Covering the area of the earth?

[fictionfan]

I'm asking how many Area Effect (in percent) would it take to cover the surface of the earth? The surface area of the earth is 5.1×108 km^2. The circumference of the earth at the equator is 24,901.55 miles (40,075.16 kilometers). The diameter of the earth at the equator is 7,926.41 miles (12,756.32 kilometers).

I am wondering about for if you wanted to cast a global enchantment or wanted to launch a kill all life missile.

[lexington]

Originally Posted by fictionfan

I'm asking how many Area Effect (in percent) would it take to cover the surface of the earth? The surface area of the earth is 5.1×108 km^2. The circumference of the earth at the equator is 24,901.55 miles (40,075.16 kilometers). The diameter of the earth at the equator is 7,926.41 miles (12,756.32 kilometers).

I am wondering about for if you wanted to cast a global enchantment or wanted to launch a kill all life missile.

Ooo, lets see.

pi r^2 = 5.1e8
r^2 = 1.62338e8
r = 12741

The radius you need is 12741 km or 1.4e7 yards.

2^x = 1.4e7
log2(1.4e7) = x
x = 23.7

So you need 24 levels total which is +1200%

[fictionfan]

Wow that's alot less then I expected thank-you.

[Anaraxes]

The joy of exponentials.

[Desthro]

I do believe 24 levels is insufficient, since the Earth is spherical, linear determinations to cover the entire surface are of the earth (a 3-dimensional object), with a 2-dimensional object, (a circle), you would need enough range to cover the distance from the Origin, (you) to the direct opposite side of the earth, otherwise your range will fall short and not cover the entire distance on the planet.


If your AoE radius in the above example is 12471 Km, your total distance covered in both directions on the planet is approximately 25,000 Km, when you NEED 40,075.16 Km total diameter in your AoE (at the Equator, we'll assume its spherical), to hit every last square inch of the planet. (Take a piece of string approximately 1/3rd to 1/4th the distance around the equator, stick it at the north pole with a string and then use a pencil to draw what you can hit, it'll miss a LOT of the planet. which is what would happen at the +1200% suggested)

you need log2(20,038,000) of AoE, which is 24.xx ranks, so 25 ranks for a total of +1250% (close enough?)

[Christopher R. Rice]

Originally Posted by fictionfan

I'm asking how many Area Effect (in percent) would it take to cover the surface of the earth? The surface area of the earth is 5.1×108 km^2. The circumference of the earth at the equator is 24,901.55 miles (40,075.16 kilometers). The diameter of the earth at the equator is 7,926.41 miles (12,756.32 kilometers).

I am wondering about for if you wanted to cast a global enchantment or wanted to launch a kill all life missile.

GURPS Psionic Powers says Area Effect 23 should do the trick.

Ghostdancer

[lexington]

Originally Posted by Desthro

I do believe 24 levels is insufficient, since the Earth is spherical, linear determinations to cover the entire surface are of the earth (a 3-dimensional object), with a 2-dimensional object, (a circle), you would need enough range to cover the distance from the Origin, (you) to the direct opposite side of the earth, otherwise your range will fall short and not cover the entire distance on the planet.


If your AoE radius in the above example is 12471 Km, your total distance covered in both directions on the planet is approximately 25,000 Km, when you NEED 40,075.16 Km total diameter in your AoE (at the Equator, we'll assume its spherical), to hit every last square inch of the planet. (Take a piece of string approximately 1/3rd to 1/4th the distance around the equator, stick it at the north pole with a string and then use a pencil to draw what you can hit, it'll miss a LOT of the planet. which is what would happen at the +1200% suggested)

you need log2(20,038,000) of AoE, which is 24.xx ranks, so 25 ranks for a total of +1250% (close enough?)

Area of effect doesn't create a sphere. It covers a given area to a height of four yards. That the area is bent in this case shouldn't matter.

[David Johnston2]

Originally Posted by lexington

Area of effect doesn't create a sphere. It covers a given area to a height of four yards.

Where did you get that from? It sounds like a rule from Magic.

[lexington]

Originally Posted by David Johnston2

Where did you get that from? It sounds like a rule from Magic.

Basic Set page 101. Area is 2 yards in radius and 12 feet high unless otherwise specified. Generally when a height is specified it is four yards anyway.

[Dragondog]

The way I read Area Effect, the effect works to a certain distance away from you. This has to be the opposite end of the world to cover all of it.

Based on the numbers given by the OP, I get log2 (21,913,364) which still ends up as 25 levels.

Because the world is spherical (or small enough to cover all of it with the AE), rather than circular, there will be some overlap.

Some GMs may choose to simplify things and go by area alone, and ignoring the required radius.