Overview: With teacher guidance,  students discuss and model the yearly cycle of the Earth. Then they create a 3D animated computer model of the Earth and Sun which demonstrates the cycles of the days, months and seasons. Their model should show the Earth revolving around the sun, and rotating  around its own axis which is tilted at a 23° angle to the plane of the Earth's orbit around the sun.  They should be able to use the model to explain the cause of day and night and the seasons of the year.  More advanced students should add the moon to their model and use it to explain the phases of the moon.  This can then be extended to explain the relation of the lunar cycle to the monthly and yearly  pattern of low and high tides. 

Topics: 
     Earth Science:  Astronomy 
     SciVis:             3-D modeling with primitives, spatial relations, 3D Animation, use of lights and cameras, 
 

NC Scientific and Technical Visualization Objectives:

Level I: 

2.00     Apply problem solving and design concepts. 
5.02     Produce computer based concept visualization projects 
5.04     Transfer computer based visualizations to output devices 

Level II: 
4.04     Apply advanced 3-D animation techniques 
5.02     Produce an integrated multimedia presentation 

NC Earth and Environmental Science Goals and Objectives (1999 Revision):
 

6.02    Analyze planetary motion and the physical laws that explain that motion: 

Rotation 

Revolution 

Apparent diurnal motions of the sun and stars. 

Tilt of the earth's axis. 

Parallelism of the earth's axis. 

Teacher Information

It is essential for teachers to realize that many people have serious misconceptions about the causes of phenomena such as seasons, lunar phases, tides, eclipses etc.  For example,  a common misconception is that the earth is further from the sun in winter than in summer. (In fact the Earth is closest to the sun in December which is winter in the Northern hemisphere.)  Research shows that these misconceptions are held even by many college graduates,  so do not expect your students to understand these phenomena without assistance!  These misconceptions sometimes arise from a combining personal experience with poorly understood previous instruction and misinterpretation of pictorial drawings in Earth Science textbooks. These misconceptions  powerfully shape student  understanding of new material including diagrams, videos, role play and teacher explanations.  Asking students to create their own visualizations can help the students overcome previous misconceptions and come to a more scientific understanding of phenomena.    Before students start to create their computer based visualizations  teachers should be sure students have a basic understanding of the Earth's daily  and yearly cycles.  This can be accomplished by simulating these cycles with a lamp and a globe in the classroom.  The teacher's role is to ask probing questions challenging misconceptions.  This is an essential role - otherwise the students may create visualizations that reinforce misconceptions.   Question students carefully to be sure they understand before proceeding to independent work! Continue to challenge them with questions as they create their visualizations.  Some links to material about misconceptions are given below in the reference section. 

Another area of difficulty for students is the relative sizes and distances involved.  The radius of the sun is approximately 218 times as large as the Earth, so any visible scale model of the Earth will not fit on the same page or computer monitor image as the Sun. You can simulate this with a ball with a 2 cm diameter (e.g. a large marble) to represent the Earth , then, ask  students to figure out the size of ball they need for the sun.  (It would need to be 4.36 meters in diameter).  Then, using the same 2 cm diameter marble to represent the Earth, ask how far away the center of the sun should be.  (It would need to be 234.81 meters away - more than  two football fields laid end to end!)  So the  students cannot create  a scale model, but must instead adjust the scale to fit the display medium while maintaining visibility of all features.   If the model of the sun is created to be relatively small, it will appear further away. 

The design brief focuses on the first group of questions below.  Teachers may want to modify the design brief for a more advanced group by including the second and third set of questions. 

Questions:  Discussion and visualizations should focus on answering the following questions.  The animation and associated presentation should answer these questions visually. 

1. What causes night and day? 
2. What causes the seasons?
3. Why are the seasons in the Southern Hemisphere opposite to those in the Northern Hemisphere?
4. Why are the days longer in the summer than in winter?
5. What causes the apparent changes in the sun’s position during the year? 

1. Why does the moon go through phases?
2. Why does the moon rise a little later each day?
3. What causes the tides?
4. What causes lunar eclipses?
5. What causes solar eclipses?

1. What causes the difference between a sidereal day and a solar day?
2. What causes the difference between the sidereal period and the synodic period?

Unlike many of the other design briefs featured on our web site, in this project all of the students will be working on very similar animations.  This can be used to good effect by the teacher in leading class discussion of the importance of camera placement and lighting techniques and in raising the question of tradeoffs in quality versus production time and file size. 

References

    On-Line

Astronomy

• Astronomical data from the U.S. Naval observatory at http://aa.usno.navy.mil/AA/   Lots of data related to the position of the sun  and moon. For example students can query the system to find out the exact time of sunrise for any given day and place.
• NASA's Space Science Data System at http://ssds.nasa.gov/  with links to data and pictures.
• The National Space Science Data Center has information on the solar system at http://nssdc.gsfc.nasa.gov/planetary/planetfact.html.
• Bad Astronomy at  http://www.badastronomy.com/bad/misc/seasons.html This site counters a common misconception with data and calculations.
• Ask a Space Scientist  at http://image.gsfc.nasa.gov/poetry/ask/askmag.html#list  This NASA sponsored site answers astronomy questions including whole sections of questions related to Earth's rotation, phases of the moon and the tides.  Students can send in new questions.
• Solar System Live at http://www.fourmilab.to/solar/     This site allows you to enter the date and a number of other parameters and then view the relative positions of all of the planets.
• Solar system information from a Cornell University course outline at http://astrosun.tn.cornell.edu/courses/astro201/solar_system.html
• The equation of time is explained at a a Sundials on the Internet  information page at: http://www.sundials.co.uk/equation.htm. and also on a Royal Observatory at Greenwich site at http://www.rog.nmm.ac.uk/leaflets/equation/equation.html.

Misconceptions

• The Private Universe Project at http://www.learner.org/teacherslab/pup/  This is a fascinating project.  The original project videoed an exploration of  people's ideas about various science topics and did a series of on-air teacher workshops.   Now there are on line lessons for students and teachers.
• Bad Astronomy at  http://www.badastronomy.com/bad/misc/seasons.html   This site counters a common misconception with data and calculations.

Design a multimedia presentation to explain and illustrate the movement of the Earth relative to the sun. 

Scientific concepts which must be covered: 
Do not just answer these questions  with words - use graphics to explain them!!!

1. What causes night and day? 
2. What causes the seasons?
3. Why are the seasons in the Southern Hemisphere opposite to those in the Northern Hemisphere?
4. Why are the days longer in the summer than in winter?
5. What causes the apparent changes in the sun’s position during the year? 

written discussion of scale used 
electronic presentation 
4 - 2 or 3-D  graphics (day, night, summer, winter) 
one animation of earth showing rotation and revolution 
reflection 

Steps:
 

1.  Develop understanding of your topic

      Research the following facts about the Earth's movement in Space:
 

Earth's  period of rotation
Earth's period of revolution
Earth's diameter
Earth's average distance from sun
Earth's angle of tilt
Sun's diameter

Look closely at these numbers:  How many times does the Earth rotate as it completes one revolution?  Is it possible to create an accurate scale model of the Earth and Sun and the distance between them on a desktop size piece of paper?  What difficulties do the relative sizes and distances cause?  Write a short description of the problems and your solutions. Turn in to teacher 
 

2.  Plan your presentation

Plan your overall presentation 
Develop storyboards for the animation, be sure to include lighting and camera placements.  Turn in to teacher
Develop a plan of action and divide up the responsibilities for your group. 
List the group members and which part of the project each will be responsible for. Turn in to teacher.

3.  Execute your plan

Set up overall slide presentation. 
Work on graphics and and insert into presentation. 
Work on animation and insert into presentation.

4.  Review Your Progress

You  should now preview your presentation as a whole making sure that it all works, fits together coherently, answers the design brief question, and meets all the project requirements.  Make any needed improvements.

5.  Present Your Project

Present the project to the class.
Ask the class for their comments and suggestions. 
Save your project on electronic media. Turn in to teacher.

As a group,  write a reflection explaining at least three strengths of your project, what problems you had to overcome to produce it and detailing what you would change about it if you could.  This should be word processed and  no longer than 1 page.  Turn in to teacher.

Team Members: __________________________ 

Available Software: ___________________________ 

Available Hardware: ____________________________ 
 

Evaluation Criteria:

 Success will be measured by the following criteria:
 

data and written discussion of scale problem	5
project planning	5
storyboards	10
graphics clear - easy to see and understand	12   (3 ea.)
graphics labeled in appropriate font for easy readability	4
good choice of colors, appropriate backgrounds	6
animation works	6
animation illustrates cause of day and night (rotation)	6
animation illustrates cause of  seasons (tilt of axis,  angle of light, day length)	10
overall project - scientific concepts clearly explained	5
- appropriate fonts	3
- consistent style	3
- attractive,  holds viewer's attention	2
oral presentation to class - concepts explained clearly and accurately	5
all group members participate	3
speak clearly	3
face audience	2
reflection	10
Total	100

Extensions:

Possible extensions include adding the moon to your presentation, visually comparing the Earth to one of the other planets, actually presenting this to earth science classes or middle school students, producing a CD ROM for Earth Science or middle school classes to use.