GRAND RAPIDS, Mich. (WOOD) — Sometimes when the sun or moon is low in the sky, it seems to grow by several sizes. One viewer wants to know why this happens from time to time in this week’s Ask Ellen.

It’s true the sun or moon can look larger depending on where it is in the sky. This goes for whether you are taking a picture, or just spotting it with your naked eye.

For years, it was theorized that the change in optical size was due to the fact that the image of the sun or moon was traveling through a thicker part of the atmosphere at sunrise or sunset, and it would “change” the size by our perspective on earth. While this is a great theory (and the reason we see oranges and reds at sunset, by the way), it is not the reason the sun or moon looks bigger at times.

Picture courtesy Walter E. Elliott

The reason comes down to a plain old optical illusion. Here is a great example. Take a look a these two orange dots. Which one is bigger?

Optical illusion showing two orange dots

At first glance, our brain tricks us into thinking the right is larger. When you remove the surrounding gray circles the orange dots are revealed to be the same size.

Optical Illusion removing the surrounding objects.

The sun or moon appears to be bigger in the sky when surrounding objects change their appearance! When the sun or moon are lower on the horizon, smaller buildings, hills, mountains, or trees can make each appear big. Even small clouds in the distance can have this effect.

A fun experiment to do with the moon is to use a paper towel roll cardboard tube and hold it up facing the moon while it is low on the horizon. Use one eye to look through the tube at the moon while closing the other. The moon alone will look small.

If you shut the eye looking down the tube and open the one without, it will look bigger! While you could do this same experiment during the day with the sun, it is not advised as it could cause eye damage.

Bottom line? Perspective is everything.