It has been known since ancient times and it must have been noticeable to many when you looked at the rising full moon that it seemed huge, while on other occasions it was of “normal” size – this is a lunar illusion. Not only do we see the Moon up to twice its size near the horizon, but we also see the Sun as well as the apparent distance of the lower stars and the size of the constellations. It is widely believed to be due to landmarks on the horizon. It is interesting, however, that astronauts experience a similar feeling during lunar clusters observed from Earth orbit, although there are no landmarks in the way that confuse the brain! It’s worth noting that there is a real difference in the apparent size of the moon depending on whether we see a near-full moon from Earth (also known as a “super moon” in places that don’t really seek scientific credibility) or a distant full moon, but the difference is much smaller than the difference between the moon. It gives us an illusion.
At moonrise or sunset, our celestial companion is close to the horizon, close to large known landmarks – such as houses, trees, and mountaintops – and this can trick our minds. In addition, the Ponzo illusion associated with the effect of perspective may also play a role. In the Ponzo illusion, we see two lines of exactly the same size placed in a shape similar to bars going into the distance, and then we see that the farthest line is much larger.
The known and repeatedly rejected response is based on how we perceive the sky. The sky rolls over us like a hemisphere, but we see it as a flat dome, in which case the things above our heads are seen as closer and the things on the horizon farther, and if the two objects cover the same area in our own. Retina (full moon has a diameter of 0.15 mm on the retina), then those close to the horizon should be larger.
The question is so complex that a psychologist is a professor the whole book Dedicated to the topic in 1989, with the help of several imaginary researchers, he compiled his work into 24 chapters, including psychological and neurophysiological aspects, and concludes without an exclusive and simple explanation. Another book came to a similar conclusion in 2002, and there is no single theory to explain the illusion.
Professor of Psychology and Neuroscience Another Longitudinal analysis in a study Countless theories in the interpretation of the lunar illusion, and came to the conclusion that there are so-called cases of microscopic examination of the eye or macro. By the way, this is the latest theory accepted by many (which, of course, has also been refuted many times). In this case, the illusion is related to how our eye-moving muscles work: if we notice the moon on the horizon, our eyes focus on infinity, while when the moon is high, we focus closely when there are no other visual cues. While in the first case the moon appears larger than the real one, in the second case it is smaller than the real one.
The theories are also analyzed in detail in a Hungarian study, Anyone who wants to dig deeper can read it here.
There is also a strange case: if one bends over and looks at the moon in the form of “face to face” between the legs, then the view on the horizon seems even smaller! (If you’re flexible enough, try it next time: look at it in a normal position and then lean into the rising moon!)
The fact that the moon is in fact exactly the same size, either on the horizon or above our head, is easily verifiable: we can cover it with the tip of our little finger either way (with our other fingers, but it is much larger than the half-degree diameter moon).
So what causes the lunar illusion? Science does not yet know a clear and provable answer to this question that has plagued us since Aristotle.
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