PacSci Perspectives

Once in a Blue Moon? No, once in a Black Moon? No, wait, what?

by | Sep 30, 2016

Your news feeds are probably filled with stories about a Black Moon rising tonight. What is a Black Moon anyway? Well simply put it was decided (by whoever decides these things) to call the second New Moon in any given month a Black Moon, the same way the second Full Moon of a month is called a Blue Moon.

Since the Moon takes about 29 days to completely go through the phases it is possible to have two Full or Two New Moons in any month other than February. Since the last New Moon was on September 1 we get another New Moon on September 30.

New Moon Diagram

This Diagram shows the relative positions of the Moon and the Earth during a New Moon on September 30, 2016.

Full Moon Diagram

This Diagram shows the relative positions of the Moon and the Earth during a Full Moon on October 15, 2016.

But what is a New Moon anyway? The light from the Sun shines down on both the Earth and the Moon. When the light is shining on the side of the Moon that faces the Earth we see the entire hemisphere lit up and refer to this as a Full Moon. When the light from the Sun shines on the side of the Moon which faces away from Earth we can’t see the Moon at all.

You won’t be able to go out and see the Black Moon because you can’t see New Moons because they are up during the day. The Moon rose just before the Sun at 5:32 a.m. this morning in Seattle and will set tonight just after Sunset at 5:49 p.m.

For more information here is a good article about the subject:

http://www.space.com/34162-black-moon-guide.html

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