xkcd: Oort Cloud

xkcd: Oort Cloud.

Comet ISON survived its swing by the sun, at least somewhat.

Comet ISON and our lack of fear

800px-HubbleSite-C2012S1-20130410
Image credit: NASA, ESA, and Z. Levay (STScI)

Lots of people are excited about comet ISON and the spectacular show it will hopefully provide.  However, unlike most people throughout history, most of us do not regard it as an evil omen, an attack from an angry god, or fear it for any other reason.  There’s a reason this.  Science!

Aristotle thought that comets were atmospheric phenomena, related to meteors or other fiery objects.  As in so many other areas, Aristotle’s view predominated until the scientific revolution, when Tycho Brahe demonstrated that comets were objects farther out than the moon.  Edmond Halley showed that comets followed elliptical orbits around the sun, and Isaac Newton, as part of his theory on  universal gravitation, showed that comets were subject to it, just like the planets.  Today, we know that comets are actually “dirty snowballs” swinging in from the outer solar system, which the sun causes to heat up and release an atmosphere, which the solar wind streams out into a tail.

We know these things because of efforts of astronomers throughout the centuries.  So, this Thanksgiving, when you’re listing things to be thankful for, you might want to include science, particularly astronomy, for the lack of fear you’re feeling as this comet passes by.