Written by Meteorologist Dave Aguilera

We have a full moon coming up on Monday, Sept. 12. This will be this years Harvest Moon! Astronomers call the full moon nearest the Autumnal Equinox,  the “Harvest Moon.” This year the Equinox will be on Sept. 23 at 3:05 am.

Sometimes the Harvest Moon appears to be bigger as it rises at the horizon and soon after that it does when it is straight up in the sky. Scientists call this the “moon illusion”.

The moon illusion can make the moon look much larger at one position than it does at the other, even though the size is always the same.

One theory as to how this occurs is that when the moon is close to the horizon our minds eye has something to compare its relative size to, like the ground, trees, houses etc. This fools your brain into perceiving the moon to be larger than it actually is.

The other theory, is the proximity to the horizon gives your brain something to compare distance to. But, when the moon is directly overhead there is nothing for you brain to compare distance to, so the overhead moon looks smaller.

Either way the harvest moon is a beautiful sight this time of year.

The moon gets its name because the added full moon light allowed farmer’s to spend more time getting the harvest in late in the day.

LINK: howstuffworks.com/question491.htm

  1. name says:

    Please also note that the moon’s orbit is an ellipse and the moon actually appears larger when closest to the earth (“perigee”) and smaller when furthest (“apogee”). This is not an illusion.

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