I just got this question from a teacher on Webconnect (which lets teachers ask science questions):

“In the past when I taught electricity I always understood that it flows from the negative terminal to the positive.   The CPO books and materials have the opposite – from positive to negative.  This doesn’t make sense to me in how you generate the flow of electrons, pulling to the opposite charge.  Is the book wrong or have I forgotten stuff? 8th grade teacher”

It depends on what you define as “electricity”.  Do you mean the flow of “electrons” or the flow of “current”?  Because, due to an unfortunate quirk of history, the direction of *current* flow is opposite to the direction of *electron* flow.  Take a moment and re-read that, because it’s not what you would expect.  If electrons are flowing to the right across this screen, then we say that current is flowing to the left.

So, let’s say that the left hand side of this screen is the positive terminal and the right hand side is the negative terminal

+                  -

*Electrons* will flow towards the opposite charge, as you say.  That’s which direction?  Right to left

<—-  electrons

But *current* is the opposite direction.  Left to right.

—-> current

So *current* does flow from positive to negative, like your books say.  And electrons do get pulled towards the negative charge, like you say.  But we define electric current to be the opposite direction of electron flow.

There’s some good history on why it’s defined this way, but I’m too busy to find it right now — if someone has a good link, stick it in the comments, thanks!

UPDATE 4/27

Here’s a relevant comic from xkcd

A recent volume of Science News had a feature article about attraction and the evolutionary basis of our conception of what makes someone beautiful.  As writer Elizabeth Quill says (I love this quote) — “For humans, there is osmething captivating and unforgettable about the arrangement of two balls, a point and a horizontal slide on the front of the head.”  Put that way, it’s pretty darn surprising, isn’t it?  Turns out that our brain gets the same dose of dopamine rewards from seeing a pretty face as from food, drugs or money.  Would we press little levers to see pictures of Brad Pitt like a rat presses a button to get doses of cocaine?  Food for thought.

Anyway.  One of the major points of the article was that we find composite faces — those that are very average, with irregular features smoothed out — very attractive.  They figured this out back in the late 19th century when Sir Francis Galton made composite photos of criminals to try to get a prototypical “criminal” face.  He found the result to be surprisingly, well, beautiful.

You can make your own average faces at faceresearch.org. You can also make a baby by uploading the mother’s and father’s faces!

Here’s one I made using just women’s faces:

faceresearch.org

And here’s one I made using just men’s faces:

faceresearch.org

And here’s one using a mix of men and women.  Trust me, the faces I chose were pretty non-beautiful overall.

copyright faceresearch.org

Also some surprisingly beautiful faces at Anthony Little’s website, alittlelab.com. I’m struck by how much I like looking at these average faces.  I definitely feel those dopaminergic receptors having a little party.

Symmetry was also mentioned as an aspect of attractiveness (a symmetrical face is more attractive), which can be a sign of health.  I’ve heard the “symmetrical faces are attractive” argument before — this article suggests that symmetry may not be as important as indicated previously. Here’s a face made symmetrical and antisymmetrical.

Also, whether a face is more masculine or more feminine can affect its attractiveness, and women are especially affected by these factors when they’re ovulating!

Read the original Science News article and see some more interesting pictures of morphed faces.

UPDATE: I’ve just posted a new article about how educational innovations do (and don’t) spread around.

Do active learning strategies work?

This article — and especially the lively discussion in the comments — argue about why college instructors aren’t using active learning strategies, and whether there is evidence that such strategies work.  He says:

People have known for a long time that college students learn more when they’re actively engaged in learning via hands-on practice and other means. But many professors refuse to adopt these methods, because they don’t want to and they don’t have to.

Am I missing something? To be clear, I’m not advocating for some kind monolithic scripted curriculum. When I put my class together, I made choices about subject matter and methods that suited my expertise and instructional strengths and weaknesses. But it seems to me that the more autonomy faculty are given in the classroom, the greater the burden of proof to demonstrate that their choices are actually working, with that proof being based, in significant part, on some evidence of what students learn. Isn’t that what higher eduction is all about — evidence?

His commenters didn’t necessarily agree.  As taken from Richard Hake’s summary of the discussion:

2. “Chemprof” wrote on 6 Feb 2009:  “Always using hands-on or active learning methods is inefficient. Students like it because it is more fun than lecture, reading, or ordinary group reviews, and administrators like it because it looks exciting and innovative. However, these activities take a long time, and require a significant slowing of the pace (dumbing down) of the class. Making a class easier is usually popular with students because they don’t have to work as hard. It is also popular with administrators because more people pass, so they can brag about ‘student retention’. Of course, students will graduate not knowing very much, and they won’t be able to compete on the world marketplace, but that isn’t the administrator’s problem anymore.. . . . .”

10. Joseph Foster wrote on 9 Feb 2009:  “. . . lecturing is quite efficient, and at least when well prepared and students have attention spans beyond that encouraged by Sesame Street, it is also quite effective. And not just for imparting ‘information’[although our students are certainly lacking in it], but for showing how to develop ideas, arguments, how to tell the difference between facts and data, and how to work from a set of data to significant generalizations.]. . . . .”

22.  ‘Dr. Mike” wrote on 10 Feb 2009: “. . . .Keeping kids ‘involved. in class, in spite of it’s inefficiency, now trumps lecture. It encourages the view that learning is the responsibility of the professor, and that learning occurs only in class. Ironically activities that are labeled as ‘active learning’ in a group setting in class are anything but in a broader sense, as they reinforce many students’ ideas that ‘active learning’ on their part as individuals outside of class is and should be unnecessary. So why do so many professors continue to lecture in spite of the constant railing of educational ‘researchers’ not to? . . . .[Not so - see e.g., Schwartz & Bransford (1998)]. . .
Lecturing is an efficient way to cover the material while still allowing topics to be covered in depth. It has proved to be a very effective mode of learning for hundreds of years. And, I suspect, that when many have experimented with ‘active,’ ‘student-centered,’ or whatever you want to call them, methods out of some sense that they’re not ‘keeping up’ with changing times ( like myself), they’ve found them to be unsatisfactory. When educational ‘research’ and theory actually begin to jibe with personal experience of effectiveness (the ultimate form of evidence) , then they’ll be given more credence, not before.”

Wow.  And it just got more vitriolic from there, including mudslinging at my boss (Nobel Laureate Dr. Wieman, who devoted his Nobel $$ to furthering science education and research).

Bill Goffe wrote in: For a great intro to why physics is moving to interactive approaches to teaching (which is based on reams of data), see  “Why Not Try a Scientific Approach to Science Education?” (PDF) by Dr. Wieman.

Here is a pithy quote from that article, which summarizes quite well what my job is about:

“Our society faces both a demand for improved science education and exciting opportunities for meeting those demands. Taking a more scholarly approach to education-that is, utilizing research on how the brain learns, carrying out careful research on what students are learning, and adjusting our instructional practices accordingly-has great promise. Research clearly shows the failures of traditional methods and the superiority of some new approaches for most students. However, it remains a challenge to insert into every college and university classroom these pedagogical approaches and a mindset that teaching should be pursued with the same rigorous standards of scholarship as scientific research.
Although I am reluctant to offer simple solutions for such a complex problem, perhaps the most effective first step will be to provide sufficient carrots and sticks to convince the faculty members within each department or program to come to a consensus as to their desired learning outcomes at each level (course, program, etc.) and to create rigorous means to measure the actual outcomes. These learning outcomes cannot be vague generalities but rather should be the specific things they want students to be able to do that demonstrate the desired capabilities and mastery and hence can be measured in a relatively straightforward fashion. The methods and instruments for assessing the outcomes must meet certain objective standards of
rigor and also be collectively agreed upon and used in a consistent manner, as is done in scientific research.”

Then on 11 Feb 2009 “Dr. Mike” commented:

Dr. Wieman claims to have educational research to show the superiority of his ideas (although the process by which, and context within which, these were arrived at are not detailed). . . . . . .my training as a scientist and my sense of logic only allows me one conclusion: whatever educational ‘research’ is, its not ‘research’ in the same sense that scientific research is. I suspect that most of us necessarily rely on our own experience more than the pronouncements of others, regardless of their good intentions and credentials. In short, educational research will be given more credence when personal experience can consistently demonstrate its validity.”

I’ve seen this “education research isn’t valid” argument before (in fact, I’ve made it myself).  Certainly the knowledge we gain from education research is of a different flavor than that we get by, say, accelerating protons around a huge track.  But the real test is repeatability.  If we get the same result in different contexts, then we can say that this is something that we accept, as scientists, to be true.  We can write theories to explain it, and then do more measurements to see if it fits the theory.  So far, “active engagement produces learning” seems to fit a great many theories and we have multiple data points to support it.

One comment by John Clement I found particularly interesting:

One of the curious things is that science researchers do not recognize that even scientific articles are designed to convince the reader.  The reader can not look at the original data and analysis and has to take the author’s word on good faith.  There are articles that detail how this type of thing is done.  Actually any scholarly article is designed to do the same thing no
matter what field it is written in.  I suspect that it would be possible to write a completely bogus article for a scientific journal, have it accepted, and have readers think it is interesting.  This has been done in other journals.  Now it may be that some of the traditionalists can not read an
education article because they do not understand the assumptions made by the author.  But I think many would be surprised if they actually read some of the better ones.

And of course, if we want others to accept our arguments and data, we should write them so they make sense outside of our discipline!  (I was happy when a participant at my talk at the AAPT on Monday said that the speakers in that session — on clicker usage — “talked like real people.”).

Dewey Dykstra also argues that clearly our data hasn’t been sufficient to produce disequilibration in faculty — in other words, they’re happy with their current model (students aren’t smart enough) and see no reason to switch to a new model (students need to be engaged to learn).  If the data don’t shake them up, they won’t change their view.  In fact, any time anybody has changed their fundamental views of the world, it’s been because of some mental shake-up like this (cognitive dissonance anyone?).

Here is a very nice review (from a teacher’s listserv I’m on) about what sounds like a great book for the chemistry teacher:

A good book about Chemistry for the middle school and high school:  “A Demo a Day, A Year of Chemical Demonstrations”, by Gross, Bilash and Koob.  It has “Separating Metallic Iron from Cereal”, the simplest form of which is to put iron-fortified cereal in a plastic bag with a magnet and shake.  “Many cereal companies add fine powdered iron to their cereals as the U.S.RDA for iron.  Most people assume that cereals are fortified with a soluble ionic form of iron and not iron in its elemental form.  Once ingested, the iron will react with the acid in one’s digestive tract to form iron ions which in turn may be absorbed into the body.”

“Potato Candle” describes how to make a candle using a cylinder of potato as the candle wax and a Brazil nut for the wick.  It is designed to show the importance of observation, while grabbing the students’ attention.  The teacher who wrote this demo was big on showmanship;  after simply telling the students that they are observing a candle, he turns out the lights and asks them to write their observations.  He blows out the candle before it burns out and asks them to read their work aloud.  “Someone will see the wax melting, the braided wick, the carbon dioxide and water vapor coming off.  Remind them about observation and interpretation and how they might have to change their conclusions on the basis of new evidence.”

“If you have timed this correctly, there will only be about one minute left in the period.  Now eat the candle and walk out of the room – never tell them what it was!!!  This will convince your classes that you are an eccentric.  There is a lot to be said for this.”

There’s good variety in this book, so you might like to look at it.

I notice that there are similar books of demonstrations for the physical sciences, biological sciences, etc.  But they appear to be out of print! If anyone knows a good source for these, please post it!  Flinn Scientific appears to carry it (and here’s the Physical Science book).

Students really struggle with the metric system.  I know I still do.  I have a rough iea of how long an inch is, and how long a foot is, but I don’t have a great sense of how long a centimeter or meter is.  In this episode of Science Teaching Tips, TI staff educator Lori Lambertson tells us how she helps students get a handle on what the units really mean by using familiar objects — students’ own bodies.

Listen to the episode – Body Metrics.

There is only one episode of Science Teaching Tips remaining! There is no more funding to continue producing this podcast. If you’re interested in seeing this continue, please let me know (and perhaps I can scrape together some funding). If you have a suggestion of where we might find some dollars to keep producing this, please, do tell! It’s been a lot of fun and we have a lot of subscribers, I’d love to keep doing this.

I’ve been meaning to post this tidbit from Yahoo News for a while.  You want a jaw-dropper?  Read this!

The Worst Food of 2009

Baskin Robbins Large Chocolate Oreo Shake
2,600 calories
135 g fat (59 g saturated fat, 2.5 g trans fats)
263 g sugars
1,700 mg sodium

We didn’t think anything could be worse than Baskin Robbins’ 2008 bombshell, the Heath Bar Shake. After all, it had more sugar (266 grams) than 20 bowls of Froot Loops, more calories (2,310) than 11 actual Heath Bars, and more ingredients (73) than you’ll find in most chemist labs. Rather than coming to their senses and removing it from the menu, they did themselves one worse and introduced this caloric catastrophe. It’s soiled with more than a day’s worth of calories and three days worth of saturated fat, and, worst of all, usually takes less than 10 minutes to sip through a straw.

See more horrifying foods at Yahoo’s Worst Foods site.

On a slightly more enlightened note, I also just found out about this father/daughter co-penned volume, Food Bites, the Science of the Foods We Eat.  It’s now on my Amazon wish list, it’s got such gems as an exploration of hollow chocolate bunnies, what to do when salt gets sticky, and how to keep guacamole from turning brown, as well as what happens to your eyes working on anonion ring factory.  They also tackle the food industry, from Lucky Charms to juice boxes to TV dinners.  Sounds fascinating!

Hey, wow, I just read this wonderful do-it-yourself experiment.  A lot of people liked my previous post on the myth that no two snowflakes are alike.  Here’s a way to preserve a snowflake forever using superglue.

It turns out that the reason superglue bonds things so quickly is that it’s made of a bunch of monomers of cyanoacrylate, which then polymerize upon contact with water.  Think of it as a bunch of little legos floating around in the superglue which suddenly link up with each other in the presence of water, making something rigid.  That’s why superglue glues your fingers (which are moist) before you get it to glue your coffee cup handle back on. So, what other things are moist?  Snowflakes, for one (though suddenly I start to think of all sorts of other uses too).  The beautiful pictures of snowflakes that Wilson Bentley took back in 1931 were hard to take, in part, because the snowflakes melted.  So this guy named Tryggvi Emilsson realized that superglue’s tendency to harden on contact with water would make it perfect for preserving snowflakes.  Here’s how:

1 – Get some microscope slides, superglue (liquid, not gel), and a freezer, and a snowy day.

2 – Freeze the slides, coverslips, and superglue — you can just put them outside on a day that’s 20 degrees or colder.   Catch snowflakes on the slide or pick up with tweezers.  (Hint, dry snow days will work better than wet snow days for seeing individual snow crystals).

3 – Put a drop of superglue on the snowflake.

4 – Press down the coverslip, just like you would if you were doing biology.  Don’t press too hard.

5 – Leave the slides in the freezer for a few weeks so the glue completely hardens.

You have a beautiful snowflake preserved.  The book (below) has a picture of one that was preserved for 30 years!

This is from a preprint of a new book that looks like it will be pretty fun – Theo Gray’s Mad Science (Experiments you can do at home but probably shouldn’t). It’s not released yet, but you can pre-order it on Amazon.  Another fun tidbit from the book was how to salt your popcorn using sodium (an explosive metal) and chlorine (a choking yellow gas).  Fun for the whole family, complete with flaming drops of liquid sodium.

There’s something quietly thrilling about going to an embargoed news conference.  Even if it’s no huge shakes in the grand scheme of things (this one was on new research on the science of kissing!), there’s just this fun sense that you know something that the rest of the world isn’t allowed to know yet.  Of course, the reality of it is pretty mundane — a roomful of reporters taking notes and researchers giving quick pithy summaries of years of work.  Still,  I like being part of the newsroom at AAAS meetings – there’s this sense that exciting things are happening.  Even if they’re not.  Which they’re generally not.  At least at AAAS.  It’s a wonderful meeting, but mostly for broad survey talks, not breaking news.  Still, there is nothing quite like walking from a talk on the disappearance of ocean ice across the hall to one on Science Café’s in Europe, and then to George Smoot talking about the history and fate of the universe.  If you’re interested in following some of the news from AAAS, visit http://www.news.aaas.org.

Session: Eugenia Etkina - Pedagogical Content Knowledge

On a totally random note, I had my first sciencegeekgirl hallway recognition moment, from a faithful reader, Danielle, who writes Urban Science Adventures — a really beautiful blog helping young people explore ecology and environmental science from their backyard.  We tend to think there’s no naturalism to be done in urban environments — not true!  Anyway.  It’s geeky fun to have someone refer to you as “hey, science geek girl!”  Thanks Danielle.

For those geeksters out there, watch for my t-shirt tomorrow.  It’s Valentine’s Day.  I’m a geek.  You may be able to figure it out.

If any bloggers at AAPT would like to meet up, let’s do lunch on Saturday!  Meet at 12:00 outside the Aculpulco Room, Gold Level, West Tower.  There is a newsroom message board where you can leave us a message.  (I know you’re not newspeople, most likely, but I am, so it counts!)

Session: Eugenia Etkina - Pedagogical Content Knowledge

Why is it that we make tests multiple choice, when the world isn’t multiple choice?  We’re not an industrial society anymore, where following directions is the key to success.  Instead, we’re problem-solvers, and knowledge is the important commodity.  But our education system hasn’t quite caught up with this shift.  We’re still testing our students like they’re good little worker bees, for whom “knowing the answer” is the important skill.

But if we want to train students to be good problem solvers, we have to assess them on it.  One of Joe Redish’ teaching commandments is that if you want students to learn something, that has to be part of your assessments.

So, how to we assess problem solving skills?  Eugenia Etkina has two examples which were pretty nice.

1. Jeopardy
This is a fun game, once your students get used to it. Take this for example:
900N – (50 kg)(9.8 m/s^2) = 50 kg * v^2 / 12m.
Sketch a situation this might describe
Write in words a problem for which equation is a solution.
(Can’t figure out the answer?  Write in the comments).
This requires students to put together pieces and make conections between the formulaic descriptions of physics and physical situations.

2.  Deep problem-solving assessment

Falling ball and pendulum

Watch this video. Decide what data you need to estimate the height of the table two different ways.  How do you decide whether the two methods agree?  Hint:  You can step the video forward frame by frame using your arrow keys.  All the data you need is on that page.
(Need help getting started?  Write in the comments).
Unlike a traditional exam, this assessment

• Doesn’t tell you what to do (the student has to come up with the method)
• Doesn’t tell you to neglect air friction, etc. (this is a genuine situation)
• Tests whether they really know what uncertainty in measurement is, and how it’s different from experimental error
• There is no correct answer
• Students can learn during the assessment

If these are the skills we want them to learn, then we have to test them on it! Physics isn’t just about knowing facts, concepts, or how to solve formulaic problems.