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Published online 3 June 2009 | Nature 459, 624 (2009) | doi:10.1038/459624a
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Quaternary geologists win timescale vote
Redefinition rescues once-threatened terminology from extinction.
In 2006, astronomers reached a decision on the planetary status of Pluto; now, geologists may have done the same for the status of the Quaternary, the time period in which humans evolved and live today. But, as was the case with Pluto, resolving this long-standing controversy has left some researchers feeling alienated.
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That Pluto decision is very likely not final. Pluto is still a planet. Only four percent of the IAU voted on the controversial demotion, and most are not planetary scientists. Their decision was immediately opposed in a formal petition by hundreds of professional astronomers led by Dr. Alan Stern, Principal Investigator of NASA?s New Horizons mission to Pluto. One reason the IAU definition makes no sense is it says dwarf planets are not planets at all! That is like saying a grizzly bear is not a bear, and it is inconsistent with the use of the term ?dwarf? in astronomy, where dwarf stars are still stars, and dwarf galaxies are still galaxies. Also, the IAU definition classifies objects solely by where they are while ignoring what they are. If Earth were in Pluto?s orbit, according to the IAU definition, it would not be a planet either. A definition that takes the same object and makes it a planet in one location and not a planet in another is essentially useless. That is why many astronomers, lay people, and educators are either ignoring the demotion entirely or working to get it overturned.
Regarding the Pluto controversy: I was recently in an elementary school classroom and there on the wall was a chart published by National Geographic that described the eight planets and associated dwarf planets and other solar system objects. http://science.nationalgeographic.com/science/space/solar-system The reclassification of Pluto, it seems, is an accepted part of the curriculum and new teaching materials have already been produced. These things happen. Scientists redraw old conclusions based on new evidence. I can't see how correcting an error, even if it means some level of relearning, is a bad thing.
Laura - Celestial objects are not living organisms, and how they are classified has always been based at least partially on their context. For example, Titan is bigger than Mercury but it is a moon because it orbits a planet (Saturn) while Mercury orbits the Sun. If Titan and Mercury exchanged places, they would also exchange designations. Nor is this business of demoting an object unigue: Ceres and the other large asteroids were initially considered to be planets, but one it became obvious that they were part of a large population of relatively small objects, they were reclassified. In fact, had people in the 1930's known the true size and mass of Pluto (it was initially though to be as big as Earth and massive enough to perturb the orbits of Uranus and Neptune but now is known to be much smaller than the Moon, as way too light to affect the gas giants), it may never have been designated a planet. -- A similar change in understanding is being reflected here.
To Thomas Keays: Nobody is requiring the teaching of only the IAU view, and there are plenty of educational materials being produced that still include Pluto. Others depart from the IAU definition and refer to dwarf planets as a subclass of planets, specifically small ones. Many teachers continue to include Pluto as a planet. It is disingenuous to teach only one interpretation as fact when that view is only one side in an ongoing debate. You say these things happen. I say these things--ie, the creation of nonsensical definitions by a tiny group of scientists in a process that violated its own bylaws--can be undone. Here is another lesson on planet definition that received a NASA award: http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/What_Is_a_Planet.html . This one presents both sides of the issue and asks students to come to their own conclusions on the issue. To Edward Schaefer: First, my name is Laurel, not Laura. Second, many astronomers do consider the large, round moons of planets as "secondary planets." That term dates back to the 19th century and is appropriate in that it acknowledges their being in a state of hydrostatic equilibrium. The demotion of Ceres was wrong as well since Ceres is also in hydrostatic equilibrium; however, the fact of it being spherical was not known to 19th century astronomers. Ceres and Pluto are not just "part of a population of small objects." The fact that they are large enough to be pulled into a round shape by their own gravity clearly distinguishes them from most shapeless asteroids and KBOs, which are held together by chemical bonds. Failing to acknowledge this crucial distinction is simply bad science.
Incredible to see the Pluto-is-a-planet (because it was discovered by an American) gang highjack this item! Please people, get over it! The decision has been made, by the acknowledged international organisation in question. Feel unhappy about that? Your problem only! And don't come with that crap again about 'only a minority voted'. Only a minority seemed to be really interested to come to the vote! If it was this important to you, you should have been there and have voted yourself. Every IAU voting member could have voted if he/she wanted. And those "many astronomers" and the public said to be opposing the vote result: this is almost solely an American phenomena. It has much to do with the fact that Pluto was the only of the former "planets" discovered by an American. The anti-movement regarding the IAU decision doens't have a strong international footing at all. And now back to the redefinition of the Quaternary, please!
It is a pity that all comments about the redefinition of the Quaternary are ruling about the Pluto?s controversy. This is a strange cocktail of planets and geology pointing to nowhere. Are there anybody interested in the Quaternary-Neogene debate? The new published by Nature contains the notice itself plus different opinions of people mainly against the recent redefinition of the Quaternary Period. Beyond this new definition are the International Union of Quaternary Research (INQUA) and the Subcommission on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS) of the IUGS. The democracy injected in science vote yes to the continuity of the term & concept ?Quaternary? as a Period in the geological time-scale. The rational and democratic exercise of science carried out by the ICS revokes the impeachment of part of the Neogene community against the term & concept of Quaternary. The Geological time-scale has been in continuous change since its first drawings in the early 1800s. Change is a matter of science, science itself is change always in development, and Geology is a Science, in addition of historical character. New worldwide incoming data allow the geological time-boundaries be more accurately dated year by year. Some people wanted to change our history and tell us a new one on the basis of a ?uniformitarism? of the geological terminology. In the note published by nature it can be read that the opinion of one person who lobbied against the ?Change? said the rules of science are ?being violated?. Talking about changes, the more ?unchanging position? has been that of the Quaternary Community maintaining the term & concept of Quaternary against the impeachment of part of the Neogene Community trying to behead a world-wide accepted Geological Time-Scale. Other person uses the definition of the platinum metre bar of the French Academy of Science (year 1799) to compare the Quaternary debate case. Please note that since 1960 the metre is defined to be equal to 1,650,763.73 wavelenght in vacuum of the radiation corresponding to the transition between the 2p10 and 5d5 quantum levels of the krypton-86 atom. There are more recent definitions of the metre in relation to the speed of light, but only recommended for very short quantic-scale distances. The definiton of the unit of length as changed at least six times since the earlier defintion of the meridian metre in the late eighteenth century. Better don?t talk about time. As aforementioned, Science is change, and definitions necessary are continuosly changing by the flux of new incoming data. Those looking for immovable concepts do not understand the Science and are not true scientists.
Nice one Pablo! "Those looking for immovable concepts do not understand the Science.." Science by its Nature is in a constant state of open revision -this is the only inviolable 'Law of Science'. This is what distinguishes it from Dogma, Creed and Religion. We must remain open to new ideas, new definitions, and must allow sufficient time to evaluate the results of changes to the nomenclature. If the scientific community becomes resistant to change, then science cannot proceed. And if a mistake has been made in the reclassification of Pluto or the Quaternary period, then the same willingness to engage in revision will ensure that mistakes are rectified in the light of persuasive evidence.