Could artificial gravity be dangerous?

[Urge]

If forexample a space-ship or peace of plating creates 1 G, and this have a long range (similar to natural gravitational fields), wont it come with the danger of pulling things out of orbit? Or attracting rocks and gravel flying through space? It would be bad if the Enterprise pulled with it Earth when leaving space-dock, or doubled its gravitational field while in orbit, causing - among other things - Earth and the Enterprise to revolve around each other.

The same goes for experiments with artificial gravity. If one suceeds there is a risk of messing up the natural order of things.

Have scientists thought about these problems? That we need to be very careful with artificial gravity experiments?

 

[ProtoAvatar]

Urge

You really need not worry about scientist not being "careful with artificial gravity experiments" or about the potential dangers posed by artificial gravity.

That's like the ancient greeks worying about their philosophers/scientists building an atomic bomb.

We don't even have a theoretical fundament, an ideea where to start in generating artificial gravity fields with less than astronomic amounts of energy (and by astronomical, I mean impossible to obtain).

 

[Christopher]

If forexample a space-ship or peace of plating creates 1 G, and this have a long range (similar to natural gravitational fields), wont it come with the danger of pulling things out of orbit? Or attracting rocks and gravel flying through space? It would be bad if the Enterprise pulled with it Earth when leaving space-dock, or doubled its gravitational field while in orbit, causing - among other things - Earth and the Enterprise to revolve around each other.

The key thing to remember is that the gravity you feel is proportional to your distance from the center of mass, and drops off as the inverse square of the distance. We feel a pull of 1 g at a distance of approximately 6380 kilometers from the Earth's center of mass. On a spaceship, you'd be at most a few hundred meters from the gravity generator. Call it, say, 64 meters, and that's 0.00001 times the distance to the center of mass. So by the inverse square law, the gravitational field would only need to be 0.0000000001 times as strong as the Earth's in order for the crew at 64 meters' distance to feel a pull of 1 g.

Also, that weaker field would drop off quickly with distance. Let's simplify it a bit more and assume you feel 1 g at 100 meters' distance from the gravity generator (making it a slightly more powerful field than in the previous example). If you were 200 meters away, you'd feel 1/4 g. If you were 1 kilometer away, you'd feel 0.01 g. At 10 km distance, you'd feel 0.0001 g. And so on.

So no, if a spaceship generated its own artificial gravity, it wouldn't pose any significant hazard to other ships. The field strength would drop off too quickly with distance. The only case where it would be a potential hazard is if two ships are docking with one another.

Of course, most fictional artficial gravity avoids this by adopting the rather nonsensical conceit that the hull of a spaceship is somehow opaque to gravity, so that you can be immediately outside and above the ship and be in weightlessness. Sometimes I think TV and movie writers must think gravity is transmitted by atmosphere.

Star Trek and others also often assume that the gravity generators are directly in the floor of each deck, which would have some bizarre inverse-square effects, since your feet would be subject to much stronger gravity than your head. Let's see, if we assume the effective center of mass of a "gravity plate" within a ship's deck is, say, 20 cm below your feet, and you're 180 cm tall, then the top of your head should feel only 1 percent as much gravity as your feet do. This is another basic physical principle that's routinely ignored in fictional portrayals of artificial gravity.

 

[Trekker4747]

It's possible that however the gravity generators in these ships works these various effects are accounted for and negated... "somehow."

For all we know the "gravity plating" is nothing more than very low level tractor beams that creates gravity but doesn't effect adjacent decks (above or below) or effects objects outside of the ship.

As to the topic at hand. Let us first assume there's "someway" to "make gravity" using technology and that this gravity is as useful, functional and has the same effects as "natural gravity."

In theory, as I understand it, it does -and could- cause problems. But nothing to overly concern oneself with.

Take something like Relativity for example. According to relativity your proximity to a massive object and your speed of movement all effects how you experience time as opposed to a person under different circumstances.

When I'm in my car going down the highway at 80 miles an hour I'm aging slower than someone standing on the road. When I'm standing at the top of a mountain I'm aging slower than someone at the bottom of the mountain. Speed and proximity to gravity (or any mass for that matter) effects how one experiences time. But the differences in both of these instances would only amount to nanoseconds over the course of a lifetime as they're small speeds/masses compared to what you'd need to be at to effect things.

If you were traveling at or near c or near a black-hole the differences would be much more noticeable.

In all reality the tiny bit of gravity the moon is acting on the Earth is slowing both down due to gravitational drag. The moon is pulling the Earth towards it! In theory the the immeasurable amount of Earth's gravity felt on the side of the galaxy is having "an effect." So, yes, if our gravity generator worked much in the same way it would have an effect. But no real effect to worry about.

 

[Christopher]

It's possible that however the gravity generators in these ships works these various effects are accounted for and negated... "somehow."

Well, this is the Science and Technology forum, not a science fiction forum. So our focus here should be on the real science and the real possibilities, not on fictional "somehows" and handwaves. We're not here to twist and ignore science in order to rationalize fiction, we're here to explore and explain science, and to acknowledge where fiction falls short or is simply wrong.

For all we know the "gravity plating" is nothing more than very low level tractor beams that creates gravity but doesn't effect adjacent decks (above or below) or effects objects outside of the ship.

Well, that doesn't entirely make sense, because it contains two contradictory assertions. If we assume that a tractor beam is essentially a graviton laser or some other directionally applied force, then like a laser it would not be subject to the inverse square law (because it propagates linearly rather than spherically) and thus would not decrease in intensity with distance, except through scattering. So that would resolve the problem of the severe tidal differential between one's head and feet. But since it wouldn't decrease with distance, and since there's no such thing as matter that's opaque to gravitation, such a graviton laser would definitely be felt far beyond the deck in question and far beyond the outer hull of the ship.

Conversely, the only way to have a gravitational or otherwise attractive effect that is not felt beyond a single deck is to have it drop off quickly enough that its effect becomes negligible more than about 3 meters away from the source. And that requires a sharp dropoff in intensity which would have to be exponential, so again you get the severe tidal differential from head to foot. And that pretty much rules out the idea of the attractive principle being some form of directional beam.

So you can't have it both ways. Either it's a beam or it's localized; it can't be both.

Well, unless it's a diamagnetic field of some sort, similar to the diamagnetic levitation effect but in reverse. Unlike gravitation, an electromagnetic field can be blocked or shielded and thus confined to a particular volume. However, it's unclear whether such a field would be safe for long-term human occupancy; even if there's no physiological risk, strong magnetic fields have been shown to induce hallucinations, paralysis, paranoia, and other neurological effects in some cases. Also there's the question of what effect such powerful fields would have on the ship's computers and electronics. And there'd probably have to be a complete lack of loose metal of any kind within the ship, as with an MRI room.

For the purposes of one of my Star Trek novels, I postulated that Starfleet gravity plating generates virtual gravitons calibrated to last for only enough time to travel about 3 meters (i.e. about 10^-8 seconds) before ceasing to exist. I claimed this was so that the artificial gravity wouldn't interfere with the warp field. But that's a handwave to rationalize something I was stuck with in the fiction. If we're discussing the topic of artificial gravity in terms of real science, it's not an idea that has a lot of credibility. Personally I'd love to see an SF treatment of artificial gravity that treats the physics of gravitation more realistically.

Take something like Relativity for example. According to relativity your proximity to a massive object and your speed of movement all effects how you experience time as opposed to a person under different circumstances.

When I'm in my car going down the highway at 80 miles an hour I'm aging slower than someone standing on the road.

Well, unless you're driving westward, against the direction of the Earth's rotation. Then you're actually moving nearly 8 percent slower than that other person. (At least until you get into an accident and die because you were reckless enough to go 80 miles per hour.)

When I'm standing at the top of a mountain I'm aging slower than someone at the bottom of the mountain.

Other way around. The deeper you are in the gravity well, the slower your perception of time relative to an observer in flat space.

 

[sojourner]

^I think on that last point he was going for the fact that the person on the top of the mountain is at a greater radius from the center of the earth and thus moving faster as the planet rotates than the person on flat ground, disregarding gravity.

 

[Itisnotlogical]

I don't think that a gravity field just strong enough to keep your feet on the ground would be enough to pull Earth out of it's natural orbit, which has been exactly the same since time immemorial. The only danger I see in artificial gravity is if a guy leans on the switch, and suddenly everyone's crushed flat against the deck.

 

[sojourner]

Yeah, at worst you still have mass to deal with. The ship, being the much smaller mass, would essentially pull itself to the surface of the planet.

 

[Asbo Zaprudder]

From TV and movie sci-fi, the main danger of artificial gravity appears to be the same as on Earth: falling from great heights (Cargo) and being crushed by falling objects (Worf).

I doubt that the effective field radius of gravity plating (how that would be generated I have no idea) would be anything like the Earth's. I guess it would be kind of an analagous situation to magnetism: a bar magnet in your hand locally has a much stronger field than the earth's, yet the earth's field extends over a much greater distance and can deflect the solar wind. It's not quite analagous as I vaguely recall that a magnetic dipole's strength falls as the inverse cube of distance whereas gravitational attraction falls off as the inverse square.

For artifical gravity created by rotation, I expect there'd also be the danger of accidentally getting swatted by the rotating ship section or getting crushed in the gearing (a movie favourite).

 

[Deckerd]

Swatted? You mean if someone's spacewalking?

Another idea I had was getting hold of very dense material similar to what is found in collapsed stars. If you had some way of harnessing that, or even encasing it, you could either use it beneath a vessel if it were a conventional ship with flat levels or you could build a Death Star round it.

 

[ProtoAvatar]

Swatted? You mean if someone's spacewalking?

Another idea I had was getting hold of very dense material similar to what is found in collapsed stars. If you had some way of harnessing that, or even encasing it, you could either use it beneath a vessel if it were a conventional ship with flat levels or you could build a Death Star round it.

This might solve the artificial gravity problem.
But you're left with the mich bigger problem of actually moving this collapsed matter and its enormous mass with the rest of the vessel.

 

[Asbo Zaprudder]

Swatted? You mean if someone's spacewalking?

Or like Sheridan in Babylon 5, you get propelled from the 0G centre towards the "floor" of the habitat, which is moving sideways at high speed relative to you.

Another idea I had was getting hold of very dense material similar to what is found in collapsed stars. If you had some way of harnessing that, or even encasing it, you could either use it beneath a vessel if it were a conventional ship with flat levels or you could build a Death Star round it.

Trouble would be to stop it changing state explosively. You'd need a binding medium. Robert L Forward suggested diamond but that poses problems all in itself, not to mention that you've now got to propel a huge extra mass around.

 

[Deckerd]

Getting it moving and stopping it would be the biggest problems.

 

[Asbo Zaprudder]

Getting it moving and stopping it would be the biggest problems.

Yep, inertial mass is as difficult a problem to overcome as to generate an artificial gravitational field by a means other than linear or rotational acceleration would be.

 

[Deckerd]

The most obvious course of action would be to get it into a solar orbit and then leave it there. Of course this doesn't help anyone wanting a vessel that can roam around but it would make a useful hub.

 

[Lindley]

Getting it moving and stopping it would be the biggest problems.

Yep, inertial mass is as difficult a problem to overcome as to generate an artificial gravitational field by a means other than linear or rotational acceleration would be.

Well, if you could find a fuel source with enough endurance you give you constant linear acceleration until turnover at the midpoint, then you've solved two problems at once: gravity and speed.

 

[iguana_tonante]

Have scientists thought about these problems? That we need to be very careful with artificial gravity experiments?

Don't worry, we will be.

Now keep calm and carry on.

 

[Trekker4747]

Other way around. The deeper you are in the gravity well, the slower your perception of time relative to an observer in flat space.

I thought I had mixed that one up.

Still, things like gravity and speed effect one's perception of time as opposed to people with different speeds/proximity to gravity.

And, in essence, everything generates a gravity well. It's just a matter of how strong it is. And it takes a large, planetary, or star-sized object with massive mass to even begin to noticeably change the perception of time in meaningful manner and it takes something super-massive like a black-hole to even effect it in any useful manner.

So while creating a gravity-generating device on earth would have in effect on everyone on the planet and even on everything in the universe it's effect isn't anything to really worry about.

 

[Asbo Zaprudder]

Getting it moving and stopping it would be the biggest problems.

Yep, inertial mass is as difficult a problem to overcome as to generate an artificial gravitational field by a means other than linear or rotational acceleration would be.

Well, if you could find a fuel source with enough endurance you give you constant linear acceleration until turnover at the midpoint, then you've solved two problems at once: gravity and speed.

Very true -- that's probably the best solution. However, I'm not aware we're anywhere near having a viable propulsion technology yet that will produce an acceleration anywhere near a substantial fraction of 1G for sustained periods of time. Dropping mini-nukes out the back end (in the manner of the original Orion Project) would do the trick but that seems to be unacceptable.

 

[Deckerd]

I'm prepared to bet the technology for propulsion will arrive sooner than a superdense gravity source to helpfully manifest itself in the vicinity of our solar system.