What If the Earth's Orbit Was Changed?

[Boo75]

Hi there, I've got a theoretical question i was hoping to gauge opinion about:
Is there any feasible situation which could change the Earth's orbit (without obliterating all life in the process)? And if so what would you imagine the effects to be, say for example if the Earth were to move further away from the sun?
I'd be interested to hear anyone's thoughts
Thanks
Dan

 

[tony873004]

It depends on how large of a change.

Small forces are constantly changing Earth's orbit. But the Earth still stays within a certain range.

If a major change occurred in Earth's orbit, life would definitely have some adapting to do. But even if Earth were moved as far away as Mars, I imagine life would find a way to hold on. Obliterating all life is probably a difficult thing. Think of how hard it is to kill cockroaches.

 

[pervect]

If you could arrange a large enough number of properly managed encounters of the Earth with large enough crossing near-earth asteroids and comets, you could eventually alter it's orbit. How much, I don't know. The computational problems to do this with reasonable energy sources would be enormous. (Finding good candidates, and when and how much of a "nudge" to give each of them). You might also be able to set up some sort of system using large orbiting bodies which gradually transfers energy and angular momentum to the Earth from some other nearby planet.

 

[Boo75]

Thanks for your replies so far, very interesting...
I too immediately thought of external bodies; however then i began to wonder whether a change in the tilt of the Earth's angle (currently at 23.5 degrees?) would do the same. Say, and this is pure hypothesis, there was an internal explosion/avalance in the core mantle area which caused the angle of rotation to shift suddenly - would this be enough to drastically change the Earth's orbit? And if not, what would you suppose the effects would actually be?

 

[Astronuc]

A change in the angular momentum, i.e. Earth's tilt or rotation, or moon's orbit would affect perturbations of the Earth's orbit, but not much in the Earth's mean orbit.

Basically to make 'big' changes, the sun's mass or Earth's mass would have to significantly change, or a substantial change in the Earth's angular momentum about the sun would have to increase/decrease, which would ostensibly require a large mass passing close enough to the earth/solar system.

 

[LURCH]

I think that the Earth's orbit must be undergoing significant change even as we speak, but the change is so gradual as to be unnoticable, even on evolutionary timescales. The Sun completes one revolution every 11 hrs (roughly), but the Earth takes 365 days to complete an orbit. The discrepency between these periods should have a "breaking" effect on the Sun (with the gravitation between the two bodies as the break mechanism), by which effect the Sun's rotation must be slowing down, and the Earth's orbit speeding up. As the Earth's orbit accelerates, the planet must move into higher orbit, getting further and further away from the Sun.

This effect should eventually become quite profound, given the difference in the masses of the two bodies involved, but it's happening very slowly. Given time, our orbit should end up being many times more distant than it currently is, but the time required would be so great that the Sun will probably go Red Giant before it's increased more than a couple percent.

 

[tony873004]

But the Sun completes 1 revolution every 25 days, not 11 hours, or it wouldn't look round.

Is the mechanism you're describing the same as the one that causes the Moon to receed from Earth? The tide pulled by Earth on the Sun are many magnitudes weaker than the tides the Moon pulls on the Earth. It's obviously a non-zero number, but so small that over the course of Earth's lifetime I'd be surprised if it amounted to more than a few kilometers of drift.

 

[SpaceTiger]

Yeah, as I said in the other thread, the dominant deviations from a non-Keplerian orbit are planetary perturbations. They're easily determined in the short term, but because of chaotic behavior in the long term evolution of the solar system, we can't predict exactly what will happen on timescales greater than ~5 million years. We can say, statistically, that the orbit is probably stable on timescales greater than the lifetime of the sun. In other words, the sun will probably die before we see a major change in the Earth's orbit.

 

[LURCH]

But the Sun completes 1 revolution every 25 days, not 11 hours, or it wouldn't look round.

Ooops! You're right, I was thinking of Saturn .

Is the mechanism you're describing the same as the one that causes the Moon to receed from Earth? The tide pulled by Earth on the Sun are many magnitudes weaker than the tides the Moon pulls on the Earth. It's obviously a non-zero number, but so small that over the course of Earth's lifetime I'd be surprised if it amounted to more than a few kilometers of drift.

Yes, tidal locking. And I agree, it won't amount to much during the lifetime of our system.

 

[Andre]

..i began to wonder whether a change in the tilt of the Earth's angle (currently at 23.5 degrees?) would do the same. Say, and this is pure hypothesis, there was an internal explosion/avalance in the core mantle area which caused the angle of rotation to shift suddenly - would this be enough to drastically change the Earth's orbit? And if not, what would you suppose the effects would actually be?

How would you fancy that? Since the (angular) momentum in a closed system is constant, any change in a part of the system needs to be offset with a counter reaction.

However, as the Earth experiences complicated pertubations due to external forces they may or may not act differently on the Earth core spin axis in comparison to the mantle spin axis. This could result in very interesting secundary effects.

 

[Boo75]

Quite!
It's the interesting effects I'm hoping to discuss
As before thanks to anyone who has contributed to this thread...

 

[Andre]

Some ideas about interesting effects concerning gravity induced differential precession of spin axes:

https://www.physicsforums.com/showthread.php?t=2974