Have you ever taken a walk at night and seen the Moon with its full ambiance shining down upon us or with its crescent moon, if you're lucky, you can see the dark side of the Moon? You might have noticed that when the Moon is either rising or setting near Earth’s horizon, it appears to be larger and more orange; but once it traversers further into the sky, it has a yellow-white hue and is smaller. Why is this the case?
The Moon's orange-red colour has to do with its wavelengths, which travel through Earth’s medium. At Earth’s horizon, wavelengths have to travel a much further distance, and only the brave and victorious red and orange wavelengths can make it through while the other wavelengths are blocked. On top of this, dust and pollution can also be factors because, following a similar logic as before, only certain wavelengths can make it through the pollution.
Now that we have figured out the Moon’s colour appearance, why does the body appear bigger on Earth’s horizon? The sad truth I always hate to say is that we aren’t entirely sure. Postulations and ideas have been tested over the years but is still quite uncertain. Most theories center on how our brain tends to visualize objects we see around us according to their size and distance from us. One explanation says that if you see trees and mountains near the Moon then that automatically tells your brain that the Moon should be big as well because of its surroundings. However, astronauts orbiting Earth can also see this illusion and they don’t have any mountains or trees to act as sensors to your brains.
Some theorists, like Aristotle, have even gone on to say that the Earth’s atmosphere scatters light rays coming from the Moon causing it to look bigger. Physicists proved him wrong and claimed that only the Moon’s colour has to do with the scattering of wavelengths.
One of the more recent tests was carried out with an MRI where scientists discovered that the brain has two parts that play a role in this illusion: the ventral and dorsal stream. The ventral stream is hypothesized to see the Moon as being far away so it’ll rescale it to make it seem larger. Then your dorsal stream will determine where the Moon actually is and seeing the image from the ventral stream, it’ll assume that the Moon is much closer. Tests were carried out with other objects and these theories were found to be accurate.
While these theories could be a potential reason why the Moon appears to be larger, scientists still aren’t sure and there might be a piece of this that we haven’t yet discovered. Stay tuned for future blogs in hopes that this mystery will finally be solved!
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