Thursday, October 27, 2011

Cups and Strings - follow up

(This is part 2 - Read about Part 1 here)
This activity went great today.We used cups instead of cans - worked perfectly. They worked in group of four. Each group got string, two cups, scissors and a copy of the Morse code chart. They were asked to first send voice messages, then use Morse code to send a message. Each group reflected on how they agreed to communicate dots and dashes and how they knoew the message arrived correctly. They were then asked if they had to use this method to transmit a messgage back to town (we're in the sticks) what would they do?

This may seem like a simple and silly activity, but it really ties into seeral things we will be covering the next few weeks. First, all data is sent over the Internet using some form of encoding. For this to work you have to agree ahead of time on a set of protocols. Their communication with the cups required a dedicated line, the string. One of the major developments that led to the Internet was Leonard Kleinrock's ideas about dividing messages into smaller packets which moved us past the need for dedicated lines. In networking and other areas there are things we can do numerically to check if a message arrives correctly. The list goes on.

A fun side effect was they had to deal with interference on their lines. As other students moved theough the halls we had various "interruptions in service". One involved a kid licking the string, no idea why.

While I hope the Internet is safe from licking, it is certainly at risk of natural and man-made interrruptions.

I had several students stop and ask what we were doing, and it was a hoot to hear my kids explain how awesome computer science is. They were the perfect ambasadors. In a moment so perfect I couldn't have scripted it if I tried one of my students explaind to his friend we ran into that "everyone should know this stuff, it's important".

The groups really experimented with this. One group created a three-way syste. Interesting fact, the cups have to be nearly equidistant for a message to transmit to all three cups. My favorite was the group that used Pythagorean theorem to find the length of their string.

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