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ACTIVITY DETAILS

Subjects:
​(primary, secondary, tertiary)
​​Science, Engineering, Mathematics, Technology

Grade Levels (K-2, 3-5, 6-8):  6-8

​Additional Topics:
Deep Space Network
Ratios and Proportions
 
Time Required:  1-2 class periods (45-90 minutes)

Next Generation Science Standards (Website) (hover)
3-5-ETS1-3
3-PS2-2 
MS-PS2-2 
3-5-ETS1-2 
MS-ETS1-2 
MS-ETS1-3 

Common Core State Standards for Mathematics (Website)
​(hover)
2.MD.A.1 

Keywords: 
time, atomic clock

DOCUMENTS

Activity (PDF)
Worksheets (Word)
Design Plan
Testing Data Table
Final Design Summary
Quality Assurance Form
Discussion Questions
​Educator Guide Intro (PDF)
Resources (Word)
Tech Report Scoring Guide
One-Paragraph Essay Directions and Scoring Guide
EDP Scoring Guide
Teamwork Scoring Guide
KEY VOCABULARY
  • atomic
  • accuracy
  • calibration
  • clock
  • consistency
  • Deep Space Network
  • durability
  • electron
  • flow rate
  • hypothesis
  • increment
  • interval
  • precision
  • variable
Picture
NASA's Deep Space Atomic Clock


​Atomic Clock
​

OBJECTIVE
After completing this design challenge, students will be better able to:
  • Explain the difference between accuracy and precision;
  • Explain why consistent, accurate timekeeping is important for space travel; and
  • Use the Engineering Design Process to design, create, and test a water clock that is capable of precisely measuring the passage of time.
​
JUMP TO MENU
  • Objectives
  • Introduction
  • Student Pages
  • Engineering Design Challenge
  • ​Teacher Pages
  • Materials
  • Engineering Design Process
  • Pre-Activity Set-Up
  • Technology 
  • Engagement Strategies
  • Common Misconceptions
  • Assessments
  • Assessment Tools
INTRODUCTION
​If you want to mark the passage of time, you need something to occur repeatedly and regularly, that you can use as a consistent measure for keeping time. Throughout history, humans have used several options for this:
  • A natural astronomical phenomenon,
  • An artificial, human-made device, or
  • A combination of both natural phenomena and artificial devices.
Timing devices that rely on natural phenomena include the observation of astronomical patterns, such as the movement of the sun during the day, or the location of stars and planets in the sky.
 
Artificial devices may rely on mechanical or chemical means.  This includes clocks that measure time by the rotation of gears, or an hourglass that uses the flow of a specific volume of water or sand to represent a specific period of time.
 
One example of a clock built by humans but relying on a natural phenomenon is an atomic clock.  Earth-based atomic clocks keep very precise time. The best will be off by only one second in 300,000 years. Atomic clocks work not by counting grains of sand or drops of water, but by counting the movement of electrons. These clocks are important for government, military, and astronomy applications, but also for everyday use -- like using GPS to find the nearest gas station!
​
As shown in the video: Sammy-the-Second and Atomic Clock, keeping precise time is essential for navigation of satellites and spacecraft. If the time is incorrect, even by a few seconds, a spacecraft could be moved off-course by many miles, possibly missing the planet it was trying to observe, or even colliding with an object that would damage the spacecraft.  The large effects of even very small changes create particular challenges for NASA engineers when developing navigation and timing systems for spacecraft.
Video: Sammy-the-Second and Atomic Clock (3:58 minutes)
NASA’s study of Atomic Clocks for use in space is changing the way we conduct deep space navigation.  Earlier missions have needed to communicate with Earth or another satellite in order to process data and navigate, which itself takes time and may affect the course of the spacecraft.  By keeping time onboard the spacecraft, spacecraft computers will be able to process data immediately, which will allow for better handling of time-sensitive events.
 
Challenges to Deep Space Time Monitoring
 Just like Earth-based atomic clocks, the Deep Space Atomic Clock is a very complicated machine that will also have to be able to survive the harsh environment of space travel. Spacecraft travel through space at about 17,000–36,000 miles per hour. The spacecraft needs to be responsive to external and internal factors in order to make landings and critical changes to orbits possible.
​
​Water Clocks
Today, you will create a water clock, which is different from an atomic clock.  A water clock is one of the oldest types of clocks, and has been used by humans for thousands of years.  Water clocks use the flow of water as a means of measurement, comparing water levels with pre-determined measurements in order to measure the passage of time.  There are many different types of water clocks, but the underlying principles of measuring changes in water volume or counting flow rate are the same. 
 
While the basic setup of a water clock seems simple, you may discover that creating an accurate timepiece using only water can have some challenges.  In particular, accurate timepieces require both precision and accuracy.  Read the sidebar to learn more about these important features.
What is the difference between precision and accuracy?
Precision and accuracy are often confused.  What is the difference? 
  • Accuracy is how close a measured value is to the actual (true) value.
  • Precision is how close the measured values are to each other.
So, if you are playing basketball and you always hit the backboard in the same place but never seem to score, then you are not 
​accurate, but you are precise!  Something may be accurate, but not precise; precise, but not accurate; accurate and precise; or neither!  Your water clock should be both accurate and precise! It should measure time accurately, and each measured interval should be the same value.
​
How might you remember the difference between these two important terms?
  • Accuracy is Awesome! (hitting the correct spot)
  • Precision is rePeating (hitting the same spot each time, but maybe not the correct spot
ENGINEERING DESIGN CHALLENGE
Your challenge is to design a durable water clock that will record precise and accurate measurement of the passing of time. You will revise your design to improve your device’s performance for multiple tests.

Design Requirements:
  • Accuracy:  Water clock must keep accurate time, within 3 minutes at any point.
  • Precise:  Water clock intervals must be consistent, within 30 seconds of each other.
  • Durability: Water clock must keep time for at least ____ hour(s) without breaking down.

Design Constraints: 
  • Only materials provided may be used to create the water clock.
​
REMINDERS!
  • Be sure to address all design requirements and constraints.
  • Document all design development and modifications.
  • Record all test results.​
Teacher Tips
  • Review the Engineering Design Process with students. More information about the Engineering Design Process and its use at NASA may be found in the NASA’s BEST Activity Guide Introduction.  Instructional videos may be found at NASA’s BEST Activity Guides.
ENGINEERING DESIGN PROCESS
Student Procedures

​ASK
  1. Identify the problem in this design challenge. 
  2. With your team, review the Engineering Design Challenge and highlight design constraints and requirements. 
  3. Identify questions and concerns you have about the challenge and discuss them with your team.
 
  IMAGINE
  1. Brainstorm possible solutions to the Engineering Design Challenge.  What information do you need in order to create a successful water clock? 
  2. Brainstorm ideas about what materials will work best to improve your measurement of time.  What will you test first?  What special features will you include?
 
  PLAN
  1. Draw and label your timekeeping device on the Design Plan.
  2. Include measurement and label all components.  You should include at least two perspectives (e.g., top view, front view, side views) of your device.  Include instructions on how to use your water clock.
  3. Write a hypothesis that identifies one or more variables that you will test to determine accuracy and/or precision of your clock.
  4. Submit your completed drawing and list of materials to your teacher for approval before continuing through the Engineering Design Process.
 
  CREATE
  1. Create a prototype, or working model, of your water clock.  Remember to consider design requirements and constraints as you build from your plan.  Your device should be able to work for at least ____ hours and measure time accurately within 5 minutes. 
  2. On your Testing Data Table, note any changes to your design as you build.​
Teacher Tips
 
ASK
  • Review Student Pages, which provide additional detail and background information on the engineering design challenge.
  • Have student teams review the design challenge and identify design constraints and requirements.  Use the NASA’s BEST Glossary List (in Reference Material) to review critical vocabulary prior to the activity.  Help students answer any questions they have about the challenge.
IMAGINE
  • You may wish to take students to the school library to conduct research. If a provided link is broken, students may easily search for information at the following sites:
  • A common question for students will be, “How do we mark the time increments on our clocks?” There are several ways to do this; the students should determine this solution on their own. See the Pre-Activity Step-up section for more information.
 PLAN
  • Students should consider the underlying principles of a water clock.   In the PLAN step, students are asked to form hypotheses related to the aspects of their devices that will be tested.  You may wish to suggest examples, such as: The ____ is the most important factor for precision of our clock, while _____ is the most important factor for accuracy.  (Note: this may or may not be the same variable!)
  • When filled, the upper container drips at a constant rate to the lower container. Students will need to determine how large to make the hole for the water to drip through. The hole needs to be big enough to have water flow through, but not so big that it streams (rather than drips) out. The hole may be in the center or on the sides of the container. If the hole is too large, plumber’s putty may be used to plug it up.  Students may then make a new hole somewhere else on the container.
  • Students will also need to determine how to mark the increments of time on the outside of the lower container or on a piece of paper. 
  • Before allowing students to move to the next step, require design sketches and materials list to be submitted for your approval.
CREATE
  • Students will experiment with the flow rate of their design to get a consistent flow of water.  One concern is for the device to allow a flow that is slow enough to count, but fast enough to calibrate in the given time.
  • Remind students to consider design requirements and constraints as they build their water clocks.

​Safety Concerns
  • Students should keep common sense safety in mind.
  • Students should exercise caution when using scissors to puncture holes in cup or can bottoms.
TEST
  1. Evaluate your solution by conducting tests on design effectiveness. 
  2. After determining that you have a constant and consistent flow of water, calibrate your device by measuring the flow rate for 60 seconds.
  3. Record this information in the Testing Data Table.  Remember to mark water levels on your device in minute increments.  Record drops/minute.
  4. Complete the Testing Data Table.
 
  IMPROVE
  1. Consider how to improve your design to maximize precision and accuracy.  Refer to your hypothesis, and improve the design of your water clock.  Continue to revise and test your design until you feel confident that you have the most effective water clock possible. 
  2. On the Final Design Summary, Describe the design of the your water clock final design,  draw and label your revised model, and provide revised instructions of how to work your Water Clock. Once you have completed this worksheet, check with your teacher before asking another team to review your design.
TEST
  • After obtaining a consistent and constant flow of water, students will fill the upper container with water and determine the actual flow rate (drops of water per minute).
  • Students will test and improve their water clocks.
  • After completing the challenge, another team will test the accuracy of their clock.
IMPROVE
  • Students will spend much of the time allocated for improvement experimenting to obtain a  constant and consistent flow of water.  If time allows, they could make further adjustments to their water clock. If time does not allow for a complete retesting, students should write out what changes they recommend and expected effects of those changes on their results.
  • After testing, students will finalize model to share with a Review Team.
SHARE
  • Have students present their solutions and results by completing the Quality Assurance Form with a Review Team.
  • Engage students in class discussion using the questions in Discussion Questions.​
  SHARE
  1. Meet with another team and present your timekeeping devices.  Be sure to review the Quality Assurance Form and be ready to identify your device strengths and areas of additional improvement.
  2. Complete the Water Clock Quality Assurance Form for the other team.
  3. As a class, review class data and complete Atomic and Water Clock Discussion Questions.
  4. Complete a one-page Technical Report on your project.
​
MORE FUN WITH ENGINEERING
 
Extend Your Study of Water Clocks
  • Test different materials or shapes for the clock.  Do materials affect flow rate?  Accuracy?  Precision?  Durability?
  • What would happen if you used something other than water to run your tests?  Repeat your test with other liquids (e.g., juice) or even solids (e.g., sand) provided by your teacher.  What, if anything, changes?
 
Explore More About Deep Space Atomic Clocks
In your experiments today, you replicated a form of timekeeping that has been around for a very long time: a water clock.  Just as you found ways to improve upon your water clock, NASA is constantly looking for ways to improve upon atomic clocks.  Learn about some ways NASA does this at the link below.  During your design challenge, you did not have to worry about the harsh conditions in space.  For example, how do you think a microgravity environment would affect the performance of your water clock?  

NASA engineers have previously used atomic clocks in space, and in preparing for future missions, such as the Deep Space Atomic Clock, they must make changes and improve on current technology.  Data on how atomic clocks withstand various conditions will allow NASA to further improve time measurement devices, which will help ensure mission success as we explore the universe.
Use the links above to research the history of atomic clocks and about future NASA missions regarding them.  Then answer the following questions:
  1. How do water clocks compare with atomic clocks?  What are differences between thm?
  2. What are different ways future Atomic Clocks will improve for future DSAC missions?
  3. How will NASA test future Atomic Clocks?
  4. What environmental conditions do you think NASA should try to simulate on Earth to prepare the for DSACs?
  5. What changes would you need to make to your water clock so that it could be used in space? 
TEACHING STRATEGIES

MATERIALS
  • Flat-bottomed plastic bottles/large containers (various sizes, 250 ml to 2 L) – at least two bottles of the same size per team
  • Ring stand or sturdy materials to construct a stand (e.g., wood, PVC, blocks) that will allow students to elevate an upper container and hold water above a lower container
  • Pin/thumb tack to pierce hole in container
  • Source of water
  • Ruler/measuring tape (with centimeter markings)
  • Stopwatch
  • Paper to use for increment markings (may need tape to attach to lower container)
  • OPTIONAL:
    • Plumber’s putty or waterproof tape
    • Food dye (for better visibility of water drips)
  • Other materials (as available)
 
PRE-ACTIVITY SET-UP
  • Decision Point - Before providing students with copies of Student Pages, the teacher should decide on a time limit for the activity and fill in the appropriate blanks under Introduction and on the Water Clock Design Plan.
  • Time Concerns - This activity may be completed in one class period; but for best results, students should observe the water dripping over a longer period of time (i.e., several hours).  The Testing Data Table is designed for students to collect data over a period of time.  Students do not need to record every individual drop, but should take readings at least every 15-30 minutes.  If time is a constraint, you may need to adjust the worksheet requirements and have students estimate their results.  For shorter collecting periods, use only a small amount of water so that students may observe and track what happens when the upper container is nearly empty. Additional research and background investigations may require a additional time before students engage with the design challenge. 
  • Work Area - Identify an area where the students are able to keep their water clocks elevated above the container that will collect the water. A wire shelf will work; alternatively, students may construct something that will allow water to drip down into a container below.
  • Calibration Process – Before running the full-length data collection, students are asked to count the number of drops that occur in 60-second increments and make marks on the lower container.  The number of drops that fall in one minute is the flow rate; students should calibrate their clocks using the flow rate before running the longer test.  Students should mark the water level in 60-second increments (either on the container itself or on a paper that can be attached to the clock – a paper measurement better allows for students to make adjustments without affecting the container).  The goal of this calibration is for students to develop reliable markings in order to see how much time has passed based on water flow.
 
USE OF TECHNOLOGY
  • Students may wish to use graphing software in order to present and/or analyze the data they collect during the testing phase.
  • If time and availability permit, students may opt to design their clocks using computer design software, and even use 3D printing to create clock components.

ENGAGEMENT STRATEGIES
  • Use a KWL chart as an introductory activity to help students identify what they know, want to know, and learned about the engineering design process.
  • After reading the introduction, students might complete a Venn Diagram on the similarities and differences between atomic clocks, water clocks, and electric clocks.
  • Ask students to come up with ways they can mark the passing of time.
  • Connect the challenge to NASA by discussing the development of the Deep Space Atomic Clock to provide precise time and therefore precise navigation in deep space. 
 
COMMON MISCONCEPTIONS
  • Students often have difficulty distinguishing between accuracy and precision, and care must be taken to explore the meaning of these terms without conflating them.
  • Some students do not recognize that there is uncertainty in all measurement, and that no measurement is exact.  They may also believe that all error can be eliminated through better, more detailed procedures or by using particular types of high-tech equipment, and cite “human error” as an explanation for irregular results.  It may be worthwhile to discuss how all measured values include some degree of uncertainty, even when instruments are accurate and precise.
 
 ASSESSMENTS
  • Water Clock Design Plan
  • Water Clock Testing Data Table
  • Water Clock Final Design Summary
  • Water Clock Quality Assurance Form
  • Water Clock Discussion Questions
    • Questions for this activity primarily focus on observations made by students in the course of testing their projects; students should be prompted to be as thorough as possible in their responses.
    • Answers to Selected Questions:
      • 3 & 4: Responses should include some discussion about effects of water pressure based on the water level in the upper container.
      • 8 & 9: Responses should be specific to either precision (question 8) or accuracy (question 9) without conflating the two. 

ASSESSMENT TOOLS
  • Technical Report Scoring Guide
  • Engineering Design Process Rubric
  • Engineering Design Process Teamwork Rubric
  • Water Clock 1-Paragraph Essay Directions and Scoring Guide
    • Student Prompt:  In this activity, you designed a water clock that was required to be durable, accurate, and precise.  You followed the steps of the Engineering Design Process to brainstorm solutions and research ideas, plan and sketch a design, build a model, evaluate the model, refine and optimize your model, and share your results. Choose one of the following questions and answer with a one-paragraph essay.
      • Compare and contrast the similarities and differences between an atomic clock and a water clock.
      • How did what you learned through the engineering design process help you understand how NASA engineers might design an atomic clock for use in deep space?
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