A View from the Back of the Envelope top

Area
m2
Scale of some things
Landmarks
Length Area Volume
[ Scale | Other ]
Rough Draft

Conversions

unit m2
mile2 106 × 2.590
km2 106 × 1.000
hectare 104 × 1.000
acre 104 × 0.4047
yd2 100 × 0.8361
ft2 10-1 × 0.9290
in2 10-3 × 0.6452
barn 10-28 × 1.000
10 ×

Landmarks

yd2 - 1 m2 (+20%, ±<1%)
100 × 0.8361±<1%
100 × 1+20%, ±<1%

ft2 - one tenth m2 (+8%, ±<1%)
10-1 × 0.9290±<1%
10-1 × 0.9-3%, ±<1%
10-1 × 1
one tenth		+8%, ±<1%

acre - 4 thousand m2 (104 × 0.4 m2, ±<2%)
104 × 0.4047±<1%
104 × 0.4
4 thousand		±<2%
104 × 1/2
1/2 hectare		-24%, ±<1%
103 × 3-26%, ±<1%<
103-75%, ±<1%
104+147%, ±<1%

Earth's surface - 500 Mm2 (1015 × 0.5 m2, -2%, ±<1%)
1015 × 0.510 m2±<1%[Cow]
1015 × 0.5 m2
500 Mm2		- 2%, ±<1%

Notes

Currently in pre-first-draft state...
hunk of sorbent, charcoal
football tenis

From [Cow 235]:
 Earth area 5.10 × 1014
 continents 1.48, eurasia 0.536, africa 0.298, N&C Am. 0.238, SAm 0.179,
  antartica 0.149, oceania 0.089
 ice free land 1.33
 oceans 3.61, ice-free: Pacific 1.66, Atlantic 0.83, Indian 0.65, Arctic 0.14
 sea ice (ave) 0.33

Moon A: (1.74 × 106)2 * 4pi = 3.80 × 1013
Sun A: (6.96 × 108)2 * 4pi = 6.09 × 1018
Jupiter A: (7.14 × 107)2 * 4pi = 6.41 × 1016

skin: "The surface area of skin of an "average" adult is 1.8 m2" [Thermal Conditions][link broken]

Lungs: "The total surface of the alveolar membrane varies from 100 to 200 square meters," [lungs.htm] [confirmations][link broken]

Capilaries "Over 6000 M2 in body; 60,000 miles in length! " [ref]

A View from the Back of the Envelope
Comments encouraged. - Mitchell N Charity <mcharity@lcs.mit.edu> 

Doables:
  "circular mills": still used?  Blech.
  Re: Wire Ampacities and Kirchoff[link broken]
    10 gauge wire is 2.59mm, 12 gauge wire is 2.05mm, 
    14 gauge wire is 1.63mm, 16 gauge wire is 1.29mm, 
    18 gauge wire is 1.02mm, 

History:
  2003-Feb-04  Flagged 3 broken links.
  1999.Dec.14  Added Earth's surface landmark.
  1998.Aug.05  Added Doables section.
  1998.Jun.23  Added some landmarks.
  long ago     Begun.