Time Machine

EVOLUTION

 SYNOPSIS

 PRINCIPAL CONCEPT

 ASSOCIATED CONCEPTS

1. Being surrounded by a familiar scale of time throughout the course will provide a constant and convenient frame of reference on which to place events in biological history, helping students to see and remember the existence and rate of biological change.

2. Students will be more likely to internalize the difficult concept of deep time if they use all their senses in a dramatic context, and if the time scale always surrounds them.

ASSESSABLE OBJECTIVES

Students will....

1. recognize the relative timing of major biological events in geological time.

2. recognize the proper orders of magnitude to those events ("billions of years", "millions of years", "thousands of years".

3. recall the approximate timing of a few selected key reference events, e.g. origin of earth (4.5 bya), oldest fossils (3.5 bya), beginning of Cambrian "explosion of life" (545 mya), largest extinction event (Permian/Triassic, ~90% of all species died out: 250 mya), age of dinosaurs (235 mya - 65 mya), the K-T extinction (~65% of all spp. died out: 65 mya ), earliest hominins (6 mya).

MATERIALS

PowerPoint Presentation (Optional): This could be used as an introduction to this lesson, or serve as a quick presentation of the concept in place of the lesson.

1. Create a Solar System time line in your classroom, in an appropriate scale to the room's perimeter, and clearly marked at least at the points listed here:

4.5 billion years ago (one edge of doorway entry into classroom: Earth and Moon fully formed) 4 billion years ago (life probably starting to form) 3.5 billion years ago (oldest fossils) 3 billion years ago 2 billion years ago (significant rise in oxygen, to ~2% level) 1 billion years ago (earliest fossil evidence of sexual reproduction: tetrad cells) 545 million years (beginning of Paleozoic and the Cambrian "explosion" of diversity) 250 million years (end of Permian extinction, beginning of Mesozoic) 65 million years (end of dinosaurs, beginning of Cenozoic) 6 million years (beginning of hominins) Now (at other edge of doorway)

- a. Measure the perimeter of your classroom. - b. Using that dimension to represent 4.5 billion years, and starting at the door into your classroom, place markers at intervals backwards in time matching the list above. A suitable scale can be found at the end of this lesson, or have your students calculate the scale dimensions for your room. To assure accuracy, have 3-4 students assigned to each dimension to calculate the scale independently; they can compare results and work out any errors. - c. If possible, have your students (or your more artistically talented ones) illustrate the past 545 million years with appropriate life forms of each era on a length of butcher paper, and mount it as a mural along the wall, from the doorway toward the back of the room. This, alone, will be a handy reference for you (and/or your students) to point out various events of the past when you talk or read about them throughout the year. If possible, get it laminated (or cover it with clear contact sheeting) for year-to-year durability.

2. Prepare an audio tape with the following:

- a. the fanfares from the first selection in the tape or record of the music from the motion picture sound track for 2001 - A Space Odyssey : "Also Sprach Zarathustra". There are 3 dramatic fanfares in about 1.5 minutes. You will probably need some filler time from when you turn on the tape to when you will make your grand entrance to one of those fanfares. The two bands following the "Zarathustra" (selections 2 and 3) would work fine...they're long and mildly spacey. Tape them first (for the duration of "filler" needed, then add the "fanfares". - b. some appropriate sound effects (from a sound effects tape or CD, or the selections 2 & 3 mentioned above); try "space" sounds, stormy winds, etc. These should serve first as the timed "filler" before the fanfares, then simply for background sounds during your "voyage" through time after the fanfares.

3. Gather your Time Pilot costume (use your wild imagination):

- a. helmet: I borrowed a black motorcycle helmet from a colleague of mine. - b. cape: Get some material from a yardage shop...something flashy (I chose red), and attach snaps, or an elastic band, so it goes on over your head quickly. - c. boots: I used my black after-ski boots...real spacey! - d. gloves: I used some cool black ski gloves with long gauntlets - e. laser blaster gun: get a toy "space" gun, which makes sounds, flashes lights I wear all black that day, with a black, long-sleeved turtle-neck pullover shirt. I wear my lab coat over that initially (easier to remove when putting on the costume).

4. Prepare your signs for the time machine:

- a. get some heavy poster board strips (about 15 cm X 60 cm long for most) - b. neatly, in large letters, with marker pen, print the word or words for each event, (see chart) - c. put the time of the event (bya or mya) on the sign. - d. there should be enough cards so that everyone in your largest class has a card to hold. - e. these should be placed around the periphery of the room, on counter tops, marker trays, et c.), in their proper position of the time line, face down.

5. Gather items representing the events:

- a. it can be very thrilling for a student to actually hold a very old rock or fossil, so try to get as many of these as you can, with the ages documented if possible (from catalog supply companies, or local university geologist). - b. where necessary, here and there, you can substitute fake items, or plastic replicas, or stuffed animals (e.g. dinosaurs). For ancient bacteria and algae, provide plastic petri dishes or culture tubes at some locations. - c. place the items around the room at their appropriate locations (somewhat hidden). - d. keep these items and signs in a special box to be used every year.

 TIME

 TEACHING STRATEGY

1. This trip is best done early in the course, perhaps in conjunction with your introduction to evolution, or your intro to ideas on the origin of life. This will provide a memorable and constant frame of reference for all subsequent lessons, discussions, films, and news events which have a geological time element. Throughout the course, you (or a student) can refer to the appropriate part of the time line when dealing with these events.

2. This dramatized "trip" may seem a little hokey, or childish for high schoolers, but it has worked very well with Juniors and Seniors. Success will hinge largely on your attitude and rapport with your students. You can always adjust your approach, so it could work well with elementary through junior college.

3. In conjunction with this, you might want to explore the methods for measuring these vast time periods, especially if you have students who might question the validity of our ability to measure geologic time (and you probably will!). A quick way is to do the mini lesson "13 Ways to Tell Time Backwards"; the strength of this is that it provides multiple lines of evidence pointing to the same time dimensions. Or consider doing the new DEEP TIME lesson, and/or one of the additonal suggestions listed under "Extensions and Variations" below.

Click here for an animated PowerPoint presentation that nicely compares cosmic and biological evolution with special creation timelines, This link will take you to the script for the PPP and how to request the PPP itself.

PROCEDURES

1. Students are prepared for a voyage backward in time...back to the formation of planet Earth. They must have "trip slips" signed by parents. Collect these a day or two before the "voyage". Anticipation grows!

2. On the day of the "voyage", the room is darkened (curtains closed, lights off), and students are told that "I have arranged for my brother, "Flash Flammer" [make up a name], an experienced Time Pilot, to serve as your leader of this expedition so far back in time. Flash is in my back room, preparing for the voyage, and I'll have to go get him." Students are asked to wait patiently for a few moments while you do this. [You start the tape player going, with spacey sounds, and go directly into your back room, where you quickly don your helmet, cape, gloves, and ray gun. You leave via a back door (passing through the adjacent classroom, startling everyone), go to your classroom's outer door, listening for the next fanfare from "2001 - A Space Odyssey", carefully timed to begin about this time on your tape. [If you don't have a back room, or back door, set up a screen for your costume change, and improvise your own version of a dramatic entrance.]

If you like, you can explain at some point that the curtains must be closed because "our time machine causes everything outside to spin, and this could make you dizzy if you could see outside."

3. With the next fanfare, you throw open the door dramatically, step in, shouting "Aha!!! Are you ready?....It's TIME ...for the voyage of your life!!!" Rev up the engine (a child's pretend bicycle engine, or appropriate sound effects). Explain to students that they will need to get "spaced out"...they do this by standing and walking out of each row, starting at the back, and walking back and around the perimeter of the room, with each row falling into the growing line, until everyone is standing around the edge of the room. You should lead the line, using your trusty "laser blaster" to deal with dangerous dinosaurs, terrible trilobites, belligerent brachiopods, attacking algae, and bad bacteria! When all students are standing around the room perimeter, facing into the room, move back around and gently re-position students so that they occupy positions pre-selected where they can hold a sign and/or object representing that point in time (which you placed there before class).

If you need (or want) to cut across the room, pretend that you are passing through a "worm-hole in the space-time continuum", while you move across in staggering thrusts and bumps along the way.

4. Once positioned, announce that you will step outside for a moment "to set some switches". Do this, then immediately throw open the door, with loud booming noises, flash the room lights off and on quickly (lightning), shake a large sheet of posterboard or sheet metal (thunder), and announce "It's four and a half billion years ago...the earth is forming!" Hand off these two jobs to two students standing there, while you move on to the next station, handing "hot" volcanic rocks to a student ("tsssss"). At the 3.8 billion years station, hand the student a piece of 3.8 billion year old rock, exclaiming "One of the oldest known rocks on earth....3.8 billion years old!" At a station between 3.8 and 3.5 billion years, pick up a hidden box of "Life" cereal, hand it to the student there, announcing "The first living thing!". "We know this, because the oldest fossils found are about 3.5 billion years old" (handing a piece of chert to that student, pointing to the student, saying "The oldest fossil!!!"). At 2.7 billion years, announce "You've got a nucleus!... you must be the first eukaryote!"

5. Other highlights will be:
a. the first significant rise in atmospheric oxygen (about 2 billion years ago,
to the 2% level), you could have an oxygen molecule model here.
b. the first sign of sexual reproduction ("...the beginning of SEX!" [in the form of 1 billion year old fossils of cell tetrads, suggesting meiosis])
c. the pre-cambrian appearance of multicellular organisms (algae and wormy
animals, 600 mya to 545 mya)
d. the cambrian "explosion" of diversity of invertebrates (545 mya)
e. the first fishes (~500 mya)
f. the first amphibians (~360 mya)
g. the first reptiles (~300 mya)
h. the first mammal-like reptiles, e.g. dimetrodon (~250 mya)
i. the first mammals (220 mya)
j. the first birds (210 mya)
k. the first flowering plants (about 130 mya)
l. the last dinosaurs go extinct (actually, 40% of all genera went extinct)
(65 mya)
m. the explosion of mammal diversity in the Cenozoic (65 mya)
n. the earliest whales (about 50 mya)
o. the earliest apes (30 mya)
p. the earliest hominins (6 mya)

Along the way, be sure to point out (dramatically):
q. the greatest mass extinction (end of Permian, 250 mya; 60% of all genera, went extinct, perhaps 90% of all species.)
r. the beginning of the separation of North and South America from Europe and Africa about 2 mya (beginning of Jurassic period)
s. the "age of dinosaurs" (250 - 65 mya)
t. the last "ice ages" which covered much of North America (less than 1
mya)

In order to have something for every student to hold, prepare several stations for the long 3.5 bya to 2 bya, time frame, with signs saying "BACTERIA" , "ALGAE", "MORE BACTERIA", "MORE ALGAE", "UGLY ALGAE", "BEAUTIFUL BACTERIA", etc., along with appropriate rocks, culture tubes, fake "slime", and/or petri dishes.

6. Continue thus around the room until you arrive at "NOW". At this point turn up the lights, have each student pick up his/her sign identifying the event or material at that point, hold the signs so all can see them, and ask everyone to look around the room for a few minutes, noticing the timing and sequence of the events. Then, ask students to place the signs at their positions so that they can be seen when they leave. Students must then walk forward through time, (counterclockwise in my room), going past all those events, and eventually moving into their row to sit down. They then begin to fill in their "time map" diagram, placing the events asked for at the proper position in time, according to the signs in the room. Meanwhile, you return to the back room, remove costume, and return to the class, asking if they found the trip exciting, etc.

7. If there is time, it's interesting to show them a series of slides, or the video entitled "Powers of Ten", moving from the familiar to the far reaches of outer space, moving out exponentially, then back down to the familiar, and deep into the microscopic and sub-microscopic reaches of inner space. This adds further to dramatize the vast ranges of time, size, and space. You might close with a little homily that, "Even though each of us is just a little speck in the universe, in time and space, we ARE special: we ARE made of stardust...the remains of a supernova, we ARE ALIVE!, we CAN DO amazing things, ...and we ARE ALL IMPORTANT, certainly to ourselves, and to those who care about us. Isn't that amazing?!"

There are also a few animated "Powers of Ten" sequences online. Try these:
The Universe Within
A Question of Scale
Powers of Ten
Eames Office Powers of Ten

8. Another version of some closing comments: "For such a tiny speck of material (in this vast universe), existing but an instant in the vastness of time, we (and all life) are very precious...very important, to each other. If you are having problems, trouble, sadness, anger in your life, just stand back and reflect on your place in this universe, and perhaps those problems will not seem so overwhelming!!! In addition, even little things we do can have a profound effect on others, so DO GOOD THINGS!"

ASSESSMENT

EXTENSIONS

& VARIATIONS

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1. As mentioned in the Teaching Strategy section, it would be useful to explore some of the ways scientists actually determine the ages of geological events and fossils. Using "13 Ways to Tell Time Backwards" is a good opener. In addition, it would probably be helpful if you could include a lesson dealing with radiometric age-dating (e.g. C-14 and Potassium-Argon), the principles and procedures involved, especially if students have not explored this topic in earlier courses. We have a new lesson (2004) that provides a very nice experience in a rock-dating simulation. It's called Date-a-Rock!. Try it. There is also an excellent online interactive dating tutorial on radioactive dating, C-14 dating, and using isochrons for nearly fool-proof dating. You should also consult the Talk Origins Archive essay on Radiometric Dating for information. In addition, the University of California Museum of Paleontology web site "Learning from the Fossil Record" features a nice age-dating lesson: "Determining Age of Rocks and Fossils" by Frank McKinney.

2. Seriously consider spending a session with the new interactive lesson on the ENSI site: DEEP TIME, in which the methods and high level of confidence held by scientists in geological age dating is experienced. This lesson is designed to be a useful introduction to the Virtual Age Dating Tutorial described above. It also points to the pseudoscience of those predisposed to discredit the science of modern geochronology in favor of "evidence" for a young Earth.

3. To help students gain a more realistic personal sense of deep time (especially in middle school life science or earth science), try our Patterns in Time lesson. In that lesson, students also come to realize that the different vertabrate classes emerged separately over several 100s of millions of years, and did not exist prior to their emergence (as revealed in the fossil record). That lesson also demonstrates the accumulation of modified traits on top of the accumulated traits found in the previously emerged group, showing gradual, additive and mosaic changes over time. All of this provides a strong implication that each group descended from the earlier antecedents through gradual change over time.

4. We also have an excellent lab experience in our Varve Dating lesson. In this activity, students actually count the annual varves in small pieces of the Green River shale formation, then extrapolate that count to the actual duration for the body of water in which those sediments were deposited (a few million years!)

5. There are many versions of student-constructed or class-constructed time line lessons. Most are not as dramatic as the "Time Machine" lesson described here, but they could be useful for students to do in addition to "going back in time". An excellent timeline lesson is available, with vivid illustrations, from the efforts of ENSI fellow and OBTA winner, Thomas Atkins and one of his students. It's entitled: "The History of Everything".

6. For students with little or no experience in dealing with time sequences, there is an excellent exercise on the UCMP web site ("Sequencing Time" by Judy Scotchmoor) which takes the students from sequencing the events in their own lives, to assigning numerical values for those events (years ago), then giving names to the groups of related events (e.g. "Pre-Schoolian Era", etc.). From here, it's an easy jump to working with geological time charts.
In addition, a followup lesson ("What Came First?", also by Judy Scotchmoor) physically engages students in building a room-scale timeline. This lesson could be even more impressive and effective than the Time Machine lesson: it's very physical, but it's easier to do and prepare for. The timeline is already provided (mounted around the room). You ask students to pick one of about 15-20 large event cards (this requires about half of your class). Then ask them to arrange themselves in the sequence they think the events happened (not along the timeline, yet). Lots of shuffling and reshuffling! Then, ask the seated students to suggest any changes they think should be made (can vote, if necessary). When they are all more or less satisfied, read your list of the events in proper sequence, asking students to move accordingly, as you go. Quite an eye-opener.
Next, when all properly sequenced, ask them to move to the time line around the room, and take up positions where they think they should be. When "done", again ask for input by those in seats. Finally, have students move to where they should be, as necessary. Another eye-opener, depending on whether they have done any timeline work before. Most will be jammed into the very short past 500 million years. You can find this lesson (with list of events) on the UCMP site.

 OTHER RESOURCES

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1. A beautiful timeline poster is available: "A Correlated History of Earth". It is not a scaled timeline, but it correlates a variety of events in geological and biological history. It shows stages of plate tectonics, mountain building, volcanic episodes, glacial epochs, asteroid and comet impacts, fossil group ranges from many different localities, and major extinctions. It can be seen and ordered from the Worldwide Museum of Natural History for $20 (laminated for $25), including shipping. You can also order by phone at 1-800-216-8130.

2. TalkOrigins Archive has a very nice listing of events (with their times) in their "Evolutionary and Geological Timelines". They also have a short discussion of why the times seem to change, and why they may be different in different references: "Geological Time Scale".

3. An excellent source for the latest geological time scale charts is:
The International Commission on Stratigraphy: http://www.stratigraphy.org/
Also, (same site): Time Scale Chart and Timescale comparison charts (to scale - 1937-2004) - These are useful to show changes in the Time Scale Charts over the past 50 years..

 ATTRIBUTION

Some of the ideas in this lesson may have been adapted from earlier, unacknowledged sources without our knowledge. If the reader believes this to be the case, please let us know, and appropriate corrections will be made. Thanks.

1. Original Source: Larry Flammer (1970)

2. Reviewed by J. Beard, C. Nelson, M. Nickels, 12/15/97

3. Edited / Revised for website by L. Flammer 4/2008