Physics in the Past Essay Example for Free

Physics in the Past Essay One hundred years ago, in a poky apartment in Bern, Switzerland, Albert Einstein, then just a 26-year-old patent office clerk still working part-time towards his PhD, published five ground breaking scientific papers. Each of these papers, written during Einsteins annus mirabilis , has become a classic in the history of science: On a Heuristic Viewpoint Concerning the Production and Transformation of Light , which discusses optical photons and photoelectric effects. Molecular and New Measurement , which deduces the mathematical equation for calculating the speed of the diffusion of molecules. On the Motion of Small Particles Suspended in Stationary Liquids Required by the Molecular-Kinetic Theory of Heat , which provides proof for the existence of atoms. Does the Inertia of a Body Depend upon its Internal Energy, which proposes the idea for two-way transformation between mass and energy according to the special theory of relativity. On the Electrodynamics of Moving Bodies , which proposes a new theory on the relationship between time and space. This paper served as the foundation for the theory of relativity. The contemporary physics revolution, based on the theory of relativity and quantum theory, has led science into a new era. Starting from this, human exploration has extended to the boundless universe, to the distant origin of the cosmos and to the microscopic structure of objects previously unknown to mankind. Contemporary physics revolution has also spurred revolution in life sciences and geosciences in the last years. All these have changed mankinds outlook on matter, time, space, life and the universe. Moreover, this contemporary physics revolution has also given birth to technological physics including nuclear energy, semiconductors, laser, new materials such as with superconductivity, and fostered rapid development of a wide range of new technologies that have changed the methods of our industrial production and our ways of life while bringing the world to the new knowledge economics era. Founders of contemporary physics, Einstein the most outstanding among them, are undoubtedly epoch figures in the history of science and the history of mankind. It is therefore both of significance and importance for us to commemorate them in our reflections on the development of physics in the last one hundred years not just to express our gratitude but to draw inspiration from their achievements and build on their legacy to create a better future for all humankind. 1. The inconsistency between experiments and theories gave birth to new science concepts At the end of the 19 th century, people were still intoxicated with the interpretations given by classical physics. Some even held that there was not much more to do in physics. It was under such a state that the discovery of some physical phenomena revealed the limitations of interpretations given by classical physics. High-temperature measurement technology, called for by the rapid development of the metallurgical industry, led to research in thermal radiation. In the mid 19 th century, Germany emerged as the birthplace for research in this field. Thermal radiation refers to the electromagnetic waves emitted by matter when heated and largely depends on the temperature of the matter itself. Maxwells electromagnetic field theory regards light as an electromagnetic phenomenon. Although this explains the propagation of light, it does not explain the emission and reception of thermal radiation. G. R. Kirchhoff (1824—1887) advanced to use black body as an ideal body for research on thermal radiation (1859). W. Wien (1864-1928) confirmed that it is possible to regard the thermal radiation performance of a pored cavity as a black body (1896). A series of experiments demonstrated that the density of the energy emitted by such black body is related to its temperature and not to its shape or materials. Theoretical explanation of the energy spectrum curve of a black body became an essential issue in research on thermal radiation at the time. Based on the general principle of thermal mechanics and some special assumptions, Wien developed a formula to determine the energy density associated with particular wavelengths for any given temperature of a radiating black body (1896). Max Plank joined research on heat radiation during the same period. To explain the energy distribution curve of the radiated light spectrum of a black body, Plank developed a formula. It was not until 1900 that scientists proved the veracity of the formula through experimentation. Plancks formula requires that the energy emitted or absorbed by black body is the energy quanta that determine its amount. This implies that energy, like a matter, has the properties of particles, i. e. , energy also has separability and discreteness. In 1905, Einstein extended the concept of quanta to the propagation of light and proposed the light quantum theory, successfully using it to explain photoelectric effect. In 1913, the Danish physicist N.  Bohr (1885 – 1962) extended the concept of quanta to atoms, and established a quantum structural model for atoms based on the discreteness hypothesis of the energy state of atoms. Dissatisfied with the lack of self- sufficiency of Bohrs atom theory, the German physicist Werner Karl Heisenberg (1901—1976) developed matrix mechanics in 1925 by starting directly from a priori data on the frequency and intensity of spectrum of visible light. The following year, the Austrian physicist E. Schr? dinger (1892—1961) improved the wave-particle duality matter wave theory of L. V. de Broglie (1892—1994), leading to wave mechanics. Subsequent research proved the mathematical equivalence of both matrix mechanics and wave mechanics. The American physicist R. P. Feynman (1918 – 1988) later developed the third equivalent path integral quantum mechanics. It is until this period of time that quantum theory was established to its robust architecture. The thermal radiation hypothesis became the logical starting point for the birth of quantum theory. The quantum of energy concept was developed in 1900. As a result of its development and extended application, quantum mechanics, which describes the motion of subatomic particles, took form in the 1920s. The combination of quantum mechanics with the special theory of relativity gave birth to quantum field theory, which describes the generation and annihilation of subatomic particles. Development of quantum field theory has experienced three stages: classical quantum field theory (symmetrical), standard quantum field theory (non-symmetrical) and super-symmetrical quantum field theory. It has not only revealed the secrets of the subatomic world invisible to the naked eye, but deepened our understanding of the evolution of the universe and revolutionized the way people perceive the world. Quantum field theory, moreover, has set the stage for a series of key technological breakthroughs. It has been demonstrated from the experimental research on a black body radiation to the advancement of the quantum theory that science is, after all, still a positivistic knowledge system. That is, as long as a theory is not consistent with rigorous experimental results, a scientist has all the reasons to doubt the theory itself no matter how authoritative the theory it may be, no matter how many people have upheld it, and no matter how many years it has been embraced. At the same time, we should understand that the ultimate results of scientific research should give theoretical interpretation of natural phenomena discovered while this requires not only rigorous and scientific attitude and rational challenging spirit, but also profound thinking ability and deliberate analysis ability and theoretical reasoning ability. 2. Key breakthroughs in science hinge upon distillation of scientific research questions The theory of relativity advanced by Albert Einstein (1879 – 1955) is a brand new outlook on space and time. The key scientific question for the theory of relativity lies in simultaneous relativity. The theory of relativity has given justified interpretations about the relationship between time and space, the relationship between space and distribution of matters, and the relationship between matters and energy. In the process, it transformed the knowledge system of classical physics dating back to Sir Isaac Newton(1642-1727). The theory of relativity, together with quantum theory, not only formed the foundation for development of physics in the 20 th century but also raised our understanding of the nature to an entirely new level, thus having a profound effect on the way of thinking and perceptions of the world. The founding of the theory of relativity originated from the crisis of Ether, a hypothesized carrier for electromagnetic waves. The experiment report On the Relative Motion between the Earth and Light Ether published by the American physicist A. A. Michelson (1852—1931), revealed that the theory of relativity, which is universally correct in the reference to Newtonian mechanics, is incorrect in Maxwells electromagnetic field theory. Both the Dutch physicist H. A. Lorentz (1853—1928) and the French physicist J. H. Poincare (1854—1912) attempted to solve this contradiction by maintaining the Ether hypothesis. Lorentz proved that the earth system and Ether follow the same law at the first-order approximation by incorporating â€Å"length contraction† (1892), â€Å"regional time† (1895) and a new conversion relationship (1904) while the relativity principle developed by Poincare and the conversion group (1905) developed by Lorentz emphasized the universal validity of the relativity principle. Although both deviated from the framework of classical physics lay at the doorstep to the theory of relativity,but it was left to Albert Einstein to turn the key and push the door open. Einstein believed that the electromagnetic field had an independent physical existence and held the Ether hypothesis to be superfluous. His most important contribution may reside inside in the fact that he raised the critical scientific problem of â€Å"simultaneous relativity†. In On the Electrodynamics of Moving Bodies (1905), Einstein claimed that two events happening simultaneously in the same location do not depend on the observations of the observers; yet two events happening simultaneously at two different locations do depend on their observations. It would be meaningful only if it is indicated clearly that the events are relative to which observer. We could hardly observe such relativity of simultaneity in our daily lives because this can be discovered only when the speed of an observer is close to the speed of light. Starting from the simultaneity of relativity concept, Einstein deducted the main conclusions for the theory of special relativity through two principles: constancy of the speed of light and relativity. The general theory of relativity (1915) and the unified field theory are further developments of the theory of special relativity. Through his trilogy research on the theory of relativity, Einstein revealed to his physics colleagues his extraordinary creativity in scientific thinking. 3. Scientific imagination requires the support of rigorous experimental evidence In the year following the publication of his general theory, Einstein publishedObservations Made on Cosmology Based on the General Theory of Relativity (1917), which marked the birth of modern cosmology. Although Einsteins cosmological model followed the static Newtonian view on the universe, its field theory lays the groundwork for the existence of dynamic solutions to cosmology. The Dutch astronomer W. de Sitter (1878-1933), the Russian mathematician A. Friedmann(1888-1925) and the Belgian physicist G. Lemaitre(1894—1966) published the expanding universe theory in 1917, 1922 and 1927, respectively. The ‘red shift effect observed by the American astronomer Edwin Hubble (1889-1953) offered strong support for the expanding universe theory. Drawing on the expanding universe theory, the Russian American physicist G. Gamov (1904—1968), formulated the idea of a hot explosion of matter and energy at the time of the origin of the universe by incorporating knowledge in nuclear physics. His student R. A. Alpher(1921-) and others further derived in 1948, that the big bang explosion took place about 15 billion to 20 billion years ago and hypothesized that remains from the big bang explosion may still be circulating in the universe, presenting 5K cosmological background radiation. In 1964, two American radio engineers, A.A. Penzias (1933-) and R. W. Wilson (1936-), discovered evenly distributed isotropic cosmic microwave background radiation while tracing the source of radio noise that was interfering with the development of a communications program involving satellites. This microwave radiation is coincidentally equivalent to 3. 5K blackbody radiation. This discovery is regarded as a confirmation of the cosmic background radiation as a result of the big bang explosion. The latter years witnessed the rise of the big bang theory, which developed as the â€Å"standard model† for cosmology. In the early of 20 th century, Einstein listed the origin of a geomagnetic field as one of the five major challenges in physics. However, not until the 1960s, after the seismic wave method confirmed the layered structure of the earth, did scientists devise the â€Å"self-exciting dynamo† hypothesis, the full scientific endorsement of which awaited evidence from differential core-mantle movement obtained in 1995. Increased knowledge on the inner structure of the solid earth mainly relies on the seismic wave method. The concept of layered structure of the earth has gradually formed through analysis of variation of the seismic wave passing through the inner structure of the earth. The Croatian geophysicist, A. Mohorovi? ie (1857—1936), discovered the interface between the earths crust and mantle (1909); The German-American seismologist, B. Gutenberg (1889—1960), discovered the interface between the earths mantle and the core (1914); and the Dutch seismologist I. Lehmann discovered the interface between the earths liquid outer and solid inner core (1914). The New Zealander physicist K. E. Bullen proposed the layered model of the earth (1940). The differential core-mantle revolving movement, a hypothesis designed to explain the origin of the geomagnetic field, was later used as a mechanism to explain the inversion of the polarity of geomagnetism. However, no direct scientific evidence had been found. Based on their analysis of recorded data for 38 earthquakes, which took place between 1967 to 1995 near the Sandwich Islands close to the South Pole in South America, Dawn (Xiaodong) Song and Paul G.  Richards, Columbia University, in US, measured the speed of seismic wave transmitted from the earths inner core to a seismographic station in Alaska near the North Pole. They found that the time it took seismic wave to travel from the South Pole to the North Pole had been reduced by 0. 3 seconds over the previous years. This confirms that the earths inner core is revolving slightly faster than its crust and the mantle—indeed the earths inner core will turn one extra circle in about 300 to 400 years. Dr.  Su Weijia, another Chinese scholar residing in the US, and Dziewonski, an American seismologist, reached a similar conclusion based on analyses of seismic data from about 2000 seismographic stations around the globe. Based on their computation, the revolving speed of the earths inner core is even faster, 20 – 30 degrees just over the timeframe 1969 to 1973. It can be seen from the propositions and improvement of the theory of relativity by Einstein, the big bang theory and the geomagnetic theory that while it is important to solve problems in development of science, it seems even more important to raise key questions in science. Raising questions is the prelude to scientific research. More importantly, raising key questions reveals the creativity associated with science. Sometimes a key question in science leads to new fields and new research directions. To ask the right questions, one must have a through understanding of existing knowledge, a love for truth that transcends respect for authority, and fine observational skills and creative thinking. At the same time, one must be rational bold and confident.