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π The Clacks - discworld semaphore
The technology depicted in Terry Pratchett's Discworld novels takes two forms: magical and mechanical. Nearly all technology early in the series is at least partially magical, but in more recent books, a form of industrial revolution takes place, with numerous purely mechanical inventions being introduced. In Thud! ancient 'devices' of undisclosed origin and great power were introduced; it is not clear whether these are magical, mechanical, both or neither. Time-travel technology, the exact nature of which is usually unclear, is used by the History Monks. Most Discworld technologies have real-world equivalents, in function if not form.
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- "The Clacks - discworld semaphore" | 2009-12-09 | 20 Upvotes 3 Comments
π Antiobjects
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- "Antiobjects" | 2009-12-07 | 133 Upvotes 28 Comments
π Tell HN: There will be a Blue moon in December
A blue moon is an additional full moon that appears in a subdivision of a year: either the third of four full moons in a season, or a second full moon in a month of the common calendar.
The phrase in modern usage has nothing to do with the actual color of the Moon, although a visually blue Moon (the Moon appearing with a bluish tinge) may occur under certain atmospheric conditions β for instance, if volcanic eruptions or fires release particles in the atmosphere of just the right size to preferentially scatter red light.
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- "Tell HN: There will be a Blue moon in December" | 2009-12-07 | 29 Upvotes 8 Comments
π Claude Shannon
Claude Elwood Shannon (April 30, 1916 β February 24, 2001) was an American mathematician, electrical engineer, and cryptographer known as "the father of information theory". Shannon is noted for having founded information theory with a landmark paper, "A Mathematical Theory of Communication", that he published in 1948.
He is also well known for founding digital circuit design theory in 1937, whenβas a 21-year-old master's degree student at the Massachusetts Institute of Technology (MIT)βhe wrote his thesis demonstrating that electrical applications of Boolean algebra could construct any logical numerical relationship. Shannon contributed to the field of cryptanalysis for national defense during World War II, including his fundamental work on codebreaking and secure telecommunications.
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- "Claude Shannon" | 2009-12-03 | 25 Upvotes 12 Comments
π Help keep the Y Combinator Wikipedia page updated
YΒ Combinator is an American seed accelerator launched in March 2005 and has been used to launch over 2,000 companies including Stripe, Airbnb, Cruise Automation, DoorDash, Coinbase, Instacart, and Dropbox. The combined valuation of the top YC companies was over $155Β billion as of October, 2019.
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- "Help keep the Y Combinator Wikipedia page updated" | 2009-11-24 | 37 Upvotes 39 Comments
π IQ and the Wealth of Nations
IQ and the Wealth of Nations is a 2002 book by psychologist Richard Lynn and political scientist Tatu Vanhanen. The authors argue that differences in national income (in the form of per capita gross domestic product) are correlated with differences in the average national intelligence quotient (IQ). They further argue that differences in average national IQs constitute one important factor, but not the only one, contributing to differences in national wealth and rates of economic growth.
The book has drawn widespread criticism from other academics. Critiques have included questioning of the methodology used, the incompleteness of the data, and the conclusions drawn from the analysis. The 2006 book IQ and Global Inequality is a follow-up to IQ and the Wealth of Nations by the same authors.
Discussed on
- "IQ and the Wealth of Nations" | 2009-11-22 | 13 Upvotes 10 Comments
π The Interesting Number Paradox
The interesting number paradox is a semi-humorous paradox which arises from the attempt to classify every natural number as either "interesting" or "uninteresting". The paradox states that every natural number is interesting. The "proof" is by contradiction: if there exists a non-empty set of uninteresting natural numbers, there would be a smallest uninteresting number β but the smallest uninteresting number is itself interesting because it is the smallest uninteresting number, thus producing a contradiction.
In a discussion between the mathematicians G. H. Hardy and Srinivasa Ramanujan about interesting and uninteresting numbers, Hardy remarked that the number 1729 of the taxicab he had ridden seemed "rather a dull one", and Ramanujan immediately answered that it is interesting, being the smallest number that is the sum of two cubes in two different ways.
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- "The Interesting Number Paradox" | 2009-11-14 | 65 Upvotes 9 Comments
π Go! -- the non-Google programming language by Keith Clark and Francis McCabe.
Go! is an agent-based programming language in the tradition of logic-based programming languages like Prolog. It was introduced in a 2003 paper by Francis McCabe and Keith Clark.
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- "Go! -- the non-Google programming language by Keith Clark and Francis McCabe." | 2009-11-11 | 82 Upvotes 49 Comments
π Comfort Noise
Comfort noise (or comfort tone) is synthetic background noise used in radio and wireless communications to fill the artificial silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines.
Some modern telephone systems (such as wireless and VoIP) use voice activity detection (VAD), a form of squelching where low volume levels are ignored by the transmitting device. In digital audio transmissions, this saves bandwidth of the communications channel by transmitting nothing when the source volume is under a certain threshold, leaving only louder sounds (such as the speaker's voice) to be sent. However, improvements in background noise reduction technologies can occasionally result in the complete removal of all noise. Although maximizing call quality is of primary importance, exhaustive removal of noise may not properly simulate the typical behavior of terminals on the PSTN system.
The result of receiving total silence, especially for a prolonged period, has a number of unwanted effects on the listener, including the following:
- the listener may believe that the transmission has been lost, and therefore hang up prematurely.
- the speech may sound "choppy" (see noise gate) and difficult to understand.
- the sudden change in sound level can be jarring to the listener.
To counteract these effects, comfort noise is added, usually on the receiving end in wireless or VoIP systems, to fill in the silent portions of transmissions with artificial noise. The noise generated is at a low but audible volume level, and can vary based on the average volume level of received signals to minimize jarring transitions.
In many VoIP products, users may control how VAD and comfort noise are configured, or disable the feature entirely.
As part of the RTP audio video profile, RFC 3389 defines a standard for distributing comfort noise information in VoIP systems.
A similar concept is that of sidetone, the effect of sound that is picked up by a telephone's mouthpiece and introduced (at low level) into the earpiece of the same handset, acting as feedback.
During the siege of Leningrad, the beat of a metronome was used as comfort noise on the Leningrad radio network, indicating that the network was still functioning.
Many radio stations broadcast birdsong, city-traffic or other atmospheric comfort noise during periods of deliberate silence. For example, in the UK, silence is observed on Remembrance Sunday, and London's quiet city ambiance is used. This is to reassure the listener that the station is on-air, but primarily to prevent silence detection systems at transmitters from automatically starting backup tapes of music (designed to be broadcast in the case of transmission link failure).
Discussed on
- "Comfort Noise" | 2009-10-31 | 54 Upvotes 10 Comments
π Laws of Power: Machiavelli and Sun-Tzu brought up-to-date
The 48 Laws of Power (1998) is a non-fiction book by American author Robert Greene. The book is a bestseller, selling over 1.2 million copies in the United States, and is popular with prison inmates and celebrities.
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- "Laws of Power: Machiavelli and Sun-Tzu brought up-to-date" | 2009-10-27 | 27 Upvotes 19 Comments