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The parsec is a unit of length used to measure the large distances to astronomical objects outside the Solar System. A parsec is obtained by the use of parallax and trigonometry, is defined as the distance at which one astronomical unit subtends an angle of one arcsecond, i.e. 1/3600th of a degree. This corresponds to 648000/π astronomical units. One parsec is equal to 31 trillion kilometres or 19 trillion miles, equates to about 3.26 light-years. The nearest star, Proxima Centauri, is about 1.3 parsecs from the Sun. Most of the stars visible to the unaided eye in the night sky are within 500 parsecs of the Sun; the parsec unit was first suggested in 1913 by the British astronomer Herbert Hall Turner. Named as a portmanteau of the parallax of one arcsecond, it was defined to make calculations of astronomical distances from only their raw observational data quick and easy for astronomers. For this reason, it is the unit preferred in astronomy and astrophysics, though the light-year remains prominent in popular science texts and common usage.

Although parsecs are used for the shorter distances within the Milky Way, multiples of parsecs are required for the larger scales in the universe, including kiloparsecs for the more distant objects within and around the Milky Way, megaparsecs for mid-distance galaxies, gigaparsecs for many quasars and the most distant galaxies. In August 2015, the International Astronomical Union passed Resolution B2, which, as part of the definition of a standardized absolute and apparent bolometric magnitude scale, mentioned an existing explicit definition of the parsec as 648000/π astronomical units, or 3.08567758149137×1016 metres. This corresponds to the small-angle definition of the parsec found in many contemporary astronomical references; the parsec is defined as being equal to the length of the longer leg of an elongated imaginary right triangle in space. The two dimensions on which this triangle is based are its shorter leg, of length one astronomical unit, the subtended angle of the vertex opposite that leg, measuring one arc second.

Applying the rules of trigonometry to these two values, the unit length of the other leg of the triangle can be derived. One of the oldest methods used by astronomers to calculate the distance to a star is to record the difference in angle between two measurements of the position of the star in the sky; the first measurement is taken from the Earth on one side of the Sun, the second is taken half a year when the Earth is on the opposite side of the Sun. The distance between the two positions of the Earth when the two measurements were taken is twice the distance between the Earth and the Sun; the difference in angle between the two measurements is twice the parallax angle, formed by lines from the Sun and Earth to the star at the distant vertex. The distance to the star could be calculated using trigonometry; the first successful published direct measurements of an object at interstellar distances were undertaken by German astronomer Friedrich Wilhelm Bessel in 1838, who used this approach to calculate the 3.5-parsec distance of 61 Cygni.

The parallax of a star is defined as half of the angular distance that a star appears to move relative to the celestial sphere as Earth orbits the Sun. Equivalently, it is the subtended angle, from that star's perspective, of the semimajor axis of the Earth's orbit; the star, the Sun and the Earth form the corners of an imaginary right triangle in space: the right angle is the corner at the Sun, the corner at the star is the parallax angle. The length of the opposite side to the parallax angle is the distance from the Earth to the Sun, the length of the adjacent side gives the distance from the sun to the star. Therefore, given a measurement of the parallax angle, along with the rules of trigonometry, the distance from the Sun to the star can be found. A parsec is defined as the length of the side adjacent to the vertex occupied by a star whose parallax angle is one arcsecond; the use of the parsec as a unit of distance follows from Bessel's method, because the distance in parsecs can be computed as the reciprocal of the parallax angle in arcseconds.

No trigonometric functions are required in this relationship because the small angles involved mean that the approximate solution of the skinny triangle can be applied. Though it may have been used before, the term parsec was first mentioned in an astronomical publication in 1913. Astronomer Royal Frank Watson Dyson expressed his concern for the need of a name for that unit of distance, he proposed the name astron, but mentioned that Carl Charlier had suggested siriometer and Herbert Hall Turner had proposed parsec. It was Turner's proposal. By 2015 definition, 1 Astronomical unit of arc length subtends an angle of 1 arc second at the center of the circle of radius 1 parsec. Converting from degree/minute/second units to radian unit, 1 pc 1 au = 180 × 60 × 60 π, 1 au = 149 597 870 700 m {\displaystyle 1=149\,597\,870\,700{\mbo

Prism paralleloscope

A prism paralleloscope is a piece kit used by artillery units as a gun aiming point. It is a type of paralleloscope, its purpose was to function as an aiming point in the horizontal plane when laying for indirect fire artillery. The prism paralleloscope entered service with the British Army in the late 1950s, it was permanently fitted in a fibre-glass case with a lid. This case was mounted on two short metal vertical poles so that it was about two feet above the ground, these vertical poles were held together by two horizontal rods shorter that the paralleloscope case. Once mounted the lid of the case provided a'canopy' above the paralleloscope. Paralleloscopes entered British service in the 1920s-30s; these early versions were a mirror about three feet long and 4 inches wide, mounted on a tripod about three feet high and positioned a few yards away from and to the side of a gun on its dial sight side. Each gun in a battery had at least one; when a gun was oriented in its centre of arc it recorded the paralleloscope as one of its aiming points.

With a paralleloscope the gun layer set the zero line deflection or bearing of fire on his dial sight and aimed his sight at its reflection in the paralleloscope. As the gun fire and its trail bedded in and the gun moved back, the reflected image of the sight moved along the paralleloscope, it was useful at night because it removed the need for aiming points with lights attached to them. If the gun had a wide arc of fire more than one paralleloscope was required for each gun

Overtone flute

An overtone flute is a type of a flute, designed to play in the upper harmonics well above the two or three harmonics that are the practical limit for most woodwind instruments. An overtone flute has either no tone holes, or few tone holes for a woodwind instrument. To make melodies, one plays it high into the overtone series. One series of harmonics is achieved by overblowing with the end of the tube open and another is achieved with the end closed; this means. Overtone flute tubes have a long resonating chamber compared to their inner diameter or cross sectional area, which encourages the instrument to resonate in the higher harmonics. An overtone flute in the key of G, with an inner diameter of 1", will require more effort to play higher harmonics than an overtone flute in the same key, with an inner diameter of 1/2". For example, a ratio of 1: 30 - Inner Diameter: Length allows for high harmonics to be played with little effort. Kalyuka - Russian and Ukrainian overtone flute. Traditionally, the Kalyuka was constructed from the Borshevik branch.

Because of the fragile nature of the branch, the instrument was played seasonally. Tylynka/ Tilinkó /Tilinca - Ukrainian/Hutsul and Romanian overtone flute. Willow flute - Scandinavian flute Fujara - a Slovak flute. Known as the "Shepherd's Flute", the Fujara was developed over many years by shepherds in Slovakia and Poland; the Fujara incorporates. There are three playing holes, the full scale is played by overblowing from the 4th of the scale, to the 5th. Koncovka - Slovak Overtone flute with a fipple; the Koncovka is similar to the Kalyuka. The Koncovka is constructed with a fipple. Choctaw overtone flute Natural trumpet, brass overtone instrument

Milton Marks

Milton Marks, Jr. was a California politician who served in the California State Assembly and California State Senate, as both a Republican and a Democrat, representing San Francisco for 38 years. Born in San Francisco, Marks attended the city's Alamo Grammar School and Galileo High School, where he participated in the Junior Reserve Officers' Training Corps. After graduating from Galileo as valedictorian of the class of 1937, Marks went on to earn an A. B. from Stanford University in 1941, where he had been part of the Army Reserve Officers' Training Corps. Marks went on to the UC Berkeley School of Law and was studying with a friend, future federal judge Milton Lewis Schwartz, at International House Berkeley during the attack on Pearl Harbor. Less than a month after the attack, Marks reported to Fort Ord as a Second Lieutenant in the United States Army. Serving in the Pacific Theater of Operations, including the Philippines Campaign, he was the Assistant Defense Counsel for the Court of the Eighth United States Army during the Occupation of Japan.

After completing his Army service as a Major, Marks returned to the UC Berkeley Law School but transferred, graduating from San Francisco Law School in 1949. Marks first ran unsuccessfully for the State Assembly in 1954 as a Republican, he was elected in 1958 as a Republican to the Assembly, serving until 1966, when he was named a city judge. When a vacancy occurred in a State Senate seat in 1967, he ran in and won the special election as a Republican, defeating Democrat Assemblyman John L. Burton, the younger brother of powerful Democratic Congressman Phil Burton, head of the San Francisco political machine. While still a Republican, Marks made an unsuccessful run for Congress in 1982 to unseat Phil Burton, losing by a margin of 58%-40%. Burton died unexpectedly of an aneurysm five months after the election at the age of 56 and was succeeded by Sala Burton, who would serve in the seat until her death less than four years when she was succeeded by Nancy Pelosi, a longtime Burton family friend.

He served in the Senate as a Republican until 1988. He won his last Senate term as a Democrat in 1992. Marks and his wife, had three children: the late Milton Marks III, who served as a board member of City College of San Francisco, Caro Marks, a Federal Defender in Sacramento, Edward David Marks, an attorney practicing in the Bay Area

John Taylor (Medal of Honor)

John Taylor was a United States Navy sailor and a recipient of the U. S. military's highest decoration, the Medal of Honor. Taylor served in the U. S. Navy as a seaman stationed at the Brooklyn Navy Yard in New York. On September 9, 1865, he was in charge of the Navy Yard's picket boat as it patrolled the East River with the yard's executive officer, Commander Stephen Decatur Trenchard, on board; when a ferry boat and an English steamer collided, Trenchard ordered Taylor to pull their boat alongside the stricken ferry to render assistance. As Trenchard attempted to step onto the ferry, he fell into the water. Taylor showed "rare coolness and judgment" as he rescued the officer. For this action, he was awarded the Medal of Honor four months on January 15, 1866. Taylor's official Medal of Honor citation reads: Seaman in charge of the picket boat attached to the Navy Yard, New York, 9 September 1865. Acting with promptness and good judgment, Taylor rescued from drowning Commander S. D. Trenchard, of the U.

S. Navy, who fell overboard in attempting to get on a ferryboat, which had collided with an English steamer, needed immediate assistance. List of Medal of Honor recipients during peacetime

Minneapolis Armory

The Minneapolis Armory is an 8,400-person capacity music and events venue located in downtown Minneapolis, United States. The Armory was built for the Minnesota National Guard in 1935–36 and used by the Minneapolis Lakers of the NBA from 1947-1960, it was listed on the National Register of Historic Places in 1985. In 2015, the Armory was purchased by a local development firm for $6 million; the building was converted from a parking facility to an 8,400-capacity events center and concert venue. It reopened in January 2018 in time to host several events related to Super Bowl LII; the armory was the costliest single building in Minnesota supported by a Public Works Administration grant. The building is an example of the PWA Moderne style, a design characterized by strong geometry, bold contouring and integrated sculpture ornamentation; the building was designed by St. Paul architect P. C. Bettenburg, a major in the Minnesota National Guard. St. Paul artist Elsa Jemne painted murals in the building. From the late 1930s through the 1970s, it was a venue for civic events, including concerts, political conventions and sporting events such as Golden Gloves tournaments.

The building was used by the Minneapolis Lakers of the National Basketball Association as a part-time home between 1947–1959, as its primary home court for the 1959–60 NBA season. The National Guard ceased operations at the armory in 1980. Hennepin County bought the armory in 1989 for $4.7 million, with plans to place a new county jail on the site. The Minnesota Historical Society sued to stop its destruction and in 1993, the Minnesota Supreme Court ruled that the structure was protected by state law and could not be torn down because of its historical status. In 1998, the county sold the building for $2.6 million to a private company for use as a parking structure on condition that it be preserved. Minneapolis native Prince used the building to shoot the music video for "1999" in 1982. 16 years Aerosmith recorded the video for their song "I Don't Want to Miss a Thing" in the armory. List of Registered Historic Places in Minnesota Media related to Minneapolis Armory at Wikimedia CommonsOfficial website