The July 31 appearance of the month’s second full moon will be seen for the first time in America since August of 2012.

Blue Moon To Come On Friday

Every month has a full moon, but because the lunar cycle and the calendar year aren’t lined up correctly, every three years there are two full moons in the same calendar month.

However, our Earth’s moon will not turn up blue.

When a moon does take on a bluish hue, it is due to the smoke or dust particles in the atmosphere, such as during a volcanic eruption.

The Indonesian volcano Krakatoa eruption of 1883, unleashed too much ash into the atmosphere, and caused the moon to glow in a blue light for many years.

After the explosion, which scientists measured to be similar to a nuclear bomb, the volcanic debris caused vibrant red sunsets and the moon to have a blue hue.

According to NASA’s National Space Science Data Center, the dark blue coloring of a sky can affect the coloring we perceive. The phrase “once in a blue moon” was created because it stood for something so rare, you’d be lucky to ever see it.

The U.S. Naval Observatory in Washington explained that when a season has four full moons, the third one is called a blue moon.

This blue moon event will not be seen again until January 2018.

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