You've probably noticed that the Moon sometimes seems unnaturally large. This is usually most noticeable when it rises or sets. You might think that at this moment the natural satellite is closer to the Earth, but in fact this is not the case. The Moon seems larger near the horizon due to optical distortion of our perception. People tried to understand the reason for this effect more than two thousand years ago, but to this day the lunar illusion has not been fully solved. Nevertheless, in general the reason is already known, and most likely it will surprise you.
Scientists don't know why the Moon sometimes seems big. Photo source: rtraveler.ru
Contents
- 1 Why the Moon seems big
- 2 Why the lunar illusion occurs
- 3 The Moon may be bigger than it seems to us
- 4 Why astronauts in space also see the lunar illusion
Why the Moon seems big
Many optical phenomena are related to the features of our atmosphere. For example, this concerns the Fata Morgana phenomenon (when people see the “Flying Dutchman” or even entire cities), as well as all kinds of mirages. Therefore, it was initially assumed that the lunar illusion was also related to the atmosphere. For example, Aristotle in the 4th century BC assumed that when the Moon is visible on the horizon, the light from it passes to our eyes through a thick layer of the atmosphere. In his opinion, the atmosphere had the effect of a magnifying glass.
This theory does not seem absurd, unlike some of Aristotle's other ideas. Many optical phenomena are related to the refraction of rays. Therefore, it could be assumed that the atmosphere really does have the effect of a magnifying glass and brings an object closer. However, over time, scientists discovered that Aristotle was wrong.
In fact, we always see the Moon as the same size. Photo source: iflscience.com
As it turns out, the atmosphere does not actually make the Moon larger, and it does not increase in size at all – it just seems to us that our planet's natural satellite has increased in size. If you doubt this, just take a ruler and measure it. The diameter of the Moon at its rise will be exactly the same as after some time, when it is above your head.
Why does the moon illusion occur?
Considering all of the above, it is easy to guess that the moon illusion is related to perspective, which causes our brain to distort visual information. Scientists suggest that it is all about the brain's inability to estimate the size and distance of unusual objects, such as the Moon. However, it is not clear why this happens, and why does the natural satellite seem larger only when it is on the horizon?
The Ponzo Illusion – the top horizontal line appears further away and longer. Source: iflscience.com
This is thought to be because trees, buildings, and other objects on the horizon make the Moon appear closer. This makes the Moon appear larger. When the Moon is high in the sky, there are no visual cues in front of our eyes, so we perceive it as being further away and it appears smaller.
An example of how context affects the perception of size is the Ponzo illusion, where two identical horizontal lines appear to be of different lengths. The top line appears to be further away and larger. But if you put a ruler to it, you will see that they are exactly the same. If you turn the illustration upside down, the bottom line will appear longer and the top line will appear shorter. Perhaps a similar effect is observed with the Moon.
The Moon May Be Bigger Than We Think
So, it seems that depending on the context, our perception of the Moon's size changes. But which of the sizes we see is more accurate? Most likely, the brain correctly estimates the size of the Moon when it is on the horizon. In this case, we can estimate the size based on other objects that are nearby.
The size of an object depends on the context. Source: starwalk.space
When a satellite is high in the sky, the brain cannot objectively estimate the size, since there is no reference point. That is why the Moon does not seem big to us. Rather, it seems small to us when it is high.
Why do astronauts in space also see the lunar illusion
The explanation given above seems quite logical at first glance and even has indirect confirmation in the form of the Ponzo illusion. However, according to NASA, it is not ideal. The fact is that astronauts in orbit also encounter the lunar illusion, but they do not have any objects in front of their eyes that could distort the sense of size and distance.
Astronauts in space also see the lunar illusion. Photo source: az.sputniknews.ru
Therefore, it is not entirely clear what exactly makes our brain see the Moon, sometimes big, sometimes small. But, according to NASA, regardless of the reasons and how we perceive the Earth's natural satellite, the giant Moon is a beautiful sight. Therefore, until someone unravels the exact cause of the lunar illusion, we can just watch this sight and enjoy it.
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Finally, we note that we regularly encounter a variety of optical illusions. The thing is that our brain is very easy to deceive. Even vegetable and fruit sellers often take advantage of this. A striking example of how much our brain can distort visual information is a black and white photograph, which for some reason we see in color. To verify this, follow the link.