[Earth’s orbit (Courtesy NASA); J.R.R.Tolkien (Courtesy The Tolkien Society]
Given the weight of the stories burying your social media on January 3 this year (including “bombogenesis”), you might have missed two less sensational annual events. At 12:35 AM EST, the Earth passed closest to the sun in its orbit, a point called perihelion (“around sun”). The actual time of perihelion varies a little bit each year, occurring some time between January 2-4. As you can see from the above diagram, we are not that much closer to the sun in January than we are at the farthest point (around July 4-5), called aphelion (“from sun”). A common misconception is that it is the shape of the earth’s orbit that causes seasons – being closer causes summer and being farther away causes winter. This misconception is fed by diagrams in science textbooks that greatly exaggerate the shape of our orbit, drawing it as an elongated ellipse rather than the rather more circular shape it actually has. The seasons are instead caused by the 23.5 degree tilt of earth’s axis.
The second annual event that was widely publicized on my social media was the 126th birthday of author J.R.R. Tolkien (January 3, 1892 – September 2, 1973), best known for The Hobbit and The Lord of the Rings. Among Tolkien fans it is a tradition to raise a toast to Tolkien at 9 PM local time on January 3 and proclaim “The Professor!” You might be wondering why I have included Tolkien in an astronomy blog. What many readers of Tolkien’s works miss is that he has a plethora of (often fairly accurate) references to astronomy in his fantasy! From the moon runes of The Hobbit to the various references to the sun, moon, stars, eclipses and more in The Lord of the Rings and his grand mythology The Silmarillion, Tolkien’s use of astronomy in his fantasy reveals his impressive knowledge of the night sky. Tolkien certainly wasn’t the first or last fantasy writer to integrate the night sky into his fantasy world, but unlike his friend C.S. Lewis, Tolkien felt it important to get the astronomy “right.” In fact, when he considered revising his unfinished mythology in the last decades of his life, he toyed with completely revising it to avoid trying to describe a mythological creation of the sun and earth, and used the then-current hypotheses concerning the formation of the moon as his guide.
So as you can see, January 3, 2018 gave this astronomer two reasons to celebrate. January 4, on the other hand, is just giving me an astronomical amount of snow to shovel….