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.