How can a spaceship unknowingly interfere with tides on a planet?

Someone left the artificial gravity on.

The Alcubierre drive works by manipulating space-time so that you ride a 'wave' of gravity forward at any speed. You might use this same technology to create a more static artificial gravity over a given area.

When in deep space, your ship can produce artificial gravity by emulating a large mass some distance below the ship, and letting otherwise-natural gravity take over from there. The mass of our own moon is about 7*10^22 kg. To get 1 g from that naturally, you'd need to place the mass 162 miles below the ship. This is really the furthest you'd need to put it: The mass and distance would be much lower if the ship were closer to the planet than our own moon is, or if the tides don't need to be as strong. You could either make this place of artificial mass be something like a point mass (a tiny black hole) which might be visible and have little particles streaking around it, or something subtler, like an even density field over a sphere or other shape. If you want the center of mass to be contained within the ship instead of below it, you can have it malfunction so that the gravity is stronger outside the ship instead of inside, like it should be.

Normally this gravity is switched to a local-only mode (it uses significantly more energy, but creates a gravity effect limited to the ship) when you approach a planet or another ship to avoid dangerous interference, but due to a malfunction or mistake, it was left on this time.

The sudden introduction of this gravity source will slowly begin affecting the tides, and when they realize it's happening they can get it fixed. It will also pull the other moons and planet, but you can engineer it so that this is a negligible or significant thing, based on whether the ship is nearer to the planet or the moons.

posted almost 10 years ago

Tim S.‭

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Quite simply, you can't.

The key part here is "unknowingly". If you have a structure large enough (simply massive) or advanced enough (gravity shields or internal gravity or something) to actually interfere with the tides, then it is undoubtedly being piloted by a very advanced species that has a full understanding of tides and is aware of the effects on a planet.

Our incredibly primitive culture had a keen knowledge of the tides for thousands of years, despite having the ability to reach space for a couple dozen. By the time a species has the ability to build a structure advanced enough to effect tides, they will have mastered the simulation capabilities far beyond what is necessary to account for tidal forces.

Whether or not they care is an entirely different matter.

posted almost 10 years ago

corsiKa‭

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The other answers have, unfortunately, all been too kind. You cannot affect the tides in any sort of spaceship of non-ridiculous size, you cannot move a spaceship of ridiculous size, and the technical demands for hypothetical singularity-based drives are (in addition to not being widely accepted as consistent with modern physics) so far past what we have now that there's no credible path there from "earth today".

However, very much science fiction is written without a credible path from "earth today", or in blatant contradiction with physics. So don't let that stop you! It just makes the science fiction a bit less hard.

Anyway, the thing to realize about tides is that the forces involved are immense. The tides dissipate 3-4 TW of energy on the Earth, or about 1/4 of the total power usage of all humans on the planet. Accidentally imparting anywhere near that much energy to a planetary system seems hard to do unawares (only really possible with antimatter-based energy sources; you would need to waste an extra gram of antimatter per three minutes to equal the tidal dissipation on Earth). Doing so via something other than gravity (which is extraordinarily hard to manipulate) without causing huge visible effects also seems unlikely.

The bottom line is that orbiting in a spaceship is a pretty low-impact activity, while changing tides is a big one. It would be more plausible if one of the premises were changed (e.g. one of the moons is actually the spaceship, and they are maneuvering it to begin a million-year journey to a different solar system; or the spaceship isn't there just to quietly observe but to perform massive resource extraction, which they think they can manage by huge-scale seafloor mining with drones, which is largely true except for the (gradual) change on the tides).

posted almost 10 years ago

Rex Kerr‭

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I can think of two uses for gravity generation aboard a spacecraft. The first is environmental, keeping crew and components from floating around while the ship is outside of a planet's gravity well. The second is locomotion, some form of space/time warping device. The environmental system would probably be too weak and localized to fit your needs, unless the ship was truly massive (in which case its own mass might serve your purposes).
The propulsion system would probably be much too strong when engaged. Altering planetary orbits is not your goal... you just want to move a little water. So that leaves the propulsion system at rest. Perhaps, as well behaved explorers, your humans turned off their warp drive well outside of the solar system and have drifted in using more conventional propulsion. But even with these precautions, the warp drive itself, even when turned off, emits a powerful field, approximating the strength and scope of a small moon. The environmental system would therefore serve two purposes... keeping the crew's feet on the ground and helping them resist the gravity of their engine.

As for any of this being feasible, given what we know about gravity, I am not qualified to say. As far as I know, we can feel gravity, measure it, depend on it and even occasionally defy it... but we have yet to figure out how to create it sans planetary masses.

posted almost 10 years ago

Henry Taylor‭

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Since moons affect tidal patterns on planets using gravity; I would say that's what we would have to focus on as a spaceships only means to affect tides on a distant planetary body.

Obviously, a single spaceship shouldn't have the same gravity as a moon. But let's take it a step further.

As we all know by now, the idea of "warp drive" has been a seriously considered form of FTL travel. Since your story will have a human spaceship visiting a distant planet, it would only make sense that there is some form of FTL travel (like warp drive?) available in your universe/timeline.

So let's take it a step further. Since warp drive relies on manipulating large amounts of gravitational force to manipulate space-time; maybe the spaceship could be have an early version of warp drive that didn't have all the "kinks" worked out yet.

Maybe the spaceship has to charge "gravity" up before it's ready for a warp jump to the next star system or galaxy!?

EDIT*** The "obviously" part may have been a bit misleading. So let me lay out my reasoning for that statement based on the following assumptions:

For a spaceship to be large enough to affect the tidal patterns of a distant planet (the distance, of course, would be dictated by the gravitational pull of the and the distance the object was from the planet) it would require that the spaceship to be the same mass as a moon! That would seem to be pretty huge.

Even if, the civilization was advanced enough to build a structure/spaceship that large. There are many reasons to not build ships so large for the sake of efficiency. First of all, newtons laws of force and motion would still apply to an object in space. Therefor, the greater the mass of the object they are moving (propelling the spaceship would require more energy to move a large spaceship than a small one; not to mention how much more it would take when approaching the speed of light).

posted almost 10 years ago

Get-HomeByFiveOClock‭

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Too long for a comment.

TL;DR Whatever you do, that effect has to be pretty strong.

Explanation: If you have three moons, the tides (depending on the moons' trajectories) might be very chaotic, nowhere near the pre-industrial capabilities of tidal forecasts. We have several possibilities:

1. Somehow, the tides were very important and that one domain was much more developed than any other.
2. The forecasts are rather coarse.
3. The forecasts are done only for places which have physical properties that make the flow easy to predict.
4. They don't use forecasts, only observe the tides after the fact.

With each of these there are some problems:

1. Flow dynamics (including resonating systems) is one really hard domain that we still work on. I think it's highly improbable for them to be able to do accurate tidal forecasts. But hey, it's your story. If you want to follow this path, perhaps you could have placed (a few hundreds years before the actual story is set?) some out-of-their-time character (crashed spaceship?) with only one survivor who had taught them how to calculate the right numbers for their planet.
2. The effect of the spaceship has to be visible over the chaos and their coarse tidal forecasts. Any such effect would influence other things (perhaps more noticable).
3. The effect has to get through the thing that makes the tides predictable. Similarly, any such effect would influence other things.
4. Knowing what should have happen is easier, but still rather hard. As the tides were chaotic to begin with, when something unpredictable happens it would be most likely taken as "oh bother, what we though isn't quite right, there some new factor we missed...". It takes a whole new level of reasoning to arrive at "our results were quite good, but diverged, however, our current results are still consistent if we would assume this new huge blob of mass somewhere here near our planet...".

I hope this helps $\ddot\smile$

posted almost 10 years ago

dtldarek‭

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If the effects of the tides are significant, and the spaceship inhabitants are observing the planet, it's likely that they would know that they are influencing the tides of the planet. However, if they're on some sort of commercial mission, rather than a "don't interfere/we come in peace" mission, it's highly likely that they may just not care. If that's the case, then there are numerous things that a spaceship could do that might affect the tides of the planet. Here are some examples:

The spaceship could be really big

A spaceship big enough to affect the tides would act like another moon, though tidal effects would be more variable/random if the spaceship was moving around. In this case, the spaceship would probably be visible from the planet, though cloaking fields etc. could negate this. Effects on the tides wouldn't come all at once, but rather would be a steady shift towards a new tidal equilibrium. Tides are a resonance phenomena, so it will take a few days/weeks for the tides to shift into the new pattern.

The spaceship could produce artificial gravity

Things like Alcubierre drives rely on warping space, which would likely affect the tides. Since this would be a less constant effect, it would probably cause something more like a tidal wave than a consistent change in tides. There would be a consistent effect if the spacecraft was using artificial gravity to stay at a certain non-natural orbit. For example, if a spacecraft wanted to be in a geosynchronous orbit, but at a low altitude, the craft could do this by reducing the effect of gravity from the planet on the ship. If this reduction in gravity affected the ocean under the planet, it would cause tidal effects.

The spacecraft might need to either dump things into the ocean or suck up water

A huge craft spending a few days/weeks replenishing internal water supplies by sucking up water would definitely cause tidal effects if it was using something like a gravitational tractor beam to do so. Likewise, a spaceship dumping all of its garbage would cause huge tidal waves. If they were cleaning out some internal holds by sucking up and dumping water repeatedly, this could cause alternating super low tides and tidal waves, along with massively disrupting currents on the planet.

All of these things would be very noticeable for the people in the spaceship, but they might not care. They may also not be paying any attention to the significance of changing the tides on the planet for the people below. Consider the effects of oil prospecting in the rain forest on the natives living there. The prospectors aren't really unaware of what their presence does, but they don'r necessarily think or care about the consequences. I could definitely see a space faring nation having similar attitudes towards a pre-industrial culture.

posted almost 10 years ago

ckersch‭

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All the answers so far dealt with the ship creating gravity itself. But there's another possibility: The ship might have some sort of gravity shields (to allow to pass close nearby heavy objects like neutron stars or black holes during travel without the ship being damaged), and they might have forgotten to switch them off after arrival. Now every time they pass between one of the moons and the planet, they disturb that moon's gravity (by shielding parts of the planet from it), and thus interfere with the tides.

So, how plausible are gravity shields? Well, at least not less plausible than artificial gravitation or Alcubierre drives. There's the claim by Podklednov to have observed such an effect. There's no independent verification and great doubts about it, so this is far from accepted science, but at least it's more than we have for artificial gravity, where I'm not aware of even a claim of observation. If Podkletnov is right, a gravity shield would be made of rotating superconductors.

posted almost 10 years ago

celtschk‭

341 reputation 24 102 42 10

Somebody left the tractor beam on or a control system accidentally malfunctioned activating the tractor beam. While this comes close to magical space technology effectively every other answer to this question invokes one form of magic space technology (Charles Stross TM) or other. This concept is modest by comparison, apart from the ludicrous energy requirements which have been discussed in at least one answer, with hurricane-force handwaving in the other answers. Mine is a gentle breeze in contrast.

No-one seems to have considered the possibility of a quantum gravity space-drive inadvertently leaking excess gravitons into nearby space. That could make it look like there was a new moon. if they have interstellar travel, there is every reason to expect science will solved the problem of quantum gravity and developed technology based on it. What better technology than a space-drive.

posted over 8 years ago

a4android‭

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