Earth

[[File:Pale Blue Dot.png|thumb|165px|Can you find the Earth in this picture? (1990)]][[File:The Earth seen from Apollo 17.jpg|thumb|165px|Mostly Harmless]]{{Geology}}
{{cquote|The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.
It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known.|||[[Carl Sagan]]<ref>''Pale Blue Dot: A Vision of the Human Future in Space'' by Carl Sagan (1994) Random House. ISBN 0679438416.</ref>{{rp|7}}}}
'''Earth''' (Latin: '''''Terra''''') is one of eight<ref group=note>See the IAU's [http://www.iau.org/static/resolutions/Resolution_GA26-5-6.pdf definition of what a planet is.]</ref> [[planet]]s (specifically, a rocky one due to its solid surface, as with the rest of the [[Mercury|first]] [[Venus|four]] [[Mars|planets]], though the majority of the rock on our own planet is underwater) in the [[solar system]] orbiting a [[star]], sometimes called [[sun|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 [[Greece|Greek]]s [[philosophy|philosophized]] about, the others being [[water]], [[Oxygen|air]] and [[Hell|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==
[[File:An EPIC Eclipse (cropped).gif|thumb|right|250px|Animation of 13 images, March 9, 2016, by NASA’s DSCOVR satellite showing the Earth's rotation, weather and lunar shadow in motion.]]
*Until the discovery of exoplanets, there was a great gap in planetary size between the largest-known terrestrial planet (Earth) and the smallest gas giant planet ([[Uranus]] based on mass and [[Neptune]] based on volume). Nobody had an explanation of why such was so. {{wpl|Super-Earth|A great variety of planets orbiting stars other than the Sun fill the range in mass and volume between Earth and either Uranus or Neptune|.}}  
*Most of its inhabitants believe that the Earth is a sphere, although it 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 earth|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, [[The dose makes the poison|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,<ref group=note>Just ask former U.S. Secretary of the Interior James Watt</ref> dammit we're gonna do it.
*According to one calculation, the Earth is close enough to the sun to be on the hot side of the habitable zone, but life (especially plants and cyanobacteria photosynthesizing carbon dioxide) prevents the climate from going haywire on the hot side.  
*Everyone that has ever lived and everyone you have ever known has been from Earth.  Deep, ain't it?  [[Alien abduction]]ists 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 [[Ancient Rome|Roman]] [[god]]/goddess in the English language.<ref group=note>For the sake of gratuitous pedantry, the names are in the ''[[Latin]]'' language, and borrowed into English. And technically, [[Uranus]] was a figure from [[Greece|Greek]] mythology, not Roman; his equivalent in Roman mythology was Caelus.</ref> However, the dwarf planets Haumea and Makemake are named after [[Hawaii]]an and [[Rapa Nui|Easter Island]] deities respectively, whilst Eris is named after the Greek goddess of discord.
*Since [[Pluto]] was demoted from status as a planet, Earth is the only planet in our solar system to not be depicted in the symphonic suite ''The Planets'' by Gustav Holst.   
*It is the only known planet with [[RationalWiki]], [[Minecraft]], [[feminism]], and the [[music]] of Mozart.
*It is also the only known planet with [[Reptile#Crocodilians|crocodiles]],  [[Men's rights movement|MRAs]], the [[Religious Right]] and [[Scientology|$cientology]].
*Its inhabitants are "[[The Hitchhiker's Guide to the Galaxy|Mostly Harmless]]"<sup>(caps intentional)</sup>
*It has yet to create a sustainable civilization.<ref>[https://futurism.com/civilization-type-0-living-in-a-subglobal-culture/ The Kardashev Scale Type 0: Why Earth is a Level Zero Civilization], ''Futurism''</ref><ref group="note">For the record, a civilization becomes sustainable when it reaches Type I on the {{wpl|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 [[Nuclear war|E=mc<sup>2</sup>]].</ref>
*Its inhabitants often work hard to distract from and derail progress towards greater consciousness.<ref group=note>Examples: [[Pizzagate]], [[Moon landing hoax]], [[ISIS]], [[Fred Phelps|Westboro Baptist "Church" and godh@tesf@gs.com]], [[Creationism]], [[New World Order]], [[Homeopathy]], [[9/11 conspiracy theories]], [[Holocaust denial]], and [[Ku Klux Klan]].</ref>

==Quantitative facts about the Earth==
{| style="width: 75%;"
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*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 = 5.97×10<sup>24</sup> kg
** Atmosphere = 5.1×10<sup>18</sup> kg
** Hydrosphere = 1.4×10<sup>21</sup> kg
** Crust = 3.4×10<sup>22</sup> kg
** Mantle = 4.0×10<sup>24</sup> kg
** Core = 1.9×10<sup>24</sup> kg
| style="vertical-align: top;" |
*Distance from the Sun = 1.50×10<sup>11</sup> m
*Distance from the Moon = 3.84×10<sup>8</sup> m
*Escape velocity = 11.186 km/s
*Bond albedo = 0.306
*Surface temperature = 288 K (15°C or 59°F)
*Gravitational binding energy = 2.5×10<sup>32</sup> J
*Moment of inertia = 8.02×10<sup>37</sup> kg m<sup>2</sup>
*Density = 5514.8 kg/m<sup>3</sup>
** Atmosphere (surface) = 1.217 kg/m<sup>3</sup>
** Crust = 2700 kg/m<sup>3</sup>
** Mantle = 4500 kg/m<sup>3</sup>
** Core = 11000 kg/m<sup>3</sup>
|}

==Future==

Unless [[List of predictions of the end of the world|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 CO<sub>2</sub> concentrations so much that in around 600 million years [[plant]]s will begin to disappear as they will be unable to use [[photosynthesis]], even if it has also been proposed plants could linger for much longer (up to 1.86 billion years if not even more, with the extra heat brought by a more luminous Daystar being what would kill them instead, and their extinction coinciding with the beginning of the runaway greenhouse effect as noted further down<ref name=plantdeath>[https://iopscience.iop.org/article/10.3847/PSJ/ad7856 Substantial Extension of the Lifetime of the Terrestrial Biosphere]</ref>.) 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.
<ref name=futureearth>[https://en.wikipedia.org/wiki/Future_of_the_Earth Future of the Earth. See also references therein]</ref> 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 with water molecules being destroyed by the Sun's ultraviolet radiation in the stratosphere, the hydrogen being lost to space while the much heavier oxygen remains and the process according to Peter Ward and Donald Brownlee on their work ''The Life and Death of Planet Earth'' producing storms far more powerful than any current one and the dwindling oceans becoming both hotter and saltier (as salt will remain) as time goes by, severely messing with the remaining life on them and at the end leaving just bacteria adapted to such conditions there too.

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 (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,<ref name=endtimes>[https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/end-of-life-on-earth-is-not-the-end-of-the-world-converging-to-an-estimate-of-life-span-of-the-biosphere/AB2EF73B7787EDFF94AFCC545EC31302 The end of life on Earth is not the end of the world: converging to an estimate of life span of the biosphere?]</ref> 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 [[hell]]ish 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 in the way described before and thanks to all the carbon dioxide locked up in rocks that such surface conditions would free Earth would become a Venus-like planet (ie, hellish but not as much.)

Given that no oceans could mean no plate tectonics, as water is often thought to be critical for it, 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<ref name=endtimes/> and 2.8 billion years from now,<ref name=swb>[https://arxiv.org/abs/1210.5721 Swansong Biospheres: Refuges for life and novel microbial biospheres on terrestrial planets near the end of their habitable lifetimes]</ref> even if there's still the possibility in the case of the moist greenhouse happening of simple, hardy, life as {{wpl|Extremophile|extremophiles}} surviving on underground environments as deep in Earth's crust, ice-rich caves especially those located at high heights (ie, in mountains) close to the poles, etc. for a somewhat longer time<ref name=swb/> and/or in the atmosphere, as had been thought to be happening in Venus. 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, both still putting more constraints on whatever had managed to survive to those times.<ref name=futureearth/>

Nothing more of interest except temperatures on the rise due to the aging of the Sun<ref group=note>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, [http://www.sciencemag.org/news/2015/09/good-news-earthlings-planet-mercury-probably-won-t-kill-us later studies] show that will not happen</ref> 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 destroying the planet in just minutes after 3,000 years of spiral-in to the Sun's innermost regions,<ref>[https://arxiv.org/abs/2304.07808 Residual eccentricity of an Earth-like planet orbiting a red giant Sun]</ref> but not before causing it to become a ''hell'' of a planet, including to have the [[Moon]] crashing back on Earth.<ref name=futureearth/><ref group=note>Alternative views include Earth surviving the red giant and {{wpl|Red clump|later}} {{wpl|Asymptotic giant branch|evolutive}} {{wpl|Protoplanetary nebula|stages}} {{wpl|Planetary nebula|of}} the Sun to end up orbiting the white dwarf Sun, but stripped down to its metallic core. See [https://ui.adsabs.harvard.edu/abs/1998ApJ...503L.151L here]</ref>

==See also==
*[[Age of the Earth]] — Yes, people really deny its age, hence this page's purpose of debunking that idea.
*[[Evidence against a recent creation]] &mdash; Evidence that our ball of dirt is really approximately 4.54 billion years old.
*[[Rotation of the Earth]]
*[[Earth Day]]
*[[Human]]s, one of the dominant species on this planet.
*[[Dog]]s, animals that one could argue are Man's equals in the food chain. 
*[[Cat]]s of all sizes, arguably the most bloodthirsty creatures on the planet.
*[[Goat]]s, the dominant species on this planet.

==Notes==
{{reflist|group=note}}

==References==
{{reflist|2|80%}}

[[Category:Astronomy]]
[[Category:Geology]]
[[Category:Geography]] 
[[Category:Planets]]

Categories: Astronomy, Geology, Geography, Planets