You've got physics in my D&D!

[Castellan]

Our resident physics major informed her that, due to conservation of momentum, if her mass changed from a 10-pound fox into a 120-pound woman, her momentum would be reduced by a factor of 12, which would cause her to fall short. We laughed and ignored science, and ended up with one bisected monster.

I'm a Physics and Astronomy guy... This is exactly how to deal with this kind of thing: mention that something might not work that way in real life, then ignore it. It's a game, and as a DM, I'd allow something like this to work because it's freakin' cool.

On a side note, your Physics guy would only be correct if the added mass appeared at a velocity of zero. Ignoring the issue of mass appearing and disappearing during polymorph, one can assume -- using Phantasy Physics (TM) -- that it just doesn't matter. Ultimately, your only real argument here is based on air-resistance. If you transform from a fox into some critter with a low mass and high surface area (say, a giant bat) then I might say you're unable to accomplish the task. However, in college, one of the things we learned is that the human body makes an excellent projectile with very low air resistance.

In my games, I have a tendency to stick with real Physics and Astronomy only when it makes sense from a dramatic standpoint. If you have Mind Flayers trying to extinguish the sun, Physics is just going to make your life (and your game) miserable. If it'll benefit the players and isn't completely unbelievable from a basic Newtonian Physics standpoint (i.e. no running on small tree branches per Crouching Tiger, Hidden Dragon unless they're under the influence of some kind of spell), I generally allow it.

P.S. -- Actually, I take exception to the fireball spell in 3.x. Since it creates heat but no force, you have a problem. Pressure and volume are directly proportional to the temperature of a gas. If you heat the gas (i.e. the atmosphere) then either the pressure has to increase, or the volume does, or both. This is what results in the outward force. The change in fireball never sat well with me. I suspect it was altered to make creating video games easier on the programmers, since they don't have to worry about (a) the volume of the explosion expanding into a dungeon corridor when the spell is set off in a room that's too small, and (b) blasting the PCs, NPCs, and monsters across the map. I don't like video-game changes made to my pen-and-paper game.

 

[Aristotle]

I've *never* had a physics discussion with my group in D&D. We simply use the implied physics within the rules (jumping heights, movement speeds, etc).

Now the physics discussions/arguments were an always present part of my White Wolf game back in the day. Mage: the Ascension (despite the fact that I think the magic system in it was an amazing mechanic) was a mine field of physics. And you always have that one player who knows (or thinks he does) enough about just about any subject to make an argument why Forces should cover this or Time shouldn't do that.

I really hope they clean up that system, but preserve its dynamic feel, in the new product line. I'm waiting on Mage before I get any of the new WoD stuff. That book will make or break the entire setting/system for me.

 

[ledded]

We've had a few situations where physics has come up, but we've always been able to rectify those fairly quickly (several folks in the group are very well read or have experience to back things up).

For the most part, we don't worry about it. The fireball/lightning bolt at your feet effect? Well, even though we take turns, we try to realize that everyone is moving constantly. The spell might have exploded just as they zoomed/ducked/rolled through that square, the casting may have warned them enough to be ready to take some kind of defensive action, etc. Sure, it does take a little hand-waving but we try to not get too tricky.

That being said, whoever the GM is will often bestow a penalty or even (rarely) deny a save in a particular situation that makes sense. Trapped at the bottom of a smooth 5' wide pit and someone drops in a fireball? Well, that's gonna sting a bit even with evasion, and as players we're often smart enough to know when modifiers should apply.

 

[snarfoogle]

Saving at the epicenter of a fireball? Quite simple... the character jumps and clings to the ceiling.

 

[reanjr]

It's not a handgrenade or a cannon shell. Every spot within the area of effect is of similar heat and pressure, where as in a normal explosion pressure and heat is higher in the center. Fireball has no center, if you will.



Most PCs also have natural armor

Speaking of which, I just recently discovered that it is possible for a fireball to work in a semicircle in the middle of a field.

If you cast it to the extent of its range, the fireball explodes back towards you but not outward away, creating a half circle of fire. I'm sure this could somehow be abused tactically but I can't think of it...

Magic is magic and makes no sense. On that, I'm usually pretty lenient on reality. "It's magic" is a good enough explanation for jsut about anything related to a spell. On the other hand, I do use conservation of momentum to avoid abuses. The aforementioned person thrown and turned into a fox to go 12 times faster is a moot point, because the warrior could have just thrown the fox 12 times farther in the first place. Also avoids pebble-crushings. And somehow deftly avoiding a falling boulder by shrinking it (it would just go that much faster and careen right through your skull, though you might save those around you).

 

[Orryn Emrys]

Interestingly enough, I have been in the position to make that fireball decision before, and I remember deciding on the spot that the PC at the center of the event wasn't allowed a saving throw. As I recall, I simply made this decision and delivered it in a matter-of-fact manner to the player in question, who, despite being disappointed at being trapped in this particular situation, would never have even thought to argue.

IMO rules should not be enforced if they seem nonsensical, or even, as in this case, simply unlikely. I believe in presenting a very organic world. Any number of details might factor in to such decisions. I might have decided the opposite verdict, and the players in my game may have wondered how exactly that person managed to avoid much of the damage. Most importantly, however, although I will often discuss a potential ruling with the table, referees in our group are not generally subject to being argued with. I do welcome criticism of a decision once the session is over, but not during game play. And such criticism is always offered respectfully, regardless of the detriment to any character resulting from my judgment. If a strong enough case is made concerning a rules argument, it will be handled differently in the future.

More often than not, however, this kind of decision isn't contested. If it were, I wouldn't offer speculations; I would explain the event according to the character's perceptions, i.e. an earlier injury made a character's leg stiff enough to hamper his movement at that critical moment, or the lose sand beneath the character's feet makes it impossible for him to move fast enough, etc. Or the fire simply rose all around him so fast that he had no idea what to do to escape immolation. Keeping the entirety of the environmental impact of the game solidly in the perspective of the PC clears up a lot of difficulty in adjudicating a character's options. And, at times, these options will be in direct violation of a rule that would work entirely differently in a vaccuum, or even most standard applications.

 

[Orryn Emrys]

Sorry 'bout that!

 

[El Ravager]

Not really physics, but it is a weird instance of science in my D&D game...

Once we had a player calculate the gold piece value of a pile of gold filings based on the atomic weight of gold from the periodic table of elements.

They had a lump of gold that they had scraped off a gilded statue. The PCs knew the size of the pile of gold, but I as the DM had no idea how much it should weigh. I asked the group if anyone had a reasonable estimate and I noticed one player hunched over looking at his calculator.

He looked up and asked if he could use the internet so that he could look up the periodic table of elements.

We proceeded to throw things at him and took a break to go to DQ while he did his calculations.

======
El Rav

 

[Saeviomagy]

Fireball is just one example of a spell that niggles at me. Not a ruling that I have made. Incidently I don't make rulings I discuss options, and I never change the rules in a way that would be instantly detremental to the players, without discussing it with them at length.

Well, what it sounded like you did was
<fireball goes off>
You (to player): Your character takes 80 points of damage
Player: Phew, lucky I saved and only took 40. Otherwise that would have killed me
You: Erm, actually I've just had a thought about that. I don't think you should get a save.
Player:Whaaa! But the rules say I do.
Other players: We don't care about our buddies well-being enough to comment. After all, the fireball didn't hit us.

Thank you for making assumptions and being quite rude though! I always like that!

Hey - you said that you had an argument with a player, that the argument was in-game, that the other players didn't complain because they weren't taking the damage and could survive anyway (inferring the character taking the damage couldn't), and that you capitulated.

You then basically accused the arguing player of being a whiny crybaby. I'm not going to just let you get away with that. The guy deserves some sort of defense. It's clear YOU don't understand why he'd have a problem with the rule that you came up with on the spot, when it would have the worst possible deleterious effect upon him.

Pulling that kind of stunt tends to make players defensive about the rules. No wonder he complains.

 

[soulcat]

You then basically accused the arguing player of being a whiny crybaby. I'm not going to just let you get away with that. The guy deserves some sort of defense. It's clear YOU don't understand why he'd have a problem with the rule that you came up with on the spot, when it would have the worst possible deleterious effect upon him.

Pulling that kind of stunt tends to make players defensive about the rules. No wonder he complains.

I do understand why he'd have a problem with not getting a save which is why I decided to go with the rules.

I accused him of being a "whiny crybaby" because he didn't understand why I wanted to discuss the possibility of a fortitude save or no save. The argument came about because he wasn't even able to enter the discussion. He just couldn't see any point of view apart from his own.

When I called it an argument, what I mean is I tried to put my point across, he got defensive and sulky, I tried to give him some idea where I was coming from, he got upset.

I didn't "come up with a rule on the spot" I told him I wasn't happy with the way the rules work, and tried to explain why. If I had come up with a rule on the spot I would have understood him having a problem.

Once again you are making assumptions about what happened on the night, when you where not there and have not met either of the people involved, and attacking me for what you see as my wrongs.

I would appreciate it if you wouldn't do that.