Astrophysicst Stephen Hawking

Portrait of a young Stephen Hawking, May 17, 1963. (Howard Grey)

Stephen Hawking visits the London Science Museum’s exhibit on his life and work. (Sarah Lee)

Some of the Hawking memorabilia on display at London’s Science Museum exhibition marking the scientist’s 70th birthday. (Science Museum PA)

The model built for Hawking in the early 1970s to show the deep gravitational “well” that black holes create in the fabric of space-time, from which not even light can escape. (Whipple Museum of the History of Science)

These two globular star clusters, located beyond our Milky Way galaxy, harbor hundreds of thousands of stars. Deep within the clusters’ dense cores, stars whirl rapidly around intermediate-sized black holes. (NASA/Hubble)

Seorang militan pro-Rusia di posisi pertahanan terdepan dengan senjata mesin di kota Slovyansk (19/5). (Reuters/Yannis Behrakis)

The smallest known black hole – part of a binary star system named XTE J1650-500 – is about 3.8 times more massive than our Sun. (NASA/CXC/A. Hobar)

This cosmic beach ball displays a full-sky map of the microwave radiation left over from the Big Bang event that created the universe 13.7 billion years ago. (NASA)

A sketch from Hawking’s notes illustrates the phenomenon of black hole radiation by showing that quantum effects cause electromagnetic particles to fleetingly form just outside the hole. (Hawking Family Archive)

Stephen Hawking’s A Brief History of Time, published in 1988, has been an international best seller, with over 10 million copies in print. (Science Museum PA)

Stephen Hawking, almost totally paralyzed since 1970 by ALS, enjoys a few moments of weightlessness during a flight aboard Zero Gravity Corp.’s modified Boeing 727. (Jim Campbell, Aero-News Network)

Stephen Hawking lecturing on the future of space exploration at a 2008 George Washington University event marking NASA’s 50th anniversary. (NASA/Paul E. Alers)

President Barack Obama talks with Stephen Hawking in the Blue Room of the White House before a ceremony presenting him and 15 others the Presidential Medal of Freedom, August 12, 2009. The Medal of Freedom is the nation's highest civilian honor. (Officia