[Discussion] Contragravity

[rhoenix]

Alright, the purpose of this thread is for this idea to be dissected as thoroughly as possible, so that I may better incorporate it (or not) into my current story.

I've posted a few articles regarding gravity before, in an effort to see if such a concept of contragravity (reducing the effective mass of a starship), or artificial gravity (so you don't have to spin the habitation quarters to get "up and "down") is effectively still handwavium, or if it would perch barely on the border of hard sci-fi now.

However, with the assumption that it is (at least somewhat) hard sci-fi, I'll continue with the questions. If I'm incorrect about the two concepts being hard sci-fi, well...I'd still like to see where this goes, for the sake of argument and dissection of the concepts.

According to the ol' Rocket, reaction STL (slower than light) drives must carry a commesurate amount of fuel for the mass of the ship. So, with a concept such as contragravity, wherein the effective mass of the ship is reduced (say, for the sake of argument) to 1/10th it's original mass, would that be just as straightforward a calculation of fuel to weight, given no other environmental concerns?

Second question: If the concepts of contragravity and artifical gravity would exist, would it be a logical extension to say that a gravity-based focused beam could be used as an effective tractor beam?

[Covenant]

You know, it doesn't need to be hard sci-fi to fake gravity effects on a ship. You can get false gravity through acceleration. It just won't be shaped like a boat, it'll be shaped like a rocket. There's really nothing wrong with that.

Also, you're looking at this wrong. What you need is Mass Lightening, not contragravity. You're confusing the ship's mass with it's weight. The ship, out in the dead of space, is really not working under an awful lot of gravity effects, so removing it further from gravity won't really accomplish much. However, even a gravity-less system has mass, which is what dictates inertia. Where Contragravity would be good is for getting out into orbit from the ground.

Mass lightening involves a lot of other funky shit, so you're better off making some well-formulated handwavium and combining it with existing things to make an internally consistant use of sci-fi. Honestly, I know we all want to be as realistic as possible, but you don't need to cut the fiction completely out of it.

And honestly, I'm not sure what would happen to a crew once their atoms no longer had the proper mass. It might be extremely bad.

Also, what do you mean by 'focused gravity'? How would such a thing even exist?

[Admiral Valdemar]

And honestly, I'm not sure what would happen to a crew once their atoms no longer had the proper mass. It might be extremely bad.

Also, what do you mean by 'focused gravity'? How would such a thing even exist?

The effects of reduced inertia means certain biological functions become harder to maintain. The Conjoiners in the Revelation Space series used inertia suppression via a Higgs field manipulation to make a percentage of their ship's mass vanish, the field was subject to the inverse square law and so from its source at the rear of the vessel away from the crew quarters, it could make the drives and other heavy machinery less massive, as it were. A ship that could only go one gee could then go up to doing nearly ten gees, with humans being assisted mechanically though.

The extreme events that could happen if the machinery went wrong would include a person being slammed into a wall at several kilometres a second over the course of a couple of metres, causing a huge detonation.

Anyway, when I think contragravity or anti-gravity, these are really the technologies used to make non-aerodynamic surface or rocket based landings on planets possible, since you essentially negate gravity via some unknown property (basically pissing on conservation of energy).

[Admiral Valdemar]

I'm holding back on mass manipulation until CERN or Fermilab find out just what the Higgs boson is like and whether any new physics comes with it. If the vacuum fluctuation idea for momentum is correct too, then it could lead to possible ways to lower this effect, but I'm not holding my breath. Least, not for centuries anyway when it may actually be possible to explore such concepts.

Anti-gravity, though, is simply undoable.

[RedImperator]

Anti-gravity, artificial gravity, and focused gravity all live in the same place FTL and space fighters do. You can write hard sci-fi or you can write sci-fi with gravity manipulation. Not both.

[Admiral Valdemar]

Anti-gravity, artificial gravity, and focused gravity all live in the same place FTL and space fighters do. You can write hard sci-fi or you can write sci-fi with gravity manipulation. Not both.

That's why Reynolds used only the idea of being able to lower mass, which coincidentally, links to FTL travel which cannot be done without continuity paradoxes wiping out your existence in this timeline. You can increase or lower inertia to the point of stasis (could never be made more than microscopic scale), or turn baryonic matter to photons or tachyons (theoretical and with no mass and also the aforementioned relativity and related problems).

[Winston Blake]

According to the ol' Rocket, reaction STL (slower than light) drives must carry a commesurate amount of fuel for the mass of the ship. So, with a concept such as contragravity, wherein the effective mass of the ship is reduced (say, for the sake of argument) to 1/10th it's original mass, would that be just as straightforward a calculation of fuel to weight, given no other environmental concerns?

You can write it that way, but you ought to be aware that you're shitting all over some of the most fundamental laws of physics. Anyway, make sure the mass-lightening effect doesn't affect the engine nozzle or you're going to defeat the point by pushing against lightened reaction mass.

You might be thinking that you can beat conservation of energy by fudging your mass-lightener so it needs to be supplied with enough energy to pay back its debt to the universe. However, CoE and conservation of momentum are inextricably linked - you can't have one without the other. If you can magically remove mass, then free energy for all!

Second question: If the concepts of contragravity and artifical gravity would exist, would it be a logical extension to say that a gravity-based focused beam could be used as an effective tractor beam?

If you go with relativity, then you can't have a 'beam of gravity' since it's not 'stuff', it's just how space-time behaves. With quantum mechanics on the other hand, you can imagine a beam of gravitons. I've got no idea if that's possible or what it would do. For example, photons are the EM carriers, yet a beam of light doesn't act on charged particles like a scifi tractor/repulsor.

If you go with fringe theories on inertia being a result of the Higgs field, then you can do mass-lightening, but I don't see any way of shooting that effect at people. I really doubt that Higgs bosons can be turned into a beam. It sounds cool though.

I'm holding back on mass manipulation until CERN or Fermilab find out just what the Higgs boson is like and whether any new physics comes with it. If the vacuum fluctuation idea for momentum is correct too, then it could lead to possible ways to lower this effect, but I'm not holding my breath. Least, not for centuries anyway when it may actually be possible to explore such concepts.

Anti-gravity, though, is simply undoable.

IIRC domain walls in over-my-head physics have negative gravity. Saying that a drive 'manipulates' mini-domain walls to produce antigravity is no less realistic than 'manipulating' the Higgs field to 'suppress' inertia. If I could just manipulate virtual photons, I could effortlessly unravel atoms and nuclei. This is the sort of thinking that put lush jungles on Venus because it was within the realm of possibility at the time.

[rhoenix]

This is fascinating reading. My thanks to all of you for your replies. Though grav-tech is still effectively the realm of soft sci-fi, it would have been the means to an effective end plot-wise. However, being that I'm very much in the "exploring possibilities" phase, if there are any other points anyone can think of, I'd be interested to read them.

[kinnison]

Gravity-blocking material or a forcefield that does same is impossible; it would violate the first law of thermodynamics and lead to perpetual-motion machines of the first kind.

To see why, consider a sheet of Cavorite placed so that it can be placed underneath a weight. Place it there; the weight rises, pulled by various celestial bodies. Take it away; the weight falls, possibly doing work in the process. Where did the energy come from?

The same applies to a forcefield that can be turned on and off.

[Lord Zentei]

Gravity-blocking material or a forcefield that does same is impossible; it would violate the first law of thermodynamics and lead to perpetual-motion machines of the first kind.

To see why, consider a sheet of Cavorite placed so that it can be placed underneath a weight. Place it there; the weight rises, pulled by various celestial bodies. Take it away; the weight falls, possibly doing work in the process. Where did the energy come from?

The same applies to a forcefield that can be turned on and off.

If the effect is acheived by a forcefield, you could claim that it is doing the work -- meaning that it requires an energy source.

[Beowulf]

Wait, so Niven isn't hard SF?

[Cykeisme]

If the effect is acheived by a forcefield, you could claim that it is doing the work -- meaning that it requires an energy source.

Aye.
For example, Star Wars ships have "repulsorlifts" that are essentially anti-gravity (pushing against gravitational fields instead of being attracted). However, even with the use of repulsorlift drives, Curtis Saxton still takes the total potential energy of reaching orbit into account when calculating a lower limit for a ship's reactor power output.

As Kinnison pointed out, using "gravity shielding material" to repeatedly a massive object placed between two more massive objects would definitely violate CoE though. Allowing the amounts of gravitational potential energy in a system to be changed at will also means that energy can be created at will.

[Cykeisme]

If the effect is acheived by a forcefield, you could claim that it is doing the work -- meaning that it requires an energy source.

Aye.
For example, Star Wars ships have "repulsorlifts" that are essentially anti-gravity (pushing against gravitational fields instead of being attracted). However, even with the use of repulsorlift drives, Curtis Saxton still takes the total potential energy of reaching orbit into account when calculating a lower limit for a ship's reactor power output. The repulsorlift helping push a ship into orbit needs feeding!

As Kinnison pointed out, using "gravity shielding material" to repeatedly a massive object placed between two more massive objects would definitely violate CoE, though. Allowing the amounts of gravitational potential energy in a system to be changed at will also means that energy can be created at will.

[SirNitram]

Wait, so Niven isn't hard SF?

Depends on the story. Some stories are Hard SF, some are Soft(Or as I prefer to name it, High Sci Fi), some are middle of the road. He writes whatever technology helps him tell the stories he wants to tell.

[kinnison]

Gravity-blocking material or a forcefield that does same is impossible; it would violate the first law of thermodynamics and lead to perpetual-motion machines of the first kind.

To see why, consider a sheet of Cavorite placed so that it can be placed underneath a weight. Place it there; the weight rises, pulled by various celestial bodies. Take it away; the weight falls, possibly doing work in the process. Where did the energy come from?

The same applies to a forcefield that can be turned on and off.

If the effect is acheived by a forcefield, you could claim that it is doing the work -- meaning that it requires an energy source.

I am referring to a forcefield that simply blocks gravity. As far as I know it is physically possible, perhaps by generating a beam of WIMPs, to create a reaction drive with no obvious exhaust - which could look like Niven' reactionless drive. A really powerful laser would do the same, with rather obvious side effects.

[Sam Or I]

Another thought about "artifical gravity", if an artifical gravity source (lets say 1 G) was introduced into a solar system, would that not be similar to introducing another earth sized planet to the system, possibly disruptung planets orbits in the system?

[kinnison]

Another thought about "artifical gravity", if an artifical gravity source (lets say 1 G) was introduced into a solar system, would that not be similar to introducing another earth sized planet to the system, possibly disruptung planets orbits in the system?

The answer depends on how large an area was covered by the 1G field - in fact, a 1G field with exactly the same characteristics as the real one would necessarily have the same total gravitational potential energy as Earth itself - a rather large number.

Extreme example; an asteroidal-mass black hole. At some surface near the hole the gravity will be 1G; but the effect on planetary orbits would be negligible - at least until it runs into something.

[Cykeisme]

Gravity-blocking material or a forcefield that does same is impossible; it would violate the first law of thermodynamics and lead to perpetual-motion machines of the first kind.

To see why, consider a sheet of Cavorite placed so that it can be placed underneath a weight. Place it there; the weight rises, pulled by various celestial bodies. Take it away; the weight falls, possibly doing work in the process. Where did the energy come from?

The same applies to a forcefield that can be turned on and off.

If the effect is acheived by a forcefield, you could claim that it is doing the work -- meaning that it requires an energy source.

I am referring to a forcefield that simply blocks gravity. As far as I know it is physically possible, perhaps by generating a beam of WIMPs, to create a reaction drive with no obvious exhaust - which could look like Niven' reactionless drive. A really powerful laser would do the same, with rather obvious side effects.

As we've already covered, a forcefield that "blocks gravity" is okay as long as you're willing to violate Conservation of Energy in your fiction.