# The Naked Scientists Forum

### Author Topic: What is the highest possible orbit of Earth?  (Read 12578 times)

#### Eric A. Taylor

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##### What is the highest possible orbit of Earth?
« on: 22/07/2010 10:47:29 »
I just heard about a satellite they plan to put into Earth orbit at an altitude of 1 million miles. At what altitude above Earth would the sun's gravity pull me out of Earth orbit?

#### yor_on

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##### What is the highest possible orbit of Earth?
« Reply #1 on: 28/07/2010 11:12:44 »
I started to wonder about that one too. It seems like something one could do, calculate it, knowing the mass of Earth versus the sun and then find the gravity's diminishing effect. As I took out my four colored pen and my dusty old slide-rule I suddenly realized that what you were asking for had to be its Lagranian point. That point where gravity takes out itself so to speak, so that all objects being there will feel no 'gravitational forces' acting on them.

Heh :)

And as I'm a natural lazy, proud to say it too :)
Earth-Sun Lagranian point

As an added plus you will know the Lagranian points for a lot of other planets too.
Ah, from the Suns point of view that is.

(Like the Sun would be the middle of our universe - Bah - We all know that it's Earth.)
==

Looking again I see they try to confuse us even more, involving all kinds of 'two body systems'
Wouldn't surprise me if they proclaimed that Earth was round either..

Don't let them fool us, we all know that water runs downward, a clear proof of what will happen when you come to the edge..

« Last Edit: 28/07/2010 11:24:32 by yor_on »

#### Eric A. Taylor

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##### What is the highest possible orbit of Earth?
« Reply #2 on: 30/07/2010 09:20:12 »
No sorry I'm not asking about Lagranian points. I'm wondering what is the highest stable orbit for Earth. Lagranian points are not orbits, technically speaking. They are points in space where the gravity between two masses is equal. There are even Lagranian points between you and your computer (or another person or another mass, but Earth's gravity is far stronger than yours so it's swamped.)

#### Soul Surfer

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##### What is the highest possible orbit of Earth?
« Reply #3 on: 30/07/2010 09:34:38 »
You are thinking fundamentally incorrectly.  Because the earth is a planet orbiting the sun anything that is orbiting the earth is also orbiting the sun.  This means that you cannot consider them as separate things.   You may not know it but the earth has (at least) two moons  There is a small asteroid in the earth's orbit that is controlled by the earth.  how does your current thinking look at effects like this?

go to   http://en.wikipedia.org/wiki/3753_Cruithne for details

#### tommya300

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##### What is the highest possible orbit of Earth?
« Reply #4 on: 30/07/2010 12:54:14 »
You are thinking fundamentally incorrectly.  Because the earth is a planet orbiting the sun anything that is orbiting the earth is also orbiting the sun.  This means that you cannot consider them as separate things.   You may not know it but the earth has (at least) two moons  There is a small asteroid in the earth's orbit that is controlled by the earth.  how does your current thinking look at effects like this?

go to http://en.wikipedia.org/wiki/3753_Cruithne for details

Wow I am confused here, all this time I was thinking that an orbit was a circular to elliptical path with its forces acting on the revolving body, from inside axial of an orb shape circle closed path.
The attempt to complete an orbit around either body is being interupted by these bodies themselves just as the body in question is about to complete the looped path about one body, the other opposite body's forces affect the path.

I have had thought from reading here; "An orbit is a regular, repeating path that an object in space takes around another one."

http://www.qrg.northwestern.edu/projects/vss/docs/space-environment/1-what-is-an-orbit.html

The repeated path is not completed around either affecting bodies.
It looks more like a flight path using only two timely gravitational corridors
I do not know if I am looking at this correctly or not. Please straighten out my path of perception
« Last Edit: 30/07/2010 13:46:49 by tommya300 »

#### Eric A. Taylor

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##### What is the highest possible orbit of Earth?
« Reply #5 on: 30/07/2010 21:55:36 »
The Earth/moon system orbits the sun together but the moon is not said to orbit the sun, as it's in orbit around the Earth.

Several years ago I read in SA that an object with very odd spectral signature was discovered in Earth orbit far beyond the moon. It was further discovered that the object had a very odd shape for an asteroid as well, quite long and thin. It was bright white, also very odd for an asteroid. It was found that the weird spectral signature matched something common on Earth; aircraft paint, more specifically the paint used to paint the Saturn 5 rocket boosters. It was a spent S-IV-B booster from one of the Apollo missions (I can't remember which. Most of them were sent on a course that impacted the moon, but due to where they wanted to land this was not possible for 2 of them, and they missed the moon and went into orbit around the sun. Years later Earth recaptured the booster but they said the orbit was not stable and it would eventually leave Earth again. It's still out there in an orbit close to Earth.

#### tommya300

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##### What is the highest possible orbit of Earth?
« Reply #6 on: 31/07/2010 06:41:56 »
The Earth/moon system orbits the sun together but the moon is not said to orbit the sun, as it's in orbit around the Earth.

Several years ago I read in SA that an object with very odd spectral signature was discovered in Earth orbit far beyond the moon. It was further discovered that the object had a very odd shape for an asteroid as well, quite long and thin. It was bright white, also very odd for an asteroid. It was found that the weird spectral signature matched something common on Earth; aircraft paint, more specifically the paint used to paint the Saturn 5 rocket boosters. It was a spent S-IV-B booster from one of the Apollo missions (I can't remember which. Most of them were sent on a course that impacted the moon, but due to where they wanted to land this was not possible for 2 of them, and they missed the moon and went into orbit around the sun. Years later Earth recaptured the booster but they said the orbit was not stable and it would eventually leave Earth again. It's still out there in an orbit close to Earth.

Thanks my view point is clearer now.
I was looking at the horseshoe path illustration. That is something I never seen that before. I was so fascinated I did not read this.

"Cruithne is in a normal elliptic orbit around the Sun. Its period of revolution around the Sun, approximately 364 days at present, is almost equal to that of the Earth. Because of this, Cruithne and Earth appear to "follow" each other in their paths around the Sun. This is why Cruithne is sometimes called "Earth's second moon".[2] However, it does not orbit the Earth and is not a moon."

« Last Edit: 31/07/2010 07:38:11 by tommya300 »

#### tommya300

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##### What is the highest possible orbit of Earth?
« Reply #7 on: 31/07/2010 14:15:18 »

No sorry I'm not asking about Lagranian points. I'm wondering what is the highest stable orbit for Earth. Lagranian points are not orbits, technically speaking. They are points in space where the gravity between two masses is equal. There are even Lagranian points between you and your computer (or another person or another mass, but Earth's gravity is far stronger than yours so it's swamped.)
.
Now that you had awakened my mind a little, learning about Lagrangian points.
Since the Lagrangian point is located approximately 1,500,000 km towards the Sun away from the Earth.
Shouldn't this be a factor to consider in determining the highest orbit of Earth?

http://en.wikipedia.org/wiki/List_of_objects_at_Lagrangian_points

Since we know the sun dominates the major gravitational affects throughout this solar system.
(I did not say all, just major, because of values smaller than Lagrangian points of other massive bodys relative to the sun.)
Should we not want to exceed this value at any point, in the orbit around the Earth?
Keeping this orbit a certain percentage below this value, so that the orbit can be maintained within the gravitational field of Earth at all times, right?

Wouldn't the orbit need to be a fraction smaller than this value?
Maybe 1,125,000 km, a 25% difference.
I picked 25% to cover good margin of error.

I am just thinking correct me if I am off on a tangent.

.

#### wolfekeeper

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##### What is the highest possible orbit of Earth?
« Reply #8 on: 31/07/2010 22:28:40 »
There's no basically highest orbit that is stable- all orbits are unstable over the long run. Low orbits are very stable but eventually wander, higher and higher orbits are progressively less stable. You normally get problems when the orbit is at the same altitude as the moon, because the moon tends to perturb it, but orbits that are synchronised with the moon can avoid blowing up for quite a while, but will eventually drift off.

However, if you're outside the 'sphere of influence' of the Earth then the orbit is very unstable, but even being slightly inside it won't make it magically stable.

#### wolfekeeper

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##### What is the highest possible orbit of Earth?
« Reply #9 on: 31/07/2010 23:03:55 »
Probably what you're asking for is the Hill sphere between L1 and L2 of the Sun/Earth system. It's essentially impossible to be in orbit outside that region.

#### tommya300

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##### What is the highest possible orbit of Earth?
« Reply #10 on: 01/08/2010 03:54:52 »
There's no basically highest orbit that is stable- all orbits are unstable over the long run. Low orbits are very stable but eventually wander, higher and higher orbits are progressively less stable. You normally get problems when the orbit is at the same altitude as the moon, because the moon tends to perturb it, but orbits that are synchronised with the moon can avoid blowing up for quite a while, but will eventually drift off.

However, if you're outside the 'sphere of influence' of the Earth then the orbit is very unstable, but even being slightly inside it won't make it magically stable.

I agree that the word stable does not relate to permanent. Everything degrades with time, and that varies with environment and other situations too.
The Moon approx, 350,000 km from the Earth relative to 1,125,000 km.
A 775,000 km difference with respect to the orbit value I presented.
The moon's gravitational affect being approx. 9 times less than that of earth, can the perturbing be negligible?
Will the orbit sustain a relatively, reasonably long duration of time? "Long meaning not ridiculously short."
I am trying to observe the original question by staying away from specifying a duration.
All the objects path needs to comply to, is the definition of a single orbit. I think two orbital revolutions to satisfy the word repeat. Highest one at that.

Probably what you're asking for is the Hill sphere between L1 and L2 of the Sun/Earth system. It's essentially impossible to be in orbit outside that region.

Yes when I seen that picture, that is what gave me the inspiration for my post.
Looking at the impossible and work backward from that
Can I be looking at it from a different viewing point?
« Last Edit: 01/08/2010 05:38:32 by tommya300 »

#### wolfekeeper

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##### What is the highest possible orbit of Earth?
« Reply #11 on: 01/08/2010 15:53:52 »
There's no basically highest orbit that is stable- all orbits are unstable over the long run. Low orbits are very stable but eventually wander, higher and higher orbits are progressively less stable. You normally get problems when the orbit is at the same altitude as the moon, because the moon tends to perturb it, but orbits that are synchronised with the moon can avoid blowing up for quite a while, but will eventually drift off.

However, if you're outside the 'sphere of influence' of the Earth then the orbit is very unstable, but even being slightly inside it won't make it magically stable.

I agree that the word stable does not relate to permanent. Everything degrades with time, and that varies with environment and other situations too.
The Moon approx, 350,000 km from the Earth relative to 1,125,000 km.
A 775,000 km difference with respect to the orbit value I presented.
The moon's gravitational affect being approx. 9 times less than that of earth, can the perturbing be negligible?
You'd think that, but orbits that go physically to about the same altitude as the moon are fairly weakly bound, the moon is right up at the edge of the Earth's orbit in energy terms, so it's actually VERY important at high orbital altitudes/energy.
Quote
Will the orbit sustain a relatively, reasonably long duration of time? "Long meaning not ridiculously short."
I am trying to observe the original question by staying away from specifying a duration.
All the objects path needs to comply to, is the definition of a single orbit. I think two orbital revolutions to satisfy the word repeat. Highest one at that.
Two isn't usually a problem, but when the moon is anywhere near, a lot of orbits just get flung out of the system over a few dozen orbits (a few months to years at lunar apogee).

#### tommya300

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##### What is the highest possible orbit of Earth?
« Reply #12 on: 01/08/2010 21:21:53 »
There's no basically highest orbit that is stable- all orbits are unstable over the long run. Low orbits are very stable but eventually wander, higher and higher orbits are progressively less stable. You normally get problems when the orbit is at the same altitude as the moon, because the moon tends to perturb it, but orbits that are synchronised with the moon can avoid blowing up for quite a while, but will eventually drift off.

However, if you're outside the 'sphere of influence' of the Earth then the orbit is very unstable, but even being slightly inside it won't make it magically stable.

I agree that the word stable does not relate to permanent. Everything degrades with time, and that varies with environment and other situations too.
The Moon approx, 350,000 km from the Earth relative to 1,125,000 km.
A 775,000 km difference with respect to the orbit value I presented.
The moon's gravitational affect being approx. 9 times less than that of earth, can the perturbing be negligible?
You'd think that, but orbits that go physically to about the same altitude as the moon are fairly weakly bound, the moon is right up at the edge of the Earth's orbit in energy terms, so it's actually VERY important at high orbital altitudes/energy.
Quote
Will the orbit sustain a relatively, reasonably long duration of time? "Long meaning not ridiculously short."
I am trying to observe the original question by staying away from specifying a duration.
All the objects path needs to comply to, is the definition of a single orbit. I think two orbital revolutions to satisfy the word repeat. Highest one at that.
Two isn't usually a problem, but when the moon is anywhere near, a lot of orbits just get flung out of the system over a few dozen orbits (a few months to years at lunar apogee).

Ah ok no disrespect, the light bulb got just a little brighter. I found this:
Throughout a satellites orbit there is a perfect balance between the gravitational force due
to the Earth, and the centripetal force necessary to maintain the orbit of the satellite.

So to get the distance I mentioned, the satellite would need an escape velocity and since this velocity, energy induced, permits the satellite to break free from earth's grav field, where would the energy come from to self sustain the orbit to repeat a return trip.

So for this max orbit, needs to be eliptical with a min and max altitude, and can it also be related to the value of the earths diameter? Since the moon's distance is 20 times earth's radius

#### wolfekeeper

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##### What is the highest possible orbit of Earth?
« Reply #13 on: 01/08/2010 22:01:16 »
It's not so simple unfortunately. The earth-sun-satellite is a 3 body problem.

The significance of this is that unlike a two body problem any body can steal/give energy from/to the other two. So in this case, the gravity of the sun, when it acts forwards along the orbit motion of the object's orbit around the Earth it adds energy to the object, and when it acts backwards, it removes energy. That's really what the Hill diagram is all about.

#### tommya300

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##### What is the highest possible orbit of Earth?
« Reply #14 on: 02/08/2010 12:17:13 »
.
Not to be obnoxious

Quote
http://science.howstuffworks.com/satellite3.htm

Satellites usually start out in an orbit that is elliptical. The ground control station controls small on-board rocket motors to provide correction. The goal is to get the orbit as circular as possible. By firing a rocket when the orbit is at the apogee of its orbit (its most distant point from Earth), and applying thrust in the direction of the flight path, the perigee (lowest point from Earth) moves farther out. The result is a more circular orbit.

We observe the moon's orbital path having this circular characteristic.
Also, if I interpret your previous post, ("You'd think that, but orbits that go physically to about the same altitude as the moon are fairly weakly bound, the moon is right up at the edge of the Earth's orbit in energy terms, so it's actually VERY important at high orbital altitudes/energy"), moons orbial distance from the Earth is at the edge of this energy envelope.

Can I safely say the moon's distance from the earth is the, "max conventional orbit ," that will sustain a balance and duration, providing the two orbits are synchronized and positioned ideally 180 degrees from eachother?

.

#### wolfekeeper

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##### What is the highest possible orbit of Earth?
« Reply #15 on: 02/08/2010 14:30:46 »
That's the Earth-moon L3 point. It's not very stable, but you would get quite a few orbits out of it.

If you want to get a feel for Lagrange point stability there's a reasonably cute java applet here:

http://www.princeton.edu/~rvdb/JAVA/astro/galaxy/Galaxy0.html

Select "l1-l5 M/m=40" and press start.
« Last Edit: 02/08/2010 14:38:25 by wolfekeeper »

#### tommya300

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##### What is the highest possible orbit of Earth?
« Reply #16 on: 02/08/2010 17:49:41 »
That's the Earth-moon L3 point. It's not very stable, but you would get quite a few orbits out of it.

If you want to get a feel for Lagrange point stability there's a reasonably cute java applet here:

http://www.princeton.edu/~rvdb/JAVA/astro/galaxy/Galaxy0.html

Select "l1-l5 M/m=40" and press start.

COOL, Thanks for that link! I will run it using different values to understand if more.
Well the title thread question originally, and the refinement in the first intro post asked, is there an exact value that satisfies the Questions? Ignore the stability and other factors, all is needed is to satisfy a repeated path.
Seeing that link shows me the stability of orbits and different ones at that I never knew possible.
« Last Edit: 03/08/2010 00:25:46 by tommya300 »

#### yor_on

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##### What is the highest possible orbit of Earth?
« Reply #17 on: 06/09/2010 11:37:59 »
Eric, I'm not sure there are any weightless points between me and my computer? But I can assure you that I will make the search for them a priority, and if I find one I will tell you :)

#### Eric A. Taylor

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##### What is the highest possible orbit of Earth?
« Reply #18 on: 01/10/2010 12:41:48 »
Good luck. The gravity field of a person (say 160 pounds) and a computer (say 30 pounds) is so week compared to Earth's that it's not measurable. Anything placed at an L-point on earth will be pulled out by Earth's gravity. However if you went into deep space (perhaps even outside the galaxy) you could place an object in an L-point, if you're careful not to bump it it will stay there

#### The Naked Scientists Forum

##### What is the highest possible orbit of Earth?
« Reply #18 on: 01/10/2010 12:41:48 »