What force counteracts the solar wind for planets?

[JTsyo]

I was thinking about issues that would be faced with space based solar power and station keeping came to mind. That got me thinking about the planets. Sure their mass is huge and the solar wind would be a small ratio in comparison to their mass but it would have had 4 billion years to act. Is there something that balances the solar wind or do the solar orbits expand with time? Has the orbits already reached the equilibrium between gravity, solar wind and tangential velocity?

Also to return to the original thought would stations outside Earth orbit (Lagrange points?) need to expend much energy for station keeping?

 

[MrPickins]

Originally posted by: JTsyo
I was thinking about issues that would be faced with space based solar power and station keeping came to mind. That got me thinking about the planets. Sure their mass is huge and the solar wind would be a small ratio in comparison to their mass but it would have had 4 billion years to act. Is there something that balances the solar wind or do the solar orbits expand with time? Has the orbits already reached the equilibrium between gravity, solar wind and tangential velocity?

Also to return to the original thought would stations outside Earth orbit (Lagrange points?) need to expend much energy for station keeping?

This was my first thought.

Edit: If the force of the solar wind is directly opposed to the force of gravity, the effect would simply be that the net centripetal force on the earth would be slightly less. Our current orbit would already account for that.

 

[Zepper]

Even though more infinitesimal, the solar winds from many other stars also impinge on Earth and there are LOTs more of them. Then we have gravitation from all those celestial bodies, and perhaps forces that haven't even been discovered yet. But still, an approximate equilibrium will do.
. There can be no true equilibrium (nothing else being as constant as change ;-) as the theory says the universe will die a "heat death". Given enough time, the Moon will reach the tipping point and fall into the Earth's gravity well, likewise the Earth to the Sun. Of course that is if something unexpected doesn't interfere.
. If the human race wants to last longer than our Solar System (or even just our local part of it), then we'd better get on with it and get out there. I understand Earth's orbit is shrinking constantly as well as its velocity. Who knows when we'll reach the thermal tipping point and we'll all be toasted like hot dogs on sticks over the great campfire in the sky...

.bh.

 

[PCBeal23]

Originally posted by: Zepper
Given enough time, the Moon will reach the tipping point and fall into the Earth's gravity well, likewise the Earth to the Sun. . . Who know's when we'll reach the thermal tipping point and we'll all be toasted like hot dogs on sticks over the great campfire in the sky...

.bh.

Zepper, do you have any references to back this up?

It is my understanding that the entire solar system works on a system of balances, which helps keep equilibrium for the time being. In fact, most cosmologists and physicists are more worried about the sun burning out in 5 billion years than the Earth's orbit decaying.

As for the moon, the Sun-Moon-Earth system works much the same way. The sun's gravitational pull is working on the Moon just as much as the Earth's. True, the Moon is not always sandwiched between the Earth and Sun, but it's pull is great enough to keep the Moon's orbit from decaying. Also, as a side note, the shape of the Earth's and Moon's separate orbits also attributes to their "steady" state.

As far as the original question, the force from solar wind is so infantesimal that a proper "solar sail" would be kilometers in diameter in order to harness enough to propel a spacecraft. (Physics of the Impossible by Michio Kaku)

As such, the force of solar wind on a planet is easily overcome by the planet's mass (remember, a even though a sphere has the best surface area-to-volume ratio, this is not true of surface area-to-mass ratio as certain elements in the planet may be far more dense than others, throwing off any density/mass calculations). Think of aiming a ceiling fan at a big rock. True, gravity does come into play, but only because a planet's mass means the relative gravity is pulling harder on it.

It's all about mass

 

[Zepper]

A couple of atricles:

http://en.wikipedia.org/wiki/Earth
wiki.answers.com/Q/What_is_the_rate_of_decay_of_earths_orbit_around_the_sun

yield some interesting references.

plus I've heard some "scientists" mention recent evidence of orbital decay on some shows like Nature and Nova.

And common sense would offer that since gravity is a non-linear force, that orbital decay would eventually increase in a non-linear fashion. OTOH, considering the spans of time involved, something much more abrupt is likely to cause Earth to become uninhabitable a lot sooner (say as the Moon seems to be receding from Earth for some reason - what if it got pulled away as apparently it helps moderate Earth's climate). IAC, if at least enough of us humans haven't made the effort to be somewhere else by then (whenever "then" is), then we're SOL (chaos theory states that in a nexus set of conditions, the window of opportunity isn't infinite) and the issue is moot.

.bh.

 

[silverpig]

Originally posted by: Zepper
Even though more infinitesimal, the solar winds from many other stars also impinge on Earth and there are LOTs more of them. Then we have gravitation from all those celestial bodies, and perhaps forces that haven't even been discovered yet. But still, an approximate equilibrium will do.
. There can be no true equilibrium (nothing else being as constant as change ;-) as the theory says the universe will die a "heat death". Given enough time, the Moon will reach the tipping point and fall into the Earth's gravity well, likewise the Earth to the Sun. Of course that is if something unexpected doesn't interfere.
. If the human race wants to last longer than our Solar System (or even just our local part of it), then we'd better get on with it and get out there. I understand Earth's orbit is shrinking constantly as well as its velocity. Who knows when we'll reach the thermal tipping point and we'll all be toasted like hot dogs on sticks over the great campfire in the sky...

.bh.

Uh, the moon is getting FARTHER from the earth all the time...

 

[Zepper]

For now it is, but things can change... I wouldn't say that either case would be good for us.

.bh.

 

[silverpig]

Originally posted by: Zepper
For now it is, but things can change... I wouldn't say that either case would be good for us.

.bh.

In order for the moon to crash into the earth, it has to lose energy somehow. There has to be dissipation somewhere. Right now the moon is gaining energy. At some point the earth will be tidally locked with the moon, but that will take hundreds of millions, if not billions, of years. It would take something really drastic, like a moon-sized chunk of stuff hitting the moon, to change this.

Saying something vague like "things can change" doesn't offer anything of value.

 

[AstroGuardian]

Originally posted by: silverpig

Originally posted by: Zepper
For now it is, but things can change... I wouldn't say that either case would be good for us.

.bh.

In order for the moon to crash into the earth, it has to lose energy somehow. There has to be dissipation somewhere. Right now the moon is gaining energy. At some point the earth will be tidally locked with the moon, but that will take hundreds of millions, if not billions, of years. It would take something really drastic, like a moon-sized chunk of stuff hitting the moon, to change this.

Saying something vague like "things can change" doesn't offer anything of value.

No, the Moon is not gaining energy. The Moon has it's initial energy and if you project the parameters to the future, the Moon-Earth equilibrium of forces goes to moon drifting away from earth's gravity. It's the same situation with Mars and Phobos. Phobos has less kinetic energy to keep it steady orbit around Mars, so it will crash eventually.

As for the solar wind, it's known that it interacts with earth's magnetic field. So when SW reaches the earth's magnetic field it slightly pulls the earth's core (where magnetic field comes from). This compensates the pushing and pulling forces.
Even having this in mind, the SW is so weak, it does almost nothing to earth's orbit.

Another important parameter is SW existed during the formation of earth and other planets. So the current equilibrium is based on the forces of SW too.

Stations in orbit are placed inside the earth's magnetic field so it additionally helps in the protection. And again the forces are too weak to cause problems with orbits.

Best way to see how SW interact and change orbits is through observing a comet's tail. The SW interacts with particles from the comet and again those particles are extremely small and light. In time, even those particles find their equilibrium in the solar system. And that's why we get regular meteor showers for years after the comet is long gone

 

[silverpig]

Originally posted by: AstroGuardian

Originally posted by: silverpig

Originally posted by: Zepper
For now it is, but things can change... I wouldn't say that either case would be good for us.

.bh.

In order for the moon to crash into the earth, it has to lose energy somehow. There has to be dissipation somewhere. Right now the moon is gaining energy. At some point the earth will be tidally locked with the moon, but that will take hundreds of millions, if not billions, of years. It would take something really drastic, like a moon-sized chunk of stuff hitting the moon, to change this.

Saying something vague like "things can change" doesn't offer anything of value.

No, the Moon is not gaining energy. The Moon has it's initial energy and if you project the parameters to the future, the Moon-Earth equilibrium of forces goes to moon drifting away from earth's gravity. It's the same situation with Mars and Phobos. Phobos has less kinetic energy to keep it steady orbit around Mars, so it will crash eventually.

As for the solar wind, it's known that it interacts with earth's magnetic field. So when SW reaches the earth's magnetic field it slightly pulls the earth's core (where magnetic field comes from). This compensates the pushing and pulling forces.
Even having this in mind, the SW is so weak, it does almost nothing to earth's orbit.

Another important parameter is SW existed during the formation of earth and other planets. So the current equilibrium is based on the forces of SW too.

Stations in orbit are placed inside the earth's magnetic field so it additionally helps in the protection. And again the forces are too weak to cause problems with orbits.

Best way to see how SW interact and change orbits is through observing a comet's tail. The SW interacts with particles from the comet and again those particles are extremely small and light. In time, even those particles find their equilibrium in the solar system. And that's why we get regular meteor showers for years after the comet is long gone

Uh, the moon certainly is gaining energy. The earth rotates once every 24 hours. The moon revolves about the earth once every 29.5 days. The tidal forces of the moon pull the earth so that it has a bulge which faces the moon (high tide). This bulge rotates away from the moon, pulling it along in its orbit slightly, giving it energy.

The moon currently moves something like a centimeter or two away from the earth every year because of this effect (which means it is GAINING energy from the Earth's rotation). The net effect is the lunar month is getting slightly longer, and the day is getting slightly longer as well. At some point in the future the earth's rotation and the moon's revolution will be tidally locked, meaning that the moon will stay in one place in the sky and will never set nor rise.

This has already happened to the moon's rotation and is why there is a dark side and an earth side of the moon.

Also your first paragraph doesn't make sense.

 

[earthman]

Gravitational forces between celestial bodies far outweigh effects like solar wind. The complex gravitation relationships between the sun, moon, earth, and nearby planets will have far more cumulative effects, over time, I think. Bear in mind that the sun is the most dynamic element as well. In about 4-5 billion years current models show the sun becoming a red giant which will engulf the inner planets, before gradually shrinking to a white dwarf, rendering this argument moot.

 

[Eeezee]

Gravity + Angular Momentum >>>>>>>> Solar Wind

Solar winds have a negligible effect on the Earth's orbit.

 

[AstroGuardian]

Which paragraph?

 

[silverpig]

Originally posted by: AstroGuardian
Which paragraph?

This one:

"No, the Moon is not gaining energy. The Moon has it's initial energy and if you project the parameters to the future, the Moon-Earth equilibrium of forces goes to moon drifting away from earth's gravity. It's the same situation with Mars and Phobos. Phobos has less kinetic energy to keep it steady orbit around Mars, so it will crash eventually. "

1. The moon is gaining energy from the earth.
2. Project the parameters to the future?
3. Moon-Earth equilibrium of forces? Odd phrase.
4. Moon drifting away from the earth? (this is true but...) You just said the moon is not gaining energy, which is what would be required in order for the moon to drift away.
5. The Earth and moon are not in equilibrium. There are unbalanced forces and acceleration.

 

[sao123]

Originally posted by: silverpig

Originally posted by: AstroGuardian
Which paragraph?

This one:

"No, the Moon is not gaining energy. The Moon has it's initial energy and if you project the parameters to the future, the Moon-Earth equilibrium of forces goes to moon drifting away from earth's gravity. It's the same situation with Mars and Phobos. Phobos has less kinetic energy to keep it steady orbit around Mars, so it will crash eventually. "

1. The moon is gaining energy from the earth.
2. Project the parameters to the future?
3. Moon-Earth equilibrium of forces? Odd phrase.
4. Moon drifting away from the earth? (this is true but...) You just said the moon is not gaining energy, which is what would be required in order for the moon to drift away.
5. The Earth and moon are not in equilibrium. There are unbalanced forces and acceleration.

would not the earth/sun have this same relationship...

or moreover...

wouldnt jupiter/sun have this same effect, and why doesnt it eject the inner planets?

 

[silverpig]

Originally posted by: sao123

Originally posted by: silverpig

Originally posted by: AstroGuardian
Which paragraph?

This one:

"No, the Moon is not gaining energy. The Moon has it's initial energy and if you project the parameters to the future, the Moon-Earth equilibrium of forces goes to moon drifting away from earth's gravity. It's the same situation with Mars and Phobos. Phobos has less kinetic energy to keep it steady orbit around Mars, so it will crash eventually. "

1. The moon is gaining energy from the earth.
2. Project the parameters to the future?
3. Moon-Earth equilibrium of forces? Odd phrase.
4. Moon drifting away from the earth? (this is true but...) You just said the moon is not gaining energy, which is what would be required in order for the moon to drift away.
5. The Earth and moon are not in equilibrium. There are unbalanced forces and acceleration.

would not the earth/sun have this same relationship...

or moreover...

wouldnt jupiter/sun have this same effect, and why doesnt it eject the inner planets?

Yes they would and do, however due to the greater distances, the Earth has an almost negligible tidal effect on the sun. There are definitely resonances between the orbits of Earth and Jupiter that affect us (actually, I think Mars and Jupiter have a much stronger one). Mars and Jupiter have orbital resonances which bunch up asteroids into clouds, send them flying off etc...

See if you can google some info about it... orbital resonances of the planets or something like that. I'm at work and can't do it now but I'll look later myself

 

[JTsyo]

Originally posted by: silverpig

Yes they would and do, however due to the greater distances, the Earth has an almost negligible tidal effect on the sun. There are definitely resonances between the orbits of Earth and Jupiter that affect us (actually, I think Mars and Jupiter have a much stronger one). Mars and Jupiter have orbital resonances which bunch up asteroids into clouds, send them flying off etc...

See if you can google some info about it... orbital resonances of the planets or something like that. I'm at work and can't do it now but I'll look later myself

Something similar can be seen in the rings of the outer planets. The moons are called "shepherd moons" since they adjust the rings as they pass by.

 

[Biftheunderstudy]

The places where there are the strongest resonances with Jupiter's orbit are called the Kirkwood gaps. These are the semi major axis where you will find very few asteroids since the effect of an orbital resonance is to transfer angular momentum to the inner radius body thus eventually ejecting it from the system while moving the larger planet inwards. Though most likely due to bias in our detection schemes a lot of extrasolar planets have been found ridiculously close to their central star, the models predict this because a large planet will tend to kick the smaller planets out of the system until the only remaining planets are in the "safe" not resonant zones.
The Earth moon system is a tidal locking situation, there are a few other examples of this in our solar system. One of the moons of Jupiter (or Saturn I don't recall exactly) is tidally locked, another example is Mercury though its a bit more complicated because Mercury has a highly eccentric orbit.
I believe the correct response to the OP's question was brought up already, the solar wind is much much less than the orbital perturbations from the other planets, though I don't doubt someone like Tremaine has done a model of it.