A Journey to the Center of the Earth

Verne-diamond

Jules Verne, Voyage au Centre de la Terre: Imaginary visit inside a diamond.

“La science, mon garçon, est faite d’erreurs, mais d’erreurs qu’il est bon de commettre, car elles mènent peu à peu à la vérité.”

“Science, my boy, is made up of errors, but these errors are worthwhile to commit, because they lead little by little to the truth.”

–Jules Verne, Voyage au Centre de la Terre

Eighteen hundred miles (2,900 kilometers) below your feet, the solid rock of Earth’s mantle gives way to a roiling core of molten iron (with a little bit of nickel thrown in for good measure).  Embedded within this liquid outer shell lies a solid inner core, squeezed enough by the immense pressure that the solid phase of Nickel-Iron is most stable, no matter the intense heat.  No one has ever directly observed these divisions deep within our planet, yet their existence is confirmed each time an earthquake rattles chandeliers and rings the Earth like a bell.  Whether the interior was solid or liquid, or even gaseous, remained a matter of debate up through the first quarter of the 20th century, after which consensus settled on a two-layer model of the Earth, solid outside and liquid within.1

Seismic Rays

Examples of seismic rays propagating through Earth’s layers. The P-wave shadow zone lies between about 103 and 143 degrees from the epicenter.

One major piece of evidence in support of this model was the behavior of seismic waves generated in an earthquake, which can be felt and recorded at locations all over the globe.  Earthquakes trigger many different types of waves that propagate either through the body of the Earth or along its surface. Of the former type, P-waves (primary) always arrive first and are longitudinal, like sound waves in air, while S-waves (secondary, or shear) arrive second and are transverse, more like a wave on a string or a ripple on a pond.  How fast each of these waves can travel is controlled by the material properties of the medium, and when a wave encounters an interface between layers with different material properties, it will bend, just as a beam of light bends when it crosses from air to water.

When a P-wave hits the core-mantle boundary (CMB), its seismic velocity drops abruptly, and it’s refracted, and its trajectory is bent.  When it reaches the other side of the core, it is refracted again (the opposite way), and as a result of these gymnastics, that particular wave is recorded somewhere at the surface far away from the location it would have reached had it taken a direct path.  The angle of refraction depends on the angle of incidence and the ratio of velocities going from the mantle to the outer core (just like Snell’s Law in optics), and it results in a shadow zone where P-waves just aren’t observed within a certain range of distances from the earthquake epicenter.

Speeds_of_seismic_waves

Average P-wave (orange) and S-wave (purple) velocities through the different layers of the Earth.

To see why that happens, consider two almost identical ray paths, one of which almost hits but misses the CMB and the other of which hits the core and is refracted.  The first ray will only pass through the mantle, so its trajectory is pretty direct,2 but the second ray is bent away from its initial direct path.  No P-waves can arrive between about 103° and 143° of the epicenter, leaving a donut-shaped region of absent arrivals – a shadow of the core.

Things get even more extreme when you consider S-waves, which can’t pass through liquid at all.  That’s because static liquids can’t support shear stress (which is why they conform to the shape of whatever container they’re in), so shear waves just can’t get through and aren’t seen beyond about 103° from the earthquake epicenter.

So that’s where it stands: no P-waves from 103°-143° and no S-waves at all beyond 103°.  Except…there are waves that arrive in that shadow zone, so where do they come from? Actually, those shadow boundaries are a bit fuzzy because some waves skirt around the CMB through a process called seismic diffraction, but even that can’t explain all of the supposedly forbidden arrivals in the shadow zone.  For that, there needs to be an inner core.

That’s exactly what Inge Lehmann,3 head of the department of seismology at the Geological Institute of Denmark, realized after a large New Zealand earthquake shook things up in 1929.  Examining the data from the Danish network of seismic observatories, which were at a great enough epicentral distance to address this outstanding issue, she suggested that an inner core with a slightly elevated seismic velocity could explain the problematic arrivals.4

Lehmann-fig3

Figures from Inge Lehmann’s 1936 paper, P’, showing seismic wave signatures at many Danish stations.

Lehmann-fig1

Ray paths through the Earth with an inner core.

Lehmann-fig6

Waveforms, 1929 New Zealand earthquake.

 

Within a couple of years, this explanation was widely accepted by the seismology community, although the fact that the inner core is solid, first proposed by Francis Birch in 1940 and extended by Keith E. Bullen in 1946, could not be decisively determined for several decades.  Bigger earthquakes naturally produce seismic waves that sample greater depths, and to “see” the inner core, seismologists needed a really big one…or better yet, several.  In the 1970s, analysis of recent large earthquakes that had excited the lowest, fundamental frequencies of the whole Earth provided support for a solid core.

Our understanding of the internal structure of our home planet is improving all the time, as seismic networks expand, international collaborations pool data, and computational power advances.  Huge earthquakes can be–and frequently have been–devastating in terms of human lives lost, but these deadly events also offer hints as to what lies beneath our feet and how it got to be that way.  Some say that space is the final frontier, while others reply that the oceans remain largely unexplored.  Earth’s interior offers another tantalizing frontier, and while a Vernian journey to the core is unlikely (to put it mildly), geophysics gets us a pretty good view, even from all the way up here.

  1. Historian of science Stephen G. Brush attributes most of this gathering consensus to the 1926 paper and persuasive powers of Harold Jeffreys.  While most textbooks point to the P-wave and S-wave shadows as the key evidence for a liquid core, Brush points out that the final straw came from a different argument altogether, one based on the total rigidity of the Earth as measured from tides and the observed (higher) rigidity of the mantle alone (i.e., the mantle is more rigid than the whole Earth, so the core must be less rigid to account for the average).  “The transmission or nontransmission of shear waves has not been a decisive test for solidity or fluidity, contrary to frequent statements in the literature.  Those who believe for various reasons that a certain region of the Earth is fluid have been able to find plausible explanations for the apparent transmission of shear waves through that region.  Conversely, if other evidence seems to prove that a certain region is solid, plausible explanations for failure to observe transmission of shear waves through it can be found.” Brush, 1980 “Discovery of Earth’s Core.” Am. J. Phys. 48 (9).
  2. The paths of seismic waves are not actually straight lines, because the density within each layer is constantly increasing as you go deeper and deeper.  The increasing density corresponds to increased seismic velocity, and the waves are continuously refracted to form a curved trajectory.
  3. More on Inge Lehmann over at TrowelBlazers
  4. Lehmann, Inge (1936): P’. Publications du Bureau Central Séismologique International A14(3), S.87-115
Posted in Extra Credit | 1 Comment

New Books in Physics: Don Lincoln, The Large Hadron Collider

Last Monday, I sat down (via Skype) with Fermilab senior scientist Don Lincoln to discuss his new book, The Large Hadron Collider:  The Extraordinary Story of the Higgs Boson and Other Stuff That Will Blow Your Mind.  This interview is my first contribution to the New Books Network (I’ll specifically be contributing to the Physics and Astronomy channels), and you can listen to the full hour here.

What Dr. Lincoln excels at, in the book and particularly in conversation during the interview, is calling up appropriate analogies to explain incredibly complex topics.  One of my favorite examples is when he compares the different types of magnets that keep the proton beam of the LHC on track to a team of Kindergarten teachers trying to keep an unruly group of children moving in the right direction.  I really enjoyed chatting with him about his experiences, both as a high-level researcher and an avid science communicator, and how those two passions feed back on each other.  Being able to explain a concept to others is truly a formidable test of understanding it yourself, and, as Dr. Lincoln says, a useful analogy or physical intuition–while not perfect–can help focus your attention and help you move forward as a scientist.

In addition to numerous books, Dr. Lincoln is responsible for many of the short videos on Fermilab’s YouTube channel, as well as a TedEd video explaining the Higgs field:

As a side note, I remember watching this video two years ago when the Higgs announcement was made.  As I recall, another analogy involving a snowy field was printed in the New York Times around the same time, and I remember wondering whether all Higgs boson analogies needed to trade on different meanings of the word “field” to get across (Higgs field, snowy field, field of physics…).  Just a funny coincidence, I guess.

In any case, I greatly enjoyed hearing from Dr. Lincoln and he has a real knack for telling stories and explaining concepts.  If you’re at all curious about modern particle physics or an insider’s perspective on the LHC and the Higgs, give the interview a listen (or better yet, pick up the book)!

The Large Hadron Collider by Don Lincoln

Posted in Episodes, Extra Credit | Leave a comment

MAVEN and the mystery of the Martian atmosphere

Image Courtesy of NASA

Just  a few hours ago, a visitor from Earth reached the Red Planet and traded her terra-bound orbit for a Mars-centric one.  The Mars Atmosphere and Volatile Evolution spacecraft, or MAVEN, has a specific assignment:  to characterize the upper atmosphere of our neighboring world and the processes that shape its evolution over time.  MAVEN is an exciting mission, and it’s taken 10 months and 442 million miles just to get into orbit.  It will take another five weeks to circularize that orbit and settle into the primary measurement configuration.  That may seem like a long time (to say nothing of the preparations and planning leading up to the launch last November), but MAVEN is part of a much longer tradition that puts our most recent ambassador to Mars in perspective.

mars-maven-orbit

Mars has long been an object of fascination for astronomers and the public alike, and its mysterious atmosphere has stubbornly remained at the center of speculations as to the planet’s past (and current potential) habitability.  The characteristics of the atmosphere – its composition and density – control the possibility for liquid water to exist on the surface.  Mars’ atmosphere is more than 100 times thinner than Earth’s, and it’s made up of different molecules.  Whereas Earth is shrouded with a thick nitrogen blanket (77% by volume) with ample oxygen thrown in (21%), Mars’ more tenuous atmosphere is 96% carbon dioxide.  Although the total atmospheric pressure at the surface (~6 millibars) seems to just barely put Mars within reach of the triple point for water (the lowest pressure at which liquid water can exist), it’s the partial pressure of water vapor that needs to be that high, and at 0.03% by volume, there’s just not enough of it there.

Phase_diagram_of_water_under_martian_conditions.svg

Telescopic claims of a Martian atmosphere date back at least to William Herschel, who reported on changes he observed on the Martian disk in 1784: “And these alterations we can hardly ascribe to any other cause than the variable disposition of clouds and vapours floating in the atmosphere of that planet.”  Several emerging similarities between the Earth and Mars were making headlines at the end of the 18th century, based on measurements of physical properties that were not far off modern values.  Our two planets have very close rotation periods, with a Martian day lasting just 37 minutes longer than our own.  The tilt of Mars’ rotation axis is 25°, just a degree and a half more than Earth’s, implying that our neighboring planet experiences seasons as it makes its way around the Sun.  And, perhaps most strikingly, Mars has polar caps that change in size and distribution throughout those seasons, evoking for some an image of Mars as another Earth.  Observations of a Martian atmosphere strengthened this analogy, and Herschel optimistically concluded that “its inhabitants probably enjoy a situation in many respects similar to ours.”

Screen Shot 2014-09-22 at 6.53.52 AM

Whether Herschel’s “clouds and vapours” really existed was a matter of debate for much of the 19th century.  Johann Schröter agreed with his mentor, writing that “the same shapes and positions develop and pass away again, as one would expect of the variable atmospheric appearances occurring above a solid surface.” In 1830, the great mapmakers Beer and Mädler denied the existence any atmosphere, having themselves observed no changes that might be attributed to clouds or mists hovering above the surface.  Nevertheless, the idea persisted, and with it the assumption that the composition of a Martian atmosphere would match that of Earth’s.  Richard Proctor’s 1870 book Other Worlds Than Ours cited early spectrographic observations from a Dr. Huggins in support of an Earth-like atmosphere for Mars.  “[W]e know that it is the aqueous vapor in our air which causes the appearance of the lines in question.  Hence there must be aqueous vapor in the Martial atmosphere.”  The detection of water vapor (or its absence) remained a hot topic throughout the remainder of the 19th century and well into the 20th.  In 1909, W. W. Campbell, director of the Lick Observatory, published results showing that the “quantity of water vapor present, if any, must be very slight,” directly contradicting observations by Slipher and Very the year before.  In the 1920s and 1930s, Walter S. Adams made several attempts to detect Martian water vapor and oxygen, to no avail.

Screen Shot 2014-09-22 at 8.13.10 AM

These observations and debates were occurring in the midst of the (in)famous Martian canal controversy, driven in large part by Percival Lowell, who founded an observatory in Flagstaff, Arizona, just in time for the 1894 opposition of Mars.  To Lowell, the seasonal polar caps and linear markings he interpreted as artificial constructions suggested a vast network of channels meant to control and conserve surface water on a planet that, due to its smaller size and greater distance from the Sun, was at an advanced stage of planetary evolution relative to Earth.  The canals were thus an expression of ecological disaster, a last attempt to manage a dwindling resource, and a dire warning for mankind as to the fate of our home planet.  The canal controversy fired the public imagination and Mars became a canvas on which to project our own fears and hopes for the future.

Today, we know that the “canals” were not built by intelligent Martians, and we have sent our envoys to orbit the Red Planet and traverse its dry and windswept surface.  In 1963, Andouin Dollfus released his observations of a very minute amount of water vapor present in the Martian atmosphere, and a few years later, Mariner 9 returned a close-up look at the surface features so long imagined from Earth.  The 1976 Viking landers established the composition of the atmosphere to unprecedented accuracy, and many planetary missions since then have returned a wealth of information about our neighbor’s current and past climates.  There is much we still don’t know, however, and by concentrating on the processes of the upper atmosphere, where molecules might escape due to simple thermal velocity or be stripped off by interactions with the solar wind, MAVEN will tell us about the planetary evolution that so captivated Lowell and many others a century ago.  It is likely that Mars once had a much thicker atmosphere than it does today, and while there are many theories and models that could explain why it disappeared, we don’t yet know the answer.  MAVEN’s seamless arrival at the Red Planet will soon help us fill in some of the gaps in our understanding, extending and upholding a long tradition of inquiry into Mars’ mysterious atmosphere.

Image credits: MAVEN spacecraft (image courtesy of NASA); MAVEN’s orbit insertion maneuver (image courtesy of NASA); phase diagram for water (Wikimedia Commons); Martian polar caps, sketches by Herschel (Phil. Trans. R. Soc., vol. 74, 1784); Sketch of Mars, Plate VII, by Lowell (Mars, 1895).

Posted in Extra Credit, Reflections, Uncategorized | 1 Comment

A slice of Caltech history

The Tolman/Bacher House, from the 1930s (with Richard and Ruth Tolman relaxing outside their home) to today.

For the past several months, I’ve been working with the Keck Institute for Space Studies (KISS) to gather historical materials for the Tolman/Bacher House, one of the oldest buildings on campus, and with the Keck Center dedication yesterday, all of our hard work has paid off! In addition to the physical exhibits, which are tucked away in the bookcases and mantel-tops of the Oort Cloud Lounge (originally the living room) and the Black Hole Conference Room (study), we’ve built a website to introduce the house and all of its roles throughout the decades.

As a recent Caltech alum, I feel personally connected to this project, which incorporates both Caltech history and cutting-edge planetary science (KISS is a well-known think-and-do-tank for space science research).  At the same time, it marks a significant transition in my life and career, from research scientist to historian of science and curator, and I’m very grateful for the experience.  It feels strange sometimes to be making this transition on the same campus where I’ve spent several years working toward a doctorate in science, but I have to remember that it’s also the campus where I “snuck away” to take classes in history and Latin and where I’ve spent countless hours organizing rehearsals and film schedules for student theater and The PHD Movie.  In some sense, I think I’ve always been in transition.

Perhaps that’s why the Tolman/Bacher House appeals to me as much as it does:  this house, too, has played many roles and captures a transition frozen in time.  Completed in 1926, the house served as a comfortable home for two Caltech families, the Tolmans and the Bachers, before becoming part of the campus – which, by that time, had grown to surround it – in 1988.  As the Tolman/Bacher House Curator, I’ve tried to identify and juxtapose objects (photographs, newspaper clippings, letters, notes, etc.) that present the story of the house throughout the different eras of its history, the hope being that through this narrow lens, visitors and readers might view a little slice of Caltech’s past.  Standing in the original house and looking across the courtyard to the newly-dedicated Keck Center, both the past and the future feel close enough to touch.

photo 2 (1)

The study (now the Black Hole Conference Room) was added by Richard Tolman in 1936.

photo 1 (1)

The living room (now the Oort Cloud Lounge) was part of the original house, which was completed in 1926.

Posted in News, Reflections | 2 Comments

Catching up with #TalkNerdy

Over the weekend, I sat down with Cara Santa Maria, an amazing science communicator (just check out her website) to chat for a bit on her podcast, Talk Nerdy.  To be honest, I was surprised Cara asked me to be on her show (which, aside from me, has an impressive guest list!), but we ended up having a really interesting conversation about the Moon, impact craters, history of science, women in STEM, and surviving grad school.  If you have 90 minutes to spare (sorry, we went into overtime!), you can listen here.

We touched on a lot of different topics, and I thought it would be good to gather some resources on a few of them, in case anyone wants more information and to clarify anything I wasn’t very clear on.  If anyone has additional links to send my way (this is by no means exhaustive), feel free to leave a comment or tweet @trueanomalies, and I’ll add it!

Here are some things we talked about:

Planetary Science: what is it?  My standard definition, if you can call it that, is “take whatever kind of science you do (astronomy, geology, chemistry, etc), just apply it to planets – you’re a planetary scientist!”  The interdisciplinary nature of planetary science is one of my favorite things about it, even though can end up confusing people because it encompasses so many kinds of research.  Many of my colleagues work with telescopes and go on observing runs, while others use mass spectrometers to analyze meteorite samples.  My research relies on models and spacecraft data, so I’ve spent most of my time in graduate school in front of a computer – less exciting to be sure, but it has its charms too.

The giant impact hypothesis: How did the Moon form? We don’t know, but the current best guess is that a roughly Mars-sized body collided with the Earth not too long after its core formed, spraying material (mostly from the outer parts of the Earth) into orbit, which ultimately would have coalesced to form the Moon.  Here’s a computer simulation showing the standard scenario (related paper here):

Why do we think something like this might have happened? Because this hypothesis does a better job than others at accounting for the observations we have at the moment:  the current dynamical configuration of the Earth and the Moon (and their total angular momentum – see below), the chemical properties of both bodies, and the lower density of the Moon compared to the Earth.  Here’s a recent article that goes into some detail about that and introduces a slightly different hypothesis, charmingly called the Big Splat.  This piece points out an interesting wrinkle in this whole giant impact story: there are many different variations on a theme, and the particulars of the collision scenario (how big was the impactor? what angle did it arrive at? was the Earth rotating? how fast?) produce different outcomes that may help us figure out what actually happened.

Angular momentum & the Earth-Moon system:  The Moon is getting further away, the Earth’s rotation is slowing down, and these events are directly related through the conservation of angular momentum.  Here’s astronaut Mike Fossum demonstrating this principle for a single body (his actual body):

By extending his arms, he increases his moment of inertia about the vertical axis (at least, vertical with respect to the camera) and his angular velocity slows; the spinning speeds up again when he brings his arms in.  Similarly, the Earth and the Moon have a shared angular momentum budget, so when the Earth loses rotational angular momentum (which happens because the Moon raises tides – solid body tides, not just ocean ones – and then pulls more strongly on this tidal bulge, against the direction that the Earth is rotating), the Moon has to gain angular momentum, moving outward in its orbit.

http://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment

All of this  can be predicted mathematically and is not at all unique to our Moon – tidal evolution happens everywhere.  What’s really cool is that we can actually measure the rate at which the Moon is receding in its orbit.  The Apollo astronauts left several retroreflectors on the surface, which make it possible to shine a laser at the Moon and actually detect the reflection (this is a hard measurement to make, despite how easy it looks on TV).  The travel time of the laser pulse yields a very accurate measurement of the distance to the Moon, which is growing at a rate of a few centimeters per year, and this steady outward spiral is directly tied to the increase in length of day, which we tend to notice every now and then when a new leap second is added.  Everyone and everything on our planet is part of the system too, so in theory our angular momentum trades off with that of the Earth and Moon, but we’re too small to make much difference.

What is a barycenter? It’s the center of mass of an n-body system around which each body orbits.  If we consider just the Earth and Moon, the center of mass is very close to the Earth’s center, because it’s so much more massive: more than 80x!  So it’s almost true that the Moon orbits the Earth, but they actually both orbit the barycenter.  For Pluto and its moon Charon, which are much closer in mass (Pluto is ~9x more massive), the barycenter lies outside of Pluto altogether.  Here’s a handy animation:

http://en.wikipedia.org/wiki/Charon_(moon)#mediaviewer/File:Pluto-Charon_System.gif

Was there a Late-Heavy Bombardment? …Maybe? Generally speaking, there were many more collisions happening early on, when the planets were forming and sweeping up solid material, than there are now, and this impactor flux has decayed smoothly and exponentially over time.

http://www.psrd.hawaii.edu/Jan01/lunarCataclysm.html

But many of the Apollo samples that were brought back and radiometrically dated suggested that they formed at exactly the same time:  3.9 billion years ago.  This potential spike in the cratering rate (especially for the large, old lunar basins) is called the Late Heavy Bombardment, and whether it really exists or not is a topic of ongoing debate.  If it did happen, then it provides an important constraint for dynamical models of solar system formation, which have to explain the sudden cataclysm in addition to other key solar system characteristics, like the mass and structure of the Kuiper Belt.  For example, the Nice Model (based in Nice, France) proposes a scenario in which the giant planets formed somewhat closer to the Sun and evolved to their current positions (sometimes smoothly and other times abruptly) due to gravitational interactions with each other and with the planetary disk they formed in.  Here’s an animation showing a couple of potential scenarios simulated with the Nice Model:

Planetary migration can happen through several different mechanisms, and nobody knows for sure what combination (and timing) might have produced our solar system.  What’s even weirder (and more exciting!) is that other solar systems discovered so far don’t look much like ours.  The more we find out about other planetary systems and the outer reaches of our own, the more clues we’ll have to understand how our solar system got to be the way it is and how planets form throughout the universe.

That’s all I’ve got for now! Thanks, Cara, for having me on Talk Nerdy last weekend!

Posted in Extra Credit

Exciting times!

Last Friday, I successfully defended my planetary science thesis in front of my thesis committee, friends, and family – I am a doctor at last!

DefensePics

I say “at last” because it’s been quite a long time coming, really.  I arrived in Pasadena in August of 2007, having just graduated the previous June.  If I were to do it all over again, I would probably take some time off before starting grad school (and I would recommend it in general), but in retrospect, I’m glad that I didn’t.  I can’t regret the unexpected things that have come up over the past several years (to name a few: theater projects, movie producing, science communication opportunities, history of science research) that almost certainly would not have fallen out the same way if I’d changed my path, or even just delayed it by a year.

Looking ahead, I’m excited to remain at Caltech to write up for publication my research into the history of impact crater studies.  While I had originally intended to include this work as an addition my planetary science dissertation (since Caltech as an institution cannot grant any degrees in the humanities), after much careful thought, I have decided that this path forward will be more fruitful.  I am therefore at an interesting point in my trajectory (whatever it is).  I’m immensely proud of the work I’ve done in planetary science on cratered terrains and lunar surface roughness, and I look forward to publishing the bits that haven’t been published already in the coming months.  At the same time, I am so looking forward to concentrating on the history side of my research.  There’s plenty of work to do, but I’m ready for it – I have an exciting summer ahead of me!

Posted in News, Reflections

Taking “No Snark” to the Next Level

Historical figures briefly previewed in the first episode of Cosmos - can you name them all?

The first four episodes of the new Cosmos reboot have now aired,1 including a few somewhat problematic animations involving Giordano Bruno, Isaac Newton, Robert Hooke, and William Herschel.  I won’t try to summarize here the many responses that these portrayals have prompted, although many of them make for fine reading.  Instead, I want to talk about a different kind of response, a creative one.

I started this blog at the end of 2012 because I was in the middle of helping to launch PHD TV – a collaborative spinoff of PHD Comics that focuses on web videos – and I found myself with the opportunity to create a new thing, something I hadn’t seen before in the online video environment:  a history of science web series that could be entertaining without sacrificing historical complexity and could explain scientific concepts without oversimplifying how we came to our present understanding.  That’s hard.  Really, really hard.  Let me be the first to say that my attempts so far have not quite hit it out of the park, although I am proud of them and I’m excited to tweak things to see what will make future episodes better (after I graduate! Priorities.).  I’m going to keep trying, and I would like to see more others try too.

That’s the essence of the “no snark” attitude I tried to convey in my post about Giordano Bruno a few weeks ago.  Since I joined Twitter, I’ve seen several flare-ups between (generally speaking) scientists and historians, but more often than not, I’ve seen someone in the the history of science blogging community take a scientist or journalist to task for spouting irresponsible history, usually to little effect.  It’s like the MIT/Harvard rivalry over here! 2 3

Why does it matter? Cosmos has sparked a lot of conversations about history of science in the last few weeks, and that’s a good thing.  It’s an opportunity for historians to demonstrate to scientists and science communicators why it matters to get the history right, and (more importantly!) what it means to do history in the first place.  Coming from science myself, I know that this is not self-explanatory, and I’ve gotten my fair share of blank stares when I mention my history of science work.  I’m trying to get better at these conversations, to get to the point of what it’s all about – we study how people SCIENCE, guys!4 – and to dispel the idea that we’re all working on lists of dates and facts waiting to be inserted on a blank timeline somewhere (No.).

Until the science community – scientists, engineers, science communicators, journalists, movie consultants, writers, etc. – know what it is that historians actually do, there won’t be much incentive to include our perspectives and enlist our expertise in programs like Cosmos.  We should be making it easier on them!  As satisfying as it is tear apart shoddy history (and it is oh so satisfying!), complaining alone isn’t going to change anyone’s mind about the value of historical work to science communication and public appreciation of science.  So, what do we do?

In my opinion, creativity is always the answer.  We should be creating alternatives to the Cosmoses (Cosmoi?) out there, not just trying to tear them down.  It’s incredibly hard to balance entertainment with accuracy, catchiness with nuance.5 We should try to do it ourselves before (or in addition to) criticizing, and if we succeed, the world (or at least the internet) will be a little bit richer for it and the Seth MacFarlanes of the world will have a little more to go on when it comes to hiring consultants.  I imagine an ecosystem of resources that viewers could turn to after watching an episode of Cosmos:  snarky blogposts coexisting with narrative podcasts and snappy video explainers of key ideas.  If there’s a problem with how the stories of science past are being told, the solution is to tell better stories.

Of course, that’s all easier said than done, considering the limited time and resources any given person has to devote to “extra” activities like I’m suggesting, but every little bit helps.  Institutions who create YouTube channels (e.g., the Chemical Heritage Foundation) are moving in the right direction, and the new co-curated Twitter effort @WetheHumanities is a great step toward making work in the humanities more transparent and more accessible to the public.  The network of history of science bloggers is always growing, and it’s good to see the #histsci and #histtech hashtags used to continue conversations over the important issues that Cosmos, in all its glory, has started.

Let’s keep these conversations constructive! And creative too.

  1. The image shown is a collage of screenshots from the first episode, which briefly previewed several historical animations.
  2. Sorry MIT, but you know Harvard doesn’t care!
  3. Or the Caltech/MIT rivalry for that matter…
  4. …and what does it mean to “science” (and to whom) and who’s paying the bills and what kinds of things did people do to learn about the natural world before that was a word, etc.
  5. See, for example, this excellent post on the challenges faced by science museums by Professor Ludmilla Jordanova.
Posted in Extra Credit, Reflections

Want to know more about Giordano Bruno?

[Updated 8:30am (PST), March 14]

Last night the new COSMOS series aired on FOX and National Geographic channels, hosted by the one and only Neil DeGrasse Tyson and rolled out in style by producer Seth MacFarlane.  Roughly a quarter of the 43-minute program was devoted to the story of Giordano Bruno, an Italian monk and philosopher who espoused heliocentrism and an infinite universe and was burned at the stake by the Inquisition in 1600.  It’s a compelling story and the animation is really great (plus, the part of Bruno is voiced by MacFarlane himself!).  You can watch the clip here, and I recommend that you do.  Go ahead, I’ll wait =)

Pretty epic, right? Of course, you can only fit so much into 11 minutes, and as with many other popular retellings of science history, nuance isn’t high on the priority list.  But hey, Giordano Bruno was trending on Twitter last night, and that’s pretty cool! So rather than trying to tear this apart and tell you what’s wrong with it, I’d like to just gather some resources for anyone curious to go beyond the story that COSMOS tells.  No snark, just more cool stuff to fill your brain, if you want.

Now, Renaissance philosophy is not my field of study and I’m really cautious about wading in over my head, so I absolutely welcome corrections or contributions to what I’ve gathered here.  Don’t be shy (but please keep it respectful)!

First off, did anyone recognize the “dome of stars” that Bruno was stuck inside (24:21)? That awesome imagery is based on an illustration from Camille Flammerion’s 1888 book, The Atmosphere: Popular Meteorology.

flammerion

Much like COSMOS, Flammerion uses the illustration to describe past views of the Earth in relation to other celestial bodies: “Our ancestors imagined that this blue vault was really what the eye would lead them to believe it to be.” Did it have anything to do with Giordano Bruno? Not specifically. But it’s a pretty compelling visual device for this particular story.

Next up: “I spread confident wings to space and soared toward the infinite” – did Bruno really say that? Yes! Well, pretty much.  Here’s the whole sonnet (a slightly different translation by Arielle Saiber):

Who adorns me with plumes and courage?
Who has me fear neither fate nor death?
Who broke those chains and those doors
From which few rarely escape?
Ages, years, months, days and hours—
daughters and weapons of time—and that court
against which neither steel nor diamond has power:
these have protected me from the fury of the foe.
Thus with confident wings I enter the air.
I fear not obstacles of crystal or glass,
as I slice the heavens and rise toward the infinite.
And while I ascend from my globe to others,
And I pierce through the eternal field,
That which others saw from afar, I leave far behind me.

So that’s cool.  And a little confusing.  What “court” is he talking about? Who is the “foe”? This is where knowing a Bruno scholar would come in very handy (if you are one, please get in touch! I would like to know more).  Parts of Bruno’s writings seem very well adapted to the “martyr-for-science” role that we seem to really really want him to play…and others not so much.  Here’s a short overview of his works and philosophy (jump to p. 315) to help situate things.  He wasn’t executed specifically for his cosmology (although this is a topic of debate still); his belief in the plurality of worlds was just one of eight charges the Church laid at his door.

So…was he a scientist? No, as Tyson rightly states.  His views were philosophical speculations, not based on empirical observations – and anyway “science” isn’t an applicable term for what anyone was doing in the 16th century.  He was also not the nice-mannered, doe-eyed dissenter that COSMOS portrays, but a pretty difficult human being to get along with, albeit probably a more interesting one!

Some have wondered whether the show chose the wrong hero for their first episode, suggesting that perhaps English astronomer Thomas Digges would have been better, since he did much to bring Copernicus’s works to the English-speaking world and posited an infinite universe as well.  I would love to know more about Digges, and William Gilbert too (another interesting figure!), but isn’t this sort of the wrong question?  These people didn’t do what they did for our benefit, after all – they were each a product of their time and place.  As Becky Higgett says (more elegantly than I could):

Historical figures who lived in a very different world, very differently understood, cannot be turned into heroes who perfectly represent our values and concerns without doing serious damage to the evidence.

For Bruno to perfectly fulfill the hero role, we inevitably have to pick and choose which details of his life and philosophy and writings we present, because he had different concerns and values than we do – he literally lived in a different world.  I’d argue that we should stop looking for the perfect hero figure from history to champion our modern concerns and instead get to know them on their own terms.  But that’s just me.

Incidentally, if you do want to know more about Digges (and how he and Kepler and Galileo thought about and interacted with Bruno’s ideas),thonyc has put together a blow-by-blow response to Cosmos writer Steven Soter’s defense of the Bruno cartoon that’ll get you up to speed.

COSMOS presents a compelling story, but it’s a vastly simplified one.  I’m happy to see people excited about history of science, and I hope at least some of them will want to dig deeper.  I wonder what will happen in next week’s episode!

[I have to go now, since I have BILLIONS and BILLIONS (sorry, Carl) of other things to do for my actual research, but I have a few other loose thoughts floating around that I'd like to add here later today, and of course I'd love to know what others out there have to say!]

 

Posted in Extra Credit

Ocean180 & the Amazon River Plume

Here is the story of two microscopic creatures, caught between life and death, who together bring life to an entire ocean.

That’s the opening of the video abstract that I recently put together with Dr. Laurence Yeung and Nic Perez for the Ocean180 Video Challenge – an outstanding new contest for ocean scientists to bring their academic work to a middle school audience.  The basis of the video is Laurence’s 2012 paper, Impact of diatom-diazotroph associations on carbon export in the Amazon River plume (.pdf here), which takes a look at a pair of microorganisms that help each other get what they need to survive.  By working together, they turn a barren part of the Atlantic ocean into a buffet.  I had a great time animating to Nic’s epic voiceover, and I learned a ton about an entirely new field – plus, we took 2nd place in the contest! Definitely an all-around win for everyone.

Posted in Episodes, News

Errors and expertise

I recently came across a funny little article called “Journalists’ Ideas of the Moon’s Phases” in the Oct. 1934 issue of the Journal of the British Astronomical Association.  Looking through the index, I happened to glance at the title, and immediately I knew what this had to be.  My snark radar was tingling, and I was right.

Journalists-2

This article struck me because it’s so similar to the kinds of things I see today, all the time.  I haven’t seen Gravity yet, for example, but I already know what’s wrong with it because Neil DeGrasse Tyson sent out a series of tweets pointing out errors in the science.  Tyson is now notorious for calling out questionable science in movies and on TV, having pushed director James Cameron to fix up the night sky in Titanic, and having teased Jon Stewart for his retrograde-rotating Earth in the opening credits of The Daily Show.  His argument  is a simple one: it’s not hard to get the science right, so why not err on the side of caution and do your homework?

That’s exactly the argument that historian of science Thony Christie made against Tyson a few months ago when Tyson incorrectly tweeted that “the symbol ‘lb’ for pound comes from an abbreviation of the constellation Libra, the scales.”  In fact, the symbol does come from the Latin word “libra,” but that word has two meanings.  The relevant one is a Roman standard of weight, while the other meaning, “scales,” became the namesake of the constellation and has nothing to do with the abbreviation.

That might sound like nit-picking, but is it really all that different from pointing out that the Earth rotates backwards in the intro to a Comedy Central show?  The plea is the same: it’s not hard to consult an authority1 on the subject, so why not do it?

In all of these cases, expertise and authority are at stake.  Who gets to speak about certain topics, and in which circumstances and by whom are they believed? I think it’s understandable to be upset when a public figure misrepresents a fact about which you have some claim to expertise.  When the BBC Science Club promotes a cute video about the history of physics that has very little actual history in it, or when internet science headlines sacrifice truth for sensationalism, or when a fake documentary on mermaids barely admits that it’s fake, or even when the phases of the moon are reversed in a 1934 motor oil ad, someone – a scientist, a historian, whoever – who could have contributed a nuanced, fact-checked perspective based on years of experience (and maybe helped to spread a little solid knowledge around) wasn’t consulted.  That’s frustrating.

It’s also, probably, unavoidable.  Whether it’s scientists vs. journalists, or historians of science vs. scientists or popular writers vs. academics, authority in a given subject will always be contested, and all of these parties have different goals in mind when they write or speak or film, etc.2  That doesn’t make it less annoying to hear shoddy history or flimsy science repeated online or in the media, but it does prompt me to think carefully about how to respond.

Call-outs and tear-downs are often satisfying, but sometimes I find the negativity to be overwhelming.  I know it’s not easy (especially since nuanced pieces aren’t nearly as easy to share as blunt tell-you-what-to-think memes and myth-busting) but I’d take a thoughtful, upbeat, constructive teaching-moment approach over a snarky rebuttal any day.  I’m probably being naive here, but if you don’t like what’s out there in the ether, why not add an alternative?

I know this is already a topic of discussion in the history of science blogosphere, and my own experience tells me that scientists and historians of science generally have very different attitudes toward each other.  I’m told there are tensions between historians of science and historians in general too (and I expect I’ll encounter more of that in the future).  Academic disciplinary tensions are one thing, though; the popular arena is quite another.  It’s a big exciting internet out there, and it’s pretty easy to lend your voice to it, or at least to get started.  Just keep in mind what kind of voice you want to add to the mix.

  1. thonyc suggests any etymological dictionary or even Wikipedia
  2. I can complain all I want, for example, that The Big Bang Theory discourages girls from going into science, but Chuck Lorre didn’t set out to inspire young female scientists – he set out get lots of ratings.
Posted in Reflections