Astronomer William Keel of the University of Alabama uncovered an interesting fact about the Earth's view of the universe around it. Perhaps this isn't one that you'd run across, but when I did, I found it rather mind-boggling. Was it only by a stroke of luck that we were ever in a position to realize that such a thing as the Milky Way galaxy exists?

Keel and two University of Chicago astronomers observed distant galaxies from an angle that put their sightline through the spiral arms of closer galaxies.

They found that only 15-20% of the light from the more distant galaxies penetrated. ( Ray White III and William C. Keel, "Direct Measurement of the Optical Depth in a Spiral Galaxy," Nature, 359 (1992), pp. 129-130, and Ray White III, William C. Keel, and Christopher Conselice, Astrophysical Journal, 1996 (in press).

Most light from distant galaxies, it turns out, is actually absorbed by dust in the nearer galaxies. This carries an amazing implication as to our own solar system's location between, not in, the spiral arms of the Milky Way.

According to Keel, if we had been located in one of the spiral arms, we -- wait for it -- may never have seen other galaxies at all, and may never have discovered that we reside in a galaxy. A blind man can't visualize yellow or red.

I'm trying to imagine an Earth in which we were not able to see through a fog of space, and were not aware of the movements of extra-galactic objects, and in which we had no concept of the size (much less age) of the universe. How many things would we believe differently than we now do?

The Earth has what can be considered a window seat to the majesty of the entire universe. We have an unobstructed view of the ultimate art form.

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By the way, another benefit to the fact that we live between the Milky Way's spiral arms consist of the fact that intense radiation from supergiant stars within the spiral arms would overwhelm our atmospheric protection from the effects of such supergiants.

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One of my favorite Hubble discoveries, and in my opinion one of its most practical ones, occurred in 2004. That year, the Hubble was focused for 278 hours on a relatively tiny sector of the sky equivalent to only one-tenth the diameter of the full Moon. ( Peter Bond, "Hubble’s Long View," Astronomy & Geophysics, vol. 45, no. 3 (June 2004): 328.)

This allowed astronomers to calculate the constraints on all the galaxies that COULD possibly exist in any given segment of the sky - even the faintest ones that formed earliest.

About 10,000 galaxies were imaged in that segment of the sky. If this density is typical -- and it is hard to imagine how it could fail to be -- and the number were projected to the entire sky, then the number of likely galaxies in the universe would resolve at around 200,000,000,000.

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In 2006, Alice Quillen calculated and predicted the existence of a planet, orbiting around the nearby star Formalhaut. She is an expert the dust rings orbiting stars, and inferred from the

This planet was imaged by the Hubble Space Telescope, making it the second planet (after Neptune) to be correctly inferred and then imaged.

Quillen "saw the way the inner edge of the dust ring cut off sharply and recognized that a planet likely orbited just inside," said Eugene Chiang, part of the team that imaged the planet. She surmised that a small planet was using its gravity to throw the dust in its area out of orbit. Her projected orbit for the plant "was amazingly close" to the actual orbit observed.

Yesterday, I calculated that ARCO's $0.45 ATM charge made it more expensive for me than the gas station next door that charged two cents more a gallon. Good week for both of us.

Cheers,

jemanji

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images:

http://imgsrc.hubblesite.org/hu/db/2007/41/images/a/formats/web.jpg

http://www.spacedaily.com/images/fomalhaut-extrasolar-planet-bg.jpg