3

Introduction

twentieth century. Planck’s and Einstein’s theories were the originators of quantum mechanics. Te for­

mulation of quantum mechanics was made by Niels Bohr, Werner Heisenberg, Erwin Schrödinger and

other physicists around the 1920s. Quantum mechanics is a mathematical theory that was introduced

in order to understand the behavior of atoms and particles. For example, quantum mechanics is used to

magnetically manipulate the spin of hydrogen atoms nuclei in the body for magnetic resonance imag­

ing (MRI), which is used greatly today in medicine and biology. In bioelectromagnetism, for instance,

quantum mechanics and classical physics now work together towards the clarifcations of a wide variety

of biological phenomena.

Electromagnetism or electromagnetic radiation of natural origins includes cosmic phenomena, the

sun, the earth and the atmosphere. Lightning strikes occur in the atmosphere which produces elec­

tric feld variations. Static electric felds are produced in the earth’s atmosphere between the earth’s

surface and the ionosphere, known as the global atmospheric electric circuit. An atmospheric electric

circuit is said to form between the negatively charged surface of earth and positively charged surface

of the ionosphere. Tis structure has a resemblance to that of the spherical capacitor. Te naturally

originated electric feld on earth is highest near the surface and can vary from about 100 to 150 V/m

during fair weather conditions to several thousand V/m during severe weather conditions such as

under thunderstorms.

Te earth is a huge magnet. Its magnetic feld is called geomagnetic feld or geomagnetism, with

strengths of about 60 μT at both poles and about 30 μT at the equator, and it can fuctuate with time

scales of millisecond to hours. Geomagnetism is believed to be caused by convection movements in the

liquid outer core of the earth. Te huge current of hundreds of millions to billions of amperes of conduc­

tive fuid fows through it. Tis is called self-excited magnetohydrodynamic dynamo.

Life of all organisms on earth has been formed and has evolved under the infuence of solar electro­

magnetic radiation. Te sun emits electromagnetic radiation starting from the ultraviolet (UV) region,

through the visible region until the infrared region, call optical radiation. About 45% of the radiation

falls within the visible region wavelength (400–780 nm). Te UV region is from below 100 to 400 nm, and

this region is further subdivided into UVC (100–280 nm), UVB (280–315 nm) and UVA (315–400 nm).

Te infrared region is subdivided into IRA (780–1,400 nm), IRB (1,400–3,000 nm) and IRC (3,000–1 mm).

Te possible interactions between electricity and magnetism with living organisms were known and

used in ancient times to treat headache and gout by using the electric shocks generated by electric fsh.

Te Swiss-born physician Paracelsus is believed to have used magnets to treat diarrhea, hernia, jaun­

dice and bleeding. Aferward, the Italian physician Luigi Galvani discovered bioelectricity through his

experiments with the lower limb muscles of frogs, which he claimed to have caused them to twitch when

stimulated by electricity.

1.2 The Connection between Electromagnetism

and Bioelectromagnetism

Since ancient times, electricity and magnetism were considered to be separate phenomena. In 1820,

Hans Christian Oersted showed that electricity and magnetism are a combined mechanical phenom­

enon. To explain this phenomenon, he used for the frst time the term “electromagnetism” in his paper

(Oersted, 1820). Aferward, Michael Faraday immediately gave the explanation and meaning to this

phenomenon and made active use of the term “electromagnetism,” which became established as a sci­

entifc term within a year (Faraday, 1821, 1822). Afer Oersted’s discovery, the scientifc knowledge in

electromagnetism was greatly improved. Tis improvement led to a better understanding of the basic

electromagnetic phenomena in bioelectromagnetism.

Electromagnetic waves exist on earth. James Clerk Maxwell proposed theoretically the mathematical

description of an electromagnetic wave in 1865. He considered that the components of the electromag­

netic wave are electric and magnetic felds, independently. Afer the discovery of the electromagnetic