SEE ALSO Nitrogen Cycle and Plant Chemistry (1837), Darwin’s Theory of Natural Section (1859), Food Webs (1927)
In this example of mutualism, a cleaner shrimp is cleaning parasites from the mouth of a moray eel. The fish benefits by having the parasites removed, and the shrimp gains the nutritional value of the parasites.
1859
Kinetic Theory • Clifford A. Pickover
James Clerk Maxwell (1831–1879), Ludwig Eduard Boltzmann (1844–1906)
Imagine a thin plastic bag filled with buzzing bees, all bouncing randomly against one another and the surface of the bag. As the bees bounce around with greater velocity, their hard bodies impact the wall with greater force, causing it to expand. The bees are a metaphor for atoms or molecules in a gas. The kinetic theory of gases attempts to explain the macroscopic properties of gases—such as pressure, volume, and temperature—in terms of the constant movements of such particles.
According to kinetic theory, temperature depends on the speed of the particles in a container, and pressure results from the collisions of the particles with the walls of the container. The simplest version of kinetic theory is most accurate when certain assumptions are fulfilled. For example, the gas should be composed of a large number of small, identical particles moving in random directions. The particles should experience elastic collisions with themselves and the container walls but have no other kinds of forces among them. Also, the average separation between particles should be large.
Around 1859, physicist James Clerk Maxwell developed a statistical treatment to express the range of velocities of gas particles in a container as a function of temperature. For example, molecules in a gas will increase speed as the temperature rises. Maxwell also considered how the viscosity and diffusion of a gas depend on the characteristics of the molecules’ motion. Physicist Ludwig Boltzmann generalized Maxwell’s theory in 1868, resulting in the Maxwell-Boltzmann distribution law, which describes a probability distribution of particle speeds as a function of temperature. Interestingly, scientists still debated the existence of atoms at this time.
We see the kinetic theory in action in our daily lives. For example, when we inflate a tire or balloon, we add more air molecules to the enclosed space, which results in more collisions of the molecules on the inside of the enclosed space than there are on the outside. As a result, the enclosure expands.
SEE ALSO Atomic Theory (1808), Brownian Motion (1827), Boltzmann’s Entropy Equation (1875)
According to kinetic theory, when we blow a soap bubble, we add more air molecules to the enclosed space, leading to more molecular collisions on the bubble’s inside than on the outside, causing the bubble to expand.
1859
Riemann Hypothesis • Clifford A. Pickover
Georg Freidrich Bernhard Riemann (1826–1866)
Many mathematical surveys indicate that the “proof of the Riemann hypothesis” is the most important open question in mathematics. The proof involves the zeta function, which can be represented by a complicated-looking curve that is useful in number theory for investigating properties of prime numbers. Written as ζ(x), the function was originally defined as the infinite sum ζ(x) = 1 + (1/2)x + (1/3)x + (1/4)x + . . .etc. When x = 1, this series has no finite sum. For values of x larger than 1, the series adds up to a finite number. If x is less than 1, the sum is again infinite. The complete zeta function, studied and discussed in the literature, is a more complicated function that is equivalent to this series for values of x greater than 1, but has finite values for any real or complex number, except for when the real part is equal to 1. We know that the function equals zero when x is −2, −4, −6,. . . and that the function has an infinite number of zero values for the set of complex numbers, the real part of which is between zero and one—but we do not know exactly for what complex numbers these zeros occur. Mathematician Georg Bernhard Riemann conjectured that these zeros occur for those complex numbers the real part of which equals 1/2. Although vast numerical evidence exists that favors this conjecture, it is still unproven. The proof of Riemann’s hypothesis would have profound consequences for the theory of prime numbers and in our understanding of the properties of complex numbers. Amazingly, physicists may have found a mysterious connection between quantum physics and number theory through investigations of the Riemann Hypothesis.
Around the year 2005, over 11,000 volunteers worldwide worked on the Riemann Hypothesis, using a distributed computer software package, as part of project ZetaGrid, to search for the zeros of the Riemann zeta function. More than 1 billion zeros for the zeta function were calculated every day. The investigators found no counterexample to the Riemann hypothesis.
SEE ALSO Sieve of Eratosthenes (c. 240 BCE) Imaginary Numbers (1572), Hilbert’s 23 Problems (1900), Proof of the Kepler Conjecture (2017).
Tibor Majlath’s rendition of the Riemann zeta function ζ(s) in the complex plane. The four small bulls-eye patterns at top and bottom correspond to zeros at Re(s) = ½. The plot extends from −32 to +32 in the real and imaginary directions.
1861
Cerebral Localization • Clifford A. Pickover
Hippocrates of Cos (460 BCE–377 BCE), Galen of Pergamon (129–199), Franz Joseph Gall (1758–1828), Pierre Paul Broca (1824–1880), Gustav Theodor Fritsch (1838–1927), Eduard Hitzig (1839–1907), Wilder Graves Penfield (1891–1976), Herbert Henri Jasper (1906–1999)
The ancient Greek physician Hippocrates was aware that the brain comprised the physical material underlying thoughts and emotions, and the Greek physician Galen declared, “Where the origin of the nerves is, there is the command of the soul.” However, it wasn’t until the 1800s that advanced research was performed with respect to cerebral localization—that is, the idea that different areas of the brain are specialized for different functions.
In 1796, German neuroanatomist Franz Joseph Gall conjectured that the brain should be considered as a mosaic of suborgans, each specialized to deal with various mental faculties, such as language, music, and so forth. However, he made the mistake of promoting the idea that the relative size and efficiency of these various suborgans could be inferred from the size of the overlying areas and bumps of the skull.
In 1861, French physician Pierre Broca discovered a particular region of the brain used for speech production. His findings were based on examination of two patients who had lost the ability to speak after injury to a particular region located on the frontal part of the left hemisphere of the brain, which today we refer to as Broca’s area. Interestingly, gradual destruction of Broca’s area by, for example, a brain tumor can sometimes preserve significant speech functionality, which suggests that speech function can shift to nearby areas in the brain.
Additional important evidence for cerebral localization was provided around 1870 from German researchers Gustav Fritsch and Eduard Hitzig, whose experiments on dogs showed that local body movement could be elicited by electrical stimulation of specific brain areas. In the 1940s, Canadian researchers Wilder Penfield and Herbert Jasper continued investigations involving electrical stimulation of a brain hemisphere’s motor cortex, which produced contractions on the opposite side of the human body. They also created detailed functional maps of the brain’s motor areas (which control voluntary muscle movement) and sensory areas.
SEE ALSO Morgagni’s “Cries of Suffering Organs” (1761), Neuron Doctrine (1891), Brain Lateralization (1964).
The cerebral cortex includes the frontal lobe (red), parietal lobe (yellow), occipital lobe (green), and temporal lobe (blue-green). The frontal lobe is responsible for “executive functions” such as planning and abstract thinking. The cerebellum (purple) is the region at the bottom.
1861
Maxwell’s Equations • Clifford A. Pickover
James Clerk Maxwell (1831–1879)
“From a long view of the history of mankind,” writes physicist Richard Feynman, “seen from, say, ten thousand years from now—there can be no doubt that the most significant event of
the 19th century will be judged as Maxwell’s discovery of the laws of electrodynamics. The American Civil War will pale into provincial insignificance in comparison with this important scientific event of the same decade.”
In general, Maxwell’s Equations are the set of four famous formulas that describe the behavior of the electric and magnetic fields. In particular, they express how electric charges produce electric fields and the fact that magnetic charges cannot exist. They also show how currents produce magnetic fields and how changing magnetic fields produce electric fields. If you let E represent the electric field, B represent the magnetic field, ε0 represent the electric constant, μ0 represent the magnetic constant, and J represent the current density, you can express Maxwell’s equations thus:
Note the utter compactness of expression, which led Einstein to rate Maxwell’s achievement on a par with that of Isaac Newton’s. Moreover, the equations predicted the existence of electromagnetic waves.
Philosopher Robert P. Crease writes of the importance of Maxwell’s equations: “Although Maxwell’s equations are relatively simple, they daringly reorganize our perception of nature, unifying electricity and magnetism and linking geometry, topology and physics. They are essential to understanding the surrounding world. And as the first field equations, they not only showed scientists a new way of approaching physics but also took them on the first step towards a unification of the fundamental forces of nature.”
SEE ALSO Ampère’s Law of Electromagnetism (1825), Faraday’s Laws of Induction (1831), Theory of Everything (1984).
LEFT: Mr. and Mrs. James Clerk Maxwell, 1869. RIGHT: Computer core memory of the 1960s can be partly understood using Ampere’s Law in Maxwell’s Equations, which describes how a current-carrying wire produces a magnetic field that circles the wire and, thus, can cause the core (doughnut shape) to change its magnetic polarity.
1862
Germ Theory of Disease • Clifford A. Pickover
Marcus Terentius Varro (116 BCE–27 BCE), Louis Pasteur (1822–1895)
To our modern minds, it is obvious that germs cause disease. We chlorinate our drinking water, use antibiotic ointments, and hope our doctors wash their hands. We are fortunate that the French chemist and microbiologist Louis Pasteur conducted his pioneering research into the causes and preventions of disease—and for experiments that supported the germ theory of disease, which suggests that microorganisms are the cause of many diseases.
In one famous experiment, conducted in 1862, Pasteur demonstrated that the growth of bacteria in sterilized nutrient broths is not due to spontaneous generation—a theory that suggests that life often arises from inanimate matter. For example, no organisms grew in flasks that contained a long, thin, twisting neck that made it extremely unlikely for dust, spores, and other particles to enter the broth. Only when Pasteur’s flasks were broken open did organisms begin to grow in the medium. If spontaneous generation were valid, the broth in the curved-neck flasks would have eventually become infected because the germs would have spontaneously generated.
During his career, Pasteur studied fermentation in wines and diseases in sheep and silkworms. He created a vaccination for rabies. He showed that pasteurization (heating of a beverage to a specific temperature for a period of time) diminished microbial growth in food. In his studies of anthrax, he showed that even extremely diluted solutions of bacteria from infected animal blood could kill animals if the bacteria were allowed to multiply in the culture medium before injection into animals.
Pasteur was far from the first individual to suggest that invisible creatures caused diseases. Even the Roman scholar Marcus Terentius Varro published in 36 BCE a warning for people living too close to swamps, “because there are bred certain minute creatures which cannot be seen by the eyes, which float in the air and enter the body through the mouth and nose and there cause serious diseases.” However, the breadth of Pasteur’s scientific experiments into microbial causes of disease revolutionized medicine and public health.
SEE ALSO Micrographia (1665), Semmelweis’s Hand Washing (1847), Cell Division (1855), Antiseptics (1865), Chlorination of Water (1910).
Color-enhanced scanning electron micrograph showing Salmonella typhimurium (red) invading cultured human cells (courtesy of Rocky Mountain Laboratories, NIAID, and NIH). Salmonella causes illnesses such as typhoid fever and food-borne illnesses.
1864
Electromagnetic Spectrum • Clifford A. Pickover
Frederick William Herschel (1738–1822), Johann Wilhelm Ritter (1776–1810), James Clerk Maxwell (1831–1879), Heinrich Rudolf Hertz (1857–1894)
The electromagnetic spectrum refers to the vast range of frequencies of electromagnetic (EM) radiation. It is composed of waves of energy that can propagate through a vacuum and that contain electric and magnetic field components that oscillate perpendicular to each other. Different portions of the spectrum are identified according to the frequency of the waves. In order of increasing frequency (and decreasing wavelength), we have radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.
We can see light with wavelengths between 4,000 and 7,000 angstroms, where an angstrom is equal to 10−10 meters. Radio waves may be generated by electrons that move back and forth in transmission towers and have wavelengths ranging from several feet to many miles. If we represent the electromagnetic spectrum as a 30-octave piano, in which the wavelength of radiation doubles with each octave, visible light occupies only part of an octave. If we wanted to represent the entire spectrum of radiation that has been detected by our instruments, we would need to add at least 20 octaves to the piano.
Extraterrestrials may have senses beyond our own. Even on the Earth, we find examples of creatures with increased sensitivities. For example, rattlesnakes have infrared detectors that give them “heat pictures” of their surroundings. To our eyes, both the male and female Indian luna moths are light green and indistinguishable from each other, but the luna moths themselves perceive the ultraviolet range of light. Therefore, to them, the female looks quite different from the male. Other creatures have difficulty seeing the moths when they rest on green leaves, but luna moths are not camouflaged to one another; rather, they see each other as brilliantly colored. Bees can also detect ultraviolet light. In fact, many flowers have beautiful patterns that bees can see to guide them to the flower. These attractive and intricate patterns are totally hidden from human perception.
The physicists listed at the top of this entry played key research roles with respect to the electromagnetic spectrum.
SEE ALSO Newton’s Prism (1672), Wave Nature of Light (1801), X-rays (1895), Cosmic Microwave Background (1965).
To our eyes, male and female luna moths are light green and indistinguishable from each other. But the luna moths themselves perceive in the ultraviolet range of light, and to them the female looks quite different from the male.
1865
Antiseptics • Clifford A. Pickover
William Henry (1775–1836), Ignaz Philipp Semmelweis (1818–1865), Louis Pasteur (1822–1895), Joseph Lister (1827–1912), William Stewart Halsted (1852–1922)
In 1907, the American physician Franklin C. Clark wrote, “Three notable events characterize the history of medicine, each of which in turn has completely revolutionized the practice of surgery.” The first event involved the use of ligatures to stem the flow of blood during surgeries—for example, as performed by the French surgeon Ambroise Paré. The second involved methods for decreasing pain through general anesthetics such as ether, attributed to several Americans. The third concerned antiseptic surgery, which was promoted by British surgeon Joseph Lister. Lister’s use of carbolic acid (now called phenol) as a means for sterilizing wounds and surgical instruments dramatically reduced postoperative infections.
Louis Pasteur’s work on the germ theory of disease provided a stimulus for Lister to use carbolic acid in an attempt to destroy microorganisms. In 1865, he successfully treated a compou
nd fracture of the leg, in which the bone juts through the skin, by dressing the leg with cloths dipped in carbolic acid solutions. Lister published his findings in the paper “Antiseptic Principle of the Practice of Surgery” in 1867.
Lister was not the first to suggest various forms of sterilization. For example, the British chemist William Henry advised sterilization of clothing through heating, and Hungarian obstetrician Ignaz Semmelweis advocated hand washing to prevent the spread of disease by physicians. Nevertheless, Lister’s slopping of carbolic acid onto open wounds usually prevented the development of the horrific infections that so often occurred in hospitals of his time. His writings and talks convinced medical professionals of the need for using antiseptics.
Antiseptics are usually applied directly to the body surface. Modern methods for preventing infections focus more on the use of aseptic methods that involve sterilization to remove bacteria before they come near a patient (e.g., disinfection of equipment and the use of surgeons’ masks). Antibiotic drugs are also used today to fight internal infections. In 1891, William Halsted pioneered the use of rubber gloves in surgery.
SEE ALSO Semmelweis’s Hand Washing (1847), Germ Theory of Disease (1862), Chlorination of Water (1910), Penicillin (1928).
Manuka honey has been shown to have antibacterial properties that assist in wound healing. Such honey is made by bees in New Zealand that feed on the manuka bush, Leptospermum scoparium.
The Science Book Page 17
