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These are notes I took while reading Gino Segre’s A Matter of Degrees (2002) when it first came out.  This was before I was posting regularly so there are in the form of notes for myself, but I think useful to make available to others, here.


Title: A Matter of Degrees: What Temperature Reveals About the Past and Future of our Species, Planet and Universe.

Author:  Gino Segré
Publisher:  Viking
Date of Original Copyright: 2002
Date of Current Copyright:
Date of Translation Copyright:
Date Read:  August 2002

“I’m using the measurement of temperature as a guide in exploring many aspects of science.” xi

Segré, a professor of physics and astronomy at the University of Pennsylvania, is writing for a lay audience and wants to show the centrality of temperature to our lives and universe.  He does a pretty good job of it, though not with the panache of others.  Too often we get a page or two of various men’s relation to, say the invention of the thermometer, that might be excerpts from short encyclopedic entries; no great linking skein of thought.  Not that the bios aren’t interesting, or the facts about the appearance of the thermometer – just that it might be more felicitous.

The introduction posits the three basic measuring units of our lives: the ruler, the clock and the thermometer.  The thermometer – to measure heat, or its absence, cold, has the interesting property of having no obvious 0 point, unlike time, or distance.  The discovery of 0 degrees was a matter of deduction, not common sense.

  1. 98.6  Segré explores the remarkable fact that the core temperature of humans, all other mammals, and birds is 98.6 degrees, plus or minus a bit.  The accuracy of that measurement is only a couple of hundred years old, as there were no thermometers until about 1740. [The liver hovers at about 105, and the skin is about 92; temperature does not vary with position on the globe, but does rise slightly through the day, and drops during the night..]  Heat is created by burning food and drink. It is dissipated through the skin (85%) and respiration and excretion.

    1. Warm-blooded creatures, birds and mammals, are also referred to as homeotherms. While some can lower their body temperatures as during hibernation, most must keep a steady temperature.  Why at the temperature we have (98.6 F)?  Because this is the optimal temperature for the various chemical reactions that keep the body going.(9) In order to keep the body at this temperature there have to be good cooling mechanisms.  Here, evaporation is the key.  Interesting anecdote about the great Tour de France champion, Eddie Merckx.  Although capable of days of cycling at high speeds, when he was put in an enclosed room and pedaled he passed out in about an hour: no wind, little evaporation, body core heat rises, he passes out.(15) [Of caloric intake only 25% goes to mechanical energy; 75% is dissipated as extra body heat.]  When it is muggy, as well as hot, the water vapor cannot leave the skin as swiftly as when it is dry, thus even though we sweat, there is no cooling.

    2. Protection against the cold is also needed, and mostly done with clothing, however shivering generates additional internal heat. The capillaries stop bringing blood to the surface and so the colder skin – with less of a gradient to the cold air – acts as somewhat of an insulator.  Japanese women peal divers were able to increase their metabolic rate during the diving season (though in one of other such failures, he fails to mention how this was done.) (19)

    3. He goes into the nature of fevers in the body: that they are still little understood.  Gives a history of trying to deal with them, from Galen to Pasteur.  Mention of psychiatric treatment by inducing fever (33) Some evidence that fevers enhance the functioning of the immune system – by increasing the production of heat shock proteins.(38)
  2. Measure for Measure. The measurement of temperature followed that of distance and time. The progress of fire in early man. (200,000 years ago was transition of H. erectus to H.sapiens and there is chemical evidence of firewood found from that period. (Though there is argument, and claim that starchy tubers were being cooked in the plains of Africa 1.8 million years ago.(44)) “Great Leap Forward” about 50,000 years ago – weapons and tools.  Oldest clay figurines 27,000 years ago (Czech Republic); oldest fired clay pottery 14,000 years ago (Japan.) (45) Iron age began at different times in different places but is marked by the ability to get to 2500 degrees Fahrenheit.

    1. Thermometers 4 inventors; among them Galileo –abt 1600. Still in development in 1700s, experimenting with different fluids (among them Newton,) Fahrenheit (a Dane?) visited Ole Rohmer and was responsible for the scale we use now. Others adopted the Celsius scale. Both use the freezing point of ice and the boiling point of water as the two markers. Fahrenheit was probably trying to get the body temperature to be 100, thus the odd 32 for ice.
    2. More history of the development of understanding of steam power (around Manchester, England), the laws of thermodynamics and in fact the nature of heat – that it is another form of energy, not a caloric fluid. Carnot, who first understood the underlying principles of heat, and steam engines; he enunciated what came to be the 2nd law of Thermodynamics. The work a steam engine depends only on the temperature difference between the source and sink of heat. (67)

    3. The three laws: 1) heat is simply another form of energy and as a whole, is conserved. 2) Thermal energy cannot be converted to mechanical energy with 100% efficiency (this lead, via Clausius to the famous entropy understanding; tied into concept that order can only go to disorder, and not contrary – without additional input.)

  3. Reading the Earth. On global warming; the rise in temp in Alaska.  The historical record – where he cites many of the things I read in the Ice Chronicles a few weeks ago.

    1. Four main contributors to earth’s temperature: the sun; internal earth heat; oceans and air.  Interesting discussion of the development of understanding of the Milankovitch cycle of global temperature: the overlapping, interacting cycles of precession (22,000 years), eccentricity (of the earth’s orbit due to gravitational pull of other parts of the solar system) 100,000 years and tilt (41,000 years.) Warmer temperatures appear roughly every 103,000, 82,000, 60,000, 35,000 and 11,000 years ago. (103) The last 10,000 years of rough stability is rare in the known history.  Temperature change also comes with increases of dust, wetness,,,) We don’t know why it is that from 1100 to 1250 it was warm enough for Vikings to grow crops in Greenland, nor why 1400 to 1800 was a “little ice age” with common freezing of Dutch canals, New York harbor… (111)

  4. Life in Extremes.  The first deep-sea bathysphere (1920s) and then the bathyscaph of Piccard. Development of continental drift theory, begun with Wegener in the 1910s (135).  By 1974 the submersible Alvin investigated deep ocean rifts in the Mid Atlantic.  In ’76 clams were seen along a deep hot spot near the Galapagos. (140) Some 500 new species have been found along the hydrothermal vents in Deep Ocean. (146) Most of them incorporate within themselves various types of bacteria that thrive at high temperatures.  Such microorganisms have relatives in surface hot springs – like Old Faithful.(149)  These thermophilic bacteria do this by converting sulfur atoms into carbohydrate.

    1. Snowball Earth. Other microorganisms live in extreme cold. Period between 750-530 million years ago is very strange. Earth seems to have jumped from very cold (whole earth covered in ice) to very hot. Evolution had been very slow from early creatures (3.8 billion ya) until about 565 mya.  Why?  By 500 mya all existing phyla were in existence, and none have appeared since. Why? [Cambrian Explosion.]

    2. One theory is that landmasses clustered near the equator about 700 mya, leading to a cooler earth.  Ice crept southward and covered much of it.  Then millions of years of volcanism increased the CO2 until a greenhouse effect began to warm the ice.

    3. Thermophilic microorganisms lead to the classification of Archae, as the third form of life –actually the first – prior to prokaryotes (bacteria – single cell, no nucleus) and eukaryotes (nucleus: animal, plant, fungi and algae.) (162)

    4. Short discussion of theory of earth formation from space dust, the Chicxulub meteor of 65 mya, and another probable meteor 250 mya (possible remains of which may be in the Australian outback near Shark Bay

    5. Temperature on earth is key to when and where life started on earth. (173) If fossils exist before time of generative temperatures life may have come from outer space; if fossils do not exist before the time of such a temperature it is probable life generated itself here on earth. (173)

    6. Life under two miles of ice: discusses life under the ice caps and possibility of

    7. life on Europa – a moon of Jupiter.

  1. Messages From the Sun (183) Cites George Gamow as earliest science influence in his own life, and Gamow’s early book on the Sun. Brief notes on temperature of the sun –of which we see only the 5800 K degree surface; non uniformity of surface; sunspots are cooler. Galileo’s early observation of sun-spots that he deduced properly (were not planets) and that by tracking he realized that the sun rotates about every 4.  weeks. Publication of his observations was his first statement in support of the Copernican theory and lead to his trouble with the Catholic Church. Spots are a function of fluctuating magnetic field.  Disjunction between early ideas of age of sun and time that evolution would have taken; when Curies revealed radiation Rutherford saw the connection to energy for life and brought evolution and sun’s life together. (187) True source of sun’s heat is fusion of hydrogen to helium. Core temperature for this fusion is 15 million degrees K.  Takes millions of years to diffuse out to surface. (189) Neutrinos are messengers from the sun and key players in the evolution of the Universe. Once thought to have no mass, now thought to have very small mass, about 1/10,000 of electron mass. Neutrino hitting neutron can make an electron + proton + energy. (192).  Put a chlorine tank deep in the Homestake gold mine, to see if argon atoms created from neutrino hitting chlorine atom; one every three days instead of expected every 1 day. (194)

Excursion on Rutherford – proclaimed that sun’s heat was from radioactivity; probed atomic structure by bombarding gold leaf with helium nuclei (alpha rays.)  Gamow met Rutherford and explained how to solve the decay problem of radioactivity. (197) Again temperature – that of barrier penetration of nucleus.

Birth and life cycle of stars; progress into Red Giant, due to consumption of H and growth of mass of He.  Collapse of stars bigger than earth created Iron, Carbon, and Magnesium etc during the collapse (fusion of H and He to greater and greater atoms at intense heat.) (204) Observation of super nova in 1987, coupled with appearance of neutrino blast in neutrino detectors. (207)

On black holes; first “discovery” of it in 1967 of regular radio signal, labeled LGM (little green men) Repetition so fast it confirmed black hole. (This as other parts of the book, are straying from temperature, to go into related areas of physics.)

On Steven Weinberg, theoretical physicist, author of “First Three Minutes.” Formation of early nuclei as temperature dropped to 1 billion degrees; hydrogen and helium atoms formed thousands (300,000) of years later when temperature dropped to 3000 K. (215)

6) The Quantum Leap. (227) Youth of many physicists and mathematicians. Search for absolute zero. Liquefaction of all gases; ending with liquefaction of He in 1908.  Faraday – 19th C premier experimentalist. (239-233).  Spectral lines of light in bunsen burner led to discovery of He in Sun. Later it was found on earth, A Nobel gas, an element that doesn’t combine chemically with others. (234)