Does the Moon's Orbit Stay the Same?

  • Thread starter mubashirmansoor
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In summary: The term prograde orbit is used to describe an orbit in which the center of the orbit moves forward compared to the direction of the orbiting objects' motion. Near the Moon, the gravitational pull of the Earth and Sun are very strong, so the Moon's orbit is in a prograde orbit. But because the Moon's orbit is tilted by 5 degrees to the ecliptic plane, it misses the Earth every month by a little over 1/6th of the Earth's circumference, or about 5,000 kilometers. At the same time, the Moon is also moving away from the Earth at a rate of about 1,500 kilometers per day. So every month, the Moon's orbit brings it a little bit closer
  • #1
mubashirmansoor
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Hello,
I wanted to know if moon's orbit is always in the same route and that it never change? if no why??

Thankyou.
 
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  • #2
No it isn't it chages. It's why we don't have a solar elcipse and a lunar elcipse every month.
 
  • #3
scott1 said:
No it isn't it chages. It's why we don't have a solar elcipse and a lunar elcipse every month.

No, The reason we don't have eclipses every month is that the Moon's orbit is tilted to the ecliptic.

But to answer the original question, the Moon's orbit does vary over time. It increases in size by about 4cm a year, it precesses, it is stretched and squeezed by tidal froces from the Sun, etc.
 
  • #4
Is the only change in orbit 4 cm per year, as you pointed out we don't have an eclipse each mont, doesn't this mean that the changes are so often? I would be glad if someone would be able to provide me with the orbital details. Thankyou.
 
  • #5
It depends on what you mean by "changes". ALL of the properties of the Moon's orbit that Janus mentioned except the increase in size are cyclical and therefore can be said to be constant from a certain point of view. Heck, even the tilt of the Earth's axis and the shape of the Earth's orbit affect when/where we get solar and/or lunar eclipses and they don't have anything to do with the shape and orientation of the moon's orbit.

About a third of the way down on this site are the various periodic properties of the moon's orbit (which doesn't include all the Earth's motion's affects on the moon's position in the sky): http://en.wikipedia.org/wiki/Moon

But if your question is just about whether the moon will be exactly the same place in the sky the next time it hits full as it was the last time it hit full, then no, it will not.
 
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  • #6
'Changes' in the moon's orbit over your lifetime are essentially negligible, but as Janus and Russ pointed out, there are many aspect that change if you are looking for precise calculations or long-term views.

mubashirmansoor said:
Is the only change in orbit 4 cm per year, as you pointed out we don't have an eclipse each mont, doesn't this mean that the changes are so often?

If the moon orbited the Earth in the same plane as the Earth-Sun orbit, then there would be a solar eclipse (and a lunar eclipse) every month. But the moon's orbit is skewed by 5 degress (if I recall correctly) from that plane, so the proper lining-up of the sun-earth-moon (horizontally and vertically with respect to that plane) for an eclipse is much rarer.
 
  • #7
Bye-Bye Moon...the orbit of the moon does change. Much earlier in history long the moon was closure to the Earth, but is slowly expaning in its orbit from Earth--some day there will no longer be a Moon--Question is, would the Sun in its dying throws consume the Earth before the Moon slips away.
 
  • #8
Here's a link to an animate GIF showing the Moon's orbit over an 18 year period, the "Saros cycle". This may help illustrate why eclipses can only happen every 6 months.

http://www.orbitsimulator.com/gravity/saros.GIF

It illustrates the precession of the Moon's orbital nodes. Notice the Moon's perihelion and aphelion also trade places at a rate of about twice per Saros cycle.

Most of the motion you see here is caused by the Sun's strong influence on the Moon at its present distance. The Moon orbits the Earth at a distance of almost 1/3 of the Earth's Hill Sphere radius. 1/3 of this radius is approximately the boundry between where things can orbit in prograde orbits and still keep a relatively round stable orbit.
 

1. How does the Moon's orbit stay the same?

The Moon's orbit stays the same due to the balance between its speed and the force of gravity. The Moon is moving at a constant velocity, but it is also being pulled towards the Earth by its gravitational force. This results in a curved path around the Earth, creating a stable orbit.

2. Does the Moon's orbit ever change?

Yes, the Moon's orbit does change slightly over time due to various factors such as the pull of other celestial bodies and the Earth's changing shape and rotation. However, these changes are very small and do not significantly affect the overall stability of the Moon's orbit.

3. How long does it take for the Moon's orbit to complete one revolution?

The Moon's orbit around the Earth takes approximately 27.3 days to complete one revolution. This is known as the sidereal month, which is slightly shorter than the time it takes for the Moon to go through all its phases (known as the synodic month).

4. Is the Moon's orbit perfectly circular?

No, the Moon's orbit is not perfectly circular. It is slightly elliptical, meaning that the distance between the Moon and the Earth varies slightly throughout its orbit. At its closest point (perigee), the Moon is about 363,000 kilometers away from Earth, while at its farthest point (apogee), it is about 405,000 kilometers away.

5. Can the Moon's orbit ever change significantly?

While the Moon's orbit does experience small changes over time, it is not expected to change significantly in the near future. However, in about 5 billion years, the Moon's orbit is predicted to become more elliptical due to the gradual slowing down of the Earth's rotation and the tidal forces between the Earth and the Moon.

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