Why does the moon appear tilted?

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In summary, there is an ongoing debate about the explanation for the "moon illusion." Some suggest it is simply an optical illusion, while others argue that the laws of light transmission do not support this explanation. The use of panoramic photos and celestial spheres have been proposed as possible explanations. However, the use of a football illuminated by a bright light as an example suggests that the same reasoning could be applied to the moon and sun. Some sources for further explanation include a website and two research papers.
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Jackamus
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Observing a waning gibbous moon at about 8.00am one morning it appeared that its direction of illumination, a downwards angle of about 45º, could not be coming from the sun as the sun was much lower in the sky.
Researching this I found that the usual explanation was that it was an 'illusion'. However this explanation, in my opinion, does not stand-up to the laws governing the transmission of light. I proposed that as light travels in a straight line this poses a problem for moon tilt.
Most of the explanations appealed to the curved lines on panoramic photos whilst others appealed to the great circle of an imaginary celestial sphere.
I used, as an example, a football illuminated by a bright light. It is easy to see the direction of the light from observing the illuminated part of the football and tracing back in a straight line to the light. Why cannot the same reasoning be applied to the moon and sun since it is only a matter of scale?
 
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  • #2
What? Do you have any documentation of this phenomena or did you just observe with your eyes? And it sounds like you are saying that the moon isn't illuminated by the sun...? Huh?
 

1. Why does the moon appear tilted?

The moon appears tilted due to an optical illusion known as the "tilt illusion." This phenomenon occurs because our brains interpret the moon's orientation based on the surrounding objects and landscape. Since the moon is usually seen in the night sky with no surrounding objects, our brains try to make sense of its orientation by tilting it slightly.

2. Is the moon actually tilted?

No, the moon is not actually tilted. The moon's axis is nearly perpendicular to the plane of its orbit around the Earth, so it appears to be upright from our perspective on Earth. However, the moon does have a slight tilt of about 1.54 degrees, but this is not noticeable to the naked eye.

3. Does the moon's tilt change?

Yes, the moon's tilt does change slightly over time. This is due to the gravitational pull of the sun and other planets, which can cause the moon's axis to shift by a few degrees. However, these changes are very small and not noticeable to the average person.

4. Does the moon's tilt affect its phases?

No, the moon's tilt does not affect its phases. The phases of the moon are determined by its position in relation to the Earth and the sun, not its tilt. However, the tilt can affect the angle at which sunlight hits the moon's surface, which can create different lighting effects and shadows.

5. How does the moon's tilt impact Earth?

The moon's tilt has a minimal impact on Earth. It does not affect our seasons or tides, as these are mainly influenced by the tilt of Earth's axis. However, the moon's tilt does play a role in the stability of the Earth's rotation and the length of our days, as the moon's gravity helps to stabilize our planet's tilt.

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