D&D 5E Wherein we discuss spells and other magical things.

[Oofta]

But really, what I want to know is...

...if the guy inside the sphere is not going splat when he hits the ground, it stands to reason the energy generated from the sphere with the guy in it hitting the ground gets sent out from impact point. Seeing as none of that energy -which would normally turn the body in the sphere to shattered broken mush- is being utilized and has to go somewhere...

Does the single plane of kinetic energy speeding away from the sphere's point of impact slice the 10 orcs waiting around having cigarettes at the bottom of the cliff off at the ankles...or simply shatter their ankles and shin bones inside their skin?

Obviously the plane of kinetic energy will radiate from the point of the sphere with the greatest circumference of the sphere parallel to the ground. In addition since we are prohibited from causing damage to organic living matter [for reasons], the orcs would not be directly affected. Their cigarettes however would explode with the force. BEST SMOKING CESSATION IDEA EVAR!

 

[Dannyalcatraz]

We have. The magic of the sphere stops the person from escaping the sphere.



Except that it can't be. Something that has no mass cannot have momentum. Therefore you cannot transfer momentum through a massless object (assuming the sphere is treated as an object).



It doesn't have to. It's magic. We know the occupant cannot physically pass through the sphere. They cannot interact with the ground. However, if the sphere decelerates to a speed relative to the ground of zero, the occupant is also going to decelerate to a speed of zero relative to the sphere.

There doesn't have to be conservation of energy or momentum or any logical consequence that would happen if someone fell onto a physical object. Why? Because ... repeat after me ... magic is stopping the occupant, not a physical object.

In my campaign from a metaphysical standpoint, I would say that the energy behind a spell is pulled from the ether. The ether surrounds us, some creatures such as dragons naturally pull power from the ether as readily as they breath, magic users pull energy from the ether to power their spells or to create objects. The momentum of the creature hitting the wall of the sphere is transferred to the ether which transfers an equal amount of force back to the creature.

Ottiluke would have to be dumb as all get out to design a spell that- for 1 minute- renders him essentially immune to harmful kinetic effects originating outside it, but would then, nevertheless magically deliver the exact same amount of energy to the occupant if the kinetic energy were great enough.

If nothing else, if he survived the trial runs of the original "cliff drop tests" for the ORS, he'd have built Feather Fall into it to avoid that scenario.

 

[Dannyalcatraz]

A related question: what would happen if someone jumped from a great height onto a wall of force? Nothing can physically pass through a wall of force. You could drop a mountain on top of one and nothing would happen to someone standing underneath. Yet a wall of force can be free floating. What happens to the momentum of the falling mountain? Are you saying that someone that falls onto a wall of force would take no damage?

There's already a thread tackling WoF issues...though not really that one.
http://www.enworld.org/forum/showth...rce-Reality-Check-(as-used-by-DM-not-players)

Well, just like not all magical fire behaves the same way, neither are all force effect spells identical in behavior. ORS and WoF do have some differences. While both are force objects, one can be dispelled, and the other cannot.

Also, tellingly (for me), while both ORS & WoF prohibit items physically passing through them, only ORS has language stating that the protected creature is protected from damage- "a creature or object inside can’t be damaged by attacks or effects originating from outside, nor can a creature inside the sphere damage anything outside it."

In contrast, the WoF dos not explicitly negate damage of any kind, just makes it a hell of a lot harder to deal any out. So, I'd rule that the horizontal WoF would act identically to any normal solid object and splat the posited jumper.

If the jumper was also the caster, I'd hope he'd be bright enough to cast it directly under his feet and

1) orient it like a slide to a softer landing zone,
2) make as big a flat (or concave, if headed for water) surface as possible, to increase wind resistance, minimizing his terminal velocity

(Too bad the linear version of contiguous 10x10 panels has to be flat- if the ones at the tips could be angled, instant force copter!)

 

[Lanefan]

In the double body problem, the ORS is stopped by the ground, then milliseconds later, the occupant smacks into the ORS's inner surface. We know from Newton's 3rd, that the falling occupant can only decelerate if an equal and opposite force is applied to his momentum. So we have to ID the source of the force.

1) the occupant can't be the source- that would mean he is not only supplying his kinetic energy, but somehow supplying energy to stop himself. How can he do this- doubling his energy- without thrusters?

2) the sphere can't be the source- for all intents & purposes, it is massless, and cannot deliver enough energy to decelerate the occupant. If you hit a relatively massless thing with something heavy, the massless thing will deflect off at a high velocity and the more massive object willhardly be slowed at all. The double body problem is essentially the falling boulder illustration twice- first, the great mass of the ground halts the ORS without noticably slowing, then the same sphere is struck by something else with a great mass compared to itself. If it could, it would simply start moving again, the occupant hardly slowing.

But it can't move because it is resting on the earth, you'll say. This is true, which gets us to:

3) the ground is the source of the deceleration force.

It's the only thing that can supply it.

But this outside deceleration force, originating as it does from outside the ORS, can't damage the occupant...the same answer as in the single body problem.

While there's logic here, it still doesn't answer the very basic question of how the occupant can decelerate from falling speed to 0 speed (or accelerate from 0 speed to high speed just as quickly when golfed by a giant) in less than a heartbeat without taking some serious pain even just from the g-forces involved.

Secondary question: if the sphere isn't directly falling as such but instead rolling and bouncing down a long rocky bank, what happens to the occupant?

Lanefan

 

[Lanefan]

Ottiluke ... If nothing else, if he survived the trial runs of the original "cliff drop tests" for the ORS, he'd have built Feather Fall into it to avoid that scenario.

That was the higher-level version of the spell that he never quite finished before his campaign shut down.

 

[Dannyalcatraz]

While there's logic here, it still doesn't answer the very basic question of how the occupant can decelerate from falling speed to 0 speed (or accelerate from 0 speed to high speed just as quickly when golfed by a giant) in less than a heartbeat without taking some serious pain even just from the g-forces involved.

What I have been saying this whole thread: the occupant can't be damaged by a force originating outside the ORS, and the deceleration force on the body is a result of the ground pushing back hard, a la Newton's 3rd. So, the dangerous levels of kinetic force are magically nullified by the ORS or the kinetic energy is converted into magical energy which is returned to the source from which all casters draw.

Assuming the occupant doesn't have a fear of heights or some such that would force a concentration check to see if he can maintain the ORS throughout the fall and impact, to him, it will feel like stepping off a curb.

To me, either of these options makes infinitely more sense than the posited magical backlash that damages the occupant with the exact amount of damage as the nullified impact.

Secondary question: if the sphere isn't directly falling as such but instead rolling and bouncing down a long rocky bank, what happens to the occupant?

I think this is actually a tastier question.

The occupant is jostled, but not damaged. But since he is rolling down an incline, he's got to maintain his balance. That takes a little concentration. I'd probably make the player roll both to maintain the ORS and his upright posture, or- to simplify- make a single penalized roll to maintain both.

With the single-roll method, a minor failure, and either the PC falls or concentration on maintaining the ORS is lost. A major failure, and both are lost.

 

[Oofta]

What I have been saying this whole thread: the occupant can't be damaged by a force originating outside the ORS, and the deceleration force on the body is a result of the ground pushing back hard,...

One more time...

Let's suppose you put a sphere around Grog the Orc. Unbeknownst to you, Grog has claustrophobia. Once he realizes he's doing a mime in a sphere impersonation he freaks out and starts punching (with his unprotected fist) over his head. At the top of the sphere.

Does the sphere stop his fist?

If the sphere stops his fist, what is pushing back against his fist? The ground can't be pushing back, he's punching above his head. What is the unbalanced force that is stopping the momentum on his fist?

While D&D doesn't really model this (it's a DM's call) if he punches any significantly hard surface with his fist using all of his strength, assume for a moment that at some point he would hurt himself. How is Grog's hurting himself through momentum he caused different from getting hurt from the sudden change of momentum when landing after a fall?

I know the sphere is not possible in our (mostly) Newtonian universe. Neither are force fields. Neither are dragons that fly and breath fire (at least not with the wingspan normally depicted). Magic sometimes overrides physics.

 

[chaochou]

2) the sphere can't be the source- for all intents & purposes, it is massless, and cannot deliver enough energy to decelerate the occupant. .

The sphere is the clear source of the force upon the occupant, irrespective of its mass. It is, quite literally, a sphere of shimmering force. The ability of the sphere to exert force is totally unrelated to its mass. Otherwise I can punch the occupant in the face because physics tells us a massless sphere can't exert a force on my fist to stop it.

But we know the sphere can exert force, and we know it exerts resistance against an occupant trying to move it. So when said occupant smashes into the inside at 120mph it resists and the result is highly unpleasant for the unfortunate victim. That is all entirely consistent with what we know about the sphere.

 

[Dannyalcatraz]

One more time...

Let's suppose you put a sphere around Grog the Orc. Unbeknownst to you, Grog has claustrophobia. Once he realizes he's doing a mime in a sphere impersonation he freaks out and starts punching (with his unprotected fist) over his head. At the top of the sphere.

Does the sphere stop his fist?

If the sphere stops his fist, what is pushing back against his fist? The ground can't be pushing back, he's punching above his head. What is the unbalanced force that is stopping the momentum on his fist?

One more time...

The kinetic force is magically nullified by the ORS or the kinetic energy is converted into magical energy which is returned to the source from which all casters draw- magic overriding physics.

 

[Oofta]

One more time...

The kinetic force is magically nullified by the ORS or the kinetic energy is converted into magical energy which is returned to the source from which all casters draw- magic overriding physics.

I agree with that. Which then means that the ground does not provide the opposing force on the occupant of the sphere when they decelerate from falling speed to 0 in an instant.

Which means that the rapid change in velocity still occurs when the sphere stops when it hits the ground. Deceleration is what causes damage.