Here’s today’s science classroom activity. We’re surrounded by the crushing weight of layers of atmosphere above us, but we don’t feel it. Why? Our perception is tuned to differences, not absolutes. If we were in a completely pink world, we would notice anything that wasn’t pink, but (I’m pretty sure) after a few minutes, we would become blind to pink itself, just like you don’t hear the noise of a fan in the room until it stops.
Similarly (though through different mechanisms), we’re not constantly aware of the intense pressure pushing in on our bodies. (Would we really turn into mush in a vacuum? No… read more about the effects of a vacuum on the human body here). Thank goodness, because it’s quite startling. I know, because I’ve felt it, in this wonderful science classroom experiment.
All you need is a big trash bag and an industrial strength vacuum cleaner, and a willing victim (er, “faithful subject of science.”) The victim (aka “subject) gets inside the bag, and once you suck all the air out of the bag with the vacuum cleaner, they’ll feel an intense pressure. SAFETY FIRST! Read this PDF writeup of the activity (from the Exploratorium’s Eric Muller) for all the ins-and-outs and safety factors in doing this with your kids. (Words to the wise — don’t put your head inside the bag!) It’s stunning — try it if you can.
Best skin-tight prom dress. Courtesy of Eric Muller – http://www.exo.net/~emuller
Why do we feel this pressure? Stop and think about it a moment. What changed when we sucked the air out of the bag? There’s the same atmospheric pressure outside the bag (14.7 PSI at sea level), that didn’t change, there’s still the weight of the atmosphere pressing down on you. What changed is the pressure inside the bag. What does that have to do with anything?
The high pressure outside the bag pushes the bag’s surface against your body, and the bag stretches against your skin. We feel this stretching of the bag as it pushes on our skin and the little hairs on our body. We don’t feel the pressure without the bag, because though the air pushes against our skin, it pushes the same in all directions. The bag lets us feel what is already there — the weight of the air!
You can extend this activity a bit by measuring the pressure inside the bag (at the Exploratorium it was 1 PSI). Eric says:
Paul Doherty and I used a barometer watch to measure the pressure inside the bag when doing research on this activity. Some one that goes to the mountains a lot might be able to loan you one or you can buy one. You can also just get a barometer. I found a bunch for sale on eBay. Lastly, you can make a home-made barometer. If you do a Google search, there are a variety of easy to make barometer designs (but you still might need a good barometer to calibrate your homemade one)
Paul D. has a similar activity to let you feel the pressure in water with a plastic bag. Stick your hand in a pail of water. You don’t feel any pressure. But stick your hand in a plastic bag and stick it in the water, and you’ll feel an intense pressure (that gets stronger with depth) as you put your hand in the bag. Paul D. explains:
Why do you need the glove or the bag?
Human sensors detect differences or changes in a signal. When you stick your ungloved hand into the water the water exerts a uniform force on your hand. It flows around every hair and every wrinkle in your skin. Now a single hair is bent to the side. When this happens you cannot feel the pressure exerted by the water.
However when you wear the bag or the glove they will bend down the hairs on your hand, and the glove and the bag may have folds that exert uneven forces on your skin. So that you can “feel” the force exerted by the water.
Cocktail Party Physics has a great old post on the history of measuring pressure (fascinating stuff, really). And Eric has more activities here.
One of Paul Hewitt’s favorite demos to show that suction cups stick because of the air pressure pushing (rather than a “sucking force”) is this atmospheric pressure mat. You can lift a whole lab stool once you stick this down on it. A similar but smaller version is these atmospheric pressure cups.
A vacuum chamber/pump will let you reduce the pressure on anything (they suggest marshmallows), explore gas laws, etc. See the website for some example class activities. They also have a class set.
They’ve also got a durable hand-held vacuum pump for expelling air from any other kind of container. (Good for the “coin and feather fall at same rate in vacuum” kind of demo).
I am a science education and communications consultant -- view my website for my full range of services.
My friend and fellow science writer Jen Frazer has started a new blog (well, two actually, but let’s start with the first). I don’t know how she can spend a whole day at work writing copy, and then come home and spin out gorgeous and witty prose, but, hey, she didn’t win the AAAS Science Journalism Award for nothing! In the Artful Amoeba she explores charismatic microfauna, or the “weird wonderfulness of life on Earth.” By way of explanation, she says:
I say: it’s not the taxonomy that’s important. It’s the learning about the diversity of life on Earth. We don’t have to go to Mars to find living wonders, and though I respect those that want to, I wish the 100% real living organisms on Earth could get half the attention the putative creatures on a planet millions of miles away do. The curiosity cabinet is long gone, but the curiosities are still here, just waiting for us. All 10,000 ferns. All 70,000 known fungi. All untold millions of species on Earth. I want to show you. I’m passionate about this stuff, and I like to make it fun. Please join me.
Her other blog is Home Cooking Well - A blog about how your kitchen can enrich your life, your wallet, and your sense of humor.
As a teaser, here’s one of her recent posts on Moss That Swings Both (all?) Ways
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I’m sometimes greatly amused by the quality of press release science writing that is taking the place of professional science writing these days, since no one will pay for us to do it full time anymore (Science Daily, a major source of internet science news, is made almost entirely of press releases reprinted verbatim. And you’ll notice that this very blog is, so far, gratis).
At first glance, mosses and human beings have little in common.
Gee, ya think? I’m imagining myself at a coffee shop holding a cup of steaming tea and sitting across the table from a noticeably uncomfortable bryophyte.
Cough. *blink*
Me: So, read anything interesting lately?
Moss: No.
See? Not much in common. Strangely, this doesn’t differ greatly from most of my actual dates.
I don’t want to seem too hard on the author here, since 1. the release was probably first written in German, and 2. this is actually one of the clearer and more helpful press releases I’ve read. In any case . . .
Scientists from ETH Zurich and the University of Freiburg im Breisgau report that they were able to insert DNA from humans and bacteria into the moss Physcomitrella patens (sounds suspiciously close to “patent”) and the moss was able to manufacture human proteins without any further help. Yes, they basically cut and paste. And the moss said: OK! Cool!
The protonema of Physcomitrella patens. When the spore of this moss lands on a suitable spot, it starts growing into filaments like these. Given enough time, these little filaments will grow into a full-grown moss plant. You can see the chloroplasts, or light harvesting equipment, as little green circles.
For those of you unfamiliar with the Way of the Cell, DNA makes RNA (with the help of proteins called RNA polymerases), and RNA makes proteins (with the help of cell organelles called ribosomes). The reason this moss-cular feat is astounding is that doing the same thing with flowering plants will get you nada. The mammalian gene start and end sequences have evolved themselves right out of business when placed in a similarly much-modified flowering plant. Not that there’s much of a reason that that would *ever* happen in nature. Now in an evil mad plant scientist laboratory, on the other hand . . . Belgians + petunias = Brussels sprouts. Mwa ha ha ha ha ha . . . . .
How is it mosses can do what so-called “higher” plants cannot? It’s a mistake to think of mosses as “primitive” in the sense of “inferior”. Both mosses and flowering plants have ancestors that were alive at the same time. What mosses are is “less-derived”, in biologist-speak. The lineage that gave us mosses just didn’t change as much over time as the lineage that produced flowering plants, because they found they were well-adapted as-is to their particular niche (forests, rocks, sidewalk cracks, and the sets of “Lord of the Rings” adaptations). Like sharks, they found a sweet gig and they stuck with it.
According to Ralf Reski, botanist and co-author of the paper announcing this discovery, as part of this cozying into a niche relatively early on for multicellular life (moss seem to have sprouted out of the ocean and then pretty much called it a day) mosses have stayed genetic generalists. And this easy-going gene-set enables them to translate a wide range of DNA. In fact, hold on to your hats . . .
This cross-kingdom conservation of mammalian and moss protein production machineries is phylogenetically profound, and has several implications for basic and applied research. Comparative genomics, as well as functional studies, have recently established major differences in metabolic pathways and gene function between flowering plants and P. patens, and have suggested that a substantial moss gene pool is more closely related to mammals than to flowering plants (Frank et al., 2007; Rensing et al., 2008).
In the next post, we’ll take a look at what on Earth possessed these scientists to stuff human genes into a soft, green, cushiony object and at why biology is WAY cooler than nuclear physics. Stay tuned.
This is the last in a series of four posts about using clickers in upper division physics courses.
We’ve conducted extensive research on what students think about clickers, in introductory and upper division physics (email me if you want links to our papers). The survey of students who had used clickers in upper-division courses (across 11 courses, 224 responses) indicates that students prefer:
2-3 clicker questions per hour
Clicker questions be interspersed with lecture (not all at end or beginning)
Peer discussion be allowed and encouraged, and peer discussion be part of the response
Many prefer some time for individual thinking prior to the peer discussion
Clickers set students up to learn more from your lecture. Once they’ve struggled with the concept or idea, then when you do give your brilliant lecture, they’ll get a lot more out of it. To quote Dan Schwartz, there is a time for telling, it’s just not too soon. (more on this idea here and here).
Tips for Success
These aren’t that different from the tips at the lower division, but here they are:
Tell your students why you’re using clickers (to help them learn, not to track them)
Ask questions that are challenging (but not too hard)
Connect questions to lecture (so questions build on lecture or lead into lecture)
Create a comfortable environment for discussion
Don’t stress the grading of the clickers for the “right” answer
For a detailed instructor’s guide on the use of clickers, see our website.
Once again, here are a few very useful books on using clickers in the classroom:
Peer Instruction is the “bible” of clicker usage, including sample questions in physics. This text will change the way you teach! Derek Bruff’s new book Teaching with Classroom Response Systems comes highly recommended by Eric Mazur himself, which is high praise! Doug Duncan’s Clickers in the Classroom is a short and pithy gold standard of how to use Peer Instruction in the classroom.
I am a science education and communications consultant -- view my website for my full range of services.
I’m not actually committing to posting a physics toy every Tuesday, but I’ll start small.
One of my favorite places to watch people back at the Exploratorium was the colored shadows exhibit. This one’s always a winner.
Images from http://www.flickr.com/photos/soyunterrorista
This is an example of color addition. Remember this from grade school? I only remember it because I had to teach it. Color subtraction is what happens when you mix together pigments. Red pigment absorbs all light but red (which is reflected to your eye). Blue pigment absorbs all light but blue. So mix red and blue and you’ve subtracted all colors, getting black.
Light’s weird, though. You mix together all colors of light and you get white. The primary colors of light are red, green, and blue. You have receptors in your eyes for each of those colors. If your eye senses both red and green light at the same place, your brain says “cyan” (sort of blue-green). The really weird one is that red and green light together make yellow. So, that’s why the shadows are colored. The white light has all colors (R+G+B). If you block just one of the lights, (say, the blue one) then you get (R+G+B) minus (B) which equals (R+G), or yellow. Block the blue and the green lights and you get (R+G+B) minus (B) and minus (G), or Red. Block all three, and you get a normally colored black shadow.
Of course, even if your receptors get the same amount of light as someone standing next to you, your brain might interpret that color differently, so people will often disagree if something is orange or yellow, for example.
Arbor Scientific has a version (Color Addition Spotlights) of this that you can buy for your classroom or, hey, if you’ve got a dorm room and some extra cash, wow, this would be a really cool party trick. It’s actually not that expensive, considering. But if it’s too much for you, they’ve got a Spectrum Demo kit that teaches some of the same stuff using your overhead projector (better spectrum than a wimpy little prism demo).
You can make this on the cheap from the Exploratorium’s Science Snacks website (which also has a good explanation of the science behind it) and a more detailed lesson on Paul Doherty’s teacher institute page. And here’s a link to the Teacher’s Lab with some step by step science explanations, and how to use the science of light and color in the classroom. And Science Buddies gives some detailed inquiry lessons using colored shadows, and a video of students doing the activity.
I am a science education and communications consultant -- view my website for my full range of services.
This is part 3 of an ongoing set of posts about using clickers in upper division physics courses, as we’ve been doing at U. Colorado for several years.
Arguments against using clickers in upper division
We’ve heard plenty of arguments about why people don’t want to use clickers in the upper division. Here are a few (with our answers):
It chews up time. Yes, it’s true, it does. But these ideas are complex! And if students walk away with the few key ideas from class and really get them, then that’s a valuable use of class time.
Students are sophisticated learners at the junior level and don’t need this technological tool to help them learn. Yes, it’s true, they are sophisticated learners, and can go home and read the book if they don’t “get” the lecture. But we’re using clickers as a tool to aid their learning, and because they’re more sophisticated learners, they can get a lot more out of the use of that tool and peer discussion.
Discussion is easy in small classes, we don’t need clickers. Some instructors do use other methods, such as colored cards, in small classes. The technology itself may not be as crucial, but the teaching method (of asking a question and encouraging students to discuss it with their neighbors) is still incredibly powerful. Plus, students can still “hide” in a class of 10. Or even a class of five. And so can their misconceptions. Students may think that they are following, but until they have to answer a challenging question, they may not be aware of difficulties that they have.
Students may resist the use of clickers. That’s what happened in one class at CU, but the next semester, when clickers were used in that class, students saw the value they added.
It’s some extra effort for faculty. Yes, but we do have some question banks available for you at CU if you would like to try it.
Why use clickers?
Besides, clickers work. We have lots of data showing that peer discussion works — see for example the recent paper in Science by Michelle Smith et al. Below are some results from my own work in junior E&M I, when clickers were added to the course. That was only one of a set of changes, however, so it’s hard to tease out whether clickers were a major component, though it was certainly the one that students had the most contact with.
Our end of term surveys also show that students find the use of clickers useful and recommend them in upper division courses. See the powerpoint slides to see all that data.
One interesting piece of that story is that students in quantum mechanics, taught by a popular but traditional lecturer, didn’t want to see clickers added to the course. They said things like:
The class is small enough that if you don’t understand something you can ask the professor to clarify.
I feel that with clicker questions, the class would “feel” more like a lower division course.
The lecture style was extremely useful. NO CLICKERS!
The data reflected their concerns — they didn’t recommend that clickers be used in upper division courses. But the same instructor taught roughly the same course the next semester (different students, but same instructor and same course) with clickers. Those students were enthusiastic about the use of clickers, and strongly recommended using them in upper division courses. So, students may not be able to predict the value of clickers when they haven’t seen them used in an upper division course yet.
I am a science education and communications consultant -- view my website for my full range of services.
Wow, super cool. A group of schoolkids in Italy measured the distance from the earth to the moon using the delayed echo in the audio recording of Neil Armstrong’s famous “One small step…” speech.
They used the open source audio editing program Audacity to measure the echo’s delay which turned out to be 2.620 secs and used this to work out the distance to the moon as 3.93 x 10^8 metres.
That’s not bad given that the actual distance varies between 3.63 and 4.05 x10^8 metres.
Here’s the original Arxiv paper if you want to do it yourself, it has all the details. Tip o’ the lab coat to Swans on Tea.
I’ve also got some fun activities using Audacity and other sound programs to do some sound analysis, such as the difference between men’s and women’s voices, exploring harmonics in music, and the wonderful Escher staircase illusion of music. Here’s the handout (PDF). Here’s another version of that handout (PDF) using another free piece of software that is GREAT for elementary and middle school kids in particular, the TEEMSS Soundgrapher.
I am a science education and communications consultant -- view my website for my full range of services.
This is my second post in a series about using clickers in the upper division.
A lot of people have trouble imagining what kinds of questions you might ask at the upper division. The challenge is to make them tough, but not too tough. You want students to have to think and argue about them, but you don’t want to make them so hard that students are just stuck. Some example question types are:
conceptual
math/physics connection
application of ideas
step in calculation, proof or derivation
Here are some example questions from a few different courses:
Here is a video showing how one instructor used clickers in his upper division courses — this is a great little video, which really shows the thought process going into each question
And while we’re on the subject of clickers, here are a few very useful books on using them in the classroom:
Peer Instruction is the “bible” of clicker usage, including sample questions in physics. This text will change the way you teach! Derek Bruff’s new book Teaching with Classroom Response Systems comes highly recommended by Eric Mazur himself, which is high praise! Doug Duncan’s Clickers in the Classroom is a short and pithy gold standard of how to use Peer Instruction in the classroom.
I am a science education and communications consultant -- view my website for my full range of services.
I recently gave a talk at the AAPT about how we’re using clickers in upper division physics, and I keep meaning to include this as a post here! I wonder, should I submit this to The Physics Teacher, perhaps?
First off, you can download my powerpoint, as well as the accompanying videos, here. There are a whole bunch of different resources on clickers (clicker banks, videos in progress, useful links) at that website as well (http://STEMclickers.colorado.edu) and on my YouTube channel.
Clickers in the Upper Division
Some people disagree with the use of clickers at the upper division (or even in the lower division). We find them incredibly valuable as a tool to engage students so they get (a) to talk to their peers, (b) get feedback on their performance in a private way, and (c) the instructor gets instant feedback on what the class is understanding. We typically ask a question, then ask students to discuss it with their neighbors to convince each other of their answer. They click in and we discuss the question as a class. I’ll write a post in more detail about clickers later, but if you want to know more, go to Derek Bruff’s blog, or take a look at his excellent book Teaching with Classroom Response Systems: Creating Active Learning Environments. He also has some resources posted here.
You can see more recommendations on books on clickers at my sciencegeekgirl picks page.
Using clickers in the upper division is a little bit controversial. Many faculty disagreed with our choice to use clickers at this level, and still do despite the data showing that it was an effective way to teach. There is a sense that clickers are “babying” the students, or not serious.
The history of upper division clickers at CU
We’ve been using clickers in the upper division at CU since 2004 in classes from Stat Mech, to Classical Mech, to E&M and Quantum, plus one graduate course (AMO) — a total of 26 classes and 10 courses. This hasn’t just been the work of Physics Education Research (PER) faculty — it’s been a real mix of PER and non-PER. One thing to note is that, with just two exceptions, faculty had taught an introductory course using clickers before they used it in the upper division.
We’ve been working on transforming two of our courses in particular, to be more interactive — junior level Quantum I and E&M I. Let’s look at Quantum I. This is typically taken by 2nd semester juniors, and is currently in its third semester of transformations. It was co-taught by a PER instructor (and expert clicker user), Steven Pollock, and a non-PER instructor (new open-minded clicker user), Oliver DeWolfe, this last semester.
Let’s see how this looked in action — here is a video showing Steve using clickers in this quantum class, students talking about what they got out of it, and Oliver discussing whether he thought clickers were a good thing.
There was an interesting discussion on a college level email list recently about classroom management, where an instructor was trying his darndest to create a group learning environment in his classroom, but ended up with a bunch of rowdy off-task students. A whole plethora of responses flooded in with personal experiences on classroom management and tried-and-true tips for getting these active learning strategies to work in practice. Here are some snippets from that conversation.
The original question (from Paula Engelhart) was:
The pedagogy works great and the students really seem to get a lot out of it but…. what I’m having difficulty with is controlling the amount of social interaction that is occurring in the second semester class.It wasn’t very difficult to keep them on task the first semester in part because they wanted to know the answer to the activity. Moving into the more abstract ideas of the second semester they don’t really seem to care as much and also many of them were together last semester and know each other. Some days I have a very hard time getting them to stop talking at the beginning of class to get class going.
Julie Libarkin had similar problems in a large (275 student) class. She felt the group work was very useful, but had trouble getting them to stay on task during the activity and then struggled to bring them back together afterwards. She posted a query to the Chronicle of Higher Education and got some useful suggestions:
1) Establish a standard routine for group work. For example, always let the students know before group work begins what the purpose of the work is, tasks they should plan to do during the activity, and products they should expect to have completed or close to completion at the end of the activity. Set a time limit for the activity – you can always add more time if the class wants it. Write everything on a slide that is displayed during the group time. For longer group work, have some mechanism for grabbing attention about mid-way through the activity, like a clicker question geared towards the first part of the activity or a brief discussion of common problems you have observed cropping up in groups.
2) For me, the hardest thing was getting students to settle down when it was time to finish up the activity and have a class discussion. I got this great advice: Have a slide (mine has cartoon images that move randomly around) start playing 2 min before groups should be done. Have a countdown clock on the slide. This worked like magic for my class, especially since I told them about it ahead of time, and we even practiced the whole quiet down thing. If your class is really hard to settle down, you can also have music that plays and which gets louder and louder as the end time approaches.
3) For engaging the class in discussion: I assigned my students to group numbers, mostly as a mechanism for handing back assignments. Each group has a folder which they pick up and return themselves at the start/end of class. Even though my groups are not formal in the classic sense, the group numbers help with discussions. If I ask a question about the activity, and no one responds, I shout out a group number. Someone from the group always pipes up. If no one from that group is in class that day (happens occasionally), then I write it down. I don’t actually do anything with this information usually, but the rest of the class is empowered to speak up if they think not speaking up is somehow detrimental.
Melissa Dancy shared this advice (which was seconded by Chandralekha Singh)
One thing I’ve found that does help is to walk up to a group that is not on task and start asking them questions to force them to engage in the material. This works if the class is small enough that I can visit each group regularly but for my larger class the time it takes me to get from one group to another means they can spend lots of time off task.
This is a good use of Learning Assistants — a model created at the University of Colorado (where I’m at) where good undergraduates are given the job of helping to facilitate peer discussion by circulating the room during lecture. They help students learn, get good experience themselves, and can also help with these classroom management issues.
I am a science education and communications consultant -- view my website for my full range of services.
I’m going to try posting a regular feature here on sciencegeekgirl — Hands-on Science Sunday. I figure, if I were a teacher, Sunday might be the day I’d appreciate getting an idea of a science classroom activity. So, here you go.
Why do it?
This is a good activity to help your students visualize percentages (including really small percentages), as well as calculating ratios, all while learning more about the composition of the atmosphere and why carbon dioxide is so important. You can adapt this activity to middle school, but I believe it’s more suitable to 9th-10th grade.
Materials:
Rice
clear plastic bottle
food coloring
digital scale
funnel
What to do
First, you’ll want to dye a bunch of rice different colors. You’ll need 4 colors (plus white) — each color will represent one constituent of the atmosphere. I found that sushi rice soaks up somewhat diluted food dye fairly well — here is an activity sheet on rainbow rice (PDF). Tough to mess up, but messy all the same. If you want to get fancy, you can buy black rice, but this quickly gets expensive. In fact, because each atmosphere model uses a litersworth of rice, you will want to have students team up on this activity to reduce materials’ cost.
Then, using the percentages of the different constituents of the atmosphere, fill the bottle with those proportions of rice, using a scale. (This is tricker than it seems, see the handout, below, for a good method to do this systematically).
78% nitrogen
21% oxygen
2% water vapor
1% argon
0.04% carbon dioxide
Add the nitrogen and oxygen first and mix them up. This gives you a good visual of what 78% and 21% mean, in terms of how the constituents are spread throughout the volume.
Then throw in the water vapor and argon.
Wow. It’s not very much. But water vapor is a significant contributor to global warming.
Now put in 3/4 of the carbon dioxide grains. That’s the earth’s atmosphere in 1880.
Now add the rest of the carbon dioxide. Those are today’s levels. So, why do we care so much about the increase in carbon dioxide in the atmosphere? Because the rest of the atmosphere is transparent to the infrared. Carbon dioxide “traps” infrared (because infrared light makes its bonds jiggle, so it sends some of that heat back down to earth).
Shake up the bottle to mix up the grains. Now see if you can find any of the argon, carbon dioxide, or water vapor, as you turn the bottle around.
You can see a bunch more activities from me and Paul on climate and weather here.
I am a physicist, writer, podcaster, and educator in Boulder, CO. On this blog I get to wax on about science stuff I think is cool (like weird science, or stuff we think is true but isn't), K-16 science education, hands-on science activities, teaching pedagogy, and how to communicate science. Geek on. 8-)
ne of Paul Hewitt’s favorite demos to show that suction cups stick because of the air pressure pushing (rather than a “sucking force”) is this atmospheric pressure mat. You can lift a whole lab stool once you stick this down on it. A similar but smaller version is these atmospheric pressure cups.
A vacuum chamber/pump will let you reduce the pressure on anything (they suggest marshmallows), explore gas laws, etc. See the website for some example class activities. They also have a class set.
. He also has some resources posted 
’)
