I love how everyone is discussing the physics of a cannonball gun DIY setup in a game where magic can instantly teleport people or turn a person into a huge dragon.
Point is well taken, but D&D magic doesn’t take physics off the table, it violates physics within strict limits. Mundane physics still operates. As a DM a good reason I can think of for invoking physics in cases like this is that the player’s plan depends as much on physics as it does on magic, and I don’t think their cannonball trick would work. The gunpowder imparts the same momentum to the shrunken, diminished-mass cannonball as it would to a regular bullet. When the cannonball’s original size and mass are restored, it still has that much momentum - which I imagine will carry it a few feet.
Fortunately my game group includes a very smart player with a master’s degree in physics, who is very quick at computing such things. I would absolutely trust her estimate of how far the cannonball would go.
I would say that using modern physics in fantasy is not always a good idea. Depends on the setting I suppose.
In DnD there are a lot of concepts taken from premodern physics like the four elements, flogiston(even though it is completely different from what it was in the real world), alchemy is present too I suppose. So why would you insist on mkdern physics?
Inversing this gets really fun: enlarge spell on a tungsten/mithril bearing or toothpick. Pack enough charge to fire it out of an actual piece of siege equipment, hello nearly relativistic projectiles. Ship or battlement mounted rods from God.
"We strategically position our ship to ensure the flight path of the projectile happens in 6 second intervals, allowing for a near perfect rhythm of enlarge chanting. We keep three wizards and a wild magic sorcerer near each of our cannons.
Firing even a 42lb cannon wouldn’t capsize a decently large ship. A 42lb projectile at 1700 ft/s carries like 425 million joules of energy. Then shrink that mass down from 42lbs to 0.5 lbs and let conservation of energy multiply the and whatever is in its flight path is going to have a really bad day. Like a “half a pound traveling at 0.6% of C” level of bad day.
With magic metals like mithril you can probably make a siege cannon of at least double the poundage. Modulate the load and use a tungsten wire instead of a toothpick, and you make a plasma weapon. You would need wizards dedicated to calculating the firing solutions to ensure you don’t miss your shots. Einstein would be the deadliest mother fucker on the Sword Coast.
Well, the cannon only needs to produce enough force to move a tiny cannon ball really fast.
The 6 second interval is to match the in game fight sequences, implying that the enlarge spell would finish casting as it impacts the enemy ship. All of that momentum suddenly comes to a grinding halt as the weight suddenly changes and the cannon ball rips the enemy ship to shreds
I came here to point out exactly this: If you only shrink the ball, without reducing its size, well… you’re gonna have problems carrying the ammo.
As a DM, I think I would let them both shrink and reduce the mass, and wait till they fired the weapon before invoking “conservation of momentum” and declaring that the cannon ball drops to the ground after about a meter.
Dunno about 5e etc. but in 1e, which I still play & DM, Enlarge and its reverse affect both the dimensions and mass of an object. So the cannonballs could be reduced to a mass a gun could shoot.
Well in that case, the reverse would also be true. So my barbarian can throw a cannonball at someone. How about if the mage readys the shrink spell to target the cannonball just as it leaves my hand? Conservation of energy would dictate that:
Decisions like these are what makes TTRPGs so fun, and I enjos every minute of these sort ot discussions.
Throwing a shrunken cannonball would work the same as shooting it out of a gun. If you throw an object that weighs one ounce at the time, it flies away with the amount of energy it took to accelerate an object that size to whatever velocity you give it. When the shrinkage magic stops, its mass returns to normal. This doesn’t change the amount of momentum the barbarian or the flintlock gave it. Think of it this way - if you get magically shrunk and you pick a flower, when the magic stops and you grow back to normal size the flower doesn’t also grow. It wasn’t affected by the magic and isn’t affected by the magic going away. Neither is anything else you acquire while shrunk, like momentum.
I noticed I didn’t even finish my previous comment, oops.
I do understand the physics, I work in engineering. I also looked at the spell desctiption from 5e D&D, it reduces the weight by 8, so the reduced weight would still be about 1-2kg. Not exactly a bullet yet.
Yeah, but D&D also has spells and potions of shrink / enlarge that don’t make players start drowning in atmosphere their lungs are too small to breathe or collapse under their own weight due to square cube law restrictions, so there’s definitely some magical physics at work in there.
You’re right, it’s very wonky, but that doesn’t validate not caring about physics at all, and the intellectual exercise of working it out is fun - which is the whole idea.
I see people make comments like this about shows, movies, etc. and I’ve never understood this line of thinking. I generally expect things to work the same as they do in real life unless it’s explicitly explained otherwise. Not sure if I’m the odd man out in thinking that way or what.
you sorta said it but an exception is places like the fae wilds, where you assume physics is only barely present enough to hold your organs together (hopefully)
No, you’re right IMO. Just because something is different from our world doesn’t mean all logical consistency is off the table. This idea is called versimilitude.
I love how everyone is discussing the physics of a cannonball gun DIY setup in a game where magic can instantly teleport people or turn a person into a huge dragon.
I’m not complaining, I just find it amusing.
Point is well taken, but D&D magic doesn’t take physics off the table, it violates physics within strict limits. Mundane physics still operates. As a DM a good reason I can think of for invoking physics in cases like this is that the player’s plan depends as much on physics as it does on magic, and I don’t think their cannonball trick would work. The gunpowder imparts the same momentum to the shrunken, diminished-mass cannonball as it would to a regular bullet. When the cannonball’s original size and mass are restored, it still has that much momentum - which I imagine will carry it a few feet.
Fortunately my game group includes a very smart player with a master’s degree in physics, who is very quick at computing such things. I would absolutely trust her estimate of how far the cannonball would go.
I would say that using modern physics in fantasy is not always a good idea. Depends on the setting I suppose.
In DnD there are a lot of concepts taken from premodern physics like the four elements, flogiston(even though it is completely different from what it was in the real world), alchemy is present too I suppose. So why would you insist on mkdern physics?
Inversing this gets really fun: enlarge spell on a tungsten/mithril bearing or toothpick. Pack enough charge to fire it out of an actual piece of siege equipment, hello nearly relativistic projectiles. Ship or battlement mounted rods from God.
"We strategically position our ship to ensure the flight path of the projectile happens in 6 second intervals, allowing for a near perfect rhythm of enlarge chanting. We keep three wizards and a wild magic sorcerer near each of our cannons.
We don’t lose fights often, no, why do you ask?"
Unfortunately after a single fire the force tosses the ship onto its side and is sinking
Firing even a 42lb cannon wouldn’t capsize a decently large ship. A 42lb projectile at 1700 ft/s carries like 425 million joules of energy. Then shrink that mass down from 42lbs to 0.5 lbs and let conservation of energy multiply the and whatever is in its flight path is going to have a really bad day. Like a “half a pound traveling at 0.6% of C” level of bad day.
With magic metals like mithril you can probably make a siege cannon of at least double the poundage. Modulate the load and use a tungsten wire instead of a toothpick, and you make a plasma weapon. You would need wizards dedicated to calculating the firing solutions to ensure you don’t miss your shots. Einstein would be the deadliest mother fucker on the Sword Coast.
Well, the cannon only needs to produce enough force to move a tiny cannon ball really fast.
The 6 second interval is to match the in game fight sequences, implying that the enlarge spell would finish casting as it impacts the enemy ship. All of that momentum suddenly comes to a grinding halt as the weight suddenly changes and the cannon ball rips the enemy ship to shreds
I came here to point out exactly this: If you only shrink the ball, without reducing its size, well… you’re gonna have problems carrying the ammo.
As a DM, I think I would let them both shrink and reduce the mass, and wait till they fired the weapon before invoking “conservation of momentum” and declaring that the cannon ball drops to the ground after about a meter.
Dunno about 5e etc. but in 1e, which I still play & DM, Enlarge and its reverse affect both the dimensions and mass of an object. So the cannonballs could be reduced to a mass a gun could shoot.
Well in that case, the reverse would also be true. So my barbarian can throw a cannonball at someone. How about if the mage readys the shrink spell to target the cannonball just as it leaves my hand? Conservation of energy would dictate that:
Decisions like these are what makes TTRPGs so fun, and I enjos every minute of these sort ot discussions.
Throwing a shrunken cannonball would work the same as shooting it out of a gun. If you throw an object that weighs one ounce at the time, it flies away with the amount of energy it took to accelerate an object that size to whatever velocity you give it. When the shrinkage magic stops, its mass returns to normal. This doesn’t change the amount of momentum the barbarian or the flintlock gave it. Think of it this way - if you get magically shrunk and you pick a flower, when the magic stops and you grow back to normal size the flower doesn’t also grow. It wasn’t affected by the magic and isn’t affected by the magic going away. Neither is anything else you acquire while shrunk, like momentum.
I noticed I didn’t even finish my previous comment, oops.
I do understand the physics, I work in engineering. I also looked at the spell desctiption from 5e D&D, it reduces the weight by 8, so the reduced weight would still be about 1-2kg. Not exactly a bullet yet.
Yeah, but D&D also has spells and potions of shrink / enlarge that don’t make players start drowning in atmosphere their lungs are too small to breathe or collapse under their own weight due to square cube law restrictions, so there’s definitely some magical physics at work in there.
You’re right, it’s very wonky, but that doesn’t validate not caring about physics at all, and the intellectual exercise of working it out is fun - which is the whole idea.
I see people make comments like this about shows, movies, etc. and I’ve never understood this line of thinking. I generally expect things to work the same as they do in real life unless it’s explicitly explained otherwise. Not sure if I’m the odd man out in thinking that way or what.
you sorta said it but an exception is places like the fae wilds, where you assume physics is only barely present enough to hold your organs together (hopefully)
No, you’re right IMO. Just because something is different from our world doesn’t mean all logical consistency is off the table. This idea is called versimilitude.
I had to look this up and I’m very surprised this is a borrowed word in English, at first glance I would assume it’s an evolution of “very similar to”