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Paper prepared by Prof. Omar Hasan Kasule Sr. MB ChB (MUK), MPH (Harvard) DrPH (Harvard) Chairman, Institutional Review Board - KFMC
DEFINITION AND CLASSIFICATION:
• Physical sciences deal with inorganic matter and energy. Physics is the basic physical science. It studies the physical world. It specifically studies matter, energy, and their interactions.
• Physics seeks to arrive at simple principles that explain complex phenomena of matter, motion, and energy at the microscopic, macroscopic, and cosmic levels. These fundamental principles are sunan al Ilaah fi al kawn.
• Physics is very precise and concise in stating these laws using mathematical language.
• Classical physics can explain macroscopic events moving slowly relative to the speed of light. Modern quantum and relativity physics have modified those laws for movements of objects at high speeds relative to the speed of light.
HISTORICAL DEVELOPMENT - 1:
• Physics as a discipline was founded in the mid-19th century but its constituent sub-disciplines had been known for a long time. These constituents were mechanics, optics, acoustics, electricity, magnetism, and material science. By the 19th century, Newtonian mechanics was coming under criticism because it could not explain some phenomena.
• Greeks developed the earliest theories about physics as they attempted to reconcile the diversity of observed phenomena and the underlying unity of matter. Greek atomists taught
that nature consisted of discrete indivisible atoms and that all phenomena were due to the motion and clustering of the atoms. The Stoics argued that space and matter were a continuity.
• Aristotle developed several ideas on a motion that impeded scientific development for centuries. Aristotle argued that force s caused-motion. A moving body required a force to act on it directly and continuously. On earth, heavy bodies moved down while lig ht bodies moved up. In the extraterrestrial realm, a motion was circular and celestial bodies followed a circular path unaffected by external bodies or agents. Massive earthly bodies had a tendency to move to the center of the earth.
• Archimedes applied mathematics to the solution of problems motion of levers and flotation of bodies on water (hydrostatics).
HISTORICAL DEVELOPMENT - 2:
• Greek science reached its climax in the 2nd century AD. There was a decline in science after that caused by many reasons: disinterest of the Romans in theoretical issues and the anti-scientific stance of the Christian Church. Muslims took the helm of scientific progress by translating and absorbing Greek sciences and then adding their own observations and theories. It was this scientific knowledge that led to the European renaissance when it reached Europe through Andalusia and Sicily.
• Aristotelian mechanics dominated medieval Europe. Aristotle had asserted that motion required the continuous action of a force. This was found inadequate to explain the continuing motion of a projectile after losing contact with the initial force. Ibn Sina and Abu al Barakat al Baghdad were among scientists who tried to rescue the Aristotelian theory by proposing that an incorporeal force was imparted to the projectile allowing it to continue in motion after losing contact with the initiating force. The medieval Church started condemning Aristotelian scientific assumptions that did not conform to theological teachings.
HISTORICAL DEVELOPMENT - 3:
• With the start of the European renaissance and reformation, science was separated from philosophy and technology. New ideas developed that replaced the Greek view of the world that has extended over 2 millennia. The new view of nature included quantitative instead of qualitative descriptions, view of nature as a machine and not a living organism, using experimentation to develop and test theories, emphasis on ‘how’ and not the ‘why’ of physical phenomena. The Christian Church that has opposed scientific growth before started being marginalized with the growing secular and humanist spirit of the period.
• Galileo Galilei (1564-1647) was among the first Europeans to challenge the ancient ideas. He questioned the idea that the earth was the center of the universe. He also discovered the laws of falling objects by showing that heavy and light objects fell to earth at the same speed. Galileo Galilei mathematized physical descriptions. He derived the law of free fall (distance is proportional to the square of time). He derived the parabolic path for a projectile. He also developed the principle of inertia.
HISTORICAL DEVELOPMENT - 4:
• Kepler developed laws describing the motion of planets. These laws were reduced to axioms by Newton the father of classical mechanics. The three laws of Kepler were: (a) orbits of planets are ellipses (b) As the planet moves through its orbit the line joining it to the sun would sweep out equal areas in equal times (c) The period of a planet’s orbit depends on its distance from the sun.
• Rene Descartes was inclined to theory and developed mechanical philosophy which explained all phenomena of nature in terms of matter and motion. Descartes postulated ether as the substance that transferred a force between 2 bodies that are not in contact. Christiaan Huygens, a disciple of Descartes, developed laws about the conservation of momentum and elastic kinetic energy.
HISTORICAL DEVELOPMENT - 5:
• Sir Isaac Newton was the culmination of the 17th-century scientific revolution. In his 1687 Mathematical Principles of Natural Philosophy, developed three laws that explained motion and mathematized physics.
• The first law states that a body stays at rest or in uniform motion unless acted on by a force.
• The second law states that the change in motion is proportional to the magnitude of the force.
• The third law states that to every action there is an equal and opposite reaction.
• Newton postulated the force of gravity to extend his laws to planetary motion. European scientists thenceforward changed from Cartesian to Newtonian physics. Newtonian mechanics were used to explaining most of the observed phenomena about the motion of celestial bodies. These methods were so effective that planets not yet observed were predicted from their effect on the movement of known planets.
HISTORICAL DEVELOPMENT - 6:
• Michael Faraday discovered induction. Faraday and Maxwell described local action. Heinrich Hertz discovered electromagnetic waves.
• By the 19th century, the law of conservation of energy was recognized as a general law of nature. The concept of entropy was formulated. Max Planck introduced the concept of quantum. Einstein extended the quantum theory to light. Then quantum or wave mechanics developed and was later extended to quantum electrodynamics. Einstein’s theory of relativity was revolutionary in physics by providing exact formulations that were only approximations under Newtonian mechanics.
• The discovery of radioactivity in 1896 opened up new areas of investigation. The description of alpha radiation (helium +), beta radiation (electrons), and gamma radiation (electromagnetic waves) suggested transmutation of elements from one another by loss or gain of sub-atomic particles. It was discovered the nuclear fission or fusion released a lot of energy and this information was used to produce atomic energy for commercial and military uses.
HISTORICAL DEVELOPMENT - 7:
• In 1905 Albert Einstein published the special theory of relativity, the quantum theory of radiation.
• The theory of special relativity asserted that laws of nature are the same for observers in an inertial frame of reference. It also asserted that the speed of light was constant for all observers regardless of their frame of reference. There is no absolute space or time all are relative. An observer in one frame will observe space and time in another frame differently. He also inferred that mass would increase with an increase in speed. Mas and energy are interconvertible and are related by the formula energy= mass multiplied by the square of the speed of light. Albert Einstein said ‘no number of experiments can prove me right; a single experiment can prove me wrong’.
HISTORICAL DEVELOPMENT - 8:
• The quantum theory of radiation asserted that electromagnetic waves were emitted as discrete energy quanta. Max Planck is also credited with the discovery of the quantal nature of radiation. Eventually, the dual wave-particle nature of radiation was accepted. Quan tum mechanics was thus born as a discipline as was applied to explain the properties of atoms and molecules.
• Heisenberg proposed a principle that it was not possible to determine the position and the velocity of an electron at the same time. These findings gave rise to philosophical discussions.
• Niels Bohr argued that reality was from measurement while Einstein argued that the physical world has properties whether measured or not.
HISTORICAL DEVELOPMENT - 9
• Optics started in Greece. Euclid stated the law of reflection and ot her Greek optic observations.
• Ibn Hazim solved many optical problems and his writings were influential in Europe. Kepler traced rays of light from the object to the image and developed a geometric theory of lenses.
• Descartes used his theory of mechanical philosophy to explain optical phenomena in terms of matter and motion.
• Isaac Newton developed the theory of colors and demonstrated that white light was a mixture of different colors. Newton regarded light as particulate. Huygens viewed light as pulsatile and developed the concept of a wavefront. Thomas Young used the wave theory of light to explain optical phenomena like interference.
HISTORICAL DEVELOPMENT - 10
• Investigations of electricity and magnetism proceeded apace in the 18th century. Newton’s inverse square law was found to hold for electricity and magnetism.
• In the 19th century, it was discovered that electric currents were accompanied by magnetic fields and this gave rise to electromagnetic sm. Later electromagnetic induction was used to produce electric currents using magnetic fields.
• The electromagnetic theory that developed later led to the understanding that light is an electromagnetic wave and that the electromagnetic spectrum extended beyond the range of visible light.
PRINCIPLES, BASIC PARADIGMS - 1
• Science is basically the description of regular predictable phenomena in nature and their causes with the purpose of manipulating or benefitting from them. Because senses are used in understanding the phenomena and senses are inherently limited, science has limitations. Early humans were keen observers of nature. Observations of movements of planetary bodies gave rise to astrology that became astronomy. Mathematics developed alongside astronomy as a way of quantifying observations.
• Science is an organized way of using evidence to learn about the natural world. Evidence-based observation can be quantitative or qualitative. The goals of science are: to investigate and understand nature, to explain events in nature, and to use explanations to make useful predictions.
• Scientists are interested in knowing what happens and how it happens but not why it happens. A scientist should be curious, honest, open-minded, skeptical, and humble (knows that science has limitations).
PRINCIPLES, BASIC PARADIGMS - 2
• The scientific method involves stating a problem, forming hypotheses, carrying out a controlled experiment, recording and analyzing results, and drawing conclusions. A theory is a well-tested explanation that unifies a broad range of observations. Theories change with new knowledge or new understanding.
• The purpose of physical science is to derive a few simple laws that can describe complex natural phenomena.
• Philosophy of physics: philosophy of nature includes considerations of metaphysics and the world view (weltanschauung). Physics deals with inorganic objects and processes that are measured and are described mathematically. Chemistry can be considered as part of physics because the forces that bind atoms and molecules together can be described physically.
PRINCIPLES, BASIC PARADIGMS - 3
• Physics describes complex phenomena starting with a few empirical axioms. Physics asserts that there is a natural order in the physical world whose basic constituents are: symmetry, fields, matter, and action.
• There are 2 modalities in physics: quantum and relativistic. The two can be combined in electrodynamics.
• There are many philosophical problems in physics that are not yet solved. Physics is also being used to solve cosmological problems such as the beginning of the universe and its ultimate fate.
• Physics started as natural philosophy. It continues to have an impact on philosophy. Newtonian mechanics is based on determinism (the assertion that the universe is based on strict causality and that the future can be predicted accurately from the present. The philosophical concepts of materialism, naturalism, and empiricism have used determinism in physics as a model. Logical positivism stake the extreme position that anything not formulated in the language of physical observation is not to be accepted. The uncertainty principle has led to a reexamination of determinism.
PRINCIPLES, BASIC PARADIGMS - 4
• Modern physical science is basically quantitative being based on measurement. Physics depends on measurements. The measurement uses numbers to describe physical phenomena. The fundamental units of measurement are time, length, and mass. All measurements are subject to uncertainty. We have to make a distinction between accuracy (the extent to which a measured value agrees with the standard value) and precision (the degree of exactness). Measurem ents may be made by unaided human senses or may be made using measuring instruments. Measurements with instruments are extensions of observations by human sensory organs. Since human sensory organs are limited, measurements are also limited.
• Measurement is the process of associating numbers with physical observations. Measurements can be carried out by the naked eye or by the use of instruments. Ancient measurements were confined to weight, volume, distance, area, and time. The growth of science has added thousands of measurements of electric currents, temperature, light, etc. Sometimes the measured item is not directly accessible and a proxy will have to be used. The signal measured may have to be amplified to enable better detection.
PRINCIPLES, BASIC PARADIGMS - 5
• The process of measuring can have an impact on what is measured thus introducing an inherent measurement error. Measurement s involve comparison with a standard. External factors that affect a measurement include noise, interference. A measurement theory must explain the error. The theory of error enables quantitative determination of the margin of error. Errors cannot be eliminated from any measurement it is, therefore, necessary that any stated measure be accompanied by a statement of the margin of error. Errors can be classified as instrument errors, observer errors, sampling errors. The errors may be random or systematic.
PRINCIPLES, BASIC PARADIGMS - 6
• Energy: Energy is the ability to do work. It exists in various forms. The re is interchange among various forms of energy. These include kinetic, gravitational, mechanical, elastic, thermal, electrical, chemical, radiant, nuclear, etc.
• Energy can be transformed into work or into another form of energy. Humans first learned how to transform chemical energy into heat energy when they discovered the use of fire. Watermills. Tidal mills and windmills were used to transform kinetic energy into mechanical energy. The steam engine converted heat energy into mechanical energy to run pumps, trains, and machines.
• The internal combustion engine transforms chemicals into mechanical energy. Turbines and rockets are also forms of energy conversion. Electromagnetic induction is a way of turning mechanical energy into electrical energy.
• In recent years direct energy-converting systems have been developed: the electric battery, the fuel cell, and the solar cell. These convert energies without an intermediate stage. The electric battery and the fuel cell convert chemical energy into electricity. The solar cell converts radiant energy from the sun into electricity. Nuclear fission and nuclear fusion produce thermal energy. Thermoelectric generators and thermionic power converters transform heat energy directly into electricity.
PRINCIPLES, BASIC PARADIGMS - 7
• Symmetry: the right to left symmetry
• Entropy and disorder: entropy is a measure of the disorderly state of matter. The entropy of a system always increases and never decreases. When a system is not in thermal equilibrium part of it may increase in entropy while other parts do not.
• Chaos: Power is the rate of doing work.
• Forces: There are 4 types of forces in decreasing order of strength: the strong nuclear force, the weak nuclear force, electromagnetic force, and gravitational force. These forces are thought to be outward manifestations of the same underlying force and physicists are working on developing a unified theory for them. All 4 forces exhibit the phenomenon of symmetry (physical laws are the same in different regions of space and time) can be described as fields.
PRINCIPLES, BASIC PARADIGMS - 8
• Gravity: Gravity is a universal force by which bodies attract one another. It has no effect on the internal properties of an atom. It is considered the weakest force in nature but it is important because it determines the motion of celestial bodies.
• Gravity was first described by Isaac Newton in 1687. His description is still valid for most ordinary bodies and motion. He used his theory of gravity to explain the movement of celestial bodies, the falling of objects, sea tides, and many other phenomena.
• Newton developed the law of gravitation which states that and 2 bodies or particles in the universe attract one another by a force acting through a straight line between them. The force is directly proportional to the product of the masses and inversely proportional to the square of the distance between them.
• The General Theory of Relativity has made modifications to the Newtonian gravitational law.
• In the 20th century, Einstein made modifications to the theory of gravity in his theory of relativity which finds applications at high speeds. The challenge of modern physics is to find a relationship between gravity and other forces.
PRINCIPLES, BASIC PARADIGMS: ELECTROMAGNETISM
• In the 18th century Charles Coulomb showed that electrostatic forces between charged bodies followed the same law as Newton’s law of gravity. He also showed that the force between 2 magnetized bodies followed the same law. Electricity and magnetism are not separate entities but are a manifestation of the underlying electromagnetism that has a dual wave and quantum character.
• Magnetism is associated with the movement of electric charges and with the movement of electrons orbiting within atoms. No specific magnetic charge comparable to an electric charge has been identified. All matter exhibits magnetism of varying intensities when in a magnetic field; iron exhibits the strongest magnetism because of its internal alignment. A magnetic field exerts a force on charged particles. There is an attraction between opposite dipoles and attraction-repulsion between similar dipoles. Magnetism is associated with a magnetic field that has an impact on the matter. The commonest source of magnetic fields is an electric current through a loop.
PRINCIPLES, BASIC PARADIGMS: MOTION
• Motion: Complex motions can be reduced to several components simple motions. Kinematics is a description of how objects move. Dynamics is an explanation of why objects move the way they move. Newton’s 3 laws of motion illustrate the primary purpose of the science of reducing the complex to the simple and also are sunan al Ilaah fi al kawn. Motion is due to forces (push or pull). There are basically 3 types of forces: gravitational, electromagnetic, and nuclear.
PRINCIPLES, BASIC PARADIGMS: CONSERVATION - 1
• The law of conservation applies to physical properties that do not change with time within a closed system. The changes seen are temporary and after adjustments, the status quo returns. The following properties are conserved during physical changes: mass, energy, momentum (linear and angular), and the total amount of the electric charge.
• There are some properties of sub-atomic particles that are also subject to the law of conservation. The benefit of the conservation law is that it enables us to predict what will happen to a closed system after temporary changes. Conservation laws are valid for classical, relativistic, and quantum physics. Conservation laws reflect a basic law of nature which is symmetry.
PRINCIPLES, BASIC PARADIGMS: CONSERVATION - 2
• Conservation of energy: The total energy of interacting bodies or particles in a closed system remains constant. This means simply that energy cannot be created or destroyed. It can only change from one form to another. The various forms of energy encountered are kinetic energy, potential energy, thermal energy, chemical energy, magnetic/electrical energy. The principle of conservation of energy is the first law of thermodynamics.
• Conservation of mass
• Conservation of mass-energy: after the discovery of relativity the principles of conservation of energy and conservation of mass were combined into one principle of conservation of mass-energy. This is because of the interchange between mass and energy.
PRINCIPLES, BASIC PARADIGMS: UNCERTAINTY
• The Uncertainty Principle also called the indeterminacy principle states that the position and velocity of an object cannot be measured exactly at the same time. The implications of this principle are difficult to see when dealing with large objects. The implications are easy to see when dealing with sub-atomic particles.
PRINCIPLES, BASIC PARADIGMS: MECHANICS
Mechanics: Mechanics is the study of the motion of objects when subjected to forces. Classical mechanics, also called kinematics, is founded on the three laws of motion by Isaac Newton. Newton’s laws are deterministic in nature. Mechanics can be divided into three sub-disciplines: statistics studies forces acting on a body at rest. K kinematics describes the motion of a body. Kinetics predicts motion. The central concepts in classical mechanics are mass, force, and motion. Mass and force are difficult to define since they are known through their effects. Mass is the tendency of a body to resist motion. Force accelerates a body. Other concepts related to mechanics are energy, momentum (linear and angular). Energy and momentum are conserved.
RESEARCH METHODS
• Research and development (R&D) is the basis of technological innovation of new products. Basic research aims at understanding nature. Applied research is using results of basic research to produce useable technology.
• Physics depends on measurement and mathematical reasoning. Arguments by analogy and symmetry are also used. Theories keep on being changed and refined. Many new discoveries are made purely by accident. Models are constructed to facilitate reasoning
• The basic measurements are mass (weight), distance, volume, and area. Ancient civilizations had standardized measures. Today the International System has become accepted as the basis for scientific measurements. Length is measured in meters. Mas s is measured in kilograms. Time is measured in seconds. Electric current is measured in amperes. Temperature is measured in kelvins. The amount of substance is measured in moles. Light intensity is measured in candelas.
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