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The photophone is a telecommunications device that allows transmission of speech on a beam of light. It was invented jointly by Alexander Graham Bell and his assistant Charles Sumner Tainter on February 19, 1880, at Bell's laboratory at 1325 L Street in Washington, D.C. Both were later to become full associates in the Volta Laboratory Association, created and financed by Bell.

On June 3, 1880, Bell's assistant transmitted a wireless voice telephone message from the roof of the Franklin School to the window of Bell's laboratory, some 213 meters (about 700 ft.) away.

Bell believed the photophone was his most important invention. Of the 18 patents granted in Bell's name alone, and the 12 he shared with his collaborators, four were for the photophone, which Bell referred to as his "greatest achievement", telling a reporter shortly before his death that the photophone was "the greatest invention [I have] ever made, greater than the telephone".

The photophone was a precursor to the fiber-optic communication systems that achieved worldwide popular usage starting in the 1980s. The master patent for the photophone (U.S. Patent 235,199 Apparatus for Signalling and Communicating, called Photophone) was issued in December 1880, many decades before its principles came to have practical applications.

🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Intelligence 🔗 Military history/Cold War 🔗 Military history/Australia, New Zealand and South Pacific military history 🔗 Military history/Canadian military history 🔗 Military history/European military history 🔗 Military history/British military history

The Five Eyes (FVEY) is an anglophone intelligence alliance comprising Australia, Canada, New Zealand, the United Kingdom and the United States. These countries are parties to the multilateral UKUSA Agreement, a treaty for joint cooperation in signals intelligence.

The origins of the FVEY can be traced back to the post–World War II period, when the Atlantic Charter was issued by the Allies to lay out their goals for a post-war world. During the course of the Cold War, the ECHELON surveillance system was initially developed by the FVEY to monitor the communications of the former Soviet Union and the Eastern Bloc, although it is now used to monitor billions of private communications worldwide.

In the late 1990s, the existence of ECHELON was disclosed to the public, triggering a major debate in the European Parliament and, to a lesser extent, the United States Congress. As part of efforts in the ongoing War on Terror since 2001, the FVEY further expanded their surveillance capabilities, with much emphasis placed on monitoring the World Wide Web. The former NSA contractor Edward Snowden described the Five Eyes as a "supra-national intelligence organisation that does not answer to the known laws of its own countries". Documents leaked by Snowden in 2013 revealed that the FVEY has been spying on one another's citizens and sharing the collected information with each other in order to circumvent restrictive domestic regulations on surveillance of citizens.

In spite of continued controversy over its methods, the Five Eyes relationship remains one of the most comprehensive known espionage alliances in history.

Since processed intelligence is gathered from multiple sources, the intelligence shared is not restricted to signals intelligence (SIGINT) and often involves defence intelligence as well as human intelligence (HUMINT) and geospatial intelligence (GEOINT). The following table provides an overview of most of the FVEY agencies involved in such forms of data sharing.

🔗 Computing 🔗 Computer science 🔗 Cryptography 🔗 Cryptography/Computer science

Diffie–Hellman key exchange is a method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols as conceived by Ralph Merkle and named after Whitfield Diffie and Martin Hellman. DH is one of the earliest practical examples of public key exchange implemented within the field of cryptography.

Traditionally, secure encrypted communication between two parties required that they first exchange keys by some secure physical means, such as paper key lists transported by a trusted courier. The Diffie–Hellman key exchange method allows two parties that have no prior knowledge of each other to jointly establish a shared secret key over an insecure channel. This key can then be used to encrypt subsequent communications using a symmetric key cipher.

Diffie–Hellman is used to secure a variety of Internet services. However, research published in October 2015 suggests that the parameters in use for many DH Internet applications at that time are not strong enough to prevent compromise by very well-funded attackers, such as the security services of large governments.

The scheme was published by Whitfield Diffie and Martin Hellman in 1976, but in 1997 it was revealed that James H. Ellis, Clifford Cocks, and Malcolm J. Williamson of GCHQ, the British signals intelligence agency, had previously shown in 1969 how public-key cryptography could be achieved.

Although Diffie–Hellman key agreement itself is a non-authenticated key-agreement protocol, it provides the basis for a variety of authenticated protocols, and is used to provide forward secrecy in Transport Layer Security's ephemeral modes (referred to as EDH or DHE depending on the cipher suite).

The method was followed shortly afterwards by RSA, an implementation of public-key cryptography using asymmetric algorithms.

Expired U.S. Patent 4,200,770 from 1977 describes the now public-domain algorithm. It credits Hellman, Diffie, and Merkle as inventors.

🔗 Computer science

In computer science, the Knuth–Morris–Pratt string-searching algorithm (or KMP algorithm) searches for occurrences of a "word" W within a main "text string" S by employing the observation that when a mismatch occurs, the word itself embodies sufficient information to determine where the next match could begin, thus bypassing re-examination of previously matched characters.

The algorithm was conceived by James H. Morris and independently discovered by Donald Knuth "a few weeks later" from automata theory. Morris and Vaughan Pratt published a technical report in 1970. The three also published the algorithm jointly in 1977. Independently, in 1969, Matiyasevich discovered a similar algorithm, coded by a two-dimensional Turing machine, while studying a string-pattern-matching recognition problem over a binary alphabet. This was the first linear-time algorithm for string matching.

🔗 Companies 🔗 Computing 🔗 United Kingdom

Andrews & Arnold Ltd (also known as AAISP) is an Internet service provider based in Bracknell in the United Kingdom founded in 1997 and launched in 1998, primarily serving businesses and "technical" home users.

In 2009 the company was judged the best niche provider in the Thinkbroadband Customer Service Awards, based on customer ratings and again in 2010.

The company's owner, Adrian Kennard (RevK), stated in a blog post that as of October 2010 the company is "xkcd/806" compliant, referring to xkcd comic number 806. This means that technical support callers who say the code word "shibboleet" will be transferred to a technical support representative who knows at least two programming languages, and presumably can offer more useful advice than a standard tech support script.

Andrews & Arnold provides IPv6 to all customers, for no additional charge.

Andrews & Arnold provides optional bonded multiple-link internet access. This allows multiple links to be used together to vastly increase speed and reliability. Special routers distribute individual IP packets between the available links in such a way that even one single download or upload operation will benefit fully from multiple speed, and it is not necessary to have several users, several running programs or computers to gain the speed benefit. Links can be of different types, each needs only to be a pipe that can carry IP packets. Multiple links can either be used together all the time, or some can be brought up as a back up if other links fail, so-called 'failover', or a combination of the two approaches can be set up.

Andrews & Arnold are strong advocates of not censoring Internet connections. Adrian Kennard has several blog posts discussing why Internet censorship as discussed in the UK is not workable, providing background for AAISP's decision.

🔗 Computing 🔗 Computing/Software

In software development, the yo-yo problem is an anti-pattern that occurs when a programmer has to read and understand a program whose inheritance graph is so long and complicated that the programmer has to keep flipping between many different class definitions in order to follow the control flow of the program. It often happens in object-oriented programming. The term comes from comparing the bouncing attention of the programmer to the up-down movement of a toy yo-yo. Taenzer, Ganti, and Podar described the problem by name, explaining: "Often we get the feeling of riding a yoyo when we try to understand one of these message trees."

Most practices of object-oriented programming recommend keeping the inheritance graph as shallow as possible, in part to avoid this problem. The use of composition instead of inheritance is also strongly preferred, although this still requires that a programmer keep multiple class definitions in mind at once.

More generally, the yo-yo problem can also refer to any situation where a person must keep flipping between different sources of information in order to understand a concept.

Object-oriented design techniques such as documenting layers of the inheritance hierarchy can reduce the effect of this problem, as they collect in one place the information that the programmer is required to understand.

🔗 Biography 🔗 Military history 🔗 Military history/Military biography 🔗 Military history/World War II

Sir Basil Zaharoff, GCB, GBE, born Vasileios Zacharias (Greek: Βασίλειος Zαχαρίας Ζαχάρωφ; October 6, 1849 – November 27, 1936), was a Greek arms dealer and industrialist. One of the richest men in the world during his lifetime, Zaharoff was described as a "merchant of death" and "mystery man of Europe". His success was forged through his cunning, often aggressive and sharp, business tactics. These included the sale of arms to opposing sides in conflicts, sometimes delivering fake or faulty machinery and skilfully using the press to attack business rivals.

Zaharoff maintained close contacts with many powerful political leaders, including British Prime Minister David Lloyd George, Greek Prime Minister Eleftherios Venizelos and Ottoman Sultan Abdul Hamid II; he served as a primary inspiration for Ian Fleming's fictional James Bond villain Ernst Stavro Blofeld.

🔗 Physics 🔗 Systems 🔗 Systems/Chaos theory

In condensed matter physics, Hofstadter's butterfly describes the spectral properties of non-interacting two dimensional electrons in a magnetic field. The fractal, self-similar, nature of the spectrum was discovered in the 1976 Ph.D. work of Douglas Hofstadter and is one of the early examples of computer graphics. The name reflects the visual resemblance of the figure on the right to a swarm of butterflies flying to infinity.

The Hofstadter butterfly plays an important role in the theory of the integer quantum Hall effect, and D.J. Thouless has been awarded the Nobel prize in physics in 2016 for the discovery that the wings of the butterfly are characterized by Chern integers, the quantized Hall conductances discovered in 1980 by Klaus von Klitzing for which he has been awarded the Nobel prize in 1985. The colors in the diagram reflect the different Chern numbers.

🔗 Biography 🔗 Bangladesh 🔗 Architecture 🔗 Skyscrapers 🔗 Civil engineering 🔗 Chicago 🔗 Illinois

Fazlur Rahman Khan (Bengali: ফজলুর রহমান খান, Fozlur Rôhman Khan) (3 April 1929 – 27 March 1982) was a Bangladeshi-American structural engineer and architect, who initiated important structural systems for skyscrapers. Considered the "father of tubular designs" for high-rises, Khan was also a pioneer in computer-aided design (CAD). He was the structural engineer of the Sears Tower working with Architect Bruce Graham, since renamed Willis Tower, the tallest building in the world from 1973 until 1998, and the 100-story John Hancock Center.

Khan, more than any other individual, ushered in a renaissance in skyscraper construction during the second half of the 20th century. He has been called the "Einstein of structural engineering" and the "Greatest Structural Engineer of the 20th Century" for his innovative use of structural systems that remain fundamental to modern skyscraper design and construction. In his honor, the Council on Tall Buildings and Urban Habitat established the Fazlur Khan Lifetime Achievement Medal, as one of their CTBUH Skyscraper Awards.

Although best known for skyscrapers, Khan was also an active designer of other kinds of structures, including the Hajj airport terminal, the McMath–Pierce solar telescope, and several stadium structures.

🔗 Spaceflight 🔗 Physics 🔗 Science Fiction

A black hole starship is a theoretical idea for enabling interstellar travel by propelling a starship by using a black hole as the energy source. The concept was first discussed in science fiction, notably in the book Imperial Earth by Arthur C. Clarke, and in the work of Charles Sheffield, in which energy extracted from a Kerr-Newman black hole is described as powering the rocket engines in the story "Killing Vector" (1978).

In a more detailed analysis, a proposal to create an artificial black hole and using a parabolic reflector to reflect its Hawking radiation was discussed in 2009 by Louis Crane and Shawn Westmoreland. Their conclusion was that it was on the edge of possibility, but that quantum gravity effects that are presently unknown will either make it easier, or make it impossible. Similar concepts were also sketched out by Bolonkin.