A matter of scale, or, Why you should be scared

Taner EdisDepartment of Physics, Truman State University

www2.truman.edu/~edis/

2008 Focus the Nation 2

Exponential Growth

• 1-2% per year population growth.

• 2-3% GDP growth. 3% ideal for US economists.

• Say volume used by humans grows by 2% every year

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2008 Focus the Nation 3

Baseline volume estimate

• Starting volume needed per person: 3 m height, 30 m2 area. A room ~ 100 m3.

• Ludicrous underestimate. But economists tell us to expect technological miracles. Human ingenuity will find a way.

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2008 Focus the Nation 4

How long to c?

• Pile everyone on top of each other. How long will it take for the volume occupied by humans to start growing faster than the speed of light?

a) Thousands of yearsb) Millions of yearsc) Billions of yearsd) Trillions of years

2008 Focus the Nation 5

Let’s calculate

V = V0 eat , where

a = ln 1.02 (2% growth)

V0 = 102 x 1010 = 1012 m3 (today)

Pack in sphere, radius r = 3 V1/3/4π

Set speed of expansion to c, the speed of light:

∂r /∂t = c = 1016 m/year

2008 Focus the Nation 6

a) Thousands of years

• The result, solving for t, is

t ≈ 5000 years• Remember, this is with ludicrously

optimistic assumptions.

• 2% growth is crazy. Human civilization is already at a scale where we have planetary effects.

2008 Focus the Nation 7

It’s the economists, stupid

“First thing we do, let’s kill all the lawyers.”

(Shakespeare, Henry VI, Act IV, scene II.)

economists.”–––––––––––––––––––––––––––––––