Home \ Online Books \ The Creation Explanation

Some Basic Principles of Physics
Important for Understanding Nature

Motion, distance, speed and velocity

Motion is measured in terms of distance, using such units as feet, inches and miles, or meters, centimeters, and kilometers. The rate of change of distance, called speed, is measured in miles per hour (miles/hour), meters per second (cm/sec), or kilometers per hour (km/hr). Velocity is speed with the direction precisely stated, for example, 10 miles/hour directly north. Acceleration is the rate of change of velocity.

Work, force, energy, and energy transformations

Work and force are familiar terms to most people, and the average person has some intuitive notion of what they mean, even though he may not know their technical definitions. Force applied to an object produces change only if permanent deformation or motion results. Some motion, however slight, always results from applied force unless it is counteracted by an equal and opposite force.

Thus, when a force is applied to a coil spring, there is motion, for the spring is compressed; or, when a lifting force is applied to a lead weight, there is motion and the weight moves upward. In each case there is resisting force: the spring resists being compressed, and the force of gravity resists the lifting force.

This leads us to the definition of work: Work is the transference of energy which occurs when a force is applied to an object, causing it either to be deformed or to move in the direction of the force. Quantitatively, work is defined as the product of force times distance. This is expressed by the formula, W = FxD (where F is the component of the force which is in the direction of the motion, and D is the distance moved.

Once the spring has been compressed and the compressing force is released, the spring can expand and do work in the process by exerting force on a moving object. The raised weight can be allowed to return to its initial lower level while doing work in a similar fashion. Thus we say that a compressed spring and a raised weight have the capacity to do work.

This leads to another important definition: Energy is the capacity to do work. Thus the compressed spring and the raised lead weight in the previous illustrations possess energy. There are a number of different kinds of energy, and most of these are classified as either potential or kinetic. Potential energy is possessed by a system of objects by virtue of their relative positions. Thus the compressed spring possesses potential energy of deformation because its parts have been moved with respect to one another. Likewise the lead weight possesses gravitational potential energy because of its position relative to the earth. A third class of energy is radiant energy, the energy carried by any kind of electromagnetic radiation, such as visible, X-rays or radio waves.

On the other hand, Kinetic energy is energy which an object possess by virtue of its motion. If the raised weight is released, it immediately starts to lose potential energy as it falls, but gains kinetic energy as its speed increases. These are two examples of energy transformation which will be discussed in more detail below.

Note that when the raised weight is left free to fall, the only force acting upon it is the force of gravity downward. The weight immediately receives an acceleration in the direction of the gravitational force acting upon it. The compressed spring in a toy gun applies force to a projectile and accelerates it. Magnetic force acting on a piece of iron can accelerate the iron, and the gas pressure in a rifle barrel produces and force on the end of a bullet which accelerates it to high velocity along the barrel.

From these examples of the effect of force, we may derive a definition for force: Force is any influence which capable of accelerating an object. From this definition we may draw the conclusion that if an object is either stationary or moving at constant velocity, the sum of all forces acting on it is zero, because it is not being accelerated. On the other hand, if the velocity of an object is changing--either increasing, decreasing, or changing direction--a non-zero net force is acting on that object, because it is being accelerated.

figure 2-1. The stationary weight at the top possesses potential energy. As it falls, its potential energy is transformed into kinetic energy.

Observe that force is an interaction between two objects which, when there is relative motion, transmits energy from one object to the other. Thus as a force compresses the spring or lifts the weight, these objects gain potential energy. And as expanding gases in a rifle barrel exert force on a bullet, they perform work on the bullet, which is accelerated and gains kinetic energy.

We have explained force and its relation to energy only qualitatively, but just this rudimentary understanding can give much insight into common processes happening all around us in the world. Now let us return to the subject of energy.

The common kinds of energy include mechanical (potential and kinetic energy of objects large enough to be seen and handled), heat, radiant, chemical, gravitational, electromagnetic, and nuclear energy.

In view of the definitions of work and energy, it should be clear that work involves the transformation of one kind of energy into another or its transmission from one object to another. Thus, when an object falls under the influence of the force of gravity, potential energy is converted into kinetic energy as the object is accelerated.

When a gun is fired, the chemical energy of the explosive is converted into the heat energy of hot, compressed gases in the barrel, which is then converted into the kinetic energy of the rapidly moving bullet. In a hydroelectric power generating system, the gravitational potential energy of the water at the top of the dam is converted into electrical energy by the turbine-generator system at the bottom of the dam. When a moving auto is stopped, the vehicle's kinetic energy is converted by friction into heat energy in the hot brake drums. And as a final example, when a man does manual labor, chemical energy stored in his body which came from the food he consumed is converted into heat and mechanical energy. As we shall see in a later section, whenever energy is transformed, none is lost; it is merely changed into new forms.

In theory, motion need not necessarily involve work. If a moving object does not exert any force upon another object in the direction of its motion, no work is being performed. The energy of the moving object remains constant. Let us consider two examples. First, imagine a skater gliding across a perfectly frictionless ice surface. Neglecting air resistance, the skater would continue in a straight line indefinitely with the same velocity and the same amount of kinetic energy, performing no work. His acceleration would be zero because the total forces acting are zero. But if there is some friction between the skates and the ice or the skater and the air, the skater does some work on the ice and the air, and the frictional forces slow him down (negative acceleration); he thus loses some kinetic energy.

For the second example, consider a timely one, that of a satellite in circular orbit around the earth far outside the atmosphere. The earth's gravitational attraction is exerted at right angles to the direction of the satellite in its orbit. Therefore, the satellite does no work, because there is no component of force along the direction of motion. Thus it continues at a constant speed in the same orbit with constant kinetic energy and constant gravitational potential energy (because it remains at a constant distance from the earth's center). Acceleration caused by the gravitational force is a continual change in direction, toward the center, not a change in speed along the circular orbit. If, however, as is the case, there is a slight amount of very thin atmosphere through which the satellite moves, friction between the satellite and the gas molecules will result in a drag force which will slow down the satellite. The satellite in turn will do work on the air molecules and lose kinetic energy.

What happens to the kinetic energy lost by the skater and the satellite? Friction transforms it into heat energy in the ice and in the atmosphere. The production of heat by friction will be considered in more detail in the next section.

Note that, except for nuclear energy, geothermal energy, and the energy of tides, all of the energy sources available to man lead finally to the sun as the ultimate energy source on earth. Present living things obtain their energy from the sun through photosynthesis as did living things in the past. But most of the fossil fuels--coal, oil and gas--are believed also originally to have received their energy stores from the sun. Finally, hydroelectric power stems from the solar energy which powers the water cycle to lift water from the oceans to the mountain tops.

Force, energy and change

Now that the basic definitions of force, work, and energy have been considered, we may begin to examine how force and energy are involved in the structures and processes which, according to the creation model were established by the Creator for the natural world, and how the physical laws which govern the actions of forces and the transformations of energy are in accord with the creation model. It will be shown that these universal physical laws discovered and enunciated by scientists support the view that living things were designed and created by an intelligent Creator, that they could not have arisen by any spontaneous process of chemical reactions or evolution. To reach an understanding of these physical laws we must first delve more deeply into the forces which help to organize atoms which form the physical objects in the universe.

All of the changes and the examples of work discussed above in this chapter are characterized by interactions (forces) exerted between units of matter and by the movement of units of matter relative to each other. There are four classes of interactions or forces between particles of matter: gravitational, electromagnetic, the nuclear strong interaction, and the nuclear weak interaction. Gravitational force is exerted mutually between every object or particle in the universe and every other object or particle. Electromagnetic force is exerted between the fundamental particles inside the nuclei of atoms, between the nuclei and the electrons of atoms, and between electric charges and electric and magnetic fields anywhere in space.

It is by means of these four kinds of interactions or forces that units or particles of matter become organized into various forms and structures. Gravitational force is long-range in action and is mainly responsible for the organization of matter into larger units such as planets, stars, the solar system, and galaxies. Electromagnetic force in general acts at shorter or intermediate ranges and is responsible for the organization of the outer electronic structure of atoms and for the organization of atoms in molecules, crystals, liquids, all solids, gases, and plasmas (ionized gases). Finally, the nuclear forces operate at exceedingly short distances in conjunction with electromagnetic force to organize the neutrons and protons inside the nuclei of atoms.

Because all of the changes which are observed taking place in the physical universe result in the reorganization of units of matter, and because mutual forces of interaction act between material particles, work must be done when the changes occur, and energy must be transferred or transformed from one form to another.

Thus, when a weight falls toward the earth, work is performed on the weight by the force of gravity, and potential energy is transformed into kinetic energy of the moving weight. When the rock strikes the earth and stops, the directed kinetic energy of the moving rock is changed mostly into heat energy (random kinetic energy of the atoms and molecules) in the rock and the soil. When ice is melted in a pan by means of a gas flame, first the molecules of natural gas are reorganized into combustion products, i.e., molecules of carbon dioxide gas and water vapor, and the chemical energy(actually electromagnetic potential energy) of natural gas and oxygen molecules is changed into the heat and radiant energy of the hot combustion products. The heat and radiant energy is transferred to the atoms of the products. The heat and radiant energy is transferred to the atoms of the metal pan which in turn transmit it to the ice. This energy serves to break the bonds holding the water molecules together in the solid ice crystals, and the water molecules are reorganized into liquid water.

How is heat transmitted from molecule to molecule when the heat is conducted through a solid substance? Since heat is essentially the random kinetic energy of trillions of molecules or atoms which make up the solid, heat is conducted by the collisions of adjacent molecules. By this means kinetic energy moves from molecule to molecule, the faster moving molecule performing work on the slower-moving molecule.

In the preceding section the production of heat by friction was alluded to in connection with the illustration of the skater and that of the satellite. How does friction produce heat? As was just mentioned, heat is essentially the kinetic energy which atoms and molecules have by virtue of their random, rapid motions and jostlings back and forth in liquids, or gases. When the skate moves over the surface of ice, the atoms on the surface of the skate blade come into contact with and collide with those on the surface of the ice, and the atoms in the ice are given more kinetic energy because they have been caused to move faster. We say that their temperature has increased.

Likewise, when the satellite or the skater collides with the molecules of air in the atmosphere, kinetic energy is imparted to the air molecules. The temperature of the air increases. Friction always results in the production of heat. We conclude, then, that friction transforms organized kinetic and other forms of energy into random kinetic energy of atoms and molecules, which is called heat.

Can electromagnetic radiation such as visible light do work on atoms or molecules? When an atom or molecule absorbs a quantum of radiation, the quantum transfers its very small amount of momentum. The atom or molecule moves slightly, but the work accomplished is quite small. However, the energy of the quantum of radiation can increase the internal energy sufficiently to break a bond and split the molecule, to raise an electron to a higher energy level, or eject an electron from the molecule. In this way electromagnetic radiation such as visible or ultraviolet light can bring about chemical change. Outstanding examples of this are photosynthesis in plants and the production of a photographic image in the film in a camera. In photosynthesis, the chlorophyll molecule of the plant absorbs the sun's radiant energy. The plant is then able to use this energy to separate the carbon from the oxygen in carbon dioxide and combine it with water to produce sugar and starch.

In the photographic process, light energy dislodges electrons in the microscopic crystals of silver bromide or silver iodide in the film emulsion. As a result, some free silver atoms are produced which then serve as a latent or invisible image, made visible by the development process. Thus photography is based upon changes which light is able to produce in chemicals in the film emulsion to bring about the reorganization of atoms in the silver bromide crystals.

For our final example of energy transformations and reorganization of matter, let us consider the use of food and oxygen by our bodies (known as metabolism). Remember that we are dependent ultimately upon plants for our food supply. Using the sun's radiant energy, plants reorganize carbon dioxide, water, and compounds of nitrogen and phosphorus, plus many other elements in trace amounts, to produce sugars, fats, proteins, vitamins, and other compounds necessary for our bodies. These substances are absorbed from the plant materials eaten by animals and by man.

Particularly the sugars, fats, and proteins contain large amounts of chemical energy which comes originally from the sun as radiant or light energy. These important organic compounds also are more complex in structure, more highly organized than the simple substances such as carbon dioxide and water which the plants started with. Furthermore, the living cells of plants and animals are capable of using them to fashion other substances which are even more highly organized. And these substances contain very high energy content, actually called free energy because it is energy which is available to do work when the complicated molecules are broken down into simpler molecules.

Thus living things--plants and animals--are capable of using the sun's energy to organize simple, low-energy substances into exceedingly complex organic molecules which contain much free energy. Moreover, plants and animals can then use these complex organic molecules to construct almost unfathomably complex living cells. And living cells compose all the vast panorama of living things with their almost endless variety of structures, functions, abilities and interrelationships.

The fundamental food supply for any community of living things is provided by the photosynthetic plants which use the radiant energy of the sun to transform low-energy carbon dioxide gas from the air plus water and other simple substances from the soil into carbohydrates (sugars, starches, and cellulose), proteins, fats, and other energy-rich organic compounds. Animals consume the energy-rich plant products and then use them to maintain their bodies in a high-energy state. When a plant stops absorbing the sun's energy, or when an animal stops consuming high-energy plant or animal products, the creature dies and its body soon decomposes into low-energy substances.

A tiny seed sprouts, begins to photosynthesize, and slowly from the elements in the air and soil builds a great, complex structure, a Sequoia tree. A microscopically small fertilized egg, just a single cell, begins to divide, absorbing energy-rich substances from its mother, and the end result is a powerful lion or a man possessed of intellect and personality.

This coupling of energy for the transformation of disorder into structured, energy-rich complexity is peculiar to living organisms. That non-living systems cannot accomplish this feat is the consistent conclusion which must be drawn from all the scientific evidence yet observed. Non-living systems appear to be characterized by processes of change which uniformly transform highly organized, energy-rich chemical structures into disordered or less organized substances of lower free energy content. This matter will be discussed in detail below where we will see that the most fundamental physical laws discovered by scientists afford powerful support for creation.

The law of Conservation energy

Scientists carefully observe and measure the things which they are investigating, accurately recording all of their observations. Then they repeat their experiments and observations, and other scientists will probably do the same, to verify that the data are reproducible. From the time several centuries ago that scientists first became interested in carefully defining and accurately measuring force, work, and energy, their experimental data have proved to be consistent with the theory that energy is always conserved. This means that in every physical process that scientists have been able to investigate quantitatively, the destruction of energy has never been observed. Energy may be transmitted from one point to another, or it may be transformed into other kinds of energy, but it is never destroyed. This principle has become established as the First Law of Thermodynamics or the Law of Conservation of Energy: In any physical system the sum of all forms of energy remains constant unless energy flows into or out of the system.

The discoveries of modern physics require a single modification of this law, since it has been found that matter can be converted quantitatively into energy and vice versa. Therefore, the conservation of energy and the conservation of matter have been combined into the Law of Conservation of Matter-Energy, which simply requires that the total of matter and energy be conserved. However, except in the case of nuclear reactions or high-energy physics, the original simple energy conservation law uniformly applies to a high degree of accuracy.