Thursday, March 02, 2000

Solar Dance 5: The Galactic Landscape

(Image Credit: Wolfgang Brandner (JPL/IPAC), Eva K. Grebel (Univ. Washington), You-Hua Chu (Univ. Illinois Urbana-Champaign), and NASA. This image shows several stages in the life cycle of stars in a single image; to be taken to the Hubble page with caption:

At the heart of the bigger picture of the cosmos that I am trying to know is the idea of expanding my sense of place. Like many humans, I have a pretty solid sense of the region where I live. I know its communities of plants and animals, the forms of its land, the direction from one place to another. My skywatching is but a few steps removed from, and intimately related to, this common experience.

A slightly larger sense of place includes the knowledge that over those mountains on the horizon lies Chaco Canyon, or that following these nearby mountains north will bring me to Yellowstone, and then the Canadian Rockies. To have a general sense of where each direction is in the local landscape, and what lies further in that direction in the continental landscape, brings me home in a larger sense.

Beyond that is the Gaian view, of being a part of one living planet. I won’t go into the details, controversies, or distortions that surround this image of a living earth: questions of fore-planning by creation, self-organization at the root of material forms, the role of symbiosis in biology, or human-centric thinking. Beyond all these issues lies the experience of the unity of earthly life. Virtually all primal cultures, and various artistic, literary, and scientific traditions in modern cultures, have shared in this experience. In this view, nature is the most accessible, tangible window through which humanity can explore the mysteries of life and creation. To know the unity (and diversity) of life on earth is but one small step from entering the galactic landscape.

An earlier installment (The Solar Dance #2, The Living Solar System), introduced the experience of knowing our place as being a part of our local star’s body. This essay builds from there, as we begin to look out from our "spaceship earth", now rightly perceived as but an orbiting piece of the star that is us.

What is the lay of the land within which our star is living its life? Most of us know the simple answer: we are part of a spiral galaxy we call The Milky Way. The general picture of a disc of stars, dense in the center, with a number of spiraling arms is familiar to any schoolchild. We’ve further been told that we are on the edge of one of the outer arms, offering a healthy sense of the peripheral role of the sun in the grand scheme of the galaxy. Perhaps we have also integrated the knowledge that the Milky Way we see stretching across the summer sky is a view through the disc of the galaxy. This is a great starting point for gaining a true sense of place in the galactic landscape.

So here we are, under the night sky, the Milky Way stretching overhead. If it is summer, the band is wide and bright, stretching up from its heart near the tail of Scorpio. If it is winter, the Milky Way is fainter, but still obvious under dark skies, passing alongside Orion, and fading out up toward Cassiopeia’s "w" shape. We know that’s the galaxy, but we have little or no idea how all the stars we see, or our sun, fits into the whole.

To flesh out our knowledge of the galactic landscape will be the goal of many of our skywatching sessions. A few key landmarks will begin to give flesh to the body of the galaxy, allowing us to begin to experience the next step of knowing our place. We’ll learn which way the galaxy is spinning, which stars are just ahead of us in this great spiral dance, what’s "up" and "down" in a familiar sense, when we’re looking into the galaxy’s center and when we’re gazing out the nearby edge. Future posts will highlight these perspectives, but it's worth mentioning the basics up front:. The summer Milky Way is a primary anchor for this awareness: with the thick heart of the galaxy lying low in the south, the white band stretching overhead is "ahead" of us in the grand turning of the galactic disc, with bright Vega leading our way around that center). Meanwhile, the winter sparkle of Orion and Sirius points us toward the softer band of the spiral arm that swings around outside and behind us, trailing the sun in its great journey as part of the galaxy's turning. Buckle up, and prepare for liftoff!


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