New AP Physics C Mechanics Book Release

You may have noticed it’s been a LONG time since I’ve updated this physics education blog.  More likely you haven’t noticed, because it’s been a LONG time since I’ve updated this blog.  This hasn’t been due to a lack of topics to write about, but rather, it’s been a conscious choice to plow full steam ahead on a project that began in June of 2013 and that I’m thrilled to announce is now available, The AP Physics C Companion: Mechanics.  But first, some background.

Traditional AP Physics C

As a teacher of calculus based physics (AP Physics C – Mechanics and AP Physics C – Electricity and Magnetism), I’m faced with a very unique challenge in those courses.  I typically enjoy classes of bright, motivated students who are preparing for careers in engineering, science, medicine, and other technically challenging fields.  And I love teaching the content of these courses — the level of technical challenge keeps me motivated, and I love the highly mathematical nature of the course.

In teaching the class, however, what I found is a very aggressive schedule to fit both courses into the school year, and my students are co-enrolled in calculus (which means they typically need to solve calculus problems in physics before they’ve been introduced to the calculus in their mathematics classes).  Further, teaching in a traditional style, I found that most topics fit fairly well into our 42-minute periods.  Students come in to class, begin with a warm-up question tied to the previous day’s topic, which we spend a few minutes reviewing, then I have time to present a single topic with an example or two each day.  If we don’t take any breaks, and throw in a quiz or test every couple weeks, as well as some fairly straightforward lab activities, we JUST barely get through all of our material in time for the May AP exams.

What I especially enjoy about this class and this method of teaching, however, is the face-to-face time with the kids during the daily lessons.  Class sizes for AP Physics C is typically small enough that we have a very informal style that is warm and inviting, yet challenging for all.  The students enjoy the class, taking notes from their seats each day, and doing book problems and old AP problems for homework in the evenings.  And our AP scores each year are solid.

In September of 2011, however, I decided to try something different.  I wanted to get away from the teacher-centric model, as I realized that I was the hardest working person in the classroom.  This contrasted with the best teaching advice I ever received, when our assistant principal and my mentor explained that I should strive to “Look like the laziest teacher in the building while the students are in the classroom, and the hardest working teacher in the building the moment they leave.”  What he meant was students should be doing the work in the classroom, especially as I continuously espoused my belief that physics is something you do, not something you know.  Although the students were doing OK in their passive roles as notetakers, this was a credit to the strength of these students, not my teaching.

A New AP Physics C Methodology

Instead, I began to imagine a classroom in which students directed their own learning, building lifelong learning skills that would serve them well outside the narrow discipline of future physics courses.  With the blessings of our administration, I undertook a giant experiment in the classroom.  We went through the year with the goal of having zero teacher lectures.  Instead, I completely “flipped” the classroom.  Students were expected to watch video mini-lessons on topics outside of class, as well as read the textbook and take notes, saving classroom time for group discussions and problem solving, hands-on lab activities, and deeper dives into topics of interest.

I ended up going back to traditional lectures on two topics — Gauss’s Law and the Biot-Savart Law, but for the most part the class ran independently.  I built up “packets” of assignments, practice problems, labs and activities for each unit, and students worked at their own pace (within reason) through each unit.  Unit exams were given when students said they were ready, with multiple re-take opportunities.  This evolved into a self-paced course, and at the end of the year, I found AP scores were significantly higher than in past years, which in retrospect shouldn’t have been surprising.  Teaching in this more hands-off manner is very uncomfortable, however.  I “feel” like I’m doing a great job when I’m working hard, presenting great lectures, and interacting with the students.  Stepping back and watching the students work, only getting involved to ask the occasional question or provide some basic clarification and support is extremely challenging.  Given the results, though, I tried it again the following year.  Same result!

These classes were regularly polled for feedback on the course.  General observations were that many students felt more intimidated and lost at the beginning of the course.  As well, there were several points throughout the year in which the students felt quite frustrated.  Polls at the end of the year, however, indicated students felt very confident in their self-teaching abilities, their ability to work through challenges they initially thought impossible, and their comfort level with their preparation for future studies.  The most common opportunity they identified for improvement — learning how to read the textbook.

In an effort to address this, I’ve implemented a variety of changes in my classroom.  First off, we take some time at the beginning of the year and again after mid-terms to talk about and practice strategies for reading a technical text.  We also take some time to talk about how to actively use the video lessons and example problems so that study time is efficient and productive.

The AP Physics C Companion: Mechanics

AP Physics C Companion: Mechanics

Finally, I started work on a “companion” text to the AP Physics C curriculum, focused on distilling down the key points from the text and illustrating them with a variety of applications.  Not really a review book (though it could be used in that sense), but rather a cleaned-up version of instructor notes for the course that could be applicable to any calculus-based mechanics course.  A large focus of the book is trading off technical complexity for illustrated application of concepts, including justifications for problem solving steps in the problems themselves, and well-documented problem solutions.

I’ve been using the notes and draft chapters of this book for several years in my classes, which has allowed me a “test run” of various sections and the opportunity to see what works with students, and what needs further revision.  The final result, I’m excited to say, is now available as “The AP Physics C Companion: Mechanics.”  It will first be available in black and white print editions from APlusPhysics.com and Amazon, as well as a full-color PDF edition on APlusPhysics.com.  Shortly thereafter, print editions (both color and black and white) will be available from any retailer, including Amazon and Barnes and Noble.  Finally, bulk purchases will be available directly from sales@sillybeagle.com (Silly Beagle Productions) at substantial discounts.

Where’s the E&M Book?

I’ve already been asked repeatedly if there’s an E&M version planned.  The answer is rather convoluted, however.  The E&M version is half done — the draft is complete as part of my class work and has been for more than a year.  I haven’t typeset it yet, however (probably a 6-12 month project), or worked on the graphics for a few reasons.  First, it is a huge investment of time to do so, which puts other projects on the back burner.  Second, the market for such a book could be pretty small.  As only 27,000 students took the AP Physics C: E&M exam last year, that’s a very limited market to cater to.  Though the book would be appropriate for an introductory calculus-based E&M course, a very significant portion of students taking the E&M exam would have to purchase and use the book in order to recuperate the costs involved in putting out the book (which are substantial).  As most any science author will tell you, there’s not much profit to be made in writing these types of books, and margins are mighty slim.  It’s a labor of love because you want to help students (yours and others).  I’m already pushing the limits of ‘wise decisions’ in marketing a book to the AP-C Mechanics market (53K test takers last year), and hoping it at least breaks even.

Before making any commitments to an E&M version, I want to obtain feedback from the mechanics version — are students and instructors finding it helpful, what is a reasonable percentage of the market to anticipate, would it at least break even, and how is the new format received (fewer pages, larger format and type, color vs. B&W, etc.)  Given all that, I imagine it’s probably likely at some point I’ll get to work on it (after every book I tend to think I’m done, then eventually change my mind and start on another one).  However, it feels good to “fool myself” for awhile and pretend I’m done while I work on updating the APlusPhysics site, continue work on instructional videos, and perhaps get to bed a little earlier in the evenings.

For now, however, I’m excited to announce the release of The AP Physics C Companion: Mechanics.  Hope you enjoy it as much as I enjoyed putting it together!

*AP and Advanced Placement Program are registered trademarks of the College Board, which does not sponsor or endorse this product.

AP Physics 1 Essentials — The Mystery Third Edition

A few years ago I put together a review/guide book for the AP Physics 1 course the College Board recently released.  AP Physics 1 EssentialsThe project was started around 2009, but took several years to complete as the scope and direction of the College Board’s AP Physics 1 course continued to evolve, as more and more information about the course was released, modified, re-released, etc.  It has done fairly well, and after the release of the first exam, a second edition was released, which included minor edits, modifications, and rephrasings in the main text, but also incorporated a significant number of more challenging questions in the appendix, though many of them remain numerically focused.

The Goal

The goal of this book was never to be a “sole source to success in AP Physics 1.”  The AP Physics 1 course is a VERY challenging introductory physics course, which requires a strong foundation in fundamental physics principles, logical problem solving, and transfer of basic concepts to new and unique situations.  In my humble opinion, building skills of this sort requires more than a review book.  It requires more than videos.  It requires extensive hands-on work with applications utilizing the concepts, individual and group problem solving, debate, discussion, and research.  It’s a very high level of expectation for what has been largely touted as an introductory physics course.  For many, AP Physics 1 will be the only physics course they take.  I am concerned that the course offers only a subset of what I would like to see in a general survey course of physics.  Though it covers basic circuits, it is light on electrostatics.  Though it covers mechanical waves, it doesn’t touch electromagnetic waves, optics, or modern physics.  If these were the only topics my students were introduced to in their only physics course, I feel I would be doing them a disservice, and not providing them an opportunity to see more of the breadth and beauty of the field I so love and enjoy.

The AP1 Essentials book, as written, was designed as the book I’d want to use with my students.  The book which I’d ask them to read outside of class (coupled with video mini-lessons) so that when they arrived in class, they’d have some level of exposure to the basic material allowing us to use our class time more efficiently for those deeper explorations into the topics under study.

Public Response

Public response to the book has been strongly bimodal.  Overall reviews are very positive (4.5/5 stars on Amazon.com), with the primary criticisms and 1-star reviews focusing on the book utilizing too much numerical problem solving, and focusing on basic problems that are “too easy” compared to the actual AP 1 test questions.  These are VERY valid criticisms, and I agree with them.  However, in the context in which the book is intended to be used, these criticisms are inconsistent with the book’s purpose.

AP Physics 1 Concerns

A grader of this year’s AP Physics 1 exam recently stated that he was surprised to learn that “not including the date, birth date and school code, a student could have made a perfect score on the whole exam without writing down a single number.”  calculatorI find this extremely troubling.  I am in favor of questions that test understanding, but I also believe that many physics students who go on to successful careers in STEM fields learn by first mastering the calculations, mathematics, and numeracy of problems, and over time build deeper conceptual understandings as they recognize patterns in their answers.  There is a place for these conceptual and symbolic problem solving exercises in AP Physics 1 and on the AP Physics 1 exam, but there is also a significant place for what I’ll call physics numeracy for lack of a better term — traditional problem solving that involves recognizing appropriate relationships, manipulation equations, finding a numerical answer, and verifying that numerical answer makes some sort of physical sense.

Further, I strongly believe that the College Board’s vision for the AP program should focus on providing opportunities for high school students to earn college credit consistent with the courses offered by most colleges.  More simply, the AP courses should strive to mimic what colleges are offering and testing in their corresponding courses.  In the case of AP Physics 1, the College Board is attempting to lead the way in physics education reform.  Regardless of personal opinions on the direction of the AP Physics 1 curriculum and exam, which may very well be valid, a change of this sort shouldn’t be led by the AP program, but rather mirrored by the AP program as it becomes the norm at colleges and universities.

The Third Edition

Back in December, I started work on a third edition of the AP Physics 1 Essentials book, with the goal of migrating the book closer to style of the AP Physics 1 exam.  It’s now late June, and the third edition is well over half done.  I have no doubt if I continued on this course, I could have the third edition completed in time for the book to hit the shelves in late August.

The third edition, as currently being drafted, however, won’t see the light of day.  garbageSince I started this revision effort, I haven’t felt good about the work I’ve been doing.  Though I do believe I am making a book that is more closely aligned to the AP Physics 1 exam, I’m moving further and further away from the book I’d want to use with my AP Physics 1 students.  Regardless of what the College Board is asking for on the AP Physics 1 exam, I want my students to be best prepared for their future endeavors, which may include AP Physics 2, AP Physics C, and their ongoing academic courses in the sciences.  That will, most assuredly, require strong physics numeracy skills. And it will require students to learn how to learn independently.

Resolution

There is a place for physics modeling, for building understanding and for MANY of the ideals inherent in the AP Physics 1 curriculum.  But there’s also a place for the traditional course and problem solving skills.  This debate doesn’t have to be an either/or proposition.  There’s definitely room for a happy medium including aspects of both viewpoints.  Personally, however, I can’t continue work on a third edition of the AP Physics 1 book when in my heart I strongly feel I’m doing my students a disservice in their overall physics education and creating a lower-quality product, even if it means more one-star reviews and critiques that the book doesn’t match the AP 1 exam.  Maybe someday I’ll change my mind, but Friday afternoon I took all the changes to the third edition, zipped them up, copied them somewhere safe, and removed them from my computer.

I strongly believe there will be a 3rd edition of the AP Physics 1 book.  I see TONS of opportunities for improvement.  But the work I’ve been doing for the past six months to make the book more consistent with the AP 1 exam isn’t really an improvement, it’s an attempt to improve student scores on a test I believe has significant flaws, at the expense of other important skills.  If I’m honest with myself and focus on doing what is truly best for my kids, I want to see them continue to use the book as an introduction to the essential concepts of AP Physics 1, including significant algebraic manipulation and problem solving, and leaving more time in the classroom for application and hands-on activities.  I still feel the book is a great tool for students preparing for the AP 1 exam, and I’m going to keep significant numeric problem solving with basic concept application, and leave the deeper-dive and conceptual understanding questions for class time when the instructor is available to direct, guide, and differentiate as needed.

Addendum

This is not meant as an attack on the AP Physics 1 Curriculum, the design committee, the test writers, or any others.  I am honored to work in a profession where so many are so passionate about trying to do what’s best for their students and the field itself.  Sometimes we disagree on the path forward, and that’s OK.  And I could be wrong.  I often am.  I admire the effort and the vision so many have put into this work, and the feedback and support I’ve received and continue to receive for this book, both in praise and in criticism.

Which AP Physics Course Should I Take?

Considering an AP Physics course? Outstanding, but which course should you take? The College Board now offers four separate and distinct versions of AP Physics, each designed with very different content, styles, and levels of mathematical complexity.

Currently, the four physics courses offered are AP Physics 1, AP Physics 2, AP Physics C: Mechanics, and AP Physics C: Electricity and Magnetism. So let’s start by talking about the courses and what each has to offer.

Algebra-Based Courses

The new AP Physics 1 and 2 courses are both algebra-based courses, meaning no knowledge of calculus is required, though students should be comfortable with basic algebra and trigonometry. The exams for these courses were first offered in May of 2015, so the courses and the exams are still evolving through their infancy. Further, the AP Physics 1 and AP Physics 2 courses include a strong emphasis on conceptual understanding and critical thinking. Compared to traditional physics courses, these courses include a significant amount of reading and structured writing, experimental design, and critical thinking.

Though mathematical reasoning and problem-solving are required for success in the course, they aren’t emphasized as strongly as in traditional courses. The courses are centered around seven “big ideas in physics,” and many of the exam problems will test your ability to interpret and apply one or more of these ideas to a new and unique situation (sometimes referred to as a transfer task).

Like most introductory physics courses, both AP Physics 1 and AP Physics 2 include a strong lab component to help students develop proficiency in science practices which are crucial to success. The course as a whole focuses on the idea that physics is something you do, not just something you know.

The associated AP exams for these courses consist of two sections: a 90-minute multiple choice section and a 90-minute free response section. The multiple choice section consists of 50 to 55 questions with four answer choices per question. Unlike most multiple choice tests, however, certain questions may have multiple correct answers that need to be chosen to receive full credit.

The free response section consists of four or five questions. Typically one question will cover experimental design, one question will cover quantitative and qualitative problem solving and reasoning, and three questions are of the short answer variety. In addition, students are expected to articulate their answers with a paragraph-length response.

AP Physics 1

The AP Physics 1 course itself is designed as a first-year physics course. The bulk of the course centers around traditional Newtonian Mechanics, beginning with the study of motion (kinematics), forces (dynamics), work, energy, power, linear momentum, circular motion and rotation, gravity, and oscillations. In addition, AP Physics 1 also includes a brief introduction to mechanical waves, basic electrostatics, and simple electrical circuits.

AP Physics 2

AP Physics 2 is designed as a follow-up to AP Physics 1, utilizing the same course philosophy, but extending the content covered to include fluids, thermal physics, a deeper look at electrostatics and more complex electrical circuits, magnetism, optics, and modern physics.

Calculus-Based Courses

The two AP Physics C courses both incorporate calculus, so students should have calculus as a pre-requisite or co-requisite for the best possible experience. AP Physics C: Mechanics can be offered as a first-year physics course, though some schools offer both AP Physics C: Mechanics and AP Physics C: Electricity and Magnetism in the same year to students who have prior physics courses in their background.

Compared to AP Physics 1 and AP Physics 2, the AP Physics C courses follow a more traditional path with a stronger emphasis on quantitative problem solving. The level of calculus complexity is relatively light, with a strong focus on application of principles to various situations as opposed to the longer written explanations of the AP–1 and AP–2 courses.

AP Physics C: Mechanics

Similar to AP Physics 1, AP Physics C: Mechanics covers only traditional Newtonian Mechanics. Students study motion, forces, work, energy, power, linear momentum, angular momentum, circular motion, rotational motion, gravity, and oscillations. Compared to AP Physics 1, however, the C course incorporates a higher level of technical complexity, such as dealing with situations of a non-constant acceleration, incorporation of drag forces (such as air resistance), and calculations of rotational inertia.

Both of the AP-C exams consist of roughly 35 multiple choice questions given in a 45-minute interval, followed by three free response questions in a second 45-minute interval. The AP-C exams are typically given back to back on the same afternoon.

AP Physics C: Electricity & Magnetism

The AP Physics C: Electricity & Magnetism course is by far the most technically complex of the AP Physics courses. Beginning with electrostatics, the course includes a detailed look at charges, electric forces, electric fields, electric potential, and capacitors. These concepts are then applied to an analysis of electrical circuits, including circuits with multiple sources of potential difference, real and ideal batteries, and transient analyses of circuits which include capacitors.

From there, the course transitions into a look at magnetism, with a strong focus on the relationships between electricity and magnetism as Maxwell’s Equations are investigated. It’s typically in this section that students really begin to challenge themselves, applying fundamental relationships (and calculus skills) to problems of increasing sophistication and technical complexity. With the added knowledge of magnetism, inductors are also discussed and tied back into the analysis of electrical circuits.

As you can see from the course descriptions, both of the AP Physics C courses are quite limited in scope, allowing for a much deeper exploration of the fundamental relationships and their application to various problems and situations.

Long-Term Goals

So then, back to our original question – which AP Physics course should you take? The answer, as is so often the case in life, is that it depends. Students who are planning on a career in engineering or physics should definitely consider the calculus-based courses (AP Physics C). These courses are fundamental to future studies, and a majority of colleges and universities accept scores of 4 or 5 in these courses for credit (though many students choose to re-take these courses to further cement their understanding of the fundamental concepts and boost their freshman GPA).

AP 1 2 C Table 001

For students who aren’t planning on a career in engineering or physics, the AP Physics 1 / AP Physics 2 series might be a better answer if their school of choice accepts AP–1/2 credit, as AP Physics C could be “overkill” compared to future course requirements. The problem, however, is that the AP Physics 1 and AP Physics 2 courses are so new that many colleges don’t know how to deal with them, and as of the writing of this article, there aren’t many schools that provide college credit for strong scores on the exams, as the course content and philosophy often times don’t match up well with the college’s offerings. For this reason, students who are up for a challenge and enjoy problem solving may want to target the AP Physics C course, even if they aren’t planning on a career in engineering or physics. Many universities will give credit for a good score in AP Physics C as a general science credit.

To complicate matters, there are often times opportunities to take a sequence of these courses. In many high schools, AP Physics C is offered as a second-year physics course, with students taking on both the Mechanics and E&M courses in a single year. It’s a fast-paced course, but doable for those who have successfully passed an introductory physics course. For those taking physics for the first time, AP Physics C: Mechanics is a reasonable year-long endeavor. Some schools with extended class times offer both AP–1 and AP–2 in the same year, though this is a very aggressive undertaking.

Summarizing the Choices

To summarize as best I can in this nebulous time period, AP Physics C courses are traditionally for students heading toward physics and/or engineering related career paths, and require a pre-requisite or co-requisite in calculus. Definitely take AP-C Mechanics before AP-C E&M, though it is possible to do both in the same year, especially with some prior physics background. For students not taking calculus or not headed toward physics or engineering careers, AP Physics 1 is a great place to start, with AP Physics 2 a reasonable follow-up for those interested. The concern with these choices is the newness of the courses, and whether colleges and universities will give credit for a strong AP score. As always, discussing and planning out course selections with a guidance counselor in consultation with an admissions counselor is highly advised.

Strategies for Success

Regardless of which course(s) you choose, the AP Physics courses are challenging courses that require a level of independence and personal accountability to learn the material. These courses aren’t designed for “spoon feeding,” in which the instructor lectures, students listen, and everything works out. In order to truly understand the material and perform well on the culminating exam, you must engage in the class on a daily basis, struggle through the challenging problems, make mistakes again and again, and learn from them. Actively participate in classroom and lab activities and discussions, ask questions, but be prepared to search out your own answers. And don’t be afraid to take a step back every now and then and think about how what you’re learning applies to the course goals as a whole. Concept-mapping or outlining the topics in the course can be a terrific way to make connections you might not otherwise recognize.

And of course, you have tons of resources to help you. Beyond just your textbook (which I do recommend you actually open and actively read) and teacher, you’ll find outstanding video tutorials and Q&A forums like those at Educator.com, discussion and homework help communities, “cheat sheets,” and extra problems at APlusPhysics.com, and of course there are some great review and companion books available for these specific courses.

 

About the Author 

Dan Fullerton is the author of AP Physics 1 Essentials, AP Physics 2 Essentials, and the APlusPhysics.com website.  He is an AP Physics teacher at Irondequoit High School in Rochester, NY, and was named a New York State Master Physics Teacher in 2014.

 

AP and Advanced Placement Program are registered trademarks of the College Board, which does not sponsor or endorse this work.

Separating Wheat from Chaff #lewin #physicsed

Recently I replied to a post on the College Board’s AP Physics Teacher discussion forum, an act that always seems to be a dicey proposition.  A teacher had asked other AP physics teachers for instructional physics video recommendations.  I replied with links to one of my favorite video series, the MIT 8.xx introductory calculus-based physics series put together by Prof. Walter Lewin.

If you are unaware, Prof. Lewin’s lectures have been immensely popular and have been in many ways the “de facto” standard for online physics lectures.  His preparation was well thought out, his content coverage thorough, his demonstrations engaging, and his performances nearly flawless.

Recently, however, Dr. Lewin’s lectures have been pulled from the MIT website due to an investigation in which MIT determined that Lewin “had sexually harassed at least one student online.”  (link here).  You can still find versions on YouTube.

Following my post on the discussion forum, I received several responses from instructors stating that they would not recommend the videos any longer.  I briefly responded that the quality of the videos didn’t change, therefore even though Lewin may have been acting in appropriately personally, the videos were not affected and retain their educational value.

Several responses were quickly received, ranging from recommendations to use alternate videos to a response stating that posting materials associated with Lewin would be morally irresponsible.  Though I do understand the concerns, I think disappointment in the behavior of one of our “physics heroes” is clouding the collective judgment.

If referencing the works of scientists who have had personal ethical or moral failings is the “correct response,” we need to recognize how much great work must be thrown away.  It doesn’t take long to research the personal lives of Albert Einstein, Richard Feynman, Marie Curie, Edwin Schrodinger, or even Stephen Hawking to find well documented evidence of significant personal life scandals.  Why is it that referencing their works in the classroom isn’t morally irresponsible, but referencing Lewin’s is?

This same issue surfaces again and again outside just the scientific world.  Were Babe Ruth’s accomplishments less amazing (especially in relation to other baseball players of his time) knowing his personal behavior off the field?  Were Pete Rose’s 4,192 hits less valuable to his team because he was later found to have a gambling addiction?  Should the Cosby Show be banned from syndication due to the show’s star alleged indiscretions?  In working toward my teaching certification, my class studied a book by Bill Ayers, whose past actions could easy label him a domestic terrorist.  Despite his past, however, as a class we were able to explore and debate the philosophies he promoted in his book in a productive manner.  We even re-elected a sitting president who lied under oath AND engaged in significant sexual misconduct.

My point isn’t that any of these behaviors are anywhere close to acceptable, nor that we should excuse them.  Nothing could be farther from the truth.  My point, however, is that pulling Lewin’s videos punishes the many students who could benefit from them.  Severing ties with the author, closing the associated discussion forums, and similar actions appear reasonable.  Removing the good works done by this individual only makes a bad situation worse.

Finally, to say that using the works of a public figure discredited for personal indiscretions is “morally irresponsible,” when looked at in a wider view, just becomes silly.  How many library books must you pull from the shelves?  How many theories and inventions must be destroyed?  And where do you draw the line on what level of personal indiscretion warrants these actions?  Is it a felony?  A misdemeanor?  Last week I received my first traffic ticket for a broken taillight (which was fixed first thing the next morning) — does that invalidate what small contributions I’ve attempted to make to my field?

Let’s move back to reality.  A beloved and popular teacher allegedly screwed up.  Big time.  We’re disappointed, and we’re hurt.  One of our heroes fell.  I get it, and I’m hurt too.  But his mistakes don’t invalidate his 40+ years of excellent teaching.  Our world is just not that simple.