I’ve always known that the Kuiper belt and Oort Cloud are the outermost part of the Solar System, but I never had a sense of scale between the two. Kuiper belt objects, including Pluto and other dwarf planets, orbit at ~55 AU (0.001 light years). Compare to the Oort Cloud, a 50,000 AU (~1 light year) sphere containing billions of comets at the boundary of the Solar System’s gravitation.
We have hardly begun to explore the outer Solar System and Kuiper Belt, and have searched next to nothing of the Oort Cloud–analogous to only inspecting your garden box in a 100 acre plot of land. If extraterrestrials are observing us from the Oort Cloud, we have absolutely zero chance of knowing they’re here.
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May 9, 2009 at 3:14 pm
Paul Maurice Martin
I really hope they’re out there. I used to ask “Is there intelligent life elsewhere in the universe?”
After the performance of our species on this planet over the past few decades, I’m now more inclined to simply ask, “Is there intelligent life in the universe?”