“Those wanderers must have looked on Earth, circling safely in the narrow zone between fire and ice, and must have guessed that it was the favourite of the Sun's children.”

“The time was fast approaching when Earth, like all mothers, must say farewell to her children.”

“If such a thing had happened once, it must surely have happened many times in this galaxy of a hundred billion suns.”

“A man who grows that much hair,' critics were fond of saying, 'must have a lot to hide.”

“In this single galaxy of ours there are eighty-seven thousand million suns. [...] In challenging it, you would be like ants attempting to label and classify all the grains of sand in all the deserts of the world. [...] It is a bitter thought, but you must face it. The planets you may one day possess. But the stars are not for man.”

“It must be wonderful to be seventeen, and to know everything.”

“My favourite definition of an intellectual: 'Someone who has been educated beyond his/her intelligence.[Sources and Acknowledgements: Chapter 19]”