isaac Newton and Charles Darwin in the nave of Westminster Abbey. (Photo by Ben Stansall - WPA Pool /Getty Images)