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Named after the ruler of the Roman gods, Jupiter is large and bright enough to be seen by the naked eye. In fact it is the fourth-brightest object in the night sky, after the [[Sun]], the [[Moon]], and the planet [[Venus]].<ref name=arnett>Arnett, Bill. "[http://www.nineplanets.org/jupiter.html Entry for Jupiter]." ''The <s>Nine</s> 8 Planets'', April 10, 2005. Accessed March 3, 2008.</ref> Jupiter is conspicuous and easy to recognize. An observer carrying 7-power field glasses (of a type used for birding or hunting) will see a round disk that shines steadily. An observer with a small telescope should also be able to resolve the [[Galilean moons]], as [[Galileo Galilei]] himself did. They will appear, as they did to Galileo, as "stars" traveling in "formation" with Jupiter and changing their positions relative to Jupiter in a single night of observation.

Named after the ruler of the Roman gods, Jupiter is large and bright enough to be seen by the naked eye. In fact it is the fourth-brightest object in the night sky, after the [[Sun]], the [[Moon]], and the planet [[Venus]].<ref name=arnett>Arnett, Bill. "[http://www.nineplanets.org/jupiter.html Entry for Jupiter]." ''The <s>Nine</s> 8 Planets'', April 10, 2005. Accessed March 3, 2008.</ref> Jupiter is conspicuous and easy to recognize. An observer carrying 7-power field glasses (of a type used for birding or hunting) will see a round disk that shines steadily. An observer with a small telescope should also be able to resolve the [[Galilean moons]], as [[Galileo Galilei]] himself did. They will appear, as they did to Galileo, as "stars" traveling in "formation" with Jupiter and changing their positions relative to Jupiter in a single night of observation.

The [[Babylonia]]ns believed that their god [[Marduk]] set Jupiter in the sky to guide the stars.<ref name=nelson>Nelson, Clark. "[http://www.timeemits.com/HoH_Articles/399-Day_Mean_Synodic_Period_of_Jupiter.htm 399-day Mean Synodic Period of Jupiter]."  <http://www.timeemits.com/>, 2006. Accessed March 3, 2008.</ref> Jupiter might have had an influence in the invention of several ancient calendars, including the Mayan calendar, the Egyptian calendar, the ancient (pre-Hillel II) Hebrew calendar, and possibly the calendar in use (at least by the [[Seth]]ite generations of [[Adam]]) before the [[Great flood|Great Flood]]).<ref name=nelson/>

The [[Babylonia]]ns believed that their god [[Marduk]] set Jupiter in the sky to guide the stars.<ref name=nelson>Nelson, Clark. "[http://www.timeemits.com/HoH_Articles/399-Day_Mean_Synodic_Period_of_Jupiter.htm 399-day Mean Synodic Period of Jupiter]."  <http://www.timeemits.com/>, 2006. Accessed March 3, 2008.</ref> Jupiter might have had an influence in the invention of several ancient calendars, including the Mayan calendar, the Egyptian calendar, the ancient (pre-Hillel II) Hebrew calendar, and possibly the calendar in use (at least by the [[Seth]]ite generations of [[Adam]] before the [[Great flood|Great Flood]]).<ref name=nelson/>

The name of the Roman god derives from the Latin "dyeu-pater" and "ius-pater."<ref>http://www.etymonline.com/index.php?term=Jupiter</ref>

The name of the Roman god derives from the Latin "dyeu-pater" and "ius-pater."<ref>http://www.etymonline.com/index.php?term=Jupiter</ref>

== Rotational characteristics ==

== Rotational characteristics ==

Jupiter has a very short sidereal day of about 9.92 hours. However, its latitudinal cloud bands rotate at different speeds, and some of these appear to rotate retrograde. Astronomers once calculated the Jovian day from observations of the equatorial cloud band, but today they rely on the periodicity of Jupiter's magnetic field.<ref name=nasa3>Gierasch, Peter J., and Philip D. Nicholson. "Jupiter." World Book Online Reference Center. 2004. World Book, Inc. <http://www.worldbookonline.com/wb/Article?id=ar293080.> Hosted as "[http://www.nasa.gov/worldbook/jupiter_worldbook.html Entry for Jupiter]," World Book at [[NASA]]. Accessed March 3, 2008.</ref>

Jupiter has a very short sidereal day of about 9.92 hours. However, its latitudinal cloud bands rotate at different speeds, and some of these appear to rotate retrograde. Astronomers once calculated the Jovian day from observations of the equatorial cloud band, but today they rely on the periodicity of Jupiter's magnetic field.<ref name=nasa3>Gierasch, Peter J., and Philip D. Nicholson. "Jupiter." World Book Online Reference Center. 2004. World Book, Inc. <http://www.worldbookonline.com/wb/Article?id=ar293080.> Hosted as "[http://www.nasa.gov/worldbook/jupiter_worldbook.html Entry for Jupiter]," World Book at NASA. Accessed March 3, 2008.</ref>

== Physical characteristics ==

== Physical characteristics ==

== Magnetosphere ==

== Magnetosphere ==

Jupiter has a magnetic field about 14 times as strong as that of Earth. Specifically, its [[magnetic dipole moment]] amounts to 1.55 * 10²⁷ N-m/T, higher than that of any object except the [[Sun]]. It is so high, in fact, that by [[Russell Humphreys]]' model for planetary magnetic fields, Jupiter's field must have formed with ''all'' of its mass aligned for the maximum cumulative magnetic dipole moment, instead of the usual 25%. By this assumption, the magnetic dipole moment of Jupiter at creation must have been 1.79 * 10²⁷ N-m/T. The half-life of this field is longer than 31,500 Julian years.

Jupiter has a magnetic field about 14 times as strong as that of Earth. Specifically, its [[magnetic dipole moment]] amounts to 1.55 * 10²⁷ N-m/T, higher than that of any object except the Sun. It is so high, in fact, that by [[Russell Humphreys]]' model for planetary magnetic fields, Jupiter's field must have formed with ''all'' of its mass aligned for the maximum cumulative magnetic dipole moment, instead of the usual 25%. By this assumption, the magnetic dipole moment of Jupiter at creation must have been 1.79 * 10²⁷ N-m/T. The half-life of this field is longer than 31,500 Julian years.

This field tends to shield Jupiter from the [[solar wind]]. However, the field has also trapped large numbers of radioactive particles in a Van-Allen-like radiation belt<ref name=nasa3/> that actually encompasses the orbits of the seven innermost moons. The magnetic field extends beyond the far side of Jupiter for at least 700 million kilometers.<ref name=nasa3/>

This field tends to shield Jupiter from the [[solar wind]]. However, the field has also trapped large numbers of radioactive particles in a Van-Allen-like radiation belt<ref name=nasa3/> that actually encompasses the orbits of the seven innermost moons. The magnetic field extends beyond the far side of Jupiter for at least 700 million kilometers.<ref name=nasa3/>

== Ring system ==

== Ring system ==

Jupiter does have a ring, consisting of three components, called the halo, the main ring, and the gossamer ring. This ring lies entirely within the region occupied by the four innermost moons, and probably derives its substance from escaping dust from the two innermost moons, [[Metis]] and [[Adrastea]]. The average size of the ring particles is 10 microns, comparable in size to the particles in [[tobacco]] smoke.<ref name=nasa4>Harvey, Samantha. "[http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Rings Jupiter:Rings]." ''Solar System Exploration'', [[NASA]], February 7, 2008. Accessed March 3, 2008.</ref>

Jupiter does have a ring, consisting of three components, called the halo, the main ring, and the gossamer ring. This ring lies entirely within the region occupied by the four innermost moons, and probably derives its substance from escaping dust from the two innermost moons, [[Metis]] and [[Adrastea]]. The average size of the ring particles is 10 microns, comparable in size to the particles in [[tobacco]] smoke.<ref name=nasa4>Harvey, Samantha. "[http://solarsystem.jpl.nasa.gov/planets/profile.cfm?Object=Jupiter&Display=Rings Jupiter:Rings]." ''Solar System Exploration'', NASA, February 7, 2008. Accessed March 3, 2008.</ref>

==Shoemaker-Levy==

==Shoemaker-Levy==

In 1994, scientists were able to witness fragments of the comet Shoemaker-Levy 9 collide with Jupiter. These collisions laster for 6 days, starting on July 16 of that year, and was the first cosmic collision to be observed. During the impacts, at least 21 separate fragments with a size of up to 2 kilometers hit Jupiter, leaving scars in its atmosphere larger than several Earths.

In 1994, scientists were able to witness fragments of the comet Shoemaker-Levy 9 collide with Jupiter. These collisions lasted for 6 days, starting on July 16 of that year, and was the first cosmic collision to be observed. During the impacts, at least 21 separate fragments with a size of up to 2 kilometers hit Jupiter, leaving scars in its atmosphere larger than several Earths.

== Problems for uniformitarian theories ==

== Problems for uniformitarian theories ==

# Jupiter never ignited, though its magnetic field is four times as strong as its mass would normally predict.

# Jupiter never ignited, though its magnetic field is four times as strong as its mass would normally predict.

# None of Jupiter's 63 moons is gaseous. Therefore a key event in the nebular sequence did not take place.

# None of Jupiter's 63 moons is gaseous. Therefore, a key event in the nebular sequence did not take place.

# The four dwarf-planet-sized [[Galilean moons]] have vastly differing apparent geological "ages" coming from times estimated to be as disparate as ten million years to as recent as thirteen hundred (although the times cannot be fixed with any reliability).<ref>Fulbright, Jeannie. ''Exploring Creation with Astronomy.'' Apologia Educational Ministries, 2004.</ref>

# The four dwarf-planet-sized [[Galilean moons]] have vastly differing apparent geological "ages" coming from times estimated to be as disparate as ten million years to as recent as thirteen hundred (although the times cannot be fixed with any reliability).<ref>Fulbright, Jeannie. ''Exploring Creation with Astronomy.'' Apologia Educational Ministries, 2004.</ref>

# Many of Jupiter's outer moons move retrograde to Jupiter's own day.

# Many of Jupiter's outer moons move retrograde to Jupiter's own day.

Seven spacecraft, all from the [[United States]], have visited Jupiter thus far. First to do so was [[Pioneer 10]] (December 3, 1973), which suffered tremendously from the radiation belt but still provided the evidence for Jupiter's [[magnetosphere]]. [[Pioneer 11]] was next (December, 1974) and took far better images of Jupiter and its Great Red Spot.

Seven spacecraft, all from the [[United States]], have visited Jupiter thus far. First to do so was [[Pioneer 10]] (December 3, 1973), which suffered tremendously from the radiation belt but still provided the evidence for Jupiter's [[magnetosphere]]. [[Pioneer 11]] was next (December, 1974) and took far better images of Jupiter and its Great Red Spot.

[[Voyager 1]] (March, 1979) and [[Voyager 2]] (July, 1979) gave the first comprehensive views of Jupiter and the Jovian system, including the discovery of its rings, the discovery of four moons inside [[Io]]'s orbit, and the first extensive studies of the [[Galilean moons]].

[[Voyager 1]] (March, 1979) and [[Voyager 2]] (July, 1979) gave the first comprehensive views of Jupiter and the Jovian system, including the discovery of its rings, the discovery of four moons inside [[Io]]'s orbit, and the first extensive studies of the Galilean moons.

[[Ulysses]] (February 1992) made a brief flyby of Jupiter in order to place itself in polar orbit around the Sun. Nevertheless [[European Space Agency]] scientists used this opportunity to make further measurements of Jupiter's magnetosphere and the effect upon it by the solar wind.

[[Ulysses]] (February 1992) made a brief flyby of Jupiter in order to place itself in polar orbit around the Sun. Nevertheless, [[European Space Agency]] scientists used this opportunity to make further measurements of Jupiter's magnetosphere and the effect upon it by the solar wind.

[[Galileo Project|Galileo]] reached Jupiter in 1995. It released a probe to dive into Jupiter's atmosphere; that probe transmitted for nearly an hour before the tremendous pressures crushed it. Galileo's orbiter remained in the system for nearly eight years, through two extensions of its mission, and conducted the most extensive surveys of the Galilean moons to day. Eventually, with the craft low on fuel, mission planners dived it into Jupiter to prevent its possibly crashing into [[Europa]], rupturing Europa's ice sheet, and contaminating the liquid ocean that astronomers now suspect lies a mere 10&nbsp;km deep to the ice and could yet harbor [[extraterrestrial life]].<ref name=nasa3/>

[[Galileo Project|Galileo]] reached Jupiter in 1995. It released a probe to dive into Jupiter's atmosphere; that probe transmitted for nearly an hour before the tremendous pressures crushed it. Galileo's orbiter remained in the system for nearly eight years, through two extensions of its mission, and conducted the most extensive surveys of the Galilean moons to day. Eventually, with the craft low on fuel, mission planners dived it into Jupiter to prevent its possibly crashing into [[Europa]], rupturing Europa's ice sheet, and contaminating the liquid ocean that astronomers now suspect lies a mere 10&nbsp;km deep to the ice and could yet harbor [[extraterrestrial life]].<ref name=nasa3/>