|
8 months ago ::
Oct 09, 2012 - 12:33PM
#1
|
Date Joined:
Apr 13, 2011
|
Before anyone hassles me about my geekiness, remember you are posting on a DnD forum - pot, kettle and all that  And yes I realise "it's magic" often resolves any such arguments about realism, what with fireballs, flying dragons, etc. But still this amused me enough to do the maths. Potion of Diminution "You shrink to 10 percent of your normal size and weight" A regular human has a mass of 70kg, a density approximated to that of water of 1000kg/m^3, hence a volume of 0.07m^3. If you shrink to 10% of your normal size, that reduces your volume to 0.1% of your normal volume (as you shrink in 3 dimensions). Hence your volume becomes 0.00007m^3. Meanwhile shrinking to 10% of your normal weight, your mass becomes 7kg. This implies a density of 100,000kg/m^3. To put that into context, lead has a density of 11,340kg/m^3. So we're talking an order of magnitude more dense than lead. The core of the Sun is about the ballpark density we're talking. en.wikipedia.org/wiki/Density
|
|
|
|
8 months ago ::
Oct 09, 2012 - 12:37PM
#2
|
Date Joined:
Sep 30, 2006
|
I too watched mythbusters the other day.
|
|
|
|
8 months ago ::
Oct 09, 2012 - 12:38PM
#3
|
Date Joined:
May 27, 2012
|
Maybe, by "size" they are referring to "volume"; then it would be consistent.
The metagame is not the game.
|
|
|
|
8 months ago ::
Oct 09, 2012 - 12:45PM
#4
|
Date Joined:
Apr 13, 2011
|
Maybe, by "size" they are referring to "volume"; then it would be consistent.
Hmmm, good thinking. That would require height becoming 46% of normal. So a 2m human would become 92cm tall, about the size of a halfling.
|
|
|
|
8 months ago ::
Oct 09, 2012 - 1:50PM
#5
|
Date Joined:
Jan 30, 2007
|
Maybe, by "size" they are referring to "volume"; then it would be consistent.
Hmmm, good thinking. That would require height becoming 46% of normal. So a 2m human would become 92cm tall, about the size of a halfling.
I'm going to geekily point out that any "negative" effects (like being more dense than the sun, for example), would be pointed out.
If you are 6 feet tall and 200 pounds, after drinking the potion you would be 7.2 inches tall, and weigh 20 pounds. Where does the extra density go? Somewhere between dimensions if you want the hand-wave, but if you want the "rules" explanation, it's because people can figure out 10% easily.
I get where you're going at, but most people don't play D&D to play calculus. *looks up at your first post*
Salla, on minions: I typically use them as encounter filler. 'I didn't quite fill out the XP budget, not enough room left for a decent near-level monster ... sprinkle in a few minions'. Kind of like monster styrofoam packing peanuts.
|
|
|
|
8 months ago ::
Oct 09, 2012 - 3:24PM
#6
|
Date Joined:
May 18, 2002
|
For reference: en.wikipedia.org/wiki/Square-cube_lawOf course, someone instantly losing 90% of his mass would create an explosion large enough to level a very large city and probably also the closest city in any direction.
|
|
|
|
8 months ago ::
Oct 09, 2012 - 3:27PM
#7
|
Date Joined:
Apr 10, 2009
|
For reference: en.wikipedia.org/wiki/Square-cube_law
Of course, someone instantly losing 90% of his mass would create an explosion large enough to level a very large city and probably also the closest city in any direction.
Only if by 'losing' you mean 'converting into energy'. If by 'losing' you mean 'ceasing to exist
' - then you just get a loud bang and a big wind as the surrounding air moves into the void left by the disappearing mass.
There is no requirement for mass to be conserved in a magical universe.
---
And you know you made the density calculations much more complicated than you needed to (and, of course, the relative change is independant of the starting dimensions)
You should increase to 100 times your current density.
You drop to 1 / 103 of your current volume. You drop to 1/10 your current weight.
1/ 10 current weight in 1 / 103 current volume result in a 100-fold increase in density or 100,000 kg/m 3 (with the 'we are equal in density to water' simplification).
Not 'star core' density by far (actually more like 1 one-thousandth of star core density) - but far more dense than any normal matter and more dense than the core of the Earth (by a factor of 10).
Carl
|
|
|
|
8 months ago ::
Oct 09, 2012 - 3:35PM
#8
|
Date Joined:
Aug 22, 2007
|
The magic is the the explosion is teleported to the Plane of Fire where it dissapates harmlessly.
Any idiot mage can make a potion that shrinks you.
Only the smart ones make one that solves the density problem.
Orzel, Halfelven son of Zel, Mystic Ranger, Bane to Dragons, Death to Undeath, Killer of Abyssals, King of the Wilds.
Constitution Based Class for Next!
|
|
|
|
8 months ago ::
Oct 09, 2012 - 3:42PM
#9
|
Date Joined:
May 18, 2002
|
One tenth the size and one thousandth the weight is how it should be.
Our 200lb guy would drop to 7.2 inches and 0.2 pounds (a bit over 3 ounces).
|
|
|
|
8 months ago ::
Oct 09, 2012 - 3:45PM
#10
|
Date Joined:
Sep 26, 2012
|
In a lot of other places (in various rule books here and there) they do "more proper" weight conversions. Increasing by double in height and raising weight by a factor of 8. So you decrease in height to 10%, but weight to 0.1% Maybe dimunition could use some numbers that 'do' make more sense. Of course being a 'hand' tall and weighing 0.2 lbs (or 0.01kgs) might have its own issues. Which you could fix in other ways if you like. Bugs are prepared to deal with this issue in a variety of ways. But it also makes them relatively impervious to brutal falling damage and the like. How far do you want to take this? :P Also, since the person isn't minature forever, I kinda assume the mass isn't just 'lost' but must be kept somewhere (magically?). However, a 20lb - 7 inch hero will certainly crush any dimunitive mount that may have existed outside the dimunitive pot itself.well I'm 7 inches so I hop on a salamander and kill it outright - squiiiiiish. Oops. We tend to try to overlook things like that in the spirit of the rules/fantasy in our group even if a few of us are physics/math/engineering nerds. However, if your suspension of disbelief - wait what I'm 7 inches tall!? - is offended...fix it
Currently running a playtest, weekly, online D&D Next Session using a virtual table system called roll20.
|
|
|
