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*[http://en.wikipedia.org/wiki/1960 1960]

*[https://en.wikipedia.org/wiki/1960 1960]

==Definitions==

==Definitions==

*1:  an innately determined [[rhythmic]] [[biological]] [[process]] or [[function]] (as [[sleep]] behavior); also :  the internal [[mechanism]] that determines such a process or function  

*1:  an innately determined [[rhythmic]] [[biological]] [[process]] or [[function]] (as [[sleep]] behavior); also :  the internal [[mechanism]] that determines such a process or function  

According to believers in ''biorhythms'', a person's [[life]] is influenced by rhythmic biological [[cycles]] that affect one's [[ability]] in various domains, such as [[mental]], [[physical]] and [[emotional]] activity. These cycles begin at [[birth]] and oscillate in a steady (sine wave) fashion throughout life; thus, by [[modeling]] them mathematically, a person's level of ability in each of these domains can be [[predicted]] from day to day.

According to believers in ''biorhythms'', a person's [[life]] is influenced by rhythmic biological [[cycles]] that affect one's [[ability]] in various domains, such as [[mental]], [[physical]] and [[emotional]] activity. These cycles begin at [[birth]] and oscillate in a steady (sine wave) fashion throughout life; thus, by [[modeling]] them mathematically, a person's level of ability in each of these domains can be [[predicted]] from day to day.

Most biorhythm models use three cycles: a 23-day "[[physical]]" cycle, a 28-day "[[emotional]]" cycle, and a 33-day "[[intellectual]]" cycle. Although the 28-day cycle is the same length as the average woman's [http://en.wikipedia.org/wiki/Menstrual_cycle menstrual cycle] and was originally described as a "[[female]]" cycle, the two are not necessarily in any particular [[synchronization]]. Each of these cycles varies between high and low [[extremes]] sinusoidally, with days where the cycle crosses the zero line described as "critical days" of greater [[risk]] or [[uncertainty]].

Most biorhythm models use three cycles: a 23-day "[[physical]]" cycle, a 28-day "[[emotional]]" cycle, and a 33-day "[[intellectual]]" cycle. Although the 28-day cycle is the same length as the average woman's [https://en.wikipedia.org/wiki/Menstrual_cycle menstrual cycle] and was originally described as a "[[female]]" cycle, the two are not necessarily in any particular [[synchronization]]. Each of these cycles varies between high and low [[extremes]] sinusoidally, with days where the cycle crosses the zero line described as "critical days" of greater [[risk]] or [[uncertainty]].

The notion of periodic [[cycles]] in human fortunes is [[ancient]]; found for instance in [http://en.wikipedia.org/wiki/Natal_astrology natal astrology] and in folk [[beliefs]] about "[[lucky]] days." The 23- and 28-day rhythms used by biorhythmists, however, were first devised in the late 19th century by [http://en.wikipedia.org/wiki/Wilhelm_Fliess Wilhelm Fliess], a Berlin physician and patient of [[Sigmund Freud]]. Fliess believed that he observed regularities at 23- and 28-day intervals in a number of [[phenomena]], including [[births]] and [[deaths]]. He labeled the 23-day rhythm "[[male]]" and the 28-day rhythm "[[female]]," matching the menstrual cycle.

The notion of periodic [[cycles]] in human fortunes is [[ancient]]; found for instance in [https://en.wikipedia.org/wiki/Natal_astrology natal astrology] and in folk [[beliefs]] about "[[lucky]] days." The 23- and 28-day rhythms used by biorhythmists, however, were first devised in the late 19th century by [https://en.wikipedia.org/wiki/Wilhelm_Fliess Wilhelm Fliess], a Berlin physician and patient of [[Sigmund Freud]]. Fliess believed that he observed regularities at 23- and 28-day intervals in a number of [[phenomena]], including [[births]] and [[deaths]]. He labeled the 23-day rhythm "[[male]]" and the 28-day rhythm "[[female]]," matching the menstrual cycle.

In 1904, psychology professor Hermann Swoboda claimed to have independently discovered the same [[cycles]]. Later, Alfred Teltscher, professor of engineering at the University of Innsbruck, came to the [[conclusion]] that his students' good and bad days followed a rhythmic pattern of 33 days. Teltscher believed that the brain's [[ability]] to [[absorb]], mental ability, and alertness ran in 33-day cycles. One of the first [[academic]] researchers of biorhythms was also Estonian-born Nikolai Pärna, who published a book in German, called "Rhythm, life and creation" in 1923.

In 1904, psychology professor Hermann Swoboda claimed to have independently discovered the same [[cycles]]. Later, Alfred Teltscher, professor of engineering at the University of Innsbruck, came to the [[conclusion]] that his students' good and bad days followed a rhythmic pattern of 33 days. Teltscher believed that the brain's [[ability]] to [[absorb]], mental ability, and alertness ran in 33-day cycles. One of the first [[academic]] researchers of biorhythms was also Estonian-born Nikolai Pärna, who published a book in German, called "Rhythm, life and creation" in 1923.

The [[practice]] of consulting biorhythms was popularized in the [http://en.wikipedia.org/wiki/1970's 1970s] by a series of books by Bernard Gittelson, including ''Biorhythm — A Personal Science, Biorhythm Charts of the Famous and Infamous'', and ''Biorhythm Sports Forecasting''. Gittelson's company, Biorhythm Computers, Inc., made a business selling personal biorhythm charts and calculators, but his ability to [[predict]] sporting events was not substantiated.

The [[practice]] of consulting biorhythms was popularized in the [https://en.wikipedia.org/wiki/1970's 1970s] by a series of books by Bernard Gittelson, including ''Biorhythm — A Personal Science, Biorhythm Charts of the Famous and Infamous'', and ''Biorhythm Sports Forecasting''. Gittelson's company, Biorhythm Computers, Inc., made a business selling personal biorhythm charts and calculators, but his ability to [[predict]] sporting events was not substantiated.

Charting biorhythms for personal use was popular in the [[United States]] during the [http://en.wikipedia.org/wiki/1970's 1970]s; many places (especially video arcades and amusement areas) had a biorhythm machine that provided charts upon entry of date of [[birth]]. Biorhythm charts were common in newspapers, usually found with horoscopes, at the time as well. Biorhythm programs were a common application on personal computers; and in the late 1970s there were also handheld biorhythm calculators on the market, the Kosmos 1 and the Casio Biolator. Though biorhythms have declined in [[popularity]], there are numerous websites on the [[Internet]] that offer free biorhythm readings. In addition, there exist free and proprietary software programs that offer more advanced charting and [[analysis]] capabilities.[http://en.wikipedia.org/wiki/Biorhythm]

Charting biorhythms for personal use was popular in the [[United States]] during the [https://en.wikipedia.org/wiki/1970's 1970]s; many places (especially video arcades and amusement areas) had a biorhythm machine that provided charts upon entry of date of [[birth]]. Biorhythm charts were common in newspapers, usually found with horoscopes, at the time as well. Biorhythm programs were a common application on personal computers; and in the late 1970s there were also handheld biorhythm calculators on the market, the Kosmos 1 and the Casio Biolator. Though biorhythms have declined in [[popularity]], there are numerous websites on the [[Internet]] that offer free biorhythm readings. In addition, there exist free and proprietary software programs that offer more advanced charting and [[analysis]] capabilities.[https://en.wikipedia.org/wiki/Biorhythm]

[[Category: General Reference]]

[[Category: General Reference]]