Sunday, November 02, 2008

A walk across the universe

You will know by now that my daily walk to college is about a mile. Several thousand steps. Through woods and meadows. Across a stream.

Imagine that the mile represents the distance to the most distant objects we see with our telescope, most of the way back to the big bang itself, 13.7 years ago. As I start my walk in the morning, the big bang is a mile away -- 13.7 billion light-years.

On this scale, the Milk Way Galaxy is about the size of a dime -- one hundred billion stars in a whirling spiral. The next spiral, the Andromeda Galaxy, is another dime (well, maybe a nickel) about as far away as my footprint is long. The Milky Way under my heel, Andromeda under my toe.

I take a step. I span galaxies. As I walk, galaxies flow under my feet. As I approach my destination, I begin to encounter quasars, the violently energetic centers of young galaxies, vast black holes in the making. In my last step, I encounter the creation of matter out of pure energy.

Fling dimes for a mile in every direction, a foot or so apart. Every dime is a galaxy of a hundred billion stars. Every star (perhaps) with planets.

As we look out with our telescopes, we see those other galaxies as they were at some time in the past. No galaxy is closer to the center. There is no center. Nor a boundary. The universe inflates like the surface of a balloon. Inflates from a pinpoint. Space (the surface of the balloon in my analogy) comes into existence as the balloon inflates. The galaxies are dots on the balloon. As the balloon inflates, the dots move apart. But no dot is central, and there is no boundary to the surface. The view from any galaxy is like the view from any other.

Now let the mile of my walk represent time, the 13.7 billion years that the universe as we know it has been in existence. The several million years of our human ancestry would fit into my footprint. All of recorded human history would snuggle under my little toe. My lifetime is the thickness of a slip of paper.

You've taken this walk before. Or something like it. You've seen the Hubble photographs. You've heard the analogies. But one can hear the story a hundred times and still it's hard to grasp the dimensions of cosmic space and time. I've been writing and teaching this sort of thing for half a lifetime, and I still have a hard time getting my head around it.

Surely, no discovery is of greater import. It is a discovery that should shake our ancient theological and philosophical assumptions to their core. But the fact remains that the vast majority of people -- even many who are highly educated -- continue to live psychologically in the cozy human-centered universe of Aquinas and Dante.

The Church knew what it was doing when it burned Giordano Bruno at the stake in 1600. Bruno was one of the first to imagine the plurality of worlds. All the stars were other world systems, he said. Space was infinite. This just decades after Copernicus had moved the Earth from the center of the cosmic egg, and only years before Galileo turned his telescope on the myriad stars of the Milky Way.

Bruno was a rebel from from his youth, and prone to enormous ego and outrageous opinions, but give him this: He dreamed of a universe not unlike the one we subsequently discovered, and he understood its implications. The individual, said Bruno, was a "temporary conglomeration of atoms in the great sea of the world's soul." A whole tablet of heresies followed -- questions about heaven, hell, the Incarnation, and personal immortality -- for which the dreamer paid the ultimate price.

Accept a universe of worlds without end and the power of the Church as divinely appointed broker of God's commerce with humans is threatened. Thus the fiery execution in the Campo de Fiori in Rome, the victim's heretical tongue restrained with a thong or spike so that he might notin extremis compound his blasphemies.

But the Church was not alone in being threatened by cosmic space and time. Each us us must feel a shudder of angst when looking into the abyss. We have been raised to believe a personal creator of the universe is mindful of our every thought and action. Yet everything we have discovered about the universe suggests that we are, as Bruno said, "temporary conglomerations of atoms in the great sea of the world's soul."

I set out on my daily walk. The sky in the east glows golden with the light of dawn. A long, ragged vee of geese honks overhead, heading south. At the plank bridge the water purls in cold eddies; soon we'll have the first thin films of morning ice. I stop, and listen. A nuthatch? A wind in the willows? I do my best to open my senses to the "world's soul." I stand on the bridge and I shiver in "the immense and the numberless" (to borrow the title of one of Bruno's books). Then I start again along the path, my stride encompassing galaxies.

Further Reading

A new biography of Bruno by Ingrid Rowland, Giordano Bruno.

Tom informs me that Google Street View now includes Rome. If you would like to visit the place were Bruno was executed, and see his statue, go to Google maps and type in "Campo de Fiori, Rome". Click on the northeast corner of the square (the intersection of the Via del Pellegrino and the Piazza della Cancelleria) and turn around and walk into the Campo. As you zoom in, you will see Bruno looming there.

Discuss this essay and more over on the Science Musings Blog.