Friday, December 30, 2011

Modelling Expansion of the Universe – blog post #48

Teaching The Big Bang Theory to Ontario grade nine science students forces a teacher to embrace their sense of humour. First one must address the prior knowledge the students have which is: The Big Bang Theory is a television show. All good teachers know that they need to meet their students where they are and I had anticipated that my students would be familiar with this tv show so I printed out the lyrics for the theme song before class. The students were happy to sing it; following the bouncing ball on the smart board is always a fun activity!
Eventually we got into the fact that there is actually a theory about how the universe was formed and it is the Big Bang Theory. (It all started with a big bang!) My students were amazed by even this little snippet of information! As I explained the Big Bang Theory to them with the help of numerous visuals and video clips, while constantly referring back to both the lyrics and what they had learned in the chemistry unit, their engagement was obvious by the questions that came pouring out of them. My favourite was: “Why didn’t anyone ever tell me about this before?”
After spending an entire period on the Big Bang Theory I left the class with the thought that the universe is expanding and the promise that tomorrow would be a hands-on activity where we would explore this phenomena. In order to organize a hands-on activity that models how the universe is expanding to students with weak mathematical skills I used my best friend, the internet, to help me come up with a great idea! (This activity is not original to me, it is found on many web pages, I was unable to track down its origin.)
1.      Initiate and Plan = Engage

Together the class used the Smarter Science template to design a testable question. It was: “Can we model how the universe is expanding?”
The variables were:
Independent - Amount of air in the balloon
Dependent - distance between the points
Controlled - shape of balloon and keeping balloon tightly sealed during measuring
In small groups, the students were given a new balloon and a marker. Each group marked six random points onto their balloon. One was labelled home while the other five were labelled A, B, C, D and E in no particular order. 
Using a string to measure the distance between two points

Using a ruler to measure the string

The surface of the balloon represented a 2-dimensional universe. Each point represented a galaxy with home being the Milky Way.
Each individual then made a hypothesis regarding what would happen to the distance from home to each of the other galaxies if the universe expanded. 

2.      Perform and Record = Explore

Recoding the data
They students measured and recorded the distance from home to each of the other five points. This measurement was taken at time one. We used this data sheet. 
An assigned group member then inflated the balloon to about the size of a grapefruit. This represented time two. The distance from home to each of the five points was measured again, while the air in the balloon was sealed inside.
This procedure of blowing more air into the balloon and measuring the distances was repeated six times and the data was collected in an observation table. 

3.      Analyze and Interpret = Explain
The students graphed their data in a simple line graph of time versus Distance from home point. They used a different colour for each line on the graph and a key to define each line.

4.      Communicate = Extend
In their final report the students had three questions to discuss. They were:
1.      How did the distance from the home dot to each of the other galaxies change each time you inflated the balloon?
2.      Did the galaxies near home or those farther away appear to move the greatest distance?
3.      How could you use this model to simulate the Big Crunch, a time when all the galaxies might collapse in on themselves?

This activity was very successful. It helped students who are not destined to be rocket scientists of astronomers understand our concept of an expanding universe. Although they used simple mathematics, measuring and line graphing, it helped them understand why I am always telling them that a lot of what we know about space has been proved mathematically.
I recommend this activity for hands-on learners of all ages!

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