Origins Part I

Teacher Pa's class as been studying various religions, including their
creation stories, this week, so she asked me to review the scientific
"creation story" with the kids.  She had made a big poster with
Hinduism, Judaism, Christianity, and Islam as column headings, each
with entries in rows titled [Name of] God, [Sacred] Book, Creation
Story, Golden Rule, What Happens After Death, and Holidays, and she
wanted me to fill in a Science column for Creation Story, Golden Rule,
and What Happens After Death.

I wanted to make very, VERY clear to the kids that science is not
another religion, so I refused to tell a "creation story" and instead
made a detective story about our origins.  (It turns out I was
justified: even after spending the whole morning with the kids and
emphasizing how science works, as the kids went to lunch I began
ripping the Science column off the religion poster and my own son
Linus said, "Dad, what holidays does science celebrate?")

I started the morning by discussing what kinds of questions science
can answer and what kinds of questions it can't.  If you're about to
bite into your last cookie and someone asks you to share it, can
science help you figure out if you should share it?  No.  If your best
friend moves away and you're lonely, can science help you figure out
what to do?  No.  Religion might help you with those questions.  But
if you have a question about nature, such as "When did the Earth
begin?", then science can help.  I think it's super-important to help
kids draw these distinctions.  Because religion tries to say something
about our origins, and so does science, it's tempting to make
parallels between them.  But the differences are more important then
the superficial parallels, and we need to help kids see that.  Science
and religion are simply about different things.  If we had a poster
comparing different sports, we wouldn't put Sudoku on it!

The kids had done a timeline of the history of Davis, so I started
with a blank timeline with "Now" on the right and "?" on the left.  I
put a few recent events (the years they were born) close to "Now" and
asked how we could know about the distant past using evidence (clues).
Because they had recently been to Yosemite and seen a slice of a tree
with about 1,000 rings, I started with that: we know that trees grow
one ring each year, so this tree tells us that Earth is at least 1,000
years old.  In fact, the oldest trees in the world live in California
and they are over 4,000 years old, so I marked that too.  (Aside: by
matching long-dead trees with just-felled trees [using ring thickness
as an indicator of how good for growth each year was], scientists have
been able to put together tree-ring histories going back about 10,000
years!)

Next, we moved on to rocks. They had studied some geology in
preparation for Yosemite, so we reviewed how long it takes millions of
years for a river to carve a canyon, based on how fast we observe it
carving today.  So Earth is at least millions of years old.  One kid
knew that some rocks are at least 1,000,000,000 (one billion...I wrote
out the number to impress them) years old.  But how, I asked.
"Dating."  OK, but how do we do that?  I did a very simplified version
of radioisotope dating.  I took some dominoes and stood them up on a
desk.  Standing up, they have some potential energy, because they have
the potential to fall.  Once fallen, they don't have potential energy.
(We had talked a bit about this concept previously.)  Now some atoms
in your bones (or in rocks) have this extra potential energy, but as
time goes on more and more of them lose this.  I knocked down a few to
illustrate the passage of some time, then a few more to illustrate the
passage of more time, etc.  They quickly got the idea of "more down
equals older" (I gave them many scenarios and they got the relative
ages right) but I'm not sure what they were really visualizing when we
said "more energy" or "fall down" because I got questions about
whether the atoms are dead or had changed into something else.  A nice
thing about these dominoes was that they came in different colors, so
it was easy to point out that this domino is still a red domino with 5
and 2 dots, it's just that it doesn't have extra energy now.  So I
think the got the idea that we were using small particles in the rocks
as a clock, but not much else.  Which is probably ok; you can't do
everything.  (If I had planned this whole semester better I probably
would have brought in a microscope very early on, and established the
concept of atoms so that I could safely refer to it throughout the
semester...last year all the kids in the school studied atoms but only
one of those kids is in this room this year.)

So I extended the timeline all the way across the other (very long)
whiteboard and wrote 4,500,000,000 as the age of the oldest rocks on
Earth.  I then mentioned meteors, which they had heard of, and how
their slamming together would generate heat.  (I slammed clay lumps
together for visual effect.)  We think Earth was formed by meteors
slamming together and creating so much heat that they melted together.
The rock-dating clock starts when the rock solidifies, so the age of
the Earth is 4,500,000,000 years.  I then wanted to show them a movie
rendering of this process, and I showed the first few minutes of the
Birth of the Earth episode of How the Earth Was Made; in the first
several minutes they have some really nice visualizations of this.
But they like it so much that we kept watching, well into break time,
and almost finished.  But with about 10 minutes left in the 43-minute
episode, I really wanted them to stretch their legs so we encourage
them to go outside but left the option of continuing to watch. Half
the kids watched to the end.  I highly recommend this episode, and in
fact this whole series.  It emphasizes the use of evidence to test
ideas.

The kids had MANY questions in response to the video.  It was great to click Pause as soon as a question arose so I could deal with it right away.  I felt like the movie was an awesome way to keep their attention (which is sometimes a struggle), but I could still provide an interactive teaching environment.  It was the best of both worlds.




I have a lot more to say about what we did after break, but I'll make
that another post.  To be continued....