Today’s topic was “moon phases,” the vocabulary and geometry behind why the moon appears to change size each month. In reality, there is nothing changing about the moon; it is always the same size, orbiting roughly the same distance from Earth, receiving the same amount of sunlight. What we call “moon phases” is really a change in how we view the moon, not a change to the moon itself.

As you can see in the video above, when the moon is directly behind Earth, we are able to see all of it’s illuminated side. This called a full moon. After that, the moon enters the waning gibbous phase, shrinking each day as it goes. Then comes the waning quarter, followed by the waning crescent, and eventually a new moon. After that, the moon begins waxing, or growing, each night. It starts out as a waxing crescent, then a waxing quarter, eventually becomes a waxing gibbous, and then becomes a full moon again. This process is repeated roughly once per month.

Thank you to those of you who visit the website religiously. As a reward for those of you reading this, I will give a prize to the first person who visits me during homeroom and whispers the password “eclipse.”

January 12 – Moon Phases (pg407)