Archive for February 8th, 2012

February 8, 2012

Prehistoric Music

divje babe flute

Prehistoric music (previously called primitive music) is a term in the history of music for all music produced in preliterate cultures (prehistory), beginning somewhere in very late geological history. Prehistoric music is followed by ancient music in different parts of the world, but still exists in isolated areas.

Prehistoric music thus technically includes all of the world’s music that has existed before the advent of any currently-extant historical sources concerning that music, for example, traditional Native American music of preliterate tribes and Australian Aboriginal music. However, it is more common to refer to the ‘prehistoric’ music which still survives as folk, indigenous or traditional music. Prehistoric music is studied alongside other periods within Music Archaeology.

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February 8, 2012



The pregap on a Red Book audio CD is the portion of the audio track that precedes ‘index 01’ for a given track in the table of contents (TOC). The pregap (‘index 00’) is typically two seconds long and usually, but not always, contains silence. Popular uses for having the pregap contain audio are live CDs, track interludes, and hidden songs in the pregap of the first track. On certain CDs, such as ‘Think Tank’ by Blur, the pregap contains a hidden track. The track is truly hidden in the sense that most conventional standalone players and software CD players will not see it. Such hidden tracks can be played by playing the first song and ‘rewinding’ (more accurately, seeking in reverse) until the actual start of the whole CD audio track. Not all CD drives can properly extract such hidden tracks. Some drives will report errors when reading these tracks, and some will seem to extract them properly, but the extracted file will contain only silence.

The pregap was used to hide computer data, tricking computers into detecting a data track whereas conventional CD players would continue to see the CD as an audio CD. This method was quickly made obsolete in late 1996 when an update to Windows 95 made the pregap track inaccessible. It is unclear whether or not this change in Microsoft Windows’ behavior was intentional: for instance, it may have been intended to steer developers away from the pregap method and encourage what became the Blue Book specification ‘CD Extra’ format.

February 8, 2012



A micromort is a unit of risk measuring a one-in-a-million probability of death (from micro- and mortality). Micromorts can be used to measure riskiness of various day-to-day activities. A microprobability is a one-in-a million chance of some event; thus a micromort is the microprobability of death. The micromort concept was introduced by Ronald A. Howard who pioneered the modern practice of decision analysis.

An application of micromorts is measuring the value that humans place on risk: for example, one can consider the amount of money one would have to pay a person to get him or her to accept a one-in-a-million chance of death (or conversely the amount that someone might be willing to pay to avoid a one-in-a-million chance of death).

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February 8, 2012

Manifold Destiny

Grigori Perelman by Antonio Guzman

Manifold Destiny‘ is a 2006 article in ‘The New Yorker’ written by Sylvia Nasar (known for her biography of John Forbes Nash, ‘A Beautiful Mind’) and David Gruber. It gives a detailed account (including interviews with many mathematicians) of some of the circumstances surrounding the proof of the Poincaré conjecture, one of the most important accomplishments of 20th and 21st century mathematics, and traces the attempts by three teams of mathematicians to verify the proof given by Grigori Perelman.

Subtitled ‘A legendary problem and the battle over who solved it,’ the article concentrates on the human drama of the story, especially the discussion on who contributed how much to the proof of the Poincaré conjecture. Interwoven with the article is an interview with the reclusive mathematician Grigori Perelman, whom the authors tracked down to the St. Petersburg apartment he shares with his mother. The article describes Perelman’s disillusionment and withdrawal from the mathematical community and paints an unflattering portrait of the 1982 Fields Medalist, Shing-Tung Yau.

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February 8, 2012

Grigori Perelman

Poincaré conjecture

Grigori Perelman (b. 1966) is a Russian mathematician who has made landmark contributions to geometry and topology (the study of geometric deformation). In 1992, Perelman proved the soul conjecture. In 2002, he proved Thurston’s geometrization conjecture. This consequently solved in the affirmative the Poincaré conjecture, posed in 1904, which before its solution was viewed as one of the most important and difficult open problems in topology.

In 2006, Perelman was awarded the Fields Medal, but declined to accept the award or to appear at the congress, stating: ‘I’m not interested in money or fame, I don’t want to be on display like an animal in a zoo.’ In 2010, it was announced that he had met the criteria to receive the first Clay Millennium Prize for resolution of the Poincaré conjecture. He turned down the prize ($1 million), saying that he considers his contribution to proving the Poincaré conjecture to be no greater than that of U.S. mathematician Richard Hamilton.

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