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In my game there is a high level wizard conjurer. He wants to cast a force wall around himself and the party, then use minor conjuration to create 10 pounds of the center of the sun, which he scried earlier,1 outside of his wall of force.

I'm wondering if this is even possible or if there's some rule limitation. If it is possible, can I have an idea of the amount of TNT this is? Would the explosion pass through the wall of force? What about the sound waves? Would the party go blind due to the explosion? What about the warforged?

They also had this idea to conjure a milligram of the centre of the sun right in front of a guy's face. How destructive would that be? Right now I've said no to conjuring it, but not because I don't want him to do it just because I want to know, will this blow up the country, a city, a small house, the surrounding area or what? And what about the milligram -- would that blow up the guy's head or the entire party, or do effectively nothing.


1 In my setting, there is a gateway to the plane of the gods in the centre of every star (the star itself isn't the gate, the star just has empty spherical area about 10m3 at its centre, large enough for the gate). During a plane war between the Nine Hells and the Deietic forces, the wizard scried on a Solar (the creature, MM p. 18) while it was transiting the gate inside the local star. And I just rolled poorly on its save against scrying. (The wizard was blinded by seeing the core of the sun while scrying, but enjoyed a Lesser Restoration afterwards.)

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    \$\begingroup\$ Please do not answer in comments on this site. Comments are for requesting clarification or suggesting improvements to the question. \$\endgroup\$ – doppelgreener Jun 2 '17 at 11:04
  • \$\begingroup\$ This is a physics question, not a dnd question. \$\endgroup\$ – Tyler S. Loeper Jun 6 '18 at 19:44
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This could go a number of ways, depending on how you rule it. I'll address the problems first.

What is an Object?

First and foremost, you have to consider what the definition of an Object is. The Minor Conjuration feature says...

[...]you can use your action to conjure up an inanimate object [...] no larger than 3 feet on a side and weigh no more than 10 pounds, and its form must be that of a nonmagical object that you have seen.

Herein lies the first problem. Is a blob of Fusile Hydrogen an object? Is it discrete enough that it is an 'object [he] has seen?'

The DMG (p.246) defines an Object as such:

[...]an object is a discrete, inanimate item like a window, door, sword, book, table, chair, or stone--not a building or a vehicle that is composed of many other objects.

By interpretation of this rule, no. It would not be. But, as a DM, this is still your call.

This also raises the question of "Can you conjure Part of an object, or only whole objects?" For example, could you conjure a chunk of a ship, because you've seen a ship before?

Is the Sun Magical?

In many realms, the sun is magical in nature. It's not a ball of fusing hydrogen...it's either a deity, or a hole in the fabric of the sky, or a massive portal to the Elemental Plane of Fire, or something else entirely. If the sun is magical, then he can't summon parts of it.

Assuming you're going to let this happen....

(Note: This section has been rewritten after errors in an equation I was using were pointed out to me. This altered the output of this answer dramatically)

If he summons a chunk of the sun, and assuming the sun is similar to our sun:

He can conjure a maximum of just over 30 cubic centimeters of solar core (a block about 3.1 cm to a side). This is because the Solar Core has a density of 150 grams per cubic centimeter, and Minor Conjuration can only create 10 lbs of matter (appx 4536g). This block of matter is held at a pressure of 26.5 Petapascals and a temperature of 15 million degrees C.

This seems absurd...but remember that this is a tiny piece of matter that is going to hurl itself apart the moment it is conjured (again, further evidence for it NOT being an Object). The amount of time it takes for that tiny wad of plasma to disperse would be extremely short. But, let's see what this does anyway.

While the sun's typical energy production is low (276.5 W/m3), that is still a lot of thermal energy that needs to go somewhere.

From here, it's time to break out the math. For simplicity's sake, we're going to assume the plasma behaves like an Ideal Gas. Because otherwise this gets completely insane. So, to determine the total available energy of 3ccs of solar matter, we can use this equation:

$$E = {\frac{3}{2}nRT}$$

Where E is energy, n is the number of moles of gas, R is the Gas Constant, and T is the temperature in Kelvin. At this scale, the difference between Celsius and Kelvin (273.15 degrees) is basically negligible.

At the heart of the sun, the composition is roughly 33% Hydrogen, 65% Helium, 2% Other. To determine how many moles we have, we're going to ignore the '2% other' (again, for sanity's sake) and just consider 33% Hydrogen, then just wave my hands and say the other 67% is Helium. Not strictly accurate, but close enough for my purposes.

So, starting with a total mass of 10lbs (4535.92g), we have 1496.9 grams of Hydrogen at 1.008 g/mole, and 3039 grams of Helium at 4.003 g/mole. This gives us a total of 1485 moles of Hydrogen and 759 moles of Helium. Total moles of matter: 2244

So, plugging in the numbers

$$E = 1.5 \times 2244\text{mol} \times 8.31\text{J/K} \times 150,000,000\text{K}$$

For a result of 4,195,719,000,000 Joules or 4.2 Terajoules

This is going to be a VERY large explosion. We aren't reaching the range of a nuke yet...but let's get some comparisons.

If every drop of fuel in a Boeing 747 went up at once, it would unleash 6.4 Terajoules. 12 Terajoules is what would be imparted to you if the International Space Station rammed you. 63 Terajoules (15x our drop of solar matter) was the Little Boy Atomic Bomb.

This is going to be an enormous explosion. Again, if you are permissive enough to allow that part of a star, an amorphous blob of highly dense, extremely energetic plasma, counts as an Object.

I would also mention...if you let a player conjure 'plasma' as an object...don't be surprised if they start trying to conjure up acids, toxic gases, and other amorphous substances.

But how many dice is that?

Per request of a comment, I will now attempt to render this blast in terms of dice of damage. Disclaimer: I am now applying physics to D&D rules. This segment is for entertainment purposes only (because anything caught in such a blast is dead anyway).

Tests conducted on medieval melee weapons show that a typical 1-handed swing of a Mace imparts about 130 Joules to a target. In D&D 5e, a mace deals 1d6 damage. So, to compute the dice of damage of direct exposure to the heart of a star, let's just assume damage scales linearly.

Our little spoonful of sunshine unleashed 4,195,719,000,000 Joules of energy. Divide by 130...

32,274,761,538 d6 of Fire Damage or, put simply, 32 giga-d6.

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    \$\begingroup\$ Comments are not for extended discussion; this conversation has been moved to chat. \$\endgroup\$ – nitsua60 Jun 2 '17 at 2:21
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    \$\begingroup\$ Comments purged. Use that chat for discussing this answer 👆 and reserve comments here for suggesting improvement and requesting clarification. At this point ~40 comments have been nuked on this post; we can't permit that much comment clutter even on super-fun stuff. \$\endgroup\$ – doppelgreener Jun 2 '17 at 10:42
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    \$\begingroup\$ I'm gonna be honest. By the end of your answer I really wanted to see the damage as measured in Md6 (i.e. millions of 6-sided dice). \$\endgroup\$ – josh314 Jun 4 '17 at 17:46
  • \$\begingroup\$ From my understanding of the lore the sun is a planet that was set on fire by Selune when Chauntea begged for help to create life on Abeir-Toril. That would make it not magical as if it were then it would be constantly sapping at here power. Which at the time after the War of Light and Darkeness would have been very taxing as she was greatly wounded. \$\endgroup\$ – Destiny Pugginty Feb 10 at 19:36
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Regardless of whether or not the player would be able to conjure bits of the sun, let's take a look at what would happen if he could.
After all, one of the joys of tabletop games is letting the players get away with things.

Most of what I'm about to walk through is based off Randall Munroe's research, specifically, information gleaned from XKCD's "What If?" series. The one I'm referencing in particular is #115, specifically note 5.
In note 5, he poses the question:

So what would happen if an AJ-shaped chunk of Sun-interior gets teleported to snowy Colorado, then we just left it there?

And answers it as:

The energy released would be somewhere between a large bomb and a small nuclear weapon.


Hardly exact numbers, but it gets us in the neighborhood.

From there, it's mostly a matter of figuring out how that relates to your pounds/grams/miligrams of solar material.

Let's get some numbers down:

  • Stanford lists the center of the sun as weighing about 160 g/cm^3, which is about 160,000kg/m^3
  • The volume of a human body is in the neighborhood of 100L, or about .1m^3

So, through a pretty simple calculation, we've got something like 16,000kg of solar material being roughly between 'a large bomb' and 'a small nuclear weapon'.
I'm going to interpret that as something between the GBU-43's yield of 11 tons of TNT, and the W-25 nuclear warhead's 1.5 kilotons of TNT.


Let's go for another nice round number, and say that the 16,000kg of sun is equivalent to about 100 tons of TNT, or about 100,000 kg.
This leaves us with a nice, round number -- each kg of sun is about equivalent to 1 ton of TNT.


So, to answer your implied questions about how destructive this material is, here's a few handy reference values:

$$ \begin{array}{l|l|l} \text{Mass} & \text{Equivalent mass, TNT} & \text{Approximate energy} \\ \hline 1600lb & 5\;tons & \text{Approx. similar to the Delft Thunderclap;} \\ & & \text{enough to devastate a small city} \\ 160kg & 1\;ton & \\ 1.6kg & 100kg & \text{More than most players 'need'} \\ 150g & 1kg & \text{About enough to obliterate a modern vehicle} \\ 80g & 500g & \text{About on par with a claymore antipersonnel mine} \\ 1mg & 1g & \text{Not much at all} \\ \end{array} $$


Now, bear in mind, that most of this energy is going to be undirected. I'd much rather stand in front of half-a-kilo of sun than in front of a claymore mine. As such, the destructiveness is going to be somewhat less than that of the comparable example.

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The other currently existing answers cover the physics of "What would happen if I transported ten pounds of solar core to the Earth's surface?"

The question of:

I'm wondering if this is even possible or if there's some rule limitation.

is more a matter of world-building and etiquette. It's world-building because in a fantasy setting there is no need to assume that the sun is a mass of incandescent gas as they say. In Middle Earth, it's a Maia, one of the Balrogs' good cousins; in Egyptian myth, it's Ra travelling over the world and then through the underworld in his boat. It is highly questionable what effect, if any, making a ten pound copy of a piece of something like that would have (if indeed it is even possible since pieces of divine bodies, avatars, or equipment would surely be magical and non-conjure-able.)

It's also etiquette in terms of respecting genre and your world-building efforts (or even just the world-building of a pre-packaged setting you happen to be using.) Sure, sometimes the whole point of a game (or a series of novels, like The Guardians of the Flame series) is to do a little deconstruction and see what happens when modernity infects a fantasy setting. But unless I as GM want that to be the point of my game-- and I will tell the players and get buy-in before that happens-- then all such attempts to make guns, or vaccines, or nuclear weapons, or teleported fusion sun-bombs are just going to fail.

You are well within your rights as GM to do this summarily.

For a more "Rules As Written" approach, the conjured object must be a non-magical object. The comments that have accrued during the composition of this post imply that stars are planar gateways, which sounds magical to me.

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For real world purposes, the density and temperature of the sun's core are such that ten pounds would probably be a pinhead size, which would very rapidly expand (with explosive force) to a volume of several hundred liters, while cooling as it expands to a temperature not far above room temperature.

It would not "nuke the entire continent" -- it's almost entirely hydrogen and helium, and the heat content of ten pounds of that gas (even at several million degrees) isn't even equivalent to a small nuclear device. Initially, it would be hot enough that most of its radiation would be in X-ray, but the expansion (and cooling per Boyle's Law) would take milliseconds at most, leaving the gas too cool to radiate in visible light at all. For some portion of the expansion, the gas would radiate brilliantly in visible, IR, and UV light, but that radiative period would be a fraction of the expansion time.

The effect would be much like looking into a strobe flash -- dazzling, but not blinding. The explosion would be smaller in volume than a Fireball spell, and likely do less damage. It would certainly not penetrate a Wall of Force (though if the Wall isn't closed, the explosive shock wave would likely wrap around the ends/top and lead to temporary deafness, like a nearby grenade explosion). The hydrogen would surely ignite, but (mixing with air only at a spherical interface) wouldn't produce an explosion as such, just a very quickly abating puff of invisible flame.

In other words, the caster would be much better served using a perfectly ordinary Fireball spell for the same effect.

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You are the GM and this is a fairly ridiculous idea. You have many ways to rationalize denying this.

  • The core of the Sun is so bright, he could not actually see anything there, just blank whiteness.

  • This is your setting, and this Sun is powered by positive energy and is thus magical/massless/.... and thus cannot be conjured.

  • As soon as it is created, the sun-core-material starts to rapidly expand. You declare that this explosion causes damage to the object and thus ends the conjuration immediately. (See also this question.)

  • With some Wikipedia diving I already know that he could conjure no more than 30 cubic centimeters of that material. Which is not a whole lot. It is Wiki, so take it with a grain of salt, but it also says that:

Theoretical models of the Sun's interior indicate a power density of approximately 276.5 W/m3, a value that more nearly approximates that of reptile metabolism or a compost pile than of a thermonuclear bomb.

So the fusion itself would not necessarily be that explosive/destructive. Also, it will stop the moment the whole thing starts to expand and the necessary pressure for fusion disappears.

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Props to you for this question. This was a fun one.

Given your specific scenario, this is valid

Let us accept the following premise:

  • Your Wizard has seen the center of the sun

  • The sun is not magical in your setting

  • Your Wizard is still alive

Then Minor Conjuration states:

This object can be no larger than 3 feet on a side and weigh no more than 10 pounds, and its form must be that of a nonmagical object that you have seen. The object is visibly magical, radiating dim light out to 5 feet.

This includes, but is not limited to, the following substances that a D&D Adventurer might encounter over their lifetime:

  • Lava

  • Radioactive uranium

  • Purple Worm Poison (DMG pg 268)

  • A 3x3x3ft cube of expensive spellcasting material components

They all fill the criteria of being a "nonmagical object" and can be created in a way where they weigh less than 10 lbs and occupy less than a 3x3x3 cube. As long as the adventurer has seen the above things, they can summon any of them.

The center of the sun is not any different, and so should be fair game for Minor Conjuration.

How would it play out?

If we are to use our Sun as the basis of this, then our friendly Wiki says:

  • The solar core is \$150\frac{g}{m^3}\$ dense

  • The solar core is 15 million degrees Celsius hot

  • The solar core is pressurized up to 3.84 trillion psi

Given this, we can calculate the mass of a 3x3x3ft cube of solar core, or the volume of one that weighs 10 lbs.

$$150\frac{g}{m^3} \times 27 \text{ft}^3 = 252 833.24 \text{lbs} > 10\text{ lbs}$$

$$\frac{10 \text{lbs}}{150\frac{g}{m^3}} = 30.24 \text{mL} < 27\text{ft}^3$$

So it seems like we would have a drop of the Sun's core instead of a cube of it. Great, so now how do we determine how it explodes?

Let's simplify our calculation by assuming the core behaves like an ideal gas, so that we can use the time-tested Ideal Gas Law equation:

$$PV = nRT$$

Then substituting all the variables to get the amount of moles in this drop of sun:

$$3.8\text{ T psi} \times 30.24\text{ milliliters} = n \times R \times 15,000,273.15 \text{ kelvin}$$

$$n = 6352\text{ moles}$$

And finding the kinetic energy of this many moles:

$$K = \frac{3}{2} \times nRT$$

$$K = \frac{3}{2} \times 6352\text{ moles} \times R \times 15,000,273.15 \text{ kelvin}$$

$$K = 1.2\text{ trillion joules}$$

Taking into account that one kiloton of TNT is about 4.2 trillion joules, this is equivalent to about 0.285 kilotons of TNT, or 0.285 million kilograms of the stuff.

Equation 12 of this research document shows you the overpresure and positive phase durations for any given weight of TNT. Overpressure is just the pressure caused by an explosion above ambient pressure, and positive phase duration is the time it took the pressure to rise above ambient pressure (usually milliseconds for short distances). These assume the blast happens in open air.

So, let's graph it!

graph

The equation that yielded that is:

$$P_\text{atm} = 0.986923 \times (6784\frac{W}{R^3} + 94\sqrt\frac{W}{R^3})$$

This is ridiculously explosive. The blast from this will still be felt and hurt people who are 45 kilometers away from the explosion site, where the overpressure is still 2.8 psi.

To put that in perspective, if you stood 45 kilometers away from the explosion, you would still witness:

  • collapsing residential structures

  • brick walls destroyed

  • people getting injured from the shockwave

  • possible fatalities

And if you were 20 kilometers away from the blast area, you would witness:

  • Reinforced concrete buildings severely damaged

  • Severe heart and lung damage

  • Limbs can be blown off

Let's extrapolate from there and guess that as you move closer to the blast radius, the further you move from "dead" to "even more dead."

Your Wizard now has the ability to conjure a powerful bomb at will.

Why did this happen?

Now, we draw a line between real world physics and D&D, because the players would be able to easily abuse a lot of things given how loosely D&D treats physics. For example, if you allowed them to see and replicate the following, you will run into lots of trouble:

  • Dark matter (comes with Dark Energy, also the ability to rip protons apart)

  • Antimatter (perfect destruction through annihilation, literally)

  • Exotic matter (ie, negative mass matter -- enables wormholes and FTL)

  • Neutron stars (if these things rotate, they can give off gamma ray bursts, which is worse than Disintegrate)

  • Black holes (sucked into oblivion)

Giving your players access to real world physics shenanigans will break your game.

You have stepped dangerously close -- if not outright over -- this thin line which gives your players a fun option to maybe sometimes use in their adventures, to a free "I win" button.

I advise you to really think hard if you want to go for "realism" here, or if you are willing instead to cause plot-induced amnesia to this particular Wizard.


My previous answer was off by a factor of 1 million, thanks to myself copying 3.8 trillion psi as 3.8 million psi instead. Thanks to @guildsbounty for spotting that error!

However, if you want to keep the previous result (as it was rather nice), you would need to scale the explosion back by a factor of a million. This means decreasing pressure and temperature by factors of a thousand each, but then it stops representing the Sun.

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I would argue that RAW lets you turn this into a flashbang and not much more. The conjured substance isn't actually the real thing. Dim glow and destroyed on damage both point to that. Let's rules lawyer the rest.

Ten pounds of solar core is a pretty potent pocket of power. It's super bright. It's under immense pressure. Left unchecked, it's going to do real damage. However, a good chunk of that damage comes from the rapid expansion of very hot gas. There's a size limit for this kind of conjuration, though. Once you've exceeded it, it's no longer a valid conjuration and it blinks out of existence.

The flash would undoubtedly be absurdly bright, but maybe less bright than you'd expect. The core of the sun isn't where the majority of the photons are produced. We don't have solid math on this that I can find, so we'd have to handwave it. Way brighter than daylight, but not funny physics bright.

Next up is the bang. 125 cubic feet of atmosphere has about the same mass as the conjuration limit, so after it blinks out, there's going to be a sudden vacuum pulling air back in behind the shockwave front ever so slightly harder than the shockwave presses outwards against the surrounding air. That much movement is going to be incredibly loud, but help limit the damage done by the shockwave itself.

So basically, high power flashbang. Rewards creativity without breaking the game.

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Let's assume that you allow this (which is an awesome idea by the way). In terms of balancing I would consider the following.

First of all you said that your wizard wants to cast force wall around himself? I assume that you mean the 5th level Wall of Force spell? If so, this means that every time your wizard uses Minor Conjuration to summon a piece of the sun he or she must either expend a 5th level spell slot or higher or take massive damage as the Minor Conjuration feature has a maximum range of 10 feet. What this means is that summoning the sun effectively becomes a player invented 5th level spell.

A 5th level Fireball spell would deal 10d6 fire damage (or half as much on a successful dexterity save) without any additional feats such as Elemental Adept or Empowered Evocation. A 6th level Disintegrate spell would deal 10d6+40 force damage on failed dexterity save, but can only target one creature and does no damage on a successful save. Your wizard's use of Minor Conjuration would deal area of effect damage (I'm assuming), a positive, but couldn't be scaled to do more damage as the actual spell slot being expended is for the shield, which is a negative as the damage wouldn't become greater if your wizard used a 9th level spell slot to shield him or herself from the piece of the sun.

Furthermore, Wall of Force lasts for up to 10 minutes with concentration but can be undone by Disintegrate.

Therefore, what I recommend is the following. Allow your wizard to use Minor Conjuration together with Wall of Force to summon a small piece of the sun, dealing 8d6 radiant damage with no save to all creatures within a 20 foot radius as well as disintegrating any small objects nearby, as well as the Wall of Force itself. You could say that while he or she can summon a piece of the sun, doing so is more difficult, even though it's within the limits of Minor Conjuration, and that therefore he or she can't summon it as effectively. This explains why the sun piece does less damage than a 5th level Fireball spell and why the shield disintegrates.

This lets your wizard have a cool moment without becoming too broken. You could give detail about how your wizard weaves the magic to summon a piece of the sun, dramatically slamming his or her staff on the ground at the last moment to shield the party as a blinding blast emanates 10 feet from the wizard, disintegrating parts of the nearby plants/walls, dealing damage to nearby creatures, with the shield barely holding up against the full blast before dissipating upon the blast's end.

Then, if you want, you could rule that your wizard would be able to invent a new spell if he or she cast it in this way first for X number of times (You can decide X, but it should be at least 10), as well as spending the time and gold to write it down in his or her spellbook upon completion of the experiments. Once your wizard officially learns this new spell, allow him or her to name it, then hand them a spell card with the following:

__________ (Insert Name Here)

5th-level conjuration

Casting Time: 1 action

Range: 10 feet

Components: V, S, M (a pinch of burnt powder made by crushing a gemstone)

Duration: Instantaneous

A small piece of the sun appears at a point you choose within range. All creatures and objects within a 20-foot-radius sphere centered on that point, except for creatures with 10 feet of you, take 9d10 + 20 radiant damage. If this damage reduces a creature or object to 0 hit points, it is disintegrated. When you cast this spell using a spell slot of 6th level or higher, the size of the blast increases by 10 feet and damage increases by 1d6 for each slot level above 5th.

Feel free to tweak the numbers, but I see no reason why a balanced homebrew spell can't be made to explain your wizard's request so long as you are willing to rule that because this is a fantasy universe where Barbarian Tieflings can tank Fireball spells, the magnitude of summoning a piece of the sun might not be quite as devastating as it would be in our own world.

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protected by Oblivious Sage Oct 22 '17 at 17:37

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