Friday, August 8, 2014

Comet 67P Size Comparisons

As the ESA Rosetta probe approached it's target, Comet 67P (67P/Churyumov–Gerasimenko), I was having a tough time grasping the scale of this object. 

In response to @ObservingSpace tweeting a picture of 67P, I suggested comparing it to major cities. 

I did the same to the ESA and Emily Lakdawalla, who blogs for The Planetary Society. 

There was no response. 

I knew there were others far more talented than me, but I decided to put something together. I grabbed some images of 67P from the ESA, an older one with a 2km scale and the latest one without, and, in PowerPoint, adjusted the images to match so that I would have a scale on the latest image. 

I then went to Google Maps and took a screenshot of a map of Manhattan with a 500m scale. Adjusting the scales to match, I had 67P superimposed on Central Park. 

I tweeted this including ESA and Emily Lakdawalla and also Phil Plait, with little response. 
I then tried DC and San Francisco. 

Turning my sites to Europe, since the mission is through the ESA, I thought of another big rock, Gibraltar, this time using Google Earth:

But then I hit upon an idea that strangely was more useful than reality: Star Trek. 

I remembered being fascinated by a website called Jeff Russell's STARSHIP DIMENSIONS at where spacecraft from Sci Fi were drawn to scale. 

I sized several Star Trek stations and ships and came up with this:
I tweeted again to the same audience, but at that time I noticed William Shatner was tweeting with the ESA, so I sent the photo to him and was excited to get a re-tweet (to his 1.9 million followers):
I have my phone set to send me a text every time I get favorited and retweeted on Twitter, so the rest of the day my phone was buzzing constantly.

A few other retweets shared the picture with an even wider audience, and the number of retweets of these and the original built up. 

Life is back to normal with only a trickle of notifications now. But it was exciting while it lasted. 

I have since made a few more comparisons and realized that a black background looks better. 

Here's the latest gallery:

Tuesday, June 10, 2014

How 97,000 AP Physics exams get scored

I was fortunate to be a reader this year for the AP Physics exams. In order to be considered, I had to have taught AP Physics for at least 3 years before filling in the application.  It took another four years to be invited to be a reader.

Readers spend just over a week at their reading location, with all travel and expenses paid by the College Board. This year's physics reading occurred in Kansas City, Missouri, at the same time as psychology and European History. 205 physics teachers from around the world came to grade over 90,000 exams.

New readers are called "Acorns" and are given an acorn logo on their name badge. While you might expect this to be an invitation for hazing, we were welcomed and treated quite nicely.  Name badges were required for entry into any of the reading areas to ensure security of test materials.

AP reader name badge with acorn indicating first-time reader

For seven consecutive days, we worked from 8:00 a.m. till 5:00 p.m. with an hour for lunch and two 15 minute breaks. There were varied activities scheduled most evenings including receptions, professional development sessions and workshops given by the College Board.

Behind the Scenes

Before the reading begins, there is a remarkable process by which all exams are transported from the individual schools to the College Board offices in New Jersey.  There, the exams are sorted, tagged and assembled into folders. Each folder contains 25 exams and a set of computer bubble-sheets, one for each question. Ten of these folders are packed into each of thousands of cardboard boxes and shipped to the respective reading locations which this year included Louisville, KY, Cincinnati, OH, Salt Lake City, UT and Kansas City, MO.

Each reader is assigned a specific question from one of the exams.  I was grading the second free response question on the AP Physics B exam, referred to as "B2".  There were an additional twelve readers assigned to my question as well as two "Table Leaders" who arrive prior to the readers to fine-tune the grading rubric along with the Chief Reader.

The first day of reading began with a welcome meeting giving general instructions and introducing the various table leaders. We then each followed our table leaders to our reading locations. The large conference rooms (think hotel ballroom) were split into individual question rooms by portable curtains. Our room had tables up front where boxes of exams were assembled and where packets were picked up and dropped off for grading.  On each side of these tables was a flip-chart for keeping a tally of number of folders each reader completed every session.  Table leaders occupied two additional tables facing the room and additional tables facing the table leaders each sat two readers.

We went through brief introductions and began training on our specific question. Sets of student responses were copied and distributed for us each to grade according to the rubric, after which we compared our scores on each of the four parts of the question. we discussed any discrepancies and continued with several sample packets and discussions to ensure that we were applying the rubric consistently with similar interpretation.

Following lunch, the reading began.

In addition to the physics teachers flown in from around the world, there was a local workforce hired to manage the flow of boxes and exams between rooms. They would open boxes and prepare the packets for pick-up by pulling the proper question scan sheet from a pocket in the back of the folder and place it in the  folder in front of the pack of exams. They would also perform quality control on the returned packets, ensuring the scan sheets were properly bubbled and all information was complete before re-packaging the boxes of exams to be moved to another room for another question to be graded.

The scoring process consisted of picking up a packet from the front of the room, returning to my desk, filling in my reader number on the edge of the folder to indicate that question 2 had been read, and bubbling in my reader number on the scan sheet. I then would work through the 25 exams, which are the actual packets the students wrote on during the test administration (I had thought these might have been scanned in and we'd be working from images), fairly and consistently applying the rubric and bubbling in the question 2 score on the scan sheet.  When complete, I'd bring the folder back to the return/quality control table, post a tally mark on the flip chart and grab another folder.

On the first day of the reading, every folder was dropped off with the table leader instead of at the return table, and the table leader would grade the same set of exams.  Any discrepancies of more than a point would be discussed.  Once we were getting the same scores, the remaining packets could be turned in to the return table. This grading quality control continued throughout the week with table leaders requesting packets at various times through the day. Each scan sheet contained two columns for grading, and the completed scan sheets were processed for statistical control, both to keep track of each reader's overall productivity as well as to identify any deviation from table leader scores on identical packets or from the rest of the group in terms of overall average scores on the question.  These statistics were examined daily and throughout the day by the reading leadership.


I kept track of my daily total for individual number of tests scored, while table leaders kept track of folders scored for each reading period.  By the third day of reading, the pace of scoring had reached a point where a typical reader could complete about ten packets per session.

I was surprised to see productivity continue to increase as much as it did over the first few days of reading. I was so excited about my numbers that I was tweeting them to followers and a former student took it on himself to graph my progress.


By the end of the reading, I had personally scored a total of 5,620 exams.


Grading the exams was a remarkable learning experience, both for the actual process as well as for the after-hours professional development and camaraderie with fellow physics teachers. But I also came away with several tips for students taking exams in the future:

  1. Read Directions:  So many students were likely approaching problems and drawing diagrams just the way they were taught by their teachers, but many of these approaches and drawings did not earn credit because they did not follow the clear directions stated in the problem. 
  2. Don't Bother Writing an Irrelevant Essay:  Students might think it is amusing to write long letters or fiction or complaints to the person grading the exam, but chances are your work will never be read.  I took 22.5 seconds on average to grade each exam, which included bubbling the scan sheet and walking the test to the front of the room.  I don't have time to read your essay, and if it is in the "justify" section, it'll just upset me if you waste my time. A brief display of your artistic talent, however, was appreciated on occasion, especially if you got the rest of the question right.
  3. Show Your Work: Many points were lost for "immaculate answers" or answers where the origin of the solution was unclear.  This isn't a test about getting the right number, it is a test about demonstrating knowledge of physics.
I hope I get the chance to return every year to repeat this experience. It certainly will make me a better teacher and I'll be better able to prepare my students to demonstrate their knowledge of physics.

Oh, and I also got a nifty new geeky physics tee shirt to commemorate the experience.

Disclaimer: Although I was paid by ETS for my participation in scoring AP exams, these opinions are my own and I am in no way authorized to represent the opinions of ETS. It is my understanding that none of the above discloses any proprietary information.

Friday, March 28, 2014

No, I won't just let it go

I'm fixing a hole where the rain gets in / and stops my mind from wandering / where it will go - Lennon/McCartney
If your job is repairing leaky roofs, you would not tolerate people who made a habit of attacking them with pick axes.

As I understand it, the human brain has a natural tendency to be leaky, letting in all sorts of nonsense. The methods we've developed over the past several hundred years of scientific investigation are the only ones proven to effectively separate the reasonable from the bunkum and allow us to patch the holes and keep the nonsense out.

In my role as a physics teacher, I have the opportunity to demonstrate that you can explore everyday phenomena through observation and analysis and discover the rules by which the universe operates. Things don't fall down because I tell you they do; instead, our experience demonstrates that they fall and our analysis tells us how they will accelerate. Newton's Law of Universal Gravitation is not important because it came from Newton, but because anybody can derive it given sufficient data and math skills, and because we can make reliable predictions about the motion of objects from it.

Pseudoscience, on the other hand, relies on unverified and unfalsifiable claims that go against everything we know about the world. Homeopathy relies on water molecules remembering where they've been (which they don't). Acupuncture relies on the flow of Qi (which is not detectable) through meridians (which have not been found). Energy bracelets release negative ions (they don't) that align your body's natural energy field (which doesn't exist). When tested in properly designed scientific studies, we find that these and other fantastic claims perform no better than placebo - and the better designed the study, the smaller any beneficial effect.
Some simple methods to identify questionable claims. 

But what's the harm? So what if you enjoy a palm reading or your daily gargle of coconut oil? Who cares if your uncle feels his power bracelet improves his golf game? What does it matter if your Facebook friends spend their weekends tracking Sasquatch in the woods of Vancouver? Why should it matter if Mayim Bialik refuses to vaccinate her kids?

There is financial harm. The incredible waste of money on sham treatments is vast and disturbing. Power Balance made enough in their scam to (temporarily) sponsor the LA Kings NBA arena. Purveyors of scam treatments cleverly advise that it may take more than one treatment or will recommend regular preventative treatments to maximize the money they can collect from their victims. Dowsers in California are currently collecting hundreds of dollars per visit to supposedly locate water for drought-stricken farmers.  And not to make a slippery slope argument, but the public acceptance of each pseudoscientific product encourages the creation of more scams.

There is medical harm. When people substitute sham treatments for proven ones, they fail to get the medical attention they need. Preventable diseases are on the rise due to unscientific fear of vaccines. And people are given false hope by sham practitioners. At the same time, beneficial products, such as Vitamin A fortified Golden Rice are delayed or blocked due to unscientific thinking.

But equally troubling is the long term intellectual harm that presents "magic" as a viable alternative to scientific understanding, threatening to roll back the progress we've made. In order to accept pseudoscience, you must reject science. Every false claim that is accepted without justification is another pick-axe hole in the roof that undoes the work that I dedicate every day to accomplish.

Wednesday, March 5, 2014

Science is not true

In the words of Indiana Jones: "If it's truth you're looking for, Dr. Tyree's philosophy class is right down the hall."

As I Understand It, science is not about discovering truth.  If we say it is, we run the continual risk of truth changing with each new discovery, and increased public misunderstanding and lack of trust in our scientific endeavors.  When people claim that Newton was proven wrong by Einstein, it belittles the incredible accomplishments of Newton and then sets the genius of Einstein up for failure when the next discovery is made.

Instead, we should promote the idea that science is all about development of increasingly useful models: Ones which are better at explaining the past and predicting the future.

As an analogy, my grandfather once told me that his first car was a Model A Ford.  Over the years, I've wondered about his car, so I found an old black and white picture of a Model A.  With this picture, I could see certain details and understand proportions of the car, but it only showed one side, so I had no good idea of the top, bottom or inside.  In order to better understand the car, I got a small scale model of the car.  It had working doors and you could open up the hood and trunk to see the engine.  The wheels turned and it provided a 360 degree view of the car.  This model was a lot more useful than the picture, but it did not prove the picture "wrong".  It also didn't tell me everything about my grandfather's experience.

So I tracked down a fully restored Model A.  Now, I could sit behind the wheel, drive the car and see how it handled around corners, smell the exhaust and experience the rattling of the steering wheel. It was the best guide yet to what my grandfather's car must have been like, but still, if I were to take a DNA sample of the leather in the seat, it would not match that of his original car.  It was a better model than the last one, but didn't prove the old ones "false" and neither was this model "true".  Instead, I had developed increasingly detailed models that were useful for different needs.

Our scientific endeavors are the same.
Improving models
of the atom

If we look at the history of atomic theory, we find a series of models of the atom.  J. J. Thomson's plum pudding model explained the presence of electrons, which Dalton's model did not.  Ernest Rutherford obtained data with his gold foil experiment that was not explained by the plum pudding model, so he developed the planetary model. Atomic spectrum were not consistent with the planetary model, so Neils Bohr developed an atomic model with electron shells, which better explained the spectra. Despite this "progress", we still use an old billiard ball model of atoms to explain thermodynamics and ideal gases.  Each model is useful for a different set of circumstances, yet we should not be so arrogant as to claim that even our current model is "true".

When some students in biology class feel that evolutionary theory contradicts their religious views, perhaps an understanding that evolution isn't "true" would help to ease their objections.  Instead, evolution provides us with an incredibly useful model.  It helps to explain the common properties of life on earth and allows us to predict where to find the next transitional fossil -- things that a six-day-creation model may not be entirely useful for. But just because it is useful doesn't make it true.

Another obvious risk to claiming scientific truth is the all too common case of groundbreaking discoveries that reshape our understanding. We should avoid the arrogance of thinking that what we understand today will be looked upon as anything more than quaint to scientists a hundred or a thousand or ten thousand years from now.  And yet, some of our models may still prove useful to our distant descendants.  Remember, we needed little more than 300 year old Newtonian mechanics to calculate the trajectories that would put humans on the moon.

At least that's How I Understand It.

Tuesday, March 4, 2014

What we can learn from Adam's bellybutton

Recently, Bill Nye, The Science Guy, accepted a challenge and debated Ken Ham, CEO of Answers in Genesis. The topic: "Is creation a viable model of origins in today's modern scientific era?"  Reviews of the debate generally award victory to the debater that shared the reviewer's point of view. This is not a review of that debate, but instead presents a point of view that may make the question moot and foster mutual interest in the conclusions of mainstream science, As I Understand It.

There was an old joke about an archaeologist who discovered the mummified remains of a male and female and claimed that he had found Adam and Eve.  How did he know?  Because they did not have bellybuttons.  The question of bellybuttons is actually one that Ken Ham has answered on his website, and he concludes that since they were never attached to an umbilical cord, they would not have the scar associated with one.

from Wikimedia Commons
Brueghel's Creation of Adam
A literal reading of Genesis provides few details and leaves many such questions open to interpretation. However, the details we are given tell of a single week of creation during which plants, land animals, sea creatures and flying birds as well as all the stars and galaxies in the universe were created each on a specific day.  Within the garden of Eden, the animals were paraded in front of Adam and given names and finally Eve was created from Adam's rib as a companion for him.  By exploring the subsequent genealogies in Genesis, these events can be traced to a time roughly six thousand years ago

However, discoveries of modern science point out some apparent difficulties of this account. 
from Wikimedia Commons
Map of Nearby Stars
Astrophysicists can accurately measure the distance to many stars, which range from as little as four light years away to more than thirteen billion . If we take the Genesis account literally, then the skies above Eden should have begun quite dark, with only our sun, moon and five nearby planets visible on the first night.  It would take a little over four years for the light of Proxima Centauri to make its debut in the night sky, as the light given off by that initial burst of fusion in the first week of creation finally completed its journey to Earth. By the end of the sixteenth year of creation, only an additional eight stars would be visible, and even today, we should be able to see no farther than the nearby arm of our Milky Way galaxy.

Clearly, this is not the case.  

NASA Image. Spitzer/GALEX
Helix Nebula
There is another issue with the stars.  Our catalog of heavenly objects includes stars at all stages of their life cycles.  Based on analysis of the light emitted from each star, we can understand the elemental composition of each sun and the nuclear reactions taking place within it. Based on the known rates of reaction, the age and remaining life of each star can be determined.  Some gas clouds are known stellar "nurseries" giving birth to new stars, while others are clearly the remnants of ancient stellar explosions.  How are we to reconcile stars at all stages of their billions-of-years life cycle with a six thousand year old universe?

If we were to take a Young Earth Creationist point of view, we would have to accept that the variety of stars created on the fourth day included some young, some old and some already exploded.  He must have provided a variety of objects representing the entire life cycle of stars, both ready for our enjoyment and available to our analysis.  Despite being only six thousand years old, the stars would tell a story of thirteen billion years of history. This story is written in the heavens.  And since we can see these objects, despite their great distance, then perhaps God also created the beams of light between the stars and Earth, so that they would be visible on that first evening, displaying the majesty of the night sky.

A similar argument could be made for the first plants.  There is no indication in Genesis that the first trees in Eden started as seeds and had to grow to their full height over decades.  On the contrary, we are provided an image of a full grown forest, likely with trees at all stages of their life cycles suddenly appearing. Would those that began their existence full-grown have no growth rings? Or, as we see with stars, would the tall trees contain a growth record for time that did not exist, with rings consistent to their growth?  I don't recall anything in Genesis that would contradict this conclusion.

That which is true for plants and stars would extend to animals.  Young and old created all at once, with the old bearing a non-existent history of time that never existed: Lions with full-grown manes and elephants with well-developed wrinkles as well as fish with growth rings on their scales and shellfish with well-developed layers of calcium carbonate.

Grand Canyon from NASA's Terra spacecraft
Similarly, glaciers would exist at the end of the first week with hundreds of thousands of years worth of annual growth layers, available for discovery by today's scientists studying ice cores.  Mountains would be created with billions of years of sedimentary layers consistent with an old Earth.  Grand canyons could be created within the first week without having to wait for meager rivers to carve their steep banks.  Using this logic, fossils could have been scattered throughout layers of rock telling an evolutionary story of life's origins consistent with the old appearance of the Earth.

And, yes, Adam would have a belly button.

Under this scenario, scientists could continue to look at all the converging lines of evidence and conclude that we live on a four and a half billion year old Earth that in the midst of a thirteen billion year old universe.  At the same time, creationists could look at a six thousand year old earth and universe, but study side by side with scientists to read the rich history written by the hand of God in the details He provided at creation.  In addition to reading the Word of God presented in the Bible, creationists could read the Word of God presented in the universe that tells a story of thirteen billion years of history, including our rich evolutionary past.

There doesn't need to be any conflict.

At least As I Understand It.

About me

A blog?  Sure, why not.  Welcome to "As I Understand It", where I'll ponder and pontificate on things scientific.  I'll challenge pseudoscience, promote critical thinking and hopefully avoid arrogance and ridicule (of myself and others) while doing so.

For the past ten years or so, I've been living my lottery dream.  In the years after getting my MBA and working as a marketing strategy consultant, I had the dream of winning the lottery and giving up business to become a high school physics teacher. I didn't win the lottery, but got to make the transition all the same, and despite the 3/4 salary cut, it was the best career decision I could have made.  I taught for four years in the suburbs of Denver, Colorado, and for the past seven have been doing so in Williamsburg, Virginia.

I majored in physics at Brandeis University, having always had a knack for math and science. I also was active in theater and spent every summer through high school and college working as a camp counselor.  Teaching high school physics ties these three loves together to some degree as I get to share my love of physics through the occasional "performance" of teaching, while having a positive influence on kids.

I've always been one to ask questions to understand the world around me.  If you've ever been on a group tour where there is someone at the front monopolizing the tour guide's time with question after question, that's me.  I'm THAT guy. It doesn't matter if it is a brewery tour or a Ranger program at the National Park, I can't help it but to ask questions.  Hopefully, through all that questioning, I've learned a thing or two, and I'm always looking to learn more.

So I'll be blogging about things "As I Understand It", and I hope to learn more along the way.

Please be kind.