Units & Systems

Once Upon a Unit....

Imagine that every country on Earth uses its own measurement systems. This approach was once the way of the world. Units were based on the sizes of parts of the body.

What are some problems with using body parts as a system of measurement? Three of these body-based units are used currently but have been standardized.

​

Before writing, help students envision what the effect would be if every country on Earth used its own measurement system.

Show the slide with eight units that were based on parts of the body: digit, inch, hand, span, foot, cubit, yard (nose to fingertip), and fathom.

Sample response:

Some problems with using body parts as a system of measurement are that they are not easily converted from one unit to the next, and each person's measurements are different. The inch, foot, and yard of a smaller person would be smaller than that of someone taller. Because one's height and arm span are correlated, five old-fashioned, body-based yards of cloth sold by a six-foot-tall person would likely cost the same as six yards sold by someone only five feet tall.

For entertainment, you can read some names from this delightful list of obsolete units.

Make the Case for The Universal United Unit Union

We've imagined that every country on Earth uses its own measurement systems. However, there has been some talk recently of trying to develop one system that everyone could share. But this new movement has no leader—until now.

​YOU are responsible for delivering a speech to the United Nations about the benefits of a unified standard system of units. Describe examples of how countries could better cooperate in science, enjoy sports, trade goods, etc.Alternatively, you may choose to write a speech against the idea of a unified standard system if you prefer.Use the focus words; they can help you make a better argument.

​mass • weight • volume • capacity • length • distance • standard • unit

The writing prompt asks students to make the argument for or against a standardized, worldwide system of measurement. Students should include examples of how this system would benefit (or have a negative impact on) science, sports, and business.

Remind students to use the focus words.

Paraphrase:

It is your job to argue well for the position you are assigned. Use information on this page as well as information from the prior sessions. It is also a great time to use your previous notes and the unit's focus words; they can help you make a better argument.

For ideas about how to run a class debate, click here.

​

Ask students to share their points and counterpoints.

You may want to use the Reading to Learn Science strategy, Argument Lines, to discover students who are on the pro and con sides of this debate. Argument lines are a tool for improving discussion of a scientific question with two plausible answers. The two answers are posted at opposite ends of the room, and students line up between them, standing close to one answer if they believe it’s correct, or in the middle if they aren’t sure. You can then prompt adjacent students to talk with each other, explain and justify their positioning, and redistribute themselves along the line if their ideas have changed. You can also expand these discussions to the whole class, asking students to explain and justify where they are standing individually (“Explain why you are standing close to Choice B, but not all the way there.”) and relative to each other (“Explain why you are close to Choice B, but not as close as your classmate who just spoke.”) As discussion continues, students can keep repositioning themselves on the argument line to reflect their changing views.

End this lesson with a general discussion during which students share their own comments and raise their own questions.

Students may prefer to take one side of the debate or the other. If you expect students will not divide evenly, you may consider randomly assigning them roles or sides in the debate.

It may be useful to refer to this activity and discussion if you teach the next unit, U2: Measuring Up Metric.

The PDF linked below shows the history of the metrication movement in the U.S.

​

Hearing from Both Sides and Viewpoints In-between

How strongly do you feel about this topic? Line up in your classroom. If you believe the entire population of Earth should use a unified standard system, stand at one end of your classroom. If you think such a unified system of units could have a bad effect on science, sports, trade goods, etc., stand at the opposite end. If you hold an opinion less strongly, stand somewhere between the two ends.

​