If there's one thing I love more than octopuses, octopodes and octopi (all of which are perfectly acceptable pluralizations of the word octopus, thank you very much), it's pedantry. And good grief, does Phil Plait ever serve up a whopping helping of the stuff in reaction to today's Earth-Day themed Google Doodle.
Plait (aka the "Bad Astronomer"), kicks off his long list of scientific grievances thusly, today on Slate:
The phase of the Moon is shown the wrong way.
As the Doodle cycles, you see the Moon rising on the left and setting on the right (which is correct for someone in the northern hemisphere facing south; east is to the left and west to the right). The first time we see the Moon, it’s a crescent rising in the east at sunset, oriented with the wide part to the left, and the horns of the crescent pointing to the right.
But that’s not possible. When the Moon is opposite the Sun in the sky, it has to be full. Here’s why.
The reason we see phases of the Moon is due to the geometry between the Earth, Moon, and Sun, which changes as the Moon orbits the Earth. When the Sun and Moon are in the same part of the sky, the Moon is new. A few days later, as the Moon circles the Earth, it pulls away from the Sun in the sky, and we see a crescent, with only part of it lit. A few days more (a week after new Moon), and the Moon is half-lit (what we call, weirdly, first quarter, because it’s a quarter of the way through its monthly cycle). A few more days, and the Moon gets fatter, and has what’s called a gibbous shape. Then, two weeks after new Moon, it’s opposite the Sun in the sky and we see it as full, a completely lit disk.
After that, the cycle reverse. The Moon becomes gibbous, then half lit, then a crescent again. Since it’s at the end of its cycle, we call that the old Moon.
Google's doodle begins with the old Moon, but there really isn't anything wrong with that (after all, the Moon's phases follow a cycle, so there really isn't a correct "beginning" or "end" to its illumination); what is wrong, says Plait, is that the crescent Moon be near the Sun in the sky. "That’s why it’s a crescent," Plait insists. In the doodle, "it’s shown as opposite the Sun, rising in the east as the Sun sets in the west, which only happens when the Moon is full."
This oversight will not stand, man. And if Plait has anything to say about it, neither will the several other scientific mistakes in this otherwise characteristically fun, entertaining and interactive Google doodle. Seriously, though, it's loaded with inaccuracies. Head on over to Slate for Plait's full unmitigated pedantry-fest.