Lunar Orbital paths traced on Earth?

[sdlawrence]

I have seen many sites that log and track lunar and solar eclipses, and which even have Google Earth overlays showing the various paths traced by the moon over the surface of the Earth, but only as they relate to eclipses.

To anyone's knowledge, has there ever been a graphic tracing of any kind done for lunar orbit over the surface of the Earth? Specifically, I am looking for a "Spirograph-like" tracing of a single 18.5996 year nodal cycle, using an imaginary line which intersects the center of gravity of both the Earth and the Moon, tracing this moving imaginary point over the surface of the Earth.

Even more specifically, I would like to convert this (as a vector drawing), using a plate carrée projection.

Anything? A resource, or someone that has already done this, or a program that would help me to accomplish the same thing?

Thanks in advance...

[Centaur]

I have seen many sites that log and track lunar and solar eclipses, and which even have Google Earth overlays showing the various paths traced by the moon over the surface of the Earth, but only as they relate to eclipses.

To anyone's knowledge, has there ever been a graphic tracing of any kind done for lunar orbit over the surface of the Earth? Specifically, I am looking for a "Spirograph-like" tracing of a single 18.5996 year nodal cycle, using an imaginary line which intersects the center of gravity of both the Earth and the Moon, tracing this moving imaginary point over the surface of the Earth.

Even more specifically, I would like to convert this (as a vector drawing), using a plate carrée projection.

Anything? A resource, or someone that has already done this, or a program that would help me to accomplish the same thing?

Thanks in advance...

Welcome to the discussion group, sdlawrence.

Apparently you are first referring to maps that show how the shadow of the Moon progresses across the Earth’s surface during a solar eclipse. Only people located along a rather narrow path are able to witness a total or annular eclipse. Regarding a lunar eclipse, you may be referring to maps that show the locations on Earth where it can be seen. Anyone experiencing nighttime under clear skies is able to observe a lunar eclipse.

Regarding the Earth-Moon barycenter (center of mass/gravity), it is located about a thousand miles beneath the surface of the Earth along the line connecting the centers of the Earth and Moon. So it plows along a roughly circular path through the Earth’s interior over a period of about 25 hours.

[sdlawrence]

Welcome to the discussion group, sdlawrence.

Apparently you are first referring to maps that show how the shadow of the Moon progresses across the Earth’s surface during a solar eclipse. Only people located along a rather narrow path are able to witness a total or annular eclipse. Regarding a lunar eclipse, you may be referring to maps that show the locations on Earth where it can be seen. Anyone experiencing nighttime under clear skies is able to observe a lunar eclipse.

Regarding the Earth-Moon barycenter (center of mass/gravity), it is located about a thousand miles beneath the surface of the Earth along the line connecting the centers of the Earth and Moon. So it plows along a roughly circular path through the Earth’s interior over a period of about 25 hours.

Thank you for the welcome, Centaur. I understand and agree with everything you wrote, however I am actually not interested in eclipses, the Earth-Moon barycenter, or anything related to the shadow of the Earth, or anything which can be observed from Earth.

If you draw an imaginary line between the centers of gravity of the Earth and the Moon, the mean barycenter will be along that point below the surface. What I want, however, is the single point where it intersects and traces a curve along the surface of the Earth, which will repeat (more or less, ignoring tidal friction/slowing/recession) like a Spirograph drawing, every 18.6 years. That is the curve I'm trying to get my grubbies on.

[sdlawrence]

Welcome to the discussion group, sdlawrence.

Apparently you are first referring to maps that show how the shadow of the Moon progresses across the Earth’s surface during a solar eclipse.

Thank you for the welcome. I replied much earlier, but for some reason my post never made it.

I am actually not interested in anything whatsoever to do with eclipses, shadows, or anything observable from Earth. I only used those as an example because there are some Google Earth .kmz files that do show partial traces of the lunar orbital path over the surface of the Earth. The Earth-Moon barycenter is an imaginary, moving point which just happens to rest along the same line that I am interested in, but the barycenter is not the point on the line that I want.



In my case it would be the point (not a shadow, but an imaginary point on an imaginary line) where that same line intersects the surface of the Earth, tracing a curve over the surface, again like a Spirograph, one that repeats every ~18.6 years.

[Swift]

Thank you for the welcome. I replied much earlier, but for some reason my post never made it.

sdlawrence - Your post made it, but it was waiting in the "moderation queue". All posts from all newbies are held in "limbo" until they can be approved by a moderator. It is nothing personal, it is just part of our anti-spam measures, and depending on how many moderators are on-line at a given time, it can sometimes take a couple of hours till it is approved. A couple of more posts and you won't have this problem any longer.

And welcome to BAUT.

[Tog]

I take it be the sine wave ground track for the Moon.

I found this, which might allow you to enter a "new" satellite that happens to be exactly where the Moon is. I'm really not sure.

This paper might have the formulas you need to work it out. I had two goes at algebra 1, so I'm really not sure.

[Centaur]

If you draw an imaginary line between the centers of gravity of the Earth and the Moon, the mean barycenter will be along that point below the surface. What I want, however, is the single point where it intersects and traces a curve along the surface of the Earth, which will repeat (more or less, ignoring tidal friction/slowing/recession) like a Spirograph drawing, every 18.6 years. That is the curve I'm trying to get my grubbies on.

The point on the Earth’s surface that lies along the line that includes the centers of the Earth, Moon and barycenter is on a track that circles the Earth in a period that averages 24.84 hours. The latitude of that circle will oscillate with a period of 27.3 days. The amplitude of those latitude swings will oscillate with a period of 18.6 years.

[sdlawrence]

Excellent, cheers all.

[Centaur]

Not only is that Earth-Moon diagram not to scale, but also the barycenter does not circle Africa. It more nearly circles the Earth’s rotational axis.

[grapes]

I thought the red line was the earth/moon barycenter depth.

[Centaur]

I thought the red line was the earth/moon barycenter depth.

Indeed, it would have been accurately so if a polar region were at the center.