"Thomas Paine's Common Sense first appeared on January 10, 1776, and the stroke of luck it enjoyed upon its appearance could hardly have been calculated to great effect. The political tract immediately became the moral and intellectual touchstone for American colonists struggling to articulate their case for independence from England. It sold over 120,000 copies within three months of its publication. the United States of America owes its existence...

This book belongs to the most rare of men. Perhaps not one of them is yet alive. It is possible that they may be among those who understand my "Zarathustra": how could I confound myself with those who are now sprouting ears?--First the day after tomorrow must come for me. Some men are born posthumously. The conditions under which any one understands me, and necessarily understands me--I know them only too well. Even to endure my seriousness, my passion,...

De Brevitate Vitae (English: On the Shortness of Life) is a moral essay written by Seneca the Younger, a Roman Stoic philosopher, sometime around the year 49 AD, to his father-in-law Paulinus. The essay argues that time is best used by living in the present moment in pursuit of the intentional, purposeful life.

Explains how scientists' observations of the stars led to the development of the big bang theory, a theory of how our universe was formed.

For hundreds of years, people found the fossils of ancient sea creatures at the tops of tall mountains. Scientists puzzled over this problem. A fish couldn't have swum up a mountain. And how could rocks on a mountain move up from the bottom of a sea? Geologists finally found the answers they needed in the 1960s, when they developed the theory of plate tectonics. This theory revolutionized our understanding of the earth. Plate tectonics explains how...