The Astronomical Unit
Greg Ragland
2/17/98
Description of Lesson
The focus of this lesson is to teach students how far each of the planets in our solar system are
away from the sun compared to the earth. This is a lesson in which the students have the
opportunity to show how far the other planets are away from the sun in relevance to the earth's
distance using a measurement small enough that they can show at school.
Grade Level:
This lesson has been structured to teach a fifth grade class. The Alabama Course of Study
suggests that students will "explain the variety of components of the solar system."
Background Information:
The earth is approximately 93,000,000 miles away from the sun. The earth's distance from the
sun equals one astronomical unit. Therefore, one astronomical unit is equal to approximately
93,000,000 miles. The planets in our solar system's distances from the sun can be compared to
the earth's by using astronomical units.
Mercury is approximately one third of the distance from the sun than the earth, so it is one third
of an astronomical from the sun. Venus is three fourths of an astronomical unit from the sun.
Mars is one and one half astronomical units from the sun and Jupiter is five and one fourth.
Saturn is nine and one half times of the distance of the earth from the sun and Uranus is
approximately nineteen. Neptune is thirty astronomical units and Pluto is thirty-nine and one
half units away.
Everything in our solar system is very far away. Planets are not the only thing that can be
measured by using astronomical units. Stars and other galaxies may also be measured by using
astronomical units.
Concepts:
Recognize and describe what an astronomical unit is. Realize how far the earth is from the sun
and be able to compare the other planet's distances using astronomical units. By using a unit of
measure to represent an astronomical unit, the students should be able to show on paper or
outside how far each planet is away from the sun. By using a yard (36 inches) for our unit of
measure that represents one astronomical unit, the students will be able to see the planets on the
football field and get an idea of their distances from the sun in relevance of the earth's distance.
After using one yard, they can get a better idea by using two or three yards. When using three
yards, the students will be able to see what our solar system would be like if it were the size of a
football field.
Materials:
Procedures:
1. Explain to students what an astronomical unit is and how it works. Explain to them that each
planet is a certain distance from the sun and can be compared to the earth's distance using
astronomical units. (This can be done the day before you do this activity outside so that
you may have more time for the activity.)
2. Assign students to nine different groups, each group representing a different planet. You
should also assign one student to be the sun.
3. Give each group one yardstick and the proper sign for their group. Each group should decide
who is going to hold the sign, who is going to measure, and who is going to help count
when measuring.
4. Take students to a large outside area. (A football field is a great place for this activity because
it gives you plenty of room to do this.)
5. Instruct the student who is the sun to find somewhere to stand. Stress to that student that it is
very important for them to stay where they are in order for every group to get an accurate
measurement.
6. Tell the students that the unit of measure they will be using to represent one astronomical unit
will be one yard.
7. Instruct the students to begin measuring in yards form the sun until they reach the distance
that their planet will be in astronomical units. Distance that they should be: Mercury=1/3
yard (12 inches), Venus= 3/4 yard (27 inches), Earth=1 yard, Mars=1 ½ yards, Jupiter=5
1/4 yards, Saturn=9 ½ yards, Uranus=19 yards, Neptune=30 yards, and Pluto=39 ½ yards.
8. Tell students this is what our solar system would look like if it were the size of the area that
we are standing in. If earth were one yard from the sun, this is how far each of the other
planets would be.
9. Repeat steps seven and eight using two and three yards for your astronomical unit so they can
get a better understanding of how far each of the planets are away from the sun. Let the
students change planets and roles so that they each can have the opportunity to do
something different.
Gather students in a colloquium and have them explain to you what they have just done. Ask
questions about how far each of the planets are away from the earth and let the students tell you
what an astronomical unit is and how it works. You may also use miles for your astronomical
unit and relate it to cities around you. For example: If you were at Auburn University and you
were the sun and one mile equaled one astronomical unit, how far away would Pluto be? It
would be in Columbus, Georgia. Jupiter would be somewhere in Opelika and Mars would be
about a mile and a half away. You can use any cities or places to represent how far away the
planets would be. You can also use more than one mile for your astronomical unit so the
students can get an even better understanding of how big our solar system is.
Assessment:
Students can come up with their own unit of measure to represent an astronomical unit. Allow
the students to do this and tell them it should be something small enough they can put on poster
board or butcher paper. Have the students brings in 40 of the objects they chose for their unit of
measure and glue it in a straight line on the poster board or butcher paper. After they have done
this, they can label where each of their planets would be on their poster they have made. You
can assess the students by observing them while they are working on their projects by taking
notes of who is having problems and who is not. You can also assess them by grading their
actual projects and checking to see if they have the proper measurements and alignment.
Useful Internet Sources:
Lesson Plans/Science/Astronomy (5-6)
This lesson identifies the unit used to measure distances in space. It provides information about
how big our solar system really is.
Science Process Skills:
Questioning, data collecting, making models, inferring, cooperative learning, measuring, relating,
and role playing.
Critique of Lesson:
I feel that my lesson went really well. The students seemed to get an understanding of
what an astronomical unit is. They seemed to really enjoy the activity. I am really glad that we
reviewed everything the day before they went outside. This seemed to give them a much better
understanding of the astronomical unit and how it works. I feel that if we would have started on
astronomical units when we went outside, they would have been really confused and not had a
clear understanding of what we were doing. We would have probably ran out of time and not
completed what we were doing.
I am really proud of my students. They did a wonderful job of measuring and most of
their measurements were very close. All of them were within two or three yards of the spot that
they were supposed to be in. By the time we finished the activity, most of the students had
already memorized the chart of how many astronomical units each planet was away from the sun
and new their correct measurements..
When we doubled and tripled our astronomical units, using two and three yards instead of
one yard, the students were really able to see how much further Pluto and the other planets were
away from the sun compared to the earth. We also used the miles and talked about how far the
planets would be and they were really amazed by that.
For their assessment, the students made their charts using different objects for their unit of
measure. Some used bubble gum, cereal, buttons, pogs, toothpicks, coins, and there were many
other ideas. Some of their measurements were a little off, but they seemed to have the basic
understanding of what an astronomical unit was.
The student's behavior was excellent during this activity. They were not only learning, but they
were also having a lot of fun. The idea of being outside really made the lesson a lot more
interesting for them. Luckily, we had beautiful weather during the lesson. They were very
interested and stayed on task.
One thing that I liked that happened during the lesson took place after we had used two yards for
our astronomical unit. We were talking about how you could use three yards and I mentioned
that their may not be enough room. I knew that their would be enough, but I wanted to see how
the students would react. One students said that they believed that there was enough space. I
asked if they would like to try and all of the students wanted to. This showed me that they were
interested in the lesson and they were thinking throughout the lesson. It also showed me that
they understood what we were doing and what we would have to do if we did triple our unit of
measure.
Overall, I think that the lesson was a success. As I mentioned earlier, the students seemed to be learning throughout the lesson and were interested the whole time. I also taught this lesson to my second science class and they seemed to even get a better understanding.