The question isn't if there is a cost (and I assume this is what Peter means when he refers to energy and power; most people use those words to refer to things like battery time and fuel usage), simply what it is. And this and other quotes indicate that the cost increases with increasing mass. Unfortunately, we know nothing about the means of generating that force or how efficient it is, so we don't have nearly enough information to calculate how much magic it takes.The cargo-master slapped his shoulder again, harder this time, and Halesak nodded vigorously. Then the dragon swept over the parapet of the fort, clearing it by barely fifty feet, and braked into an abrupt hover as the Gifted cargo-master activated the levitation spell.
The spell wouldn’t support the dragon’s heavy bulk for more than a very few minutes, but that was all the time in this universe – or any other – Iftar Halesak and his men needed.
Louis R wrote:That's why "power" is in quotes - the whole exercise is physically meaningless. I engaged in it simply to show that the original suggestion lead to a result that doesn't make any sense - that the longer you stay up, the less power you need to do it.
BTW, that helicopter is a perfect example of what I've been trying to get at; thank you.The energy is not being spent 'holding it up', it is spent moving the rotors against the drag force of the air they're moving in: it is being dissipated internally in the system that generates the force holding the aircraft in equilibrium. And in fact it does matter how high it is, although usually not enough to notice - drag is a function of air density and temperature, and decreases with height at a different rate than the lift generated by the blades.bkwormlisa wrote:The problem I have with this calculation (and Peter's) is that you're using the potential energy of height. A helicopter (to use the previous example) doesn't care about height. it can be 100 or 1,000 or 10,000 feet off the ground, and it takes just as much additional force from the rotor (and thus, additional energy/fuel) to hold it up. Textev is that levitation accumulators can be used to let a dragon carry tons more, so they aren't "pushing" off the ground and the height probably has little or no relevance. So I don't believe any calculation that relies on height or time to reach the ground can be applicable. That's what I find so difficult about calculating this sort of thing.
I cannot believe that it can hover there for free, whatever the physics involved, and the textev specifically states that it can't. It also states that the higher the weight, the more the cost and/or the lower the time it can float is. Calculating how much magical energy it takes will depend on how much magical energy it takes to create a force that can counterbalance the weight, or to change the gravity of that much mass to zero. Unfortunately, I don't think we have enough information to make that calculation.
Peter, I don't agree that there are clearly two different types of levitation. Something is creating a force that is perpendicular to the gravity field (and in some cases, like the chairs and table, prevents it from easily moving laterally as well), but there is no evidence of how. It might be making the stretcher (or whatever) "fall" upward with enough force to support whatever is lying on that (as a crude description), but we don't know if it involves gravity or not. Even if it is manipulating gravitons, that would not mean it had zero mass, simply zero or negative weight. And there is equally no evidence that anything on or in the levitated object is directly affected by the spell; it appears that they are held by normal force against the surface.
But it could just as well be electromagnetic or something that has no connection to anything we know. Weber has said the physics in their home universes does not match ours, after all, and the suggestion is that such things won't work on Sharona either. So it may be "pushing" off something that doesn't even exist on Earth. It's equally possible that Weber hasn't specifically named the physical force it's using because he doesn't care. It works, and while he usually tries to describe physics to explain how things work in space, in a situation where nothing we know applies, he may not even define it to himself. Because of that, I think we're chasing something in circles that can't be caught.
PeterZ wrote:I would like to complicate the issue. Text describes 2 different effects from levitation spells. The levitating chairs and tables of the Fallen Timbers negotiations did not function as if they and the objects or people on them had zero mass. Those tables and chairs were suspended by some force making them stable enough to sit on and rest items on.
The levitating spells used with transport dragons do appear to alter the impact of gravity on the mass within its area of effect.
Neither affect changes our inability to calculate the amount of energy involved or know the level of Gift required create and then charge the different spells.