Effects of Moving a Planet

[Crossroads Inc.]

Ok first off in the realms of Sci FI, moving big things have been quite common. In the Xeelee sequance, uncounted stars where moved with ease to make "The Ring" And in Ringworld, shoot, it was supposed to be able to use the energy from its star to push the whole thing through hyperspace or somesuch. So moving "just" a planet shouldn't be that big.

But what would it do to the planet? I am thinking of a short story that would have a moving planet, either through a form of warp or through wormholes. But what happens to a planet when its pulled from the gravity well of one sun and dropped into another? Or what if it is between stars and just on its own? How would the changes in gravity affect it?

[Junghalli]

The main effect of the sun's gravity on Earth's structure is IIRC the solar tide, which is less than 1/2 the strength of the lunar tide. This solar tide IIRC creates bulges in the oceans, atmosphere, and solid body of the Earth (small ones IIRC - meters for the ocean, much less for the solid body) at the points facing toward and away from the sun. If the sun were magically taken away, you'd have a redistribution of solid body and water away from these points - I imagine probably much faster than the natural solar tide, since that part of the world isn't slowly turning away from the sun's gravity like when the tide naturally goes out, the sun's gravity is just gone.

I rather doubt this would have any significant effect (e.g. earthquakes due to the sudden settling of the land) at all, although I'm not really confident in saying that for certain.

If the Earth were magically moved into orbit of a different star it becomes more complicated since a lot depends on the new star and the new orbit. If the Earth is to not have its velocity changed and remain habitable and with a minimum of climatic disruptions then it's probably relatively safe to assume the new star is quite similar in mass to the present sun (because it needs to recieve roughly the same sunlight in its present orbit), which should minimize the effects. Basically, there may be a slight change in the solar tides, and if the Earth isn't facing the same side to the new sun that it was to the old then there may again be a sudden redistribution of land and water as the focus of the solar tide is suddenly changed.

[Phantasee]

What about the Puppeteer's taking their planets on a long trip to wherever the fuck they were going? How would that work? AFAIK they didn't have a sun with them, they just put the population planets and the agriculture planets together and took off.

[Junghalli]

What about the Puppeteer's taking their planets on a long trip to wherever the fuck they were going? How would that work? AFAIK they didn't have a sun with them, they just put the population planets and the agriculture planets together and took off.

As far as gravitational effects go the big issue with moving a planet is that accelerational gravity will be trying to pull the planet out of its spherical shape. I imagine this could easily do very bad things to its surface environment. This can be reduced by doing very gentle acceleration, which you'd probably be doing anyway simply because of the ridiculous power needed to move a planet at all.

There's also the waste heat the necessary engines would be generating and the massive amounts of propellant they'd need, but those are somewhat outside the OP.

As far as the Puppeteers, having recently read Juggler Of Worlds the "planetary drives" they use were bought from the Outsiders and the Puppeteers themselves do not seem to fully understand them. There's no mention of propellant or gravitational effects, although there is mention of them needing huge amounts of energy - I think it's reasonably safe to think they're probably something like giant gravity polarizers. That would be the system that creates the least problems.

Edit: reading my last reply I think I should clarify that when I said "sudden redistribution of land and water" at the end I meant the oceans going down/up a few meters or less and the land much less - not something horrendously catastrophic like that may sound like.

[Freefall]

The general effects of moving a planet are going to depend on how fast you're trying to move it. Since the Earth is pretty gooey on the inside, and it's got a lot of inertia, trying something like pushing it from the "back" at any appreciable speed is probably going to make it deform and cause quite a lot of magma to start bursting out all over the crust. This is why I have to roll my eyes at DC whenever they have Superman push planets (especially the earth) around.

And from what I remember, it doesn't take much of a total velocity for the energy needed to move the earth out of orbit to exceed its GBE, so you're definitely going to want to ease it out.

In regards to a wormhole, I would be concerned about tidal forces distorting (or destroying) the planet, since one end of the planet would obviously enter the wormhole well in advance of the other, and if these are the kind of wormholes that involve a kind of "sucking" force, then this is obviously problematic. Of course, you'd also need a planet sized wormhole, and a civilization can create something like that, then "compensating" (gotta love throwaway nonsense like that) for any negative effects could be well within their abilities.

Warp I think would also depend on exactly how you see it working. If we're talking Trek style, then I think you'd need a planetary deflector field, structural integrity field, and inertial dampers. I mean, even the Enterprise is threatened by tearing itself apart at warp when those systems start failing, and you've to got to figure it will be a much bigger deal for a planet.

As far as generally just removing it from it's parent star, I think the effects will be mostly tidal, like Junghali pointed out. For earth in particular, I think removing it from the moon would be much more serious, as far as gravitational effects go. Planets closer to their parent star will be more strongly affected, planets further away less so. If earth had no moon and were cut loose from the sun, from a gravitational standpoint, I don't think it would be the end of the world or anything (the lack of sunlight would be a much bigger deal).

[someone_else]

I would use an artifical gravity well (-insert magitech-) to push it around (a pretty big one, since it must have a big enough mass to stay at enough range to have insignificant tidal effects on the planet. Otherwise you just tear it apart).
Then you can apply whatever the fuck of acceleration you want, since the gravity from the artificial gravity well will be so close to unidirectional and change so little from planet's side A to planet's side B to have no harmful tidal effect on it.
Now, how to calculate the mass and distance needed for something like that is another matter. Much above me.

As of moving planets around, there is something interesting I can say:
You will screw up both system's orbits, since now the gravity pull of Planet A1 in System A won't be felt anymore by planet A2, A3, and so on. That may, over ludicrously long timescales, break the system and slingshot planets in deep space.

The same goes for adding a planet. Now there is one more gravity well that interacts with others, potentially doing the same.

Obviously the effect with something relatively small as the Earth shouldn't be a big issue, but when you move a gas giant...

If you have a planet-moving tool, you can easily fix that, but orbits will have to be rearranged a little to find a new equilibrium.

[Junghalli]

Since the Earth is pretty gooey on the inside, and it's got a lot of inertia, trying something like pushing it from the "back" at any appreciable speed is probably going to make it deform and cause quite a lot of magma to start bursting out all over the crust.

IIRC the idea that the Earth is like an egg with a thin crust of solid rock over a lava ocean is actually a misconception - the mantle is basically solid and only acts like a liquid over very long timescales (the stuff that comes out of volcanoes is solid rock that liquifies as it rises and the pressure is reduced). At any rate if the force wasn't being distributed well into the planet I'd think the most likely result is the rockets would drive themselves into the ground. I think the bigger problem lies with the fact that the Earth is much too big to hold itself in a solid shape against gravity. That's why it's a sphere. Imagine if you magically reshaped it into an egg shape. The ends of the egg would be mountains thousands of miles tall - and they'd collapse instantly under their own weight.

The problem is if it starts accelerating at a significant rate it's effectively in the same situation - it's a sphere where gravity wants to pull it into - uh, I'm not sure exactly, a pancake? The matter of the Earth will start to flow, probably doing terribad things to the surface. For starters the oceans are much more responsive to this sort of forces than the solid body, so even forces that don't effect the solid body's shape too much will start the oceans flowing to one side of the planet...

In regards to a wormhole, I would be concerned about tidal forces distorting (or destroying) the planet, since one end of the planet would obviously enter the wormhole well in advance of the other, and if these are the kind of wormholes that involve a kind of "sucking" force, then this is obviously problematic. Of course, you'd also need a planet sized wormhole, and a civilization can create something like that, then "compensating" (gotta love throwaway nonsense like that) for any negative effects could be well within their abilities.

Warp I think would also depend on exactly how you see it working. If we're talking Trek style, then I think you'd need a planetary deflector field, structural integrity field, and inertial dampers. I mean, even the Enterprise is threatened by tearing itself apart at warp when those systems start failing, and you've to got to figure it will be a much bigger deal for a planet.

If we're talking science-fictional interpretations of "warp" or "wormholes" (as opposed to theoretical physics versions) then it's basically magic and its properties are arbitrary. Just give it whatever properties are convenient for the story.

I would use an artifical gravity well (-insert magitech-) to push it around (a pretty big one, since it must have a big enough mass to stay at enough range to have insignificant tidal effects on the planet. Otherwise you just tear it apart).
Then you can apply whatever the fuck of acceleration you want, since the gravity from the artificial gravity well will be so close to unidirectional and change so little from planet's side A to planet's side B to have no harmful tidal effect on it.

This sounds rather similar to a gravity tug.

[someone_else]

This sounds rather similar to a gravity tug.

Well, it is a gravity tug . It just relies on magitech to create and move the gravity well that pulls the planet.

[Uncluttered]

You can do it if you transfer the orbital energy from Jupiter to Earth with an orbiting stream of asteroids.

It's slow, and probably doesn't answer your question fully.

Link: http://arxiv.org/abs/astro-ph/0102126