Thursday, July 30, 2015

How the Earth's Crust is Born: Marie Tharp "girl talk" and the Mid-Atlantic Ridge

Marie Tharp and the Mid-Atlantic Ridge Linocut
Marie Tharp and the Mid-Atlantic Ridge,
9" x 12" linocut on Japanese paper, by Ele Willoughby, 2015
Happy birthday to American geologist and oceanographic cartographer Marie Tharp (July 30, 1920- August 23, 2006), whose pioneering, thorough and complete ocean floor maps made with her partner in science Bruce Heezen revealed the Mid-Atlantic Ridge. The mid-ocean ridge itself, based on their 1957 physiographic map, is illustrated behind her, along with the sort of echo sounder or precision depth recorder tracks she used, in front of her.

Tharp had struggled to find the the right university major; she wanted something she could do, and enjoy, but there were not many options for women in her day. More opportunities opened up during WWII and she took the chance to return to school and study geology and then math. Looking for something challenging (but not tedious) she contacted Maurice 'Doc' Ewing at Lamont-Doherty Earth Observatory at Columbia, who hired her to draft data, including the thousands of echo sounder profiles they were gathering. Women were still not allowed to participate in research cruises, but they could work with the data. Before long, Heezen came to Lamont and required so much drafting work that Tharp worked exclusively with him.

Scientists once imagined the ocean floor as a largely featureless plain. Early depth measurements were taken with lead weights (such as canon balls) and a whole lot of rope! As early as the late 19th century, such laboriously collected datasets began to hint at a broad rise in the centre of the Atlantic. By the mid 20th century, there was a push to try and map these submarine mountains.

Tharp spent months painstakingly "plotting, drawing, checking, correcting, redrawing and rechecking" profiles of the North Atlantic. The ship tracks across the Atlantic were a sparse web, but when Tharp compared half a dozen more or less parallel transects she noticed no only the general similarities of the ridge, but a V-shaped notch in the centre of all the profiles. She suspected they coincided because they indicated a rift valley all along the ridge crest. The early ideas about plate tectonics or the "continental drift" theory were still quite controversial and unpopular. Heezen dismissed Tharp's observation as "girl talk" for looking too much like continent drift - as in fact it was indeed a vital piece of the plate tectonics puzzle. We now know that surface of the Earth is itself a jigsaw puzzle of pieces known as tectonic plates, jostling one another at a stately, geological pace. Mid-ocean ridges are underwater volcanic mountain chains which roughly bisect all ocean basins. They are all cut by a rift valley which is the spreading centre. These rifts are where new crust is born, pushing upwards and outward. This drives the two plates on either side slowly apart over geological time. On our own timescales of everyday life, we notice the bumps in this slow ride: the sporadic earthquakes, rather than the slow creep (though today, we can meticulously measure both).

Tharp believed the rift was real though her contour maps hadn't convinced Heezen. In 1952, they began working on physiographic maps, which would show seafloor topography as if you were flying just above it, and the water were drained away. These had the advantage of really giving a sense of the variety of geology, from plains to mountains, seamounts to trenches. Also, unlike detailed contour maps, physiographic maps were not US Navy classified information, so Tharp and Heezen would be able to publish what they produced. Further, they were beginning to gather much better precision depth recorder data, which revealed far more features, along with better navigation to plot ships' positions along tracks more accurately. A second project in their research group involved plotting earthquakes, and Heezen insisted they work at the same scale. Heezen then noticed that ocean earthquake epicentre data also formed long lines - and in fact, when one map was placed above the other on a light table they found the earthquakes formed near continous lines along the Mid-Atlantic ridge right where Tharp had indicated there was a rift valley. Using the earthquake data to extrapolate and plot the rift position where there was no seafloor sounding data, they found that the rift extend landward into the Rift Valley of East Africa - a well-known, easy to observe terrestrial rift valley. Heezen was then convinced. They had discovered a worldwide mid-ocean ridge system, tens of thousands of kilometres long. Tharp was able to mine existing data to show the Mid-Atlantic Ridge extended to the south Atlantic and found similar features in other oceans. These all similarly lined up neatly with earthquake epicentres. Ewing and Heezen announced their findings in 1956. In 1957 Tharp and Heezen published their North Atlantic physiographic map; I've shown my version of their map behind her. The ridge snakes from top to bottom (north to south-south-west), above and almost mimicking the line of her arm.

They continued this work, extending to other oceans over the next 25 years, ultimately producing detailed physiographic maps of the world oceans. Their pioneering work mapping the oceanic plate boundaries, and showing their clear alignment with seismic data helped fuel the revolution in geology and geophysics, the paradigm shift of plate tectonics.

Tharp's work was largely in the background during her university career, though she won a number of prizes during her retirement and has continued to gain posthumous recognition for the importance of her work and observations. I was very pleased to see her recognized recently in Neil DeGrasse Tyson's Cosmos reboot. I want to bring her incredible insight and excellent work to a wider audience as both artist and marine geophysicist myself.

(cross posted from the minouette blog)

Wednesday, July 15, 2015

Jocelyn Bell Burnell and the LGM-1

Jocelyn Bell and the LGM-1
Jocelyn Bell and the LGM-1, linocut portrait by Ele Willoughby 2014

Happy birthday to astrophysicist Jocelyn Bell Burrell (born, 1943), who discovered pulsars! As I wrote previously:

In November, 1967, Jocelyn Bell (Burnell) was just a graduate student when she discovered the first radio pulsar (or pulsating star), a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. This radiation (light in the radio frequency band) can only be observed when the star is point towards us; so, like the light from a distant lighthouse, it appears to pulse at a precise frequency. She had been working with her supervisor Antony Hewish and others to construct a radio telescope to study quasars (quasi-stellar objects which emit radio waves). She noted some "scruff" on her chart-recorder, and then that the pulses were incredibly regular, occurring every 1.337 seconds. Hewish was initially scornful and insisted the regular pulses must be noise from a human made source. He first dubbed this object, emitting with such regularity 'LGM 1' for "Little Green Men 1", a playful joke about their uncertainty about what could emit radiation so regularly - obviously it could only be a communication from extraterrestrials hahaha! Only after she found other such sources, in different places with different frequencies, were her colleagues convinced and this lead to the development of the pulsar model. It is now known PSR B1919+21.

The 1968 paper announcing this discovery in Nature has five authors, lead by Hewish, followed by Jocelyn Bell. In 1974, Hewish won the Nobel Prize for this discovery, along with fellow radioastronomer Marlin Ryle). Jocelyn Bell was not included as it was assumed that the "senior man" was responsible for the work. This was controversial and has been condemned by many leading astronomers like Fred Hoyle (who with Thomas Gold was first able to explain the signals as due to a rapidly rotating neutron star). Jocelyn Bell Burnell herself has stated she was not upset. Bell Burnell has a great on-going career and won many honours after her impressive start, but her exclusion from the Nobel win, based on her own research strikes me and many others as one of the more blatant and egregious examples of gender bias in the selection of Nobel prize recipients.

Read the full post about how her beautiful dataset itself has lead a life of its own as a cultural meme.

Tuesday, June 23, 2015

The Enigma of Alan Turing

Alan Turing, linocut 2012, by Ele Willoughby

I've written previoulsy about Turing, for the centenary of his birth. To celebrate his 103rd birthday, I'm sharing my portrait of him complete with a schematic of the Enigma machine. I had long thought to portray Alan Mathison Turing, OBE, FRS (23 June 1912 – 7 June 1954), British mathematician, cryptanalyst, computer scientist, prophet and hero, but was stumped. My scientists are shown with images of something quintessential to their science, or the reason they are famous (or should be), but Turing had so many accomplishments, it wasn't obvious what to portray or how. Turing is the subject of this year's biopic The Imitation Game. You might recall his portrayal in Neal Stephenson's 'Cryptonomicon'. I was introduced to him many year ago by Douglas Hofstadter's 'Gödel, Escher, Bach'. You may also be familiar with the Turing Test or at least its portrayal in Blade Runner. Turing foresaw not only that machines might quite likely develop the capacity to think (after all, our brains are only made of matter, and complex systems of neurons, which either fire or not, much like an electronic switch), but that we needed an objective, double-blind test to determine whether something/someone was able to think, as early as 1950, when most people were only dimly aware of the existence of any sort of computer. But Turing quite literally defined what we now mean by computation itself (with his concept of Turing Machines) back in 1936. During the WWII he worked as a codebreaker and invented the device which was finally able to crack the notorious German cryptographic Enigma machine (in its more complex later incarnation)! His work undoubtedly saved many lives, and today we recognize him as a genius and a hero. In my print, I've included a simplified diagram of the mechanism behind the Enigma with its rotors or scramblers which acted as monoalphabetic substitution ciphers, literally scrambling letters at each turn. During, his all too short life, he also made important contributions to mathematical biology and explaining morphogenesis (the biological process that causes an organism to develop its shape) and the existence of Fibonacci numbers in biology. To indicate this later work, I've made the pattern of his tie look like the sort of Turing pattern produced by reaction–diffusion systems. This work presaged much later work in chaos theory.

Tragically, he lived in a time even more biased and bigoted than our own. Rather than recognizing the magnitude of his contributions to society during his lifetime, he was prosecuted for his homosexuality (still illegal in Britain in 1952) and forced to undergo chemical castration. He died two years later, after eating a cyanide-poisoned apple (determined by the coroner to be a suicide - something his mother vigorously denied). It is truly abominable they way he was treated; while we can't address the past injustice we can remember, recognize and celebrate his remarkable achievements today.

There are many serious looking photos of Turing. I chose one of him smiling as inspiration for this portrait. He clearly enjoyed his work, and had a sense of humour (evident in the silly names he gave mathematical techniques he discovered), so I chose to remember him laughing.

Sunday, May 31, 2015

Chien-Shung Wu & the Violation of Parity

Mme Wu
Madame Wu and the Violation of Parity, 2nd ed. linocut, 2012, Ele Willoughby

Happy birthday to Mme. Wu! Chien-Shiung Wu (May 31, 1912- February 16, 1997, Chinese-born American physicist, whose nicknames included the “First Lady of Physics”, “Chinese Marie Curie,” and “Madame Wu”) came up with a truly beautiful experiment to test whether the weak force conserves parity (whether beta decay would be the same if reflected in the mirror). In my print on the left I show Mme. Wu in her lab and a schematic diagram in the box of her beautiful experiment. On the right I show her reflection, as in the mirror, and in the box I show the mirror reflection of the experimental set-up and the shocking result, that the reaction is not the mirror opposite.

In 1956, theoretical physicists Tsung Dao Lee and Chen Ning Yang suggested that perhaps the weak force might not be the same 'through the looking-glass'. The idea that the "Law of Conservation of Parity" might be broken was hard to believe. The laws of physics are the same in the mirror for anything else. Face a friend, as in the mirror. If you drop a pencil from your right hand, and your friend mirrors you and drops a pencil with his or her left, the pencils will fall at the same rate. This is because Parity is conserved by the force of gravity - as it is with the electromagnetic force and even the strong (nuclear) force within atomic nuclei. Lee and Yang pointed out that no one had checked to make sure that the weak force, which controls beta decay in radioactive materials, also conserves parity. Lee convinced the brilliant experimentalist to test this.

Madame Wu did a subtle and technically difficult experiment with her collaborators which is shown schematically in the print. She took Cobalt-60 (shown as the cobalt blue sphere in the box), which is radioactive. Its neutrons spontaneously give off electrons and become protons. The electrons are the tiny blue dots. On the left, we see that the Cobalt-60 in an electromagnet (a wire wrapped metal horseshoe with a source of power). Because of the spiral-wrap of the wire, we know that the North pole of the magnet will be on the bottom (you can figure this out by mimicking the curl of the wire with the fingers of your right hand and look at the direction your thumb points). It turns out that the emitted electrons are given off preferentially towards the North pole.

Next, she reversed the set-up as in the mirror. On the right you see the horseshoe and wire spiral reflected. If you use your right hand to check the direction of the magnet field, you'll see that it is the opposite way; the North pole is now on the top. It turns out that the electrons are preferentially emitted upwards toward the North pole. Thus, beta decay IS NOT the same in the mirror! Madame Wu showed that a "Law" of physics did not hold! This result was staggering and shocked the physics world. Lee and Yang won the Nobel prize for their theoretical work. Many physicists thought Mme. Wu should have been included in this win.

She won many honours for her incredible career. Wu took part in the Manhattan Project (she is believed to be the only Chinese person to do so) and literally wrote the book on beta decay. She was the first: Chinese-American to be elected to the U.S. National Academy of Sciences; Female instructor in the Physics Department of Princeton University; Woman with an honorary doctorate from Princeton University; Female President of the American Physical Society, elected in 1975; winner of the Wolf Prize in Physics (1978); Living scientist to have an asteroid named after her. She won many awards and fellowships including: the Research Corporation Award 1958; the Achievement Award, American Association of University Women 1960; John Price Wetherill Medal, The Franklin Institute, 1962; Comstock Prize in Physics, National Academy of Sciences 1964; Chi-Tsin Achievement Award, Chi-Tsin Culture Foundation, Taiwan 1965; Scientist of the Year Award, Industrial Research Magazine 1974; Tom W. Bonner Prize, American Physical Society 1975; National Medal of Science (U.S.) 1975; the aforementioned Wolf Prize in Physics, Israel 1978; Honorary Fellow Royal Society of Edinburgh; Fellow American Academy of Arts and Sciences; Fellow American Association for the Advancement of Science; Fellow American Physical Society. And I bet you hadn't heard of her! I'm trying to redress that.

Wednesday, May 27, 2015

There be dragons...

"Carta Marina" by Olaus Magnus Licensed under Public Domain via Wikimedia Commons.

What to do at the edge of known territory, or how to demark the gaps in data in any sort of data visualization - geographical maps in particular - has long been an issue we grapple with. Medieval and even Renaissance mapmakers famously decorated the unmapped regions of their maps with fanciful creatures. These creatures would not fit with our modern conceptions of science, but in fairness, were not necessarily complete fabrications, but actual attempts to document animals which had been described by early explorers, but unseen by the mapmakers, rather than simple mythological ornaments. It's also been argued that they intended to scare foreign fishermen away from certain waters and reflected the idea land creatures had a marine equivalent (sea dogs, sea cows, even sea chickens apparently - see the Tetrapod Zoology review of Sea Monsters of Medieval and Renaissance Maps). The early map of Scandinavia, the Carta Marina by Olaus Magnus (1490–1557), is a prime example of the sorts of fabulous creatures of the maps. You can find the same creatures, including the ziphius (a whale sized creature) porcus marinus (like it sounds, essentially a pig mermaid, or boar-whale perhaps an attempt to depict a sea lion), and the rosmarine (or boar-whale, a tusked creature perhaps derived from the walrus) on many other maps, often appearing to be copied or inspired by previous maps.
A ziphius sea monster eats a seal, while attacked by another monster
(detail of the 1575 edition of the Carta Marina by Olaus Magnus)

Toronto artist Bailey Henderson has done a magical thing. She's created a series of bronze sculptures, Monstorum Marines, depicting these creatures in full textured 3D. Each is coloured with pigments and acrylics. The texture both micmics the lines of woodcut maps, like the Carta Marina, and enhances further, creating a naturalistic yet fantastic creature.

A ziphius eats a seal while biten by another creature in naturalist Conrad Gesner's 1560 Icones Animalium 

Famous cartographer Abraham Ortelius's 1603 edition of his well-known Theatrum Orbis Terrarum map includes this tame whale with fearsome teeth, he calls the Steipereidur, explaining that it "fights other whales on behalf of fishermen."
Bailey Henderson,
Ziphius et Orca
Cold cast bronze, acrylic paint, powdered pigment
17 3/4 x 11 1/4 x 7 inches

Henderson writes,
Ziphius is based on a sea monster commonly depicted on renaissance and medieval maps. It was believed to cut boats in half with its sharp dorsal fin. Here sculpted in a life-like form. Creatures like Orca are based on whales, and were commonly depicted on maps in various forms.

I see a little Ortelius and Gesner, by way of Magnus in this sculpture.

Rosmarine, or boar-whale by Gesner, 1555
detail, Carta Marina (1575) by Olaus Magnus, including the rosmarine or pinniped with his tusks
Bailey Henderson, Pinniped,
Cast Resin, acrylic paint
11 x 4.75 x 4.75

Sea pig, detail from Olaus Magnus' 1539 Carta Marina. This purported creature was compared to heretics that "distorted truth and lived like swine" (according to Hanah Waters, "The Enchanting Sea Monsters on Medieval Maps" on
Of the sea pig, or hog, Olaus Magnus wrote, "Now I shall revive the memory of a monstrous Hog that was found afterwards, Anno 1537, in the same German Ocean, and it was a Monster in every part of it. For it had a Hog's head, and a quarter of a Circle, like the Moon, in the hinder part of its head, four feet like a Dragon's, two eyes on both sides of his Loyns, and a third in his belly inkling toward his Navel; behind he had a Forked-Tail, like to other Fish commonly."(via strange science)

Bailey Henderson, Porcus Marinus
Cold cast bronze, powdered pigment, acrylic paint
16 x 8 1/2 x 7 inches

Be sure to the rest of her portfolio, for other sculpture creatures and illustrations.

Wednesday, May 13, 2015

Inge Lehmann & the Earth's Solid Inner Core

Inge Lehmann print
Inge Lehmann, linocut, 8" x 8", by Ele Willoughby, 2011

Happy birthday to Inge Lehmann! Inge Lehmann (May 13, 1888 – February 21, 1993) was a Danish seismologist who first demonstrated that the Earth's core is not one single molten sphere, but contained an inner (solid) core, in 1936. She was a pioneer woman in science, a brilliant seismologist and lived to be 105, so I've selected her for my offering for the Mad Scientists of Etsy April challenge on earthquake seismology. Each is 8" (20.5 cm) square and printed in dark cyan and red-orange ink on white Japanese kozo (mulberry) paper.

We now know, as she first postulated, that the earth has roughly three equal concentric sections: mantle, liquid outer core and solid inner core. The crust, on which we live is merely a thin, um, scum really, on top of this slowly boiling pot. The only way to probe deep into the earth's core is to employ massive earthquakes, the waves they generate and the paths they follow. There are two main types of seismic waves used for studies of the globe, unimaginatively named Primary (or P, or compressional) and Secondary (or S, or shear). Imagine a glass of water with a straw; the straw will appear broken at the air-water interface, because light bends as it enters the water. Just like light travelling through different media, these seismic waves can bend, reflect or be transmitted at any boundary. The difference in physical properties between the mantle and outer core causes a P-wave shadow. (For S-waves, the shadow zone is absolute because liquids, like the outer core, do not support shear - imagine trying to cut water with a pair of shears and you can see this for yourself. Thus, no shear waves can make it through the outer core, and thus we can be certain the outer core is fluid). That means, the compressional waves from an earthquake can be recorded at seismic stations out to 105 degrees from an epicentre and then there is a zone which is in the core's shadow. Lehmann found that there were some late-arriving P-waves are much larger angles (142 to 180 degrees) which had been vaguely labelled 'diffractions'. She showed that these could be explained instead by deflections of the waves which travelled through the outer core at her postulated inner core boundary.

She later discovered a discontinuity in the mantle (confusingly also called the Lehmann discontinuity). She did important work well into her 70s.

When she received the Bowie medal in 1971 (she was the first woman to receive the highest honour of the American Geophysical Union), her citation noted that the "Lehmann discontinuity was discovered through exacting scrutiny of seismic records by a master of a black art for which no amount of computerization is likely to be a complete substitute...".

I think her accomplishment is downright astonishing. To have the exactitude to work with the data and the daring to neglect the irrelevant and offer up a simple, elegant - correct! - explanation is a rare and marvellous thing. To be the top of her field in 1936, when she was a pioneer for women in science and had to compete in vain with incompetent men (her words) is heroic.

I based my portrait on an earlier photo, to match the date of her phenomenal P' paper. I also show her model of the earth in red-orange ink, complete with mantle, inner and outer core, and travel paths for rays through the layers, including into the shadow zone.

Tuesday, May 12, 2015

Florence Nightingale; Nursing, Statistics and Data Visualization Pioneer

Florence Nightingale portrait
Florence Nightingale, 2nd edition linocut on kozo, Ele Willoughby, 2014

I confess that Florence Nightingale (12 May 1820 – 13 August 1910) wasn't on my shortlist of women in science I wished to portray. I felt a little like she was an old-fashioned heroine, from a time where if a woman wasn't going to be defined strictly as a person who served and cared for her family, it was okay if (and only if) she cared for other people. This bias was somewhat reinforced by my own family history: my mother is a nurse, her mother was a nurse, whereas I am a physicist. I know my grandmother wanted to be a pharmacist, and my mother felt her career options were school teacher or nurse. Plus, I take after my father's side of the family and have been known to have a vasovagal response to the mere description of medical procedures; I have a high pain threshold, but am squeemish, and faint like the rest of them. All of which means I partially define myself by not being a nurse. However, I was (luckily) commissioned to make a portrait of Florence Nightingale. The more I read, the more interesting she became to me.

Nightingale earned the nickname "The Lady with the Lamp" during the Crimean War, from a phrase used by The Times, describing her as a “ministering angel” making her solitary rounds of the hospital at night with “a little lamp in her hand”. The image was immortalized by Henry Wadsworth Longfellow's 1857 poem Santa Filomena in the stanza:

Lo! in that house of misery
A lady with a lamp I see
Pass through the glimmering gloom,
And flit from room to room.

So, I’ve shown Nightingale with her little lamp, based on contemporary photos and illustrations. But inventing modern nursing wasn't her only accomplishment. Taking up a profession, travelling to a war zone, nursing the wounded, taking on hospital administration and the training of a professional class of nurses weren't the only things she did which were so unusual for a woman of her time to do. It turns out that her father fostered her gift for mathematics, and she made significant contributions to statistics and data visualization too.

Behind Nightingale is her own ‘Diagram of Causes of Mortality in the Army in the East’ plotted as a polar area diagram – her own statistical and data visualization innovation, sometimes called a Nightingale Rose Diagram. It illustrates the causes of death in the military hospital she managed during the Crimean War. April 1855 to March 1856 is shown on the left and April 1854 to March 1855 to the right. When she researched the causes of mortality, looking back at the data, she saw clearly that the lack of hygiene was a far greater risk to soldiers’ lives than being wounded. The sections represent one month of data {J,F,M,A,M, J,J,A,S,O,N,D} for each month of the year. The green “wedges measured from the centre of the circle represent area for area the deaths from Preventible or Mitigable Zymotic diseases, the [yellow] wedges measured from the centre the deaths from wounds, & the [orange] wedges measured from the centre the deaths from all other causes. The […] line across the [yellow] triangle in Nov. 1854 marks the boundary of the deaths from all other causes during the month. In October 1854, & April 1855, the [orange] area coincides with the [yellow], in January & February 1856, the [green] coincides with the [orange]. The entire areas may be compared by following the [green], the [yellow], & the […] lines enclosing them.” This "Diagram of the causes of mortality in the army in the East" was published in Notes on Matters Affecting the Health, Efficiency, and Hospital Administration of the British Army and sent to Queen Victoria in 1858.

This experience influenced her later career and she campaigned for sanitary living conditions, knowing how dangerous unsanitary conditions can be to survival. She also made extensive use of similar polar area diagrams on the nature and magnitude of the conditions of medical care in the Crimean War, or sanitation conditions of the British army in rural India, to make such statistics transparent to Members of Parliament and civil servants who would have been unlikely to read or understand traditional statistical reports. This is an excellent example of how careful selection of how data is presented can influence whether the information is successfully communicated and how important that can be - occassionally even influencing people's survival!

In 1859, Nightingale was elected the first female member of the Royal Statistical Society. She later became an honorary member of the American Statistical Association.

Though her own opinion  of other women was often harsh, she has been credited with contributing to feminist literature with a book she wrote while sorting out her thoughts on her role in the world, including the essay Cassandra, which protested the over-feminisation of women into near helplessness. She helped abolish laws regulating prostitution that were overly harsh to women. She also clearly expanded the acceptable forms of female participation in the workforce.

This, and in particularly, the way she insisted on making decisions based on scientific evidence, and using data to save lives, makes her an apt addition to the women in science portrait series.


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