# Question about the Sun's gravitational influence on the Earth and its moon

• B
• Evenlander
In summary, the sun's gravitational influence on the Earth and its moon causes them to orbit around a common center of gravity which in turn orbits around the sun. This is due to the initial conditions and Newton's law of gravity, and once the orbits are stable, it takes a lot of momentum to change them. Jupiter also has moons, but the moon's distance from Earth is only about 0.2% of the Earth-sun distance, so the wobble in its orbit around the sun is not noticeable. However, there are three body systems where the moon has a horseshoe orbit around the sun while following the Earth's orbital path.
Evenlander
If the sun has a gravitational influence on Earth and on its moon then why isn't the moon revolving around the sun. If the gravitational force of sun is large enough to make planets like Jupiter revolve around it (which has a greater mass than that of the moon.) Why not moon?

Evenlander said:
If the sun has a gravitational influence on Earth and on its moon then why isn't the moon revolving around the sun. If the gravitational force of sun is large enough to make planets like Jupiter revolve around it (which has a greater mass than that of the moon.) Why not moon?

What makes you think the Moon is not orbiting the Sun?

russ_watters, vanhees71, Vanadium 50 and 2 others
Hello Evenlander, !

Earth and moon orbit around a common center of gravity. That center of gravity orbits around the sun. Matter of initial conditions and Newtons law of gravity. Once the orbits are stable there 's a lot of momentum needed to change them.

Jupiter has moons too

Evenlander
PeroK said:
What makes you think the Moon is not orbiting the Sun?

A.T. said:
@Evenlander note this quote from the above page:

“The Sun's gravitational effect on the Moon is more than twice that of Earth's on the Moon; consequently, the Moon's trajectory is always convex[24][25] (as seen when looking Sunward at the entire Sun–Earth–Moon system from a great distance outside Earth–Moon solar orbit)”

Dale
Evenlander said:
To be more specific, the Earth-moon system's orbit around the sun is 149.6 +/- 0.5 million km in radius (it's elliptical). The moon is 0.36 million km from Earth, or about 0.2% of that distance. If you animated that and deleted the Earth, you probably wouldn't even notice the wobble in the moon's orbit around the sun.

Dale
russ_watters said:
you probably wouldn't even notice the wobble in the moon's orbit around the sun.
Around +/- 0.2% of wobble (about 300 thousand km in 150 million km), with about 13 cycles of 'wobble' on the way round. It never 'goes backwards' in its orbit round the Sun.
There are three body systems where the 'moon' body has a horseshoe orbit around the 'sun' body, whilst more or less following the orbital path of the 'earth' body. That link can be initially confusing.

## 1. What is the Sun's gravitational influence on the Earth and its moon?

The Sun's gravitational influence on the Earth and its moon is significant, as it is the primary force that keeps them in their respective orbits. The Sun's mass and proximity to the Earth and its moon create a strong gravitational pull that keeps them in a stable orbit around the Sun.

## 2. How does the Sun's gravity affect the tides on Earth?

The Sun's gravitational pull also affects the tides on Earth. The Moon's gravitational pull is stronger than the Sun's, but since the Sun is much larger and closer to the Earth, it still has a noticeable influence on the tides. When the Sun, Moon, and Earth are aligned, their combined gravitational pull creates higher and lower tides, known as spring tides.

## 3. Does the Sun's gravity affect the Earth's rotation?

Yes, the Sun's gravitational pull does affect the Earth's rotation. The Earth's rotation is slightly slowed down by the Sun's gravitational pull, but this effect is very small and not noticeable to humans. However, the Moon's gravitational pull has a greater impact on the Earth's rotation.

## 4. How has the Sun's gravitational influence on the Earth and its moon changed over time?

The Sun's gravitational influence on the Earth and its moon has remained relatively constant over time. However, the Earth's distance from the Sun does vary slightly due to its elliptical orbit, which can affect the strength of the Sun's gravitational pull. Additionally, the Moon's orbit around the Earth is gradually increasing, which will eventually result in a slower rotation of the Earth and a longer month.

## 5. Can the Sun's gravitational pull on the Earth and its moon change?

The Sun's gravitational pull on the Earth and its moon can change, but only under extreme circumstances. For example, if a large object were to pass close to the Earth or the Sun, it could have a temporary effect on the gravitational pull. However, the overall gravitational pull of the Sun on the Earth and its moon is unlikely to change significantly in the foreseeable future.

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