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"The word physics comes from the Greek word physika meaning pertaining to nature. Physics can be considered the most basic of the sciences. Ernest Rutherford, a prominent physicist of the early twentieth century, who ironically received the 1908 Nobel Prize in chemistry for his work on the structure of the atom, said all science is either physics or stamp collecting. While other scientific disciplines have developed in the last three hundred years, physics is the foundation of all science.
Each of us is subject to the laws of physics and physics attempts to explain basic phenomena such as gravity, electricity, sound, light, and heat. Physics applications constantly surround us as we go about our daily activities." (p.XI)
"Throughout life, each of us has been conditioned to accept, without thought, regular patterns as we conduct our daily business. The Sun rises in the morning and sets at night, dropped objects fall to the ground, water flows downhill, and an ice cube melts when taken out of the freezer. We know that a window will shatter when stuck by a baseball hit by a line drive, and if we live in a glass house it is best to throw nerf balls. The universe constantly reveals its behavior as we go about our daily lives. Conversely, we accept other facts based not on direct experience, but on the authority of others. At times, these facts even contradict our experience and direct observation. For example, it is difficult to comprehend that as you read this book you are sitting on a roughly spherical object rotating at a speed of approximately 800 miles per hour. (This assumes you are reading in the continental United Sates. In Alaska, the speed is only about 500 miles per hour, while at the equator it is just over 1,000 miles per hour.) In addition to its rotation, the Earth is also revolving around the Sun at a speed close to 67,000 miles per hour, and the entire solar system is moving around the center of our Milky Way galaxy at more than 500,000 miles per hour.
The several examples cited above illustrate the science of physics. Physics involves the study of matter and energy in its different forms, and the transformation of matter and energy. This same definition might also apply to chemistry, and the two disciplines are closely related. Chemists tend to focus more on the specific characteristics of matter and how different forms of matter are transformed into other forms of matter. Chemists tend to treat matter and energy as separate entities. Physicists are concerned with the general properties that govern all of matter and energy, and in this sense a clear distinction between the two is unnecessary.
As the quote at the beginning of this chapter states, physics involves trying to explain everyday experience in the simplest terms. The science of physics is a continual quest to explain the behavior of the universe using relatively few basic principles. These basic principles should be applicable to all scales of matter ranging from fundamental particles (quarks) and atoms to galaxies. In a sense, physics can be thought of as the search for a general explanation for everything. During physics' history there have been periods when physicists have claimed they were on the verge of knowing everything needed to explain the universe. For instance, the confidence in Newtonian mechanics at the end of the nineteenth century caused some physicists to claim that little remained to be discovered and this heralded the end of physics. Shortly thereafter, relativity and quantum mechanics gave rise to modern physics." (pp.1-2)
"Theoretical physicists use the laws of physics to refine theories, suggest experiments, and predict the results of experiments. Albert Einstein can be thought of as the quintessential theoretical physicist. Einstein's laboratory was his mind. Einstein didn't conduct experiments in the classical sense of using instruments to collect data, but used the body of physics knowledge available at the beginning of the twentieth century to introduce new ideas to explain both old and new observations. As the name implies, experimental physicists design and conduct experiments to test hypotheses and verify theories. Theoretical and experimental physics should not be viewed as distinct areas, but as different strategies for understanding the universe. The interaction between theoretical and experimental physics is critical to the advancement of the science as a whole. Theoretical physicists use the results of experiments to refine their ideas and at the same time suggest new experiments. Experimental physicists, likewise, use refined theories to modify techniques and develop new experiments.
Applied physics is concerned with using physics to meet societal needs. The twenty-first century's modern life is largely a product of applied physics. Modern society uses applied physics to produce a plethora of simple products and integrated engineered systems. A toaster applies the concept of electrical resistance. Cars are the result of applying thermodynamics (internal combustion engine), aerodynamics (design), material science (body, tires, windshield), electronics (ignition and diagnostics), and mechanics (brakes, transmission). Air transportation exists in its present form due to the application of fluid mechanics, in the form of the Bernoulli principle, to achieve lift. The modern information age is intimately connected to applied physics. This is exemplified by prestigious physics labs operated by large companies such as Bell and IBM." (p.2)
"Classical physics refers to the body of knowledge that began to define physics as a discipline starting in the Renaissance. Galileo Galilei (1564-1642) and Isaac Newton (1643-1727) were the two key figures who established the foundation of classical physics. Classical physics is often defined as physics developed up to the year 1900. Classical physics deals primarily with familiar phenomena and macroscopic objects. Classical physics is perfectly adequate for describing everyday observations. If we want to know how fast to drive to make a green light or how long it takes for a dropped object to strike the floor, equations developed hundreds of years ago can be used to make accurate calculations. The laws of classical physics were questioned starting in the late nineteenth century, as paradoxical results were obtained from experiments exploring light and atomic structure. These paradoxes led to the development of modern physics. Modern physics allows physicists to address questions of nature outside the realm of everyday experience. Relativistic and quantum principles from modern physics are needed to explain observations on objects approaching the speed of light or the behavior of matter in an extreme gravitational field, such as a black hole.
Classical and modern physics should not be viewed as distinct branches of physics but as different levels for understanding natural phenomena. [...]
Classical physics can be divided into several main branches. These include mechanics, thermodynamics, electromagnetism, sound, and optics. Mechanics is the study of motion (or lack of motion). The pure description of motion is termed kinematics. Dynamics is the study of changes in motion and the forces associated with this change. Mechanics has enabled scientists and engineers to put men on the Moon, design intricate mechanical devices, and populate all areas of the Earth. The tern "mechanics" also appears with other terms to further delineate mechanics. Fluid mechanics deals with the motion of liquids and gases. Quantum mechanics is an area of modern physics that enables physicists to describe the structure and behavior of atoms.
Thermodynamics is the study of various forms of energy and how energy is transformed. It involves the study of heat. The first law of thermodynamics states that energy cannot be created or destroyed, while the second law dictates the natural flow of energy in a system. These basic laws can be used to calculate the amount of work that can be obtained from a given amount of energy and to determine the efficiency of a process. By applying the laws of thermodynamics, humans continually convert both nonrenewable (fossil fuels) and renewable (hydroelectric, solar, biomass, etc.) resources into energy to fuel modern society. The industrial revolution in the nineteenth century owes its start to the ability to apply thermodynamics to develop industrial machines." (pp.2-3)
"Electromagnetism is the study of the related phenomena of electricity and magnetism. The movement of electric charge produces a magnetic field, and the movement of a conductor, such as wire, through a magnetic field produces an electric current. The study of electromagnetism deals with the propagation of electromagnetic waves through space. Society changed drastically as humans built vast networks to deliver electricity throughout developed countries at the beginning of the twentieth century. The modern information age with its plethora of electronic devices and global communication networks is based on harnessing electromagnetism for society's use.
Sound is the vibration of air and the propagation of sound waves through space. The study of sound, how it's created, and its interaction with the environment is termed acoustics. Human communication—speech and hearing—is based on sound. Sound waves, in the form of sonar, can be used to probe beneath the sea. Acoustics is used to design musical instruments and the grand concert halls that house the musicians that play in them.
Optics is the study of light and, in this sense, may be considered a branch of electromagnetism. Geometrical optics deals with the tracing of light rays, how they travel, and how objects affect them. The use of corrective lenses (glasses or contacts) is probably the most common example of geometrical optics. The behavior of light as an electromagnetic wave is referred to as physical optics.
Physics combined with other disciplines produces unique areas of study. Geophysics is physics of the Earth. Geophysicists use physics to study both the external and internal structure of the Earth. Biophysics applies the principles of physics to the study of life processes, for example, using thermodynamics to study metabolism. Astrophysics applies physics to the study of the universe. The evolution of stars, the propagation of electromagnetic waves through interstellar space, and the structure of the universe are just a few areas that astrophysics addresses. Many distinct areas of science are highly dependent on physics. For example, meteorologists use physics to study the motion of the atmosphere and to understand weather patterns. Oceanographers apply physics to study wave motion and water circulation throughout the oceans. Engineers constantly apply physics to carry out tasks such as building bridges, designing cars, and refining oil." (p.4)
"The roots of physics, as well as other scientific disciplines, can be traced back to this period of the pre-Socratic Greek philosophers. Miletus, located on Turkey's western shore of the Aegean Sea, was the center of early Greek philosophy. Miletus was ideally situated as a trading port where Babylonian and Egyptian learning could be integrated with Greek thought. It was in Miletus that pre-Socratic philosophers started to integrate rational logic into traditional Greek mythology to explain their world. Gods and supernatural causes were removed from natural explanations. A major area the pre-Socratic philosophers focused upon was the relationship between change and life. Life was interpreted in a holistic sense by the early Geeks. In contrast to the modern view of the world consisting of living and nonliving entities, objects such as stones, water, and fire were seen as biotic components of the world. For example, the Greeks believed the Earth gave birth to rocks deposited on the Earth's surface through volcanic eruptions. Thus, a volcano was similar to a woman in labor.
Coupled with the idea of life and change, was the belief of a primordial substance that formed all matter. Thales of Miletus (624-546 B.C.E.) believed water was this primordial substance. His thoughts on water as the essence of life were probably influenced by Egyptian and Babylonian contacts he met in his travels throughout the region. The idea of water as the basic element was appealing to the early Miletian philosophers. After all, water could exist in three forms—solid, liquid, and gas—that readily changed from one to another. The deposition of sediments out of water in deltas gave evidence that Earth itself sprang forth from water." (p.5)
"Natural philosophy did not hold a central place in Plato's philosophy. Plato held a Pythagorean view of the universe, believing that mathematics was the key to understanding nature. He reasoned that the four basic elements consisted of geometrical shapes. Fire consisted of tetrahedral particles, air particles were octahedral, water particles were icosahedra, and earth particles consisted of cubes. The heavens consisted of a fifth element, quintessence, which came from dodecahedra. Plato accepted the view that the Earth and planets were perfect spheres and moved in uniform circular motion. Because mathematics held a central place in Plato's philosophy, arithmetic, geometry, and astronomy were studied as branches of mathematics. In this regard, astronomy served to develop mathematical constructs, rather than to explain observation of the heavens. Astronomical observations made by Plato and his students served to reveal the basic truths contained in the mathematics. Plato's simple model of the universe described in his Timeaus consisted of two crystalline spheres. An outer sphere that contained the fixed stars that rotated around the earth once every 23 hours 56 minutes, and a solar sphere that rotated once every 24 hours and contained the Sun. Beyond the crystalline sphere containing the stars was an infinite void. Between the Earth and the stars, the planets—the term itself means wanderers—moved." (pp.6-7)
"Aristotle's Meterologica synthesized his ideas on matter. Aristotle believed that four qualities could be used to explain natural processes: hot, cold, dry, and moist. Hot and cold were active qualities. Hence, the addition or subtraction of heat leads to the transformation of things. Moist and dry were the result of the action of the active qualities.
Only four possible combinations of these qualities could exist in substances: hot and moist, hot and dry, cold and moist, and cold and dry. Opposite qualities could not coexist. The combinations of hot and cold or moist and dry were impossible in Aristotle's system. The four allowable combinations determined the four basic elements. Air possessed the qualities hot and moist, fire possessed hot and dry, earth possessed dry and cold, and water possessed wet and cold. Aristotle's system is summarized in Figure 1.1 and is found in a number of ancient writings.
Using the four qualities of matter and four elements as a starting point, Aristotle developed logical explanations for numerous natural observations. Both the properties of matter and changes in matter could be explained using Aristotle's theory. Aristotle explained the process of boiling as a combination of moisture and heat. If heat is added to a substance that contains moisture, the heat will draw the moisture out. The process results in the substance dividing into two parts. When the moisture leaves, the substance becomes thicker, while the separated moisture is lighter and rises. Aristotle used this type of reasoning to explain numerous physical and chemical processes including evaporation, decay, condensation, melting, drying, and putrefaction. While Aristotle's philosophy explained much, it did have its shortcomings. A simple example will help to illustrate how problems arise with any scientific theory. According to Aristotle, hard substances were hard because they had an abundance of earth and possessed the qualities of dry and cold. Aristotle claimed earth was heavy and so it moved down. Soft substances would not contain as much earth, but contained more water and air. These substances would not be attracted downward as strongly. Now consider ice and liquid water. Ice is dry and cold compared to liquid water, which is moist and cold. We would expect ice to have more of the element earth, and have a stronger downward attraction than liquid water. Yet, hard solid ice floats in liquid water. Even though many other problems existed with Aristotle's theory, it provided reasonable explanations for many observations.
Aristotle's system could also be used to explain the motion of objects. He explained his views on motion in his work Physics. Natural motion was the result of an object seeking its "natural" place in the universe. Solid objects, such as rocks, fell because they contained an abundance of Earth and desired to return to the Earth. Conversely, smoke rose because it had an abundance of air. Violent motion was motion that opposed natural motion. For example, a rock can be lifted or thrown upward. According to Aristotle, violent motion required an agent in contact with the object in order to occur. This was readily observed when a cart was pushed uphill or an object lifted, but presented problems in explaining many other types of motion. For instance, when a rock is thrown upward, it leaves the thrower's hand and loses contact with the agent causing the motion. Aristotle invented various explanations to account for discrepancies in his ideas on motion. In the case of a projectile, he reasoned that air in front of the projectile, would be pushed behind it and propel it along. Aristotle also classified motion as linear, circular, or mixed. Terrestrial motion was linear and motion in the heavens was circular. In the atmosphere, between heaven and Earth, the two types could combine to describe the motion of objects.
With respect to the universe, Aristotle adopted and expanded upon Eudoxus' system. In contrast to Eudoxus and previous philosophers, Aristotle viewed the spherical motion as corresponding to physical reality and not merely a geometrical representation. Accordingly, Aristotle proposed Eudoxian spheres as three-dimensional shells. In his system, to counteract the affect the outer shells would have on the inner shells, Aristotle proposed additional spheres rotating in the opposite direction. These counterrotating spheres negated the influence of one planet's set of shells on another. Aristotle's mechanical system increased the number of spheres needed to describe observed planetary motion to 50." (pp.8-9)
"Other natural philosophers conformed to Aristotelian physics and proposed models for the universe that integrated Aristotelian principles with astronomical observations. The most successful of these models was that of Ptolemy (100-170 C.E.). Claudius Ptolemy (Figure 1.2) was a Greek astronomer and geographer who lived in Alexandria, Egypt. He made extensive observations over his life. Ptolemy integrated the work of his predecessors with that of his own to construct a geometric model that accurately predicted the motion of the Sun, Moon, and planets. One of his primary sources was Hipparchus (190-120 B.C.E.). Hipparchus had made discoveries such as the precision of the equinoxes and the different motions of the Moon.
The Ptolemaic system of the universe relied on clever geometric constructions to account for the movement of the Sun, Moon, and planets. Ptolemy's planetary motion consisted of a system of epicycles, deferents, and equants as displayed in Figure 1.3. Each planet moved in a circular orbit called an epicycle. The center of the epicycle itself revolved around a deferent. The deferent was positioned between the Earth on one side and an equant on the other. The epicycle moved at a constant speed with respect to the equant. By introducing more epicycles and circles, Ptolemy was able to construct a good approximation for the movement of the planets. His planetary system contained approximately 80 different circular motions. Ptolemy's Earth-centered universe was surrounded, in order, by the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn." (p.9)
"Several individuals made significant contributions to physics during the height of the Arab Empire. Thabit ibn Quarra (826-901) did work in the area of statics, using levers, and developed concepts related to the center of mass. Al-Battani (850-929) cataloged approximately 500 stars and critiqued the astronomical system proposed by Ptolemy in the Almagest. He showed that the Sun varied in its furthest distance from the Earth; in modern terms this would mean that the Earth's elliptical orbit varied. In conjunction with this work Al-Battani also provided accurate calculations for the precession of the equinoxes. Alhazen (965-1038) wrote 92 volumes on astronomy, geometry, and optics, and he is especially remembered for his work in the latter area. His experiments in optics led him to reject many of Ptolemy's ideas on light. He refuted Ptolemy's idea that the eyes were sources of light rays and correctly determined that objects were visible because they reflected light rays. Through his experiments, he developed ideas on lenses and ray tracing. Alhazen also found that the speed of light varies as it passes through different media. Using the rarefaction of light, Alhazen estimated that the atmosphere was 15 kilometers thick. Al-Biruni (973-1048) also conducted studies on light, as well as on hydrostatics and density. Avicenna (980-1037), a Persian physician best known for his studies in medicine, contributed to physical science by classifying machines as levers, wheels, screws, and so forth. Much of Avicenna's teachings questioned the status quo and teachings of Aristotle.
By Avicenna's time, around 1000 C.E., the Arab Empire was in decline from both internal and external forces. Factions of the Islamic faith battled one another. A general intolerance of science pervaded Arab culture, and scientists were not free to publish their ideas. Christian Crusaders from the West and Mongol invaders from the East exerted pressure on the Arabic world. As Europeans recaptured Arab regions, the classical knowledge that had been preserved and advanced by the Arabs influenced European thinking. Major Arab learning centers, such as Toledo, in Spain, and Sicily contained extensive libraries as sources to rekindle European science. Bilingual Christians and Muslims fluent in Arabic and Latin reintroduced the works of the ancient Greeks to European scholars." (p.12)
"Roger Bacon (1214-1294) was an English contemporary of Albertus Magnus. Bacon was a Franciscan clergyman who taught at Oxford and conducted studies in alchemy, physics, and astronomy. He conducted major studies on gunpowder. His major work in physics was in the area of optics. Bacon did pioneering work on the magnifying ability of lenses that predated the development of spectacles in Italy at the end of the thirteenth century. Bacon's major contribution to scientific thought was his development of modern scientific methods to guide the discovery of knowledge.
Bacon purchased, modified, and built instruments and used assistants in conducting his experiments. In his Opus Majus (Major Work), Opus Minus (Minor Work) and Opus Tertium Bacon argued that the study of the natural world should be based on observation, measurement, and experimentation. Bacon proposed that the university curriculum should be revised to include mathematics, language, alchemy, and experimental science. Because of his teachings, Bacon often had difficulties with his superiors and spent nearly 15 years of his life in confinement. Although today we accept many of Bacon's ideas as the foundation of modern science, his methods were revolutionary in the thirteenth century." (p.13)
"Another primary figure of the Middle Ages was William of Ockham (1284-1347). William of Ockham, like Bacon, believed knowledge could be gathered through the senses, apart from scriptural teaching, and was persecuted by the Church for these beliefs. In physics, William of Ockham resurrected the impetus theory first proposed by John Philoponus (490-570) in the sixth century. According to Philoponus, the motions of heavenly bodies were due to an initial force, or impetus, supplied by God rather than constant pushing by angelic spirits, as proposed by Plato and Aristotle.
The initial impetus imparted to an astronomical body caused its motion to continue because the vacuum present in space did not retard this motion. Aristotle believed a vacuum could not exist because if it did he would be at a loss to explain how projectiles moved through the air, as discussed previously. William of Ockham revived the impetus theory, and several other Middle Ages philosophers advanced this theory of motion, including Jean Buridan (1300—1358), Nicholas Oresme (1323-1382), and Nicholas of Cusa (1401-1464). Oresme rejected the idea of a stationary Earth. He proposed that the Earth rotated daily on its axis, and this motion was imparted by an initial impetus. He also did studies on light and introduced the idea of graphing two variables on a coordinate system. Nicholas of Cusa further advanced the idea of a mobile Earth, claiming that it rotated and moved around the Sun. He believed the heavens were made of the same materials present on Earth and that stars were other suns with their own planetary systems. The impetus theory never received universal support during the Middle Ages, and the ideas of Aristotle continued to dominate Western thought." (pp.13-14)
-Richard L. Myers, The Basics of Physics, Greenwood Press, 2006, 365 pages.
