[meteorite-list] Scientists Debate Planet Definition and Agree to Disagree

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Sat, 20 Sep 2008 16:22:42 -0700 (MST)
Message-ID: <59715.>

Hello everyone:

The actual press release had contact information for all of the scientists
quoted here. If you have any interest in contacting them, please let me
know and I can send you contact information.


On Fri, September 19, 2008 3:28 pm, Ron Baalke wrote:

> http://www.psi.edu/press/archive/20080919planetdebate/
> Scientists Debate Planet Definition and Agree to Disagree
> Planetary Science Institute Press Release
> September 19, 2008 - Two years ago the International Astronomical Union
> (IAU) elected to define the term planet, restricting it to the eight
> largest bodies orbiting the Sun, and deleting Pluto from the list. The
> demotion of Pluto sparked considerable public controversy. Numerous
> planetary scientists and astronomers protested the IAU's definition as not
> useful, while numerous other planetary scientists and astronomers
> supported the outcome.
> Recognizing the need for further scientific debate on planet definition,
> more than 100 scientists and educators representing a wide range of
> viewpoints on the issue converged for three days on the Applied Physics
> Laboratory of Johns Hopkins University (APL) for "The Great Planet
> Debate: Science as Process" conference <http://gpd.jhuapl.edu/> last
> month. The conference was sponsored by NASA, APL, the Planetary Science
> Institute, The Planetary Society, and the American Astronautical Society.
> Different positions were advocated, ranging from reworking the IAU
> definition (but yielding the same outcome of eight planets), replacing it
> with a geophysical-based definition (that would increase the number of
> planets well beyond eight), and rescinding the definition for planet
> altogether and focusing on defining subcategories for serving different
> purposes. No consensus was reached.
> A sample of the opinions expressed by conference participants follows:
> "I was impressed with two things that came out of The Great Planet
> Debate meeting: first, that no one liked the IAU's definition of
> planethood, and second, that there are strongly divergent scientific
> opinions about what a planet is, with those who study orbits and those who
> study planets themselves seeing the matter very differently." said
> planetary scientist Alan Stern, currently a visiting scholar at the Lunar
> and Planetary Institute of Houston, Texas. "My view is that the
> dynamically based definitions are deeply flawed because they do not take
> into account any physical properties of the body in question, and give
> ridiculous results, for example classifying identical large objects in
> different orbits differently - so that even Earths are not always planets,
> which is crazy," Stern concluded.
> "Gravity forces large bodies to be round, whereas small bodies can be
> quite oddly shaped. But the proposed 'geophysical' definition of planethood
> based upon roundness uses a poor criterion because there is no good
> dividing line. Indeed, there are likely to be more intermediate solar
> system objects that are in the fuzzy 'roundish' area than there are
> objects that are clearly round. In contrast, the eight planets recognized
> by the IAU are significantly different from the numerous small objects
> that are classified as 'minor planets' (asteroids) in terms of both
> physical properties and their effects on bodies orbiting nearby," said
> Jack Lissauer, planetary scientist at NASA's Ames Research
> Center in Mountain View, California.
> "We all have a conceptual image of a planet. Therefore, we need a term
> that encompasses all objects that orbit the Sun or other stars," said Larry
> Lebofsky, Senior Education Specialist at the Planetary Science
> Institute in Tucson, Arizona. "The debate is a great teaching moment.
> Whether dwarf planets are grouped together with the classical planets is
> not as important as the process by which scientists arrived at their
> conclusions. Scientists look at the same information in different ways;
> there may be more than one 'answer'. Facts change. What we know now may
> not be what we know in two or three years. Learning to think critically
> and understanding how scientists organize facts to develop theories are
> lessons that will serve students for a lifetime."
> "The word 'planet' has a deep cultural context that cannot be decided by
> vote of a subset of astronomers meeting in a room somewhere, especially
> when that debate is rushed and the vote close", said William McKinnon, a
> Professor of Earth and Planetary Sciences at Washington University in
> St. Louis, and an IAU member. "The IAU should reopen the issue to
> electronic debate by the entire astronomical community. I am sure the
> outcome in that case, whatever it turns out to be, or even if it is
> concluded that no universal definition is necessary, would be more
> satisfactory to all parties," he said.
> "I believe the IAU definition correctly recognized the utility of a
> dynamical criterion, but that it needs clarification, not abandonment. In
> particular, 'clearing' the neighborhood should be replaced by the concept
> of 'dynamical dominance'," said Steven Soter of the American Museum of
> Natural History in New York.
> Jay Pasachoff, from Williams College, who is spending this year at
> Caltech studying Pluto's atmosphere, says, "I have long tried, in my
> textbooks, to reflect consensus rather than trying to legislate new
> terminology. I think that the IAU should have limited their decision to
> the administrative assignment of naming responsibility and not tried to
> make decisions for the general public. If third-grade students eventually
> decide that Eris, Makemake, Haumea, and their successors are too many to
> learn about, then a new consensus may emerge. In the meantime, let's let
> scientific discovery continue to take its course and let us hope to excite
> new generations of students with the new information that emerges."
> "I think the IAU made a mistake getting into the business of defining a
> widely used word, 'planet', and sowing confusion thereby. Scientifically,
> the useful discussion would be about categories of planets (e.g., gaseous
> planets, rocky planets, dwarf planets, icy planets, free-floating planets,
> etc., and an individual celestial body may fall into more than one
> category). This approach would address the main practical problem of
> nomenclature without confusing the public about 'planet' itself," said
> Renu Malhotra, a Professor in the
> Department of Planetary Sciences of the University of Arizona.
> Neil deGrasse Tyson, astrophysicist with the American Museum of Natural
> History and panelist for the Great Planet Debate commented, "The word
> 'planet' has surely outlived its usefulness. The time has come for us to
> create a fresh and sensible classification scheme from the ground up -- one
> that applies to all objects of our own solar system, yet is flexible
> enough to embrace newly discovered objects elsewhere in the galaxy. Other
> fields, such as biology, and even subfields of astrophysics that study
> stars and galaxies, have strong needs to classify objects and have solved
> this problem long ago. It's time for the community of planetary scientists
> to do the same. We should not 'agree to disagree, we should 'agree to
> converge'."
> "It was a mistake for the IAU to dictate a definition when there is no
> consensus among planetary scientists. It is also counter-productive to
> focus only on the planets in our solar system, ignoring some 300
> exoplanets," said David Morrison of NASA Ames Research Center. "The IAU
> definition of planet should be withdrawn or ignored."
> "Historically, 'planets' are just objects that orbit the Sun. Even
> asteroids are called 'minor planets' By the IAU. The controversy caused by
> the IAU officially declaring the term to be restricted to eight objects in
> our solar system was unnecessary, but a natural consequence of one group
> of people trying to impose their views on everyone else," said Mark Sykes,
> Director of the Planetary Science Institute, in Tucson,
> Arizona. "Ultimately, over the years, the process of science is not
> guided by imprimatur and ensures that the most generally useful perspective
> will prevail."
> The debate continues.
> ------------------------------------------------------------------------
> The Planetary Science Institute is a private, nonprofit corporation
> founded in 1972 and dedicated to solar system exploration. It is
> headquartered in Tucson, Arizona.
> PSI scientists are involved in numerous NASA and international missions,
> the study of Mars and other planets, the Moon, asteroids, comets,
> interplanetary dust, impact physics, the origin of the solar system,
> extra-solar planet formation, dynamics, the rise of life, and other areas
> of research. They conduct fieldwork in North America, Australia and
> Africa. They also are actively involved in science education and
> public outreach through school programs, children's books, popular science
> books and art.
> The Institute's researchers are based in 15 states, the United Kingdom,
> Russia, Switzerland and Australia.
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Received on Sat 20 Sep 2008 07:22:42 PM PDT

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