Tonight, do not miss the opportunity to see the big moon illusion

Tonight, if you look at the night sky, you will have the opportunity to see a "big" Moon - the result of a rare, powerful illusion.

When the full moon appears in the night, many people will mistakenly think it is unusually large when near the horizon. In fact, it's just an illusion. The moon, near the horizon, is not much bigger when it is above our heads.

This hallucination is especially recognizable at the time of the "low-moon", ie two days before the summer begins in the Northern Hemisphere.

The reason for this, according to NASA, lies in the moon's mechanism: The sun and the full moon are like two kids playing seesaw, when one is high, the other will be low. This week, the rising sun makes us see the moon lying low, big in the horizon, and this illusion is very strong, lasting for a long time.

The sky we "see" has a bowl shape, making the moon in the horizon look bigger than the moon on the top of the head, not really. On the chart, with the "real" sky , the moon in any position is the same. (Photo: NASA)

And this is the mechanism of that illusion: Your thinking always believes that everything in the horizon is farther away at the top, because you're used to seeing clouds only a few miles from the top of your head, but clouds in the horizon can be practically hundreds of miles away. So if we think that something (such a moon) is farther away, but in fact it is not, it will look bigger.

If you are in doubt, please try to verify it. Go out to the moon with a small object, such as a pencil eraser. Grab it by hand when the moon rises and compare the size of the moon with the eraser. Repeat the experiment 1 or 2 hours after the moon rises above the top of the head.