Galen

Galen, the most outstanding physician of antiquity after Hippocrates. His anatomical studies on animals and observations of how the human body functions dominated medical theory and practice for 1400 years. Galen was born of Greek parents in Pergamum, Asia Minor, which was then part of the Roman Empire. A shrine to the healing god Asclepius was located in Pergamum, and there young Galen observed how the medical techniques of the time were used to treat the ill or wounded. He received his formal medical training in nearby Smyrna and then traveled widely, gaining more medical knowledge. About 161 he settled in Rome, where he became renowned for his skill as a physician, his animal dissections, and his public lectures. About 169, the Roman emperor Marcus Aurelius appointed Galen as the physician to his son Lucius Aelius Aurelius Commodus. Most of Galen's later life was probably spent in Rome.

Galen dissected many animals, particularly goats, pigs, and monkeys, to demonstrate how different muscles are controlled at different levels of the spinal cord. He noted the functions of the kidney and bladder and identified seven pairs of cranial nerves. He also showed that the brain controls the voice. Galen showed that arteries carry blood, disproving the 400-year-old belief that arteries carry air. Galen also described the valves of the heart and noted the structural differences between arteries and veins, but fell short of conceiving that the blood circulates. Instead, he held the erroneous belief that the liver is the central organ of the vascular system, and that blood moves from the liver to the periphery of the body to form flesh.

Galen was also highly praised in his time as a philosopher. In his treatise On the Uses of the Parts of the Body of Man he closely followed the view of the Greek philosopher Aristotle that nothing in nature is superfluous. Galen's principal contribution to philosophic thought was the concept that God's purposes can be understood by examining nature.

Galen's observations in anatomy remained his most enduring contribution. His medical writings were translated by 9th-century Arab thinkers and became highly esteemed by medical humanists of Renaissance Europe. Galen produced about 500 tracts on medicine, philosophy, and ethics, many of which have survived in translated form.

Gabriello Fallopio

Gabriello Fallopio (1523?-1562), also known as Gabriello Fallopio and Gabriel Fallopius, Italian anatomist, physician, botanist, and surgeon. Born in Modena, Fallopio studied medicine at the University of Ferrara, and after receiving his degree he worked and studied at various European medical schools. Fallopio became professor of anatomy at Ferrara in 1548 and professor of surgery and anatomy at the University of Pisa about a year later. In 1551 Cosimo I dè Medici, grand duke of Tuscany, called him to a similar post at Pisa to succeed Andreas Vesalius, the Belgian anatomist. There he also held the chair of botany and materia medica and was superintendent of the botanical gardens.

Fallopio's work dealt primarily with cranial anatomy and he added considerably to the knowledge of the ear. He was the first to use the ear speculum instrument to diagnose diseases of the ear and the first to show the connection between the mastoid, a part of the skull that houses the ear, and the middle ear.

His discoveries included the sphenoidal sinuses; the chorda tympani; the canal through which the facial nerve passes after it leaves the auditory, called the Fallopian aqueduct; and the ducts leading from the ovaries to the uterus known as the fallopian tubes. He also named the hard palate, the soft palate, the placenta, and the vagina. 

In addition to his work as a surgeon and educator, Fallopio was also a distinguished botanist, and he made important contributions to practical medicine. He was a strong opponent and vocal critic of the theories of Galen, the Greek physician who proposed that the liver is the central organ of the vascular system. His writings included treatises on tumors, ulcers, surgery, the composition of drugs, simple purgatives, thermal waters and baths, a commentary on Wounds in the Head by the Greek physician Hippocrates, and a study on syphilis, De morbo gallico (1564). His best known work was Observationes anatomicae (1561), and his complete works appeared for the first time in Venice in 1584.

Forestry

Forestry is the art and science of managing forests, tree plantations, and related natural resources. The main goal of forestry is to create and implement systems that allow forests to continue a sustainable continuation of environmental supplies and services. The challenge of forestry is to create systems that are socially accepted while sustaining the resource and any other resources that might be affected.

Silviculture, a related science, involves the growing and tending of trees and forests. Modern forestry generally embraces a broad range of concerns, including assisting forests to provide timber as raw material for wood products, wildlife habitat, natural water quality management, recreation, landscape and community protection, employment, aesthetically appealing landscapes, biodiversity management, watershed management, erosion control, and preserving forests as 'sinks' for atmospheric carbon dioxide. A practitioner of forestry is known as a forester.

Forest ecosystems have come to be seen as the most important component of the biosphere, and forestry has emerged as a vital field of science, applied art, and technology.

Lorentz contraction

Lorentz contraction (lôr`ĕnts), in physics, contraction or foreshortening of a moving body in the direction of its motion, proposed by H. A. Lorentz on theoretical grounds and based on an earlier suggestion by G. F. Fitzgerald; it is sometimes called the Fitzgerald, or Lorentz-Fitzgerald, contraction. The Lorentz contraction hypothesis was put forward in an attempt to explain the negative result of the Michelson-Morley experiment of 1887 designed to demonstrate the earth's absolute motion through space (see ether; relativity). The hypothesis held that any material body is contracted in the direction of its motion by a factor 1−v²/c², where v is the velocity of the body and c is the velocity of light. Although the Lorentz contraction did not succeed entirely in reconciling the results of the Michelson-Morley experiment with classical theory, it did serve as the basis for the mathematics of Einstein's theory of relativity. The equations used in relativity theory to change from a coordinate system, or frame of reference, in which the observer is at rest to a second system that is moving at constant velocity with respect to the first system are known as the Lorentz transformation. The Lorentz transformation will result in a stationary observer recording an effect equivalent to the Lorentz contraction when observing an object in uniform motion relative to his system of coordinates. Einstein showed, however, that this effect is due not to the actual deformation of the body in question, as Lorentz had originally supposed, but to a change in the way space and time are measured.

Atomic clock

Atomic clock, electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillates at a uniform rate to control the rate of movement of its hands or the rate of change of its digits. Mechanical clocks and watches use oscillating balance wheels, pendulums, and tuning forks. Much greater accuracy can be attained by using the oscillations of atoms or molecules. Because the frequency of such oscillations is so high, it is not possible to use them as a direct means of controlling a clock. Instead, the clock is controlled by a highly stable crystal oscillator whose output is automatically multiplied and compared with the frequency of the atomic system. Errors in the oscillator frequency are then automatically corrected. Time is usually displayed by an atomic clock with digital or other sophisticated readout devices.

The first atomic clock, invented in 1948, utilized the vibrations of ammonia molecules. The error between a pair of such clocks, i.e., the difference in indicated time if both were started at the same instant and later compared, was typically about one second in three thousand years. In 1955 the first cesium-beam clock (a device that uses as a reference the exact frequency of the microwave spectral line emitted by cesium atoms) was placed in operation at the National Physical Laboratory at Teddington, England. It is estimated that such a clock would gain or lose less than a second in three million years. The U.S. standard is the NIST-F1, which went into service in 1999 and should neither gain nor lose a second in 20 million years. A fountain atomic clock, the NIST F-1 consists of a 3-foot vertical tube inside a taller structure. It uses lasers to cool cesium atoms, forming a ball of atoms that lasers then toss into the air, much like one would toss a tennis ball, creating a fountain effect. This allows the atoms to be observed for much longer than could be done with any previous clock.

Many of the world's nations maintain atomic clocks at standards laboratories, the time kept by these clocks being averaged to produce a standard called international atomic time (TAI). Highly accurate time signals from these standards laboratories are broadcast around the globe by shortwave-radio broadcast stations or by artificial satellites, the signals being used for such things as tracking space vehicles, electronic navigation systems, and studying the motions of the earth's crust. The accuracy of these clocks made possible an experiment confirming an important prediction of Einstein's theory of relativity. Prototypes of atomic clocks using atoms such as hydrogen or beryllium could be still thousands of times more accurate. For example, researchers at the U.S. National Institute of Standards and Technology have demonstrated an atomic clock based on an energy transition in a single trapped mercury ion (a mercury atom that is missing one electron) that has the potential to be up to 1,000 times more accurate than current atomic clocks.