I have always believed the moon appears bigger when on the horizon than when it is overhead because of light refraction. When looking at it on the horizon we are looking through much more atmosphere therefore it appears to be very large. I was wrong. When the diameter of the moon is measured at the horizon and overhead the measurement is the same. So what is going on? It is our brain. Our brain concludes when it is near the horizon it is very far away and therefore has to be huge and when overhead our brain perceives it as being closer and it need not be as big.
Now please before you think I am either crazy or really stupid this is not my idea. This is the accepted theory of the world’s leading astronomers and cognitive theorists. It is an example of the old expression, “My brain is playing tricks on me.” It is comparable to not remembering why you entered a room until you return to where you were when you started the errand. It is a blow to our pride to think our own brain deceives us. We want to believe our powers of logic are a certain guide to truth. When we see something, we “know” it is true. But is it? At the beginning of my courses I inform my students half of what I will teach them isn’t true. My problem is I don’t know which half.
Thus the need for faith. “Faith is being sure of what we hope for and certain of what we do not see.” Hebrews 11:1
Written by Roger Bothwell on August 17, 2003
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