Overview

In this lesson we work in groups using classroom supplies and everyday objects to develop our own systems for encoding and sending simple binary messages, messages that only have two possible values. We will think about what can be usefully conveyed in such a simple message and build a "device" to communicate the message over some physical distance. Then we are asked to consider how to use your binary messaging devices to send a more complex message - a message with more than two possibilities, say four, or eight, or even thousands of different messages. We will collaborate in an iterative design process in the "maker ethos" of rapidly building and improving their "device" for sending messages.

Vocabulary

Goals

Students will be able to:

Purpose

One of the least understood things about the internet is how it works as a physical system. Bits of information physically travel from one place to another. On the "real" internet bits are transmitted using a variety of different mediums, and most of the time a single bit physically travels over a variety of systems to get where it’s going. Students should see the issues in the physical transmission of bits as a separate problem from interpreting and encoding the messages sent on top of those systems.

While building and modifying their "binary message devices" students should recognize that it's easier to invent a system of communication that uses combinations of binary signals with a simple device, rather than making a new, or increasingly complex device for each new problem. This lays the foundations for:

Resources

Getting Started

Computer science is commonly thought to be the study of computers themselves - the physical machines we have on our desks and carry around in our pockets. Another way that computer scientists think about would be to say that computer science is the study of information and information processes. Today we're going to think about what "information" and "information processes" means. What is it that you think you might be studying?

What is your personal definition of "information?" Take a minute to write it down.

Pro Tip

Remarks

Activity

Today we're going to work more with binary questions and messages. First you and your partner need to come up with a binary question.

Prompt

Imagine that you and your friend have not been able to communicate for the entire summer, and you have a chance to ask her one binary question that she will answer. What binary question do you want to ask?

Pro Tip

Now that you’ve come up with a binary question, let's talk about how you need to answer it. Answering a binary question is easy when we speak to each other, but it becomes more difficult when we are separated. Today we will focus on how a binary message can be sent over a distance. You will build the device that sends them.

Introduction

You are going to build a device out of classroom supplies to send information to a classmate on the other side of the room. There are some basic rules and constraints:

Challenge 1: Send a Binary Message

For the first challenge you will have 5 minutes to construct a device out these supplies to send a simple binary message - one of the two possible answers to your binary question - to your partner on the other side of the room.

You should try to make it fail-proof. Consider obstacles that might be thrown in your way. Would your device still work if:

Quick Share / Demonstration

Pro Tip

Content Corner

Example Solution

Binary Question: "Do we have a quiz or test today?"

Challenge 2: Four possible messages

Not all questions have only two possible answers. Your new challenge is to invent a way to use your device to send an answer to a question that has 4 possible answers! Think about these things:

Quick Share / Demonstration / Discussion

Activity Goal

The purpose of the whole activity is to build toward an understanding that, from an engineering perspective, the simplest way to physically send an infinite number of messages over some distance is to make a binary message device, and to send unique sequences of binary states. This is how the internet at physical level actually works. After each little challenge the purpose of the demonstration and questions is to:

There are 3 basic ways that we will focus on to make a device send 4 different messages:

  1. Modify the device so it can assume 4 different states.
  2. Similarly, we might just use the device differently in such a way that it can do 4 different things with it.
  3. Use the same representations of states A and B from your original device and come up with 4 unique sequences, for example A-A, A-B, B-A, B-B

Most of us will likely do the first two options - modify the device or use 4 different ways - but some might do the 3rd option at this point. Certainly, the preferred solution is number 3 and that's what we're working toward with the activity.

Note: For 4 messages the optimal solution is to use sequences of 2 binary messages (AA, AB, BA, BB). For 8 messages you can use sequences of 3 binary states (just add an A or a B to each of the previous 4 messages). For 16 messages, you can use a sequence of 4 binary messages and so on.

Challenge 3: Eight possible messages!

What if you wanted to ask an even more complex question with 8 possible answers? Just as before update your device and test it out. Record how to use your device.

Quick Share / Demonstration / Discussion

Challenge 4: N-possible messages

Could we keep increasing the number of messages forever? Could our devices be used for questions with 16, 32, or 1,000,000 possible responses? Some things to think about...

Topic for thought: How could we use our device to respond to much more complex questions (for example one with 1,000 possible responses). Come up with a system for using your device and describe it in such a way that another group could pick up your device and use it to send messages this way. Give students a few minutes to discuss and write.

Wrap Up

  1. Could we use another group's device to send our set of messages? Why or why not? What would you need to know from the other groups?
  2. Based on what we've learned in today's activity what do we think are the limitations on the kinds of information we can send with binary messages?

Assessment

1. Multiple Choice: A binary question is defined as:

2. Provide an example of a question that could not be answered with a binary message. Explain why this is the case, making reference to the definition of a binary message.

3. Modify your question so that it could be answered with a binary message. Explain why it can now be answered with a binary message.

4. Can you send a message in binary to someone you’ve never before communicated with? If yes, how? If no, what does the person receiving a message need to know in order to successfully decode the message?

5. Why did you choose your particular message encoding strategy? List at least two reasons that justify your decision. List two issues or problems that could be improved in your encoding strategy.

Extended Learning

Standards Alignment