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{{quotebox|Mercury has a very elliptical orbit. At its farthest distance from the Sun, it is nearly 50% farther than at its nearest distance to the Sun. <ref> [http://astroprofspage.com/archives/139 ] </ref> }}

{{quotebox|Mercury has a very elliptical orbit. At its farthest distance from the Sun, it is nearly 50% farther than at its nearest distance to the Sun. <ref> [http://astroprofspage.com/archives/139 ] </ref> }}

The [[precession]] of Mercury's eccentric orbit was detectable to 19th century astronomers.{{fact}}

The [[precession]] of Mercury's eccentric orbit was detectable to 19th century astronomers.<ref name=Wudka>Wudka, Jose. "[http://phyun5.ucr.edu/~wudka/Physics7/Notes_www/node98.html Precession of the perihelion of Mercury]." September 24, 1998. Accessed April 17, 2008.</ref><ref name=Britannica>"[http://www.britannica.com/eb/article-241978/Mercury Mercury: Mercury in tests of relativity]."  In "Mercury," ''Encyclopædia Britannica'', 2008. Encyclopædia Britannica Online. 17 April 2008</ref>

== Orbital oddities ==

== Orbital oddities ==

It was the study of this planet's orbit that [[Albert Einstein]] used to help confirm the [[General Theory of Relativity]].<ref>Testing general relativity [http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31277 European Space Agency] Accessed July 16 2007</ref><ref>Albert Einstein [http://www.phy.hr/ Fizički odsjek] Accessed July 16 2007</ref> Specifically, Mercury's [[apsis|perihelion]] precesses by 43 arc-seconds per century, or more than [[Sir Isaac Newton|Newtonian]] physics alone would predict from the respective masses of Mercury, the Sun, and the other planets. Astronomers of the period hypthesized either an [[Asteroid Belt|asteroid belt]] or another planet (which they named [[Vulcan (planet)|Vulcan]]) inside Mercury's orbit. Einstein's second-order correction to Mercury's orbit accounted exactly for the 43 arc-seconds of precession and obviated the need to look for any unseen asteroids or innermost planet.<ref name=Hartnett>Hartnett, John. ''Starlight, Time, and the New Physics''. Creation Book Publishers, 2007, pp. 34-36. ISBN 9780949906687.</ref>

It was the study of this planet's orbit that [[Albert Einstein]] used to help confirm the [[General Theory of Relativity]].<ref>Testing general relativity [http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31277 European Space Agency] Accessed July 16 2007</ref><ref>Albert Einstein [http://www.phy.hr/ Fizički odsjek] Accessed July 16 2007</ref> Specifically, Mercury's [[apsis|perihelion]] precesses by 5600 arc-seconds per century, which is 43 arc-seconds per century more than [[Sir Isaac Newton|Newtonian]] physics alone would predict from the respective masses of Mercury, the Sun, and the other planets. Astronomers of the period hypthesized either an [[Asteroid Belt|asteroid belt]] or another planet (which they named [[Vulcan (planet)|Vulcan]]) inside Mercury's orbit. Einstein's second-order correction to Mercury's orbit accounted exactly for the 43 arc-seconds of precession and obviated the need to look for any unseen asteroids or innermost planet.<ref name=Hartnett>Hartnett, John. ''Starlight, Time, and the New Physics''. Creation Book Publishers, 2007, pp. 34-36. ISBN 9780949906687.</ref><ref name=Wudka/><ref name=Britannica/>

Mercury has more or less no atmosphere, and many craters. <ref>John Gribbin, ''Companion to the Cosmos'' (Little, Brown & Company, 1996)</ref> It has no known moons.

Mercury has more or less no atmosphere, and many craters. <ref>John Gribbin, ''Companion to the Cosmos'' (Little, Brown & Company, 1996)</ref> It has no known moons.