Earth

== Notes ==
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{{reflist |30em |group="n" |refs=

<ref name="Aoki">The ultimate source of these figures, uses the term "seconds of UT1" instead of "seconds of mean solar time".—{{cite journal |last1=Aoki |first1=S. |title=The new definition of universal time |journal=Astronomy and Astrophysics |year=1982 |volume=105 |issue=2 |pages=359–361 |bibcode=1982A&A...105..359A |last2=Kinoshita |first2=H. |last3=Guinot |first3=B. |last4=Kaplan |first4=G. H. |last5=McCarthy |first5=D. D. |last6=Seidelmann |first6=P. K.}}</ref>

<ref name="apsis">aphelion = ''a'' × (1 + ''e''); perihelion = ''a'' × (1&nbsp;– ''e''), where ''a'' is the semi-major axis and ''e'' is the eccentricity. The difference between Earth's perihelion and aphelion is 5 million kilometers.—{{cite book|page=144|title=Probing the New Solar System|last1=Wilkinson|first1=John|year= 2009|publisher=CSIRO Publishing|isbn=978-0-643-09949-4}}</ref>

<ref name="epoch">All astronomical quantities vary, both [[Secular phenomena|secularly]] and [[Frequency|periodically]]. The quantities given are the values at the instant [[J2000.0]] of the secular variation, ignoring all periodic variations.</ref>

<ref name="hill_radius">For Earth, the [[Hill radius]] is <math>R_H = a\left ( \frac{m}{3M} \right )^{\frac{1}{3}}</math>, where ''m'' is the mass of Earth, ''a'' is an astronomical unit, and ''M'' is the mass of the Sun. So the radius in AU is about <math>\left ( \frac{1}{3 \cdot 332,946} \right )^{\frac{1}{3}} = 0.01</math>.</ref>

<ref name="jaes41_3_379">Including the [[Somali Plate]], which is being formed out of the African Plate. See: {{cite journal |first=Jean |last=Chorowicz |date=October 2005 |title=The East African rift system |journal=[[Journal of African Earth Sciences]] |volume=43 |issue=1–3 |pages=379–410 |doi=10.1016/j.jafrearsci.2005.07.019 |bibcode=2005JAfES..43..379C}}</ref>

<ref name="solar_energy">Aphelion is 103.4% of the distance to perihelion. Due to the inverse square law, the radiation at perihelion is about 106.9% of the energy at aphelion.</ref>

<ref name="surfacecover">Due to natural fluctuations, ambiguities surrounding [[Ice shelf|ice shelves]], and mapping conventions for [[vertical datum]]s, exact values for land and ocean coverage are not meaningful. Based on data from the [[Vector Map]] and [http://www.landcover.org/ Global Landcover] {{Webarchive|url=https://web.archive.org/web/20150326085837/http://www.landcover.org/ |date=26 March 2015}} datasets, extreme values for coverage of lakes and streams are 0.6% and 1.0% of Earth's surface. The ice sheets of [[Antarctica]] and [[Greenland]] are counted as land, even though much of the rock that supports them lies below sea level.</ref>

<ref name="space_debris">As of 4 January 2018, the United States Strategic Command tracked a total of 18,835 artificial objects, mostly debris. See: {{cite journal |url=https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv22i1.pdf |title=Satellite Box Score |journal=Orbital Debris Quarterly News |editor1-first=Phillip |editor1-last=Anz-Meador |editor2-first=Debi |editor2-last=Shoots |volume=22 |issue=1 |page=12 |date=February 2018 |access-date=18 April 2018}}</ref>

}}