Reading Date: May 16, 2023 ~ Sep 4, 2023
98.6 F
Human’s body temperature is 98.6 F, though it may change according to the time of day or age. The hypothalamus is a master control system embedded in the brain. This thumbnail size organ controls the section that dictate many of the key metabolic functions (ex: water, sugar, fat level, hormones, and temperature). The body dissipates 85% of the heat through skin. If the reading in thermoregulatory section of the hypothalamus says the body is too cold, the capilaries constrict; if the body is too warm, the capilaries dilate.
Evaporation is the key to keep our body cool. Dogs and birds pant to stimulate evaporation from their throats. Bees also use water drops and fanning their wings to stimulate circulation in their nests. The nest can remain at 85 F even if the outside temperature is 160 F with unlimited access of water. When in cold temperature, human elevates its metabolic rates to generate additional heat, and capillaries constrict. Seal has a quarter-inch insulation blubber between its skin and its core. The blubber is permeated by capillary, which will close while the seal is in cold water and open while it is in warm water. It is an active and extraordinarily efficient thermal regulator. The male emperor penguin hatches the egg along as long as two months, after the female layed the egg and returned to the sea. During those two months, they huddle together. The male penguin makes no dramatic changes in metabolism. This may burn up more than a third of his body weight.
A temperature reading above normal is called pyrexia, so called fever. Fever-causing substances are known as pyrogens, which may be bacteria. They stimulate fever by evoking the release cytokines in the host, which are then carried through bloodstream. They produce prostaglandin (messenger), and they eventually reach hypothalamus. The chemical resets the body’s thermostat to a higher temperature, which tricks our body to think we are cold. We can either kill the bacteria that leads to cytokines, or destroy the messenger that tricks us (ex: aspirin). A slightly increase of body temperature enhances the functioning of the immune system. Mammals, birds, the warm-blooded animals, cold-blooded animals (ex: lizard), fishes, insects also react to infection by moving to warmer locations or increasing body temperature. There is no known reason of why we have fever. Perhaps the rise in temperature during infection is one way of stimulating our body to increase hsp (heat shock protein, or so called stress protein), that helps repair our body. The protein can be found in different species universally.
Measure For Measure
In the early 17th century, the telescope, the microscope, the thermometer, and the pendulum clock were invented. The first telescope was made around 1600 by Dutch spectacle makers, but it was Galileo, who first pointed it at the sky on January 7, 1610. The microscope was also invented by Dutch lens makers at the beginning of 17th century. Robert Hooke (much more known for Hooke’s Law) is the first one who use the instrument to look at microscopic objects, and he later published Micrographia with hand-drawn illustrations. Several people (one of them is Galileo) shared the credit for inventing the thermometer. Santorio is one of those people, and he is the first person to systematically measure our body temperature.
Scientists found that if we keep constant pressure, there is a positive correlation between volume and temperature (with a shift). Zero is the smallest number it can take in volume, which gives us the lowest temperature, absolute zero. At the time steam engine was invented, people don’t really understand what heat is. They later found out heat is simply a form of energy, and the sum of all forms of energy in an isolated system is conserved (Thermodynamics’s First Law). The Second Law first shown by Carnot’s Law states that the efficiency of conversion of heat to work in a heat engine has an upper limit. It can be rephrased by the concept of entropy as overall disorder (entropy) always increases. The Third Law states that an object’s entropy goes to zero as its temperature goes to absolute zero. Temperature, absolute zero, molecule’s motion, and energy were later connected by Maxwell (Maxwell-Boltzmann distribution). He applied statistical approach, which he had used it to show that the rings of Saturn were made up of small particles interacting with each other.
Reading The Earth
There are four main contributions to the Earth’s surface temperature. The first is the Sun, our principal source of heat. The second is the heat generated directly in the Earth, like volcanoes and radioactive decay. Potassium-40, thorium-232, uranium-235, and uranium-238 are the source of radioactive isotopes that contribute signifcantly to the Earth’s heat. They concentrate at the outer crust of the Earth, which is why the deeper the mines are the hotter they get. The third is oceans and currents, which are big contributors to global temperature shifts. The fourth is our atmosphere, in which the green house gases trap the heat.
Jean Le Rond d’Alembert had calculate the precession takes 22,000 years to circle around in 1754. After a hundred years, Joseph Alphonse Adhemar, proposed that the precession would lead to ice aages, due to the amount of heat receive is lesser in the winter. He was wrong, because a smaller amount of heat in winter will always be balanced by a larger amount of heat. Adhemar’s idea with later picked up by James Croll. On top of that, James Croll also added feedback mechanism (ex: snowfall, ocean currents) to his statement. (Now known as Milankovitch cycles.) In this case, slight orbital change might trigger an amplified cooling of the Earth, which would not necessarily be balanecd by summer. Snowfall has been pilling up without melting for thousands of years in Greenland and Antarctica. The layers of ice records the chronical history of the Earth’s climate. The data agreed with the cycles, but with surprising events that cannot be explained by the tilting angle of rotation axis.
The Earth’s atmosphere, which acts as a one-way filter, produces greenhouse effect. The three main composition of our atmosphere (nitrogen, oxygen, argon) are transparent to solar radiation. Carbon dioxide has a molecular structure that makes them transparent to solar radiation, but highly absorbent of the infrared radiation from the Earth. If there is no greenhouse gas, the Earth’s average temperature would be 255 $^{\circ}K$, which is 33 $^{\circ}K$ lower. Mars and Venus are two extreme situations. Atmosphere on Mars is so thin that it has a negligible greenhouse effect, and the daily temperature swings from 295 $^{\circ}K$ to 184 $^{\circ}K$. Whereas Venus has too much carbon dioxide, which causes its surface temperature to be 700 $^{\circ}K$.
Controlling greenhouse gas emission is controlling ones economy and development of a country. At the time this book was written, over fifty developing countries have emissions only 4% of that of the United States. The developing countries feel that the developed countries created the problem and that they need to also help solve it. And some oil-rich countries would like to see high levels of oil consumption, so that they can benefit from it. I think recent years, people have started to quantify environmental harm, like carbon coin that restricts how many tons of carbon dioxide can a company emit.
Life In The Extremes
By the 1960s, Alfred Wegener was struck by the idea of the continents were once joined together. The evidences are that the congruity of the eastern shore of South America to the western shore of Africa and the mountain chains on one continent matched those on another. But his theory lacked a plausible mechanism for the motion of continents. We later found that our planet’s outer shell is made up of seven giant slabs and about twenty smaller ones. These slabs rest on strata of semimolten rock that move in giant loops, rising, moving parallel to the surface while cooling, and then finally sinking.
At the location of two separating plates, underwater volcanoes produce hot springs known as hydrothermal vents. The highest recording was 623.15 $^{\circ}K$. The temperature can differ by 330 $^{\circ}K$ between the tip of the opening and the cold seawater an inch away. This small inch of separation constitutes the largest natural temperature gradient on Earth. More than 500 new species were found around this, and some are amazing different from the ones we know. They live without sun, and they live in super hot, large temperature gradient, and lots of minerals environment. Pompejana (also known as Pompeii worm) usually covered with mineral grains formed from the deposits in the hydrothermal vents, has 55 $^{\circ}K$ difference between its head and tail. These kind of creature normally form a symbiotic relationship with the bacteria with extaordinary tolerance to high temperatures. Bacterias that love hot environment are thermophiles. Some in a much more extreme case are called hyperthermophiles, they can even function at boiling point. They are normally found near hydrothermal vents and hot springs. Ordinary enzymes break down at high temperature, but not them. Photosynthesis ceases at 75 $^{\circ} C$. Creatures that live at hydrothemal vent feed on hydrogen sulfide rich nutrients. They free sulfur atoms from the toxic hydrogen sulfide, combine them with carbon dioxide, oxygen, and water, and then obtaining energy by creating sulfate. Sunlight (Photosynthesis) is being replaced by Chemosynthesis (a sulfide-to-sulfate transition).
3.8 billion years ago, single-celled creatures emerged on Earth. And 561 million years ago, all major animal phyla started appearing within a short 50 million years. After that, no new phyla have appeared since then. This sudden burst is known as Cambrian Explosion. The sudden change of global temperature, the rapid shifts of oxygen and carbon dioxide, glacier movements, feedback loops, and the thermophiles may solve this puzzle. Thermophiles can live isolated in the deep ocean on an ice-covered Earth, preserving life.
Archaeabacteria were first discovered and labeled by Carl Woese, while he was tracing RNA residing on bacteria’s intracellular sites and creating a universal bacterial chronometer. It is the third branch of life, alongside with Bacteria and Eukarya. Almost all the archaea discovered in the first few years were thermophiles, but not all of them, some where bacteria. Archaea are abundant and are even found in polars. Perhaps the first microorganisms were thermophilic, but neither simply Archaean nor simply bacterial, and it may be wrong to think life is single rooted.
Messages From The Sun
The energy source of the Sun should be long enough to acount for the geological shaping of the Earth and biological evolution. The Sun’s core is a giant nuclear reactor in which $10^{12}$ pounds of hydrogen nuclei are converted to helium nuclei every second. In order to perform hydrogen-to-helium converstion, the core’s temperature needs to be over $1.5 \times 10^{7}$ $^{\circ} K$.
We measure the Sun’s temperature through neutrino produced at its core (solar neutrino). The neutrino generated rate depends on the Sun’s core temperature. This is because there are no impenetrable barriers using quantum mechanics to explain. Though there is strong force that holds helium nuclei and larger nucleus together, and there is electrical force prevents helium nuclei to get into the larger nucleus, these barriers aren’t impenetrable, and in higher temperature, they act more energetic and thus increase the probability of penetrating the barrier. The detector were full of chlorine (they filled it with cleaning fluid), and it was placed in deep underground to avoid noise. The energetic solar neutrinos very occasionally change a chlorine nucleus into an argon nucleus. During the process, a neutron inside the chlorine nucleus turns into a proton.
The chain of nuclear reactions (until Fe) generate energy. These elements owe their existence to nuclear reaction in sun’s core. Through explosions after sun’s death, they are scattered through out the universe. During the core’s collapse, electrons and protons are squeezed together, each pair forming a neutron and neutrino. The density is so high that it takes 10 seconds for neutrinos to leave its core, normally, it only needs a microsecond. These neutrinos reach thermal equilibrium and carry memory of the temperature.
At the early universe, the number of neutrons and protons are equal. But the neutron will decay into a proton, an electron, and a neutrino, unless it is locked inside a nuclei (not the radioactive nuclei). Neutrons and protons combine and form helium nuclei four minutes after the universe’s birth, when the strong force has overcome the temperature. The ratio of hydrogen to helium nuclei was set once and for all at roughly $10:1$. Hydrogen and helium atoms formed when temperature dropped to 3000 $^{\circ} K$. And this was the last time the universe’s visible matter was in thermal equilibrium.
Photons continue to interact with protons and electrons and maintained thermal equilibrium, until atoms are formed and they ceased to interact with their surroundings. Photons were stretched by the universe’s expansiion and then were leave unpertubed through the universe for the last fifteen billion years, leaving us the cosmic microwave background of $2.735$ $^{\circ} K$. Unlike photons, neutrinos can still interact with matters through weak interaction. When the time scale of weak interaction were slower than the expansion, neutrino ceased to interact with others and left us roughly $2.$ $^{\circ} K$.
The Quantum Leap
There once was a competetion of liquifiying every all known gas. Helium was the last one to be liquified. People started using these liquified Helium to study how matter behaves slightly above absolute zero. Resistence is known to decrease and conductivity increase as temperature drops when approaching absolute zero, but this is not the case for superconductors. The resistense decrease continuously, but once it passes the critical temperature, the resistence drop to 0 abruptly.
In classical physics, motion comes smoothly to an end as absolute zero is approached. But quantum mechanically, smoothness is impossible, it is quantized. The jump from one quantum configuration to another grows in significance as temperature drops, and discontinuities start to prevail. Uncertainty principle also points out that as temperature drops, velcity drops, and it becomes difficult to know where their position is. Interesting things starts to appear. For bosons, when large amount of bosons occupy the lowest energy states at low temperature, all the wave function interference together, and the microscopic quantum mechanical phenomanon becomes macroscopic.