SO MANY SUNS, SO MANY WORLDS

We live in an expanding Universe, vast and ancient beyond ordinary human understanding. The galaxies in contains are rushing away from one another, the remnants of an immense explosion, the Big Bang. Some scientists think the Universe may be one of a vast number-perhaps an infinite number-of other closed-off universes.

There may be different laws of Nature and different forms of matter in those other universes. In many of them life may be impossible, as there are no suns and planets, or even no chemical elements more complicated than hydrogen and helium. Others may have an intricacy, diversity, and richness that dwarfs our own.

Our Universe is composed of some hundred billion galaxies, one of which is the Milky Way. "Our Galaxy", we like to call it, although we certainly don't have possession of it. It's composed of gas and dust and about 400 billion suns. One of them is the Sun, our ordinary local star. Accompanying the Sun in its 250 million year journey around the center of the Milky Way is a retinue of small worlds. Some are planets, some are moons, some a asteroids, some comets. We humans are one of the 50 billion species that have lived on a small planet, third from the Sun, that we call the Earth.