OK, we’re back for part 2. Remember that our goal is to impart an intuitive, long-term understanding of how comet tails work. Iâll give you an observation worksheet that students can use during the Comet Running game, but if time or attention-spans are too short for a worksheet, dispense with that element in favor of learning through movement and Socratic dialogue. (What? You think an engineer wouldnât have read the Greek philosophers?)
If you have time and enough outdoor space for the âGameâ version of this simulation, move right along to “Stage 2” now. The promise of a chance to make their own models is what will entice the students back to the classroom. Otherwise, save the great outdoor model for another time or place and move directly to “Stage 3,” building the individual models.
Stage 2: The Game
That’s One Big Comet
This is an outdoor game, and it works to best advantage with a nice BIG comet model. Four five-yard lengths of white fabric streamers attached to a single badminton shuttlecock (âbirdieâ) make our Comet Chase model. A playground ball or a soccer ball (around 8â in diameter) stands for the sun.  Sort the participants into groups of no more than five and no fewer than three, and move to the great outdoors. A grassy area is safest, because this game involves some complicated running; if youâre stuck with pavement, tone down the running to âjoggingâ and allow a little extra time.
Start by laying out the ground rules for the game. First, each group will get to play every role. There are three parts: being the sun, being the comet, and being observers back on Earth. Remind everyone of your local rules for behavior outside. Itâs harder to listen to instructions out in the sunshine and fresh air!
Take a moment to review the lesson so far. Place the model Sun on the ground, at least ten yards away. Ask an adult helper or one of the students to stand about halfway between the class and the Sun and to hold the head of the comet
Large Comet Head With Coma
while you extend the tailâs long white streamers.  This model is much more evocative of the scale of a real comet, which has a tail tremendously longer than the diameter of its coma, or headâbut itâs still not a scale model. Allow for some oohs and aahs, but move on to your query: which direction should the cometâs tail point? Donât move yet; both you and your helper just stand in place.
Large Comet: Incoming or Outbound?
Donât be concerned if it takes more than one answer to get the right one! Some may still want to know which way your comet is moving. But in a few moments, you should achieve the consensus that the tail should point towards the class and away from the sun.
Now, add the movement and ask everyone to call out which way for you to move. Ask your helper to start walking (slowly, please!) towards the sun and then to loop around the sun. You will need to move quickly to keep the cometâs tail pointing away from the sun. In fact, even if your helper cooperates by walking slowly, you will need to break into a run! As you run, if the students arenât already hollering directions to you, tel them to keep reminding you which way to point the tail: away from the Sun!
Pause partway and while you catch your breath you can demo a technique for helping to align the tail while in motion. With your outside hand, hold the streamers. With your inside hand, point at the Sun. The tail-runners should always find that pointing at the Sun also means pointing at the cometâs head.
Now, it is finally the studentsâ turn. Run as many iterations as necessary to ensure that each group does each job at least once. For instance, for a class of 20, allow time to run the game at least four times.
The Comet Group: The comet group needs one Head and up to four Tail-Runners. Name the comet after the person whoâs serving as the Head. Comets are always named according to the last name of the cometâs discoverer. So if you have Robin Williams as the cometâs head, then this will be Comet Williams. Getting the comet named after him/her may compensate for the fact that the âheadâ only gets to walk slowly around the sun.
Meanwhile, the tail-runners get to hold the ends of the tail streamers and run to keep the cometâs head between themselves and the Sun. In the normal course, the âtailâ group will tend to lag a little and spread out, but that actually serves to more-accurately represent the shape of the dust tail. If youâre working with a two-tails group, designate one especially determined runner to represent the ion tail by taking one ribbon and maintaining a straight line from the ribbon end through the comet head to the sun.
The Sun Group: The sun group stands in the middle of your running space. One or two group members hold the model sun overhead. This makes it easier for the Comet group to see if they have successfully aligned the comet head and the sun. If the tail-runners stray out of line, members of the sun group need to to shout out âGot you! Got you!â or “Solar Wind Coming!” to warn them that the solar forces are blasting the tail.
The Astronomer Group: The people who are not part of the sun-comet demonstration still have a critical role. They are not just watching other people play the game, but they are tracking the shape of the cometâs tail as it passes around the sun, as observers on Earth. Depending on their perspective at each point in the cometâs orbit, the tail will appear longer or shorter. For example, if the comet is roughly between Earth and the Sun, the tail may look short, because it is stretched towards us. If you have time for writing, ask the Observers to sketch the comet as they see it. (See the handout.) In an average class, each student will get to observe the comet at least twice, which is very helpful for catching the unexpected views.
When every group has had a chance to play every role, take a few minutes to review one more time. As a comet is orbiting around the sun, which way does its tail point? By now, everyone should be willing to state that the tail always points away from the sun.
Still, you may still have a few hold-outs who are not quite sure this can be true. If you are lucky and itâs a sunny day, you have a hole card to play. Invite the students to each imagine that they are comets. âGuess what? You can see exactly where your tail would be. Who can point at it? Whereâs your tail, Comet Human?â
If you are not saved by the insight of a student whoâs totally absorbed the lesson, it is OK to resort to hints. âEveryone has one. Itâs easy to see. Yes, you can see your comet tail! Where is it? Which way does a cometâs tail point? Right: away from the sun. Whereâs the sun right now? What do you have thatâs pointing away from the sun? Itâs not bright and shiny like a cometâs tail. Itâs dark, because there are no sunbeams there.
âYes! Your shadow is your comet tail. It points away from the sun, always, no matter what direction you run.â
Stage 3: The Reward
Finally, everyone needs a model comet of their own to take home and show off and share with family members everything about how comet tails work. This is not an art project; itâs an opportunity to review and experiment individually. If some students are fussy about carefully arranging their streamers to make a colorful pattern, that is all right, but the point is to assemble a working model.
Each participant needs 24 feet of curling ribbon and a birdie (remember what I told you earlier about calling it by its proper nameâbe prepared for lots of giggling and teasing if you insist on that) . Cut the ribbon into eight lengths of roughly 3 feet. It is perfectly all rightâand in fact more realisticâif the streamers come out various lengths. And depending on the studentsâ social skills, it is also all right for them to exchange colors once the cutting is done. (There are always some who prefer to discover a multi-color comet and others who prefer monotone.)
Once each student has six streamers, have them tie one end of each streamer to the head of the birdie.
Detail–Attaching Ribbon For Comet Tail
Your meticulous planners will distribute them evenly around the netting; others will be clumped randomly. Either is fine. Every comet is unique and most are quite non-uniform.
Be real. This project is not done when it the comets have been only built. Everyone needs a chance to try them out. They will, of course, want to toss them around the classroom; if this is not acceptable, make some provision for them to try out that technique outdoors. More scientific, of course, as time permits, is to allow the participants to take turns trying out their comets in the pretend âsolar windâ of the classroom fan. As long as they willing and able to mind safety rules about working around a fan, by all means have everyone try out the tail position approaching, passing, and retreating from the Fan Sun. But donât get all hot under the collar if other comets are flying through the room while you monitor the fan users. Just imagine youâre in the Oort Cloud and youâll be OK.
Up next:Â Supplies You Need and Resources You Can Use
A Cluster of Comets, Incoming & Outbound
