Although Twilight fans may not care, our heroine Bella Swan’s knowledge of lunar phases is questionable. In the book’s title-inspiring scene, in which her vampire boyfriend Edward leaves her and she wanders through the woods for hours, Bella thinks, “Tonight the sky was utterly black. Perhaps there was no moon tonight—a lunar eclipse, a new moon.”
Bella correctly equates “new moon” with “no moon.” A new moon is above the horizon only during the day, and the only lit part is the far side that we can’t see.
But Bella’s phrasing suggests a few astronomical impossibilities:
1) In her distress, is Bella thinking a lunar eclipse and new moon are the same? Her thoughts are ambiguous. But a lunar eclipse can happen only when the moon’s phase is full. Never when it’s new. Not even in fictional worlds with vampires.
When the moon is new, it’s between the sun and Earth, as Meyer describes on her Web site. A lunar eclipse, however, requires a different geometric line-up: Sun-Earth-Moon.
Only in this configuration can the Earth’s shadow cover (eclipse) the moon. MrEclipse.com explains why lunar eclipses don’t happen every full moon, and NASA’s lunar eclipse page lists dates of past and future lunar eclipses.
2) Even during a lunar eclipse, Bella wouldn’t have “no moon tonight.” The moon remains visible when eclipsed by the Earth’s shadow. Although the moon darkens, sometimes almost to the point of invisibility, it won’t completely disappear because Earth’s atmosphere bends sunlight. An eclipsed moon usually looks reddish (not to be confused with the reddish tint the moon can take on when near the horizon, regardless of its phase).
3) Even with no moon, the sky wouldn’t look “utterly black” in Forks, Washington, where Bella wanders the woods, unless there was a regional power outage. Because of light pollution, there are no truly dark skies in the entire state. But we can forgive Bella for exaggerating in her distraught condition.
Six months later (warning! spoiler ahead!), things brighten up for Bella when she reunites with Edward in Italy. There they further mangle the solar system by experiencing an impossible sun. That’ll be another blog post.
Do you have an example to share of impossible astronomy in a book? Please post a comment.
Amy Sayle is Morehead's Science 360 manager. She doesn't let impossible astronomy get in the way of enjoying a good story.