Friday, November 16, 2007

Take a break and get some perspective!

Click on the title to this post to visit the image gallery. Besides an image of the day, they offer an archive, and interesting links to other image galleries on related themes, and even other branches of NASA. They even offer a library of the favorite and most famous images, that's searchable in a number of ways. A pretty sophisticated search function at GRIN (Great Images In NASA) -- doncha love government acronyms!?

Or you can use your X-ray vision by stopping that the Chandra site, I finally chose a beautiful image from Chandra, combining x-ray and other images to clarify mysterious extra "arms" on the spiral galaxy NGC 4258 (M106), which seem to be sheets of gas being superheated by shockwaves as twin jets spray out from near the disk of the galaxy. There are two spiralling arms that can be seen in visible light, but these two extra arms appear in x-ray ranges.

When we look at this image, we are looking both far away and long ago, about 25 million light years away, the young stars in the visible arms must be very different. When the light and x-rays that made these images left the constellation Canes Venatici (the two dogs that hunt Ursa Major, the Great Bear), what was happening on our little planet? According to the Wikipedia Timeline of Evolution, blue-green algae had been making oxygen for about 300 million years, making the air toxic to the anerobic microbes that had been happily burbling about until then. The anerobes retreated deep beneath the ocean and into rocks beneath the ground where the poisonous oxygen could not reach them. The oxygen, poisonous to the majority of life on earth then, actually created an opportunity for new microbes to evolve that could use the large amounts of oxygen now available. Hooray! Eukaryotes began the long, slow evolution into all manner of animals, plants, fungi and protists.

When you take the long view, almost any catastrophe starts to look a little better.

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