Note: Updated with quotes from Patrick Wagnon, ICIMOD
On April 18, an avalanche on Mount Everest killed 16 Nepalese guides. By the end of the month, 13 bodies had been recovered. The search for the remaining three was called off after conditions were termed too risky and difficult. On April 22, the Sherpa guides announced they would not work on the mountain as a mark of respect for their fallen colleagues. The climbing season on Mt. Everest for 2014 was closed.
The incident drew attention from around the world – as consternation aimed at the Nepalese government’s provision of insufficient compensation and as concern over the effects of climate change. Its capacity to be a rallying point for anthropogenic warming was bolstered after another avalanche on May 23 that killed one climber and two more guides, who were scaling Yalung Kang, a sister peak of Mt. Kanchenjunga.
Except that the April-18 incident wasn’t an avalanche, according to some glaciologists, climate change specialists and other scientists from the International Centre for Integrated Mountain Development (ICIMOD), Nepal. They issued a ‘Clarification on inaccurate media reports‘ on May 23, about a week after a conference on the Hindu Kush Himalayas cryosphere closed.
They attributed the April-18 tragedy to a serac fall, and explained how it was different from an avalanche.
“An avalanche requires a snowpack of sufficient depth with a weak layer, a sufficiently steep slope, and a trigger. In contrast, the 18 April tragedy on Mount Everest was the result of a different phenomenon called serac collapse. Seracs are large blocks of ice that are formed as a result of glacier fracture patterns and motion, and can fall or topple without warning.”
Thus, most of the time, there is no relationship between climate change and avalanche/serac risk.
Little to no link
According to Patrick Wagnon, one of the authors of the media clarification and a glaciologist at ICIMOD, “Serac falls are due to glacier flow and fracturation, and glaciers move down with gravity. Avalanche are due to snow falls, slope, and snow cover stability, and gravity is the main process to trigger avalanches.”
Going by the ICIMOD clarification, the April 18 avalanche that killed the 16 guides was triggered by a serac fall.
In the same statement, the scientists add, “Changes in the frequency of either avalanches or serac falls in the Everest region have not been definitively linked to climate change.” So further studies have to be done to establish the nature of the link between climate change and the frequency and magnitude of avalanches and serac falls.
Wagnon added, “As far as I know, no studies have been conducted so far to link climate change and serac falls or avalanches in the Himalayas, and very few in the Alps.”
However, Wagnon also cautioned that in some specific cases, glacier flow and associated serac fall can be modified by climate change. For an example, he referred to a case under study in the Mont Blanc area in France, where a serac barrier at 3,700 m, on the Taconnaz glacier, is dominating the town of Chamonix.
Such a glacier will be moving slowly because the its temperature keeps parts of it from melting. Since the amount of warming is sensitive to elevation, parts of glaciers at critical altitudes could warm up to close to 0° C and accelerate “from 1-10 m/year to 10-50 m/year”, precipitating a serac fall. On the Alps, the critical altitude above which the falls are likelier to happen is in the range of 3,500-3,900 m. On the Himalayas, around 6,000 m.
“But really, take care, it is in very few cases,” Wagnon concluded.
Thus, the corresponding ice reserves had dwindled by around 129 km3 in the same period. The report’s authors note that while the impact of climate change on avalanches and serac falls is not fully known, rising local temperatures affect different physical features to different extents. As a result, they write, smaller glaciers that sport a larger surface area, those at lower elevations and with less-sloping surfaces are more pliant to warmer climes.
At the same time, the authors of the report advised caution in the clarification. Between 1980 and 1990, they speculate that the rate of ice loss could have been overestimated by the misclassification of snow as glacier ice – a characterization that’s yet to be fully understood.
With the second largest air burst recorded in history, a meteorite exploded over the southern Ural region of Russia in February 2013 and crashed near the city of Chelyabinsk. During its journey through Earth’s atmosphere, it underwent intense heating, eventually glowing brighter than the Sun, and blew up with a bright flash.
The accompanying shockwave damaged over 7,000 buildings and injured 1,500. The crash disintegrated the rock into fragments.
When analyzing some of these fragments, scientists from the Tohoku University, Japan, detected the presence of a mineral called jadeite. Jadeite is a major constituent of jade, the hard rock that has been used since prehistoric times for fashioning ornaments. The mineral forms only under extreme pressure and temperature.
“Generally, jadeite is not included in meteorites as a primary mineral,” said Shin Ozawa, a graduate school student at Tohoku University and lead author of his team’s paper published in Scientific Reports on May 22.
The implication is that the Chelyabinsk meteorite, originally an asteroid, could have had a violent past leading to its undergoing immense heating and compression.
Piecing evidence together
“The jadeite reported in our paper is considered to have crystallized from a melt of sodium-rich plagioclase under high-pressure and high-temperature conditions caused by an impact,” Ozawa explained. Plagioclase (NaAlSi3O8) is a silicate mineral found in meteorites as well as terrestrial rocks.
The impact would have been in the form of the Chelyabinsk asteroid – or its parent body – colliding with another rock in space.
To arrive at distinct estimates of how this collision could have occurred, Ozawa and his colleagues connected two bits of evidence and solved it like an algebraic equation. In this case, the equations are called the Rankine-Hugoniot relations.
First, they observed the jadeite was found embedded in black seams in the rock called shock-melt veins. “They are formed by localized melting of rocks probably due to frictional heat, accompanied with shear movements of material within the rocks during an impact,” Ozawa explained.
The molten rock then solidifies due to high pressure. The amount of time for which this pressure is maintained – i.e. duration of the impact – was calculated based on how long it would have taken a shock-melt vein of its composition to solidify.
Second, they knew the conditions under which jadeite forms, which require a certain minimum impact pressure which, in turn, is related to the speed at which the two bodies smashed into one another.
Based on this information, Ozawa reasons the Chelyabinsk meteorite – or its parent body – could have collided with another space-rock “at least 150 metres in diameter” at 0.4 to 1.5 km/s.
The impact itself could have occurred around or after 290 million years ago, according to a study published in Geochemistry International in 2013, titled ‘Analytical results for the material of the Chelyabinsk meteorite’. It also reports that the meteorite is 4.4-4.6 billion years old.
Collision course
Ozawa’s results aren’t the end of the road, however, in understanding the meteorite’s past, a 4-billion-year journey that ended on the only planet known to harbor life. In fact, nobody noticed it hurtling toward our planet until it entered the atmosphere and started glowing.
Earth has been subjected to many asteroid-crashes because of its proximity to the asteroid belt between Mars and Jupiter. In this region, according to Ozawa, asteroids exist in a stable state. So violent collisions with other asteroids could be one of the triggers that could set these rocks on a path toward Earth.
Ozawa speculated that such events wouldn’t be uncommon. A report released by the B612 Foundation in April this year attests to that. It states that asteroids caused 26 nuclear-scale explosions in Earth’s atmosphere between 2000 and 2013. As The Guardianwrote, “the evidence was a sobering reminder of how vulnerable the Earth was to the threat from space”.
The difficulty in detecting the Chelyabinsk asteroid was also compounded by the fact that it came from the direction of the Sun. “If it had approached the Earth from a different direction,” Ozawa added, “its detection might have been easier.”
Thus, such collisions cause essentially random upheavals in our ability to predict when one of these rocks might threaten to get too close. By studying their past, scientists can piece together when and how these collisions occur, and get a grip on the threat-levels.
Gopalkrishna Gandhi’s lead in The Hindu, ‘An open letter to Narendra Modi‘, was a wonderful read – as if from the Keeper of the Nation’s Conscience to the Executor of the Republic’s Will. I’m not interested in scrupulous political analyses and Gandhi’s piece sat well with that, explaining so lucidly what’s really at stake as Modi gears up to become India’s 14th Prime Minister without fixating on big words, not that that’s wrong but they tend to throw me off.
However, Gandhi’s piece does have an awful number of commas in it and IMO they hamper the flow. Sample this.
“Why is there, in so many, so much fear, that they dare not voice their fears?“
The piece as such is 1,469 words long, has 82 sentences, about 17.91 words per sentence and 140 commas. That means a lot of sentences have at least one comma. In fact, there are only 11 sentences in which a comma has appeared exactly once; in every other sentence with a comma, there are at least two of them (excluding the opening and closing addresses).
Overall, there are 13 sentences with no commas. Remove them and the average number of commas per sentence comes to 2.02. Factor in the number of sentences with only one comma and that gives you 2.22 – the number of commas on average in each sentence with at least two commas.
This means almost 71% of sentences in the piece possess a sub-clause. I think that makes for clunky reading. Many people, especially those writing in Indian newspapers, have a tendency to use the comma to effect a pause while reading, mostly for dramatic effect, but the comma serves a bigger purpose than that. It breaks the sentence down into meaningful nuclear bits. For example, see the italicized bit in the sentence two lines above or below. That’s a sub-clause demarcated by commas. Remove it and the rest of the sentence, with the two ends brought together, still make sense.
Ideally, the number of commas should be comparable to the number of sentences, and definitely shouldn’t differ by an order of magnitude unless, of course, you’re composing something especially tricky, like this sentence. If you find you can’t avoid using too many sub-clauses, it could mean you’re not spelling things out simple enough.
If your sub-clauses are dominated by words like ‘however’ or ‘albeit’, it could mean you’re making many assumptions while constructing your arguments. If there are too many non-essential relative clauses, it could mean you’re trying to pack in too much information (usually in the form of adjectives).
Richard Feynman, the late Nobel Laureate in physics, was once asked by a Caltech faculty member to explain why spin one-half particles obey Fermi Dirac statistics. Rising to the challenge, he said, “I’ll prepare a freshman lecture on it.” But a few days later he told the faculty member, “You know, I couldn’t do it. I couldn’t reduce it to the freshman level. That means we really don’t understand it.”
Of course, these are just my thoughts, and most of them are the sort of things I’ve to look out for while editing The Hindu Blogs. I’d try to use commas only when absolutely necessary because they, especially when frequent enough, don’t just give pause but enforce them.
Update: Gopalkrishna Gandhi replied to my piece. Very sweet of him to do so…
Absolutely delighted and want to tell him that I find his comment as refreshing as a shower in lavender for it cures me almost if not fully of my old old habit of taking myself too seriously and writing as if I am meant to change the world and also that I will be very watchful about not enforcing any pauses through commas and under no circumstances on pain of ostracism for that worst of all effects namely dramatic effect and will assiduosuly [sic] follow the near zero comma if not a zero comma rule and that I would greatly value a meet up and a chat discussing pernicious punctuation and other evils.
Hans Rudolf Giger, the Swiss artist who conceived of the alien xenomorph in Ridley Scott’s Alien (1979), died on May 12 at the age of 84 in Zurich. Here was an artist who was not awkward, harboring no pretense of subtlety. Giger was an artist suckling on a vein of psychotic posthumanism like a fat, usurious pup. His influence on various artists and art-forms cannot be overstated. From Alejandro Jodorowsky to Ibanez, from Dune to Doom, from gamers to tattoo aficionados, Giger’s biomechanical fusion of metal, flesh and insipid monochrome was the perfect picture of the macabre.
It would be wrong to remember him for just Alien. The author of dozens of paintings, sculptures and lithographs as well, perhaps his most profound accomplishment was the surgical depiction of posthuman fetishes. His 1977 book Necronomicon, a compendium of his pictures, was breathlessly celebrated for the psychiatric grimoire that it was. At the same time, it was one of the first complete impressions of unhuman lifeforms – beaten in time only by H.P. Lovecraft’s Cthulhu Mythos from the 1930s – where creatures aspired not to be ape-like, not to present distended limbs in an effort to approximate familiarity, but were beings in their own right.
What better example of this idea than Necronom IV and V, the conceptual beings that inspired the xenomorph. The Necronom had no eyes, and only the mouth to give its face any semblance of being facial. At the same time, the way Giger assembled these beings into an iconoclastic portrayal of sanity – such as with Vlad Tepes (1978) and the dharmic horror that was Goho Doji (1987) – drew forth chills, sleepless nights and confused arousal from very-human adolescents. The faces in his paintings weren’t screaming. They were staring even while they were penetrated by translucent metal proboscises. They were existing for pain and confusion.
When Ridley Scott arrived for his first meeting at 20th Century Fox for Alien, he was shown Giger’s Necronomican. “I took one look at it,” he said, “and I’ve never been so sure of anything in my life.”
To look at them was to realize the composition of the human psyche was independent of the human body, that the human mind was frightened not by the disfiguration of familiarity – such as the image of a mangled corpse or by someone jumping out from behind the shower curtains – but by its reconfiguration. Giger put fear and gratification where they didn’t belong, and the product always had a sheen of otherworldly Gödelian inaccessibility. That even alien constructions could inspire empathy and distress was a disturbing revelation, if only for me. And no, I have not made it as a normal adult.
While cinema may have moved on from the genius of Giger, the best collaboration being The Last Megalopolis (1988) and the last Species (1995), he did not suffer from the same decline in prolificity or skill that artists are wont to after tinsel-town toss-outs. He seemed not to work toward the shock factor that the screen is adept at reproducing because his success lay in his ability to parallely evoke and inhere humankind’s tendency for abuse, a chronically relevant motif. Giger’s sculpture Birth Machine (1967) on display in the permanent museum dedicated to him in Gruyeres, Switzerland, stimulates this sensation of an existential vertigo, like the thematically similar Doodlebug (1997) by Nolan. Better yet, consider Aleph (1972), or Li I (1974), dedicated to Li Tobler, his partner from ‘66 until she killed herself in ‘75 – both potent with occultist interpretations.
Such images, rather experiments with the triggers of strangeness, populate the breadth of his work. Growing up in the Swiss town of Chur, where his father ran a pharmacy, Giger admitted to having been fascinated by dark alleys between buildings that he could see from his room’s window. He also had serial nightmares, and took to art first as therapy. No wonder then that his work is effortlessly visceral, drawing as it does from the inviting darkness that pervaded Chur’s alleyways.
In the April 3 issue of Nature, Joseph Mathai and Andrew Robinson published a Comment on the afflictions of scientific research in India – and found the interference of bureaucracy to be chief among all ills. Most of the writers’ concerns were very valid, and kudos to them for highlighting how it was the government mismanaging science in India, not the institutes mismanaging themselves. In the May 8 issue of the same journal, three letters in response to the piece were published, under Correspondence, which brought to light two more issues just as important although not that immense, and both symptomatic of mismanagement that appears to border on either malevolence or stupidity, depending on your bent of mind.
Biswa Prasun Chatterji from St. Xavier’s, Mumbai, wrote about the “disastrous” decoupling of research and education in the country, mainly as a result of newly created research institutions in the 1940s and 1950s. These institutions led bright, young students away from universities, which as a result were parched of funds. The research bodies, on the other hand, fell prey to increasing bureaucratic meddling. Chatterji then points to an editorial in the November 1998 (vol. 75) issue of Current Science by P. Balaram, now the director of the Indian Institute of Science. In the piece, Prof. Balaram describes C.V. Raman as having been a firm believer in universities being the powerhouses of research, not any separate entities.
The latest issue of ‘Current Science’ (May 10, 2014)
In 1932, C.V. Raman helped found Current Science after recognizing the need for an Indian science journal. In one of its first issues, an editorial appeared named ‘Retrenchment and Education’, in which the author, likely Prof. Raman himself, lays out the importance of having an independent body to manage scientific research in India. Because of its relevance to the issues at hand, I’ve reproduced it from the Current Science archives below.
The second letter’s contents follow from the first’s. Dhruba Saikia, Cotton College State University (Assam), and Rowena Robinson, IIT-Guwahati, ask for the country’s university-teaching to be overhauled. Many professors I’ve spoken to ask for the same thing but are turned to amusement after they realize that the problem has been left to fester for so long that the solution they’re looking for requires fixing our entire elementary education system. Moreover, after the forking of education and research described in Chatterji’s letter, it seems that universities were left to fend for themselves after their best teaching resources were drawn away by the government. Here is a paragraph from Saikia’s and Robinson’s letter:
Hundreds of thousands of students graduate from Indian universities each year. However, our own experience in selecting students indicates that many are ignorant of the basics, with underdeveloped reasoning skills and an inability to apply the knowledge they have.
There was also a third letter, this one critical of the Mathai-Robinson piece. Shobhana Narasimhan, a theoretical physicist from JNCASR, Bangalore, says that she is free to pursue “curiosity-driven science” and doesn’t have to spend as much time writing grant proposals as do scholars in the West, and so Mathai-Robinson are wrong on that front. At the same time, it seems from her letter that those things she has access to that her presumably better-equipped Occidental colleagues don’t could also be the result of a lack of control on research agendas and funding in India. In short, she might be free to pursue topics her curiosity moves her toward because the authorities don’t care (yes, this is a cynical point of view, but I think it must be considered).
So I emailed her and she replied.
“The quick answer to your question is I don’t think more overview of research funding is the answer to improving Indian science. My colleagues abroad spend more time writing proposals to get funding than actually carrying out research… I don’t think that is a good situation. Similarly getting tenure at an American university often depends on how much money you brought in. We don’t have such a situation (yet) and I think that is good.
We shouldn’t blindly copy foreign systems because they are by no means perfect. [Emphasis mine]
I have been on grant committees and I found good proposals always got funded. But I do agree that there is often much dead wood in many Indian departments, but that can also happen abroad.
I am aware that I may be speaking from a position of privilege since I work at one of the better funded institutes. Also as a theorist, I do not need much equipment.”
I would say Narasimhan’s case is the exception rather than the rule. Although I don’t have a background in researching anything (except for my articles and food prices), two points have been established with general consensus:
The Rajiv Gandhi-era promise of funding for scientific R&D to the tune of 2% of GDP is yet to materialize. The fixation on this number ranges from the local – for unpaid students and ill-equipped labs – to the global – to keep up with investments in other developing countries.
Even if there is funding, there is no independent body staffed with non-governmental stakeholders to decide which research groups get how much, leading to arbitrary research focus.
The half-century old mathematics that ecologists use to understand how predator and prey populations rise and fall has received a revamp. Two scientists from Georgia Tech did this by crediting evolution for what it is but not commonly thought to be: fast, not slow.
The scientists, Joshua Weitz and Michael Cortez, applied a branch of mathematics called fast-slow dynamical systems theory to model how two populations could vary over time if they are evolving together. Until now, this has been the exclusive demesne of the Lotka-Volterra equations, derived by Alfred Lotka and Vito Volterra in the early 20th century. On a graph, these equations are visually striking for how they show predator and prey numbers rising in falling in continuous cycles.
For example, cheetahs eat baboons. In an ecosystem good for baboonkind, baboons will thrive. Cheetahs will eat them and thrive. As the number of baboons increases, so will the number of cheetahs. With too many cheetahs, the number of baboons will decline. As a result, the number of cheetahs will also decline. But the ecosystem is good for baboons. So after the number of cheetahs has declined, more baboons will appear. As the number of baboons increases, so does the number of cheetahs. And so on.
Image: Wikimedia Commons
However, the Lotka-Volterra equations make several assumptions to get this far, many of which oversimplify natural conditions to the point that they no longer seem natural. Chief among them concerns the ignorance of genetic variations. Animals do possess them whether in the field or in the laboratory but the Lotka-Volterra equations assume the differences arising from them don’t exist. As a result, while “predators and their prey differ in their abilities acquire food or avoid capture,” the equations just overlook such traits, said Michael Cortez, a postdoc at Georgia Tech and first author on the paper describing the revamped equations. It was published in the Proceedings of the National Academy of Sciences May 5.
Turned on its head
In fact, Cortez and his postdoctoral mentor Joshua Weitz were particularly motivated by three studies, two from 2001 and one from 2011, whose findings gave rise to absurd implications if the Lotka-Volterra reasoning was applied. The equations – like depicted in the chart – require the prey population to peak first, followed by the predator population. The studies from 2001 and 2011 investigated gyrfalcon-rock ptarmigan, mink-muskrat and phage-V. cholerae pairs, and found the opposite: they showed the predator population peaked first, before the prey population did.
So are the prey eating the predators? “This is not the case,” Cortez explained. According to him, the reversal in peaking is driven by fluctuations in the abundance of different types of prey. One type of prey could be more or less able to avoid capture, while one type of predator could be more or less able to capture prey. Thus, these two kinds of animals are developing distinct genetic traits at the same time, i.e. coevolving.
Image: Joshua Weitz
To understand how coevolution influenced the number of predators and prey, Cortez and Weitz applied fast-slow dynamical systems theory. The ‘fast’ applies to the change in the number of types of predator or prey. The ‘slow’, to how the population as a whole is changing. Between them, says Cortez, “I was able to break the reverse cycles into pieces and study each piece of the cycle individually, allowing me to understand how coevolution was causing the reverse cycles.”
“The most surprising and exciting prediction from our work is that co-evolution between predators and prey can reverse this ordering, yielding cycles where peaks in prey abundance follow peaks in predator abundance,” Weitz added.
A different fast-slow
While this is not the first study to investigate what effects evolution has on changing populations, it is the first to accommodate fast rates of evolution, i.e. evolutionary changes that are more rapid and occur within a few generations. As a result, their implications are far-ranging, too, for the Lotka-Volterra equations were not restricted to ecology even though they were inspired by it. One other area of science in which a system could go back and forth between two stable states is chemistry and all its chemical reactions.
However, just like in ecology, the precise mathematics that governs them is computationally intensive. On May 6, researchers from Oxford University published a paper in The Journal of Chemical Physics explaining how the mathematics could be further simplified, making it easier to model them on computers. While this team also considers fast-slow systems, the designation is different. The Cortez-Weitz model compared how rapid evolutionary changes (fast) affected population (slow). The ‘Oxford model’, on the other hand, compares how changes in the sources of food (fast) affect the time taken for the predators to become extinct (slow).
This image shows the evolution of a prey (blue line) and predator (green line) system in three parameter regimes: from the low extinction risk in Regime 1 to the high extinction risk in Regime 3. Credit: M. Bruna/University of Oxford
To demonstrate, Maria Bruna, the first author on the paper, explained that in their system, she and her team consider whale and plankton populations. Plankton is an important food source for whales. While whales live and function over many years, plankton blooms can be fickle and change their yield of food on a daily basis. However, some environmental conditions can push the plankton blooms to take many years to shift their yield. “In such cases, the whales will ‘care’ about these metastable transitions in plankton, since they notice the changes in plankton abundance on a timescale which is relevant to them,” she said.
Weitz expressed interest in this work: “It would be very interesting to see what happens when their method is applied to more complex contexts, including in which populations are comprised of two or more variants.”
References:
Cortez MH, & Weitz JS (2014). Coevolution can reverse predator-prey cycles. Proceedings of the National Academy of Sciences of the United States of America PMID: 24799689
Bruna M, Chapman SJ, & Smith MJ (2014). Model reduction for slow-fast stochastic systems with metastable behaviour. The Journal of chemical physics, 140 (17) PMID: 24811625
On May 6, the team behind the now-inoperative Planck space telescope released a map of the magnetic field pervading the Milky Way galaxy.
Titled ‘Milky Way’s Magnetic Fingerprint’, the map incorporates two textures to visualize the magnetic field’s dual qualities: striations for direction and shading for intensity.
Planck was able to measure the polarization by studying light. Light is a wave (apart from being a particle, too). As a wave, it is composed of electric and magnetic fields vibrating perpendicular to each other. Overall, however, the two fields could vibrate in any direction. So when they choose to vibrate in a particular direction, the light is said to be polarized.
Such light is emitted by dust grains strewn in the space between Milky Way’s stars. As Dr. Chris Tibbs, an astrophysicist from Caltech, told me over Twitter, “Dust grains absorb light from stars, which heats up the grains, and [they] then radiate away this heat producing the emission.”
The grains are oriented along the Milky Way’s magnetic field, so the light they emit is polarized along the magnetic field. Because the grains are so small, the light they emit is of very low intensity (i.e. very long wavelength), so it takes a powerful telescope like Planck, perched on its orbit around the Sun, to study it.
It used a technique that’s the opposite of polarized sunglasses, which use filters to eliminate polarized light and reduce glare. The telescope, on the other hand, used filters to eliminate all but the polarized light, and then studied it to construct the map shown above.
As the astrophysicist Katie Mack pointed out on her Facebook page, the Planck team that released this image has carefully left out showing the magnetic fields in the region of the sky studied by the BICEP2 telescope at the South Pole which, on March 17, announced the discovery of evidence pointing to cosmic inflation. According to Katie,
The amount of polarized dust emission in the region where BICEP2 made its observation is unknown, but if it turns out to be a lot, it could mean that the signal BICEP2 saw was not entirely primordial.
This means we’ve to wait until the end of the year to know if the BICEP2 announcements were all they were made out to be.
The asteroid that wiped out dinosaurs 66 million years ago didn’t get them all. Some of them survive to this day in the form of birds, and they may have made it because they got smaller.
For about 170 million years, dinosaurs were the dominant life-forms that lived on land. In this period, spanning the Triassic, Jurassic and Cretaceous periods, they evolved to acquire a variety of traits. One of them was size. As different lineages competed for different resources, some of them became very big: the t-Rex weighed almost eight tonnes. The dinosaurs that would evolve to become birds, on the other hand, weighed a few kilograms or less. The lightest, Qiliania graffini, weighed 15 grams.
A new data analysis has revealed that their small size helped them continue to survive after the mass-extinction event that was to follow. “There is increasing evidence that this extinction event was ecologically selective, and that large animals in particular suffered the most,” said Roger Benson, a palaeobiologist at the Department of Earth Sciences, Oxford University.
Dr. Benson and his colleagues conducted the analysis, published in PLoS Biology on May 6. First, they compiled a list of dinosaurs to study. Then, the team used the results of a previous study to estimate these reptiles’ masses. That study was conducted by two members of the same team who had established that the thickness of the leg bones have a strong relationship with body mass, “allowing the masses of extinct animals to be estimated”.
Their analysis found that once some dinosaurs evolved to giant sizes, they had it harder to invade new ecological niches and didn’t evolve new body forms. According to Dr. Benson, they were effectively ‘locked in’ to their niches. After the extinction event, these dinosaurs had a hard time adapting to their new environment.
I’ve gotten too big, haven’t I?
However, why the smaller ones had it easier is not immediately clear. Nick Longrich, from the Department of Biology and Biochemistry, University of Bath, who wasn’t involved in the analysis, thinks the crashing asteroid’s impact would have altered the environment drastically enough to favor smaller animals over bigger ones.
“There probably wasn’t much food when the asteroid hit,” he said. “It would have put a lot of dust and debris in the air, covering the sun, so there would be no photosynthesis going on. It would have been a global famine.” As a result, the available food would have been insects and invertebrates, the smaller animals that eat them, and their predators.
The dust and debris would also have caused a global cooling, and smaller animals will have had it easier to find shelter. These animals also reproduce rapidly, according to Dr. Longrich, implying that they would have been harder to wipe out.
Dr. Benson’s analysis also found the early birds were able to survive because they were able to maintain a rapid rate of evolution. The other dinosaurs also evolved rapidly in their early years, but as their respective ecological niches became saturated, the rate at which they diversified slowed down. The birds however continued to produce ecological diversity and adapted better.
One such study was published in the International Journal of Organic Evolution in February 2014 which noted, “The high evolutionary rates arose primarily from a reduction in body size.”
However, it is not immediately clear why birds and their close relatives became small in the first place. “The explanation must be specific to the ecology of these animals, because many other dinosaur lineages existing at the same time did not become as small,” Dr. Benson explained.
So although the odds are 70 million-to-1 that a big asteroid will impact Earth and threaten life, birds and insects will have it easier if it does.
Astronomers who were measuring the length of one day on an exoplanet for the first time were in for a surprise: it was shorter than any planet’s in the Solar System. Beta Pictoris b, orbiting the star Beta Pictoris, has a sunrise every eight hours. On Jupiter, there’s one once every 10 hours; on Earth, every 24 hours.
This exoplanet is located 63.4 light-years from the Solar System. It is a gas giant, a planet made mostly of gases of light elements like hydrogen and helium, and more than 10 times heavier than Earth. In fact, Beta Pictoris b is about eight times as heavy as Jupiter. It was first discovered by the Very Large Telescope and the European Southern Observatory in 2003. Six years and more observations later, it was confirmed that it was orbiting the star Beta Pictoris instead of the star just happening to be there.
On April 30, a team of scientists from The Netherlands published a paper in Nature saying Beta Pictoris b was rotating at a rate faster than any planet in the Solar System does. At the equator, its equatorial rotation velocity is 25 km/s. Jupiter’s equatorial rotation velocity is almost only half of that, 13.3 km/s.
The scientists used the Doppler effect to measure this value. “When a planet rotates, part of the planet surface is coming towards us, and a part is moving away from us. This means that due to the Doppler effect, part of the spectrum is a little bit blueshifted, and part of it a little redshifted,” said Ignas Snellen, the lead author on the Nature paper and an astronomy professor at the University of Leiden.
So a very high-precision color spectrum of the planet will reveal the blue- and redshifting as a broadening of the spectral lines: instead of seeing thin lines, the scientists will have seen something like a smear. The extent of smearing will correspond to the rate at which the planet is rotating.
Bigger is faster
So much is news. What is more interesting is what the Leiden team’s detailed analysis tells us, or doesn’t, about planet formation. For starters, check out the chart below.
Image: Macclesfield Astronomical Society
This chart shows us the relationship between a planet’s mass (X-axis) and its spin angular momentum (Y-axis), the momentum with which it spins on an axis. Clearly, the heavier a planet is, the faster it spins. Pluto and Charon, its moon, are the lightest of the lot and their spin rate is therefore the lowest. Jupiter, the heaviest planet in the Solar System, is the heaviest and its spin rate is also the highest. (Why are Mercury and Venus not on the line, and why have Pluto and Earth been clubbed with their moons? I’ll come to that later.)
“Apparently the more massive the planet, the more angular momentum it acquires,” Prof. Snellen said. This would put Beta Pictoris b farther along the line, possibly slightly beyond the boundaries of this chart – as this screenshot from the Leiden team’s pre-print paper shows.
Unfortunately, science doesn’t yet know why heavier planets spin faster, although there are some possible explanations. A planet forms from grains of dust floating around a star into a large, discernible mass (with many steps in between). This mass is rotating in order to conserve angular momentum. As it accrues more matter over time, it has to conserve the kinetic and potential energy of that matter as well, so its angular momentum increases.
There have been a few exceptions to this definition. Mercury and Venus, the planets closest to the Sun, will have been affected by the star’s gravitational pull and experienced a kind of dragging force on their rotation. This is why their spin-mass correlations don’t sit on the line plotted in the chart above.
However, this hypothesis hasn’t been verified yet. There is no fixed formula which, when plotted, would result in that line. This is why the plots shown above are considered empirical – experimental in nature. As astronomers measure the spin rates of more planets, heavy and light, they will be able to add more points on either side of the line and see how its shape changes.
At the same time, Beta Pictoris b is a young planet – about 20 million years old. Prof. Snellen used this bit of information to explain why it doesn’t sit so precisely on the line:
Sitting precisely on the line would be an equatorial velocity of around 50 km/s. But because of its youth, Prof. Snellen explained, this exoplanet is still giving off a lot of heat (“this is why we can observe it”) and cooling down. In the next hundreds of millions of years, it will become the size of Jupiter. If it conserves its angular momentum during this process, it will go about its life pirouetting at 50 km/s. This would mean a sunrise every 3 hours.
I think we can stop complaining about our days being too long.
Spin velocity v. Escape velocity
Should the empirical relationship hold true, it will mean that the heaviest planets – or the lightest stars – will be spinning at incredible rates. In fact, the correlation isn’t even linear: even the line in the first chart is straight, the axes are both logarithmic. It is a log-log plot where, like shown in the chart below, even though the lines are straight, equal lengths of the axis demarcate exponentially increasing values.
Image: Wikipedia
If the axes were not logarithmic, the line f(x) = x3 (red line) between 0.1 and 1 would look like this:
Image: Fooplot.com
The equation of a line in a log-log plot is called a monomial, and goes like this: y = axk. In other words, y varies non-linearly with x, i.e. a planet’s spin-rate varies non-linearly with its mass. Say, if k = 5 and a (a scaling constant) = 1, then if x increases from 2 to 4, y will increase from 32 to 1,024!
Of course, a common, and often joked-about, assumption among physicists has been made: that the planet is a spherical object. In reality, the planet may not be perfectly spherical (have you known a perfectly spherical ball of gas?), but that’s okay. What’s important is that the monomial equation can be applied to a rotating planet.
Would this mean there might be planets out there rotating at hundreds of kilometres per second? Yes, if all that we’ve discussed until now holds.
… but no, if you discuss some more. Watch this video, then read the two points below it.
The motorcyclists are driving their bikes around an apparent centre. What keeps them from falling down to the bottom of the sphere is the centrifugal force, a rotating force that, the faster they go, pushes them harder against the sphere’s surface. In general, any rotating body experiences this force: something in the body’s inside will be fleeing its centre of rotation and toward the surface. And such a rotating body can be a planet, too.
Any planet – big or small – exerts some gravitational pull. If you jumped on Earth’s surface, you don’t shoot off into orbit. You return to land because Earth’s gravitational pull doesn’t let you go that easy. To escape once and for all, like rockets sometimes do, you need to jump up on the surface at a speed equal to the planet’s escape velocity. On Earth, that speed is 11.2 km/s. Anything moving up from Earth’s surface at this speed is destined for orbit.
Points 1 and 2 together, you realize that if a planet’s equatorial velocity is greater than its escape velocity, it’s going to break apart. This inequality puts a ceiling on how fast a planet can spin. But then, does it also place a ceiling on how big a planet can be? Prof. Snellen to the rescue:
Yes, and this is probably bringing us to the origin of this spin-mass relation. Planets cannot spin much faster than this relation predicts, otherwise they would spin faster than the escape velocity, and that would indeed break the planet apart. Apparently a proto-planet accretes near the maximum amount of gas such that it obtains a near-maximum spin-rate. If it accretes more, the growth in mass becomes very inefficient.
(Emphasis mine.)
Acting forces
The answer will also depend on the forces acting on the planet’s interior. To illustrate, consider the neutron star. These are the collapsed cores of stars that were once massive but are now dead. They are almost completely composed of neutrons (yes, the subatomic particles), are usually 10 km wide, and weigh 1.5-4 times the mass of our Sun. That implies an extremely high density – 1,000 litres of water will weigh 1 million trillion kg, while on Earth it weighs 1,000 kg.
Neutron stars spin extremely fast, more than 600 times per second. If we assume the diameter is 10 km, the circumference would be 10π = ~31 km. To get the equatorial velocity,
So, if you wanted to launch a rocket from the surface of a neutron star and wanted it to escape the body’s gravitational pull, it has to take off at more than 30 times the speed of sound. However, you wouldn’t get this far. Water’s density should have given it away: any object would be crushed and ground up under the influence of the neutron star’s phenomenal gravity. Moreover, at the surface of a neutron star, the strong nuclear force is also at play, the force that keeps neutrons from disintegrating into smaller particles. This force is 1032 times stronger than gravity, and the equation for escape velocity does not account for it.
However, neutron stars are a unique class of objects – somewhere between a white dwarf and a black hole. Even their formation has nothing in common with a planet’s. On a ‘conventional’ planet, the dominant force will be the gravitational force. As a result, there could be a limit on how big planets can get before we’re talking about some other kinds of bodies.
This is actually the case in the screenshot from the Leiden team’s pre-print paper, which I’ll paste here once again.
See those circles toward the top-right corner? They represent brown dwarfs, which are gas giants that weigh 13-75 times as much as Jupiter. They are considered too light to sustain the fusion of hydrogen into helium, casting them into a limbo between stars and planets. As Prof. Snellen calls them, they are “failed stars”. In the chart, they occupy a smattering of space beyond Beta Pictoris b. Because of their size, the connection between them and other planets will be interesting, since they may have formed in a different way.
Disruption during formation is actually why Pluto-Charon and Earth-Moon were clubbed in the first chart as well. Some theories of the Moon’s formation suggest that a large body crashed into Earth while it was forming, knocking off chunks of rock that condensed into our satellite. For Pluto and Charon, the Kuiper Belt might’ve been involved. So these influences would have altered the planets’ spin dynamics, but for as long as we don’t know how these moons formed, we can’t be sure how or how much.
The answers to all these questions, then, is to keep extending the line. At the moment, the only planets for which the spin-rate can be measured are very massive gas giants. If this mass-spin relation is really universal, than one would expect them all to have high spin-rates. “That is something to investigate now, to see whether Beta Pictoris b is the first of a general trend or whether it is an outlier.”
I’d linked to a preprint paper [PDF] on arXiv a couple days ago that had summarized the search for Supersymmetry (Susy) from the first run of the Large Hadron Collider (LHC). I’d written to one of the paper’s authors, Pascal Pralavorio at CERN, seeking some insights into his summary, but unfortunately he couldn’t reply by the time I’d published the post. He replied this morning and I’ve summed them up.
Pascal says physicists trained their detectors for “the simplest extension of the Standard Model” using supersymmetric principles called the Minimal Supersymmetric Standard Model (MSSM), formulated in the early 1980s. This meant they were looking for a total of 35 particles. In the first run, the LHC operated at two different energies: first at 7 TeV (at a luminosity of 5 fb-1), then at 8 TeV (at 20 fb-1; explainer here). The data was garnered from both the ATLAS and CMS detectors.
In all, they found nothing. As a result, as Pascal says, “When you find nothing, you don’t know if you are close or far from it!”
His paper has an interesting chart that summarized the results for the search for Susy from Run 1. It is actually a superimposition of two charts. One shows the different Standard Model processes (particle productions, particle decays, etc.) at different energies (200-1,600 GeV). The second shows the Susy processes that are thought to occur at these energies.
Cross sections of several SUSY production channels, superimposed with Standard Model process at s = 8 TeV. The right-handed axis indicates the number of events for 20/fb.
The cross-section of the chart is the probability of an event-type to appear during a proton-proton collision. What you can see from this plot is the ratio of probabilities. For example, stop-stop* (the top quark’s Susy partner particle and anti-particle, respectively) production with a mass of 400 GeV is 1010 (10 billion) less probable than inclusive di-jet events (a Standard Model process). “In other words,” Pascal says, it is “very hard to find” a Susy process while Standard Model processes are on, but it is “possible for highly trained particle physics” to get there.
Of course, none of this means physicists aren’t open to the possibility of there being a theory (and corresponding particles out there) that even Susy mightn’t be able to explain. The most popular among such theories is “the presence of a “possible extra special dimension” on top of the three that we already know. “We will of course continue to look for it and for supersymmetry in the second run.”
