Moon Orbits: Surprisingly Unstable! The Science Explained Simply (ELI5).

Published on 05/30/2025•Content Creation Opportunities / Question Hotspots

Content Idea: "ELI5: Why Your High School Physics Model of Gravity Fails for the Moon (Introducing Mascons!)"

Explanation/Core Content:

Start with the common understanding: Briefly explain the Shell Theorem – for a spherically symmetric body, the gravitational force on an external object is as if all the body's mass were concentrated at its center. This is a simplification often taught in high school.
Introduce the complication: The Moon isn't perfectly spherically symmetric. It has "mascons" (mass concentrations) – denser regions beneath the surface, often found in large impact basins.
Explain the effect: These mascons create localized areas of slightly higher gravity. As an orbiting object passes over these regions, it experiences varying gravitational tugs. This "lumpy" gravitational field perturbs the orbit, making it deviate from the perfect ellipse predicted by the simple model.
Consequence: Over time, these perturbations can accumulate, causing many orbits (especially low lunar orbits) to become unstable, eccentric, and eventually crash into the Moon or be flung away.
Contrast (optional): Mention that while Earth also has mass variations, its mantle is more fluid, allowing for greater isostatic adjustment. This makes Earth's gravitational field relatively smoother than the Moon's, especially concerning these localized, orbit-perturbing anomalies.

Hook/Viral Angle:

"What your physics teacher didn't tell you about the Moon's gravity!"
"The Moon's Lumps: The Secret Reason Lunar Orbits are Treacherous."
"Think gravity is simple? The Moon will surprise you."

Target Audience:

Students: High school or early college physics/astronomy students who have learned basic gravitational principles.
Space Enthusiasts: People interested in space exploration, orbital mechanics, and the peculiarities of celestial bodies.
Curious Learners: Individuals who enjoy "explain like I'm 5" content or learning about scientific concepts that challenge common assumptions.
Myth Debunkers: Those who appreciate content that clarifies misconceptions or oversimplifications in science.

This idea taps into the "I thought X, but it's actually Y (and here's the cool reason why)" structure, which is inherently engaging. It addresses a specific point of confusion ("Is this not the case?") with a clear explanation of a more complex reality.

Origin Reddit Post

r/askscience

Are orbits around the moon stable indefinitely?

Posted by u/Eve_Asher•05/30/2025

My understanding is that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere at that height which slows it down over time. Would an object put i

Top Comments

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/DeadlyPancak3

Technically you experience less gravity at the top of a mountain than at its base. Surface gravity on Earth also varies slightly based on the density of the material below the surface. The ne

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/DeadlyPancak3

Technically you experience less gravity at the top of a mountain than at its base. Surface gravity on Earth also varies slightly based on the density of the material below the surface. The ne

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/Simon_Drake

[https://en.wikipedia.org/wiki/Indian\_Ocean\_Geoid\_Low](https://en.wikipedia.org/wiki/Indian_Ocean_Geoid_Low) The bottom of India is an arrow pointing at it. The difference is 0.005%. The

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/FjorgVanDerPlorg

Earth's mantle is much more uniform, so you don't see the same "gravity well" problems you get with lunar orbits. There are no human perceptible gravity variations on planet earth.

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/DeadlyPancak3

Technically you experience less gravity at the top of a mountain than at its base. Surface gravity on Earth also varies slightly based on the density of the material below the surface. The ne

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/FjorgVanDerPlorg

Earth's mantle is much more uniform, so you don't see the same "gravity well" problems you get with lunar orbits. There are no human perceptible gravity variations on planet earth.

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/warp99

Yes. There are a class of orbits which are stable and this includes NRHO which Artemis is using to transfer from Orion to a lander.

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/Simon_Drake

[https://en.wikipedia.org/wiki/Indian\_Ocean\_Geoid\_Low](https://en.wikipedia.org/wiki/Indian_Ocean_Geoid_Low) The bottom of India is an arrow pointing at it. The difference is 0.005%. The

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/FjorgVanDerPlorg

Earth's mantle is much more uniform, so you don't see the same "gravity well" problems you get with lunar orbits. There are no human perceptible gravity variations on planet earth.

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/yatpay

There is a class of orbit called [Distant Retrograde Orbits](https://en.wikipedia.org/wiki/Distant_retrograde_orbit) which *are* very stable around the Moon. But as the name implies, they're

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/Schwingzilla

I was under the impression that anything outside a sphere enclosing an object, centered on the center of gravity, was equivalent to a point mass or uniform sphere of mass gravitationally. Is

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/haruuuuuu1234

Is this the same video where he talks about the elusive returning Apollo 10 LEM and figuring out who was responsible for the floating turd? If it's not, that's another one of Scotts videos w

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/[deleted]

[removed]

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/MarkNutt25

There is also a phenomena called a "[Frozen Orbit,](https://en.wikipedia.org/wiki/Frozen_orbit)" where, if you have a detailed enough mapping of the perturbations in the body's gravitational

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/cnz4567890

While "forever" is a strong word in orbital mechanics, these orbits are stable for geological timescales—meaning millions to billions of years. For anyone considering a lunar space station o

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/Dickulture

ISS is also not immune to decaying orbit phenomena. When the space shuttle was still active, NASA used it to boost ISS up now and then to keep it out of atmospheric drag, but ISS is getting o

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/atomfullerene

And the flip side of this is that most orbits around the earth are stable...ones quite close to the atmosphere or too near the moon's orbit are unstable, but the earth has a much larger gravi

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/fixermark

This was one of the concerns in the Apollo landing. They had a pretty good model of the moon's gravity, but so-called "mascons" (mass concentrations, likely places where the moon is unusually

u/dsyzdek

These were mapped to increase the precision of nuclear missiles. Ballistic missiles typically don’t have guidance for most of their flight and are traveling, well, “ballistically,” and so the

u/LeMAD

The ISS has booster modules and is regularly boosted by spacecrafts like Dragon to maintain its 400km orbit. Otherwise it would crash on earth in about 4-5 years.

u/CrooklynzFinest

Do we know which regions on Earth have the lowest/highest gravity and would a difference be felt for a human if they went from region with the lowest gravity to a region with the highest grav

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/ThetaReactor

We have [maps](https://www.newscientist.com/article/dn24068-gravity-map-reveals-earths-extremes/). You wouldn't notice the difference, it's less than a 1% change between the extremes.

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/OlympusMons94

There are, however, many [frozen lunar orbits](https://en.wikipedia.org/wiki/Frozen_orbit) that are long-term stable (although the inclination, eccentricity, etc. often have small-amplitude o

u/Eve_Asher

Great info, thank you, effectively how long would these kind of orbits be stable for?

u/vpai924

Quite the opposite, actually. Most lunar orbits are unstable. The moon isn't perfectly uniform. Variations in density causes orbits to become more eccentric over time until the periapsis b

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

u/Groftsan

So, do satellites in a high-moon orbit essentially trigger the three body problem, in that they're been affected by both the moon and earth?

u/vpai924

That's a useful approximation that's accurate enough over short timescales... but it's only an approximation. Especially for low orbits.

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/Simon_Drake

That's a very good guess. Based on what causes orbits to decay around the Earth it certainly looks like orbits around the moon would be stable long term. However the strength of the moon's g

u/MC_Gambletron

Could a planet with human-noticable gravitic differences theoretically exist? Or would it tear itself apart?

u/Solesaver

>Or would some interaction between the earth/moon system make that orbit unstable? This is poking at the three body problem. Well, technically the four body problem. The answer is mostly

u/TheCountMC

It's only strictly true if the mass distribution is spherically symmetric. For that reason it's called the shell theorem. https://en.wikipedia.org/wiki/Shell_theorem The theorem will only

u/Andrew5329

>that earth orbits mostly decay because of the object in orbit striking the extremely tenuous atmosphere That's the case in LOW Earth orbit, which is a feature not a bug. It's very easy t

u/Gutter_Snoop

Iirc correctly NASA did do a couple of surveys prior to the lunar landing to chart gravitational irregularities. However, turns out even then navigating that sort of thing is still tricky.

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/Kittymahri

That theorem applies to spherically symmetric bodies (plus inverse square forces in 3D). A lopsided body will not have such a “nice” gravitational field.

u/iCowboy

The highest gravity on the surface of the Earth is on the surface of the Arctic Ocean, the lowest is in the Peruvian Andes. There’s about 0.07ms2 difference between the two extremes, so you w

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