Energy makes things happen in life. Energy from the Sun makes plants grow. Energy from fossil fuel runs automobiles and is responsible for most of the electric power produced. Energy from the Sun also powers nearly all communications satellites in space. Nuclear energy powers submarines and military ships.
The Sun
The Sun is the most important source of energy for our planet and the human race. The human race would starve to death without sunlight. Major food crops require sunlight to grow. Sunlight also drives weather on the Earth and causes rain clouds to form. Most of the water we drink and that required for growing our food supply is dependent on this rain. Even the oxygen we breath is provided by sunlight-dependent plants and phytoplankton (tiny, plant-like water creatures).
The Sun emits great amounts of energy. That energy comes from nuclear fusion. In nuclear fusion, lighter atoms combine to produce a more massive atom. For example, under certain circumstances, hydrogen atoms combine to form helium atoms. In the process, energy is given off according to the equation E = mc^2.
The interior of the Sun is millions of degrease, but the surface of the Sun is only about 5,000 degrees Centigrade. If the Earth was next to the Sun, the atmosphere would be blown away and the oceans evaporated. Many rocks would be melted, and the Earth could not exist.
Fortunately, the Earth is 93 million miles away from the Sun, so the energy received by the Earth from the Sun is only about 1,380 Watts per square meter (the strength of about 10 bright light bulbs).
Some energy is absorbed by the Earth's atmosphere. Water vapor in the Earth's atmosphere is a good collector of the Sun's energy. This is why you can see clouds expanding and billowing on a bright summer day. Sunlight also gets scattered by the atmosphere to produce our beautiful blue sky.
Liquid water is an reasonably good absorber of sunlight. Since 2/3 of the surface of the Earth is covered by oceans, about 2/3s of the sunlight which reaches the Earth's surface is absorbed by the oceans. On the portion of the Earth covered by land, some of the sunlight which reaches the Earth's surface is absorbed by plants and rocks. The rest gets reflected back into the atmosphere or space. Clouds also reflect quite a bit of sunlight back into space. Even though clouds absorb some sunlight, the water droplets which comprise clouds are too small to fully absorb the light which fall on them. Snow also reflects sunlight back into space.
Energy Sources
Where does energy come from? If your answer is coal, oil or sunlight, you would be partly right. The energy people use comes from many sources. Each source has an exciting story.
The story of energy must start somewhere. In fact, nearly all of our energy originally came from stars such as our Sun. Stars give us energy in two ways. The most common way is starlight, also known as sunlight. Another way stars can give us energy is when they explode. Did you know that many cities are partially powered by exploded stars? It's true! Here are some common sources of energy.
Renewable Energy Sources
Solar
Sunlight is used to grow crops and to heat some houses. Sunlight can also be used to produce electricity. When sunlight shines on certain types of silicon wafers, called photovoltaic or "solar" cells, electric current is produced. It takes quite a few solar cells to produce much electricity, so solar power is expensive. However, solar power is quite useful to power satellites, emergency highway phones, remote homes and buildings, and even portable calculators--in other words, devices which are not directly hooked up to the local power company.
Wind
Wind mills across the world use wind power to pump water and produce electricity. At one time, wind was used extensively to propel ships and is still used by many recreational water craft.
Wood
Energy literally grows on trees. Much of the world's population uses wood for heat, cooking and light. Unfortunately burning wood causes forests to be destroyed and also causes a lot of air pollution. Charcoal is frequently made from wood.
Fossil Fuels
Coal
Coal is a rock like substance produced by plants which died and decayed millions of years ago. Coal is used to generate most of the world's electricity. Coal also is used to power some ships and railroad trains. Coal used to be used extensively to heat houses.
Oil
Oil is a thick liquid found in the ground which came from decaying animals. Oil is used extensively to power automobiles trains and airplanes, but is also used for generating heat and electricity.
Natural Gas
Natural gas is often produced as a byproduct of petroleum. Natural gas is used to heat many homes, to generate electricity and to run "clean-air" vehicles.
Nuclear Energy
Fission
Nuclear electric power plants, as well as naval submarines and and ships use nuclear fission. Fission involves splitting apart heavier atoms such as uranium or plutonium into lighter ones, which releases tremendous amounts of energy. Nuclear power can be extremely cost efficient and produces very little air pollution, but can result in the release of extremely harmful radiation into the atmosphere. Nuclear decay is used to power spacecraft traveling to far planets such as Jupiter and Saturn where there is not enough sunlight for solar power.
Fusion
Fusion energy powers the stars. Fusion involves combining very light atoms such as hydrogen into heavier atoms such as helium. Fusion has been demonstrated in laboratories on Earth, but it is not yet practical for generating power for peaceful means.
Turning Energy Into Power
Energy is nearly useless unless you can turn it into power in order to perform useful work. For example, on a hot day there is plenty of energy in the air, but it would be impossible to utilize that energy to run your air conditioner.
Human history is a story of efforts to turn energy into work. Originally, the only way to turn energy into work was for people to eat energy-rich foods such as grains and do the work with their own muscles.
Eventually other ways to turn energy into power were discovered. The water flow from rivers was harnessed in water mills to grind grain and eventually drive machinery. The trick was to place a wheel-like structure into the river. The river current would push puddles or cups on this "water wheel" which would turn a grinding wheel, axle or other means attached to the machinery.
Wind power was used in much the same way. Windmills with giant propellers were built which would be rotated by the wind to drive a grinding wheel or often used to pump water.
Heat energy is easy to create. All you have to do is burn some wood or coal. Heat itself is not power, however. A steam engine is a device which can take this heat, though, and turn it into power. The first steam engine was invented in ancient times by the Greek philosopher Hero. Hero's steam engine was just a ball with a little water inside. A flame would create steam inside this ball, which would push out of little tubes and rotate the ball. It was ingenious, but not very useful. In fact the first useful steam engines were not invented until the 1700s.
In the 1800s, it was discovered how to use steam-engines to run electric power generators. It took decades for the usefulness of electric power to be fully appreciated. Indeed, electric lighting was almost unknown before the latter part of the 1800s. The electric motor was created which helped to revolutionize industry.
In the early 1900s, ways of using electricity to generate radio signals was invented. Although telegraphs and telephones were already in use, it was radio which was the true precursor of today's multimedia revolution.
Also, in the early 1900s, petroleum began to be increasingly used to power automobiles, trucks and later, trains. Petroleum power is what has made us such a mobile society.
In the mid-1900s, nuclear power became practical, and nuclear fission became used to generate electricity and run military ships and submarines. Nuclear power is also used for scientific spacecraft which travel far from the Sun.
Although solar-electric power had been known from the early 1900s, it was not really developed until it became invaluable for spacecraft. Environmental concerns about the effects of fossil and nuclear fuels have encouraged the development of solar power for use on the Earth. Other "renewable" forms of energy such as wind and geothermal have become more popular as well.
Energy & The Consumer
Each one of us is a consumer of energy. You are consuming electrical energy right now to power your computer to read this web page. Energy is very important to consumers. People use gasoline for their cars and natural gas to heat their houses.
As a consumer, you can save energy in addition to using it. Saving energy saves money and helps to preserve the environment.
Here are several simple ways to save energy:
- When you aren't in a room for more than 20 minutes, turn off the lights.
- Try not to hold open refrigerator or freezer doors for long amounts of time.
- Make sure your computer is using energy-saving features and software.
- Don't leave open outside doors foor very long when using heat or air-conditioning.
- Try to use less hot water. Take cooler baths or shorter showers.
- Get a solar-powered battery charger. Try not to waste batteries.
- Vedansh Tiwari
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