When the Moon Hits Your eye...

When asked to compare the moon when it is at the horizon and when it is in the sky, how would you explain the size difference? Would you say that the horizon moon is closer to the earth? This is the most common explanation of the moon’s “size difference.” I found a lot of the old theories interesting to read. For instance, a 1899 theory states that when your line of sight is parallel to the ground (like looking at the horizon moon); gravity has effect on your eye. This gravitational effect is supposed to “increase the distance between the lens and the retina,” causing the object to look bigger. Another interesting theory was the “angle of regard theory.” This one states that raising your eyes deceives your judgement. But this would mean that if you looked up in the sky to the overhead moon and saw it as one size, then lay on your back and looked at it, they would be different sizes. Keep in mind that these are definitely just theories but I find it interesting to see what scientists came up with. When I started reading this chapter, I thought that the horizon moon must look bigger due to an oval shaped orbit, making the moon closer. It may be hard to understand but this is an illusion of the mind. It is known as one of the most unexplainable, but fascinating illusions that our brains can create. Ingram, or whoever writes for Ingram, could not give a straight forward explanation of this illusion, but did give a few tricks to test it yourself. First, you can take a picture of the moon in each position and you’ll see that they are the same size, and second, hold an aspirin up to the moon on the horizon and then up to the moon over top and you'll see that the aspirin covers the exact amount of space that it did for the horizon moon. I find it fascinating that our brains can make such a distinct illusion. By distinct I mean, how does the horizon moon look almost twice the size as the “normal” moon? Not only does it just look a little bit bigger but it almost doubles in size. It gets me thinking, what else do we see differently than it actually is? What if half the things in nature are illusions that haven’t been discovered yet? The weird thing is that our brains vision is the hardest aspect to explain because every person sees something different yet we all think we share the same visions. For example, the contrast of red that I see can be a totally different shade of red that you see but we still call the colour a general “red.” This chapter really opened up my mind to the way each individual perceives different things, or in some or many cases...illusions.

The Moon Illusion is created by a conflict between the intuitive and rational parts of the brain. It can be depicted with an inverted Ponzo illusion as shown above. All four moons are the same size, yet on the left, the lower moon nearer to the horizon appears larger than the higher moon.