Maquina Lectora

Notes of a curious mind

Category: History of Science (Page 1 of 2)

Climate Histories: Spying on the Stratosphere

He was in the air for more than eight hours. He was tired, trapped within a heavy helmet and an uncomfortable pressure suit that resembled an airtight cocoon. The air was so thin that he would be dead in seconds without the space suit. He was flying at altitude of 65,000 feet (about 19,800 metres). 95 percent of the atmosphere was below him.

Our pilot could see across whole countries but he was alone in complete radio silence. His food was a form of liquidized paste which was inserted into the helmet through a tube in a special port. The date was 5 July, 1956, and our pilot which was flying a Lochhead U-2 aircraft, was carrying out one of the most important missions of the cold war.

The first U-2, dubbed the ‘Dragon Lady’, was built in utter secrecy and its purpose was to gather intelligence during the Cold War era. It was a remarkable reconnaissance aircraft.  It was designed to operate at 70,000 feet (about 21,000 metres), higher and for longer periods than any other aircraft since then.  It was a difficult aircraft to fly. At an altitude close to limit, only 6 knots separated the speeds at which low-speed stall and high-speed buffet occurred. If the aircraft slowed beyond the low-speed stall limit, it could lose lift and begin to fall. The pilots had a name for this narrow range of acceptable airspeeds. They called it ‘coffin corner.’

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Climate Histories: Never underestimate the power of a woman

“I believe that the more clearly we can focus our attension on the wonders and realities of the universe abour us, the less taste we shall have for destruction”

Rachel Carson, 1954

Several major shifts occurred in the 1950s and the 1960s which involved an awareness of the ties between environmental and social problems. The hydrogen bomb and nuclear testing had triggered a “ban-the-atomic-bomb” movement, intensified after the Lucky Dragon incident in 1954, in which the 23-man crew of a Japanese fishing vessel was exposed to radioactive fallout caused by the United States hydrogen bomb test on Bikini Atoll in the South Pacific.

It was difficult to ignore the post-war impact on the environment in the United States and Europe. As early as 1943 a thick smog trapped the residents of Los Angeles in an unhealthy shroud of air pollution that came to be known as Black Monday. A deadly smog hung over the Monongahela Valley in 1948, left twenty dead and six thousand people ill, mainly in the town of Donora, southeast of Pittsburgh. Perhaps the worst case of air pollution was that of London in 1952, when a deadly fog killed more than four thousand people.

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Climate Histories: The emergence of the first interdisciplinary research programme in global climate

In the mid-1970s the evidence about the greenhouse effect and its effect to climate change was growing among the scientific community. Data showed a steady increase of CO2 (carbon dioxide) in the atmosphere during the twentieth century at a rate of 25 times the historical average. Scientists, influenced by the work of Callendar, Revelle, Suess and Keeling have started to wonder if the worming trend which was occurring in the twentieth century was indeed, due to industrial emissions of greenhouse gases like CO2.  At the same time, they discovered that the biological productivity of the oceans was an important regulator of the way the CO2 built up in the atmosphere, and that the water vapour which had been found to be an important factor in the formation of clouds, could also play a role in the modulation of weather and climate. And as the questions multiplied, scientists were starting to realise that only an interdisciplinary research programme could provide the much needed answers.

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Why is the Sky Dark at Night? The Olbers’ Paradox, and Edgar Allan Poe’s Eureka

Why is the Sky Dark at Night? You might think that the answer is simple and obvious.  The sky appears dark because our side of Earth faces away from the Sun. But then, the universe is endless, it contains billion galaxies and innumerable luminous stars that we should be able to see their light from a particular distance away. Therefore, the night sky should be bright as noon!

The dark night sky paradox was a problem that dogged many astronomers since Kepler. But it was  the physician and astronomer Wilhelm Olbers, a man of amazing intellect, the first who tried to address the problem. He theorized that interstellar space is not transparent, but contains dust which absorbs energy from the stars, preventing some of their light from reaching us on Earth. The dark night sky problem was named after him the Olbers’ Paradox.

Curiously enough, it was the writer Edgar Allan Poe that first came up with at least part of the answer. Edgar Allan Poe, famous for his tales and poems of mystery, had a keen interest in science and in the field of cosmology, in particular. Just one year before his premature death in 1849, Poe wrote Eureka: An essay on the material and spiritual universe, a strange, intensive, and metaphysical, yet quite scientific in content, prose poem, which he dedicated to the  naturalist Alexander von Humboldt.

“I design to speak of the Physical, Metaphysical and Mathematical – of the Material and Spiritual Universe – of its Essence, its Origin, its Creation, its Present Condition and its Destiny.”

In Eureka, Poe claimed, among other things, that the universe is finite – in 1848 a finite-aged universe was mere speculation, and adopted a more philosophical phraseology of Newton’s Law of Gravitation, claiming that gravity is nothing but the attraction of every atom to the other atoms.

“Every atom, of every body, attracts every other atom, both of its own and of every other body, with a force which varies inversely as the squares of the distances between the attracting and attracted atom.”

Poe also pondered the question of the Olders’ Paradox. He suggested that the universe is not old enough to fill the sky with light. Is also endless in size; we see only a tiny part of it, and that observable part contains too few stars to fill up the sky with light. Poe knew that light moves extremely quickly but he claimed that there hasn’t been enough time for the light to reach us from farthest reaches of the universe.

“No astronomical fallacy is more untenable, and none has been more pertinaciously adhered to, than that of the absolute illimitation of the Universe of Stars. The reasons for limitation, as I have already assigned them, à priori, seem to me unanswerable; but, not to speak of these, observation assures us that there is, in numerous directions around us, certainly, if not in all, a positive limit—or, at the very least, affords us no basis whatever for thinking otherwise. Were the succession of stars endless, then the background of the sky would present us an uniform luminosity, like that displayed by the Galaxy—since there could be absolutely no point, in all that background, at which would not exist a star. The only mode, therefore, in which, under such a state of affairs, we could comprehend the voids which our telescopes find in innumerable directions, would be by supposing the distance of the invisible background so immense that no ray from it has yet been able to reach us at all. That this may be so, who shall venture to deny? I maintain, simply, that we have not even the shadow of a reason for believing that it is so.”

In the 1920s American astronomer Edwin Hubble demonstrated the existence of other galaxies besides the Milky Way and that these galaxies are moving away from ours. What Hubble observed when he looked at the distant galaxies, was that their light was redshifted (stretched out to longer wavelengths), an effect became known as the Hubble expansion, and thus the galaxy clusters were moving away from each other.

The universe is now believed to be approximately 13.8 billion years old and current observations show that the bulk of material in space is non-luminous dark matter. Poe was right. But there is also another, additional, reason of why the sky is black. Stars, like our Sun, shine for a few billion years, before they consume their supply of fuel and collapse into a white dwarf. The collapse of the old stars provides material that will give birth to a new generation of stars. But this material is not enough to provide fuel that would keep the stars shining forever and fill up all the space with light. And so the night sky is dark.

 

References and further reading

Edgar A. Poe, Eureka: An essay on the material and spiritual universe

Soter, Steven, and Neil deGrasse Tyson. 2001. Cosmic horizons: astronomy at the cutting edge. New York: New Press.

Heinrich Olbers.” Astronomy & Space: From the Big Bang to the Big Crunch. Gale, 2008. Biography in Context. Web. 22 Apr. 2016, 2008. Biography in Context. Web. 22 Apr. 2016

Image credit: NASA/JPL-Caltech

 

Climate Histories: Joseph Fourier – the terrestrial temperatures and the greenhouse

The story of the greenhouse effect begins nearly two centuries ago, in the early 19th century, with the work of the French Jean-Baptiste Joseph Fourier (21 March 1768 – 16 May 1830). Fourier, an ambiguous personality, was a mathematician, a scientist, and a member and secretary of the French Academy of Sciences. He was a friend of Napoleon, governor of Egypt and a promoter of the French Revolution.  He was imprisoned, twice. His reputation is largely based on his ‘Fourier Series’ a widely used mathematical technique in which complex functions can be represented by a series of sines and cosines.

Fourier’s article of 1824 “Mémoire sur la température du globe terrestre et des espaces planétaires” (On the Temperatures of the Terrestrial Sphere and Interplanetary Space) has been often mentioned as the first reference in the literature to the atmospheric ‘greenhouse effect’.  In this article, Fourier presented some ‘general remarks’ on the temperature of the Earth, but he never mentioned a greenhouse and actually he told his readers that the ‘analytic details which are omitted here are published in the works which I have already published’.[1]  Fourier’s main contribution of his 1824 article is the introduction of planetary temperature. He distinguishes three sources from which the Earth derives its heat:

Fourier2

Joseph Fourier. By User:Bunzil at en.wikipedia [Public domain], from Wikimedia Commons

The Earth receives the rays of the Sun, which penetrate its mass and are converted there into dark heat; the Earth also possesses heat of its own which it retains from its origin, and which dissipates continually at the surface; finally, this planet receives rays of light and heat from the countless stars among which the solar system is located. These are the three general causes which determine terrestrial temperatures.”[2]

Fourier established the concept of an energy balance for Earth and planets and discovered that planets reflect part of the solar light (today, it is called albedo) as well as losing energy by infrared radiation, which had been discovered by Frederick William Herschel 25 years earlier. Fourier called this energy “chaleur obscure” or ‘dark heat’. He examined each of the three sources from which Earth derives its hear and the phenomena they produce, including the heating of the atmosphere, but he did not set out to think about climate change.

Fourier compared the heating of the atmosphere to the action of a heliothermometer, an instrument which was designed and was used in scientific mountaineering in the 1760s by Horace Benedict de Saussure. James R. Fleming describes the instrument in his book Historical Perspectives on Climate Change[3],

 “It consisted of a small wooden box lined with a layer of black cork. Sunlight entered the box of glass separated by air spaces. This arrangement served to magnify the heating effect of the Sun’s rays (measured by a thermometer enclosed in the box) while eliminating the cooling effect of wind currents.”

For Fourier, the atmosphere was like a giant heliothermometer, ‘sandwiched between the surface of the Earth and an imaginary cap provided by the finite temperature of interstellar space’. He didn’t used the term greenhouse, but a different metaphor: “diaphanous envelope.” Nevertheless, he got the essence of the greenhouse effect right.

Fourier’s article of 1824, was mentioned by John Tyndall, Svante Arrhenious, and by many others. Today, many scientific review articles also cite Fourier’s article, but most of them contain brief historical references typically drawn from secondary rather the original sources. “Those seeking to understand Fourier’s scientific contributions to climate change need to look well beyond the secondary literature”, says James Fleming. It is in his magnus opus, Théorie analytique de la chaleur (Analytic Theory of Heat) [4] where Fourier discusses the problem of terrestrial temperatures and the principles governing the temperature of a green-house (serre in French). He argues that the mean temperature of the earth would be on the rise, if the heat acquired from the radiation of the sun were not balanced by that which escapes in rays from all points of the earth’s surface.[5]

References:

[1] Herivel J, (1975), Joseph Fourier: The Man and the Physicist, Claredon Press

[2] Jean-Baptiste Joseph Fourier. On the Temperatures of the Terrestrial Sphere and Interplanetary Space, translated by R. T. Pierrehumbert https://geosci.uchicago.edu/~rtp1/papers/Fourier1827Trans.pdf

[3] Fleming, James Rodger ‘ Historical Perspectives on Climate Change, Oxford University Press (19 May 2005)

[4] Joseph, Fourier, The analytical theory of heat, (translated with notes by Alexander Freeman, University Press, Cambridge, 1878) 3-4

[5] In his essay published in 1824, Fourier presented the “Theorie Mathematique de la Chaleur” (Theory of Heat), where he argued that the mean temperature of the earth would be on the rise, if the heat acquired from the radiation of the sun were not balanced by that which escapes in rays from all points of the earth’s surface

Image: Fourier’s grave, Père Lachaise Cemetery  (Coyau / Wikimedia Commons, via Wikimedia Commons)

The Planet Remade: How Geoengineering Could Change the World

More than 190 world leaders and representatives gathered this week in Paris to address the issue of climate change and to re-affirm their commitment to tackle climate change. The United Nations 21st Conference of the Parties (COP21), the last, best chance to curb greenhouse gas emissions for many, aims to agree on a global legally binding climate treaty to cut out carbon emissions, halt deforestation and keep fossil fuel in the ground.

The surface of the Earth is warming with unpredictable consequences. Scientists, NGOs, and some of the biggest humanitarian organisations warn about the dire effects of climate change. IMF has warmed that human “fortunes will melt with the ice, evaporate like water under a relentless sun, and wither away like sand in a desert storm. And the planet’s poorest and most vulnerable people will be the first to feel the pain.”

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