Our reconstruction of the chronology of events that led to the origin of the Earth and subsequent chemical evolution on our planet informs us that nothing unusual was required for the origin and development of terrestrial life, and that therefore life may be pervasive throughout the cosmos....

Gravity is the most important force in the universe, holding together planetary systems, stars, and galaxies. It is what makes the stars hot enough to shine and what keeps the Earth close enough to the Sun for life to form. It is also what ends the life of every massive star with a spectacular...

One of the greatest achievements of twentieth-century science is an understanding of the origin of matter. While hydrogen and helium were produced in the Big Bang, the origin of the heavier elements—the silicon in rocks, the iron in our blood, and the oxygen we breathe--lies in the lifecycle of...