# Learning to Think about Gravity II: Aristotle to Einstein

## Summary

We will discuss the basics of Aristotelian, Newtonian, and Einsteinian theories of Gravity and the implications of each theory. We will also review the basics of General Relativity and then consider how each of the three scientists interpret free fall and orbital motion. We will compare and contract the essence of each theory by forming a classification rubric. We will employ "distributed cognition groups," discuss some parallels in the interpretations between Aristotle and Einstein, and consider how Newton's theory is different from the other two. Students will learn how scientific theories are constructed, how they are validated, and how they are overthrown by theories that do a better job explaining nature.

Leading questions to be addressed: (1) What is gravity - is it a force? What is circular motion - is it "free motion?" (2) What are students' pre-instructional conceptions about gravity? (3) What concepts about gravity do Aristotle and Einstein share - how is Newton different? (4) Why don't we teach Einstein's notion of gravity in the classroom - knowing that Newton's theory has been superseded?

## Learning Goals

- Students will learn basics of Newton's Theory of Gravity and of General Relativity.
- Students will compare and contrast Newton's theory to Einstein's theory.
- They will make the transition from Aristotelian to Newtonian to Einsteinian thinking.
- Students will learn to respect their own theories as well as those of others. They will learn that science is not absolute and that Aristotle's concept of gravity was believed by humanity for 2000 years. And although Einstein's theory does a better job fitting the data, we still teach Newton's theory 100 years after Einstein invented GTR.

## Context for Use

This activity is particularly useful to teach how theories are constructed and how scientific methodology can lead to a deeper understanding of the world around us. It can be used as an introductory class on the nature of science, but it can be adopted to other settings.

This exercise works very well with a class size of roughly ten students, but has also been successful if applied to larger classes of 50 students.

The activity is an interactive lecture that includes Socratic dialogue, in class demos, and thought experiments.

This activity is desiged to follow Learning to Think about Gravity: Newtons's Theory activity which covers more details about Newton's theories, but it is also possible to do the abbreviated version of this module (slides 12 to 21).

## Description and Teaching Materials

The historical-constructivist method of teaching will be employed.

Student's ideas will be elicited.

Followed by an interactive lecture with two thoughts (described below) and several discussions.

The final activity consists of looking back at the original pre-instructional ideas and "correcting" them.

Optional: A discussion on the Misconceptions of students can be included. A list of these misconceptions about gravity (PowerPoint 3.2MB Jul23 07) is attached.

Experiment 1:

Cannon Ball Experiment

Experiment 2:

Equivalence Principle

## Teaching Notes and Tips

Do not tell the students the answers.

Elicit students' pre-instructional ideas and do not judge them.

Students have many misconceptions about motion and this has been research extensively in the science education literature. Research of Newton's Universal Law of Gravity has been reviewed by Kavanagh & Sneider (2007) and the reader is referred to that article about students misconceptions and about methods of teaching Newtonian gravity.

Encourage and lead discussions where students discuss their ideas among themselves. Have them argue out the validity of various arguments.

Use the power point presentation as a guidance to conduct class. Only present the right answers after students have reached the same conclusions themselves.

Don't skip final discussion that puts the exercise into perspective.

## Assessment

At the moment assessment hinges on leading and interpreting the discussion.

## References and Resources

Learning about Gravity I. Free Fall: A Guide for Teachers and Curriculum Developers

Learning about Gravity II. Trajectories and Orbits: A Guide for Teachers and Curriculum Developers