Task: Find the Circumference of Earth Using Astronomy.
Your goal is to determine the circumference of Earth. You should use Starry Night to calculate a
value (including errors) and then ﬁnd the actual value in your textbook or online. Discuss your
analysis, procedure, all thoughts and ideas in your lab book. Finally you will need to “teach” the
rest of the class about this experiment.
Feel free to ask for help from your teachers.
These questions are meant to oﬀer some hints:
Before you begin, think about what circumference means, what does this say about Earth (what
shape is Earth?)? What is one way that we can tell that we are on a curved surface. Think back
tho earlier labs, how does our view of stars change with our location of Earth? Use Starry Night
to help remember and reinforce those concepts.
Now using this knowledge, think about how the view of one star can change between diﬀerent
locations on Earth. Can you think of a useful relation that would determine our latitude on Earth?
What exactly does the latitude tell you about the size or shape of Earth?
You will need to know the exact distance between two locations on Earth. Given this last hint,
how could you ﬁnd the circumference of Earth?
Teaching the rest of the class:
Here’s your opportunity to terrorize the other students. As the teachers you can ask your students
questions which will lead them to ﬁguring out the method you used and why that method was
eﬀective. You should try to make sure that all the essential concepts are well-understood by all
your students. This may mean that you can have them role-play, use props, use activities, or any
other tool for illustrating and instructing your students. If you are unsure of the main concepts
you may ask your teachers. Your lesson should take about 15-20 minutes.
Main concept– The orbit of Venus is within the orbit of Earth.
Ways to teach– ask students “What are some observations that might show whether a planet is
outside Earth’s orbit or inside?”, “Suppose you notice that the planet is always rising or setting
within 3 hours of sunrise or sunset. What does this imply?”, “How long should one observe the
planet to be completely sure of its orbit?”.
Some other ideas– you could have 3 students act out the scenario until the whole class is convinced
that an interior planet stays close to the Sun (seen only within hours of daylight) while the outer
planets may be seen at any time.