Elementary Meteorology Online
Chapter 3 - Solar and terrestrial radiation:


Return to index, Introduction, Matter, Energy, Heat, Absolute Zero
Sources:
  • Pidwirny, M. (2006). Fundamentals of Physical Geography, 2nd Edition. (Monday, September 18 2006)


    • Introduction

    Energy is defined simply by scientists as the capacity for doing work. Matter is the material (atoms and molecules) that constructs things on the Earth and in the Universe. Albert Einstein suggested early in this century that energy and matter are related to each other at the atomic level. Einstein theorized that it should be possible to convert matter into energy. From Einstein's theories, scientists were able to harness the energy of matter beginning in the 1940s through nuclear fission. The sun releases the same nuclear energy through fusion.


    Matter

    Matter is the material that makes up things in the Universe. All matter on the Earth is constructed of atoms. Substances made up of single atoms are called elements (see WebElements for the periodic table of elements). Chemists have described approximately 115 different elements. Each of these elements have distinct chemical characteristics.

    Protons and neutrons make up the nucleus at the center of an atom. Protons are positively charged so the nucleus has a positive charge equal to the number of protons. Electrons are found orbiting outside the nucleus at various distances based on their energy level. The area occupied by the electrons has a negative charge equal to the number of these subatomic particles. Protons are much larger and heavier than electrons. As a result, most of an atom's mass is concentrated in the nucleus. If an atom has an equal number of electrons and protons its net electrical charge is zero. If there are more electrons than protons the charge of the atom is negative. Likewise, if there are less electrons than protons the charge of the atom is positive. Elements with a net positive or negative charge are called ions.

    Positive and negative ions are electrically attracted to each other. This mutual attraction allows for the bonding of atoms to occur forming structures of matter that are larger than just one atom. When similar atoms bond together they construct molecules. Atoms of different elements joined together form compounds.

    Gases are compounds whose molecules move around freely. Below are some examples of gas molecules found in the atmosphere.

    Solids are compounds whose molecules are held in place by the chemical bonds between their atoms. Below is an example of sodium chloride or table salt.


    Energy

    Energy

    Energy comes in a variety of forms. The simplest definition of the types of energy suggests that two forms exist: kinetic energy and potential energy.

  • Kinetic energy is the energy due to motion. A rock falling from a cliff, a bee in flight, wind blowing leaves of trees, and water following over a waterfall are all examples of kinetic energy.
    • Heat energy is the kinetic energy of molecules in matter. The molecules of hot substances move faster than the molecules of substances with cold temperatures. A substance with no molecular motion is said to be at absolute zero.
    • Sound, seismic waves, ocean waves also are forms of kinetic energy.
  • Potential energy is the energy stored in matter that can be potentially transformed into another form of energy. Water stored behind a dam, the chemical energy of the food we consume, and the gasoline that we putting in our cars are all examples of potential energy. Conversion of this energy occurs when the energy in food is used for metabolism and it has been digested, when the water in the dam flows through turbines to produce electricity from motion, and when the gasoline is used in a engine to produce motion from combustion. In this case, we refer to the energy flowing from one system (e.g. food, a water reservoir) to another (human body, electrical power lines). In this chapter , we focus on the transfer of energy from the sun to the earth.

    • Chemical Energy - is stored in bonds holding molecules together and released in chemical reactions. Fire is an example of such an energy realease.
    • Electromagnetic Energy - is energy stored in the electric and magnetic fields that surround charged particles.
    • Atomic or Nuclear Energy - is energy released when the bonds holding the nucleus together are broken. Nuclear reactions convert mass. to electromagnetic radiation. The Sun and hydrogen bombs release atomic energy. This conversion is calculated using Einstein's famous equation E=mc2, where E is the energy, m is the mass in kg, and c is the speed of light. The speed of light is a huge number, so small amounts of mass can release huge amounts of energy (See picture below!).


  • Electromagnetic Radiation - is the emission and propagation of energy in the form of electromagnetic waves. The release of potential chemica and atomic Radiowaves, microwaves, light and X-rays. Any object with a temperature above absolute zero (-273° Celsius) emits this type of energy. Objects at room temperature emit infrared radiation. Chemical reactions like fire generally involve the release of infrared (heat) readiation and visible light. Nuclear reactions on the sun emit mostly visible light, but also a large amounts of other radiation. Solar flares emit streams of high energy protons and electrons known as alpha and beta radiation.

    • Heat

    One important form of energy, relative to life on Earth, is kinetic energy. Simply defined, kinetic energy is the energy of motion. The amount of kinetic energy that a body possesses is dependent on the speed of its motion and its mass. At the atomic scale, the kinetic energy of atoms and molecules is sometimes referred to as heat energy.

    Kinetic energy is also related to the concept of temperature. Temperature is defined as the measure of the average speed of atoms and molecules. The higher the temperature, the faster these particles of matter move. At a temperature of - 273.15° Celsius (absolute zero) all atomic motion stops. Heat is often defined as energy in the process of being transferred from one object to another because of the temperature difference between them. Heat is transferred from the Sun to the Earth through electromagnetic radiation. For an entertaining tutorial explaining heat and absolute zero, please click here or on the image of cordoroy Bob at left..

    Absolute Zero and Kelvin scale

    Absolute zero is the lowest possible temperature. All molecular motion ceases at this temperature. When calculating the heat energy of matter, scientists use the Kelvin scale.



    This is the same as the Celsius scale, but begins with 0 at absolute zero instead of the freezing point of water. You therefor cannot have negative Kelvin values. In reality, matter doesn't reach absolute zero. If it did, we wouldn't see it: because it would be perfectly still and emit no radiation. It would be invisible!

    zero