Pluto Planet Essay

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Throughout history the definition of planet has changed greatly. The Greeks defined a planet as an object that was a “wanderer” in the sky. This was to say that a planet was an object that changes position relative to the background stars.[3] This included the 5 planets visible to the human eye (Earth was not considered a planet) and sometimes included the Sun and Moon. The definition of planet was changed and reworked until 2006, when the current official definition was created. This definition is as follows: “A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood…show more content…
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Pluto has a radius of 1184km while Mercury, the smallest current planet, has a radius of 2440km. This appears to be a huge difference, but they are quite close in size when it is taken into consideration that Jupiter has a radius of 64911km. [3] The fact that Mercury is considered to be a planet, but Pluto is considered to small is a result of the fact that planets are generally thought to be large objects, but no official size requirement has ever been defined. The fact is that any definition based on size will be arbitrary, so the problem exists of picking a cutoff. Tim DeBenedictis proposes a very reasonable solution to this problem. He proposes that we set the cutoff for planetary size at 1000km. [3] This is as arbitrary as any other number, but picking 1000km has benefits. Firstly, this fits well with the fact that we use base 10 in mathematics. This also makes the number of planets 10 with Pluto and Eris being added to the eight that we currently have. This results in a reasonable and concrete limit on the size of

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