• Measuring Time

    Overview:  In this unit students will explore the use of natural phenomena, such as shadow tracking and the phases of the moon to keep time, as well as investigating invented clocks, using some of the instruments that have been used to keep time throughout the centuries.  They will build and experiment with a water clock, sinking water clocks and investigate the characteristics of the pendulum. Finally, they will complete a small group research project focused on one specific aspect of time: measuring time, physics of time, and the psychology of time.  The unit provides students with an opportunity to learn how time has been measured, to investigate machines, to explore concepts such as energy and motion, to learn about the science of astronomy and to explore various aspects of time across disciplines.

    Unifying Concepts and Processes:

    • Evidence models and explanations
    • Constancy, change and measurement
    • Systems, order and organizations
    • Form and function

    Goals for Measuring Time:  In this unit students investigate the history of timekeeping and experiment with various timekeeping devices.  From their experiences, they are introduced to the following concepts and skills:


    • Time can be measured by observing the natural cycles of the sun and the moon.
    • Shadows cast by the sun can be used to measure and predict the passage of time during the day.
    • The phases of the moon follow a cycle that can be used to measure and predict intervals of time during a month.
    • Mechanical devices can be constructed and used to measure specific intervals of time consistently.
    • The accuracy of mechanical clocks is dependent on their design, the materials from which they are constructed, and their energy source.


    • Observing and recording information about the natural cycles of the sun and the moon.
    • Learning to plan and conduct experiments in which variables are controlled.
    • Predicting and testing how changing a variable affects the outcome of the experiment.
    • Communicating results through writing in notebooks; organizing information in charts, tables and graphs; and discussion.
    • Reading and researching science materials for information.
    • Applying previously learned concepts and skills to solve a problem


    • Developing an interest in exploring and investigating time.
    • Recognizing the importance of repeating test to validate results.
    • Appreciating the advances people have made in measuring time and explaining natural phenomena. 

    Assessment:  Assessment strategies include examination of matched student pre and post unit assessments, written self-assessments, and student record sheets, graphs and drawings, as well as observations of growth in scientific skills and contributions to class discussions.  An embedded assessment in Lesson 16, in which students design and build their own one-minute timer, provides information on a student's ability to apply what they have learned about timekeeping devices. Additional assessments at the end of the unit challenge students to respond, orally or in writing, to questions that are based on unit investigations of clocks and to make predictions about the changing appearance of the moon.


  • Water Clock Experiment