The Planet Earth

The Earth seen from Apollo 17.

The Earth seen from Apollo 17. (Photo credit: Wikipedia)

If one wants to create an imaginary thing that is as believable and realistic as possible, it pays to know as much as possible about as many real examples of that class of things as possible. This includes planets. I will use this page as a grab bag of odd, esoteric things I have had to find out about the Earth to reality check my ideas for other worlds. Some of them are less odd or esoteric. These are things that have helped me to get a better idea of scales of features on alien worlds based on the sizes of equivalent structures on Earth or in some way have helped me to visualize the worlds I create. This is a work in continuous progress. As I come across additional useful information, I will add it to the mess… In time, I intend to add pages on other planets in our Solar system, such as Venus, Mars, Jupiter, the Moon and moons of other planets, especially Titan. Information on the Sun and an overview of our entire Solar system will also be of use. For now, though, I present…

The Earth

  • Surface area: 510, 072,000 sq. km

Oceans

  • Pacific Ocean – 165,200,000 square kilometers(32.3% of surface)
  • Atlantic Ocean – 82,400,000 square kilometers(16.2% of surface)
  • Indian Ocean – 74,900,000 square kilometers(14.7% of surface)
  • Arctic Ocean – 14,000,000 square kilometers(2.75% of surface)
  • Arabian Sea – 3,864,000 square kilometers(0.758% of surface)
  • South China Sea – 3,447,000 square kilometers(0.676% of surface)
  • Caribbean Sea – 2,753,000 square kilometers(0.540% of surface)
  • Mediterranean Sea – 2,505,000 square kilometers(0.491% of surface)
  • Bering Sea – 2,269,000 square kilometers(0.445% of surface)
  • Bay of Bengal – 2,173,000 square kilometers(0.426% of surface)
  • Sea of Okhotsk – 1,603,000 square kilometers(0.314% of surface)
  • Norwegian Sea – 1,546,000 square kilometers(0.303% of surface)
  • Gulf of Mexico – 1,544,000 square kilometers(0.303% of surface)
  • Hudson Bay – 1,230,000 square kilometers(0.241% of surface)
  • Greenland Sea – 1,204,000 square kilometers(0.236% of surface)
  • Total Ocean Area: 359,900,000(~70.6% of surface)

Ocean trenches

  • The deepest known point in the Earth’s oceans is the Challenger Deep of the Mariana Trench in the western Pacific, 10,911 m (35,797 ft) below sea level.
  • The bottom of an oceanic trench is usually 3 to 4 kilometers(1.9 to 2.5 miles) below the depth of the surrounding sea bottom.
  • The seaward side of an oceanic trench typically has a slope of about 5°, while the landward slope tends to be about 10 to 16°.
  • Where sediment is particularly abundant or where the rate of convergence between plates is slow, “filled trenches,” may occur. In these locations,  subduction occurs, but the obvious bathymetric trench is obscured under all the muck.

Continental Margin

courtesy of Wikipedia

  Sediment
  Rock
  Mantle
  • The slope of the shelf is typically about 0.5°, with less than about 20 meters of vertical relief.
  • The width of the continental shelf varies. Active continental margins tend to have steep, narrow shelves, while passive continental margins will tend to have very wide, shallow shelves.
  • The outer(seaward) edge of the continental shelf lies at a fairly uniform depth of about 140 meters(460 feet).
  • The gradient of the continental slope typically varies from 1 to 10°, with an average of about 3°.
  • The gradient of the continental rise at the foot of the continental slope is typically about 0.5 to 1°.

Land

  • Asia – 44,900,000 square kilometers(29.9% of land/ 8.80% of surface)
  • Africa – 30,300,000 square kilometers(20.2% of land/ 5.94% of surface)
  • North America – 24,700,000 square kilometers(16.5% of land/ 4.84% of surface)
  • South America – 17,800,000 square kilometers(11.9% of land/ 3.49% of surface)
  • Antarctica – 5,400,000 square kilometers(3.60% of land/ 1.06% of surface)
  • Europe – 3,800,000 square kilometers(2.53% of land/ 0.745% of surface)
  • Australia – 2,966,155 square kilometers(1.98% of land/ 0.582% of surface)
  • Total land area(including inland water and Antarctica): 150,100,000(~29.4% of surface)

Lakes

Areas in square kilometers

  • Caspian Sea – 370,990
  • Lake Superior – 82,100
  • Lake Victoria – 69,463
  • Aral Sea – 64,100

Heat Flow through crust

Global map of the flow of heat, in mW/m^2, from Earth's interior to the surface. Cropped from the original figure in Davies, J. H., & Davies, D. R. (2010). Earth's surface heat flux. Solid Earth, 1(1), 5-24. Authors J.H. Davies and D.R. Davies. Licensed under Creative Commons Attribution 3.0 Unported.

Global map of the flow of heat, in mW/m^2, from Earth’s interior to the surface. Cropped from the original figure in Davies, J. H., & Davies, D. R. (2010). Earth’s surface heat flux. Solid Earth, 1(1), 5-24. Authors J.H. Davies and D.R. Davies. Licensed under Creative Commons Attribution 3.0 Unported.

Average heat flow through Earth’s crust – 91.6 mW/m2* Heat flow through continental crust – 70.9 mW/m2* Heat flow through ocean crust – 105.4 mW/m2* Radiogenic heat production – 29.2-79.9 mW/m2*(I get 86.8 mW/m2 from Anders Sandberg…) Primordial heat loss – 23.4-58.5 mW/m2*

According to one source I’ve read, a planet’s plate tectonic lifetime may scale as mass0.7. This may be useful for figuring out the relative heat flow budget of other planets.

Magnetic field

Intensity – between 25,000 and 65,000 nanoteslas(0.25 and 0.65 gauss), averages about 31,000 nT(0.31 G).

North magnetic pole at 76° N, 101° W.

According to Anders Sandberg, magnetic field intensity of a planet may plausibly scale as sqrt(density/period).

Population history

World population(millions)

  • 10,000 B.C. – 1
  • 5,000 B.C. – 5
  • 2,000 B.C. – 27
  • 1,000 B.C. – 50
  • 0 A.D. – 200
  • 500 A.D. – 300
  • 1000 – 400
  • 1500 – 500
  • 1650 – 600
  • 1750 – 750
  • 1800 – 900
  • 1810 – 1,000
  • 1850 – 1,171
  • 1900 – 1,608
  • 1950 – 2.406
  • 2000 – 6,080

Gross World Product

This is based on J. Bradford DeLong’s excellent, “Estimating World GDP, One Million B.C. – Present.” I will only present the results of his preferred scenario(other results can be found by following the link. You know you want to…). Because his estimates of global population differ significantly from my previous source, I decided to present his population estimates along with GWP and per capita GWP. I considered removing the previous source, but decided that the differences could be as illuminating as the numbers themselves. There’s also a lot more fine-grained data here. Mmmm, data…

Gross World Product through the ages
Year Population GWP per capita(1992 International Dollars) GWP(billion 1992 International Dollars)
1 million B.C. 125,000 92 0.01
300,000 B.C.  1 million 92 0.09
25,000 B.C. 3.34 million 92 0.31
10,000 B.C.  4 million 93 0.37
8000 B.C. 4.5 million 96 0.43
5000 B.C. 5 million 103 0.51
4000 B.C. 7 million 109 0.77
Year Population GWP per capita(1992 International Dollars) GWP(billion 1992 International Dollars)
3000 B.C. 14 million 113 1.59
2000 B.C. 27 million 112 3.02
1600 B.C. 36 million 121 4.36
1000 B.C. 50 million 129 6.35
800 B.C. 68 million 143 9.72
500 B.C. 100 million 137 13.72
400 B.C. 123 million 130 16.02
200 B.C. 150 million 113 17.0
Year Population GWP per capita(1992 International Dollars) GWP(billion 1992 International Dollars)
1 A.D. 170 million 109 18.5
14 171 million 102 17.5
200 190 million 98 18.54
350 190 million 94 17.93
400 190 million 97 18.44
500 195 million 102 19.92
600 200 million 104 20.86
700 210 million 112 23.44
800 220 million 116 25.53
Year Population GWP per capita(1992 International Dollars) GWP(billion 1992 International Dollars)
900 242 million 131 31.68
1000 265 million 133 35.31
1100 320 million  124 39.60
1200 360 million 104 37.44
1250 360 million 99 33.58
1300 360 million 89 32.09
1340 370 million 109 40.50
1400 350 million 128 44.92
1500 425 million 138 58.67
Year Population GWP per capita(1992 International Dollars) GWP(billion 1992 International Dollars)
1600 545 million 141 77.01
1650 545 million 150 81.74
1700 610 million 164 99.80
1750 720 million 178 128.51
1800 900 million 195 175.24
1850 1.2 billion 300 359.90
1875 1.325 billion 429 568.08
1900 1.625 billion 679 1102.96
Year Population GWP per capita(1992 International Dollars) GWP(billion 1992 International Dollars)
1920 1.813 billion 956 1733.67
1925 1.898 billion 1108 2102.88
1930 1.987 billion 1134 2253.81
1940 2.213 billion 1356 3001.36
1950 2.516 billion 1622 4081.81
1955 2.760 billion 1968 5430.44
1960 3.02 billion 2270 6855.25
1965 3.336 billion 2736 9126.98
Year Population GWP per capita(1992 International Dollars) GWP(billion 1992 International Dollars)
1970 3.698 billion 3282 12137.94
1975 4.079 billion 3714 15149.42
1980 4.448 billion 4231 18818.46
1985 4.851 billion 4634 22481.11
1990 5.292 billion 5204 27539.57
1995 5.761 billion 5840 33644.33
2000 6.272 billion 6539 41016.69

That was a hell of a chart right there, that was. I would still recommend at least glancing at DeLong’s analysis. As with the variance between the population estimate I found previously and this one, the diversity in estimates of per capita GWP is instructive as to just how much play and uncertainty there is in such analyses. Personally, I’m a bit dubious as to just how well such analyses can be extended as far as a million years back. DeLong mentions a demographic transition after World War II. What kind of transitions might have occurred after the onset of agriculture or civilization? Still, I think this is interesting. You might find it easier to digest with a bit of salt, though.

4 Responses to The Planet Earth

  1. Realmwright says:

    Good info to begin with. In the near future I’ll have a post up on my blog http://damnspacebar.blogspot.com/ of other basic Earth Sciencey things like axial tilt, length of day/year (like people really need to be told), and the order/distance of planets in the solar system. I may also include the age of the universe, galaxy, solar system, and Earth.

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