Examining the Accuracy of "Moon's Orbit Around Earth"

In summary, the statement "the moon moves in a near-circular orbit around earth. because the Earth is so much more massive, it own motion is not appreciably affected by the moons presence" is true because the combined center of mass of the Earth-Moon system lies within the Earth, with the Earth's motion being only slightly affected by the Moon's presence. This is due to the fact that the Moon's mass is significantly smaller than the Earth's, resulting in the Earth essentially orbiting around a fixed point within itself. Additionally, this concept is further demonstrated through animations of the Earth-Moon and Pluto systems.
  • #1
unrepentant
2
0
hey,
can somebody please help me examine the truth of the statement

"the moon moves in a near-circular orbit around earth. because the Earth is so much more massive, it own motion is not appreciably affected by the moons presence"
?
 
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  • #2
unrepentant said:
hey,
can somebody please help me examine the truth of the statement

"the moon moves in a near-circular orbit around earth. because the Earth is so much more massive, it own motion is not appreciably affected by the moons presence"
?

Gravity affects both objects equally (equal and opposite reaction). The result is that both objects orbit their combined center of mass.

Mass of the Moon: 7.349 x 10^22 kg
Mass of the Earth: 5.9736 x 10^24 kg
Average distance between the two: 384,400 km

Find the combined center of mass and you'll find it lies inside the Earth. I guess "appreciably" is a subjective term, since the combined center of mass is still quite a ways from the Earth's center of mass.
 
  • #3
It's about 400 miles from centre is it not?
 
  • #4
According to this article - http://en.wikipedia.org/wiki/Center_of_mass

the barycenter of the earth-moon system is 4670 km from the center of the earth. For comparison, the Earth's radius is approximately 6380 km. The barycenter is about 1000 miles below the Earth's surface on a line between the center of the moon and center of earth.

Perhaps one is thinking of the barycenter of the sun-earth system.
If the Earth were the only satellite of the Sun and the Earth were moving in an elliptical orbit about the center of mass of the Sun-Earth system then the Sun would also be moving in an elliptical orbit about that same center of mass. The scales of the orbits would be in proportion to the ratio of the masses. The Sun is about 333 thousand times as massive as the Earth. Thus if the average radius of the Earth's orbit is 93 million miles (150 million km) then the radius of the Sun's counter orbit is about 280 miles (450 km). The center of mass of the Sun-Earth system is well within the body of the Sun.
http://www.applet-magic.com/centermass.htm - This also mentions the barycenter of the earth-moon system.
 
Last edited:
  • #6
hey thanks guys this info helped alot.
tony that animation was pretty good thanks
 

1. What is the purpose of examining the accuracy of the moon's orbit around Earth?

The purpose of examining the accuracy of the moon's orbit around Earth is to better understand the motion of the moon and its effects on Earth. It can also help improve our understanding of gravity and the larger structure of the solar system.

2. How is the accuracy of the moon's orbit measured?

The accuracy of the moon's orbit is measured using various methods such as ground-based telescopes, space-based satellites, and lunar laser ranging. These methods allow scientists to track the position and movement of the moon with great precision.

3. Why is it important to accurately measure the moon's orbit around Earth?

Accurately measuring the moon's orbit around Earth is important for several reasons. It allows us to predict eclipses and other lunar events, understand the impact of the moon on Earth's tides and climate, and validate theories about the formation and evolution of the solar system.

4. Can the accuracy of the moon's orbit change over time?

Yes, the accuracy of the moon's orbit can change over time due to various factors such as gravitational interactions with other celestial bodies, tidal forces, and the gradual slowing of the moon's rotation. This is why it is important to continually monitor and study the moon's orbit.

5. How does the accuracy of the moon's orbit impact daily life on Earth?

The accuracy of the moon's orbit has a significant impact on daily life on Earth. It affects the length and strength of tides, which can impact coastal communities and marine life. It also plays a role in the Earth's climate and weather patterns. Additionally, the moon's orbit is used in navigation, timekeeping, and agriculture.

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