What Good is Stardust?
The universe is remarkable for what God has equipped it to do
Howard J. Van Till | posted 8/06/2001 12:00AM
Several years ago, my family and I drove from Tucson to Los Angeles on a clear and moonless summer night. There were few cars on the road that night, few headlights to ruin my night vision. Some hours into the ride, I noticed a diffuse band of light in the sky. Eager to get a better look at it, I stopped the car and turned off the headlights. Now I could see the luminous patchwork far more clearly, stretching across the sky from one point on the horizon to its opposite.
I immediately recognized what I was looking at, but it was no less wondrous just because I could name it. I had seen the Milky Way often, of course, but never under such ideal viewing conditions as on this dark night in the desert, far from the light pollution of any city. From this viewing site, the glow from the countless stars and nebulae of our home galaxy was not merely something that one could see, with a bit of effort. No, it was the first thing one noticed when looking up—the most prominent attraction in the star-studded sky.
Astronomers have learned a great deal about our Milky Way Galaxy, especially during the last century. Hundreds of billions of stars, sprinkled with thousands of star clusters and glowing gaseous clouds, are arrayed in pinwheel fashion throughout a more or less flat disk. Its dimensions are difficult for our minds to grasp. The diameter of the galactic disk is 100,000 light-years. That is, it would take light—travelling at its characteristic speed of 186,000 miles per second—100,000 years to travel from one edge of the disk to the opposite edge. Our solar system (the sun and its entourage of planets and lesser objects in orbit around it) is located about 30,000 light-years from the center, in the suburbs of the Milky Way. The band of light that I viewed from the darkened desert is what the Galaxy looks like from the inside.
But the Milky Way is merely one of many such astronomical giants. Only a handful of the others are within range of unaided human vision. Most galaxies can be seen only with the additional light-gathering power of a telescope. The central and brightest region of the galaxy M-31—one of our nearest neighbors, "only" 2 million light-years distant—can sometimes be seen without the aid of a telescope as a fuzzy patch of light in the region of sky occupied by the stellar constellation Andromeda.
With the largest of telescopes, astronomers can see hundreds of billions of galaxies, out to distances up to 15 billion light-years. They are distributed in a rather irregular, almost spongelike fashion, with some regions (corresponding to the hollow portions of the sponge) nearly devoid of galactic occupants. And this distribution is itself actively changing, the major alteration being a steady growth in the mean distance between neighboring galaxies or clusters of galaxies.
To our amazement, this growth is not the consequence of galaxies moving through space to new locations. No, the increase in distance is caused by the expansion of space itself. Space, we have learned, is not merely a nothing into which things can be placed. Contrary to our common conception of it, space is a nonmaterial something that can act and be acted on. Its action of expanding is one of the fundamental story lines in the formational history of the universe. From its big-bang beginning—about 15 billion years ago—the size of the universe has been growing. This spatial expansion is what leads the distance between galaxies to increase. Space itself is expanding, and galaxies are going along for the ride.
August 6 2001, Vol. 45, No. 10
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