Please Explain: The Moon

We can see the moon is up there in the sky most nights, but how much do we really know about it? Dr. Juliane Gross, a research scientist in the American Museum of Natural History's Department of Earth and Planetary Sciences, tells us all about the moon--how it got there, why it orbits the earth, and what a blue moon—the kind of full moon we had on Tuesday—is.

The moon model is on display in the Dorothy and Lewis B. Cullman Hall of the Universe at the Museum of Natural History.
The moon model is on display in the Dorothy and Lewis B. Cullman Hall of the Universe at the Museum of Natural History. ( Credit: AMNH/D. Finnin )
One of four moon rocks on display at the American Museum of Natural History, collected by astronauts during the Apollo lunar missions in the 1970s.
One of four moon rocks on display at the American Museum of Natural History, collected by astronauts during the Apollo lunar missions in the 1970s. ( Credit: AMNH/D. Finnin )
of