An Introduction to Electromagnetic Fields
Electromagnetism is one of the four forces used in modern physics. Each force can be described mathematically as a "field." A field is a volume of air or space where each point is affected in a way defined by the mathematical definition of the force.
Gravitation and electromagnetism produce forces or energy that interact with matter at large distances, like keeping a planet in orbit (gravitation), or feeling the warmth of the sun (electromagnetic energy). The other two forces in physics are used to describe actions between components of an atom. Here we are concerned only with electromagnetic fields.
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The (static) electric field and natural magnetic fields were first discovered and investigated separately. An electric charge (electrons) produces an electric field. When there is a complete path in a circuit, a current flows, defined as the movement of electrons. When this flow occurs, a magnetic field is created. When an electric field varies over time (oscillates) a corresponding oscillating magnetic field is produced. So electricity and magnetism exist together and the field created is called an electromagnetic field, or electromagnetic radiation.
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Electromagnetic radiation is usually described as radiating energy waves with a specific frequency. Since electromagnetic radiation travels at the speed of light, the lower the frequency, the longer the wavelength.
All of the natural Electromagnetic radiation that reaches the surface of earth comes from our sun, or other objects in the universe. The sun actually radiates energy from very low frequency radio waves all the way to very high frequency x-rays. The maximum output of the sun is in the visible light range of colors that we detect with our eyes, at about 500 nano-meters wavelength. Due to the filtering effect of our atmosphere, almost no ionizing radiation from the sun reaches the surface of earth.
The earth has a natural electromagnetic frequency, created by electrical charges moving between the earth's surface and a layer in the atmosphere called the ionosphere that starts about 40 miles up, that acts as a reflector. It is called the Schumann Resonance after Winfried Schumann, who predicted it mathematically in 1952. Its primary frequency is 7.83 cycles per second. This is essentially the pulse of the earth, and our hearts and brains are in tune with it. In the human brain this frequency is the Alpha waves. This is the range of brain activity that supports body/mind coordination, thinking, creativity, alertness and learning. It is the frequency that holds most of our experience of being "alive"!
The electromagnetic spectrum goes from these extremely low frequency levels through all of the technology humans have invented to send information on electromagnetic waves at higher and higher frequencies. At the highest frequencies of non-ionizing radiation is visible light. Beyond visible light is the ultraviolet frequencies and the beginning of ionizing radiation, like x-rays. Radiation at the frequency of x-rays and above is called ionizing radiation because it has enough energy to remove electrons out of atomic orbit and create an ion. And in the universe there are energy sources with much higher energies and frequencies. In the graph of the EMR spectrum at the right, from NASA's Imagine the Universe, the only thing shown in the microwave range is a microwave oven. But the microwave portion of the spectrum contains the man-made raditation used for all of our mobile phone communication, WiFi connections, cordless phones, smart TVs, baby monitors, smart meters and more.
Credit: STScI/JHU/NASA
Credit: geosciencebigpicture.com
Humans have senses that can detect only a very small portion of the entire spectrum of EMR. Visible light that our eyes see gives us most of our life experiences. At wavelengths shorter than the visible light range is ultraviolet radiation, and we sense too much exposure as sunburn. It is simple to react and protect yourself from this. The atmosphere provides protection from even shorter wavelengths (higher frequencies). We detect wavelengths in the infra-red range (longer than visible light) as heat on our skin. It is also very easy to protect yourself from that radiation.
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Our bodies have no senses to detect any of the remaining radiation in the electromagnetic spectrum with longer wavelengths than infra-red. This includes all the frequencies modern civilization uses for cell phones, WiFi, television and radio. When there is enough power, these wavelengths actually start to burn our flesh, the way a microwave oven (same frequency as WiFi) cooks meat. But for decades, scientists have found biological damage occurs at power levels far below the amount needed to heat our flesh. The manufacturers of all the modern conveniences we use, and most are addicted to, continue to deny this fact. Government agencies that are supposed to protect us also deny it. And as time goes by, man-made radiation becomes more dangerous to all life on the planet.
