Date: April 7, 2000

Grade Level(s): 3, 4

Subject(s):

• Mathematics/Measurement

Description: A lesson comparing the Metric system of measurement to the English system. Deals with the recent failed probe to Mars, and how these systems of measurement were involved in that problem.

Goals: To answer the question: will using two differing systems of measurement to construct something cause problems?

Objectives: Students will:
1. explain why the Polar Lander NASA sent to Mars, missed.
2. explain how the two systems of measurement are different

Materials:

Per group of two: Ruler (metric or English), worksheets, sheet of 8½ x 11" paper, dictionary, new pencil

Overhead projector

Worksheets/Overhead projections (Here's What We Think & Here's What We Found)

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Scientific Explanation:

There are about 2½ centimeters in an inch. America is one of the only countries still not using the metric system of measurement. The metric system bases itself off one standard, and increases by increments of 10. For example:

1 meter=10 decimeters
10 decimeters=100 centimeters=1 meter
10 centimeters=1,000 millimeters=1 meter
10 meters=1 decameter
10 decameters=100 meters=1 hectometer
10 hectometers=1,000 meters=1 kilometer

Scientists usually measure things using the metric system. So, American scientists need to know how to convert to the metric system in order to communicate with scientists around the world. In order to find out what the students already know about the metric and English systems of measurement, ask them questions. For example, Can anyone tell me something they know/think they know about the Metric system? English system? What things do you want to know about these two systems? Record their responses by writing them on the chalkboard, overhead or chart paper. Central Science Question: Will using two differing systems of measurement to construct something cause problems?

Focus Phase:

Do you remember hearing about the probe (The Polar Lander) NASA sent to Mars recently? Everyone was very excited about the mission. The probe was supposed to land on a part of Mars that had not been studied before. It was going to collect samples of materials found in the atmosphere and take photographs of the polar region of the planet. Scientists world-wide waited expectantly for the first reports from the probe, but they never came. As the days passed, they gave up hope and began looking for possible causes of the failure. What they discovered was this: U.S. scientists had used English measurements when programming a portion of the system. The rest of the system had been programmed using metric measurements. Do you think that this could have caused the mission to fail? Write down what you think and why.

Challenge Phase:

We're going to experiment for ourselves to see if we can determine if using two different systems of measurement could have caused this error. How do we determine the measurement of something? Divide the class in half. Ask students to make predictions about the measurement of five items (student desk, the dictionary, a sheet of paper (8½" by 11"), a new pencil and an item of their choice) and write them down on the worksheet. Allow them 5-10 minutes to complete this portion. Then provide them with rulers, ½ the class with English system and the other ½ with metric system. Have them write down the actual measurements on their measurement worksheet. (Be sure they circle the system of measurement their group uses.) Ask them how they think their measurements will compare with those of their classmates.

Concept Introduction:

Ask students to share the results from their investigations. Create a chart of the data together on the overhead using the "What we found…" worksheet. Have member from the different groups share their findings with the rest of the class, or have individual students come to the overhead and write down what they found. Have the rest of the students agree/disagree with the answers. If they disagree have them explain why. Ask: What is the difference between the measurements in centimeters and the ones in inches? (They should notice that the measurements in inches are smaller numbers than those in inches.) Do you think you would always get the same results? To reinforce the idea, have students take the measurement of their chosen object with the measuring tool they did not use (metric/English). Then ask them to compare the results to see if they seem to fit with the rest of the results.

Concept Application:

Ask students if their prediction about what happened to the Mars probe has changed. Why or why not? What from this lesson backed up or caused you to change your first idea. Do you think that what you have learned will always be true? Ask them to write down their answers to these questions. Explain to them that the Mars probe actually overshot Mars and kept going in space because the two units of measurement that were used are different. In order for the mission to have been successful the probe would have needed to be programmed with the same exact unit of measurements. On the chart from the beginning of the lesson, write down what students now know. Ask if there are things they still want to know.

Assessment: The students will demonstrate science understandings by:
1) explaining that the probe overshot Mars because two different units of measurements were used.
2) correctly predicting that measurements in centimeters will always be a larger number than the number of inches in a measurement.
3) their ability to identify things they now know about the differences between the English and Metric systems of measurement.