Deep time - what is your metaphor?
Skills and concepts that students must have mastered
understanding the age of the earth
How the activity is situated in the course
Content/concepts goals for this activity
I would like students to be able to work fluidly with numbers, words, and images.
I want students to think about and appreciate scaling relationships.
Higher order thinking skills goals for this activity
I want students to be able to deconstruct a metaphor (a simple, memorable thumbnail sketch), analyze it, and create their own.
Other skills goals for this activity
I want students to think about how scientific concepts are communicated to non-experts, and to appreciate the import of doing this as accurately as possible.
Description of the activity/assignment
I would like for you to evaluate these two metaphors for accuracy. How close were Twain and McPhee to appropriately contexualizing human existence in geological time? Use the pdf's of Twain's and McPhee's prose and what you know from class lectures to accomplish the following goals.
(1) Evaluate whether McPhee's and Twain's metaphors are appropriately scaled – i.e., do their metaphors correctly depict the age of the earth relative to human history? How about if we incorporate the fossil record of humans?
(2) Create your own appropriately scaled metaphor. Add in at least three other "signposts", either biological or geological, into your metaphor and explain why you chose them.
Determining whether students have met the goals
Teaching materials and tips
- Activity Description/Assignment:
- Instructors Notes:
Age of Earth — 4,500,000,000 yrs
Recorded human history — 10,000 yrs
Human share of earth history — 1:450,000
Height of the Eiffel Tower — 324 m
Thickness of skin of paint — 1 mm
skin of paint's share of eiffel tower — 324,000
Average human arm span — 150 cm
nail removed by nail file — 0.10 mm
nail file's share of human arm span — 1:15,000
**Students will come up with a variety of values for the length of human recorded history, thickness of a skin of paint, and how much nail is removed by a file. This can be instructive; you can can talk about variability and error.
- Solution Set:
Twain was closer than McPhee, but depending on how student's estimate the various measures they could be closer or farther from the correct answer. The most important ratio to get correct is the human share of Earth history.