Planetary HP

[behaigo]

How would one go about calculating the HP of planet sized objects? 

[X-Codes]

Going with the idea that the earth is solid stone, it has about 7.5 billion HP.  The thing is, there's a clause in the PHB that notes that some weapons just aren't capable of damaging some objects, such as warhammers being wielded against a wall.  So, basically, you'd need Death Star magnitude weaponry just to be allowed a damage roll.

[veekie]

^^
Wasn't it hammers that worked on walls, but swords didn't?(unless they're katanas )

[behaigo]

That seems to be around where I was estimating.  How did you go about getting that number?  Also, weapon effectiveness won't be an issue  .

[X-Codes]

There's something in the PHB about breaking stuff, and it lists hardness and HP of objects.  Stone in 15 HP per inch, and the diameter of the earth in inches is about half a billion.

[veekie]

Though if you treat that health as the thickness alone, I think you'd only SPLIT the world, not pulverise it.

[Halinn]

Going with the idea that the earth is solid stone, it has about 7.5 billion HP.  The thing is, there's a clause in the PHB that notes that some weapons just aren't capable of damaging some objects, such as warhammers being wielded against a wall.  So, basically, you'd need Death Star magnitude weaponry just to be allowed a damage roll.

You shouldn't be ignoring the iron core of the planet, it having double the hit points per inch. The mesosphere would probably also warrant an increase in hit points relative to the lithosphere and asthenosphere, to account for greatly increased density.

[X-Codes]

Going with the idea that the earth is solid stone, it has about 7.5 billion HP.  The thing is, there's a clause in the PHB that notes that some weapons just aren't capable of damaging some objects, such as warhammers being wielded against a wall.  So, basically, you'd need Death Star magnitude weaponry just to be allowed a damage roll.

You shouldn't be ignoring the iron core of the planet, it having double the hit points per inch. The mesosphere would probably also warrant an increase in hit points relative to the lithosphere and asthenosphere, to account for greatly increased density.

Ok?  So what would that make the HP of the planet, then?

[Maat Mons]

Check out this thread. 

[Prime32]

Going with the idea that the earth is solid stone, it has about 7.5 billion HP.  The thing is, there's a clause in the PHB that notes that some weapons just aren't capable of damaging some objects, such as warhammers being wielded against a wall.  So, basically, you'd need Death Star magnitude weaponry just to be allowed a damage roll.

You shouldn't be ignoring the iron core of the planet, it having double the hit points per inch. The mesosphere would probably also warrant an increase in hit points relative to the lithosphere and asthenosphere, to account for greatly increased density.

The heavy metals sink to the bottom, so I'd assume the core contains things like adamantine or even obdurium.

[Halinn]

Ok?  So what would that make the HP of the planet, then?

http://en.wikipedia.org/wiki/Structure_of_the_earth
There is a sharp increase in density after 660 km. I will model that as 20 hp/inch, a slight increase over regular stone.
The core starts at 2890 km down, and goes to 6360. I will model this as iron, at 30 hp/inch. One might wish to model this as a more, given the pressures involved.

Given that these numbers are only half way through the planet, all lengths will of course be doubled.
1320 km * 39370 inches/km * 15 hp/inch = ~779 million
4460 km * 20 hp/inch = ~3.5 billion (would be ~2.6 billion at 15 hp/inch)
6940 km * 30 hp/inch = ~8.2 billion (would be ~10.9 billion at 40 hp/inch)
Total: 12,488,164,000 hp (~12.5 billion)