Once students are in the classroom I show them this video segment of an episode in the "Big Bang Theory" where Sheldon swears he can tell that the cricket chirpping is the Snowy tree cricket.
The temperature-Cricket chirp relation has often been used to demonstrate a linear function. In this lesson, students will graph this linear relation themselves using Dolbear's Law formula and then listen to real crickets chirp to determine temperature using their own graphs.
First a little history:
Before Dolbears publication in 1897 relating temperature to Cricket chirps, others had observed and written about this relation but were not recognized. Despite what Sheldon says in the video, Dolbear really did not specify if the cricket he referred to was the Snowy tree cricket, although it was assumed. It was later found that the temperature-chirp correlation also applies to the more common field cricket used in this lesson, but not as exact because their chirpping rate may decrease with age. Still, the margin of error is at most 3 degrees which is pretty good.
After the clip and a brief discussion of the history of cricket chirp research, I tell my students that we will be graphing the relation between the field cricket chirps and celsius temperature. Then, we will work with the Celcius-Fahrenheit temperature conversion equation.
After the clip and brief discussion on the fact that counting cricket chirps can help tell temperature, I hand out Cricket chirps and Temperature in Cº.docx worksheet and ask that they they pair up and together plot the relationship between Celsius temperature and number of chirps per minute. I ask the class to make the y-scale tick marks at 2 degree intervals, rather than 5 or 10. (My students are generally more used to fahrenheit temperatures and are tempted to scale up to 100.)
After completing the table of values and graphing the linear relation, I ask that my students to answer the questions on page 2 of the handout. With respect to the x axis, I leave it up to them, but as I walk around I try to make sure that their scale reaches 120 chirps on their papers because this will make it easier for them to answer closure questions. Most students will go up the x axis by intervals of 10, which is ideal here. When students reach part II of the handout they will be forced to stop and wait for the next section. I ask students who finish early to look up information on field crickets in the carribean if they have internet access. They will be listening to one soon.
Part II of the Cricket chirps and Temperature in Cº.docx handout is the closure of this lesson. Students are asked to listen to actual field crickets recorded (by me) on 4 different days. Each recording lasts exactly one minute. Students are to count the chirps in that minute, then use their graph to estimate what the temperature was at the time. Students may want to use the equation which I motivate as well. This way they can compare their line graph to the actual equation function.
Cricket Chirp Videos
Chirp Day 1 (114 chirps in one min)
Chirp Day 2 (119 chirps/min)
Chirp Day 3 (114 chirps/min)
Chirp Day 4 (56 chirps/min)
I show the students the actual temperature once they have finished.
Teacher's Note: The last chirp recording was done very early. All the recordings were done in October when the difference in temperature from mid-day to night can be up to 12 Celsius degrees. The largest temperature difference here was 7 degrees.
The last question on the handout is to convert these celsius values to Farenheit, knowing that students may be more familiar with the Farenheit values.
I like to get student opinion at the end on what they think of all this. Some students are quite fascinated with it, others are skeptical. It's always nice to hear views from both sides. I may have this discussion orally, or I may ask students to write a thought in the back of their handout. I collect the handouts at the end to take home and review their work and if applicable, read their thoughts.