Sunday, June 19, 2016

Depths of Time in a Starry Night Image

Image Credit: Brad Goldpaint
The APOD today is beautiful! The above image, taken by Brad Goldpaint, shows a starry night scene over the Ancient Bristlecone Pine Forest in California, U.S.A. 

The trees in the image are themselves quite old, dating back several thousands of years, with one tree named Methuselah dated to 4,847 years old and another tree (not yet named) dating back to 5,065 years in age (these trees are considered to be the oldest known living non-clonal organisms). Some of those bristlecone pines stood long before Galileo turned his telescopes to the heavens; those trees bathed in starlight generations before Eratosthenes of Cyrene calculated the circumference of the Earth and developed a science of chronology; and some of those trees opened their branches to the world before people started laying the stones that would become the Great Pyramid of Egypt.

Goldpaint's night scene also shows the planets Saturn and Mars, of which the curators of APOD remark are "seemingly attached to tree branches, but actually much farther in the distance... These planets formed along with the Earth and the early Solar System much earlier -- about 4.5 billion years ago." In my recent talk, "This Thing is Older Than Your Mom" (which I gave for the 3rd Season finale of Famelab USA), I spoke of the oldest solid materials to have formed in our solar system. The calcium-aluminum-rich inclusions (CAIs) and chondrules that can be found in some of the most primitive meteorites are materials that formed before the planets as we know them. Those materials and others in primitive meteorites have given us insight into the earliest processes in our solar system, including the timing of the formation of our planets. That's how we can say that Saturn and Mars are over 4.5 billion years in age. The lives of the bristlecone pines would seem just a short blink of time relative to the ages of Saturn, Mars, the Earth, and our solar system. 

However, the oldest of the old, the most ancient of the ancient and venerated of the venerable, in this beautiful image are the stars stippling the night's sky and the band of white of our Milky Way Galaxy. At best, a single person may be able to see 2000 or so stars at night, yet we can see the illumination of our sky in a milky white band due to the illumination from hundreds of thousands of millions of other stars in our galaxy (most shining from somewhere near the plane of the galaxy). Some of those stars may be much younger than our own Sun and planets, while most of them are quite older. Sadly, a recent report in Science Advances estimates that at least 80% of the world's population lives under light polluted skies, so that as much as one third of the global human population can no longer see the Milky Way at night (we are truly stealing our history from our children by taking away the night's sky). While we should take a moment of pause and reflection at the fact that most people cannot observe the Milky Way, at least we can look on images like Goldpaint's picture at the top of this post and consider the depths of time that have passed on our planet, in our Solar System, and in the Milky Way Galaxy that surrounds us. 

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