The energy is already inside the sphere, it's just converted from potential to kinetic energy as the wizard accellerates down the gravity well.
Fair answer, but two things. First, your position still requires a fairly big assumption about how the gravitational interaction passes a barrier that either cannot be modeled in physics or has exceptional physical properties with unknowable ramifications. The occupant only accelerates downward if the force of gravity is acting on it (and perhaps only if he or she uses an action to push the sphere downward). It may be that the potential energy ceases to exist at the moment that the sphere appears. (Remember that it's magic; it can violate the law of conservation of energy.)
More to the point, that explanation only covers half the energy. Under normal circumstances, a fall results in this: the action of the body hitting, and the reaction of the ground resisting the hit. Or, if you prefer, the body accelerating downward due to gravity and then accelerating upward ("decelerating") due to the immense mass and rigidity of the ground.
So. The sphere explicitly cannot pass energy or physical objects. This means that it cannot pass the momentum of the falling occupant to the ground (action), and cannot pass the inertia of the ground to the occupant (reaction). The interaction (the collision) therefore cannot happen. You have the downward acceleration of the fall without the upward acceleration of stopping. Thus I say that you have half the energy that you need.
So what happens in this situation? We have no clue, because the laws of physics are not mutable in our universe. The sphere may allow the occupant to fall through the ground, since the sphere has no reason to stop if the occupant does not stop. The two may "fall" out of their reality entirely. The sphere stopping of its own accord and the occupant going splat against the inside are not consistent with the spell's description.
Satyrn said:
But he's already explained to me (twice! I'm dense) how he gets to weightless also being massless, providing a formula that proves that an object of 0 weight in a gravity of >0 has a mass of 0. Since we know the object is weightless, and we're discussing how this works on a planet (thus assuming some gravity) he has shown that the sphere ought to be massless.
First, magic can alter gravity, so Oofta's formula does not prove masslessness. Second, what Oofta has given is
one convention for the use of the word "weight," which does not really correlate with a use of the word "weightless." By his standard, nothing (except some particles) could be weightless in our universe unless infinitely distant from all other bodies. Yet surely you have used and heard used the word "weightless" in your life and understood its meaning to be practical. A person floating in the Red Sea or an astronaut in orbit might be "weightless" in everyday speech, but those individuals continue to both have mass and be affected by gravity. So I keep saying that he is not correct because the convention he uses to define "weight" is not in keeping with the common-language design philosophy of 5th edition.
Oofta said:
I think we can agree that the sphere magical. There is no need for the sphere itself to obey Newtonian physics. Correct?
Probably my biggest mistake is trying to describe the walls of the sphere in terms of a physical construct, because it is not. It has influence on some aspects of the physical world, but it is not what we would consider normal matter and does not need to obey Newtonian laws of physics.
Okay.
(BTW massless particles do break Newtonian laws, there was this guy Einstein who had to make up new rules because of it.)
Thanks for condescending. You're so very smart.
We know the sphere weighs nothing. It is impervious to weapons, [magical] energy and spells. We know it (and therefore it's occupant) can be moved. I always assumed it was simply a spherical wall of force that surrounded a creature that can move and be moved (unlike a wall of force). Normal weapon attacks are not going to jostle the sphere enough to cause damage to the occupant, falling is an edge case that is not mentioned in the rules.
Close enough to what the spell description says that I'm willing to go with it.
I see no reason to believe the occupant of the sphere would not obey basic laws of momentum, velocity and acceleration.
Hence the creature follows Newton's first law: an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
This is something of a matter of interpretation, depending on how literally one takes the "nothing" in the spell description. I would also add the qualification that the occupant obeys normal physical laws
except where that would violate the functioning of the spell given in the description.
If there is a change in velocity of the sphere . . .
This is the sphere acting in a physically realistic way, as we just agreed that it doesn't need to.
That "unbalanced force" in this case is the interior wall of the sphere.
As is this, in a way that is pretty damaging to the point you are trying to make.
There doesn't have to be any conservation of momentum, force or energy in the traditional sense because the occupant is not interacting with a physical object.
This is exactly why it is impossible to make the case that the occupant would take falling damage. Neither the ground nor the occupant is interacting with a physical object, so to play it such that the outcome is essentially the same as if the two physical objects interacted with each other is, I would say, a violation of the functioning of the spell as given in its description.
I don't have a problem with a reading of the sphere as a spherical wall of force, but, as I roughed out earlier, its terminal velocity would be around 25-30 miles per hour, so the occupant would never go splat in a terribly energetic way. If it falls at all. The mobility of the sphere, as I keep saying, might be entirely a magical effect, and it might freely resist gravity, just as the wall of force does.
Sidetracked. It can be a spherical wall of force, but I don't think that it is consistent with the other effects of the spell to say that the occupant would take falling damage, because what the spell does, however it does it, is to separate the occupant from the outside world and protect him or her from damage. It is easy enough to say that the magic absorbs the impact.
