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how much body does a planet have?


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In your Green Lantern thread, Greywind had Mogo's BODY as 84 but I think that's a touch on the low side. :)

 

Wikipedia puts the Earth's volume at 1.08321×10 to the 12th power. That's in cubic kilometers. HERO rulebooks will tell you the BODY of a hex of stone. I'd recommend doing the math then taking out about 5% because Earth isn't all solid stone.

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6 hours ago, archer said:

In your Green Lantern thread, Greywind had Mogo's BODY as 84 but I think that's a touch on the low side. :)

 

Wikipedia puts the Earth's volume at 1.08321×10 to the 12th power. That's in cubic kilometers. HERO rulebooks will tell you the BODY of a hex of stone. I'd recommend doing the math then taking out about 5% because Earth isn't all solid stone.

 

Body tend to be per hex/2m. Which would put Mogo a lot over just the simple 84 listed in his stats.

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1 hour ago, Greywind said:

 

Body tend to be per hex/2m. Which would put Mogo a lot over just the simple 84 listed in his stats.

 

Makes me think about this exchange

 



[The Falcon jumps out of hyperspace into a dense field of rocks and debris.]
Han Solo: What the—?
Luke Skywalker: What's going on?
Han Solo: Our position is correct, except, no Alderaan.
Luke Skywalker: What do you mean? Where is it?
Han Solo: Thats what I'm trying to tell you, kid. It ain't there. It's been totally blown away.
Luke Skywalker: What!? How?
Ben Kenobi: [grimly] Destroyed. By the Empire.
Han Solo: The entire star fleet couldn't destroy the whole planet. It'd take a thousand ships with more fire power than I've...

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Planets either have nearly infinity Body or the have between 50 and 80.

 

I forget the math on it, but it takes less than 100 Body to blow a planet sized hole through a wall, once you take into account a bunch of doublings.  But that’s in one shot, one attack.  A machine gun will never do it.  You need one big 90D6 attack.

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OK, I want to get this out there so I can stop thinking about it before bed. :)

 

One cubic meter of stone has 19 BODY. Assume that doubling the volume adds 5 BODY. Earth has a volume of ~10^21 cubic meters. That is about 70 doublings, which gives us 369 BODY for Earth.

 

Figuring out how much Damage Negation Earth has is left as an exercise for the reader.

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1 hour ago, IndianaJoe3 said:

Figuring out how much Damage Negation Earth has is left as an exercise for the reader.

 

Right. The earth's atmosphere is going to absorb a % of space-based energy attacks. A quick Google says that 22.5% of solar radiation "goes directly to the earth's surface and is absorbed."

 

So... 75% damage resistance to EB?

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1 minute ago, Chaon said:

 

Right. The earth's atmosphere is going to absorb a % of space-based energy attacks. A quick Google says that 22.5% of solar radiation "goes directly to the earth's surface and is absorbed."

 

So... 75% damage resistance to EB?

It's significantly more complicated than that.  That's for a very particular energy input distributed over an entire hemisphere, from outside the atmosphere.  Bundle that energy into a kilometer-thick death ray and you'll see vastly different results.  Bundle that energy into a different form, like kinetic energy or a different frequency on the EM spectrum or "cosmic energy" and you'll again see vastly different results.  Apply that energy to the planet at ground level and you'll see, you guessed it, vastly different results. 

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13 hours ago, Chaon said:

 

Right. The earth's atmosphere is going to absorb a % of space-based energy attacks. A quick Google says that 22.5% of solar radiation "goes directly to the earth's surface and is absorbed."

 

So... 75% damage resistance to EB?

 

How many D6 damage does sunlight do to us on the ground?  Even on the hottest days I don't think I take more than a point or two of Stun from being outside unless it's for a long time.  The Earth's atmosphere might just be +10 ED only vs sunlight.

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In the 5e rules (p. 448) I found that a hex of stone is 19 Body, and a hex of dirt is 10. I went to 15, also considering that the core is pretty dense.

 

The volume of the Earth is 1,097,509,500,000,000,000,000 cubic meters

 

A hex of dirt is 2mX2mX2m so 8 cubic meters.

 

When I divide 1,097,509,500,000,000,000,000 cubic meters by 8, I get 

137188687500000000000

 

(I divided the volume in meters cubed by 8 meters cubed to figure out how many square hexes are in the Earth.)

 

137188687500000000000  X  15 = 2,057,830,312,500,000,000,000 Body

 

(Solo was right!)

 

But don't forget you'll have to subtract the Def first (4 or 5?). 😝

 

PS: But when you think of it, how much Body do the humans alone have when you add it up? When you think of that...

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pbem's makes sense;  if anything it's low.  Ignore the oceans;  they just don't go deep enough to account for a notable fraction.  Drop down into the mantle...starts about 30 km deep and extends down until the outer core.  It's iron, magnesium, and silicon...which means 2 levels of DI.

 

Consider...HS Equipment Guide gives stats for a nuclear blast.  At ground zero, there's 20d6 BODY drain, 40d6 killing (20 each thermal and blast) and another 20 killing from winds.  So call it 150 or so BODY.  And it's like a pinprick on an elephant.

 

Anything where you're trying to talk scales like this...we almost always massively underestimate.  Ocean water is evaporated by the sun;  1 cm per day is reasonable, IIRC, for summertime.  So take the Sea of Cortez...the body of water between Mexico proper and Baja California.  It's a fairly regular shape...roughly 1000 km long by 100 km wide on average.  So on an average day, you get 10^6 m * 10^5 m * 10^-2 m evaporating off...or 10^9...1 billion cubic meters.  A day.   Or, if you prefer:

--1 billion tons of water.  

--264 billion gallons

--an acre-foot is an irrigation measure...1 foot deep by 1 acre (660 feet by 66 feet, who knows why).  So this is about 8 million acre-feet.  

--on the Web, I found an article from 2017 saying the city of Phoenix uses 2.3 million acre-feet a day...so this is enough water for the ENTIRE city for 3 days.

 

And that's one small arm of the ocean...that's not even, say, the Gulf of Mexico.  Much less the equatorial region of the Pacific.

 

Planetary scales are just plain IMMENSE.

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On 7/12/2020 at 5:17 PM, Greywind said:

 

Body tend to be per hex/2m. Which would put Mogo a lot over just the simple 84 listed in his stats.

 

I'd like to make it clear that I was joking by comparing the Mogo character to a real planet that'd take a Death Star to destroy.

 

When superhero characters are fighting Mogo the Green Lantern or Ego the Living Planet, the BODY which the characters have to overcome has to be low enough that the players aren't spending the rest of their lives in a gaming session trying to do 12d6 to it at a time. So for Mogo the character which the superhero PC's are fighting, an 84 BODY score is fine.

 

But if you have Mogo the planet in a Star HERO campaign, you're going to have to use something closer to pbemguy's estimated 2,057,830,312,500,000,000,000 BODY to make sure the players don't crash two or three starships into each planet they see in order to completely obliterate it.

 

So I guess a lot of the answer to the question posed in the original post is just exactly how JmOz is planning on using the planet in his campaign. If it is "Earth as a target to be completely obliterated", that's going to be different than "Earth as a WarWorld" which has engines on it so it can fly through the cosmos menacing fleets or other planets. And those will both likely be different than "Earth as a superhero character".

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11 minutes ago, JmOz said:

Got curious on how much damage the destroy the world ray gun would actualy need...And more to the point what kind of defenses the FISS would need to block it...

 

 

I'd recommend starting with Missile Deflection.

 

Lord knows, the Earth didn't purchase enough....

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8 hours ago, archer said:

 

 

 

But if you have Mogo the planet in a Star HERO campaign, you're going to have to use something closer to pbemguy's estimated 2,057,830,312,500,000,000,000 BODY to make sure the players don't crash two or three starships into each planet they see in order to completely obliterate it.

 

 

...But what if the starships were traveling FTL when they kamikazed....

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Just now, pbemguy said:

 

...But what if the starships were traveling FTL when they kamikazed....

 

Well, if you are in Star Wars, ships jump into hyperspace which doesn't actually share any dimensions with the physical universe.

 

Wait....

 

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In Champions Beyond, the planet-devouring villain Astron, a living sapient asteroid field with an aggregate mass as larger as the Earth, has a BODY of 1,000. That's the same as the somewhat-larger planet-eating "Giant Space Amoeba" from the Hero System Bestiary. Astron has 12 PD/ED, defined as "Body Of Stone And Metal," which is Resistant, Hardened, and Impenetrable. The GSA's tissue is softer, total 30PD/40ED, but only 10 of each being Resistant, and without the other Advantages. However, the GSA also has 75% Physical and Energy Damage Reduction, defined as "Too Big To Hurt." Comparison-wise, the GSA is one coherent mass, while Astron is an aggregate of smaller objects, which could affect how they take damage.

 

I also want to note that for game purposes, Hero books often simplify the damage from tactical nuclear weapons as 20d6 Killing with MegaArea of Effect. Attacking a planet specifically to destroy it rather than devastate its surface, e.g. targeting its core, I wouldn't deal with AOE, treating the planet just as a single "character." Weaponry to actually demolish the planet would probably have to be designed for that purpose -- just throwing a lot of nukes at the surface wouldn't do it.

 

On that basis, I would consider it balanced to give an Earth-sized planet 1,000 BODY, with DEF as Astron above, but with Damage Reduction as per the Giant Space Amoeba. That should make it possible to destroy with a massed barrage of the right kind of weapons, but it would be a challenge. Something like the Death Star that could do it in one relatively short blast would have to generate ridiculous energy... which of course is what it does. ;)

 

IMHO, YMMV etc.

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It might be useful to look at the problem from the other end - what, "attacks" has the Earth survived? The biggest one coming to mind is the Chicxulb Impact. This was estimated at between 10^24 and 5*10^25 joules, which works out to  86 DC (if I've done the math right). While that devastated the biosphere, it wasn't even close to enough to destroy the planet.

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6 hours ago, IndianaJoe3 said:

It might be useful to look at the problem from the other end - what, "attacks" has the Earth survived? The biggest one coming to mind is the Chicxulb Impact. This was estimated at between 10^24 and 5*10^25 joules, which works out to  86 DC (if I've done the math right). While that devastated the biosphere, it wasn't even close to enough to destroy the planet.

 

Whether you got the math correct or not, thanks for the heroic effort in making the attempt.

 

This is exactly why I was thinking that any planet which I designed would have Missile Deflection....

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14 hours ago, IndianaJoe3 said:

It might be useful to look at the problem from the other end - what, "attacks" has the Earth survived? The biggest one coming to mind is the Chicxulb Impact. This was estimated at between 10^24 and 5*10^25 joules, which works out to  86 DC (if I've done the math right). While that devastated the biosphere, it wasn't even close to enough to destroy the planet.

 

Yeah but damage builds up fast in Hero. 

 

Imagine you're hitting a wall.  It's a massive wall, infinitely high and wide, the thickness of the Earth.  How much damage do you need to do to smash through it in one attack?  Well according to the Wall Body chart (Hero 5th ed revised, page 448), for stone and metal every doubling of thickness is +2 Body.  That lets you knock a hex-sided hole in a wall.  To double the width of the hole, to add +1 Body for each doubling.

 

According to Wikipedia, your impact crater is 150 km in diameter and about 20 km deep.  So if you've got one hex of stone (5 Def, 19 Body), you need 24D6 to destroy the hex.  You'd need an extra 18D6 to make the one hex-wide hole a kilometer deep.  You'd need about an additional 7D6 to make it 12 km (the midpoint between 8 and 16).  So that's a 49D6 attack to make the crater the right depth, one hex wide.  Now going out wide, we need an extra 9D6 to make it a km wide, and about 7.5 additional to get it to 150 km diameter.  So with Champions math, we need about 67D6 to get the impact that killed the dinosaurs.

 

To fully punch the Earth-sized hole in the infinite wall, we need a hole 12,700 km deep and wide.  One hex of stone is 24D6, + 18D6 for a km deep.  For a thousand km deep, that's +20D6 more, and then 8 more will get you 16,000.  70D6 to punch a one hex hole through the Earth.  +10 more for it to be a kilometer wide.  +10 more for 1,000 km wide.  +4 more for 16,000.  So 94D6 should be sufficient.

 

The 86 DC that you've calculated means that our figures are within 20 damage classes or so of each other.  That's a big difference, but it's not millions of damage classes different.  If you wanted to, you could say that planets (particularly important player character planets like Earth) could have extra defenses against attacks that are not Area Effect and Megascale.  So a 94D6 EB, Area of Effect Radius, MegaArea is a planet killer.  A "mere" 94D6 regular attack might just take out a large city or so.  Because of handwaviium.

 

 

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