Tuesday, February 26, 2008

Should One Use a ‘Backward’ Approach to Teaching the Nature of Science?

Random thoughts on teaching the nature of science.

It is generally accepted that successful science education results in learners developing a meaningful understanding of the nature of science. In fact, the various guidelines for what should be taught in introductory science courses throughout the educational levels uniformly state that students should develop an understanding of the nature of science (viz., AAS, AAAS, NSES, SCST). According to these documents and position statements, students who understand science know that scientific knowledge is based upon evidence generated through experimentation and evidence, that science is a process that uses models to make predictions about natural phenomena, and that scientific theories are tentative subject to additional evidence, often resulting from advances in technology. In the same sense, these authors suggest that one might further expect students to understand that science is fundamentally a human endeavor and is enhanced, as well as constrained, by societal values and technology.

If one agrees that enhancing students’ understandings of the nature of science is an important goal of science education, the next thing one wonders is how best to teach students these ideas. Along a continuum of ideas, one perspective might be that simply by students being exposed to and memorizing the methods and results of astronomical inquiry over the duration of a course, that students should intuitively develop an accurate sense of the nature of science. However, a robust research agenda by Norm Lederman and his colleagues (viz., Lederman, 1999 and references therein) argues that students do not develop deep understandings about the nature of science unless the underlying ideas are taught explicitly. Indeed, a cursory survey of the introductory chapters of typical astronomy textbooks suggests that students should learn about the components of scientific inquiry nearly independent of the context of astronomy. Many textbooks bold-face such key terms as hypothesis, theory, law, and experiment/observation are included as definitions in end-of-book glossary entries—BUT, these same texts rarely use such words ever again in the textbook after the introductory chapters.

A long-standing strategy for teaching students about the nature of science, and the process of scientific inquiry has been to assign students the task of completing a “science fair” project. In its most abstract form, students are commonly asked to first create a hypothesis, conduct background library research, design an experiment with controlled variables, manipulated variables, and responding variables, summary their results in a table or graph, and create a conclusion about the veracity of their proposed hypothesis. (In the absence of systematically gathered data, I submit to you that these components are those commonly found on the judges’ scoring forms for many secondary-level science fair competitions.) In support of students conducting science fair projects, numerous web sites and books have been written that go through these steps in sequence, starting with generating a question and writing it in the form of a testable hypothesis, and ending with a conclusion that uses data to support or reject the hypothesis.

Upon reflection, one wonders if a ‘backwards’ approach, based on the pedagogical notions of faded scaffolding proposed by Marx and his colleagues (Krajcik et. al., 1998) might be more effective at helping students develop a deeper understanding of the nature of science consistent with the aforementioned science education reform documents. In other words, instead of describing first the character of an if-then-because hypothesis followed by explaining the process of fair-testing by collecting data through appropriate experimental design, then ending with how to write a formal conclusion statement, what would happen if the instructional sequence was to provide students with scenarios starting with an entire inquiry sequence, then piece by piece, start replacing ideas from end-to-beginning? Perhaps a simplistic, yet illustrative, example might serve to clarify this notion.

Question Res. Procedure Data Collection Conclusion
1 Given Teacher Given Teacher Given Given
2 Given Teacher Given Teacher Given Created
3 Given Teacher Given Created by Student Created
4 Given Student Created Created by Student Created
5 Created Student Created Created by Student Created


STEP ONE: Students are shown a desktop planetarium program projection of the Sun’s daily motion through the sky at the equinox and asked to record the exact azimuth at which the Sun rises on the equinox in order to systematically collect data and use observational evidence to answer the question, “Does the Sun rise directly in the East on the first day of spring?” Note, the question, the research design/procedure, the data, and even the answer is provided to the students.

STEP TWO: Students are shown a desktop planetarium program projection of the Sun’s daily motion through the sky at the equinox and asked to record the exact azimuth at which the Sun sets on the equinox in order to systematically collect data and use observational evidence to answer the question, “In what direction does the Sun set on the first day of spring?” Note, the question, the research design/procedure, and the data is provided to the students, but NOT the answer.

STEP THREE: Students are shown a desktop planetarium program projection of the Sun’s daily motion through the sky at the equinox and asked to record the exact times, azimuth, and altitude of the Sun at rising, transit, and setting on the equinox in order to systematically collect data and use observational evidence to answer the question, “What is the altitude of the noontime Sun on the first day of spring?” Note, the question and the research procedure are provided to the students, but NOT the data collection nor the answer.

STEP FOUR: Students are shown a desktop planetarium program projection of the Sun’s daily motion through the sky and asked to create a list of observations they would need to make and record (an experimental procedure) in order to collect data to answer the question, “how does the Sun move through the sky on the first day of winter?” Note, the question is the only thing given by the teacher, whereas the data collection procedure and the answer must be generated by students.

STEP FIVE: Students are given access to a desktop planetarium program projection of the Sun’s daily motion through the sky asked to create a list of questions they could answer by planning a set of observations they would need to make (experimental procedure) in order to answer their question. Note that it is unlikely that students would pick questions far afield from the domain for which they have had four previous experiences – in this sense, although this meets the spirit of “open inquiry,” the activity falls within the overall conceptual domain of motions of the heavens. For certain, one might wonder if this approach requires significantly more time to instruct students than it would if one had given students a series of steps to follow or even simply demonstrated these ideas to students. I submit it takes considerably more time to teach in this manner; however, the goal here is to facilitate students to learn about the nature of scientific inquiry simultaneously, and perhaps superlative to developing students’ understandings about the motion of the Sun.

It seems to me that students do need help with understanding each of the components of scientific inquiry, as an important and simultaneous part of learning how to conduct scientific inquiry where: (i) students are engaged in questions; (ii) students are designing plans to pursue data; and (iii) students are generating conclusions based on evidence they have collected. Therefore, I propose that a series of exercises might help students to understand the nuances of each component in the following ways.

(A) students are generating to conclusions based on evidence

In each case, are the conclusions sufficiently justified by the evidence presented?

1. Polaris, the North Star, never rises and sets because observations reveal that it is visible in the same location any clear night of the year and any time of the night.

2. Solar eclipses are caused by our Moon blocking our view of the Sun based on the evidence that this only occurs during new moon phases when the moon’s path is close to the ecliptic.

3. Jupiter must be physically larger than Saturn because Jupiter takes up more of the field-of-view in the telescope eyepiece than Saturn does.

4. Pluto is not a planet because it has no life nor any liquid water on its surface.

(B) students are designing plans to pursue data

In each case, will the research design created answer the question posed?

1. To determine when the Sun will set on June 1, we will record the setting times on March 1, April 1, and May 1 and extrapolate.

2. To determine how long it takes the Jupiter to rotate on its axis, we will record the apparent longitudinal position of the great red spot every hour throughout the night.

3. To determine the azimuth (direction) the Sun sets, we will observe its highest altitude every day.

4. To determine the temperature of the Sun, we will measure the temperature of a glass of water achieves after being illuminated by the Sun all day.

(C) students are engaged in questions

In each case, determine if the question is scientific?

1. What time will the Sun set on my birthday?

2. How much larger does the Sun appear to be in the sky than the Moon?

3. Pluto is a planet?

4. Did God make the Sun spin?

In science education circles, people often speak of a continuum of student experiences ranging from step-by-step cookbook laboratory verification exercises, guided-inquiry experiences, to open-inquiry experiences. For the purposes of this discussion, I am defining open scientific inquiry as the process by which students are (i) engaged in questions; (ii) designing strategies to pursuing data; and (iii) generating and defending conclusions based on evidence they have collected. There seems to be considerable reluctance for teachers to “turn students loose” to pursue whatever they please in open-inquiry learning experiences. However, when using a backwards, faded scaffolding approach as outlined here, student inquiry is specifically, yet quietly, channeled into conceptual domains consistent with a teachers’ curriculum and instructional goals. Most importantly, the focus here is on scientific inquiry, rather than on memorizing the facts and figures of science. As such, it just might be that science becomes more attractive to individuals who often have the perception that science is boring rather than a creative endeavor worth pursing with intellectual energy.


American Astronomical Society Position Statement on Introductory Astronomy Courses as reported in Partridge, B. & Greenstein, G. (2003). Goals for "Astro 101": A report on workshops for department leaders, Astronomy Education Review, 2(2).

American Association for the Advancement of Science. (1993). Benchmarks for Science Literacy. New York: NY: Oxford University Press, Inc.

Krajcik, J., Blumenfeld, P. C., Marx, R. W., Bass, K. M., Fredricks, J., & Soloway, E. (1998). Inquiry in project-based science classrooms: initial attempts by middle school students. Journal of the Learning Sciences, 7(3-4), 313-350.

Lederman, N. G. (1999). Teachers’ understanding of the nature of science and classroom practice: Factors that facilitate or impede the relationship. Journal of Research in Science Teaching, 36(8), 916-929.

National Research Council. (1996). National Science Education Standards. Washington, DC: National Academy Press.

Society of College Science Teachers Position Statement on Introductory Science Courses retrieved from www.nsta.org


Many of these ideas are the direct result of extended conversations with Stephanie Slater, University of Wyoming CAPER Team.


Tim Slater, University of Arizona & University of Wyoming

Cognition in Astronomy, Physics, and Earth sciences Research (CAPER) Team

Email: timslaterwyo@gmail.com

Wednesday, February 13, 2008

Students' viewpoints on what ET might be like?

The Teaching Astronomy Blog welcomes a guest contributer: Tim Slater!

Off hand essay on engaging students to think about finding life beyond Earth...

Often when giving public talks on astrobiology and searching for extraterrestrial life, an oft posed end of lecture question is, “why are we looking for bacteria instead of for living things?” Now, I know this is a common question, so I try to make a big deal out of bacteria being alive – being organisms that take and recycle energy from their environment, alter their environment by their being there, and reproducing. I also talk about how surprising it is that bacteria can thrive in more exotic environments than humans can (aside from the jokes that thermo-philic people live just fine in both extremes of the heat of Tucson, AZ and the cold of Laramie, WY). Yet, people often ask. Perhaps it is because they’d rather NASA wasn’t spending their tax dollars on looking for “lesser” forms of life or perhaps they don’t really believe bacteria are alive – either way, it is a definite sticking point.

In pondering how to get around this while giving classroom lectures in Hilo last week, it occurred to me to try something new. I asked seventh grade students at the beginning of my classroom visit to “imagine they were an astronaut being sent to a newly discovered planet where life existed – and to creatively draw what creatures they might find there and to provide three important facts about these new life forms.” You might imagine what students drew—nearly 100% drew anthropomorphic things with arms, mouths, eyes, and legs.

So, even before I began my “lecture,” I polled students to raise their hands and how many drew something with eyes? Then I said, could several people give me examples of living things on Earth which have eyes—which many could do. Then I said, ok, could you give me some examples of living things on Earth which do NOT have eyes. It took students a few moments, but eventually, they listed trees and worms (and of course bats and sharks were mentioned too as having lousy eyesight – glad they didn’t point to my thick glasses!). I said to them, “hum, curious, I wonder if there are more living things on Earth with eyes or withOUT eyes?,” and left the question unanswered.

Then, I went through the list – examples of things on Earth with mouths, then without mouths, and then do you think there are more living things with mouths or without mouths on Earth? Followed by the same dialogue about arms and legs.

At this point, it seemed to me that many students were on the verge of considering that maybe most things on Earth don’t look like people with eyes, mouths, arms, and legs – but to be sure, I went in for the kill. I said, “well, let’s change the challenge for a moment to say, ‘imagine you are an alien from another planet sent to land on Earth and look for life…if you just landed at some random spot on Earth, would you land in the water or on land? Hum, well if you landed at some random spot on Earth, how likely do you think you could look around and see a person?” Well, to my great surprise, this didn’t seem to seal the deal as well as I thought.

So, in desperation, I grabbed an inflatable beach-ball globe of the Earth, I and started randomly tossing it to students. I said, “imagine you landed where your right thumb is, would you likely look at the window of your space craft and see a person?” And, I kept a tally on the white board of person or no person, while the students tossed the ball around to other students and yelled out the answer. Well, you know where this is going, after 15 or so tosses, when the throwing got extreme, it was clear that most of the time, a randomly landing thumb (alien space craft) didn’t hit land, let alone a population center. Now, this was the culminating piece of evidence for majority of the students – aliens might not even know there were living things with eye, mouths, arms, and legs if they visited Earth unless they were lucky. And, this, of course, supports the notion that when we go to other planets, we need to be open minded about what life there might look like and it probably doesn’t look much like us.

I hope that my luck with this continues, and that if you try this with your students, it works well too!

Clear Skies, Tim

Tim Slater, CAPER Team
University of Arizona and heading to the University of Wyoming
Check out the silly press release: http://www.uwyo.edu/news/showrelease.asp?id=20440
And write me timslaterwyo@gmail.com