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Los Altos Library

13 S. San Antonio Road
Los Altos, CA 94022

Monday10am - 9pm
Tuesday10am - 9pm
Wednesday10am - 9pm
Thursday10am - 9pm
Friday10am - 6pm
Saturday10am - 6pm
Sundaynoon - 6pm
Holidays & Closures

Phone:(650) 948-7683

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Once in a Blue Moon

If you’re looking for something to happen “once in a blue moon,” look for it this Friday. This actually not so rare event occurs when two full moons appear during one calendar month. Because the previous full moon occurred on August 1st, the full moon appearing on August 31st is called a “blue” moon. And while that is how we define a blue moon now, originally a blue moon occurred when there were four full moons during a single season. Does the moon actually appear blue? Well, no. As long ago as the 16th century, the expression “the moon is blue” meant something that was impossible. However, the moon can appear greenish or bluish just before sunrise or just after sunset, if there is enough dust in the atmosphere.

To learn more fun facts about the moon, check out the Los Altos Library’s outstanding science collection. This part of our collection is funded in large part by the Los Altos Library Endowment.


The Book of the Moon The Book of the Moon


Moon Moon


Return to the Moon Return to the Moon