The following experiencial lab was originally submitted to the Poudre School District Goals 2000 project by Dave Swartz in May 1996.
Introduction:
When StarTrek first aired in the mid 1960's, it was an immediate hit. Here was an almost believable journey that everyone could take. The trek usually involved warp speed, which ment breaking the light speed barrier. To this day we don't understand why this barrier exists, and our physical laws as written will not let us ever go any faster. Today you will travel at the speed of light and hopefully walk away with an experience that helps you relate to the vastness of space.
Lesson Title: Where no one has gone before ...
Colorado State Science Standards: Grades 5-8 4.41, 4.43 ; Grades 9-12 1.7, 2.34, 4.42, 6.3
PSD Courses: ICPE, Geospace Science, Physics, Astronomy, possibly 8th grade science
Grade Level: 8 - 12
Estimated Time: Preparation 1 hour. Entire lesson delivery 68 minutes. The activity itself will run 30 minutes for a class of 30. Allow 15-20 minutes or more for an introduction to models and scale. Discuss the scale development and use for this model. Then run through the activity. For in-class completion allow 15 minutes post activity for the student's write-ups.
Floor Printouts: A .pdf file to mark the floor with key travel points used in this exercise: To The Planets.pdf
Compiled/Edited By: Dave Swartz, dswartz@psdschools.org
References: The Nine Planets Web Site by Bill Arnett
Activity Type: Experiential Lab and Writing Activity
Objective:
The student will experience travel at the speed of light (a physical
limit that under current scientific reasoning can not be exceeded)
and learn via modeling how the members of the solar system relate to
each other. The student will also share their impressions of how the
unscaled models they have learned from in the past may have impacted
their views of the true dimensions of the universe.
Teacher Content
Information:
This activity helps students to grasp the true size and relationship
between objects in our local solar system. It dispels myths
introduced by such popular TV programs as Star Trek by pointing out
physical limits and dimensions that are accurate to our scientific
reasoning. The activity utilizes a true scale model, in contrast to
what I like to refer to as "mental" models such as a drawing of the
solar system in a book or the Bohr model of an atom. A true physical
model is accurate in scale, and I have found no other method to
accurately portray our solar system.
Background Requirements for
Students:
Students should be familiar with the concepts of scale and scale
modeling. The student should also have a good command of the SI
measurements for distance and also converting between unit factors.
In addition a good foundation in rate relationships is helpful,
especially distance divided by time - the relationship known as speed
and the vector quantity velocity.
In this exercise, the sun (diameter of 1390000 km), is modeled to be 1 meter in diameter. This makes the scale of our model 1:1390000000 (1:1.39e09). Using this scale, the following relationships between the sun and other solar system objects can be determined.
Object Distance(km) Diameter(km) Scaled Distance(m) Scaled Diameter(m) Sol (Sun) * * 1390000.0 *.* 1.0 Mercury 57910000 4878.0 41.66 .0035 Venus 108200000 12103.6 77.84 .0087 Earth 149600000 12756.3 107.63 .0092 Mars 227940000 6794.0 163.99 .0049 Jupiter 778330000 142984.0 (eq) 559.95 .1029 Saturn 1429400000 120536.0 (eq) 1028.35 .0867 Uranus 2870990000 51118.0 (eq) 2065.46 .0368 Neptune 4504000000 49528.0 (eq) 3238.13 .0356 Pluto 5913520000 2340.0 4254.33 .0017 *(eq) is the diameter at the equator for the gas giants - polar diameters are less. Distances are the mean of the eliptical orbits.
Also, with the distance from the sun to the planets and knowing the speed of light is approximately 300,000 km/second, the time required for light to travel from the sun to the planets can be calculated.
Object Distance(km) Scaled Distance(m) Time
Sol (Sun) * * *.* 0 min 0 sec
18000000 12.95 1 min 0 sec
36000000 25.90 2 min 0 sec
54000000 38.85 3 min 0 sec
Mercury 57910000 (.38 AU) 41.66 3 min 13 sec
72000000 51.80 4 min 0 sec
90000000 64.75 5 min 0 sec
108000000 77.69 6 min 0 sec
Venus 108200000 (.72 AU) 77.84 6 min 1 sec
126000000 90.65 7 min 0 sec
144000000 103.60 8 min 0 sec
Earth 149600000 (1 AU) 107.63 8 min 19 sec
162000000 116.55 9 min 0 sec
Mars 227940000 (1.52 AU) 163.99 12 min 40 sec
Jupiter 778330000 (5.2 AU) 559.95 43 min 14 sec
Saturn 1429400000 (9.6 AU) 1028.35 1 hr 19 min 25 sec
Uranus 2870990000 (19.2 AU) 2065.46 2 hr 39 min 30 sec
Neptune 4504000000 (30.1 AU) 3238.13 4 hr 10 min 13 sec
Pluto 5913520000 (39.5 AU) 4254.33 5 hr 28 min 32 sec
The distance to the next closest star visible in the U.S. Northern Latitudes, Alpha Centauri, is 4.3 light years. In other words, traveling at the speed of light to Pluto takes 5 hours 28 minutes and 32 seconds and traveling to Alpha Centauri takes 4 years 110 days.
On the scale of 1:1.39e09, the distance to Alpha Centauri would be 29,266.4 km, or 18,145 miles, the distance from Colorado directly south along the W105th parallel to the south pole, and then north along the E75 parallel to K2, the second highest mountain in the world, located on the Pakistan/China border. There, you would find another 1 meter
Activity Summary:
Students will travel at the speed of light from the sun outward
through the inner planets of the solar system. The students will gain
first hand knowledge of the size relationships between the diameters
of the planets and also the distances between the planets.
Materials Required:
Procedure:
The teacher needs about 45 minutes to an hour to find an appropriate
facility and set up the lab. A very long hallway (at least 110
meters) works best, outside is OK, and as a last resort, a series of
hallways with bends. The activity has the most impact when the
student can look back the distance they walked and see the "sun".
The teacher should measure out the distances listed above in the student background. If time permits or if the teacher desires, the students can calculate the distances themselves as an activity in factor labeling or development of scale relationships.
Decide where the "sun" will be and then measure outward the distances listed in the table. At each 1 light minute, label the point on the floor using the provided handout. The students will need these reference points to accurately travel at the speed of light.
At 41.66 meters (3 min 13 seconds), use the handout page for Mercury. In addition to the circle on the page, consider placing a small BB or some clay as a physical planet the students can see. Try hanging the small clay model from the ceiling by a thread to show it "floating" in space.
At the other two distances for Venus and Earth, set up similar labels and models.
Once you are ready to do the exercise, have the students line up single file. If possible, have a stopwatch for each student. If not, a stopwatch for every other or every third student will work. It is even possible to do the activity with 1 stopwatch, but it does become a management nightmare!
Have the first student in line start out toward the Mercury model from the sun. The student will need to set a slow pace, and be sure the student knows they can not travel faster than the speed of light. With stopwatch in hand, the student should arrive at your 1 minute marker right on time. You can also include the use of the 10 second interval handout pages. Be sure to demonstrate the speed to the lead person.
I send students out from the sun at 10 second intervals. This could be easily varied depending on the size of the class. VERY IMPORTANT - since this is travel through space, tell the students that they should keep quite during their journey, because in space (a vacuum), you can't hear anyone talk (scream! - wasn't that the saying in Aliens?) The quite time should be used by the student for reflection and thought about the actual sizes involved. After about 3 minutes of travel, even my most squirrelly students have settled into the journey. I usually go up and down the line, suggesting to students they look back at the sun from time to time. The teacher, of course, is allowed to violate the speed of light for classroom management!
As the first student approaches Earth, I usually park myself near the planet. I make sure the student has taken the full 8 minutes 19 seconds for the journey. Once they arrive, I have them look back at the sun model. A very nice feature to point out to them is that when they left the sun model, actual light left as well. When they arrived at the Earth model, the light falling outside also left the sun 8 minutes and 19 seconds ago. The students and the light had parallel journeys.
Also, have the students look at the model sun and then glance at the real sun (only for a second, of course). The diameters of the two are strikingly similar, because your model is to scale.
Be careful with the sun at the other end of the hall. I have had it take off by the tug of a passing student
With your topographic map, mark off the distances from your starting point to the other planets. Mars might be a little too close to show, but certainly Jupiter at more than a half kilometer and Pluto at greater than 4km are best illustrated with a topographic map. I show the orbits as circles, even though this is not accurate. Students can then look on the map for familiar landmarks and get a good sense for the distances. Point out the fact that Pluto is the smallest planet (smaller than the BB used for Mercury), that the sun is only 1 meter in size, and that Pluto is 4 kilometers away! (staggering concept, isn't it?)
Pictures/Images:
The image on the left is a view down the hallway I use for this exercise from where Earth would be on the scale mentioned above. The image on the right utilizes the same lens and was shot through a welder's glass (#10) with the same lens configuration. The true size of the sun is masked by the flare of the lens, but the two images show that the model and the actual sun take up the same arc in space when viewed side-by-side.
Evaluation Procedure:
I take the opportunity of making this an interdisciplinary
assignment. I assign a writing exercise to the students, having them
reflect on their journey. I have varied the writing assignment and
more recently asked the students to consider a science-fiction
approach. For example, they might take on the personality of a photon
of light making the journey, or what the trip would be like for the
first humans to venture these distances. (Remember, it took three
days for Apollo to cover 1.5 light seconds on its journey to the
moon!)
You may want to solicit the help of your Language Arts department in grading the assignment, or even developing a rubric for the assessment.
Other assessments could include variations with scale to fit smaller venues, calculations of the density of the solar system, model building, etc.
Extensions:
There are plenty!
Make other similar models to describe the relationships involved in the parts of an atom. Students would then have a greater realization that matter is mostly empty space.
What are the practical implications for space travel? Will we really make it to Mars in the students lifetime? What will it take to make the journey? How could we communicate with the space travelers if it takes between 4 minutes and 20 minutes (closest and farthest away) for a signal to get to the receiver? Will one of the students in the class be on that heroic mission?
Can you think of others? Let me know by email - dswartz@psdschools.org You could also write to Rocky Mountain High School Science Department, 1300 W. Swallow Road, Fort Collins, CO 80526
My Comments:
Have fun with this activity - I always do! A student can be told the
facts, even watch cool videos like Powers of Ten by
Charles and Ray Eames (Pyramid Film and Video, 2801 Colorado Ave,
Santa Monica, CA 90404, 1-800-523-0118 - $125.00), but I have found
nothing that teaches the concept of size and scale as well as being
able to experience it with this activity.