The Solar System Around Us: Planet Learning for Third Grade

For students to understand the third grade planet lesson plans on criteria, they must first understand how the term "observation" has changed throughout the years. While students may know what observation is, do they know about how the progress of tools can change how things are observed? Use the lesson plan below to demonstrate this fact.

Explain to students that the rules of science are ever changing based on the knowledge that science acquires. Knowledge in science is acquired through use of the scientific method and largely through observation. Observations are only as accurate as the tools used to observe with. For this lesson you will need some play dough and a cloth measuring tape.

Give students each a bit of play dough. Ask students to shape the play dough into a spherical shape. Ask students if their shapes are round. Next, define a sphere to students so that they understand that a true sphere should measure the same at any given diameter. Now, measure the students spheres. Discuss how the spheres do not measure exactly the same at any given diameter. Does this change the fact that the students call them a sphere or a ball? Of course not. The object itself did not change, just the rules of defining it. Ask students if they would have known that the balls were not true spheres if they had not been measured. Now discuss the advances in the tools of science such as the development of the Hubble Telescope.

Ask students to tell you the name of the planets. Ask students if they are aware that there were once 9 planets? Introduce them to Pluto and offer them the following information that defines the criteria a planet must meet before being called a "planet".

A planet must have enough of its own gravity to make it into a round (somewhat spherical) shape as it orbits the Sun and clears the debris from its path.

Discuss Pluto with your students. Did Pluto do something to change its status as a planet? Not at all. The fact is that enough developments were made in the tools of science to see that there were other objects with larger characteristics than Pluto's, yet they were not yet defined as planets. These objects were called Dwarf Planets instead. They are not large enough to clear the debris from their orbit. Would Pluto's have changed in status without the advances in telescopes that enabled scientists to see other objects of similar shape and size?

Discuss some of the following questions with your students.

• If there is life on an object in space, does that make it a planet? Why or why not?
• Is the Earth perfectly spherical? (No, actually it isn't.)
• Have your parents ever changed a rule in the house based on new information?
• If an object is not round, can it be a planet?