In our astrophysics class, a student
once asked, "Why are we here?" The answer was as amazing to us as
it was to the class:
We are here because, more than ten billion years ago, the universe borrowed energy from the vacuum to create vast amounts of matter and antimatter in nearly equal numbers. Most of it annihilated and filled the universe with photons. Less than one part per billion survived to form protons and neutrons, and then the hydrogen and helium that makes up most everything there is. Some of this hydrogen and helium collapsed to make the first generation of massive stars, which produced the first batch of heavy elements in their central nuclear fires. These stars exploded and enriched the interstellar clouds that would form the next generation of stars. Finally, about five billion years ago, one particular cloud in one partcular galaxy collapsed to form our Sun and its planetary system. Life arose on the third planet, based on the hydrogen, carbon, nitrogen, oxygen, and other elements found in the protostellar cloud. The development of life transformed Earth's atmosphere and allowed small furry mammals to take center stage. Primative men and women evolved and moved out of Africa to conquer the world with their new knowledge of tools, language, and agriculture. After raising food on the land, your ancestors, your parents, and then you consumed this food and breathed the air. Your own body is a collection of the atoms that were created billions of years earlier in the interior of stars, the fraction of a fraction of a percent of normal matter that escaped annihilation in the first microsecond of the universe. Your life and everything in the world around you is intimately tied to countless aspects of modern astrophysics.