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Can you find the Earth in this picture? (1990)
Mostly Harmless
It's not rocket science, it's...
The Final Frontier
The abyss stares back

Earth (Latin: Terra) is one of eight[note 1] planets (specifically, a rocky one due to its solid surface, as with the rest of the first four planets, though the majority of the rock on our own planet is underwater) in the solar system orbiting a star, sometimes called Sol in random science fiction stories. While some believe there is intelligent life on Earth, others are too smart to really believe this.

Earth is also one of the four fundamental elements the Greeks philosophized about, the others being water, air and fire. Some people consider their philosophical ruminations to be somewhat naive. If you consider that they were doing said philosophizing a good few thousand years ago, and the four elements line up pretty well with solid, liquid, gas and plasma, perhaps they were not too far off the mark after all.

Fun facts about the Earth[edit]

  • Most of its inhabitants believe that the Earth is an oblate spheroid, a sphere just slightly appearing to have been "pushed in" a bit on the poles so the equator "bulges out" a bit more than on a perfectly spherical object. A highly vocal, loony, and nasally minority seem to think that it is flat, presumably squarish. This RationalWiki editor believes that it is a icosahedron.
  • Despite the fact that "Earth" means dirt, most of Earth's surface is covered by water. Curiously, while water is absolutely vital to continued life as humans know it, most of the Earth's water, if consumed in sufficient quantities, would kill humans.
  • The Earth's environment is seemingly quite fragile. However, since it is our God-given right to trash it[note 2], dammit we're gonna do it.
  • Everyone that has ever lived and everyone you have ever known has been from Earth. Deep, ain't it? Alien abductionists may disagree with this.
  • Earth lost out to Mars when all of the planetary bodies of the Solar System voted for Most Likely to Support Life. But, who's laughing now?
  • It is the only planet in the solar system not named after a Roman god / goddess in the English language.[note 3] However, the dwarf planets Haumea and Makemake are named after Hawaiian and Easter Island deities respectively, whilst Eris is named after the Greek goddess of discord.
  • It is the only known planet with RationalWiki, Minecraft, and feminism
  • It is also the only known planet with MRAs, the Religious Right and Scientology.
  • Its inhabitants are "Mostly Harmless"(caps intentional)
  • It has yet to create a sustainable civilization.[1][note 4]*Its inhabitants often work hard to distract from and derail progress towards greater consciousness.[note 5]

Quantitative facts about the Earth[edit]

  • Radius (volumetric mean) = 6371.0 km
    • Equatorial = 6378.1 km
    • Polar = 6356.8 km
    • Crust depth = 25 km (variable)
    • Mantle thickness = 2860 km
    • Core = 3480 km
  • Mass = 5.97×1024 kg
    • Atmosphere = 5.1×1018 kg
    • Hydrosphere = 1.4×1021 kg
    • Crust = 3.4×1022 kg
    • Mantle = 4.0×1024 kg
    • Core = 1.9×1024 kg
  • Distance from the Sun = 1.50×1011 m
  • Distance from the Moon = 3.84×108 m
  • Escape velocity = 11.186 km/s
  • Bond albedo = 0.306
  • Surface temperature = 288 K (15°C or 59°F)
  • Gravitational binding energy = 2.5×1032 J
  • Moment of inertia = 8.02×1037 kg m2
  • Density = 5514.8 kg/m3
    • Atmosphere (surface) = 1.217 kg/m3
    • Crust = 2700 kg/m3
    • Mantle = 4500 kg/m3
    • Core = 1.1E4 kg/m3


Unless someone gets it right much earlier, it's expected that the increase of the Sun's luminosity as it ages will cause an increased weathering of minerals, lowering atmospheric CO2 concentrations so much that in around 600 million years plants will begin to disappear as they will be unable to use photosynthesis.[2] No plants means no animals or fungi, and roughly 1 billion years from now, just bacteria will remain. Meanwhile, that very same increasing luminosity will also mess with the Earth's climate, causing either a moist or a runaway greenhouse effect which will cause the evaporation of the oceans.

In the former case, if the oceans boil away fast enough, Earth will be left as a pink and brown bone-dry wasteland somewhat resembling both Mars and Saturn's largest moon Titan with dunefields on its equator, salt-rich flats with scattered ponds marking the former place of the oceans, an oxygen-rich, Venus-like crushing, atmosphere at least for a while before such oxygen was absorbed by surface rocks, large volcanoes over mantle hotspots as both the only standing mountains, the others having been eroded away, and most visible signs of geological activity, and most of the little water just at the poles with maybe occasional rainstorms. In the latter case, which today is considered the most likely scenario[3], the slow evaporation of the oceans will saturate Earth's atmosphere with water vapor that will cause Earth's surface temperature to scream upward up to a hellish 1,600 K (1,330 °C; 2,420 °F), more than enough to melt its surface and wipe out any remaining life, and presumably later on once all that water was lost to space Earth would become a Venus-like planet.

Given that no oceans means no plate tectonics, heat may accumulate in Earth's interior until, as is thought to have happened on Venus, the planet's surface is covered in lava by extensive volcanism, killing whatever living things were still around. Alternatively, if plate tectonics stopped before the loss of oceans, erosion could transform Earth into a water-covered planet at least for a while.

Temperatures will eventually be so high that all life is expected to become extinct between at least 1.5[3] and 2.8 billion years from now[4], even if there's still the possibility in the case of the moist greenhouse happening of simple, hardy, life as extremophilesWikipedia surviving on environments as deep in Earth's crust, caves, etc. for a somewhat longer time[4]. It's also expected that Earth's magnetic field will go away within a similar timeframe and that, if you had not enough, Moon's recession may cause the Earth's obliquity to go nuts within a similar amount of time, still putting more constraints on whatever had managed to survive to those times[2].

Nothing more of interest except temperatures on the rise due to the aging of the Sun[note 6] is expected to happen until the Daystar exhausts its hydrogen supply 5 billion years from now and goes full red giant 2.6 billion years later, at which point it will absorb Earth but not before causing it to become a hell of a planet, including to have the Moon crashing back on Earth[2].

See also[edit]


  1. See the IAU's definition of what a planet is.
  2. Just ask former U.S. Secretary of the Interior James Watt
  3. For the sake of gratuitous pedantry, the names are in the Latin language, and borrowed into English. And technically, Uranus was a figure from Greek mythology, not Roman; his equivalent in Roman mythology was Caelus.
  4. For the record, a civilization becomes sustainable when it reaches Type I on the Kardashev scale, which, if they don't wipe ourselves out, should happen by 2200 CE. Pre-industrial Type 0 civilizations have a good chance of being wiped out by outside forces, while industrial/post-industrial Type 0 civilizations such as theirs have a good chance of wiping themselves out, especially when they inevitably discover that E=mc2.
  5. Examples: Pizzagate, Moon landing hoax, Westboro Baptist "Church" and, Creationism, New World Order, Homeopathy, 9/11 conspiracy theories, Holocaust denial, and Ku Klux Klan.
  6. Some calculations give a very small probability of Mercury's orbit going haywire sometime in the next billion years and crashing into another Solar System planet. While at first it was thought it could crash into Earth, later studies show that will not happen


  1. The Kardashev Scale Type 0: Why Earth is a Level Zero Civilization, Futurism
  2. 2.0 2.1 2.2 Even before then, ocean temperatures will be too high to allow adequate oxygen to be dissolved into the seas to allow fish and tadpole-stage amphibians to survive, and such warm-blooded creatures will be killed by sustained temperatures higher than their body heat, which means that birds and mammals will be long extinct. Future of the Earth. See also references therein
  3. 3.0 3.1 The end of life on Earth is not the end of the world: converging to an estimate of life span of the biosphere?
  4. 4.0 4.1 Swansong Biospheres: Refuges for life and novel microbial biospheres on terrestrial planets near the end of their habitable lifetimes