Wall of Force as a planet buster

[Volkov]

it might, but I think the amount of energy released will literally blow it apart too far to reform.
the initial impact will cause a massive explosion, greater then any nuclear weapon produced by man, but the thing is, the wall of force will remain, the planet will keep on going forward due to inertia and as it presses on it keeps on "impacting" the wall of force, creating more ridiculous releases of energy...

someone should do the math.

It wouldn't. Given that most of a planet is fluid, you wouldn't do crap to anything but the crust. Which would absorb the entire impact, and instantly break the wall with a strength check. (Every DM I know, including myself would rule that the planet would get a strength check in this situation)

[ericgrau]

People who keep thinking impact from fluids is harmless need to try cliff diving. Or at least jumping into a pool from a high diving board. Do a belly flop and it can hurt, almost like hitting a solid object. Not only would pushing the wall through the earth's mantle still cause enormous resistance, even pushing it through the earth's atmosphere at thousands of miles per hour would be an extreme impact. This is why I keep saying that if it gets destroyed at all, it won't even make it to the earth's surface.

EDIT: Btw, the math depends on a few unknowns, but I can say that we're talking about atomic bomb levels of energy here.

[taltamir]

People who keep thinking impact from fluids is harmless need to try cliff diving. Or at least jumping into a pool from a high diving board. Do a belly flop and it can hurt, almost like hitting a solid object. Not only would pushing the wall through the earth's mantle still cause enormous resistance, even pushing it through the earth's atmosphere at thousands of miles per hour would be an extreme impact. This is why I keep saying that if it gets destroyed at all, it won't even make it to the earth's surface.

absolutely true...
volkov... fluids just don't work the way you THINK they do. the impact with the fluid converts the same amount of energy into thermal energy. The reason planets don't crack open like rotten eggs is because in the REAL world we do not have "immovable" and we do not have "indestructible"..
and who cares what a DM would rule? this was a question of REAL LIFE SCIENCE not DM ruling.

As a DM I would say "the moment the wall touches the surface it magically accelerates to match its spell and now appears "immovable" compared to the planet.

EDIT: Btw, the math depends on a few unknowns, but I can say that we're talking about atomic bomb levels of energy here.

Atomic bombs don't even come CLOSE to the amount of energy we are talking about here.

[Volkov]

People who keep thinking impact from fluids is harmless need to try cliff diving. Or at least jumping into a pool from a high diving board. Do a belly flop and it can hurt, almost like hitting a solid object. Not only would pushing the wall through the earth's mantle still cause enormous resistance, even pushing it through the earth's atmosphere at thousands of miles per hour would be an extreme impact. This is why I keep saying that if it gets destroyed at all, it won't even make it to the earth's surface.

EDIT: Btw, the math depends on a few unknowns, but I can say that we're talking about atomic bomb levels of energy here.

The wall of force is too small to do much damage to the planet itself. We're talking 6 sextillion tons of ROCK and METAL. Three fourths of which is fluidic.

[taltamir]

The wall of force is too small to do much damage to the planet itself. We're talking 6 sextillion tons of ROCK and METAL.

EXACTLY (in regards to the mass)! that much mass has a LOT of kinetic energy, and it impacts an IMMOVABLE and INDESTRUCTIBLE object... all of said energy gets converted into heat. If it was an asteroid it wouldn't do a lot of damage, the asteroid will VAPORIZE from the impact with the GAS around the planet (known as air)... then its superheated vapour hits the ground creating a massive explosion, the earth is slowed down by an inconsequential amount as the superheated gas from the asteroid is accelerated to match the earths velocity (and direction). the wall of force will never be destroyed, will never match speeds, it simply forces its way through.

well, actually not all the energy gets converted, because as it is converted into heat the surrounding rock gets vaporised and no longer transfers the impact fully, it will tunnel through releasing massive amount of energy as it tunnels... it will have an entery hole of a few hundred feet, and an exit hole the other side that is a huge chunk of the planet.

Parts of the planet will fly forward, part of it will bounce the OTHER way, part of it will fly normal (perpendicular) to the axis of impact... the thing will be torn to shreds which will fly off in different directions.

[Volkov]

EXACTLY (in regards to the mass)! that much mass has a LOT of kinetic energy, and it impacts an IMMOVABLE and INDESTRUCTIBLE object... all of said energy gets converted into heat.

well, actually not all, because as it is converted into heat the surrounding rock gets vaporised and no longer transfers the impact fully, it will tunnel through releasing massive amount of energy as it tunnels... it will have an entery hole of a few hundred feet, and an exit hole the other side that is a huge chunk of the planet.

The planet would be slown down a lot as the fluid struggles against the wall, (which I would count as a strength check to break, and it would most certainly succeed instantly) So the planet will be moving at pitifully slow speeds as the comparatively tiny wall passes through.

[erikun]

At sizes like we're talking about, the fluidity of the material means nothing. The sheer gravity from an object the size of earth will keep it together, regardless of how much damage you do to its crust, or how many holes you bore through it with fantasy immobile devices.

I am, however, curious what is supposed to happen if a planet runs into a planet-sized wall of force in its orbital path. Would momentium allow it to "flow" around (more accurately, fall around) after impact, or would simply stop? Or would it ricochet, like a clumsy cue ball?

[taltamir]

The planet would be slown down a lot as the fluid struggles against the wall, (which I would count as a strength check to break, and it would most certainly succeed instantly) So the planet will be moving at pitifully slow speeds as the comparatively tiny wall passes through.

ok see, you are allowing the INDESTRUCTIBLE wall to BREAK.

if it can be broken it will never even impact the planet, it will break as soon as it hits the atmosphere and have NO noticeable effect on the planet whatsoever.

At sizes like we're talking about, the fluidity of the material means nothing.

correct, it might as well be solid.

The sheer gravity from an object the size of earth will keep it together, regardless of how much damage you do to its crust, or how many holes you bore through it with fantasy immobile devices.

that is just not how physics works. it will be torn asunder with chunks flying in every direction.

[absolmorph]

That won't work either, Pun-pun's attack will pour all of it's energy in too small a spot to destroy the earth.

When I'm more powerful than most deities and can give myself an ability to do anything, not to mention have arbitrarily high ability scores, I probably CAN.

[Superglucose]

At sizes like we're talking about, the fluidity of the material means nothing. The sheer gravity from an object the size of earth will keep it together, regardless of how much damage you do to its crust, or how many holes you bore through it with fantasy immobile devices.

That's not strictly true. If you hit something hard enough, it will break apart.

It's just a question of "how hard is hard enough?"

What I'm saying is: you're right, slowly boring holes into earth does nothing... but on the other hand sending it into a collision with a body that has the capability to reduce significant portions of the earth's crust from its current speed to 0? (keep in mind that Earth is moving at a pretty good clip)

[Volkov]

When I'm more powerful than most deities and can give myself an ability to do anything, not to mention have arbitrarily high ability scores, I probably CAN.

Unless you are using a spear the size of mount everest, no you are not destroying the planet, and even if you were strong enough to lift the spear, your tiny little hands would only manage to push it around.

[ericgrau]

At sizes like we're talking about, the fluidity of the material means nothing. The sheer gravity from an object the size of earth will keep it together, regardless of how much damage you do to its crust, or how many holes you bore through it with fantasy immobile devices.

I am, however, curious what is supposed to happen if a planet runs into a planet-sized wall of force in its orbital path. Would momentium allow it to "flow" around (more accurately, fall around) after impact, or would simply stop? Or would it ricochet, like a clumsy cue ball?

The planet would be unlikely to slow down noticeably against a 10'x10' wall of force. There'd only be an enormous explosion, whether the wall of force is destroyed in the atmosphere or bores all the way through and comes out the other side.

Against a planet sized wall of force OTOH the earth would splash like a drop of water, as the crust would not be nearly strong enough to hold it together. The backside would be relatively unaffected until it gets within a few hundred miles of the wall of force, at the same time that the front is already scattering into space. That's because the wall of force is moving faster than the vibrations travel through the earth. i.e., there would be ridiculous earthquakes on the far side of the earth, if it weren't for the fact that the wall of force reaches the other side before the quakes do.

[Lysander]

The planet doesn't have official stats as far as I know. So technically, if it comes up, it has whatever special abilities the DM rules it should have. It's sort of like asking why the universe doesn't fall if it doesn't have a fly speed.

[taltamir]

newtons three laws:

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

III. For every action there is an equal and opposite reaction.

Your planet hits an immovable and in destructive object the size of which is irrelevant (it really is irrelevant).
according to a quick google search:
the mass of earth is: 5.9742 × 10^24 kilograms
the speed of earth orbit around the sun is: 29658 m/s

to get the force which it exerts on the wall of force (use second law) you multiply the two.
F = 1.771828236x10^29 Newtons.
F = 177182823600000000000000000000 N.

the wall then applies an equal amount of force to the earth according to the third law.
the earth gets destroyed.

[erikun]

that is just not how physics works. it will be torn asunder with chunks flying in every direction.

Now might be a good time for an example.

Let's start with a rather large-sized rock. Say, one 3 feet/1 metre across. Let's drop it out of an airplane at 1,000 feet, causing it to hit a thick metal table (our Wall of Force in this example). How far would the pieces of rock scatter after the impact? 20 feet? 40 feet?

By comparison, Mars would be rock 1 foot across, aproximately 5 miles away at its closest. Venus is another rock 3 feet across, also around 5 miles away. These are the two closest gravitational forces, besides the pieces of Earth itself. In order for the Earth to be blown apart (and not reform) you need to overcome the mutual attraction of the Earth-pieces, or else it will just pull itself back together. We need to be moving at a low higher velocity (or a lot more mass) to blast the planet into pieces.


Also note that I was using my example of a "planet-sized" Wall of Force. If you're not using one that's 4,000 miles on each size, the impact will be a lot less dramatic - more like dropping the rock on a needle. Needless to say, a lot less "boom".

[Noble Savant]

Guys, why are we working hard to disprove this? Wall of Force has a range of close, teleporting is inaccurate, and space has no landmarks. The wizard teleports into space, tries to position himself correctly, and gets hit by a planet.

[taltamir]

Now might be a good time for an example.

if you want an example, take a gun and shoot a cantelope.
All your conjectures have nothing to do with physics, needles and planes etc are not indestructible or immovable, nor are your examples even accurate with the things you have described, you have obviously never thrown a rock from an airplane unto a steel table.

Guys, why are we working hard to disprove this? Wall of Force has a range of close, teleporting is inaccurate, and space has no landmarks. The wizard teleports into space, tries to position himself correctly, and gets hit by a planet.

technically this should happen every time anyone casts a WOF on the planet surface itself, because it is immoveable and indestructible (except specific magic) by definition.

[erikun]

if you want an example, take a gun and shoot a cantelope.

I highly doubt the second cantelope 5 miles away will keep the destroyed one from reforming.

Or are we talking about simply breaking up the crust on the planet? Because conventional expolsives could do that. So could any decent sized meteor, which would probably be easier to steer than trying to plot out the orbital path of the object you are standing on.

Heck, for that matter, the moon is nearby. You're pretty much guaranteed to shatter the crust if you could pull the moon into the earth.

[absolmorph]

Unless you are using a spear the size of mount everest, no you are not destroying the planet, and even if you were strong enough to lift the spear, your tiny little hands would only manage to push it around.

"A sarrukh may also grant the target an extraordinary, supernatural, or spell-like ability or remove one from it."
You don't have to grant yourself a published ability.

[taltamir]

Spoiler

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[ZeroNumerous]

That won't work either, Pun-pun's attack will pour all of it's energy in too small a spot to destroy the earth.

You don't know anything about Pun-Pun, do you? Instead of attacking the planet he gives himself the ability called "Explode Planet(Ex)" using Alter Reality. It, naturally, explodes planets. He then uses this ability targeting any planet he chooses.

[DaedalusMkV]

"A sarrukh may also grant the target an extraordinary, supernatural, or spell-like ability or remove one from it."
You don't have to grant yourself a published ability.

Indeed. The whole point of Pun-Pun is that he can do anything, ever. He wants to blow up a planet, he gives himself "Destroy Planet (Ex): Target planet within 5 LY explodes, doing 1000000d6 damage to everyone on it. Reflex half.". There are absolutely no limitations on the abilities he can give himself, which means saying "Pun-Pun couldn't do that" is always a false statement.

Note that the wall of force would deflect the planet long before it went right through unless it struck at an absolutely perfect angle directly at a point in which it would not be effected by its curvature. Similarly, it wouldn't hit with anywhere near the equivalent of the planet's kinetic energy; it's not big enough unless it's very close to the size of the planet. Besides, we're taking a situation which is impossible by the standards of modern physics and applying modern physics to it. I'm tempted to go with the "everything on the Prime is entirely stationary except the suns, which are overseen by the Gods and immune to magic" approach, since it makes so much more sense in this case.

[Project_Mayhem]

Indeed. The whole point of Pun-Pun is that he can do anything, ever. He wants to blow up a planet, he gives himself "Destroy Planet (Ex): Target planet within 5 LY explodes, doing 1000000d6 damage to everyone on it. Reflex half

Heh. The reflex half made me chuckle. Good time to have evasion.

And taltamir ... oh Science, your ms paint diagram caused me physical pain

[Megaduck]

10^32 Joules. For reference, the Sun's entire yearly output is roughly 10^34 Joules. It would take the entire energy output of the sun for about 4 days to build up enough energy to destroy a planet in a situation of perfect conversion, which is impossible. A railgun powerful enough to destroy a planet would need to be hooked up to multiple Dyson Spheres to work, barring a capacitor the size of a large sun.

Killing all human life on a planet? Easy. Destroying a planet? Really, really hard.

Edit: Ninja'd. Oh, so ninjad.

Ah, I see someone else knows where to find The Boom Table.

[Mikeavelli]

*Ahem*

Physics is a dame of culture and sophistication. She'll take you in, keep you warm at night, provide all kinds of insight into yourself and the world you never find on your own.

RAW is the wild, kinky sort of girl you'd never bring home to mother. She'll let you try new things, anything you can imagine, and more! She's flexible like a gymnist, and never has a headache.

that said, both of these ladies have one thing in common. they are possessive, jealous *****es! When you're going at it, you have to choose one or the other. Mixing the two does not lead to a clever or interesting theoretical situation, it leads to heavy, breakable objects getting thrown at your face from both sides.

[Dilb]

Your planet hits an immovable and in destructive object the size of which is irrelevant (it really is irrelevant).

The size is not at all irrelevant. If the WOF is motionless compared to the earth's orbital speed, and the WOF is completely unmovable, the impact will be like a fluid hitting a solid. Every realistic thing behaves like a fluid at that speed. As a fluid, it will tend to deform around the wall.

Bear in mind that a solid can't react to things faster than the speed of sound. For the earth, this means the edges of the earth can't move until the earthquake from the collision reaches them. It would take the WOF about three minutes to travel through the earth, while it takes earthquakes several hours to travel from the impact site to the sides. A standard size WOF is going to auger a small hole through the planet, not bring the entire thing to a halt. The earth will shake and cave in on the hole, and you'll be left with an earth with a crater at the entrance and exit points.

according to a quick google search:
the mass of earth is: 5.9742 × 10^24 kilograms
the speed of earth orbit around the sun is: 29658 m/s

to get the force which it exerts on the wall of force (use second law) you multiply the two.
F = 1.771828236x10^29 Newtons.
F = 177182823600000000000000000000 N.

the wall then applies an equal amount of force to the earth according to the third law.
the earth gets destroyed.

To get a force you multiply mass by acceleration, not speed. Multiplying the earth's mass by it's velocity gives you the earth's momentum. Momentum doesn't mean anything if you have a WOF, because a WOF ignores conservation of momentum: you can push off without an equal amount of momentum being created going in the opposite direction.

Even if that was a force, it wouldn't mean anything: destroying the earth requires energy. Any force is survivable as long as it's done over a short enough distance, or a brief enough period of time.

You can look up high speed videos of fruit getting shot: the fruit isn't dragged along with the bullet. The shockwave causes the fruit to explode in all directions, but the bullet is roughly continent sized, rather than smaller than a pin, like a regular WOF would be compared to a realistically sized planet. This apple isn't blown apart, for example, even though apples aren't held together by their own gravity, like planets are.

[RandomNPC]

Needs more Awaken Construct. Now it can take class levels, and call itself Ego.

I was thinking Mogo

[absolmorph]

*Ahem*

Physics is a dame of culture and sophistication. She'll take you in, keep you warm at night, provide all kinds of insight into yourself and the world you never find on your own.

RAW is the wild, kinky sort of girl you'd never bring home to mother. She'll let you try new things, anything you can imagine, and more! She's flexible like a gymnist, and never has a headache.

that said, both of these ladies have one thing in common. they are possessive, jealous *****es! When you're going at it, you have to choose one or the other. Mixing the two does not lead to a clever or interesting theoretical situation, it leads to heavy, breakable objects getting thrown at your face from both sides.

I'm sigging the part on RAW.

[JoshuaZ]

This isn't well-defined. Objects can't be immovable with respect to space. You have to be not moving with respect to something. Presumably when there's a big object like a planet nearby the magic somehow makes that the object chosen. But it isn't at all clear what this means. However, saying that the wall of force would stay in that point in space isn't well-defined unless you have a privileged coordinate system like in Aristotelian physics in which case the planet presumably won't be moving at all.

it might, but I think the amount of energy released will literally blow it apart too far to reform.
the initial impact will cause a massive explosion, greater then any nuclear weapon produced by man, but the thing is, the wall of force will remain, the planet will keep on going forward due to inertia and as it presses on it keeps on "impacting" the wall of force, creating more ridiculous releases of energy...

someone should do the math.

There's nowhere near enough energy to prevent the planet from reforming. This will be orders of magnitude more. Rough back of the envelope calculation: Earth has a mass of around 6 * 10^24 kilograms. In order to blow up the earth in a meaningful sense so it can't reform we need to accelerate a substantial portion of that to escape velocity (around 40,000 km/hour or about 10,000 m/s). Let's say we're trying to blow up about a third of the planet or around 2*10^24 kg. So the total energy to raise that to escape velocity is around (1/2)(10,000 m/s)^2(2*10^24 kg)=10^32 joules. That's how much energy we need.

Now how much energy will we get from this procedure? For simplicity assume a 20th level caster, so the wall has an area of 200 square feet or about 20 square meters. Now, assuming the wall stops everything it has going through it so it is reducing to 0 relative velocity a cylinder carved out of the earth with velocity around 50 km/s or 5*10^4 m/s (I'm assuming that the wall of force is stationary with respect to the sun because otherwise this isn't well-defined. I saw different estimates from googling but this is around the upper limit). The cylinder has length radius of the earth (6000 km) and base about 20 square meters so total volume is 6*10^6 * 20= about 10^8 cubic meters. The average density of the earth is around 5000 kg/m^3, but let's be generous and assume you get lucky and hit a core of about twice that density so around 10,000 kg /m^3 for a total mass of about 10^12 kg. So we need to know how much energy is in 10^12 kg going 5*10^4 m/s. So (1/2) * 10^12 kg * (5 *10^4 m/s)^2 = 5 * 10^20 joules. That's nowhere near enough energy. Since we need 10^32 joules, we are off by a factor of around 500 million. Since I rounded a fair bit this calculation could be off by as much as a factor of about a 100 either way, but that's still nowhere near the energy necessary.

If you redo this calculation with the wall of force being stationary with respect to the center of the galaxy you get around 400 times as much energy, so you would still be way off.

Edit: Also to be clear this is probably a wild overestimate since most of the mass in the cylinder won't actually get stopped but will move a bit to the sides and keep going only slightly slowed.

Edit: Just saw above uses radius of the earth when it should be the diameter. So the energy you get out is about twice as much as calculated above. Still much too small.

[Knaight]

EXACTLY (in regards to the mass)! that much mass has a LOT of kinetic energy, and it impacts an IMMOVABLE and INDESTRUCTIBLE object... all of said energy gets converted into heat. If it was an asteroid it wouldn't do a lot of damage, the asteroid will VAPORIZE from the impact with the GAS around the planet (known as air)... then its superheated vapour hits the ground creating a massive explosion, the earth is slowed down by an inconsequential amount as the superheated gas from the asteroid is accelerated to match the earths velocity (and direction). the wall of force will never be destroyed, will never match speeds, it simply forces its way through.\

No, nowhere near all of said energy gets converted into heat. The earth itself is not one object, and the rocks that compose the crust could distort to some extent, could be compressed to some extent due to being porous, and all sorts of other things that dramatically reduces the amount of energy converted to heat. Sure, rock is melted away in addition, but the wall would punch through the crust, as the planet wouldn't stop, and a tiny, tiny fraction of the kinetic energy from orbit is involved, as it breaks. Then it goes through the earth with a negligible change in speed. Now, life on the surface anywhere near the point of entrance or exit? Gone. Further away, probably gone. But the earth itself isn't affected much.

Let me put it this way. It makes an arc through the earth, of varying length, if optimized cutting around the surface (circular orbit guys, circular orbit. Circularish anyways.) So, lets give it the most volume possible. Its a 400 square foot wall, that goes for 1/2 the earth's circumfrence, about 13700 miles. Now lets look at that compared to the earths total volume, just for an understanding of how tiny this really is.