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February 2019

Book Recommendation: Glass Universe


By Stacy Palen

A few weeks ago, Colin Inglefield wrote a guest post about his uses of trade books in the classroom. Over break, I finally had a chance to read Glass Universe by Dava Sobel, and I think this would make a great book to use in this context. The book is about the early years of the Harvard Observatory, and the women “computers” who worked there. I am considering using this text for Astro101 next fall.

There are several themes running through the book that might be used to guide discussion throughout the semester.

The first is the science and society angle; there’s a lot to talk about here, of course, about the role of women in science, and how the larger society’s norms decide who gets to play along in the sciences, and in what role. Then there’s the question of who gets the credit. In recent years, it has become increasingly well-known that Rosalind Franklin was robbed of recognition for her critical involvement in the discovery of DNA due to her gender. Sobel tells a parallel story in astronomy about Cecilia Payne-Gaposhkin, and her 1925 thesis that began a revolution in astronomy by discovering that stars have fundamentally different compositions than planets. Why is her name not as well-known as Chandrasekhar’s? That’s an opening point for a wide-ranging discussion about not only the role of women in science, but also general fairness (think of the recently renamed Hubble-Lemaitre Law).

The second is about the symbiotic connection between technology and science. (This is covered more directly in another trade book, Starlight Detectives by Alan Hirshfeld.) Hirshfeld convincingly argues that the revolution in photography created a corresponding revolution in science, because scientists were able to store objective data for the first time. This meant that multiple scientists could analyze the same data, and compare data points over time. Hirschfeld follows this thread through Henrietta Leavitt’s work on different types of variable stars, Annie Jump Cannon’s work on spectroscopy, and Cecilia Payne-Gaposhkin’s work on elemental abundances, and reveals why these discoveries could not have been made in Newton’s time, for example, the record-keeping ability that photography provides simply didn’t exist. Similarly, telescope technology was improving by leaps and bounds during this time, and internally consistent observations from both hemispheres became possible.

The third theme is about the role of private and public philanthropy in science. Most students are not aware of how science is funded today, nor how it has been funded in the past. The funding sources dictate, to some extent, what projects are pursued. At the Harvard Observatory during this time, Mary Ann Draper’s interests were decisive to the success of the observatory, and dictated to some extent the avenues of inquiry that were followed. There are benefits and drawbacks associated with privately funded science just as there are with publicly funded science. Deciding on the balance between the two funding sources is a current argument unfolding in the political sphere and in the larger society. This book helps illuminate the extent to which science in the past was dependent on the individual inclinations of wealthy donors. It’s for your students to decide whether they think the system has improved or not!

I’ll use this book for an experiment with book discussion groups in fall semester. I’ll let you know how it goes! Let me know if you decide to try something similar.

Reading Astronomy News: Updated Graphic of LIGO/Virgo Compact Binaries

By Stacy Palen

LIGO has been busy, and a newly released graphic summarizes many of the exciting discoveries the detector has made in concert with Virgo, its European counterpart.

Summary: Since 2015, the LIGO/Virgo collaboration has detected gravitational waves—ripples in spacetime caused by rapidly accelerating massive objects—from 10 stellar mass binary black hole mergers and one binary neutron star merger. Black holes and neutron stars are both forms of stellar remnants—the final stage of stellar evolution that a star enters when it has burned through its entire fuel supply. This graphic provides a great jumping off point for discussions about masses in the stellar graveyard.


1. Consider the final masses of the black hole mergers (larger blue circles). What is the smallest merged mass?

Answer: About 19 solar masses.


2. Consider the masses of black holes that have been detected in X-rays (EM Black Holes, in purple). What is the largest black hole mass that has been detected this way?

Answer: About 23 solar masses.


3. Estimate the average mass of the black holes that have been detected in X-rays.

Answer: About 10 solar masses.


4. Estimate the average mass of the black holes that have been detected in gravitational waves.

Answer: This average looks to be about 25 solar masses.


5. Astronomers make the claim that they are detecting a “new population of black holes” with gravitational waves---—that is, that the type of black holes they are detecting now are different than the ones they were detecting before. Based on your answers to questions one through four, explain why they would say this.

Answer: Even though the two groups of black holes overlap in mass, gravitational waves are detecting more massive black holes, on average, than were detected with X-rays in the past.


6. Compare the number of EM black holes to the number of black holes (before merging) discovered with LIGO/Virgo. How much has LIGO/Virgo contributed to the total sample of known black holes?

Answer: LIGO/Virgo has nearly doubled the number of black holes that have been observed.


7. Is it reasonable, then, to compare the two populations (the pre-merger black holes from the LIGO/Virgo data and the X-ray black holes)?

Answer: Yes, statistically speaking, we know of about the same number of objects in each case.


8. Consider the masses of Neutron stars (yellow). What is the largest neutron star mass that has been detected with light (EM)?

Answer: About 2.1 solar masses.


9. Consider the masses of Neutron stars (yellow). What is the average neutron star mass that has been detected with light (EM)?

Answer: About 1.5 solar masses


10. Theorists predict that we would not expect to observe neutron stars with masses above about 2.14 solar masses. Are these observations consistent with that prediction? What do you think astronomers are wondering about the post-merger object resulting from the merger of two neutron stars?

Answer: The neutron stars observed with light are consistent, but the outcome of the neutron star merger is a little bit too massive. As of this writing, astronomers are still trying to figure out the form of that post-merger object. It could be a black hole, a neutron star collapsing to form a black hole, or a stable neutron star. More data are needed!

How-to: Making Them Read

Using Trade Books in an Introductory Physics Course

By Colin Inglefield

I regularly teach PHYS 1010: Elementary Physics, at Weber State University. I didn’t choose the course name; at your school, it might also be called Conceptual Physics or Descriptive Physics. Regardless, it is a physics course with no math prerequisite (and therefore very little math content), primarily taken by students to fulfill a General Education breadth requirement.

There are challenges for the instructor. Some students have profound difficulty with proportional reasoning. Others sign up for the course after taking an Advanced Placement calculus-based physics course in high school, specifically because they are looking for an easy course.

The standard texts are approachable and conversational but might also seem patronizing—at least they do to me. Typically, there are between 90 and 100 students in my course. What to do?

I want the course to provide a meaningful experience for all students, while being faithful to the catalog description and General Education mission by presenting a survey of topics in physics and physical science.

I’ve made my course reading-intensive, because I believe in the transformative power of reading in any discipline. To get an A in my course, students have to, among other requirements, read two trade books.

The first trade book is something I choose for the whole class to read together. Most commonly, I’ve used American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer by Kai Bird and Martin Sherman. It’s an excellent book, a Pulitzer Prize winner that I recommend to anyone. It’s also a 600-page (not counting notes and references) serious work, arguably the most scholarly biography of Oppenheimer to date.

It’s not a book a lot of my students would choose on their own. It includes many physics topics we talk about in the class and is a great springboard for discussing issues of science-and-society in the 20th century.

We read it in sections and take one day every other week from class as “book club day” to discuss a section of the book. Before we discuss the book, students take a short-answer reading quiz. If they don’t pass the reading quiz, they can come meet with me and, by discussing the book with me, convince me that they’ve done the reading.

The only real requirement is that they read the book.

In the in-class discussions, a different group of students participates enthusiastically as compared to a “regular” day of class. The discussions have been some of my most memorable days in the classroom in my 20-year career.

Once the students get over the “Yes, we are going to read this whole thing” on the first day of class, a surprising number enjoy it and I get more positive than negative comments on my evaluations about the reading.

I had one student tell me that she started reading again because of my class.

Beyond the book we read together, in order to get an A, students need to read another trade book from a list of ~10 that I provide.

Here is the list of books that my students currently have to choose from:

  • Obsessive Genius: The Inner World of Marie Curie by Barbara Goldsmith
  • Plastic Fantastic: How the Biggest Fraud in Physics Shook the Scientific World by Eugenie Samuel Reich
  • Einstein: His Life and Universe by Walter Isaacson
  • The Strangest Man: The Hidden Life of Paul Dirac, Mystic of the Atom by Graham Farmelo
  • The Sky is not the Limit: Adventures of an Urban Astrophysicist by Neil DeGrasse Tyson
  • Crystal Fire: The Birth of the Information Age by Michael Riordan and Lillian Hoddeson
  • The Fallen Sky: An Intimate History of Shooting Stars by Christopher Cokinos
  • The Girls of Atomic City: The Untold Story of the Women Who Helped Win World War II by Denise Kiernan

Selections cover a variety of the people and issues from science in the last century and include a diverse group of authors and subjects. I break the class up into smaller groups for a separate book club discussion for each book in the last week of class.

Grades in my class are based on reaching benchmarks in various categories.

To get an A, a student needs to average 75% or better on my (physics) quizzes and tests and read both of the trade books. They get a B, but no better, if they don’t read the second book. They can’t do better than a C without doing the reading.

This all makes for a reasonable balance between making every student do something significant and giving every student a reasonable chance for a good grade.

The reading-intensive General Education science course has been as successful as anything I’ve tried in the classroom, in my obviously biased opinion. I love to talk about it with my colleagues.

Have you tried something similar with your students? Let us know in the comments!

How-to: Using Collective Marks

By Stacy Palen

In the last two posts, I explained what a rubric is and why they are useful. In the prior blog post, I explained how I use the first part of the rubric to guide me as I assess content knowledge in each question. In this post, I will explain how I use “collective marks” that apply to the whole assignment.

I first heard of collective marks in the sport of dressage. In this sport, the horse and rider complete a test consisting of 25-40 movements, which are each scored individually against a rigid standard of perfection. At the end of the test, the horse/rider pair are scored on four different and more subjective standards, such as “effectiveness of the rider” and “harmony.”

These collective marks might be loosely summarized as “sure, it was technically perfect, but did they make it look easy?”

I use collective marks for all the things that I care about that are not technically astronomy, such as spelling and grammar. But I also include here other features of the assignment that may appear in question after question, like units or neatness or labels on graphs.

It is tedious and time-consuming to keep writing “units” or “complete sentences” after every question. Grading these items collectively allows me to focus on the content in my first pass through the assignment. Then, I leaf through the pages again to recall my general impression of the “beauty” of their performance. I scale the collective marks to be worth about 10% of the student’s grade on the assignment.

For example, if the assignments are all worth 100 points:

For each assignment, 10 of the points will come from the “collective marks,” determined by the neatness, clarity, and other aspects of the work that are taken as a whole.

10: Excellent: You remembered to use units on every measurement or calculation. The assignment is neat and easy to read, with correct spelling and grammar and complete sentences! All mathematical steps are included, and all the graphs and tables have labels, with units! You are a rock star!

9: Very good: There are one or two minor flaws of spelling or grammar. However, all of the numbers have units.

8: Good: There are three or four minor flaws. I could find all of your work, but it was disorganized and a bit sloppy.

7: Fairly good: There is a major flaw (forgetting units or a label) or a combination of 5 or 6 minor flaws.

6: Satisfactory: There is a major flaw and several minor flaws.

5: Marginal: There are two major flaws and several minor flaws; I could barely read your writing.

4: Insufficient: There are several major flaws; I could not read your writing on many of the answers or had to hunt through your papers for the answers.

3: Fairly Bad: I could not find some of the answers, and the work is very sloppy. There are major and minor flaws. Please visit the writing center for a reminder on spelling, grammar, and sentence construction.

2: Bad: I couldn’t read your writing, and the spelling and grammar were poor. The work is sloppy, but it appears that you attempted every question in the assignment.

1: Very bad: You have made no effort to show respect for your own work, or for the time your professor will require to grade it.

0: Not performed

Giving collective marks takes very little time, once I’ve graded the content.

Depending on how many students I have (and how far behind I am in my grading!), I may circle the flaws (such as spelling errors) on their assignment. But I don’t stress about making sure to catch every flaw or giving a correction. I just make a circle and move on.

Before I started using collective marks, I felt conflicted about grading for things like spelling. It seemed wrong to just ignore bad spelling or messy papers, but at the same time, I didn’t feel I had adequate time to correct every student’s grammar.

Collective marks let me do that in a way that lets students know I care, and I notice, but then puts the student back in the position of learning how they should have spelled “gallactic.”

I also find that collective marks reward the students who take the time to carefully write out their assignments, check their spelling, or make careful drawings. I have been known, on rare occasions, to give 11/10 for collective marks, because a student shows such diligent care.

Using collective marks saves me time, makes my grading more consistent, and rewards students who are careful and thoughtful in their work.

Give them a try and let me know how it goes!