What Is A Nuclear Reaction?


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Forms of Energy: Motion, Heat, Light, Sound

What forms of energy is Raul using to move his LEGO car?

When he was a teenager in Romania, Raul Oaida became obsessed with building things: a jet-engine bike, a tiny spaceship, a LEGO car that runs on air. Why? Well, why not?

You can see more cool stories about energy at The Adaptors website.

Like video and audio? Check out The Adaptors Podcast.


Energy comes in two basic forms: potential and kinetic

Potential Energy is any type of stored energy. It can be chemical, nuclear, gravitational, or mechanical.

Kinetic Energy is found in movement. An airplane flying or a meteor plummeting each have kinetic energy. Even the tiniest things have kinetic energy, like atoms vibrating when they are hot or when they transmit sound waves. Electricity is the kinetic energy of flowing electrons between atoms.

energy_forms_pie-chartEnergy can shift between forms, but it is never destroyed or created.

A car transforms the potential energy trapped in gasoline into various types of energy that help the wheels turn and get the car to move. Most of the energy is converted to thermal energy, which is an unorganized form of energy that is difficult to convert into a useful form.

Power plants transform one form of energy into a very useful form, electricity. Coal and natural gas plants use the chemical potential energy trapped in fossil fuels. Nuclear power plants change the nuclear potential energy of uranium or plutonium into electricity too. Wind turbines change the kinetic energy of air molecules in wind into electricity. Hydroelectric power plants take advantage of the gravitational potential energy of water as it falls from the top of a dam to the bottom.

These transformations are hardly perfect. An efficient fossil fuel power plant loses more than half of the energy it creates to forms other than electricity, such as heat, light, and sound.

Forms of Potential Energy


Systems can increase gravitational energy as mass moves away from the center of Earth or other objects that are large enough to generate significant gravity (our sun, the planets and stars).

For example, the farther you lift an anvil away from the ground, the more potential energy it has. Lifting the anvil is called work, which is an interaction in which energy is transferred from one system (the person) to another (the anvil). The person has to do more work in order to carry the anvil higher, and the higher the anvil is carried, the more gravitational potential energy is stored in the anvil. If the anvil is dropped, that potential energy transforms to kinetic energy as the anvil moves faster and faster toward Earth.


Chemical energy is stored in the bonds between the atoms in compounds. This stored energy is transformed when bonds are broken or formed through chemical reactions. Like letters of the alphabet that can be rearranged to form new words with very different meanings, atoms move around during chemical reactions, and they form new compounds with vastly different personalities.

When we burn sugar (a compound made of the elements hydrogen, oxygen, and carbon) in our bodies, the elements are reorganized into water and carbon dioxide. These reactions both absorb and release energy, but the overall result is that we get energy from the sugar, and our bodies use that energy to do work.

Chemical reactions that produce net energy are exothermic. When wood is burned, the chemical reactions taking place are exothermic. Electromagnetic and thermal energy are released. Only some chemical reactions release energy. Endothermic reactions need energy to start and to continue, such as by adding heat or light.


Today’s nuclear power plants are fueled by fission. Uranium or plutonium atoms are broken apart, freeing lots of energy. Hydrogen atoms in the sun experience nuclear fusion, combining to form helium and subsequently releasing large amounts of energy in the form of electromagnetic radiation and thermal energy.

Nuclear energy is the stored potential of the nucleus of an atom. Most atoms are stable on Earth; they keep their identities as particular elements, like hydrogen, helium, iron, and carbon, as identified in the Periodic Table of Elements. The number of protons in the nucleus tells you which element it is. Nuclear reactions change the fundamental identity of elements by splitting up an atom’s nucleus or fusing together more than one nucleus. These changes are called fission and fusion, respectively.


Elastic energy can be stored mechanically in a compressed gas or liquid, a coiled spring, or a stretched elastic band. On an atomic scale, the stored energy is a temporary strain placed on the bonds between atoms, meaning there’s no permanent change to the material. These bonds absorb energy as they are stressed, and release that energy as they relax.

Forms of Kinetic Energy


A moving object has kinetic energy. A basketball passed between players shows translational energy. That kinetic energy is proportional to the ball’s mass and the square of its velocity. To throw the same ball twice as fast, a player does more work and transfers four times the energy.

rotationalIf a player shoots a basketball with backspin or topspin, the basketball will also have rotational energy as it spins. Rotational energy is proportional to how many times it spins per second, as well as the ball’s mass, and the size and shape of the ball.

In shooting a basketball, players often try to add rotational energy as backspin, because it results in the greatest slowdown in speed when the basketball hits the rim or the backboard, increasing the chance that the ball stays near the basket. The opposite direction of spin, a topspin, can be used in games like tennis, because it will help speed up a ball after impact and lowers the angle it travels after the bounce.


Thermal energy is directly related to temperature. We can’t see individual atoms vibrating, but we can feel their kinetic energies as temperature. When there’s a difference between the temperature of the environment and a system within it, thermal energy is transferred between them as heat.

tea kettleA hot cup of tea loses some of its thermal energy as heat flows from the tea to the air in the room. Over time, the tea cools to the same temperature as the room air. At the same time, the thermal energy in the room air increases due to heat transfer from the tea. However, the thermal capacitance of the room air is much larger than the tea, so the temperature of the air in the room increases by very little – so little that a person in the room wouldn’t notice it.

Heat  flows spontaneously from high temperature objects to nearby low temperature objects, until all objects reach the same temperature, called thermal equilibrium. Some materials are easier to heat up or cool down than others. The thermal capacitance, or heat capacity, of a material tells us how much energy it takes to raise that material one degree in temperature. A pound of water has greater thermal capacitance than the same amount of stainless steel, for example. In moments, an empty one pound pot on the stove heats to 212 degrees Fahrenheit (the boiling temperature of water). If you pour a pound of water into the pot, it will take much longer than the empty pot to reach the same temperature, because water needs more energy to get as hot as steel.


Sound waves are made when stuff vibrates – like strings on an instrument or gas molecules in the air. Sound waves travel when the vibrating stuff causes stuff surrounding it to also vibrate. This happens in liquid, solid, or gaseous states. Sound cannot travel in a vacuum because a vacuum has no atoms to transmit the vibration.

Solids, liquids, and gases transmit sounds as waves, but the atoms that pass along the sound don’t travel the way photons do. The sound wave travels between atoms, like people passing along a “wave” in a sports stadium. Sounds have different frequencies and wavelengths (related to pitch) and different magnitudes (related to how loud).

Even though radio waves can transmit information about sound, they are a completely different kind of energy, called electromagnetic energy.


PlantElectromagnetic energy is the same as radiation or light. This type of energy can take the form of visible light, like the light from a candle or a light bulb, or invisible waves, like radio waves, microwaves, x-rays and gamma rays. Radiation — whether it’s coming from a candle or an x-ray tube — can travel in a vacuum. Sometimes physicists describe electromagnetic radiation as being composed of particles – tiny packets of energy called photons. Each photon has a characteristic frequency, wavelength, and energy, but all photons travel at the same speed, the speed of light, or nearly 1 billion feet per second.

Electromagnetic energy can be converted to the chemical energy stored in plants through photosynthesis, the process by which plants and algae use the sun’s radiation to turn carbon dioxide gas into sugar and carbohydrates.


Electric energy is to the kinetic energy of moving electrons, the negatively-charged particles in atoms. For more information about electricity, see Basics of Electricity.


-Anrica Deb


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The Global Energy Mix and Policies

 On this page, you can find energy information about the world’s most populated countries: China, India, the United States, Indonesia, Brazil, Pakistan, Bangladesh, Nigeria, Russia, and Japan. For fossil fuel information about any country, see online tables here.

A nation’s sources of energy hinge on so many factors, from what’s naturally available to geography, political history, and relative wealth.

Even though energy demand is increasing rapidly across the globe, the International Energy Agency estimates a fifth of the world population lacks access to electricity, and a whopping 40 percent of people still use traditional biomass – like wood chips – for cooking. People who live without the energy infrastructure of electricity depend on portable petroleum fuels, manure and methane gas produced from manure, wood, grass, and agricultural wastes. Because these sources of energy are informal, it’s difficult to track and include them in statistics.

World electricity and energy demands are escalating. Countries are expanding energy investment to non-fossil sources like biofuels, wind, solar, and geothermal. At the same time, they are competing to secure access to coal, natural gas, and petroleum both at home and abroad.


Nowhere has rapid energy growth been more conspicuous than in the world’s most populated country, China. While most countries saw moderate energy growth in the same period, this Asian nation doubled energy use in less than a decade – see graph – and surpassed the United States in total energy use in 2009, according to International Energy Agency estimates. Until 2009, the United States lead the world in total energy consumption, though not per person consumption, for decades. For a list of the top 30 countries by total energy consumption see here.

Meanwhile, less than 42 percent of people in Africa had electricity at home in 2009. South Asians seemed better off than Africans that year, at 62 percent, but the real story is much more diverse. Nearly 100 percent of Chinese had access to electricity, while in Burma, only 13 percent had access. Worldwide almost 78 percent of people had access to electricity in 2009, according to the International Energy Agency.




CHINA (Pop. 1.3 billion)

Between 2008 and 2035, China may triple its electricity demand, adding power plant capacity equal to the current U.S. total, the International Energy Agency projects in one scenario of the 2010 World Energy Outlook.

China is the world’s most populated country and also the world’s largest energy consumer. China gets most of its energy from coal, 71 percent in 2008. China is also the world’s biggest coal producer but only third, behind the United States and Russia, in coal reserves.

In 2008, China generated another 19 percent of its energy from oil, which it imported from all over the world, more than half came collectively from Saudi Arabia, Angola, Iran, Oman, Russia, and Sudan. China used to export its oil, but by 2009 automobile investment was expanded by so much, the country became the second largest oil importer (United States is first).

China is in hot pursuit of securing as much oil as possible, as the nation’s reliance on imported oil is growing far more rapidly than its oil production. Several powerful, national oil companies provide the domestic oil, both from on and off-shore sources. Furthermore, China has purchased oil assets in the Middle East, Canada, and Latin America, and it also conducts oil-for-loan exchanges with other countries, $90 billion worth since 2009, according to the U.S. Energy Information Administration.

Only a small proportion of China’s energy comes natural gas, produced domestically and imported in liquified form, but that may change as prices lower and liquified natural gas terminals are constructed.

China is the world’s biggest user of hydroelectric power, which made up 6 percent of energy and 16 percent of electricity in 2009. The country’s Three Gorges Dam, the world’s largest hydroelectric project, is expected to begin operating in 2012. Nuclear power accounts for only 1 percent of total consumption. However, China’s government predicts it will have seven times its current nuclear capacity by 2020.

A homemade oven. West Bengal, India, 2009.

Detailed data on energy in China can be found here.







INDIA (1.2 billion)

India is the world’s largest democracy. Though India’s population is close to that of China’s, it is only the world’s fifth largest energy user, behind the United States, China, Russia, and Japan.

Like China, India’s electricity comes mostly from coal. However, India doesn’t have enough electricity for everyone, and only 65 percent of the population has access to electricity.

Instead, many Indian use fuels at home for lighting and cooking. A 2004-2005 survey by the government found more than 40 percent of rural Indians used kerosene instead of electricity for home lighting. The same survey showed that for cooking, 74 percent of Indians used firewood and wood chips, 8.6 percent used liquified petroleum gas, 9 percent used dung cakes, and 1.3 percent used kerosene.

India produces oil domestically, but like China, the rate of India’s increasing oil consumption far outstrips its production. India therefore has to import oil; in 2009 its most significant sources were Saudi Arabia, Iran, Kuwait, Iraq, the United Arab Emirates, Nigeria, Angola, and Venezuela, in descending order.

India doesn’t have the electricity capacity to serve its population but aims to add many thousands of megawatts in the near future.

Like China, India has nuclear power, with 14 nuclear plants in operation and another 10 in planning, the reactors purchased from France and Russia.


UNITED STATES (300 million)

Until China recently outpaced it, the United States was the biggest energy consumer in the world, though per capita use isn’t the highest but in the same range as several developed countries worldwide and less than the per capita use in Canada. The United States relies on petroleum, coal, and natural gas, as well as a small part nuclear, hydroelectric, and various non-fossil sources. The Unites States has significant oil, coal, and natural gas reserves, as well as the potential for significant investment in solar, off and on-shore wind, and biofuels.

The mix of fuels that provide electricity varies widely from region to region. Find a map of fuel mix by U.S. region from the Edison Electric Insitute here.

For more U.S. information:

-Fossil fuel use in the United States, go here.
-U.S. greenhouse gas emissions and energy here.
-U.S. sources of energy, see here.


INDONESIA (250 million)

Indonesia is an archipelago of more than 17,000 islands — 6,000 are inhabited — and it is home to 76 active volcanoes and a significant undeveloped geothermal capacity, estimated at 28 gigawatts, about as much total electricity capacity as Indonesia had in 2008.

Indonesia’s energy demand is growing rapidly, split between coal, natural gas, and petroleum sources. Traditional sources of energy like wood and agricultural waste continue to be used, particularly in rural areas and remote islands, and the International Energy Administration estimates these fuels provide about a quarter of the country’s energy.

Indonesia exports coal and natural gas. In the past, the country also exported more oil than it used, but as of 2004 that balance changed. By 2009, the country suspended its membership in the Organization of Petroleum Exporting Countries (OPEC) because it was using so much of its own oil.


BRAZIL (200 million)

Tropical Brazil is the largest country in South America both in area and population, and it is the third largest user of energy in the Americas, after the United States and Canada.

Made from sugar cane, Brazil’s ethanol production is the world’s second largest, after the United States, which makes ethanol from corn.

Brazil produces almost as much petroleum as Venezuela and produces slightly more fuel than it consumes.

While Brazil depends on oil for other energy applications like transportation, the country gets an astounding 84 percent of electricity from hydroelectric dams. Brazil also has two nuclear power plants.

PAKISTAN (190 million)

Pakistan has limited access to electricity and energy sources, and its rural population still relies on gathered fuels like wood for heating and cooking.

In 2009 around 60 percent of the population had access to electricity, far better than its neighbor Afghanistan, at just 15 percent. Nonetheless, even with access, most of the population can’t rely on electricity unless they are wealthy enough to own generators. Pakistan suffers from lengthy blackouts, even in its cities, in part because of poor transmission infrastructure and widespread electricity theft. The situation is also aggravated by lack of capacity planning, insufficient fuel, and irregularities in water supply for hydroelectric.

In 2010, angry citizens protested violently after lengthy blackouts — as long as 18 hours according to Reuters — plagued the country. That summer, Pakistan has nowhere near enough electricity for its peak needs, which were roughly 25 percent more than its total production capacity. The widespread blackouts crippled the country’s textile industry, its biggest source of exports, and some reports suggest that hundreds of factories were shuttered as a result of sporadic power.

Meanwhile, several proposals for gas pipelines through Pakistan have yet to get solidified, including one from Iran to Afghanistan (which is opposed by the United States).


BANGLADESH (160 million)

Like nearby Pakistan and India, with which it shares cultural and political histories, Bangladesh also suffers from electricity shortages. Only 41 percent of Bangladeshis had access to electricity in 2009, according to the International Energy Administration.

Most of the electricity in this delta nation is generated from natural gas, with smaller amounts each from oil, coal, and hydroelectric sources. More than 30 percent of the country’s energy comes from biomass, agricultural wastes, and other combustible, renewable materials.

In 2011, Bangladesh signed a contract with oil company ConocoPhillips, allowing off-shore drilling for natural gas, despite internal protests that insisted Bangladesh should keep more of the gas for its own. The agreement gives 20 percent to Bangladesh.


NIGERIA (160 million)

Nigeria is Africa’s most populous country, and it is world famous for its oil, most of which is exported for sale by huge foreign oil companies like Royal Dutch Shell, ExxonMobil, Chevron, ConocoPhillips, Petrobras, and Statoil. Roughly 65 percent of government revenue comes from the oil sector, and around 40 percent its oil exports are sent to the United States. Nigeria also holds the largest natural gas reserves in Africa.

Extensive oil development has wreaked havoc on Nigeria’s ecology. Oil spills have polluted Nigeria’s water, affecting both fishing and agriculture. Much of Nigeria’s natural gas is flared rather than being collected and sold for fuel. Flaring involves burning off naturally-occurring gases during petroleum drilling and refining, resulting in  environmental degradation, greenhouse gas emissions and loss of revenue.

Even though Nigeria is fossil fuel-rich, only 47 percent of the population have access to electricity, and less than a fifth of energy in that country came from petroleum and natural gas in 2007, reflecting the widespread use of more traditional fuels like wood. Nigeria only used 13 percent of petroleum it produced in 2009.


RUSSIA (140 million)

Russia has significant wealth in fossil fuels, including the largest natural gas reserves and the second largest coal reserves, after the United States. In 2009, Russia produced more oil even than Saudi Arabia, mostly from Western Siberia. In 2009, Russia exported far more oil than it used, and 81 percent of its exports went to Europe, notably the Netherlands and Germany.

Russia is also the third largest consumer of energy in the world.

The country has a well-developed pipeline system to transport oil from remote regions, a system which is almost entirely controlled by a single state-run company, Transneft.

Like Nigeria, Russia flares gas in the process of drilling and refining oil, and in 2008 Russia flared more gas than any other country in the world, 1,432 Bcf of natural gas, more than double Nigeria’s output and equivalent to the annual greenhouse gas emissions for 1.4 million passenger cars, according the calculator on the U.S. Environmental Protection Agency website and data from the U.S. Energy Information Administration.

Russia operates 31 nuclear reactors, half of which employ a similar design to the ill-fated Chernobyl plant in the Ukraine.


JAPAN (130 million)

Japan doesn’t have significant fossil fuel resources, one reason that much of its electricity industry relies on nuclear power. It is the world’s third largest user of nuclear power.

Japan is the world’s third larger oil consumer, and it does produce some oil domestically. However, it also imports a lot of oil and natural gas, the later in the form of liquified natural gas, or LNG. Almost half of its energy came from imported oil in 2009, and just 16 percent of Japanese energy came from a domestic source.

Japan also invests heavily in foreign oil, including in the United Arab Emirates, the Congo, Algeria, Russia, Australia, Papua New Guinea, Brazil, Canada, the United Kingdom, Vietnam, and Indonesia, to name a few.

As of June 2011, Japan is still recovering from a massive earthquake and tsunami that devastated its northeast coast on March 11, 2011, forcing the shutdown of several nuclear reactors as well as damaging refineries, oil and gas generators, and electricity transmission infrastructure.

Japan imports most of its oil from the Middle East: Saudi Arabia, Iran, Kuwait, the United Arab Emirates, and Qatar together supplied 77 percent of imports in 2009.

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Major sources of energy/their advantages and disadvantages

There is no easy answer to what is the best source of energy or electricity. Is the priority reliability, affordability, the economy, international human rights, limiting greenhouse gas emissions, preserving environmental resources, or human health?


It’s undeniable that today — whether we like it or not — humans worldwide are overwhelmingly dependent on fossil fuels: coal, oil, and natural gas. Everything eaten, worn, lived in, and bought is tied to availability of fossil fuels. Even if 100 percent of politicians were determined to stop using them today, society has neither the electricity grid nor the vehicular and industrial technology to sustain the current American lifestyle on non-fossil sources of energy. Yet.

When comparing sources of energy, it’s easy to forget how universal fossil fuels are. These sources continue to dominate for reasons that are difficult to measure, like political influence, advertising clout, and control over energy infrastructure. Other sources have disadvantages purely because they don’t fit in as well.

Volume brings another difficulty in comparing sources of energy. There is so much more fossil energy, and it’s been used for a long time, so we know a lot more about its hazards and benefits. More modern technologies are harder to quantify. Some are renewable but still pollute (biofuels), some are very clean except in accidents or waste disposal (nuclear). Most electricity sources (renewable or not) use steam turbines, and all the water to make steam has to come from somewhere, but how important should that factor be?

Clicking the graphic above will give an abbreviated chart comparing sources line by line, but that doesn’t provide anywhere close to the whole story.

Each of the following topics compares the major sources of energy  through a different lens. Though environmental and local issues may seem the most important to those of us who don’t own power plants or utility companies, the cost of energy drives which sources are actually in place today and which sources will see investment tomorrow.












Source: U.S. Energy Information Administration

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Historical Events in Nuclear Fission

As is the case with so many scientific fields, the history of nuclear physics and energy development has always been wrapped up with the history of modern warfare.

An unprecedented level of research went into the American bomb program, applying a rapidly evolving understanding of nuclear physics immediately to building a weapon. That investment spurred the rest of the world to pursue nuclear fission, often using the energy as an excuse for the weapons development. Rather than isolate nuclear energy from its less peaceable counterpart, the timeline incorporates all types of nuclear history.

Recent nuclear media coverage:

Germany begins shutting down old reactors and considers swearing off nuclear power entirely. Germany Dims Nuclear Plants, but Hopes to Keep Lights On.

New evidence that Japan’s troubled reactors were destined to malfunction, tsunami or not, in The Explosive Truth Behind Fukushima’s Meltdown.

Add more here. TK

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