Ann Druyan, Cosmos television series This is the book for everyone who has never understood why astronauts returning from Mars would discover that they're 20 years younger than when they set out. That the speed of light is absolute makes it a tad tricky, but Einstein sorted it and so will you when you've listened to this. --The Guardian (audiobook review)
(The authors have) blazed a clear trail into forbidding territory, from the mathematical structure of space-time all the way to atom bombs, astrophysics and the origin of mass. --The New Scientist
A thrilling experience of passionate comprehension. --Ann Druyan, Cosmos television series
"The authors do a great job of answering the question in the book's title, and of tying it to the cutting edge of 21st century physics. But they do much more besides. First, they give a real sense of revelation as the
equation emerges from the seemingly unrelated concepts of space and time. Second, they're not afraid to take on questions often asked about the equation."