“Super-eruption of mount Toba, 76,000 years ago had wiped out a previous great civilization on earth.”

“After once having made the mistake of watching television news, I had worried for a while about an asteroid hitting the earth and wiping out human civilization. The anchorwoman had said it was not merely possible but probable. At the end of the report, she smiled.”

“I do not believe that civilization will be wiped out in a war fought with the atomic bomb. Perhaps two-thirds of the people of the Earth might be killed, but enough men capable of thinking, and enough books, would be left to start again, and civilization could be restored.”

“500 years ago Man "knew" the Earth was the center of the Universe. 500 years ago Man "knew" the Earth was flat. Imagine what you'll know tomorrow.”

“Global warming, along with the cutting and burning of forests and other critical habitats, is causing the loss of living species at a level comparable to the extinction event that wiped out the dinosaurs 65 million years ago. That event was believed to have been caused by a giant asteroid. This time it is not an asteroid colliding with the Earth and wreaking havoc: it is us.”

“A thousand years ago, everybody knew the Earth was the center of the universe. Five hundred years ago, they knew the Earth was flat. Fifteen minutes ago, you knew we humans were alone on it. Imagine what you'll know tomorrow.”