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It was the study of this planet's orbit that [[Albert Einstein]] claimed 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 574.10±0.65 arc-seconds per century relative to the inertial celestial reference frame. However [[Sir Isaac Newton|Newtonian]] physics alone would predict 531.63±0.69 arc-seconds (comprised of the gravitational pull of the other planets on top of [[axial precession]]). This gives a discrepancy of 42.47 arc-seconds between Newtonian models and observations.

It was the study of this planet's orbit that [[Albert Einstein]] claimed 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 574.10±0.65 arc-seconds per century relative to the inertial celestial reference frame. However [[Sir Isaac Newton|Newtonian]] physics alone would predict 531.63±0.69 arc-seconds (comprised of the gravitational pull of the other planets on top of [[axial precession]]). This gives a discrepancy of 42.47 arc-seconds between Newtonian models and observations.

Astronomers of the period hypothesized 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 supposedly accounts for 42.98 arc-seconds of precession and obviated the need to look for any unseen asteroids or innermost planet.<ref>https://www.math.washington.edu/~morrow/papers/Genrel.pdf

Astronomers of the period hypothesized 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 supposedly accounts for 42.98 arc-seconds of precession and obviated the need to look for any unseen asteroids or innermost planet.<ref name=Britannica/><ref>https://www.math.washington.edu/~morrow/papers/Genrel.pdf

, Accessed 13/12/16</ref><ref name=Britannica/><ref name=Hartnett>Hartnett, John. ''Starlight, Time, and the New Physics''. Creation Book Publishers, 2007, pp. 34-36. ISBN 9780949906687.</ref> The theoretical error in the relativity calculation is stated to be around 0.04 arc-seconds<ref name="">Iorio, L., ''On the possibility of measuring the solar oblateness and some relativistic effects from planetary ranging'', 2004</ref>). propagating the error on measurements (e.g. the positions and speeds of planets have some uncertainty in them so the Newtonian prediction has some error in it) through produces a theoretical value of 574±0.69 arc-seconds. This is within the supposed tolerance of the observations.

, Accessed 13/12/16</ref><ref name=Hartnett>Hartnett, John. ''Starlight, Time, and the New Physics''. Creation Book Publishers, 2007, pp. 34-36. ISBN 9780949906687.</ref> The theoretical error in the relativity calculation is stated to be around 0.04 arc-seconds<ref>Iorio, L., ''On the possibility of measuring the solar oblateness and some relativistic effects from planetary ranging'', 2004</ref>. propagating the error on measurements (e.g. the positions and speeds of planets have some uncertainty in them so the Newtonian prediction has some error in it) through produces a theoretical value of 574±0.69 arc-seconds. This is within the supposed tolerance of the observations.

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.