Worlds Without End

A cosmic snapshot tests the limits of comprehension

| Utne Reader September / October 2007

We live on Earth. Earth is a clump of iron and magnesium and nickel, smeared with a thin layer of organic matter, and sleeved in vapor. It whirls along in a nearly circular orbit around a minor star we call the sun.

I know, the sun doesn't seem minor. The sun puts the energy in our salads, milkshakes, hamburgers, gas tanks, and oceans. It literally makes the world go round. And it's huge: Earth is a chickpea and the sun is a beach ball. The sun comprises 99.9 percent of all the mass in the solar system. Which means Earth, Mars, Jupiter, Saturn, etc., all fit into that little 0.1 percent.

But, truly, our sun is exceedingly minor. Almost incomprehensibly minor.

We call our galaxy the Milky Way. There are at least 100 billion stars in it, and our sun is one of those. If you had a bucket with a thousand marbles in it, you would need to procure 999,999 more of those buckets to get a billion marbles. Then you'd need to repeat the process a hundred times to get as many marbles as there are stars in our galaxy.

So. Earth is massive enough to hold all of our cities and oceans and creatures in the sway of its gravity. And the sun is massive enough to hold Earth in the sway of its gravity. But the sun itself is merely a mote in the sway of the gravity of the Milky Way, at the center of which is a vast, concentrated bar of stars, around which the sun swings (carrying along Earth, Mars, Jupiter, etc.) every 230 million years or so. Our sun isn't anywhere near the center; it's way out on one of the galaxy's minor arms. We live beyond the suburbs of the Milky Way. We live in Nowheresville.

But still, we are in the Milky Way. And the Milky Way is at least a major galaxy, right?