Category Archives: Earth sciences

Earthquakes, soft bombs, and internet vulnerability

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Once I’d taken in the devastation wrought by the Tohoku earthquake and tsunami, my thoughts went to the physicists I knew at Tohoku University. The university is located in the city of Sendai, 81 miles from the earthquake’s epicenter and just 10 miles from where the tsunami hit land.

News was frustratingly difficult to obtain at first. Tohoku University’s website was down; emails were either not get­ting through or not being answered. On 16 March, five days after the earthquake struck, a friend of mine posted on Physics Today’s Facebook page that he’d heard from an old classmate of his, a nuclear physicist at Tohoku Univer­sity. Some campus buildings were damaged, but there were no casualties.

I learned later that the earthquake had damaged power lines and telecommunications cables. What’s more, the shutdown of Fukushima I and other nuclear power sta­tions in northeastern Japan had created a power shortage. Even if telecommunications cables or cellphone towers had remained operational, information would have stopped flowing on the internet due to a lack of electro­motive power.

That information is intrinsically physical and requires energy to store, process, and transmit is a familiar con­cept to physicists. But I was still surprised that an earth­quake had shut down, or at least slowed down, Sendai’s internet. After all, the internet’s message protocols and network structures were designed to survive nuclear attacks.

Given the nature of warfare, you can presume that if one group of military thinkers has devised a new weapon, another group will try to devise a countermeasure. I don’t know whether the US Pentagon’s ­BLU-114/B “soft bomb” was designed to take out an enemy’s internet, but, by targeting power plants, it could achieve that goal, too.

The soft bomb is a remarkable weapon. Within the bomb’s casing are a classified number of bomblets that contain a classified number of chemically treated graphite filaments. When detonated over a power plant, the bomb­lets release the filaments, which spread and fall in a dense cloud. Because graphite is a conductor, the filaments short­-circuit transformers on contact, leading to damaging lightning­-like discharges.

During the 1999 Kosovo War, the US Air Force’s F­-117 stealth fighters dropped soft bombs to temporarily disrupt or knock out 70% of Serbia’s electricity­-generating capacity. According to a timeline of the war published by Rasmus Ole Rasmussen, Bent C. Jørgensen, and Bernhelm Booss-Bavnbek, Belgrade’s power was cut off on day 66 of the war. Six days later, on 6 June, Slobodan Milošević accepted NATO’s peace plan.

I hope military thinkers are devising ways to protect the internet’s physical infrastructure—if not from soft bombs, then at least from earthquakes and tsunamis.

This essay by Charles Day first appeared on page 104 of the July/August 2011 issue of Computing in Science & Engineering, a bimonthly magazine published jointly by the American Institute of Physics and IEEE Computer Society.

Gaia in the Amazon

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In a 1974 paper in Tellus, chemist James Lovelock and biologist Lynn Margulis proposed a bold hypothesis: Earth’s living organisms act together to ensure that the planet remains hospitable to life. Following a suggestion by his neighbor, novelist William Golding, Lovelock named the hypothesis after the ancient Greek goddess of the Earth, Gaia.

Anselm Feuerbach’s 1875 painting Gaia decorates a ceiling in Vienna’s Academy of Fine Arts.

Given that most organisms belong to food chains that consist of, if not predators and prey, then eaters and eaten, the notion of planetary cooperation seems far-fetched. Still, Lovelock and Margulis made a strong, scientific case. Here’s the abstract of their Tellus paper:

During the time, 3.2 × 109 years, that life has been present on Earth, the physical and chemical conditions of most of the planetary surface have never varied from those most favourable for life. The geological record reads that liquid water was always present and that the pH was never far from neutral. During this same period, however, the Earth’s radiation environment underwent large changes. As the sun moved along the course set by the main sequence of stars its output will have increased at least 30% and possibly 100%. It may also have fluctuated in brightness over periods of a few million years. At the same time hydrogen was escaping to space from the Earth and so causing progressive changes in the chemical environment. This in turn through atmospheric compositional changes could have affected the Earth’s radiation balance. It may have been that these physical and chemical changes always by blind chance followed the path whose bounds are the conditions favouring the continued existence of life. This paper offers an alternative explanation that, early after life began it acquired control of the planetary environment and that this homeostasis by and for the biosphere has persisted ever since. Historic and contemporary evidence and arguments for this hypothesis will be presented.

That life has shaped Earth’s environment is beyond question. Whether and how life maintains the environment is less obvious. The planet’s inhabitants were evidently unable to prevent life-stifling sheets of ice spreading from polar regions during ice ages. Granted, evolution entails species adapting to the environment, but the adaptation is selfish and plays out on a local scale; it isn’t cooperative on a planetary scale.

Although I’m not convinced by the Gaia hypothesis, the question of how Earth’s life-sustaining environment arose is interesting and important. And thinking of Earth’s biosphere as a single system is surely appropriate in some scientific contexts, not least in the search for extraterrestrial life.

Plants that water themselves

Gaia sprang into my mind earlier this month when I came across a paper in Science. In May 2011 Christopher Pöhlker of the Max Planck Institute for Chemistry in Mainz, Germany, and his colleagues went to the Amazonian Tall Tower Observatory (ATTO) 150 km northeast of Manaus, Brazil. Their goal: to gather organic aerosol particles above pristine rainforest during the rainy season. Organic aerosols cool Earth’s surface by scattering sunlight. They also nucleate rain droplets. Despite their climatological importance, their origin and composition is unclear—hence Pöhlker’s investigation.

The paper reports what the team found when they subjected the aerosols to three different physical and chemical assays: near-edge x-ray absorption fine structure analysis, scanning electron microscopy, and secondary ion mass spectrometry.

To the team’s surprise, most of the organic aerosols contained 0.3%-20% of potassium by volume. Apparently, potassium ions serve to nucleate the formation of organic aerosols. Where does the potassium come from? Although soot from burning vegetation contains potassium, the team did not detect any fires during the collection period. They did, however, recall previous reports of plants and fungi releasing potassium inos and other inorganic species into the air. The potassium-nucleated organic aerosols are ideal for nucleating rain droplets—which suggests an intriguing possibility. To quote Pöhlker et al.:

Our findings support the hypothesis that the Amazonian rainforest ecosystem can be regarded as a biogeochemical reactor in which the formation of clouds and precipitation in the atmosphere are triggered by particles emitted from the biosphere.

I expect Pöhlker’s conclusion would delight Lovelock (Margulis died last year). Whether it supports the Gaia hypothesis is unclear, at least to me. Conceivably, plants could take up potassium from the soil in the form of ions dissolved in water. If plants emit potassium ions merely as a consequence of transpiration, then their ability to regulate rainfall is a happy coincidence.

Happenstance or not, the notion of plants watering themselves is amazing.

Is a warmer Earth a greener Earth? Remote sensing says no

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As the vast tall jungles of the Amazon evince, plants thrive in warm wet environments. Global warming, by promoting evaporation, should make some parts of the world wetter as well as warmer. Could our climate-changed world become greener? Would those extra plants, by sequestering carbon dioxide, help mitigate global warming?

Maybe. Rising temperatures also promote desertification. And if it gets too hot, the enzymes that catalyze photosynthesis stop working. Earth could become browner, not greener. In a paper published today in Science, Maosheng Zhao and Steven Running of the University of Montana in Missoula have tackled the green-versus-brown question in what I think is the only way possible: They analyzed remotely sensed data.

Amazon.jpg

The Moderate Resolution Imaging Spectrometer has been mapping Earth’s vegetation from space since 1999, when NASA launched Terra, the spacecraft that carries MODIS and four other environment sensors. The picture above is a MODIS image of the Amazon basin.

Unless you work in the field of remote sensing or, like me, have friends who do, you might not appreciate the science behind Terra and other Earth monitoring missions. MODIS is just as sophisticated as any imaging spectrometer built for astronomy. Its 36 wavelength bands span the range from 400 nm to 14.4 μm. Every day, Terra beams down a terabyte of data, a rate comparable to that generated by Higgs-hunting particle accelerators. And to extract useful data, you need to solve and apply radiation transfer formulas that Subrahmanyan Chandrasekhar and others developed for stellar atmospheres.

Zhao and Running used a decade’s worth of MODIS data to evaluate Earth’s net primary production (NPP) of carbon—that is, the mass of carbon from atmospheric carbon dioxide to terrestrial biomass. The decade 2000–09 was the warmest ever recorded. During that time, NPP rose in the Northern Hemisphere but it fell in the Southern Hemisphere in response to extensive droughts.

Unfortunately, the global balance turned out to be negative. Zhao and Running found that NPP decreased by 0.55 petagrams. Earth is getting browner, not greener.

Charles Day