Why Does the Moon & Earth Have Different Relationships with the Sun?

In summary, the Moon is able to keep the same face toward the Earth due to tidal locking, which is caused by the Moon's proximity and smaller size compared to the Earth. This results in a short tidal lock time for the Moon, while the Earth's tidal lock time is much longer. This phenomenon is also seen in other close-in moons, with the exception of Hyperion, due to the influence of the inverse cube law (1/R3). It is also possible for any orbiting body to eventually become tidally locked over time.
  • #1
Martin Rattigan
330
3
Why does the Moon keep the same face toward the Earth but the Earth not keep the same face toward the Sun?
 
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  • #2
It's tidal locking. Tidal forces are proportional to 1/R3.

The Moon is much closer to the Earth than the Earth is to the Sun. The Moon is also much smaller than the Earth and much lumpier than the Earth. All of these things combine to make the tidal lock time for the Moon an extremely short time (astronomical time frame) while the tidal lock time for the Earth is very, very long.
 
  • #3
I thought that was probably it. Do you know of anywhere that goes thro' the mechanics of that?

OK - I found something thro' Google - Thanks.
 
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  • #4
Indeed, no planets are tidally locked, and almost all close-in moons are. (I think there is one exception - Hyperion) R3 is the reason.
 
  • #5
I've wondered about this, for a while: Is it correct to assume that, given enough time, any orbiting body will become tidally locked?
 

1. Why does the distance between the Moon and Earth affect their relationship with the Sun?

The distance between the Moon and Earth plays a significant role in their relationship with the Sun. This is because the distance affects the strength of the gravitational pull between the three bodies. The closer an object is to the Sun, the stronger the gravitational pull it experiences. Therefore, the Moon's distance from the Earth affects its orbit around the Earth and its position in relation to the Sun.

2. How does the Moon's orbit around the Earth affect its relationship with the Sun?

The Moon's orbit around the Earth is elliptical, meaning it is not a perfect circle. This causes the Moon's distance from the Earth and the Sun to vary throughout its orbit. When the Moon is closer to the Sun, it experiences a stronger gravitational pull and appears larger in the sky. When it is farther away, the gravitational pull is weaker and the Moon appears smaller. This is why we have different phases of the Moon, as it reflects different amounts of sunlight depending on its position in its orbit.

3. Why does the Earth's tilt affect its relationship with the Sun?

The Earth's tilt is the reason for the changing seasons on our planet. When the Earth is tilted towards the Sun, the Sun's rays hit the Earth more directly, resulting in warmer temperatures and longer days. When the Earth is tilted away from the Sun, the rays hit at an angle, causing cooler temperatures and shorter days. This tilt also affects the Moon's relationship with the Sun, as it changes the amount of sunlight the Moon reflects back to Earth.

4. How does the Moon's lack of atmosphere affect its relationship with the Sun?

The Moon's lack of atmosphere means it has no protection from the Sun's radiation. This results in extreme temperature differences on the Moon's surface, with temperatures reaching up to 260°F (127°C) during the day and dropping to -280°F (-173°C) at night. This lack of atmosphere also means the Moon has no weather, so there are no clouds or wind to regulate the temperature. This has a direct impact on the Moon's relationship with the Sun and its ability to sustain life.

5. Why does the Moon have a smaller impact on the Earth's tides compared to the Sun?

The Moon has a smaller impact on the Earth's tides compared to the Sun because of its smaller mass. While the Moon is much closer to the Earth than the Sun, it only has about 1/81 the mass of the Sun. The Sun's gravitational pull on the Earth is about 178 times stronger than the Moon's, which is why the Sun has a greater influence on the tides. However, the Moon's closer proximity to the Earth means it still has a significant impact on the tides, causing them to change twice a day.

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