Solstice Moon Illusion

Do you want to see a giant moon? Step outside after sunset Wednesday night and look to the horizon on the east. You will see a huge moon rising into the sky.

Solstice Moon | Manchester, MD

The full Moon of June 18th is a “solstice moon”, coming only two days before the beginning of northern summer. This is significant because the sun and full Moon are like kids on a see-saw; when one is high, the other is low. This week’s high solstice sun gives us a low, horizon-hugging Moon and a strong Moon Illusion.

Sky watchers have known for thousands of years that low-hanging moons look unnaturally big. At first, astronomers thought the atmosphere must be magnifying the Moon near the horizon, but cameras showed that is not the case. Moons on film are the same size regardless of elevation … Apparently, only human beings see giant moons.

Are we crazy?

After all these years, scientists still aren’t sure. When you look at the Moon, rays of moonlight converge and form an image about 0.15 mm wide on the retina in the back of your eye. High moons and low moons make the same sized spot, yet the brain insists one is bigger than the other.

To learn more about the Solstice Moon Illusion, visit the Science & Nasa page.

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  1. Ray Fowler says:

    So did anybody get to see this last night? We drove out to a big hill facing east and tried, but it was too cloudy here to see anything. Maybe we’ll try again tonight. It’s not the full moon tonight, but it should still be pretty big!

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