Thursday, July 20, 2017

Left Behind: Sunball Selfies

Many science instructors will be making the pilgrimage to totality for the August 21 solar eclipse. This will leave science students without their instructors during the event.

In a previous post, we offered a lesson plan to fill one day of a science teacher's absence. That was a question set to accompany showing The Universe: Total Eclipse.

What can students do on Monday, August 21 at the time of the eclipse (peaking at 10:17am in Sacramento)? It's a school day and students will likely be in class during most of the eclipse.

Perhaps your school has stocked up on eclipse viewers/glasses and will distribute them for students Monday morning. Then again, maybe not. It's important to convey the danger of looking at the sun during an eclipse.

Conceptual Physics author, Paul Hewitt, reminds us that one of the best ways to enjoy an eclipse is to look down! The dappled light seen beneath trees is composed of pinhole images of the sun: "sunballs". When the eclipse is on, these sunballs turn into "suncrescents," pinhole images of the eclipsed sun. It is quite a spectacle. Some might even call it "amazeballs".

Here's an extra credit project that I will be assigning to my students for the eclipse:

Sunball Selfies (pdf) - Sunball Selfies (docx)

You will need to modify the document to use it at your school. And you don't need to be absent to use it. I used a similar assignment for the May, 2012 annular eclipse and students had great fun with it.

Sunball Selfies student album from May, 2012
2012 05 20 Eclipse Students

My own Sunball Selfies album from May, 2012
2012 05 20 Eclipse DB

Tuesday, July 18, 2017

I have stopped recommending the AP1 and AP2 exams—when will you?

I expressed my misgivings about the AP Physics 1 and AP Physics 2 exams in a previous post. Once again, this is a rant. If you're not into rants, kindly scroll to the next post.

The purpose of this post is simply to show the global exam score distributions, three years into the redesign. I used the numbers posted by Total Registration.

First up: the final three years of the AP Physics B exam scores. Fives were earned by 15% of students, fours were earned by 19%, threes by 27%, twos by 17%, and ones by 22%. (Approximately one third succeeded with 4s and 5s.)



Next up: the first years of the AP Physics 1 exam. Fives were earned by 4% of students, fours were earned by 14%, threes by 21%, twos by 30%, and ones by 31%. (Approximately one fifth of candidates succeeded.)



Try not to judge too harshly those who have lost enthusiasm for algebra-based AP Physics.

To complete the Algebra-based exams, consider the AP Physics 2 exam. Fives were earned by 9% of students, fours were earned by 15%, threes by 34%, twos by 32%, and ones by 9%.



The College Board hastens to offer explanations for the precipitous plummet, especially in regard to AP1. The AP2 scores actually match the legacy APB results reasonably well. There's reason to speculate that many (if not most) AP2 examinees are successful veterans of the AP1 exam.

1. Teachers aren't teaching the new course correctly. They haven't undergone enough in-service retraining. (This is part of the admission that the AP1 and AP2 exams aren't really about physics anymore, but about Big Ideas. Physics topics are merely the canvas upon which the Big Ideas are painted.)

2. Too many students are taking the AP1 exam. This is where I'm trying to help. And you can, too. I assure my students that I will do my best to prepare them for the exams as they are. But I encourage them to not submit to the exam. This reverses a position I held for 25 years. If we work together, we can help to reduce the glut of AP1 examinees.

The Physics team at the College Board has replaced the muscular Camaro that was AP Physics B with shiny Lamborghinis called AP Physics 1 and AP Physics 2. Emulating the college course that examinees could test out of is now a long-abandoned goal. The new courses hope to be the richest, most immersive physics courses that could be imagined.

I don't find the course syllabi to be particularly practical for high school students. The courses go well beyond virtually all introductory college and university courses. The AP Physics B exam was more demanding than those administered at the college level. And the AP1 and AP2 exams amplify that disparity to 11.

Surely this escalation of difficulty of the AP1 and AP2 exams must have resulted in a global advancement of the way colleges and universities accept and interpret passing scores. If it has, I am unaware of it. In the old days of AP Physics B, college acceptance of passing scores was a crazy patchwork. To the best of my knowledge, the crazy patchwork remains unchanged even with the more stringent AP1 and AP2 exams.

You might wonder why AP Physics C instructors remain enthusiastic about their course and exam. They were unaffected by the AP Physics B redesign. Let's bring them into the mix.

While the AP1 and AP2 scores plummeted, the un-redesigned AP C Mechanics exam scores continued to flourish. Over the past three years, fives were earned by 31% of students, fours were earned by 28%, threes by 18%, twos by 13%, and ones by 10%. (Nearly 60% success rate.)



The score of 5 (highly qualified) now represents the mode.

The un-redesigned AP C Electricity and Magnetism exam scores did well, too. Over the past three years, fives were earned by 30% of students, fours were earned by 24%, threes by 14%, twos by 19%, and ones by 13%. (More than half succeed.)



The score of 5 (highly qualified) continues to represent the mode.

AP Physics C continues to be a physics content-based exam. That is, its blueprint refers to topics in physics instead of the more philosophical Big Ideas that form the core objectives of AP1 and AP2. This may well be a key to the continuing success enjoyed AP C examinees.

Of course there's more to this discussion. I'm obviously ventilating a bit here because this continues to be a source of frustration. AP Physics C is not a viable option at my school due primarily to its prerequisites. Intra- and inter- district competition for school enrollment prevents me from simply abandoning AP1 and AP2. If not for that, I would.

With haste.

Monday, July 17, 2017

Left Behind: The Universe - Total Eclipse

For instructors making the pilgrimage to totality for the August 21 eclipse, there is a chance school will be in session and lesson plans will need to be prepared for guest teachers (aka, substitutes).

One day could be covered by the showing of the "Total Eclipse" episode of the A&E documentary series, The Universe.

The program, episode 7 of season 5 (The Universe S5E7), originally aired September 16, 2010. It can be found online. I leave it readers to source the best version and to make it available for a classroom showing.

As I do for virtually all video programs I ever show in class, I have prepared a question set to accompany the episode. A sequence of questions that can be answered while the video plays tends to keep students appropriately focused. It is available, free of charge, at my nascent Teachers Pay Teachers website: The Resources of Phyz. I have found useful resources there and plan to add more to my own corner in the future. For now, the "Total Eclipse" question set is all that I have posted.

The Universe - Total Eclipse video questions

We will add to our "Left Behind" series with other activities for students not traveling to totality in future posts.

Thursday, July 13, 2017

Reining in the kilogram once and for all

It seems we're been here before. More than once. The kilogram: a pesky unit of measure that hasn't been behaving itself.

Derek Muller goes deep into the explanation of the newly redefined kilogram. The task is not trivial. I may need to rewatch this robust explainer a couple of times before it all sinks in. Have a seat and prepare to get your geek on: there will be mathematics!

How We're Redefining the kg

Sunday, July 09, 2017

Total Eclipse of the Sun - Part 3

As I mentioned in Part 2 of this four part series, I will be observing the August 21st total eclipse of the Sun from Madras, Oregon. My main reason for this choice is the prediction for low cloud cover as you can see on this chart from Eclipsophile:
The chart shows there are many other good choices, but Madras is one of the shortest drives for me, nine hours. Another reason I am going to Madras is I was asked to help with the Lowell Observatory Solar Eclipse Experience 2017. This event at Madras High School will include daytime activities and talks by astronomers on Sunday and Monday and night time star gazing on Sunday. If you are planning on being in the Madras area, I encourage you to purchase tickets for this event. In addition to the program of events, your $15 will get you a pair of eclipse glasses, access to a water station, food and beverage vendors, and the air-conditioned auditorium. The eclipse itself will be narrated by solar astronomers. In this post I will describe my contributions to the Lowell event and ideas for you to enhance your total and partial eclipse experience.

Rich Krueger contacted me last year about contributing to the Lowell Observatory Eclipse Event. Rich teaches at Flagstaff Arts and Leadership Academy and is a fellow SOFIA Airborne Astronomy Ambassador. Rich flew on SOFIA with Lowell Observatory Curator, Samantha Thompson. Lowell tapped Rich to help fill out the outstanding program they are preparing for the day before and day of the eclipse. Rich originally wanted me to recreate Eddington's total eclipse observation that confirmed Einstein's Theory of General Relativity. I had read Donald Bruns' article in Sky and Telescope and knew this was beyond my skill and bank account. Even Mr. Bruns is only doing half of the experiment. He plans to use undeflected star positions from the Gaia catalog. Eddington did not have this luxury! I assured Rich I would bring something else that would interest and engage the crowd. Others may try to measure the star field around the eclipsed Sun at the Eclipse Experience, but the deflections are so tiny nothing will be evident that day.

My first thought was to bring the Spacetime Simulator that I use in the viral Gravity Visualized video. I would do demonstrations like the ones in the video plus the new ones I have added. Another idea is to make a bent spacetime game by distributing a bunch of 0.5, 1, and 2 kg masses on the fabric. Place a goal on one side and launch a marble from the other. The marble represents a photon following the geodesic of the warped spacetime. The winner reaches the goal in the longest amount of time. Doing these activities should keep me pretty busy, but I wanted to develop something new too. I also suspect that I won't be the only one bringing a spacetime simulator since so many people have built their own with the help of this DIY video.

My next idea was to make a large convex mirror using a spaceblanket and a kiddie pool. I briefly alluded to this at the end of my post about making concave and convex mirrors with trashcan lids and spaceblankets. I was inspired to create a large convex mirror by the fisheye lens pictures taken in previous total eclipses. They show a 360 degree sunset with a brilliant but small eclipsed sun floating in the twilight. I also remembered the picture of the 1991 total eclipse over Mauna Kea. You can see the eclipsed sun and sky in the reflection of the silvered observatory dome on the left. I wondered what you could see in a large convex mirror placed flat on the ground. Maybe it would give a similar view to the unaided eye in real time.
From Sky and Telescope 35mm slide set
Wolfgang Strickling, 3/9/2016 Eclipse
















I picked up a 45" wading pool from Big 5 Sporting Goods.  I cut the presta valve from a bicycle tube, put it through a hole in the side of the pool, and sealed it with silicone adhesive. I used the top of the pool to mark a circle on the spaceblanket and cut it out.  I used strapping tape to attach the spaceblanket over the top and started inflating it. It worked great, here is the result:
45" Spaceblanket/Kiddie Pool convex mirror
Outside the mirror showed the horizon and the whole sky. I should have left well enough alone but I was curious about how much more I could inflate it. I attached my portable air pump and added more air. The mirror stretched a little bit more but then reached its limit. Unfortunately I did not notice this until the side of the pool buckled. I would need to take it apart and reinforce it. Instead I decided to start from scratch with a bigger pool. I found a 59" kiddie pool at Toys backward R Us. Since spaceblankets are 52" wide, I obtained an oversized one that is 71" wide. To help prevent the pool from buckling I got some lawn edging to attach around the outside of the pool. I drilled holes and used bolts to secure it, then sealed each bolt with silicone adhesive. To prevent buckling, I used a

string to measure the mirror while inflating it. When the string showed the spaceblanket was not stretching anymore, I stopped inflating it. The larger mirror gave a satisfying view inside my classroom and outside in the full sun. I can't wait to see what it looks like during a total eclipse of the Sun. If I had to do it again I would stick to the smaller version. The large mirror barely fits into my Honda Odyssey and the oversize spaceblanket is not as reflective as the regular size. I may even make another smaller version to take instead of the large one since I will need room to transport a lot of equipment and gear to Madras.


I have been observing the Sun, solar eclipses, and transits with students for many years. As a result I have a good collection of solar observation equipment. The pièce de résistance is a Coronado Solarmax 70mm H-Alpha telescope (discontinued). I purchased this many years ago with a grant from the Home and School Club, Los Gatos High's version of the PTA. I made sure to come to one of their meetings after getting the telescope to show them the prominences, filaments, plages, and supergranules that students would get to see. If you want to get something similar for your school, the Coronado Personal Solar Telescope is very capable and more affordable at $599. I will bring a Meade 10" SCT with solar filter, 20x80 binoculars with solar filters, a box of eclipse glasses, and an 80mm refractor with a Sun Funnel. What is a Sun Funnel? That is what I thought when I first came across this solar observing aid. It is a safer way to do eyepiece projection, pointing an unfiltered refractor at the Sun and aiming the eyepiece toward a screen. Once focused, a nice large image of the Sun shows up on the screen. I have done this many times but always worried someone would look in the eyepiece and injure themselves. The Sun Funnel is placed over the eyepiece and projects the image on the back of a screen fastened to the other end. I followed the very clear instructions and made one in about 15 minutes after assembling the materials. If you have access to a small refractor, I highly recommend you build one. Small refractors can be purchased for less than $100 and work well with the Sun Funnel as long as you use an eyepiece and star diagonal that are made of metal, no plastic.

http://www.hoydalsvik.net/astrofoto/eclipse2008/
The partial phases of the eclipse can be observed without any additional tools. You can simply overlap the fingers of each hand, making a waffle shape, and project pinhole images of the Sun on the ground or other convenient surface. The images can be improved by making pinholes in a screen and holding it above a flat, light colored surface. The further the pinhole is from the surface, the larger but dimmer the image will be. If the screen is in a shaded area, the images can be seen easier.  Some people even create a design with the pinholes, creating an image made up of crescent Suns. There are many creative plans for pinhole projectors that are described elsewhere. You can even measure the diameter of the Sun with a pinhole projector. The ratio of the diameter of the image to the distance between the pinhole and the image is the same as the ratio of the diameter of the Sun to the distance to the Sun. If there are trees, bushes, or other objects with small openings, you may notice small crescent images scattered across the ground, walls, etc. If you have access to your eclipse site ahead of time, scout around at the same time as the eclipse to locate the best examples. I won't have that opportunity so I am stacking the deck. I am creating a pinhole pattern out of a prototyping or perf board. These are used for electronics projects and have a grid of tiny, closely spaced holes. I use them for an inverse square activity in workshops (click to download). I ordered a large one (18x12.8 cm) that I will create a pattern on by masking selected holes. I am undecided what that pattern will be, if you have an idea, leave a comment. In Part 2 of this series I advised against using precious total eclipse observing time to take pictures. However, you will have plenty of time during the partial phases to photograph the crescent pinhole images, natural or contrived. That's what I did for the June 10, 2002, partial eclipse at my home in California. Sky and Telescope published my photo in the December issue of that year.




[Dean adds: for the May, 2012 eclipse, I made "eclipse portraiture" an extra credit project. My own "before and during" has been published in a few places.] 


Another way to reveal the partial phases of the eclipse is to reflect a solar image from a mirror. I use this to bring the Sun into the classroom. I use a front-surfaced mirror to get a crisper image. I mask off the surface of the mirror except for a hole made with a paper punch. This produces a brighter image than a pinhole so you can project it over a longer distance to create a larger image. You still need to project the image into a shaded location to make the it easily visible. I am going to place a sheet of white paper in a box for the eclipse.
Solar Spectrum using Red Tide spectrometer with Logger Pro
 

Projecting a solar image is useful even if there isn't an eclipse going on. Imagine a solar image projected through your classroom door onto your whiteboard for the whole class to see. Large sunspots should be visible. After a little time, students will notice that the solar image moves. Propose the idea of determining how much time it would take the solar image to move all the way around, back to where it started. Draw a circle around the image and time how long it takes to move completely out of it.  How many images would it take to complete one circle? The Sun's apparent size is about 0.5 degrees so 360/0.5 = 720. Multiply the time measured by 720, this should give about 24 hours. How about that! You can improve your answer by calculating the exact apparent angular size of the Sun for the current distance to the Sun on the day you do this activity. I also use a spectrometer to display the solar spectrum using the projected solar image as the light source.

As you can see, I will be very busy for the total eclipse on August 21st. Even if you can't make it under the path of totality, I hope you will be busy sharing this event with your students, family, and friends. I have used this post to give you some ideas to enhance the experience. I urge you to use them in your classroom beyond the Great American Eclipse day. The concluding post of this series will describe my experience in Madras. It will be interesting to contrast it to my first total eclipse experience that I described in Part 1 of this series. I also will be posting live on Twitter @kilroi22.


Colored Shadows Tough Problem

I have mentored and coached for the New Teacher Program through the Exploratorium's Teacher Institute for several years now. Many summers I get to work with teachers in their first few years of teaching as they participate in an intensive three week institute. I went through it myself ten years ago and it is a lot of great information and wonderful pedagogy. I learned more in those three weeks than in my entire credential program about teaching science.

It is exciting when a new teacher discovers or comes up with something that is so cool it has be shared. Summer 2016 Ajayi Lawrence was focused on light and took a journey through diffraction, color addition, filters, etc. There were several times that we took red, green and blue LEDs to darker exhibits to experiment. Lots of "Oh that was cool, do that again!" and talking out what we saw, especially when it was contrary to our predictions. (It's good to be wrong sometimes!)

While trying to set up a procedure for his students, Ajayi shone a red LED through the two filters of a pair of 3D glasses. The red light passed through the red filter and was almost completely blocked from the blue-ish filter, as expected. The blue light was blocked by the red filter and shone through the blue-ish filter. The green light was blocked by the red and shone through the blue-ish filter. (Now you seen why I say it was "blue-ish.")

Later we took the same pair of glasses to the Colored Shadows exhibit (which can be recreated in your classroom using this Science Snack) and snapped this great picture.
Ajayi and I both said that showing this picture to students and asking them to determine the colors of each filter would be a great way of  assessing what they have learned about color addition and subtraction. This year in our color unit I showed this picture to my students and didn't tell them that they were 3D glasses. After some discussion they realized that the two lens of the glasses must be different, which reminds them of "old" 3D glasses. Most of your students will have never used red-blue 3D glasses before, by the way. After they discover that they have to think about what light passing through one of those filters would look like versus lighting being blocked by the filter. 

This was done as a quick end of class activity to wrap up some other concepts. I would have preferred it to be discussed in small groups with whiteboards so that students could make their own drawings. I've written up a worksheet that is a little more guided, adding a portion on the colored shadows of hands I already use, that is available untested as a pdf. If you want to check your answer here is a visual key.

Friday, July 07, 2017

Lab equipment older than me

While continuing to clean my prep room (no end in sight!) I found more old Macalaster Scientific Corporation boxes similar to the radiacmeter and dosimeter I found a few weeks ago. I found four different pieces of equipment, it has been interesting to research them, find out what they were used for, and try to determine if they can still be used. The company seems to have stopped production in the 1960s, although upon searching for their equipment I see many familiar things. My dynamics carts from my Crash Cushions project are apparently made by Macalaster and potentially 50 years old. Perhaps new dynamics carts will be on my shopping list this year ...

Mass of an Electron Apparatus
This uses a "Magic Eye Tube" with a circular display that was used to tune radios in the 1930s. My equipment, shown below left, had to be used with an air core solenoid, shown below right. From what I can tell these can still be purchased for about $100 each (solenoid not included) and used as demo equipment.

The instructions puzzled me a bit as they referred only to assembly so I turned to the instructions of a similar modern version.

This video shows the magic eye tube changing as a radio is tuned in and out:
It took me awhile to realize that when not used with a radio, the magic eye would produce a straight edged fan shaped wedge that would be unchanged (bottom right).  That is, unless a magnetic field is brought near it to bend the electrons and the fan shape on the display (bottom left).  That is where the air solenoid comes in, constructed to be about twice the height as the fluorescent screen on top of the magic eye tube so that it sits at the center of the solenoid. The magnetic field around the solenoid when current is running through it effects the electrons on the fluorescent screen.

The explanation describes an experiment to determine the mass of an electron approximating the curvature of the "fan" shape using something else round. You seem to need to know multiple voltages, the current and turns in the solenoid (to determine's magnetic field strength) and the curvature of the bend. The instructions end with "Refer to physics text books for the formulae relating to the calculations for the strength of the magnetic field and the velocity of the electrons. From this information you can calculate the approximate mass of a single electron." Not quite spelling it out for us, is it?

I found this image and equations on Hyperphysics that I think match up with this experiment.

I'm not 100% sure that this is the correct equation for finding the mass of an electron with a magic eye tube but it looks promising. The radius of the curve of the electron deflection due to the solenoid's magnetic field would be found by matching it to a circular object. Since it would be hard to accurately measure the radius of only part of a curve, the instructions suggest that if you find something else that has the same curvature but is a complete circle it will be easier to measure the radius. The magnetic field strength of the solenoid could be found by knowing the current through it and the number of coils. The voltage should be measured from the circuit, charge on one electron is known and that should reveal the mass of one electron.  

Potential Difference Kit
From the brief assembly instructions I think (1) I'm missing an insulating handle and (2) it is acting like an electrophorus. (Here is an Electrophrus Engineering activity by the way.) That is my guess at least, maybe someone else has a better idea of what this #unknownequipment is used for.

Tangent Galvonometer Kit
The dismantled frame (left) can be assembled (right) to make a base to hold a compass and a loop of wire. A compass (not found in the box) would be placed where the spool of wire is placed on the right. A square loop of wire is made around the four nails (two top, two bottom) that surround the compass resting on the base. This modern version shows the same set-up. There are fancier equivalents of this kit with secured circles of wire around mounted compasses. I've made similar set-ups for students with cardboard in class (start video about 30 seconds in).
I was surprised to read "This can also be used to determine the magnitude and direction of the horizontal component of the Earth's magnetic field." in the description. I found this explanation of the experiment but I'm not sure if this particular rudimentary kit would be successful. This kit is quite large, about a foot tall, and has sharp aluminum edges. This particular one has been defaced with an engraved swear word as well. While it could be useful, I can probably make some that are a bit easier to worth with.

Cathode Ray Tube
I figured it lit up when I saw it but Dan was able to tell me that this piece of #unknownequipment was a Cathode Ray Tube. This Lab Guy post shows how it could be hooked up and made to work like a small TV. That is way above my current summer level of work load though. Dan also said he powers one with a handheld Tesla Coil so until I procure one of those this may not be useful.

While I might be able to get some of these to work, some would require purchase of additional materials. One could find such vintage pieces on eBay but it begs the question, do you want to? They still hold some educational value, if their original purposes are known, but it may not be worth trying to get them to work. For the time being they will remain on a shelf with other vintage pieces I can't bear to part with.

Thursday, July 06, 2017

Rolling shutter explained by a YouTuber

The lesson is a nice complement to yesterday's photography post. Destin from Smarter Every Day produced a great rolling shutter explainer. Those weird motion-based video artifacts that your camera phone captures? Rolling shutter (not the "wagon-wheel" stroboscopic effect).

Destin's explanation benefits from his intentions and Phantom high-speed camera. And some great work in post-production. Next time I fly, I will book my tickets on "Smarter Every Day" airlines!

Wednesday, July 05, 2017

Polarization demonstrated by a photographer

In the era of digital photography and Photoshop, the use of filters in photography has declined. Some effects of photographic filters can be simulated in post-production software.

Polarization is not one of those things. I use a polarizer in my own landscape and (to some extent) wildlife photography quite heavily. (Links to that work can be found at The Treks of Phyz.)

This video recently bubbled up at Digital Photography Review (my favorite resource for digital camera news and reviews). It's a photographer's description and demonstration of polarizers. Nicely done, and it can certainly act as a springboard for the discussion of polarization in the classroom.

Take a look for yourself.

Monday, July 03, 2017

Skepticism: Gwyneth's Goopy Body Vibes

Dan Burns recently directed my attention to a dust-up regarding a Goop-endorsed product. Goop is Gwyneth Paltrow's high-priced personal product brand/store and Body Vibes was an endorsed product available at Goop. Body Vibes' body stickers could work all manner of miracles

According to a Washington Post article, Body Vibes originally claimed to use materials engineered by NASA. After NASA refuted the claim, Body Vibes reworded their sales pitch to delete the NASA reference. Read the WaPo take-down for all the details.

If you thought Power Balance style scams were a thing of the past, think again. Body Vibes gets their "technology" from AlphaBio Centrix in Las Vegas. Watch this "disturbing" AlphaBio video. It was posted in 2015 and already had nearly 800 views when I came across it. (We can't all be Dan Burns.)



They had me at "We use sub-harmonic frequency to power our Bio Energy Patches". For such statements, we must deploy the most incendiary burn in the arsenal of physics: "Not even wrong". (For the uninitiated, that means it's so very wrong that it cannot even be considered as worthy of argument.) The genius of the product design and marketing is that you could get stickers for every need, from anxiety, to low-testosterone, to gluten free(?).

Bottom line: there will always be products like this and the products will always have a credulous customer base. Do what you can to make sure your students aren't taken in by these things.

Update: I almost forgot to include Stephen Colbert's Late Night take-down of Body Vibes.



Gizmodo's takedown: NASA Calls Bullshit on Goop's $120 'Bio-Frequency Healing' Sticker Packs

TANGENT: In the course of writing this post, I wandered over to what's left of the Power Balance company page. Not surprisingly, they're still selling bracelets. Waiting for that 2010 nostalgia craze to kick in, I suppose. Amusingly, the post-lawsuit "technology" behind the bracelet is described as "Power Balance holograms are created using a proprietary process featuring cutting edge three-dimensional imaging, which makes the hologram truly unique. The hologram is designed based on Eastern philosophies. Many Eastern philosophies contain ideas related to energy. These are commonly referenced as Chi or Chakras. There are a number of well known practices like acupuncture, meditation and Feng Shu, which are believed to affect these energies. The hologram is based on some of these same ideologies." A legal work of art!

Thursday, June 29, 2017

A summertime fidget spinner I can endorse

If you aren't plugged into Derek Muller's Veritasium YouTube channel, it's time to correct that oversight.

His latest exploration involves hydrodynamic levitation. It's a phenomenon very different from the Coanda effect-based airstream levitation. And it constitutes a summertime fidget spinner I can wholeheartedly endorse!

Hydrodynamic Levitation


Muller is, of course, armed with high-speed videography. He recently added schlieren photography to his arsenal. I'm delighted to support him on Patreon; the guy does great stuff that's always fun to watch.

Wednesday, June 28, 2017

Skepticism in the Classroom: "Wireless" Bungee

Bree Barnett Dreyfuss recently pointed out this amusing feat of daring-do to me. Take a look at this breathless tale of magnetically-braked cordless bungee jumping.



As a veteran of bungee jumping, I was thrown off by the use of the term "wire" in this context. "Rope" or "cord" are common terms used to reference the bungee, but not "wire". The term is obscured a bit via use of a second language (translation issues?). But by the end, the need for the use of that specific word is clear.

In any case, it seems not everybody picked up on the clues that the whole spot was a spoof. That's what Snopes is for: Bungee Leap of Faith.

But magnetic braking is far from unheard-of. Engineered use of eddy currents/Lenz's law has been deployed on a large scale for the benefit of thrill-seekers at amusement parks for years.



It seems the Ikea production team took some cues from this classic Mercedes Benz barrel roll fake. A team of nervous scientists working furiously toward a singular moment. An accomplished daredevil willing to risk life and limb for the sake of science and adventure. This one really goes over the top (!) in terms of cinematography and soundtrack. I like this version, which includes a wink at the end.



Tangent; If you missed the Bungee Physics Extravaganza the was born of my Victoria Falls leap. just click that link.

Tuesday, June 27, 2017

PGS: Give your students quantum numbers

Visitors to my classroom sometimes compliment me on its level of organization. I think my classroom is often in a state of high entropy, but such is the eye of the beholder. I confess some compulsion toward organization: there is enough randomness built into running a lab class in high school. If not held back a little bit, it can easily cascade out of control.

My school opened in 1963 and continues to operate in the buildings it opened with. My classroom is also my lab; it's a "shoebox" (no islands or peninsulas). It has electrical outlets that drop down from the ceiling. It has three functional sinks, a few gas jets, and more outlets along a long, narrow countertop. Below the countertop and along the back wall, there is classroom storage. I have a demonstration lab bench in the front of the classroom, a flatscreen. There are Ethernet jacks and electrical outlets along a recently installed racetrack along two walls. And there is a wireless access point on the ceiling in a corner.

The bulk of the floor space is occupied by 18 two-student tables and 36 chairs. Their positions and orientations can be modified at any time.

The default classroom instruction (sage on the stage) mode is three columns of six tables. We used to limit lab courses to 32 students, so two tables in the back would be unoccupied. This arrangement is neither innovative nor creative; it could be disparaged with the harshest aspersion known in education: "traditional".
One of my early-career epiphanies was that students shoulder much better stewardship of lab apparatus when each item of apparatus is labeled specifically for use by individual lab groups. So nearly every item in my lab carries some kind of group-specific identification. I use letters A through H. It's awkward when Group C is found using Group E's apparatus. And when something goes wrong/missing, the chain of custody is readily apparent. No group hopes to end up on the "Phyz Foul" list maintained on the whiteboard in the front of the classroom.
I develop a seating chart very early in the school year based on student seating preferences (front/middle/back). Thereafter, we do a seating chart shuffle every 20 school days, with an emphasis on performance-based heterogeneity and individual choice in mind.

In recent years, I've had occasion to collect and sort student work for later return to the students. I'm a big fan of milk-crate file boxes, so they're what I use for the temporary storage. With hanging files and manila folders, I could create files for each student labeled by last names. But that requires alphabetical sorting of each assignment and wastes manila folders at a high rate.

I realized that my seating chart serves as a very useful organizational / classification scheme. Each seat within each group could be assigned a number, 1–4. Add to that the period number, and each student on the year's roster has a unique PGS (period, group, seat) address during any given seating chart. Student 5F2 is in 5th period, group F, seat 2.
Students write their PGS code on work they turn in. Sorting the work is a breeze. File crates with hanging files and manila folders are useful in perpetuity.

For computer-based activities (PhET sims, etc.), students 1 and 2 can turn around so that everybody's working around the back table. If the computer (we use laptops) is positioned correctly, all students can reach it.

For more sprawling labs, students 1 and 2 can move to the opposite side of their table, which can be pushed (lifted) to adjoin the 3-4 table.
If the orientation of the letters and numbers (right to left, etc.) looks backward somehow, that's intentional. The orientations are designed to be logical in the student perspective.

This is a simple organizational tool that I find useful in my instruction. It's a small thing. But sometimes it's the small things that can make a big difference in day-to-day operations.

Sunday, June 25, 2017

In the Skeptic Zone with The Exploratorium's Paul Doherty

And Richard Saunders and Eugenie Scott.

Australian skeptic podcaster, personality, origami artist, and host of The Skeptic Zone Podcast, Richard Saunders crossed the Pacific to visit America. Here in Northern California, he visited Paul Doherty at the Exploratorium and Eugenie Scott at her backyard beehive.

Our friend, Paul Doherty, was literally in his element, and that comes across nicely. Eugenie Scott is noted for her work with the National Center for Science Education, a friend to any teacher hoping to teach the science of evolution or climate change in challenging environments.

Richard Saunders has long been on the front lines of skepticism and critical thinking. My students know him for his ingenious take-down of the Australian distributor of Power Balance bracelets.

All three of these people are heroes and inspirations to me.

In any case, have a listen!

Skeptic Zone, Episode #453 - 25.June.2017

Monday, June 19, 2017

Total Eclipse of the Sun Part 2

I won't have to worry about changing film for 2017 eclipse
In my last post, I shared my first total eclipse of the Sun. I hoped to spur into action people who were on the fence about going. Hopefully you have started investigating the logistics about how to place yourself under the path of totality on August 21st. In this post, I will share my advice for making the most out of the experience and my 1998 trip to Aruba to witness my second total eclipse. I am in no way an experienced eclipse chaser or an expert on eclipse observation and photography. My hope is to motivate you to do further research into the various aspects of total eclipse viewing that I will raise. All of the pictures and video in this post were taken by myself in Aruba.

There are several considerations for selecting your observation spot. For me, the most important is the prospect for clear weather. When looking at various choices available to you, compare the probability for clear skies for the day and time of the eclipse. Another important factor is the length of the eclipse, but for me that is secondary. A total eclipse is one of those experiences for which the perception of the passage of time is highly altered. I was lucky to see one of the longest eclipses, 7 minutes of totality in 1991. The eclipse in Aruba was about half that duration at my location. Both seemed to last the same amount of time. I would select a location based on weather and then get close to the center line to maximize the duration. That is why you will find me in Madras, Oregon (2:00 min totality) on August 21st instead of Nashville, Tennessee (2:40 min totality). Do some research, there are many online sources for eclipse weather information. This chart shows the average cloud cover across the eclipse path.

If you are planning on photographing the total eclipse, my advice is do what I say, not what I did. I spent too much time fooling with my equipment in both of the eclipses I observed. For August 21st, I plan to snap a few pictures through my 80 mm refractor. I will not try and capture all the various phenomena associated with totality like Bailey’s Beads, the Diamond Ring, prominences, and the extent of the corona. My goal will be to have a nice personal souvenir, not to try and compete with the more experienced, skilled, and equipped eclipse photographers. They will share their results online. You can increase your chances of getting a good photograph by practicing on the Moon when it is near full. This will give you a good idea of what exposure to use and how large the image will be for your optics. I also plan on setting up my video camera to record the crowd, sky, and sound during the eclipse like I did in Aruba. I will not need to monitor it during totality. This will free me to observe as much of totality as possible using just my eyes and my 10 x 30 image stabilized Canon binoculars.


Observing a total eclipse without a solar filter is completely safe. It is the partial eclipse phase on either end of totality that is risky. It is not safe to look at any part of the Sun's surface (photosphere) for more than an instant. We have a natural instinct that prevents us from doing this. However, if you were determined to blind yourself, you could do it on any sunny day. What makes a partial eclipse a problem is our instinct is overridden by our curiosity. Furthermore, when it is a very thin crescent, the lower brightness can allow a person to look long enough to cause damage before wanting to look away. You won't notice the damage as it occurs, the eye does not feel pain. That is why it is important to have a variety of safe ways available to view the partial eclipse. Pinhole viewers, eclipse glasses, supervised telescopes/binoculars with solar filters firmly attached over the objective, and supervised telescopes/binoculars projecting images on screens are all good choices. A Sunspotter is one of the best tools if you have $430 to spend.

If you are lucky enough to be in the path of totality, you can look directly at the totally eclipsed Sun. You are now viewing the corona and chromosphere which are similar in brightness to a full moon. It is stunning to see in a telescope or binoculars but if you are looking when the eclipse ends, you will most likely damage your eye. It is important to know the duration of the eclipse at your location and stop looking about 30 seconds before it is predicted to end.

Just before the total eclipse and immediately after, there are two phenomena known as Baily’s Beads and the Diamond Ring. These occur when the only part of the photosphere that is visible is seen through valleys on the limb of the Moon. Baily’s Beads occurs when there is a crescent of valleys that the photosphere is peaking through. The Diamond Ring occurs when there is one last piece of photosphere visible. It forms the diamond and the corona forms the ring. Although many people have done it, including myself, it is not safe to look at even this last small part of the photosphere. I recommend looking at the Diamond Ring using a safe solar filter. That way when the total eclipse starts, your eyes will be more dark adapted so you can see more structure in the corona. More importantly, you will still be able to see when it is time to drive home! Most people that have seen the Diamond Ring directly saw it at the end of the eclipse. That is when I have seen it. It is the signal to look away from the Sun. It would be prudent to do so before the Diamond Ring but in my experience, most people don’t. The key is the duration of your look. I will not attempt to estimate a safe duration. I will only say it should be less than the time it takes to burn an image of it on your retina.

Gia on the beach
Dan diving a shipwreck
The total eclipse my wife and I saw in Aruba was on February 26, 1998. I was teaching science at Los Gatos High School and this was before we had a week break in February. I pitched the trip as a science expedition to my principal and he approved my one week absence. I arranged for our best substitute teacher to take all my classes for the entire week and met with him beforehand. The Exploratorium was going to show the eclipse live from Aruba on something called the Internet. I showed the sub how to connect my CRT TV to my Mac and how to log in to the Exploratorium website using an application called Netscape. If things went well, one of my classes would be able to see the total eclipse live, others would see the partial phases on the Exploratorium’s broadcast.

Warned to not be under sleeping iguanas
The eclipse stamp shows Aruba was prepared
Aruba is a Caribbean island near the coast of Venezuela. It is very dry and the weather prospects were excellent. The southern tip of the island was closest to the center line, but we elected to watch from the beach outside our hotel. We gave up 25 extra seconds of totality but also a long bus ride into an uninhabited area. People started setting up for the eclipse a couple of hours before totality. I was surprised by how many people asked what was going on. They just happened to schedule a vacation in the path of a total eclipse. What luck!
This may be the most laid-back place to view a total eclipse
I took a few shots of the partial phases through my 80 mm refractor with a solar filter. Just before totality I wedged my video camera in a palm tree and aimed it toward my psoition and the ocean. I hoped to catch the Moon’s shadow approaching. I sat on the beach and awaited a spectacle that must be seen in person to appreciate. Someone near me was watching the time and shouted out fairly accurate and helpful time estimates of second and third contact. After the diamond ring appeared I looked up and gazed in slack-jawed wonder. I then alternated viewing through the refractor and naked eye views. I took a lot of pictures, bracketing the exposure I had determined would be the best for the corona. I took a few very short ones to try and show the chromosphere and some long ones to try and get Jupiter. I also hoped to get the Diamond Ring. My plan was to look for it visually and take the shot without looking in the camera viewfinder. It turned out pretty well with maybe a bit too much diamond, not enough ring.
No large prominences :(
Long exposure shows Jupiter and moons but smeared Moon
Picture of Diamond Ring worth risking equipment, but not eyeball
It did not get very dark during the total phase as you can see in the videos. I did not need a flashlight to see the exposure settings on my camera. It was interesting to hear all the noises during the total eclipse. People honked their horns, yelled, and set of firecrackers, much different than the sounds on a cruise ship. I also noticed birds flying back to their roosts prior to totality. There were a good number of people scattered along the beach but it wasn’t crowded. I am looking forward to seeing what it is like to observe a total eclipse in the large crowd I expect will be on the football field at Madras High School.


Beat this misaddressed postcard back
The photosphere has its charms too
After I returned, I learned my students were able to watch the first total eclipse ever broadcast live on the Internet. The live stream would not load all morning but my substitute kept trying and also let the students try. One of the best students to ever come through Los Gatos High gave it a try and got it working just before second contact. The drama added to their experience.

In my next post I will give details about the eclipse event conducted by Lowell Observatory at Madras High School in Oregon. I will describe my plans for contributing to this event and some ideas for activities you can do to enhance your experience on August 21st.


Thursday, June 15, 2017

Total Eclipse of the Sun Part 1

Not easy to get a good picture on a ship
This is the first of a series of posts I will write about the upcoming total eclipse of the Sun that will be visible this year in a narrow swath that crosses the entire continental United States on Monday, August 21. In preparation for this eclipse, I dug out everything I had saved from the trip to see my first total eclipse of the Sun in July of 1991. At that time I was completing the physical science teaching credential program at San Jose State. My wife Gia and I took a cruise out of Los Angeles on Royal Caribbean's Viking Serenade. We sailed to Cabo San Lucas and then observed the eclipse from the Sea of Cortez. On board the ship was a long list of scientists that gave fascinating lectures before and after the big event. Among these were archaeoastronomer Ed Krupp from Griffith Observatory, cosmologist David Schramm from the University of Chicago, astronomer Donald Osterbrock from Lick Observatory, meteorologist James Sadler from the University of Hawaii, and geologist, astronaut, and senator Harrison Schmitt.
Brought along my Space Shots trading card for Schmitt to sign

UCLA Extension offered a class during the cruise, Astronomy 425.84. I signed up for the college units and because I would be going to all the lectures anyway. As part of the class I was required to write a paper about my experience. While going through my eclipse momentos, I found my paper written in cursive on Royal Caribbean stationary. Since I got a solid A on it, I thought I would share it. Below is the text from my paper exactly as I wrote it except for a few corrections suggested by the spellchecker and a few added commas. The only additions are the pictures, videos, and their captions.

Seven Minutes of Spectacle, a Lifetime of Wonder

The Sun is the same in a relative way but you're older
A total solar eclipse is the most spectacular natural phenomenon that can be observed without mortal danger. People have traversed the globe to witness them even after the advent of coronagraphs. Although total solar eclipses have little scientific value, they can have great value to the individuals that witness them. A renewed curiosity in all natural phenomena will surely occur in everyone who views a total solar eclipse. This paper will describe my own observations and reactions as well as some of the people I have talked with.

A sense of apprehension pervaded the ship on the morning of the eclipse. The towering cumulonimbus clouds that surrounded us looked threatening. However, those of us who attended the Pacific weather lecture knew that they would stay over the mainland and the peninsula. It was the high cirrus clouds that caused the most worry. They covered the sun most of the morning up to the first contact. Just before first contact the ship seemed to pull out from under them, revealing the Sun. I was observing through my 20 x 80 binoculars and was able to see that the Sun was finally clear. I detected first contact at 11:29 and 14 seconds, seeing it well before people using the solar screen viewers. Even though I had a compass and was paying attention to my orientation, first contact occurred almost 90 degrees from the part of the limb I was concentrating on!

The excitement grew as we monitored the moon’s progress across the solar disk using the binoculars, view screens, and the viewfinder of the video camera. It soon became clear that the center of the moon was going straight towards the center of the Sun’s disk. This was not going to be just a partial eclipse!

Shadow bands from another eclipse (Wolfgang Strickland)
A noticeable dimming of the ambient light occurred about 20 minutes before totality. Sunglasses were no longer necessary and the air temperature grew cooler. This darkening progressed until shadows were barely visible. People’s attentions were drawn towards the west, looking for the approach of the moon’s shadow. I turned my attention to a white sheet laid out next to my position when someone exclaimed “shadow bands!” They were very evident against the sheet for about 10 seconds before totality. They were stripes of dark and light bands about 2-3 inches across. At first they appeared to move towards the east but then they started to oscillate. I believe this was an optical illusion.

Now it was time for the main event. I removed the filters from my binoculars and video camera just as the crowd shouted. I looked up to see the most beautiful and eerie sight. It looked like no picture I have ever seen. I now know why people travel so far to see total eclipses, it is the only way to know what one looks like! The corona extended for about two moon diameters with two streamers approaching three and one half. Detailed structure could be seen throughout the corona. No photograph could show this wide range of lighting and structure. After my eyes had dark adapted some, I looked to see what planets and stars were visible. I quickly made out Venus, Jupiter, Mercury, Regulus, Canopus, Betelgeuse, and Sirius. I did not see Mars, Castor, or Pollux but the incredible view of the eclipsed Sun didn’t make it worth looking for them!

Eclipse with prominences drawn by
dinner table partner Darly, age 5

The biggest surprise for me was the obvious naked-eye prominences. There was one large one to the north and several moderate size ones to the south. They had a beautiful pink-orange color. Through the 20 x 80 binoculars the large prominence showed a hook structure. With all the different factors that combined to make this a great eclipse I think being near sunspot maximum provided the best show. I will never forget the appearances of the prominences.

I was also surprised by how bright it was during the eclipse. I had been told to have a flashlight ready because it would be dark. It never got darker than sunset usually is. I believe this was due to the brighter than usual corona and the reflected light off the cumulonimbus clouds which nearly surrounded us. This probably explains why we didn’t see the approach or departure of the moon’s shadow.


I kept hoping Lurch would come out with a tray of drinks.
The reappearance of the diamond ring signaled third contact and the end of totality. Its beauty tempered the disappointment of our experience coming to an end. I looked around and observed that everyone else was as emotionally drained as I felt. They looked happy and serene. I stayed on deck until just after fourth contact, filming the entire sequence on video. A new sense of camaraderie had developed among the people who had just shared this experience. We exchanged addresses so that we can share our pictures at a later date. The actor John Astin was near us (Addams Family, Night Court) and I talked with him for awhile, never mentioning his celebrity status. The experience of a total eclipse had humbled us all.


Since the eclipse I have noticed a heightened interest in science and astronomy among the passengers. Our nightly stargazing is better attended and people are demonstrating an intense desire to learn more. People ask probing questions and make keen observations. A cheer arose in the dining room when those seated near the window observed the green flash. People left their tables and looked when the 31-hour moon was spotted. All of the lectures that I have attended since the 11th have been standing room only. I hope this renewed sense of curiosity in people is permanent and contagious! As a science teacher, it is great to see people respond to natural phenomena with wonder and excitement. I hope I can use the pictures and videos as well as my personal experience to convey this to my students. I hope it doesn’t require a total eclipse to spark people’s curiosity about our world and the universe!
Lens flare in long exposure shows chromosphere

Dan Burns – July, 1991

In the next eclipse post I will share my experience observing the 1998 total eclipse of the Sun in Aruba. I will offer some advice for observing the eclipse this year. In the meantime, make your travel plans. I already have my substitute teacher lined up! Here is a one-stop place for information about this eclipse:

https://www.astrosociety.org/education/2017-solar-eclipse-information-resources/

I will be helping to put on this event in Madras, Oregon, maybe I will see you there:

https://www.lowellsolareclipse.com/