Introduction Energy is the source of all change on the planet Earth.
Earth is a complex of
active physical and biological systems which interact and influence one another and change in response to energy in its various forms.
There are various sources and forms of energy on Earth; some exert their influence naturally and others do so through human intervention. Energy cannot be destroyed but it can be (and constantly is) converted from one form to another.
1. What is the most important source of energy for Earth?
The Sun. Energy radiating from our closest star - the Sun - provides the
natural power that fuels most of the physical and biological processes important to life. These processes include the movement of Earth's atmosphere which distributes energy, produces global weather, and oceanic circulation. Sunlight energy also sustains plant and animal life. About half of the Sun's energy is absorbed or reflected back into space as it passes through our atmosphere.
2. Is the Sun our only natural source of energy ?
No. Another natural source is the
gravitational force which pulls matter toward the center of Earth. The pull is strongest on or near Earth's surface; it causes flows of air and water, and falls of earth and rock.
Another natural source of energy is geothermal energy which is heat contained beneath the Earth's crust and includes heat generated within the Earth by radioactive decay of unstable atomic isotopes.
A third natural source of energy is the energy contained in the oceans and rivers. Electrical energy can be generated from the energy released by flowing water.
3. What are the different forms of energy?
From the point of view of a physical geographer they are: solar radiant energy, heat energy, gravitational energy, kinetic energy, and chemical energy. These are the forms of energy that are most significant to natural processes on Earth's surface.
From the point of view of a physicist for whom the definition of energy is the capacity or power available for doing work (causing change) the different forms may be described as being electrical, mechanical, thermal, or nuclear.
4. What is Solar Energy?
Solar energy is radiant energy that travels from the Sun to Earth (a distance of about 150 million kilometers) and reaches Earth in about eight-and-a-half minutes at a speed of about 300,000 km per second (186,000 miles per second). Most of the solar radiant energy reaching Earth is visible light (wavelengths of energy to which the eyes of animals are sensitive). Some of the energy is longer-wavelength thermal energy that is felt as heat. Shorter-wavelength ultraviolet solar energy is what causes sunburn.
5. What is Heat Energy?
This form of energy is produced by the random motion of atoms and molecules of substances. The more vigorous the movement of its atoms and molecules, the hotter a substance becomes. The movement requires the input of energy - which can be in another form (other than heat) such as longer-wavelength solar energy.
Heat energy can be transmitted from one body/substance to another by conduction, convection, or radiation.
Heat energy can be used to perform mechanical work.
6. What is the relationship between heat energy and temperature?
Temperature is a measure of average molecular motion. Heat energy is the amount of energy in a substance. For example, a hot drink at 122 degrees Fahrenheit (50 degrees Celsius) is hotter (has a higher temperature) than a bathtub of warm water at 95 degrees Fahrenheit (35 degrees Celsius) but there is more heat energy in the warm bathtub water because of its larger volume.
7. What is Gravitational Energy?
Gravitational energy is the potential energy an object (or a substance) has because of its elevation or distance from Earth's surface. Gravitational energy is proportional to altitude and mass; a large boulder at op of a mountain will hit the ground at the foot of the mountain with more force than will a smaller boulder further down the mountainside.
8. What is Kinetic Energy?
This is the energy of motion. The higher the speed at which something is moving, the more kinetic energy it has. For a given speed, the amount of kinetic energy is proportional to the mass of an object. If equal volumes of air and water are moving at the same speed, the water will have much more kinetic energy because of its much greater mass. This is why ocean waves can do more damage than winds even when the winds have more velocity.
9. What is Chemical Energy?
This is energy stored in the electrical bonds that hold together the atoms and molecules of all substances. When substances react chemically, their energy is either released, absorbed, or converted to other forms of energy. For example, when striking a match, the chemical energy stored in the match-head is transformed into heat and light energy. In plants, radiant solar energy is used in photosynthesis and is stored in the resulting carbohydrate molecules.
10. Is Chemical Energy the Same as Atomic Energy.
No. Atomic energy is the energy released by the splitting of an atom as in a nuclear reactor. Stars, like our Sun, are natural nuclear reactors in that hydrogen is continuously converted to helium with resulting violent outputting of energy.