Energy

Our universe was born about 14 billion years ago in a huge explosion called the Big Bang. As the universe expanded and cooled down, forms of matter condensed out of the cosmic soup. 

Three minutes after the Big Bang, the building blocks for simple atoms like hydrogen and helium had already formed. These building blocks clumped together thanks to gravity to form the first stars and galaxies about 200 million years after the Big Bang. Elements heavier than iron came about when these stars explored in a supernovae. 

Our sun and solar system was formed just 5 billion years ago, with life on Earth about a billion years later. We humans came on the scene toward the end of that period, which accounts for our present state of evolution. 

Today's Lesson: 

ENERGY

A primary component of our cosmic soup is ENERGY, the radiant energy in light and the mass in protons, neutrons, and electrons. 

(Remember, in terms of physics, chemistry, and biology, the universe is made of atoms and elementary particles, such as electrons, protons, quarks, and neutrinos). 

As you learned in middle school, energy is the ability to do work. Basically, energy makes physical systems do stuff. 

Energy can be conserved: it can take different forms - heat, work, electrical energy, mechanical energy - but it is never lost. THIS IS KNOWN AS THE FIRST LAW OF THERMODYNAMICS. 

I know what you're going to ask. If energy can be conserved, and if the universe started from nothing, then where did all the energy come from??? 

Excellent question! 

Quantum mechanics (a term you hear thrown around a lot these days without being fully understood) describes energy in terms of quantum fields, a kind of background or what they call underlying fabric of the universe (like a layer in Photoshop), whose wave makes up the elementary particles - photons, electrons, quarks. 

So, the energy we see around us (Earth, stars, light, heat) came out of the underlying quantum fields (that background Photoshop layer) by the expansion of our universe. 

As you recall, gravity is an attractive force that pulls things together. As the universe expands, gravity acts like a vampire, sucking energy out of the quantum fields. Most of the energy in the quantum fields is positive. This positive energy is balanced (for the most part) by the negative energy of gravitational attraction. The further we expand, the more positive energy becomes available to us, in the forms of latter and light. 

ENERGY BASICS 

Energy comes in different forms: 

• Heat (thermal) 
• Light (radiant) 
• Motion (kinetic) 
• Electrical
• Chemical 
• (The food you eat contains chemical energy, and your body stores this energy until you use it or when you work or play). 
• Nuclear energy
• Gravitational

There are two types of energy: 

• Stored (potential) energy
• Working (kinetic) energy

RENEWABLE or NONRENEWABLE ENERGY

The electrical energy in our homes was probably generated by burning coal, by a nuclear reaction, or by a hydroelectric plant at a dam. Therefore, coal, nuclear and hydro are called energy sources. When we get gasoline for our cars, the source might be petroleum or ethanol made by growing and processing corn. 

Renewable means that an energy source can be easily replenished. Nonrenewable means that an energy source is being used up and cannot be recreated). 

Renewable energy sources include: 

• Solar energy from the sun, which can be turned into electricity and heat
• Wind
• Geothermal energy from heat inside the Earth
• Biomass from plants, which includes firewood from trees, ethanol from corn, and biodiesel from vegetable oil
• Hydropower from hydroturbines at a dam

Nonrenewable energy sources include: 

• Fossil fuels - oil, natural gas, and coal (fossils)
• Uranium (we split these atoms in a process called nuclear fission to create heat and electricity)

FORMS OF ENERGY

As we discussed, energy is found in different forms (light, heat, chemical, motion). While there are many forms of energy, we divide them into two categories: POTENTIAL energy and KINETIC energy. 

POTENTIAL ENERGY

Potential energy is stored energy and the energy of position. Checmical energy is stored in the bonds of atoms and molecules. Batteries, biomass, petroleum, natural gas, and coal are examples of stored chemical energy. When you burn wood in your fireplace, you're converting chemical energy to thermal energy. 

Mechanical energy is energy stored in objects by tension. Compressed springs and stretched ponytail bands are examples of stored mechanical energy. 

Nuclear energy is stored in the nucleus of an atom (the energy holds the nucleus together). Very large amounts of energy can be released when the nuclei are combined or split apart. Nuclear power plants split apart energy in the process known as fission, whereas the sun combines the nuclei of hydrogen atoms in a process called fusion. (Fission takes things apart, fusion puts things back together). 

Gravitational energy is the energy stored in an object's height. The higher and heavier the object, the more gravitational energy is stored. When you ride your bike down "Killer Hill" (for example) and you pick up speed, the gravitational energy is being converted into motion energy. 

Hydropower is another example of gravitational energy, where the dam "piles" up water from a river into a reservoir. 

KINETIC ENERGY 

Kinetic energy is motion (waves, electrons, atoms, molecules, substances, and objects). 

Radiant energy is electromagnetic energy that travels in transverse waves. Radiant energy includes visible light, x-rays, gamma rays and radio waves.  Light and sunshine are radiant forms of energy, which provide fuel and warmth that makes life on Earth possible. 

Thermal energy (heat) is the vibration and movement of the atoms and molecules within substances. As an object is heated up, its atoms and molecules move and collide faster. Geothermal energy is the thermal energy inside the Earth. 

Motion energy is energy stored in the movement of objects. The faster they move, the more energy is stored. It takes energy to get an object moving, and when an object slows down, energy is released. Wind is an example of motion energy. 

Sound is the movement of energy through substances in longitudinal (compression/rarefaction) waves. Sound is produced when a force causes an object or substance to vibrate - the energy is transferred through the substance in a wave. Sound energy has less energy than other forms of energy. 

Electrical Energy is delivered by charged electrons (usually moving through a wire). Lightening is a very powerful, natural form of electrical energy.