Mechanical computer
From Wikipedia, the free encyclopedia
A mechanical computer is built from mechanical components such as levers and gears, rather than electronic components. The most common examples are adding machines and mechanical counters, which use the turning of gears to increment output displays. More complex examples can carry out multiplication and division, and even differential analysis.
Mechanical computers reached their zenith during World War II, when they formed the basis of complex bombsights including the Norden, as well as the similar devices for ship computations such as the US Torpedo Data Computer or British Admiralty Fire Control Table. In the post-war era, most complex examples were quickly replaced by electronic versions, an evolution that culminated in the 1970s with the introduction of inexpensive handheld electronic calculators.
Noteworthy are mechanical flight instruments for early spacecraft, which provided their computed output not in the form of digits, but through the displacements of indicator surfaces. From Yuri Gagarin's first manned spaceflight until 2002, every manned Soviet and Russian spacecraft Vostok,Voskhod and Soyuz was equipped with a Globus instrument showing the apparent movement of the Earth under the spacecraft through the displacement of a miniature terrestrial globe, plus latitude and longitude indicators.
[edit]Examples
- The Antikythera mechanism, ca. 150 BC
- Stepped Reckoner, 1672 - Gottfried Wilhelm Leibniz's mechanical calculator that could add, subtract, multiply, and divide.
- Difference Engine, 1822 – Charles Babbage's mechanical device to calculate polynomials.
- Analytical Engine, 1837 – A later Charles Babbage device that could be said to encapsulate most of the elements of modern computers.
- Kerrison Predictor ("late 1930s" ?)
- Curta calculator, 1948
- Moniac, 1949 – An analog computer used to model or simulate the UK economy.
- Voskhod Spacecraft "Globus" IMP navigation instrument, early 1960s
- Automaton - Mechanical devices that, in some cases, can store data and perform calculations, and perform other complicated tasks.
Documentary hypothesis
From Wikipedia, the free encyclopedia
"JEPD" redirects here. JEPD may also refer to Jointly Exhaustive, Pairwise Disjoint.
The documentary hypothesis, (DH) (sometimes called the Wellhausen hypothesis), proposes that the Pentateuch (the first five books of the Bible) was derived from originally independent, parallel and complete narratives, which were subsequently combined into the current form by a series of redactors (editors). The number of these is usually set at four, but this is not an essential part of the hypothesis.
The hypothesis was developed in the 18th and 19th centuries from the attempt to reconcile inconsistencies in the biblical text. By the end of the 19th century it was generally agreed that there were four main sources, combined into their final form by a series of redactors, R. These four sources came to be known as the Yahwist, or Jahwist, J (J being the German equivalent of the English letter Y); the Elohist, E; theDeuteronomist, D, (the name comes from the Book of Deuteronomy, D's contribution to the Torah); and the Priestly Writer, P.[1]
Julius Wellhausen's contribution was to order these sources chronologically as JEDP, giving them a coherent setting in the evolving religious history of Israel, which he saw as one of ever-increasing priestly power. Wellhausen's formulation was:
- the Yahwist source ( J ) : written c. 950 BC in the southern Kingdom of Judah.
- the Elohist source ( E ) : written c. 850 BC in the northern Kingdom of Israel.
- the Deuteronomist ( D ) : written c. 600 BC in Jerusalem during a period of religious reform.
- the Priestly source ( P ) : written c. 500 BC by Kohanim (Jewish priests) in exile in Babylon.
While the hypothesis has been increasingly challenged by other models in the last part of the 20th century, its terminology and insights continue to provide the framework for modern theories on the origins of the Torah.[2]
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