Middle and High School … from a Montessori Point of View
Water is necessary for life as we know it, which is why the search for life on other planets and moons in the solar system has been focused first of all on finding water. NASA now reports signs of water on Mars. Salty water perhaps, and even now there is no direct evidence that it is water and not some other fluid, but this is the first evidence of there being liquid water on Mars today.
The video above explains, and the BBC has a good article.
We could have been talking about the nuclear meltdowns in Japan, but I’m not sure. Our conversations tend to wander. I remember trying to explain where the carbon atoms, that are so essential for life, came from. It’s been a while since we saw this topic, so I figured it wouldn’t hurt to go it over again. And then I found this wonderful image of the Tycho supernova from the Chandra space telescope. Supernovas are where the heaviest atoms are formed.
In the beginning … the big bang created just the smallest elements, hydrogen and helium. But even these tiny things have gravity, so they pull each other together until there’s so much stuff that the pressure at the center of the clump is enough to fuse hydrogen atoms together.
Now fusion is easy to confuse with chemical bonding that occurs around us every day. After all, the hydrogen in the atmosphere is usually in the form of H2, which is two hydrogen atoms bonding together by shared electrons.
With fusion, on the other hand, the single protons that make up the nuclei of the hydrogen atoms are pushed together to create a bigger atom, helium. I say pushed together, because it takes a lot of pressure to fuse atomic nuclei. And it also releases a lot of energy. Notice all that heat and radiation that comes from the Sun? All that energy was created by the fusion of hydrogen atoms; the smallest element, hydrogen, fuels the stars.
The huge amounts of energy released by fusion makes fusion power one of the holy grails of nuclear energy research. If we were able to create and control self-sustaining fusion reactions, just like what happens in the Sun, we would have a source of tremendous energy. There is a lot of research in this area. Some people have figured out how to build fusion reactors in their basements, but these use a lot more energy than they produce so they’re not very useful as a power plant (Barth, 2010). The ITER reactor, currently being built in France, aims to be the first to produce more electricity than it uses.
Now back to the stars. Hydrogen atoms fuse to form helium, but it takes a lot more pressure to create larger atoms: carbon has six protons, nitrogen seven, and oxygen eight. These elements are essential for life (as we know it). The only time stellar forces are great enough to produce these are when stars explode; an exploding star is said to have gone nova. Bigger atoms, like iron (26 protons), gold (79 protons), and uranium (92 protons) need even greater forces, forces that only occur when the largest stars go supernova.
So if these elements are only produced in novae and supernovae, how did they get to Earth? How did they get into your DNA?
Well when stars explode, a lot of these newly formed elements are blasted off into space. It’s a sort of cosmic dust. We could even call it stardust. It’s matter, just like the hydrogen and helium from the big bang, only bigger, which means they have more mass, which means they have more gravity.
The gravity pulls the stardust together with the hydrogen and helium sill floating around in space (there’s a lot of it), to form new stars, and, now that there are the larger elements to create them, rocks, asteroids, and planets.
So, if you think about it, some stars needed to have been formed, lived their lives (which consists of fusing hydrogen atoms until they run out), and exploded to create the matter that makes up the planets in our solar system and the calcium in our bones, the sodium in our blood, and the carbon in our DNA.
1. Lots of information about Tycho’s Star on SolStation.com.
This nighttime photograph of the Nile River and its delta from the International Space Station beautifully illustrate the importance of water for life and civilization. The city of Cairo is at the neck of the delta; the brighter spot where the distributaries diverge.
Spaceflight Now has other really cool photos. Bad Astronomy has an interesting post on the logistics of this particular photo, while Heather Pringle has a very interesting post on how the desert may have aided the ancient Egyptian’s civilization.
Discover Magazine has a great article summarizing the evidence for life on Mars. It’s long because it goes into a lot of detail examines quite a variety of possibilities, but it ties quite nicely in with the questions we are asking about what is life and where it can be found.
The article also mentions a study titled, “The Limits of Organic Life in Planetary Systems” produced by the National Research Council for NASA. It can be found for free online, with an associated podcast that much more accessible to middle schoolers. The report is extremely open to the possibility that extra-terrestrial life exists, and could exist even without water and might even be silicon based.
One of the major motivations space exploration is the search for extra-terrestrial life. The SETI project is the most visible initiative and there are a lot of neat educational resources on their outreach page. And you can participate. seti@home allows you to download a screensaver that actually helps them process data.
The NPR program, To the Best of Our Knowledge, has a nice program asking the question, “What is Life?” The last part of the program (at about 45:00 minutes in) is an interview with Paul Davies who is head of the SETI post-detection task group. It starts with question of silicon based life, the theory of which is based on the locations of carbon and silicon in the same column in the periodic table. It also talks about what life might look like once technology really takes off and life starts “evolving by design”.
But SETI searches for signs of intelligent life using radiotelescopes. There are other projects that look for any sign of live. One of the major reasons the Mars rovers and satellites spend a lot of time looking for signs of water on the planet is that life, as we know it, requires water.
It’s also why space agencies are so interest in Europa, the moon of Jupiter that’s covered with ice. Europa also has signs of volcanic activity under the ice, which makes it doubly interesting.
90% of the cells in your body are bacteria and other provocative facts about the Domain Bacteria are the subject of a great but long article by Valarie Brown.
[R]esearchers have also discovered unique populations adapted to the inside of the elbow and the back of the knee. Even the left and right hands have their own distinct biota, and the microbiomes of men and women differ. The import of this distribution of microorganisms is unclear, but its existence reinforces the notion that humans should start thinking of themselves as ecosystems, rather than discrete individuals.
—Brown (2010), in Miller-McCune.
The article makes for great reading during this cycle’s work on classification systems and evolution. One choice paragraph summarizes the fundamental differences between the domains of life:
There’s such ferment afoot in microbiology today that even the classification of the primary domains of life and the relationships among those domains are subjects of disagreement. For the purposes of this article, we’ll focus on the fundamental difference between two major types of life-forms: those that have a cell wall but few or no internal subdivisions, and those that possess cells containing a nucleus, mitochondria, chloroplasts and other smaller substructures, or organelles. The former life-forms — often termed prokaryotes — include bacteria and the most ancient of Earth’s life-forms, the archaea. (Until the 1970s, archaea and bacteria were classed together, but the chemistry of archaean cell walls and other features are quite different from bacteria, enabling them to live in extreme environments such as Yellowstone’s mud pots and hyperacidic mine tailings.) Everything but archaea and bacteria, from plants and animals to fungi and malaria parasites, is classified as a eukaryote.
—Brown (2010).
Brown also gets into a discussion of if bacteria think:
[B]acteria that have antibiotic-resistance genes advertise the fact, attracting other bacteria shopping for those genes; the latter then emit pheromones to signal their willingness to close the deal. These phenomena, Herbert Levine’s group argues, reveal a capacity for language long considered unique to humans.
—Brown (2010).
Trimming this article down would probably make it a good source reading for a Socratic Dialogue.
Bacteria are the sine qua non for life, and the architects of the complexity humans claim for a throne. The grand story of human exceptionalism — the idea that humans are separate from and superior to everything else in the biosphere — has taken a terminal blow from the new knowledge about bacteria. Whether humanity decides to sanctify them in some way or merely admire them and learn what they’re really doing, there’s no going back.
—Brown (2010).
The Toilet Paper Timeline of Earth History worked as well as I’d hoped. The beginning was a bit boring, it was a challenge keeping the kids focused, since nothing much happens for a very long time. It helped that we had to unroll the toilet paper back and forth across the room, so I had a different student take over every time we had to turn around.
That was not quite enough though to keep them from getting distracted, however, so I also assigned people to stand at the location of major events. This worked out nicely in the end because it let me ask them, at the end, whose event was the most important? Most of them made some argument without any prompting; the group is already pretty comfortable with each other and are not afraid of speaking up.
During the unrolling, most events occur in the final two turns. Students did notice this fact, which is the ultimate point of the exercise. Getting them to talk about different events, like the time of the first multicellular organisms or the extinction of the dinosaurs, helped students own the work. All together, it seemed to strike their imaginations.
They also seem to like using Cartoon History of the Universe as their reading assignment.
Jennifer Wenner has posted a beautiful demonstration of geologic time using toilet paper for the timeline at SERC. You’ll need a 1000 sheet roll and by the time you’re done there will be toilet paper everywhere.
This is a great demonstration because as you unroll the toilet paper you get a great feel for the long spans of time in the preCambrian when nothing much happens, and then, as you approach the present, events occur faster and faster. There’s 300 million years between the formation of the Moon and the formation of the Earth’s atmosphere. That’s 60 sheets! while modern man only turns up about 10,000 years ago, which is 0.002 sheets; about the width of the line drawn by a pen. Even the dinosaurs went extinct only 14 sheets from the end.
The SERC webpage has a spreadsheet with most of the important dates marked and translated into toilet paper units. The Worsley school in Canada has some nice pictures of the toilet paper being rolled out all the way down the hall.
