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Pluto Should Be Reclassified as a Planet, Experts Say (sciencedaily.com)
The reason Pluto lost its planet status is not valid, according to new research from the University of Central Florida in Orlando. From a report: In 2006, the International Astronomical Union, a global group of astronomy experts, established a definition of a planet that required it to "clear" its orbit, or in other words, be the largest gravitational force in its orbit. Since Neptune's gravity influences its neighboring planet Pluto, and Pluto shares its orbit with frozen gases and objects in the Kuiper belt, that meant Pluto was out of planet status. However, in a new study published online Wednesday in the journal Icarus, UCF planetary scientist Philip Metzger, who is with the university's Florida Space Institute, reported that this standard for classifying planets is not supported in the research literature. Metzger, who is lead author on the study, reviewed scientific literature from the past 200 years and found only one publication -- from 1802 -- that used the clearing-orbit requirement to classify planets, and it was based on since-disproven reasoning. He said moons such as Saturn's Titan and Jupiter's Europa have been routinely called planets by planetary scientists since the time of Galileo.
"The IAU definition would say that the fundamental object of planetary science, the planet, is supposed to be a defined on the basis of a concept that nobody uses in their research," Metzger said. "And it would leave out the second-most complex, interesting planet in our solar system." "We now have a list of well over 100 recent examples of planetary scientists using the word planet in a way that violates the IAU definition, but they are doing it because it's functionally useful," he said. "It's a sloppy definition," Metzger said of the IAU's definition. "They didn't say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit."
"The IAU definition would say that the fundamental object of planetary science, the planet, is supposed to be a defined on the basis of a concept that nobody uses in their research," Metzger said. "And it would leave out the second-most complex, interesting planet in our solar system." "We now have a list of well over 100 recent examples of planetary scientists using the word planet in a way that violates the IAU definition, but they are doing it because it's functionally useful," he said. "It's a sloppy definition," Metzger said of the IAU's definition. "They didn't say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit."
Read the Wikipedia article on clearing the neighborhood. It's defined well enough and people know what it means. Claiming that "If you take that literally, then there are no planets, because no planet clears its orbit." is like pointing to the requirement that a planet must be round, and saying that if you take that literally, no planet is round. Yes, no planet is 100% round, but it's possible for a planet to be close to round or not very close to round, and the same goes for clearing the neighborhood.
The research that shows that nobody used this definition in the past is probably correct. But it doesn't help. Scientists can make up new definitions.
Furthermore, while it's also true that planetary scientists call lots of things planets, the report itself admits that they also use the term for moons. Nobody else is going to start calling Pluto a planet under a definition that also includes moons.
Yeah, and there are too many chemical elements (118) on the Periodic Table, so what we need is a new rule that limits the number of elements to a nice, easy-for-schoolkids-to-memorize list of between 8 and 12 "major elements". I don't care how you categorize it, we simply cannot have a never ending list of elements to include in our definition of reality.