Pluto’s Punishment and Two Other Cases of Reclassification in Science: A Golden Teaching

Opportunity

Valerie Bergeron

Delaware Technical & Community College

&

Harry Shipman

University of Delaware

What we will do today

• Describe Pluto’s punishment

• Have you do a version of the Pluto activity

• Briefly evaluate its success

• Is the Pluto situation typical? An example from chemistry

• A second example from astronomy

Pluto’s Punishment

• Status of Pluto has long been debated

• Precipitating event: discovery of big trans-Plutonian objects by Mike Brown of Caltech

• Summer of 2006: IAU strips Pluto of its planetary status, against committee recommendations

Why Pluto? Intense interest

• Summer of 2006 was the first time in 29 years that Time and Newsweek had same science cover story

• Student social website “Facebook” had special interest group on Pluto which attracted 750,000 members in less than one month

Pluto interest, more

• To be “plutoed” was selected as the 2006 word of the year

• In several randomly selected 4th grade classrooms, every student knew about Pluto.

• Future usage of Pluto identifier will determine the fate of the summer 2006 recommendation.

An activity on Pluto

• Yes, we want you to actually do this!

• Form groups of 2-4 and briefly discuss:

Suppose that you are recommending whether and how to include Pluto in your institution’s scale model solar system. What information do you need?

The activity that one of us has done

• Give students a reconstructed conversation between two people who disagreed about Pluto.

• Ask students to decide its fate in their school’s scale model solar system.

• Reflect on what this conversation means.

Did it work? Yes

• Should it be included in the curriculum? 100% of teachers said yes (N=10) in a formal evaluation. Sixty others agree.

• Some comments quite enthusiastic: “Absolutely. Demonstrates [that] scientists need to discuss and agree on definitions.”

Did it work?

• Every group has had a good discussion and come up with varied responses.

• Of the group of 10 who filled out a formal evaluation, 9 understood the main point (2 partially)

Is the Pluto event typical?

• Trigger event: Mike Brown discovering massive trans-Plutonian objects

• Committee discussion

• Usage, not committees, determines what actually happens

The Ever-Changing Periodic Table

A brief look at four components:

• Structure of Table

• Column Numbers

• Number of Elements

• Names of Elements

1976 - TietzFundamentals of Clinical

Chemistry

Honeywell ~ 1988

Comparison Points

Tietz

• Separation in the middle

•Column Numbers - American SystemA for Representative elementsB for Transition elements

•Number of Elements - 105No name for 104Ha (hahnium) for 105

Honeywell

• Column Numbers - 3 sets IUPAC 1 to 18 European (first 8 Roman numeral with A,

second 8 Roman numeral with B) American

• Number of Elements Up to 109 Unq, Unp, Unh, Uns, Uno, Une for last six

elements (unnilquadium, unnilpentium, etc)

McMurry, Castillion & Ballantine - 2007General, Organic & Biological Chem 5th Ed

Bettelheim, Brown, Campbell & Farrell - 2007

Intro. To Gen, Org & Biochemistry 8th Ed

Comparison of 2007 Periodic Tables

McMurry

• Column Numbers IUPAC 1 - 18 American on top of column

• Number of Elements Up to 116 elements (no 113 or 115) No name for 112, 114, 116

Bettelheim

• Separated Hydrogen

• Column Numbers American IUPAC in parentheses on top of column

• Number of Elements Up to 116 No names for 112 to 116

Emsley - 2002Nature’s Building Blocks: An A - Z Guide to

the Elements

Emsley - 2002

• Structure Hydrogen and Helium separated Separated by subshells (s, p, d, f)

• Column Numbers IUPAC and Roman numerals (no letters)

• Number of Elements Up to 120 Names up to 109 110 to 112 and 114 are, Uun, Uuu, Uub, Uuq -

question marks for the rest.

Summary

• Triggering events - discovery of new elements require changes in the periodic table

• After 1976 the structure has been stable (except for Emsley)

• IUPAC numbering is not pedagogically useful• 1997 IUPAC naming decision (to element 109)

has been adopted in textbooks• Newly discovered/synthesized elements require

more than single digit numbers of atoms to be named

White Dwarf Star Spectral Re-Classification (1983)

• Trigger event: formal printing of Ed Sion’s white dwarf catalog

• Prior spectral classification by Greenstein (1960) was not working, with many “classes” becoming empty sets

White dwarf story (2)

• “Committee” discussion at Second Delaware Workshop on White Dwarfs

• People not at workshop were consulted

• Paper published in 1983

• Result? A few additions to the scheme, but general acceptance.

What Does This Mean?

• Process for acceptance of changes in a classification system in these three cases was similar

• Teachers can use examples like these to help students understand that science knowledge is durable yet changeable in their lifetimes

Thank you!

Valerie & Harry

Reference List

Bettelheim, F.A., Brown, W.H., Campbell, M.K, & Farrell, S.O. (2007). Introduction to General, Organic & Biochemistry, 8th ed. Belmont, CA: Thomson Brooks Cole.

Brown, E. (2007). Discovery of Eris, the largest known dwarf planet. Retrieved June 15, 2007 from http://www.gps.caltech.edu/~mbrown/planetlila

Emsley, J. (2002). Nature’s Building Blocks: An A – Z Guide to the Elements. New York: Oxford University Press.

Fraknoi, A., (2006, October 4). Teaching what a planet is: A roundtable on the educational implications of the new definition of a planet. Astronomy Education Review 5(2). Retrieved April 14, 2007 from http://aer.noao.edu

McMurry, J., Castellion, M. E., & Ballantine, D. S. (2007). General, Organic, & Biological Chemistry, 5th ed. Upper Saddle River, NJ: Pearson Prentice Hall.

Tietz, N. W. (Ed.). (1976). Fundamentals of Clinical Chemistry. Philadelphia: Saunders.