A Weblog Dedicated to the Discussion of the Christian Faith and 21st Century Life

A Weblog Dedicated to the Discussion of the Christian Faith and 21st Century Life
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I do not seek to understand that I may believe, but I believe in order to understand. For this also I believe, –that unless I believed, I should not understand.-- St. Anselm of Canterbury (1033-1109)

Thursday, October 22, 2015

Is Life In the Universe Special Because It Is Rare?

For centuries, we human beings have speculated on the possible existence and prevalence of life elsewhere in the universe. For the first time in history, we can begin to answer that profound question. At this point, the results of the Kepler mission can be extrapolated to suggest that something like 10 percent of all stars have a habitable planet in orbit. That fraction is large. With 100 billion stars just in our galaxy alone, and so many other galaxies out there, it is highly probable that there are many, many other solar systems with life. From this perspective, life in the cosmos is common.

However, there's another, grander perspective from which life in the cosmos is rare. That perspective considers all forms of matter, both animate and inanimate. Even if all "habitable" planets (as determined by Kepler) do indeed harbor life, the fraction of all material in the universe in living form is fantastically small. Assuming that the fraction of planet Earth in living form, called the biosphere, is typical of other life-sustaining planets, I have estimated that the fraction of all matter in the universe in living form is roughly one-billionth of one-billionth. Here's a way to visualize such a tiny fraction. If the Gobi Desert represents all of the matter flung across the cosmos, living matter is a single grain of sand on that desert. How should we think about this extreme rarity of life?
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The entire post can be read here.

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