Although 270.4 deg. C is 518.72 deg. F, -270.4 deg. C is NOT -518.72 deg. F. That temperature does not exist! Instead, -270.4 deg. C is -454.72 deg. F. I'm sure Dr. Hawking knew better, so I think it was someone else who made this egregious error, probably because they were too rushed to publish the book. I still give the book 5 stars.