Thursday, August 16, 2012
 Del Tintero - Longitude
Realmente no tenia un tema para escribir hoy, hasta que comenzaron a preguntar por unidades que estan en desuso. Hablamos entonces de la unidad de nudos para medir la velocidad de las embarcaciones. La descripcion aqui:
Until the mid-19th century vessel speed at sea was measured using a chip log. This consisted of a wooden panel, weighted on one edge to float upright, and thus present substantial resistance to moving with respect to the water around it, attached by line to a reel. The chip log was "cast" over the stern of the moving vessel and the line allowed to pay out. Knots placed at a distance of 47 feet 3 inches (14.4018 m) passed through a sailor's fingers, while another sailor used a 30 second sand-glass (28 second sand-glass is the current accepted timing) to time the operation. The knot count would be reported and used in the sailing master's dead reckoning and navigation. This method gives a value for the knot of 20.25 in/s, or 1.85166 km/h. The difference from the modern definition is less than 0.02%
La velocidad era clave en la navegacion porque el metodo de localizar la embarcacion en el mar consistia en predecir apropiadamente la ruta. El Estimado o 'Dead Reckoning' utilizaba datos de la velocidad de la embarcacion y el tiempo para estimar la posicion. Mas aqui:
Dead reckoning, using best estimates of speed and direction, is subject to cumulative errors. Advances in navigational aids which give accurate information on position, in particular satellite navigation using the Global Positioning System, has made simple dead reckoning by humans obsolete for most purposes; however, inertial navigation systems, which provide very accurate directional information, use dead reckoning and are very widely applied.
Esto lo escribi hace casi dos a/nos atras...
Desviando de los temas politicos y ambientalistas de los ultimos posts decidi discutir de esta interesante serie que vi hace unos a/nos atras, donde se discute de como el progreso de la tecnologia fue clave para el desarrollo de la navegacion moderna. Tener relojes precisos y buena medicion de la velocidad era clave para no quedarse a la deriva.
La historia moderna indica que los metodos de navegacion existentes de principios del siglo 18 eran increiblemente imprecisos y causaban retrasos y naufragios innecesarios. Inglaterra tenia la necesidad de dominar los mares y convoca a una competencia con un premio significativo (20,000 libras esterlinas) para el que pudiese idear una tecnologia de navegacion lo suficientemente precisa y compacta para ser usada en las fragatas de la era.
El siguiente articulo da una buena introduccion a la novelizacion del tema en el libro Longitude.
Errors in navigation have also resulted in shipwrecks. Motivated by a number of maritime disasters attributable to serious errors in reckoning position at sea, particularly spectacular disasters such as the Scilly naval disaster of 1707 which took Admiral Sir Cloudesley Shovell and his fleet, the British government established the Board of Longitude in 1714.
"The Discovery of the Longitude is of such Consequence to Great Britain for the safety of the Navy and Merchant Ships as well as for the improvement of Trade that for want thereof many Ships have been retarded in their voyages, and many lost..." and announced the Longitude Prize "for such person or persons as shall discover the Longitude."The prizes were to be awarded to the first person to demonstrate a practical method for determining the longitude of a ship at sea. Each prize, in increasing amounts, were for solutions of increasing accuracy. These prizes, worth millions of dollars in today's currency, motivated many to search for a solution.
Britain was not alone in the desire to solve the problem. France's King Louis XIV founded the Académie Royale des Sciences in 1666. It was charged with, among a range of scientific activities, the improvement of maps and sailing charts and advancement of the science of navigation. From 1715, the Académie offered one of the two Prix Rouillés specifically for navigation. Spain's Philip II offered a prize for the discovery of a solution to the problem of the longitude in 1567; Philip III increased the prize in 1598. Holland added to the effort with a prize offered in 1636. Navigators and scientists in most European countries were aware of the problem and were involved in finding the solution. Due to the international effort in solving the problem and the scale of the enterprise, it represents one of the largest scientific endeavours in history.
Interesante por demas como la precision de medir el tiempo se hizo necesario para navegar.
Mas aun, que los polinesios sean excelentes navegantes sin necesidad de tanta precision...http://en.wikipedia.org/wiki/Polynesian_navigation
A 2007 study published in the Proceedings of the National Academy of Sciences of chicken bones at El Arenal near the Arauco Peninsula, Arauco Province, Chile suggested Oceania-to-America contact. Chickens originated in southern Asia and the Araucana breed of Chile was thought to have been brought by Spaniards around 1500. However, the bones found in Chile were radiocarbon-dated to between 1304 and 1424, well before the documented arrival of the Spanish. DNA sequences taken were exact matches to those of chickens from the same period in American Samoa and Tonga, both over 5000 miles (8000 kilometers) away from Chile. The genetic sequences were also similar to those found in Hawaiʻi and Easter Island, the closest island at only 2500 miles (4000 kilometers), and unlike any breed of European chicken. Although this initial report suggested a Polynesian pre-Columbian origin a later report looking at the same specimens concluded:
A published, apparently pre-Columbian, Chilean specimen and six pre-European Polynesian specimens also cluster with the same European/Indian subcontinental/Southeast Asian sequences, providing no support for a Polynesian introduction of chickens to South America. In contrast, sequences from two archaeological sites on Easter Island group with an uncommon haplogroup from Indonesia, Japan, and China and may represent a genetic signature of an early Polynesian dispersal. Modeling of the potential marine carbon contribution to the Chilean archaeological specimen casts further doubt on claims for pre-Columbian chickens, and definitive proof will require further analyses of ancient DNA sequences and radiocarbon and stable isotope data from archaeological excavations within both Chile and Polynesia. In the last 20 years, the dates and anatomical features of human remains found in Mexico and South America have led some archaeologists to propose that those regions were first populated by people who crossed the Pacific several millennia before the Ice Age migrations; according to this theory, these Pre-Siberian American Aborigines would have been either eliminated or absorbed by the Siberian immigrants. However, current archaeological evidence for human migration to and settlement of remote Oceania (i.e., the Pacific Ocean eastwards of the Solomon Islands) is dated to no earlier than approximately 3,500 BP; trans-Pacific contact with the Americas coinciding with or pre-dating the Beringia migrations of at least 11,500 BP is highly problematic, except for movement along intercoastal routes
Cierro aqui por hoy...