Category: astro 101

I’m working with a veteran gen-ed astronomy (#astro101) instructor to make his classroom more learner-centered. We’re working hard on effective clicker implementation. The benefit of using clickers for think-pair-share (TPS) questions is the instructor can use the students’ votes to guide the instruction.

clicker_iclicker_UIC — i>clicker receiver and clicker (sorry, can't find credits for this pic.)

If everyone gets a question right, just confirm the answer and move on – don’t waste valuable class time re-teaching something everyone already knows! Conversely, if the students have no clue what the answer is and simply guess, you’d expect 20% for each choice A-E, 25% each if there are 4 choices, and so on. If that’s how they vote, either there’s something wrong with the question (a critical typo, perhaps) or the students haven’t learned the concept yet. Teach it again BUT NOT JUST LOUDER. Teach it again in a different way.

The “sweet spot” is when there’s a nice split between 2 or choices. The students have thought hard enough to formulate and pick the choice they feel is correct, which means they’re prepared to interact with their peers. In cases like this, we ask them to “turn to your neighbours and convince them you’re right.” Then you sit back and let them teach themselves. Ahhh.

(Well, actually, you shouldn’t sit back. You should wander around the room and eavesdrop – you’re going to hear some great ideas you can use for choices on the final exam!)

The hard part for instructors is knowing when to move on or when to get the students to discuss the question. Is 90% correct enough? Yes, probably. What about 80%? What about 60%?

In today’s astronomy class, the instructor asked the students a TPS question and the distribution of votes was A 0, B 0, C 67%, D 20%, E 13%. The instructor wasn’t overjoyed, but 67%? That means 2/3 of the students got it, right?

Wrong. Some knew the answer. And the rest guest. Er, guessed.

I did a little thought experiment with the instructor afterwards. “Suppose only half the students knew the answer and the rest just guessed. What vote distribution would you get?”

“Er, 50% then 10% for each choice, so a 60 and 10’s.”

“Great,” I said. “Suppose 2 of the 5 choices were obviously wrong. Then what.”

He thought for about 2 seconds. “67-17-17.” Our numbers from that today. “Oh.”

That’s right, when there are only 3 valid choice and only half the students know the answer, you still get about 67% success. And you might be tempted to move on even though half the students don’t know what you’re talking about!

That got me thinking – suppose fraction f of the students know the correct answer and the rest guess. What do the clicker vote distributions look like? I cast a spell with Excel (I’ve finally reached novice Excel spellcaster) and found these results:

ClickerDistWhenfKnow_5choices — Distribution of votes when fraction f of students know the correct answer is A and the rest of the students make a random guess. Each set of 5 bars show the votes for A, B, C, D, E.

(Quick limit test that us math-types do: when no one knows and f=0.0, the votes are 20% for each choice. And when everyone knows, it’s 100-0-0-0-0. Got it.)

For example, when the peak vote is 60%, only 50% of the students actually know the answer. And it gets worse when there are fewer choices (or equivalently, when you can eliminate some of the 5 choices because they’re obviously wrong.) Here are the distributions when there are 4 choice and 3 choices:

ClickerDistWhenfKnow_4choices — Distribution of votes when fraction f of students know the correct answer is A and the rest of the students make a random guess. Each set of 4 bars show the votes for A, B, C, D.

ClickerDistWhen4Know_3choices — Distribution of votes when fraction f of students know the correct answer is A and the rest of the students make a random guess. Each set of 3 bars show the votes for A, B, C.

This last chart shows our 67-17-17 vote distribution corresponding to only 50% of the students knowing the right answer.

This isn’t ground-breaking research. I bet many clicker users have done this, too. Or at least, worked out a few special cases.

The moral of the story, though: the fraction of students who choose the correct answer is always higher than the fraction of students who know the correct answer. Don’t move on to the next topic unless you get a very strong peak.

What’s your threshold for moving on or doubling-back with a pair-share?

Galileoscope eyepieces

January 23, 2011

Peter Newbury

“I put my Galileoscope together. How do I use all these eyepieces?”

That’s a question I get all the time. There are three different eyepieces depending on how you assemble the components:

Galileoscope eyepieces — There are three eyepieces for the Galileoscope depending on how you assemble the components.

Galileoscope eyepieces photo-illustration by Peter Newbury is licensed under a Creative Commons Attribution 3.0 Unported License.

The easiest way to use your Galileoscope is with eyepiece A. It gives a fairly widest field-of-view (you can see the largest region of the sky) with a 25x magnification. This is the combination I recommend to new users, parents and kids, and school groups. With this eyepiece, you can easily see the craters and shadows on the Moon and the moons of Jupiter.

The combination A+B+D gives an eyepiece with 50x magnification because B+D create a Barlow lens that doubles the magnification. The increase in magnification comes at a cost: a much smaller field-of-view and fainter image. It is almost impossible to use this 50x combination without a tripod (which the designers anticipated by building a nut into the bottom of the Galileoscope that fits any standard camera tripod.) If you have a tripod and a clear, dark skies, you can see the rings of Saturn. Yes, the rings of Saturn! And that’s magical.

Finally, there is a special lens combination included for historical (and educational) reasons. You see, the Galileoscope was designed as a cornerstone project of the 2009 International Year of Astronomy (IYA2009). That celebration marked the 400th anniversary of Galileo using his telescope to observe the Moon, Venus and, in 1610, the moons of Jupiter. The special “Galileo eyepiece” C+D mimics the view Galileo had, with a meager 17x magnification over a tiny field-of-view. The image appears right-side-up, though, unlike the 25x and 50x combinations which invert the image as most refracting telescopes do.

With all these eyepieces and magnifications, I still recommend the simplest one, just the 25x. In fact, when I’m doing “sidewalk astronomy” I keep the Barlow lenses in my pocket and pull them out only with the more advanced telescope users. Going from naked-eye to 25x already opens up a Universe of wonders.

Parents, teachers, sidewalk astronomers: The Galileoscope design team has put together a great collection of resources. You can order Galileoscopes directly from them, from Learning Encounters or check your local telescope store.

I’m really interested in learning to take pictures through my Galileoscope. If you’ve taken some good ones and have any tips, I hope you’ll share them below.

Why do we teach astronomy?

January 18, 2011

Peter Newbury

astro 101 3 Comments

I just spent a week in Seattle at the 217th Meeting of the American Astronomical Society. If you’re here via my Twitter feed, you’ve been bombarded with my #aas217 tweets. I’ll be sharing some thoughts and experiences in future posts. There was one experience that really sticks in my memory, though.

Ed Prather from the Center for Astronomy Education led a workshop that I attended. I’ve been to a number CAE workshops with Ed. He’s intense. You don’t have “thin” conversations with Ed.

Ed and his colleagues are dedicated to teaching (and teaching teachers to teach) “Astro 101”, the general education course that 100,000’s of non-Science undergraduates take each year. It’s likely their first, last and only science course. As Ed proclaims, and with which I wholeheartedly agree, we need to teach these people science. Not because they’re on their way to becoming scientists – that audience isn’t taking “Astro 101”. Rather, these people are the next generation of teachers, lawyers, politicians, journalists, parents. In this age of technology, medical advances and global warming, it’s vital that the next generation of voters be scientifically literate.

Yes, YES! Just the pep talk that gets my heart pounding! And then Ed continued…

Why it is so critical? Because high-tech, science-related jobs in the United States are not being filled by Americans.

Wazzat?

Don’t get me wrong — there is nothing wrong with patriotism. In fact, I admire how strong his convictions are. And if I dig deep enough in my brain and heart, I’ll probably say the same thing about Canadian kids. But I haven’t thought about it that way. I’m still at the “let’s do this for our kids because they’re inheriting our mess.” Maybe that’s naive of me. Or maybe it’s a Canadian/American thing. Either way, we all agree that scientifically literate citizens are critical to our — all of our — future.

Galileoscope eyepieces photo-illustration by Peter Newbury is licensed under a Creative Commons Attribution 3.0 Unported License.

Navigation