The whole Pluto controversy is very interesting from a nature of science (NOS) point-of-view. The point being that scientists could have all the data ever desired, and still they would come up with different interpretations and conclusions based on their own personal background and experiences. Scientists are not without bias, after all they are only human. A scientist could have his or her entire career invested in a certain line of reasoning and when new information comes along they aren't always able to look at the new evidence with an objective mind. Davis (2000) states that the passion of a scientist in pursuit of an exciting idea places a strain on his objectivity. He may fail to consider alternative hypotheses, he may unconsciously avoid designing experiments that might threaten the favored hypothesis, he may clutch at straws in the face of decisive evidence, or he may even distort the very process of observation.
In my opinion, this is the true nature of science that many inside and outside the area of science don't always understand or want to admit exists. This is why some of the most exciting, and revolutionary discoveries in science have come to people early in their careers or when they are new to a particular field of study. McComas (2004) states that the prior insights that some scientists bring to the process of investigation explain why some individuals make monumental breakthroughs while others do not. It wouldn't surprise me if part of the reason Pluto was named a planet in 1930 was because scientists "wanted" a new planet to be in that particular location of the solar system; therefore, that may have clouded their judgement or ability to look at all the available data, lack of data, and/or quality of evidence.
Sebastien 11 Jul 11:25 PM
Alan is touching a critical point about Pluto's discovery and initial classification as a planet. Indeed when Pluto was discovered, some astronomers were really expecting that a planet would be discovered over there! This has certainly contributed to Pluto being hailed as the 10th planet.
The story is that shortly after Neptune was discovered (1846), initial calculations suggested that its orbit was irregular. Some postulated that a planet the size of Earth was causing a perturbation in Neptune's orbit. At the time, the hypothetical 10th planet was called "Planet X" (from the roman numeral X=10).
This was actually quite controversial. But the very colorful and wealthy amateur astronomer Percival Lowell (better known for his ideas about life on Mars -- the infamous "canals") set out on a personal quest to find that mysterious Planet X, devoting considerable resources to the program.
Lowell died in 1916, but left a large endowment to continue the search for Planet X. Clyde Tombaugh was hired by the "Lowell Observatory" in 1929, and hit pay dirt in 1930. He actually discovered Pluto very close to where some astronomers had predicted that "Planet X" should be found. The rest is history.
As in turns out, there really were no deviations in Neptune's orbit. The supposed "perturbations" were only measurement errors! However, it took decades to finally figure out that there was absolutely no need a "Planet X"...
In any case, Pluto was initially thought to be about as massive as Earth. Only when the satellite Charon was discovered could the mass of Pluto be calculated with some precision, and it was then found that it was much less massive than anyone ever thought. Not even massive enough to have been the hypothetical Planet X.
Talk about shattered expectations!
Cheryl 14 Jul 8:08 PM
Since Pluto is a large member of the Kuiper belt then I do not think that it should be categorized as a planet. Yes, It does have "roundness" therefore exhibiting a balance between the pushing of pressure and the pulling of gravity, but it does not quite fit the entire description of "today's planet". Its roundness does prevent it from being considered a small solar system body, but it still lacks at least one aspect. "A planet must also be the most massive object in its orbital zone". (The Pluto Controversy: What's a Planet, Anyway?- Neil Tyson) Pluto is not alone. It is among many other bodies. This causes Pluto to be categorized with the term dwarf planet. I agree with this decision. I can see how it is quite different than the other planets, even though "traditional planets don't fit into one neat category" either (The Pluto Controversy: What's a Planet, Anyway?). The following description of a dwarf planet sums it up nicely. "A dwarf planet may also orbit in a zone that has many other objects in it. For example, an orbit within the asteroid belt is in a zone with lots of other objects." (Questions and Answers on Planets-http://www.iau.org/public_press/news/release/iau0603/questions_answers/)
Alissa 10 Jul 11:43 AM
This discussion is generating many interesting responses. There is something about Pluto that makes people very passionate- is it tradition, a Disney character named after it, the wonderful name or maybe all of the above! I know that the changing of Pluto's place in the Solar System hierarchy has made many people very upset. It is up to us - who know something about how science works - to explain it to others, either the public or our students. As a part of our science test, students are to be familiar with the nature of science. This whole controversy is a way to show students how science works.
As far as I am concerned, Pluto is neither like a terrestrial or a Jovian planet since it is a very large comet in the Kuiper belt. It is icy, fairly small, and it crosses Neptune's orbit. Its orbit is far more elliptical than the planets. So there is no comparison- it is not a planet at all.
Keith 10 Jul 2:32 PM
Nature of Science
Through my courses in getting my M.Ed. I have learned the value in showing students the nature of science and giving them an idea of how theories and ideas can change over time. Shelley brings up the great point that this is a wonderful topic to explore not only because people have strong feelings about it (I know nearly all of my students from student teaching were very much aware of Pluto's change in classification), but because it demonstrates that science is fluid and up for scrutiny and revision. It is good for students to see examples of people looking back at past ideas, challenging them, and forming new ideas out of that process. I've noticed that many students can't stand being told that science shouldn't be questioned and that it is always right(I know some teachers do this!); they like knowing that part of the nature of science is the questioning, the skepticism, and the revision.
Sebastien 11 Jul 11:47 PM
Science is fluid
Well said. And thanks so much for teaching your students about what science is really about!
I must add that, having evolved in the world of professional scientific research for many years now, I can't understand why scientists are so often depicted as axiomatic and inflexible. It is all the contrary! It is part of our training to constantly challenge old and new ideas, and put them all to the test. I see my fellow astronomers at their happiest when something new and unexpected is revealed. This whole reclassification of Pluto (which by the way had been brewing for over 15 years) has had everyone so excited.
Chery 14 Jul 8:17 PM
I feel the same way. If anyone is flexible, it is a scientist! I think in order to be a scientist, flexibility has to be a given trait. It is ingrained into them. They are constantly looking for new ideas and either building on or changing the old. I can't wait until the new information about Pluto allows astronomers to spark new ideas again. It is so interesting to see how only minute pieces of information can change a large amount of ideas.