High and Low Gravity [long]

[Cheiromancer]

Well, if the gravity suddenly doubled. it would be like you were carrying someone around on your shoulders. Your thigh bones would carry twice as much weight, each square centimeter of the soles of your feet would exert twice the pressure on the ground, and so on.

If your growth hormones messed up and you started to grow again, and didn't stop until you were 4 meters tall, something similar would happen. Your feet would be twice as wide and twice as long, but you would be 8 times as heavy; each square centimeter of your feet would have 4 meters of silent bard to carry, not 2, and it would put a lot of strain on your bones.

Or consider an ant. It can carry many times its own body weight. It can fall a hundred times its own body length and not be inconvenienced. But an elephant- elephants cannot even jump! If they fell a hundred body lengths, they would splash. And look at how thick their legs are compared to an ant's. Effectively an elephant experiences a much heavier gravity than the ant does. It still falls at 9.8 m/s^2, of course, but physiologically the gravity is experienced very differently.

 

[thesilentbard]

Gravity is a force that attracts you towards other objects (and vice versa with the same intensity), right?

Since weight is equal to mass*gravity, all objects are affected by the same factor.

The fact that if I would suddenly grow and my bones would snap is correct. But that is why there is a maximum size for humans. The conception of the human body is only good at our size.

The fact that an elephant would go splat after falling one hundred feet and an ant not is especially dependant on kinetic energy. 1/2*mass*speed squared = kinetic energy
The speed is the same for both the ant and the elephant. So the interesting factor here is mass. An elephant weighs easily around 5'000 kg, if not more. An ant, I'll guess the weight at around 0.005 kg. So the elephant acquires one million times more kinetic energy than the ant. The structure of the ant (a carapace composed of the same material as our nails) has good chances of resisting that fall, the flesh and vital organs that absorb the elephant's fall are less resistant than the carapace of an ant, and have to embrace a shock 1 milion times greater than that of the ant. That's why it goes splat.
Gravity is just responsible for the speed both acquire, and that is the same for both if we don't take into account the laws of aerodynamics and the resistance of air.

The fact that an ant can carry weights many times superior to it's own is due to the way an ant is "constructed" (pitty is, that construction only is useful to creatures that are quite small, for the same reasons you explained why my body getting bigger would surely destroy it).

The jumping factor is due to a similar reason to the above (an ant can hardly jump, but a flea will make tremendous leaps).

The gravity is effectively experienced differently by bigger objects, but that is why they are so different from the small ones, and are adapted to their size. I wouldn't make any modifiers depending on size of the creature for D&D, since we can assume that each creature is adapted to its normal gravitiy.

 

[Cheiromancer]

Exactly. Creatures are well adapted to the current gravity and their current size. And suddenly increasing the gravity would be like suddenly increasing the size.

There are some rules in the books for increases to size, so I fiddled around with them to get some rules for increases to gravity.

 

[thesilentbard]

So the example where you compare an ant to an elephant is not quite right.

An increase in size with or without increase in mass? (logically there should, but with magic you never know)

Getting away from this pseudo-scientific discussion, the first draft of rules doesn't look bad

 

[ax0n]

I have a couple of ideas to determine whether a given creature can cope with being in a high gravity environment, what effect acclimation has, and so on. But lets see if anyone reads this, first.

You never finished this

 

[Cheiromancer]

Ok, I've decided that each 10% increase in gravity effectively imposes a -1 high gravity penalty to Strength, Constitution and Dexterity. Each 10% decrease in gravity gives a low gravity bonus to these penalties.

If someone's effective ability score reaches 0, they are incapacitated in some way; they cannot get up, they are permanently exhausted, their heart gives out or limbs break, etc..

The following should be put in a foot-note or sidebar somewhere:

Small creatures halve the modifiers, tiny creatures divide by 4, and diminutive or fine creatures divide by 6.

Creatures larger than medium size receive the standard bonuses from low gravity, but suffer more from high gravity. Large creatures suffer double penalties to Strength and Constitution from high gravity, and standard penalties to Dex. Huge or larger creatures suffer quadruple penalties to strength, double penalties to Constitution, and standard penalties to Dexterity.

Appropriate protection will reduce a creature's size category by 1 or more. A seated human in a high gravity field is effectively small; laying down would be considered tiny, and in a special crash couch or fully immersed would be considered diminutive. Dragons on high gravity worlds are typically aquatic. They are also usually smaller than standard dragons.

Every 50% increase in gravity halves a creature's base movement rate. The range of missile weapons is also halved. At 100% normal gravity, movement rates and missile ranges are 1/4 standard, and so on.

Each 50% decrease in gravity boosts a creature's base movement rate by 50%. Under zero gravity a creature can move at twice its normal speed. The range of missile weapons increases accordingly.

(Note that at zero gravity an arrow will go virtually forever, but the element of control is such that the effective range is still limited).

Falling damage increases by +1 hp per d6 per point of high gravity penalty. For example, in 150% of normal gravity, damage is 1d6+5 per 10 feet fallen, to a maximum of 20d6 + 100.

In low gravity fields determine the damage normally, then multiply by the low gravity. A creature falling 200 feet in a gravity field only 40% as strong will take 8d6 of damage.
---------------------------

Ok, I think this is close enough to what is scientifically plausible to work. Now comes the need for acclimation. This I am much less certain about:

High Gravity field: Each month a creature will make a Fortitude save vs DC 10 + high gravity penalty. Success indicates the removal of 1 point of the high gravity penalty to Strength, Constitution and Dexterity due to a temporary increase in those statistics. Failing the save indicates that the creature's Strength, Constitution and Dexterity have been permanently reduced by 1 point. The save DC decreases by 1 each month. Temporary increases to a character's ability scores fade at the rate of 1 point per week.

Low Gravity field: Each month a creature will make a Fortitude save vs DC 10 + low gravity bonus. Success indicates that one point of the high gravity bonus to Strength, Constitution and Dexterity is removed. These statistics suffer a temporary decrease. Failing the save indicates that the creature's Strength, Constitution and Dexterity have been permanently reduced by 1 point. The save DC decreases by 1 each month. Temporary decreases to a character's ability scores fade at the rate of 1 point per month.

Comments?

 

[ax0n]

they cannot get up, they are permanently exhausted, their heart gives out or limbs break

Could we expand on this point in some way. Do characters receive hit point damage if they break a limb, or more permanent damage if their heart gives out? Do they risk death?

Under zero gravity a creature can move at twice its normal speed

Would zero gravity prohibit movement as much as it helps it?

Also, aren't there long-term problems for exposure to high/low gravity as well as benefits. Don't you have to acclimitise back to you own gravity?

I've emailed you a file containing all the information on advanced gravity you've sent me. I'll be using it as an aside in the 2.0 version for our Plane Construction System. Let me know what you think

 

[thesilentbard]

I'm not sure making stat penalties is a good way to handle it.
If a human with strength 17 (+3) suffers from high gravity, his stregth goes down to 16 (+3).
Another with Str 18 (+4) would go down to 17 (+3).
If they where to grapple, they would now have equal chances of winning (if we consider they have the same BAB), although the Str 18 had slightly better chances of winning under normal gravity.
I'd think that someone remaining a length of time on high gravity worlds would actually become stronger, but I wouldn't implement such rules, since D&D doesn't provide rules for other means of physical training.
Since relative strength remains the same, maybe just give a -1 penalty to all rolls depending on the affected stats until the creatures grows accustomed, without actually decreasing them.