Cycles may be due to restorative forces causing repetition as in simple harmonic motion, regularity of motion such as daily, monthly, yearly, and other astronomical cycles, or being affected by something else that has these qualities. These forces may be physical, biological, economic or social.
Stonehenge is considered to have been used to predict eclipses, and is perhaps the earliest knowledge that we have of human interest in cycles. Other early studies of cycles are found in Vedic, Buddhist and Christian sacred books. Pythagoras' study of music and Ptolemy's motion of the planets were early scientific studies of cycles. Early studies of cycles were generally related to astronomical, astrological and weather and climatic cycles. Copernicus, Tycho Brahe, Kepler, Newton and Einstein contributed to ever refined understanding of the motion of the planets.
In modern times economic cycles were studied by Joseph Kitchen, Clement Juglar, Simon Kuznets and Nikolai Kondratieff, each of whom has an economic cycle named after them. There has been debate about the reality of some economic cycles.
Our understanding of weather cycles being attributable to annual and monthly astronomical motions was extended by Milutin Milankovitch who showed that ice ages were closely related to variations in the Earth's orbital eccentricity, axial tilt and the precession of the equinoxes which have periods of around 100,000 years, 40,000 years and 26,000 years respectively.
General cycles research pioneers were Chizhevsky in Russia and Raymond Wheeler in the USA. Ed Dewey, who formed the Foundation for the Study of Cycles in 1942, stated that everything that had been studied had been found to have cycles present. This includes cosmology, physics, biology, geology, climate, economics, sociology, civilisation, and history in general. It was Dewey who formulated the concepts of common cycle periods, cycle synchrony and harmonically related cycle periods.
Piccardi discovered inexplicable fluctuations in the rate of chemical reactions and Takata found that a human blood test he devised varied with time and depended on the sunspot cycle. Later Simon Shnoll and other researchers at the Russian Academy of Sciences found that such cycles were simultaneously happening in the growth of single celled organisms and in radioactive decay.
Through the middle part of the 20th century Abbott claimed to measure variations in the solar constant and links between the sunspot cycle and weather cycles on earth were vehemently denied by many scientists. With the coming of the artificial satellite age we have vastly better measures of both solar output and weather around the world and these cyclic links are now firmly established and accepted.
The now defunct Foundation for the Study of Cycles in the US and CIFA in Europe and Russia are organisations set up to study cycles and fluctuating phenomena. An interdisciplinary Internet discussion group on cycles allows cycles researchers from different fields to exchange ideas and results.
Mathematics of waves and cycles
Amplitude modulation - Amplitude - Beat - Chaos theory - Diffraction - Doppler effect - Eigenstate - Eigenvalue - Frequency domain - Frequency spectrum - George Gabriel Stokes - Hamiltonian (quantum mechanics) - Harmonic oscillator - Huygens' principle - Longitudinal wave - Mechanical wave - Partial differential equation - Permutation - Phase (waves) - Physics of music - Power spectrum - Signal - Sine-wave - Spectrum of an operator - Transverse wave - Wave equation - Wave - Waveform
Biological and medical cycles
Alternation of generations - Bioelectricity - Biological clock - Biological pest control - Bipolar disorder - Cardiopulmonary resuscitation - Calvin cycle - Cell cycle - Chronobiology - Citric acid cycle - Circadian rhythm - Claude Levi-Strauss - Clinical depression - Ecology - Feedback - Life cycle - List of biochemistry topics - Manfred Eigen - Marine biology - Neurofeedback - Non-Hodgkin's lymphoma - Organic farming - Polymerase chain reaction - Soil degradation - Stomach cancer - Triage - Zygote
Absorption spectroscopy - Anders Jonas %C5ngstr%F6m - Astronomy - Black body - Blazar - Bremsstrahlung - Caesium - Cherenkov radiation - Color - Colors - Diffraction - Digital signal processing - Direct-sequence spread spectrum - Dispersion (optics) - Eigenstate - Eigenvalue - Electromagnetic radiation - Electromagnetic spectroscopy - Electromagnetic spectrum - Electromagnetism - Emission line - Emission spectrum - FM broadcast radio - Frequency domain - Frequency hopping - Frequency spectrum - Gamma ray burster - George Gabriel Stokes - George Westinghouse - Hamiltonian (quantum mechanics) - History of radio - Hue - Isotope - Light - List of electronics topics - List of physics topics R-Z - NTSC - Optical brightener - Optical spectrum - Particle in a spherically symmetric potential - Piezoelectricity - Power spectrum - RADAR - Radio frequency - Radio - Radiocommunications Agency - Redshift - School Science Experiment - Demonstrating the properties of waves on an Oscilloscope - SETI - Spectrogram - Spectrometer - Spectroscopy - Spectrum analyser - Spectrum - Stellar spectroscopy - Sunyaev Zeldovic Effect - Supernova - Telecommunication - Timbre - Very high frequency - Visible light - White noise
Acoustic theory - Acoustics - Aerodynamics - Alvin Lucier - Amplitude - Anemometer - Beat - Bottlenose Dolphin - Bugging - Charles Cros - Cherenkov radiation - Cold fusion - Compressibility - Dayton Miller - Delay line memory - Diffraction - Doppler effect - Ear - Earpiece - Echo sounding - Electronic filter - FTIR - George Gabriel Stokes - Glossary of medical terms related to communications disorders - Johann Philipp Reis - Krakatau - Lee De Forest - Loudspeaker - Mach number - Microphone - Music theory - Ossicles - Pan pipes - Parabolic microphone - Phonetics - Phonons - Physics of music - Piezoelectricity - Prostate cancer - Psychoacoustics - Radio - Radiologist - Reginald Fessenden - Sawtooth wave - School physics experiments and demonstrations - Shock wave - SID - Sonar - Sonic boom - Sonoluminescence - Sound proofing - Sound recording - Sound - Speech signal processing - Speed of sound - Sperm Whale - Square wave - Subsonic - Subtractive synthesis - Synthesizer - Telecommunication - Telephone - Thomas A. Edison - Transmission line - Triangle wave - Wave drag - Waveform - Yamaha YM3812
Music and rhythm cycles
Antonin Dvorak - Daniel Barenboim - Dmitri Shostakovich - Free jazz - Fugue (music) - Gustav Mahler - Jean Sibelius - Music theory - Physics of music - Rhythm - Robert Schumann - Interval cycle
Economic and business cycles
Austrian School - Business cycle - Calvin Coolidge - Economy of Cape Verde - Economy of the United Kingdom - History of Seattle - History of the United States (1865-1918) - Joseph Schumpeter - Marxism - Marxist school of economics - Monetary policy of central banks - New classical economics - New Economy - Northern Ontario - Organization - Ragnar Frisch - Recession - Rise of the New Imperialism - Secularity - The Euro - Timeline of meteorology - United Kingdom - Virtuous circle and vicious circle
Belgian Congo - Climate change - Consciousness - Crop rotation - Education in the People's Republic of China - Environmental engineering - Fertile Crescent - Global warming and agriculture - Organic farming - Soil degradation - Sustainable industries
Climate and Weather cycles
Avalanche - Climate change - Climate model - Clock of the Long Now - Ecology - Endometrium - Environmental geography - Global cooling - Global warming and agriculture - Global warming - Historical temperature record - Ice age - Mars Polar Lander - Migration (human) - Milankovitch cycles - Milutin Milankovic - Monsoon - Sunspot - Timeline of meteorology - Pleistocene
Religious Myth and Spiritual cycles
Atharvaveda - Creation beliefs - Creationism (theology) - Dependent origination - Eschatology - Harvey Spencer Lewis - India - Irish mythology - Mantra - Maya (illusion) - Mythology - Resurrection of Jesus Christ - Samhain - Surya - Vedanta