Big news: We’re moving!


usstates-3d-bgAfter 8(!) sunny years in Pasadena, CA, we’ve decided to move back to the east coast! We’ll be making the cross-country trip to Cambridge, MA, in late August.  Yes, it will be cold and rainy sometimes, and yes, we’ll deeply miss all of our friends and colleagues in southern California, but we’re also looking forward to this next step! Woohoo!


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Pluto, Mars, Moon, Earth


At the 2013 annual meeting of the American Geophysical Union, Michael Carr give the Shoemaker Lecture on “Geologic Exploration Of The Planets: A Personal Retrospective Of The First 50 Years.”  I was lucky to hear it, because he included this anecdote about Mariner 9’s arrival at Mars in 1971:

The planet was engulfed in a dust storm and very little could be discerned except for polar caps and some dark spots which turned out to be volcanoes poking up above the dust.  As an aside, there was a lot of argument about those volcanoes. They looked exactly like calderas. But already by that time, the perception of Mars as a lunar-like body had solidified, and there was just enormous resistance to interpreting those dark spots as the summits of volcanoes.


Before Mariner 9 reached the red planet, Mariner 4 flew by on July 14, 1965, returning 22 images of a rugged, cratered surface that had never before been seen – not quite what the imaging team expected to find!  This bulletin, circulated to the DSN stations along with the photos, sums up how these results affected the understanding of Mars and its planetary evolution:

Man’s first close-up look at Mars has revealed the scientifically startling fact that at least part of its surface is covered with large craters.  This is a profound fact which leads to far-reaching fundamental inferences concerning the evolutionary history of Mars and further enhances the uniqueness of Earth within the solar system… Some mention must be made of features looked for but not seen on Mariner photos.  Although the flight line crossed several “canals,” sketched from time to time on maps of Mars, no trace of these features was discernable.  It should be remembered in this respect that the visibility of many Martian surface features, including the “canals,” is variable with time.

Mariner_Mars_'64_Bulletin_No_52_Aug_4_1965-1-2Mariner 4 arrived at Mars to find it cold and barren – “more Moon-like than Earth-like” – and that revelation, as Mike Carr recalled, fueled the dominant perception of Mars for the missions that followed.  The Mars of 1965 had to fit somewhere in our limited palette of planetary analogs, and the never-before-seen craters of the ancient highlands tipped the scale toward the lunar end.  Ground-based observations of the seasonal cycle on Mars, evidenced by the retreat and expansion of polar caps and changes observed in shade and placement of darker regions, had inspired hopes of a geologically active planet, but the cratered terrains and absence of a magnetic field said otherwise.  In fact, they said it so loudly that when Mariner 9 caught a glimpse of Olympus Mons “poking up above the dust,” it took a lot of convincing to entertain the notion that Mars might be more Earth-like than our first encounter suggested.

Yesterday – fifty years to the day after Mariner 4’s Martian flyby – NASA’s New Horizons spacecraft made its closest approach to Pluto, and we have been bathed in ever more detailed images of the dwarf planet and its moons for the past several days.  As the photos have gotten clearer, a chorus of comparisons has risen:

Pluto is red! It looks like Mars!

Of course, Pluto isn’t red for the same reasons that Mars is red (space-weathered hydrocarbon molecules vs. iron oxides), so there are plenty of holes to poke in the analogy…

It’s been very exciting to see Pluto come into focus, and even more interesting to watch the process of viewing, describing, and naming features that have gone from light or dark patches to “the whale” or “the heart.” I can’t avoid thinking of this process in the context of previous planetary quests, especially Mars exploration with its history of telescopic observation, flybys, orbiters, and rovers.  It’s satisfying to see that Mars has graduated to become an analog for even newer worlds – what an exciting time to be alive!

Credit: NASA

Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

Posted in Extra Credit, Reflections | 1 Comment

Stitching a Supernova


When John R. Whitman saw an X-ray image of the Cassiopeia-A supernova in Scientific American in 1975, he decided it would make a lovely needlepoint design, and when he wondered who he might ask to produce it, he immediately thought of his good friend, Dr. Cecilia Payne-Gaposchkin.

“I met with Cecilia to inquire if she might have any interest in producing the first example of my design. She looked at me with her penetrating gray eyes, normally focused on stellar distances, and exclaimed that, yes, she would be delighted to create the Cas-A needlepoint. I was overjoyed.”1

Whitman originally designed his Cas-A pattern as part of a needlepoint kit for Intercraft, a craft startup that never really came together.  The prototype – carefully stitched by Dr. Payne-Gaposchkin, then in her seventies and retired – remained in storage for years before joining her collection at the Harvard University Archives.2

In a brief article for PieceWork Magazine in 2004, Whitman described how his friend Philip Charles, a co-author of the Scientific American paper, sent him the data file for the Cas-A X-ray image.  He printed the schematic using a computer at the Smithsonian Institution’s Center for Short-Lived Phenomena, where he worked at the time.

“The computer I used was, at the time, the largest civilian computer in New England, a CDC-6400 that, when not printing out needlepoint designs, was calculating massive equations for astronomers and tracking satellites (the Smithsonian was then operating the world’s first satellite-tracking system).”


“Several months later, Cecilia presented the needlepoint to me with great pleasure and much pride. It was a gorgeous sight. Her workmanship, primarily employing the Scotch stitch, was superb, and everyone who saw it was highly impressed with its quality and beauty.”


It’s a curious little anecdote, but a valuable one.  Dr. Payne-Gaposchkin is rightly remembered for her pioneering work in astronomy and for overcoming so many hurdles to achieve it.  This little needlepoint offers a tiny window into her other interests, of which Whitman insists there were many:  traveling, cooking, printing, quoting Shakespeare, and devouring mystery novels, to name a few.  In his own words:

“Cecilia’s needlepoint rendition of the Cas-A image represents a fascinating intersection of her place in astronomy, her dexterity as an accomplished stitcher, and her devotion as a friend. Created with the hands of a genius who left far more valuable astronomical works behind, this treasure is no less wonderful for her touch.”


  1. Whitman quotes are from “The Cecilia Payne-Gaposchkin Cas-A Needlepoint Story,” PieceWork Magazine, July/August 2004
  2. Whitman: Images of her needlepoint are now included in the Harvard Archives, available to all for scholarly and educational purposes.”
Posted in Extra Credit

Exploring “Genius Day” with Annie Jump Cannon

1892-pplc6-annie-jump-cannon-1893 (1)

This past Saturday, I co-ran a”Genius Day” workshop for a dozen or so middle school-age kids for a local non-profit organization, the Institute for Educational Advancement.  Previous “Genius Days” have focused on Darwin, Shakespeare, and William Strata Smith, and I helped out a friend last summer with some Galileo-themed activities.  At first, I was little skeptical of the focus on Genius and Geniuses, because there’s so much baggage around figures in the history of science bearing that title, and because (IMHO) kids – especially ones who are constantly told they are “gifted” – don’t need added pressure to live up to an impossible ideal. So I was initially a bit worried about what I would encounter at a “Genius Day” centered on Galileo. What I did find, however, was a focus on interrogating the idea of “genius.” Impressions of the word were collected at the beginning of the day and re-examined at the end, after a series of activities and discussions and slide presentations.  It was well done!

When the opportunity arose (several months later) to run one of these workshops myself, we decided to focus on Annie Jump Cannon – the first woman in the series.  There are a lot of threads to Cannon’s story, and that complicates the notion of “genius” in a good, thought-provoking way.  She’s a woman who worked primarily in a man’s world.  Whether her employer, E. C. Pickering, was progressive or just penny-pinching for hiring women to work as researchers is a question that has no straightforward answer.  She also lost most of her hearing to scarlet fever in early adulthood.  Her impressive work – developing a stellar classification system and classifying hundreds of thousands of stars – was the product of decades of hard work, and understanding her achievement requires knowledge of photography (including photographic plates), prisms, spectra, and absorption lines.  Having navigated all of this over five hours this past weekend, I thought it would be useful to share some of the materials that we – myself, along with Louise Hindle and Min-Ling Li at IEA – gathered and created for the workshop.

Carnegie Observatories - plate demonstration

After an introductory discussion about the word “genius” and everything it might mean, we launched into a discussion of photography. I wanted to get the kids thinking about how photographs are and are not objective representations of reality. We talked a lot about how the choices they make in taking photos – even digital ones with their smartphones – influence the final product, and we connected this idea of “making” a photo (rather than “taking” one) to older forms of photography.

Then we really had a treat! Representatives from the Carnegie Observatories Cindy Hunt, Andrew Benson, and Catharine Vlahakis brought over several real photographic plates from the Mt. Wilson Observatory archives to look at.  From the surface of the Moon, to spiral galaxies, to nebulae, there was plenty to marvel over, and having the physical objects there really drove home the materiality of the photographic medium.  Hubble PlateThey even brought a plate from Edwin Hubble’s search for variable stars in the Andromeda Galaxy, complete with his fingerprint baked right into the photographic emulsion – talk about tangibility!

Many of the participants took photos of the plates with their phones and had fun reversing the negatives to see what they would look like to the eye, and I think some of those points about the manipulability of photographs really landed with them.

Spectroscopic PlateAfter the plate demo, we were able to bring the discussion around to the difference between the kinds of direct images on the plates we had seen and the spectroscopic plates that Cannon would have been working with.  To help with this, we used an image of one of Cannon’s actual spectroscopic plates that Jonathan McDowell, an astronomer working at the Harvard Observatory (where Cannon worked) now, had very helpfully provided for us. Each of the little blurred lines is a star, the starlight having been spread out into a bar by a prism. The colors themselves didn’t make it into the photograph, but many of these spectra show clear absorption lines – gaps in the rainbow where no light is seen.  Using the placement and intensity of these lines, Cannon grouped them into different star types.  Looking at all of the star spectra and the careful notations, you can really get a sense of the kind of work that went into Cannon’s stellar classification system, and you can see more of the Harvard plate archives here.  This image became a jumping-off point to talk about the kinds of scientific information that photographs can provide – and then it was time for lunch!

After a brief lunch break, we headed out to the Huntington’s wonderful “Beautiful Science” exhibit to see the one item in the collections1 related to Cannon: a letter she wrote to Mt. Wilson Observatory astronomer F.H. Seares in 1912.  A mix of personal and professional comments, the letter was sent while Cannon was on vacation, and she writes of her current work: ” I hated to leave my catalogue with 45,000 stars classified, but so many more to do! However, my mind will be refreshed and body rested by the plunges in Old Ocean I am going to have.”

Letter from Cannon to SearesLetter from Cannon to Seares

Back out on the lawn, we talked a bit about how Cannon has been described at various times, from her own lifetime to today. A brief article from 1929 describes her as an “eminent astronomer,” even while the title of the piece suggests an “invasion” of women into the field of astronomy. astronomy-invadedA “Wonder Women of History” comic from 1949 (part of the original Wonder Woman series) portrays her as a determined and accomplished pioneer, but adds that she loved spending time with children as well. A modern depiction from shows Pickering helpfully steadying the ladder while Cannon climbs up beside a telescope, holding a wrench.  All of these examples bear on how we talk about women in the history of science and women in STEM today.

After heading back to the classroom, we passed out diffraction gratings (which work a lot like prisms) called Rainbow Peepholes2 and used them to look at a variety of light sources: the fluorescent lights overhead, a flashlight, white incandescent and colored LED holiday lights.  Immediately engaged by the “hidden rainbows” revealed to them, the students really got into exploring the differences between the different light sources. They noticed that white light is spread out into the entire spectrum, but the red and green LEDs were just…red and green.  Interestingly, the light from the purple LEDs was separated into just two colors (blue and magenta).


This activity connected directly back to the spectroscopic plates that Cannon worked with, and we followed up by attempting to classify the spectra ourselves into at least two identifiable groups.

We didn’t quite have time for the last activity – making stellar trading cards – but we sent everyone home with the materials to make their own. Here’s the trading card template I put together and a bunch of Cannon quotes about her work and the field of astronomy as she saw it. Feel free to use it, or adapt your own! I imagined using it to make a card for each star type, but you could also do it with individual stars, and I could see it working for other kinds of objects – moons, exoplanets, asteroids – too!

We wrapped up the day with a discussion about spectroscopy in astronomy and remote sensing today, and we talked a bit about how the spectral classes fit into our understanding of how stars evolve and what’s going on inside them. And that was it! Quite a long day, but very rewarding, and I’m happy to share all of our work putting this workshop together.  If anyone else has resources to add, or would like more information on what we did, please let me know!

  1. Many thanks to Huntington curator Melissa Lo for locating the letter and many other useful materials!
  2. Thanks to Holly Bender for alerting me to these – the name is a bit strange, but the kids loved them!
Posted in Extra Credit, News, Reflections


I made this (hastily) for MESSENGER’s final pass around Mercury and impact just now.  Few spacecraft have dealt with heat o’ the sun and winter’s rages like this one! It has really been an impressive mission.

The Cymbeline quote is all the more appropriate given that MESSENGER’s final resting place is near Shakespeare basin.

Posted in Extra Credit

“So You Want to Do Research”

Cecilia_Helena_Payne_Gaposchkin_(1900-1979)_(3)I recently came across a brief article entitled “So You Want to Do Research” in the December 1943 issue of Pro Tem, a Radcliffe College campus publication.  Written by Dr. Cecilia Payne-Gaposchkin, the column offers some advice to students considering a career in research and describes some of the astronomer’s views on the process of science.  Payne-Gaposchkin describes an environment that is both demanding and rewarding, and she doesn’t sugarcoat the tougher bits.  Some of her advice sounds so applicable to graduate students today that it’s almost jarring to come across a sentiment or stylistic element that belongs to an earlier time, as when she consistently uses male pronouns to describe “a scholar” in the abstract.  I’ve pulled out a few excerpts that spoke to me here, but the whole article is available in Harvard’s digitized collections.

Only become an astronomer if nothing else will satisfy you; for nothing else is (approximately) what you will receive.  The material returns will never be great, and most of the scholars who receive them do so at the price of sacrificing time that they might devote to pure scholarship.  Fame is the reward of the few, and those who achieve it realize too often that it has been purchased by efforts that were not their highest.  If you do your job, you will be able to earn your living, and you will taste the delights of discovery, than which (to the addict) there is nothing more satisfying.  That is all.  If it is enough, then become a scientist.  If it is not, get out before it is too late.
Screen Shot 2015-04-28 at 11.55.05 AM

Probably the most important starting points are good health, good eyesight, humility, and a sense of humor.

There are some for whom the world seems to hold no mysteries; for them, everything fits into a preconceived scheme and the whole is convincingly explained.  They will never be scholars.

…a complex training, difficult to describe, yet more difficult to achieve.  It involves a continuous habit of sorting the uncoordinated facts, fitting them together again and again until some pattern emerges, seeking other facts that seem to piece out the pattern.  The process is one of working ceaselessly on an intellectual jigsaw puzzle, in which you have little clue to the subject, the scale of the design, the relationships of the pieces.  The very elusiveness of the pattern is its chief fascination, the possibility that the final picture may prove to be of something never before seen by mortal eyes.

Astronomy is peculiar in several respects; it is a science debarred from experiment, and it deals chiefly with processes that are so slow that they defy any but long-drawn and precise observations.  It is a schooling in precision and patience, and it compels the construction of long-term plans and the formulation of long-term problems.

ceciliaLastly, there should be a word about technique.  Not the detailed technique of the branch of knowledge, the particular vocabulary, symbolism, and equipment.  Rather the technique of the intellectual jig-saw puzzle.  Let no one expect it to be easy work. It is hard labor, often carried to the point of exhaustion and despair.  Repetitions carried to the point of utter boredom. Simple, elementary processes that would shock the uninitiated by their naïveté.

The popular conception of scientific research: ‘You must be so very clever to be able to do it’ could not be wider of the mark.  Real investigation is not the reception of a transcendental vision, a process of thought beyond the power of an ordinary mortal.  The prayer of the scientist might well be, “Lord, show us the obvious.”

As a science communicator, I spend a lot of time trying to convince people that you don’t have to be “so very clever” to understand or to do what scientists do on a day-to-day basis.  It’s very much within “the power of an ordinary mortal,” because, well, scientists are ordinary mortals.  From a historian’s perspective, it’s interesting to hear Payne-Gaposchkin’s thoughts on academic fame.  It’s both conferred rather arbitrarily, and it takes up time that could be devoted to pure research.  By 1943, she had already received numerous awards for her work,1 so it’s interesting to hear a somewhat cautionary note in her address to students.2  And as a former (recovering?) graduate student, I appreciate her no-punches-pulled description of the “exhaustion and despair” and “utter boredom” of research just as much as her admission that she’s an addict of the “delights of discovery.” So you want to do research? Couldn’t hurt to read this first.

  1. She was elected to the Royal Academy of Sciences in 1923, while still a student at Cambridge, she received the first Annie J. Cannon Award in 1934, became a member of the American Philosophical Society in 1936, and was elected to the American Academy of Arts and Sciences in 1943.
  2. It also brings to mind the controversy over her dissertation: having found that hydrogen is by far the most abundant element in the Sun (a result contradicting prevailing theories of stellar composition), heavyweight astronomer Henry Norris Russell convinced to reject her values for hydrogen and helium abundance.  Four years later in 1929, after arriving at the same conclusion using different methods, Russell published a massive paper on the subject, and although he credits Payne-Gaposchkin’s work at the end, he’s generally gotten the lion’s share of the credit.
Posted in Extra Credit, Reflections

Annie Jump Cannon in Her Own Words

Annie Jump CannonI’ve been poking around the Harvard Library’s digital archives quite a bit this week, preparing for a “Genius Day” workshop I’m leading next month with the Institute for Educational Advancement.  The focus of the workshop is Annie Jump Cannon, an astronomer famous for developing the stellar classification scheme still used today and for personally classifying hundreds of thousands of stars by their spectra.  While trying to track down a high-resolution scan of one of Cannon’s spectroscopic plates,1 I came across an article she wrote in the Radcliffe Quarterly in 1931 entitled “Astronomical Adventures.” In recounting some of her experiences, she describes a field “at a cross-roads between the old, the visual, and the new, the photographic method,” and offers a new definition for the “adventures” in store for aspiring astronomers. I thought I’d share a few brief excerpts that I particularly enjoyed, but feel free to read the entire account here. 2

Typical Spectra, from Cannon, Spectra of bright southern stars...Astronomers are not often thinking of pure discovery. We have no expectations of ever finding at one glance, as did Tycho Brahe, a new star rivaling Venus in brilliancy, nor any hope of emulating Galileo’s thrilling experiences. Something different must satisfy us in these later days.

Has it not been something of an adventure to take any part, however small, in the remarkable development of astronomy during the present century?

It is often difficult when one stands at the cross-roads to choose the new and untrodden path. It is not the path of our dreams. Who in the “gay nineties” ever dreamed of an astronomer who was not nightly gazing through a large telescope at soul-thrilling celestial objects? Time has proved, however, that along the new and seemingly unromantic photographic path lay all the coming adventures.

There is romance in science! What more appealing to the imagination than the fact that these dark lines in star light bring us messages as to what the stars are, how they are traveling, and how far away they are.

The spectrum of such a star, if it can only be obtained, always tells the story of its vagaries in the bright bands indicating glowing gases. Not soon to be forgotten was the thrill of finding such an object while in Arequipa, of eagerly photographing its spectrum and beholding on the negative the tell-tale bands proclaiming its escapade. To the gleaming southern stars, thus one was added, whose light had been traveling fifty thousand years to shine down on us over the Andes.

NYTimes Headline, Solar Eclipse of January 24, 1925When the California astronomers came east to the eclipse of January 24, 1925, we could boast of no such optimistic weather reports, but almost contrary to our own expectations, we had a clear sky on that below zero morning. No clouds marred the spectacle from Cornell to Nantucket. The mystical shadow bands danced, glowing prominencies streamed out, and the glowing corona flashed forth its matchless beauty.

Curious, I looked around for other personal accounts from the women at Harvard College Observatory, the “computers” that were the backbone of Edward C. Pickering’s research program in the decades surrounding the turn of the 20th century.  While not at all a comprehensive survey of the online archive’s content, my little search yielded a couple of items that I am truly happy to have come upon. I’ll do my best to share some of them here as well.

  1. Thanks to Jonathan McDowell and twitter, I now have many wonderful photographs of the Harvard plate stacks and Cannon’s spectroscopic work!
  2. And for a very adventurous version of Cannon, check her out on Rejected Princesses!
Posted in Extra Credit, Reflections

The Not-So-Brief History of Climate Change Science

As part of my ongoing collaboration with NASA’s Orbiting Carbon Observatory 2 mission, I’ve put together this 4-minute history of climate change science.  Global warming may seem like a recent issue, but people have been investigating it for a long time.   Only by choosing to engage with the natural world and gathering information can we prepare for whatever the future may bring.

Posted in Extra Credit, TA Episodes

New Books in Astronomy: Bill Sheehan and Chris Conselice, Galactic Encounters

Galactic EncountersThis past month has been really crazy with all of the podcasts, but I’m finally catching up with my New Books in Astronomy interviews. In the latest episode, I talked with William Sheehan and Christopher Conselice, co-authors of a new book called Galactic Encounters: Our Majestic and Evolving Star-System, From the Big Bang to Time’s End.  I really enjoyed the book and I was very happy to be able to speak with both of them together.  Sheehan and Conselice bring their complementary backgrounds in history, psychiatry, and astronomy together to present both the current understanding and historical context of investigations into the nature of “fuzzy” objects in the night sky, from distant nebulae and galaxies to our own Milky Way galaxy.  A couple of my favorite chapters have to do with E. E. Barnard and early astronomical photography (Chapter 7) and W. W. Morgan and how he recognized the spiral structure of the Milky Way (Chapter 12).  But there’s a whole lot more, from the Herschels to Hubble and on to dark energy!

Posted in Extra Credit, NBN Episodes

Manh(a)ttan Brings Nuclear Physics to Primetime (Physics Central Podcast)

Of all the new television shows to premiere last fall, my favorite was Manhattan, a fictionalized retelling of the development of nuclear weapons at Los Alamos during WWII.  As a historian of 20th-century science and as the curator for the Tolman/Bacher House at Caltech (both Tolman and Bacher played large roles in the Manhattan Project and its aftermath), this show is especially exciting to me, but it also has the potential to seriously misrepresent the history I care about.  To achieve their dramatic goals while avoiding some of this risk of pseudo-history, the show creators pursued a really interesting strategy.  All of the main characters (aside from a couple of important figures, like Oppenheimer) are completely fictional, operating within the larger (mostly historical) framework.  I wanted to know how much of the history and science they get “right” on the show and what that really means when you’re dealing with a tradeoff between drama and reality, so I spoke with science writer and former Director of the Science and Entertainment Exchange Jennifer Ouellette and Executive Director of the Los Alamos Historical Society Heather McClenahan about their impressions of the show.  Both Ouellette and LAHS held weekly events to recap and discuss new episodes as they aired.  What was the consensus? Manhattan certainly doesn’t portray everything at Los Alamos as it would have been, and some exaggerations didn’t go over well with its former and current residents.  It did succeed, however, in portraying scientists at work and McClenahan noticed a decided uptick in tourism resulting from the show.  Overall, everyone seems happy enough with a show designed not as a documentary, but as a vehicle to explore the timeless issues of secrecy, privacy, and surveillance.  It’s been renewed for a second season, and I have reason to believe the show will have an excellent reference on hand when it comes to history.  I, for one, can’t wait!

These brilliant opening titles appeared in the third episode and added A LOT to the show (for me). Talk about a way to visually represent the all-too-human connotations of “implosion.”

Posted in Extra Credit, Physics Central