jueves, 24 de julio de 2014
http://www.facebook.com/l.php?u=http%3A%2F%2Fwww.fisicarecreativa.com%2Ftaller%2Fguias%2Fcap_12_Astronomia.pdf&h=lAQEN7kHj
RESUMEN DE LA LECTURA
Aristarco ideó un ingenioso método para medir el tamaño de la Luna y su distancia a la Tierra comparando el tamaño de la sombra de la Tierra con el de la Luna durante un eclipse lunar
Proyecto II.30.- Determinación del tamaño de la Luna y su distancia a la Tierra -
Aristarco
Usando la técnica descripta más arriba, Figura 12.1, determine la relación entre el tamaño
(diámetro) de la sombra de la Tierra y la Luna.
Determine el mejor valor de α, ángulo subtendido por la Luna.
Del análisis de una (o más) foto de un eclipse de Luna, y los valores de α y RT que se proveen, estime
el tamaño de la Luna, RL, y su distancia a la Tierra, dTL. Para esta primera parte puede suponer que el
tamaño de la sombra de la Tierra es igual al de la Tierra, o sea: RT ≈RT’.(Ver Fig. 12.2).
A partir del análisis de la foto del eclipse, Fig. 12.1, determine el mejor valor del cociente: k = R’T/RL y
estime su incertidumbre. Usando el esquema geométrico ilustrado en la Figura 12.2, demuestre que:
RT R T dTL = ' +α ⋅ . (12.4)
Radio Terrestre
Equipamiento recomendado: Una mira telescópica, con retículo en forma de cruz montado sobre un
trípode. Una regla milimetrada de unos 40 cm de largo. Un nivel o una manguera de plástico transparente
con agua. Acceso a una loma o edificio de al menos 25 o 30 m de altura, con vista al mar
Método de Hiparco
Equipamiento recomendado: Obtenga datos de eclipses reales similares a los indicados en la Fig. 12.8,
que se pueden encontrar en la página de internet de la NASA.1
Proyecto II.33.- Distancia Tierra-Sol
Aristarco de Samos no solo estimó el tamaño de la Luna, sino que además ideó un ingenioso esquema
para medir la distancia al Sol. En la Fig. 12.9 se representa la posición de la Luna en dos fases
Usando los datos de la Tabla 12.1, grafique la duración del año planetario, Tp, en
función de su distancia al Sol, dS. Usando escalas lineales y logarítmicas, describa la
dependencia de Tp con dS.
COMENTARIO:
Me interesó que hubo una recreación de métodos geométricos clásicos con la ayuda de la tecnología que ha incrementado herramientas para estimar distancias astronómicas a partir de observaciones simples mediante técnicas y el uso de imágenes digitalizadas de eclipses disponibles en el internet. y comparaban el tamaño de la sombra de la Tierra con el de la luna durante el eclipse para así hacer posible su medición.
martes, 8 de julio de 2014
http://eclipse.gsfc.nasa.gov/OH/OH2014.html#LE2014Apr15T
ECLIPSE TOTAL DE LUNA DEL 08 DE OCTUBRE
The second lunar eclipse of 2014 is also total and is best seen from the Pacific Ocean and bordering regions. The eclipse occurs at the Moon's descending node in southern Pisces, two days after perigee (October 06 at 09:41 UT). This means that the Moon will appear 5.3% larger than it did during the April 15 eclipse (32.7 vs. 31.3 arc-minutes).
This time the orbital path of the Moon takes it through the northern half of Earth's umbral shadow. The total phase lasts 59 minutes primarily because the diameter of the umbral shadow is larger (1.49° verses 1.39°). The lunar path through Earth's shadows as well as a map illustrating worldwide visibility of the event are shown in Figure 3. The times of the major eclipse phases are listed below.
Penumbral Eclipse Begins: 08:15:33 UT
Partial Eclipse Begins: 09:14:48 UT
Total Eclipse Begins: 10:25:10 UT
Greatest Eclipse: 10:54:36 UT
Total Eclipse Ends: 11:24:00 UT
Partial Eclipse Ends: 12:34:21 UT
Penumbral Eclipse Ends: 13:33:43 UT
At the instant of greatest eclipse (10:54:36 UT) the Moon lies near the zenith from a location in the Pacific Ocean about 2000 km southwest of Hawaii. At this time, the umbral magnitude peaks at 1.1659 as the Moon's southern limb passes 6.6 arc-minutes north of the shadow's central axis. In contrast, the Moon's northern limb lies 5.4 arc-minutes from the northern edge of the umbra and 39.3 arc-minutes from the shadow centre. As a result, the southern half of the Moon will appear much darker than the northern half because it lies deeper in the umbra. The Moon samples a large range of umbral depths during totality so its appearance will change considerably with time. The exact brightness distribution in the umbra is difficult to predict, so observers are encouraged to estimate the Danjon value at different times during totality (see Danjon Scale of Lunar Eclipse Brightness). It may also be necessary to assign different Danjon values to different portions of the Moon (e.g., north vs. south).
During totality, the autumn constellations are well placed for viewing and the brighter stars can be used for magnitude comparisons. The center of the Great Square of Pegasus lies 15° to the northwest, its brightest star being Alpheratz (m = +2.02). Deneb Kaitos (m = +2.04) in Cetus is 30° south of the eclipsed Moon, while Hamal (m = +2.01) is 25° to the northeast, Aldebaran (m = +0.87) is 56° to the east, and Almach (m = +2.17) is 40° to the north.
Although relatively faint, the planet Uranus (m = +5.7) lies just 2/3° southeast of the Moon during totality. Is a transit of the Earth and Moon across the Sun's disk visible from Uranus during the eclipse? An interesting idea but calculations show a miss. From Uranus, the Sun's disk is only 1.7 arc-minutes in diameter and this is a very small target to hit. Nevertheless, transits of Earth from Uranus are possible - the next one takes place on 2024 November 17 (Meeus, 1989).
The entire October 08 eclipse is visible from the Pacific Ocean and regions immediately bordering it. The northwestern 1/3 of North America also witnesses all stages. Farther east, various phases occur after moonset. For instance, the Moon sets during totality from eastern Canada and the USA. Observers in South America also experience moonset during the early stages of the eclipse. All phases are visible from New Zealand and eastern 1/4 of Australia - the Moon rises during the early partial phases from Australia's west coast. Most of Japan and easternmost Asia catch the entire eclipse as well. Farther west in Asia, various stages of the eclipse occur before moonrise. None of the eclipse is visible from Europe, Africa, and the Middle East.
Table 3 lists predicted umbral immersion and emersion times for 25 well-defined lunar craters. The timing of craters is useful in determining the atmospheric enlargement of Earth's shadow (see Crater Timings During Lunar Eclipses).
The October 08 eclipse is the 42nd eclipse of Saros 127. This series is composed of 72 lunar eclipses in the following sequence: 11 penumbral, 18 partial, 16 total, 20 partial, and 7 penumbral eclipses (Espenak and Meeus, 2009). The family began with the penumbral eclipse of 1275 July 09, and ends with another penumbral eclipse on 2555 September 02.
COMENTARIO:
Me pareció novedoso que se ve mejor desde el Océano pacífico y las regiones limítrofes.
aparecerá un 5,3% mayor de lo que apareció durante el eclipse del 15 de abril. Su fase dura en totalidad 59 minutos y que se puede usar la visualización de las constelaciones otoñales durante la totalidad para comparaciones de magnitud.
The second lunar eclipse of 2014 is also total and is best seen from the Pacific Ocean and bordering regions. The eclipse occurs at the Moon's descending node in southern Pisces, two days after perigee (October 06 at 09:41 UT). This means that the Moon will appear 5.3% larger than it did during the April 15 eclipse (32.7 vs. 31.3 arc-minutes).
This time the orbital path of the Moon takes it through the northern half of Earth's umbral shadow. The total phase lasts 59 minutes primarily because the diameter of the umbral shadow is larger (1.49° verses 1.39°). The lunar path through Earth's shadows as well as a map illustrating worldwide visibility of the event are shown in Figure 3. The times of the major eclipse phases are listed below.
Penumbral Eclipse Begins: 08:15:33 UT
Partial Eclipse Begins: 09:14:48 UT
Total Eclipse Begins: 10:25:10 UT
Greatest Eclipse: 10:54:36 UT
Total Eclipse Ends: 11:24:00 UT
Partial Eclipse Ends: 12:34:21 UT
Penumbral Eclipse Ends: 13:33:43 UT
At the instant of greatest eclipse (10:54:36 UT) the Moon lies near the zenith from a location in the Pacific Ocean about 2000 km southwest of Hawaii. At this time, the umbral magnitude peaks at 1.1659 as the Moon's southern limb passes 6.6 arc-minutes north of the shadow's central axis. In contrast, the Moon's northern limb lies 5.4 arc-minutes from the northern edge of the umbra and 39.3 arc-minutes from the shadow centre. As a result, the southern half of the Moon will appear much darker than the northern half because it lies deeper in the umbra. The Moon samples a large range of umbral depths during totality so its appearance will change considerably with time. The exact brightness distribution in the umbra is difficult to predict, so observers are encouraged to estimate the Danjon value at different times during totality (see Danjon Scale of Lunar Eclipse Brightness). It may also be necessary to assign different Danjon values to different portions of the Moon (e.g., north vs. south).
During totality, the autumn constellations are well placed for viewing and the brighter stars can be used for magnitude comparisons. The center of the Great Square of Pegasus lies 15° to the northwest, its brightest star being Alpheratz (m = +2.02). Deneb Kaitos (m = +2.04) in Cetus is 30° south of the eclipsed Moon, while Hamal (m = +2.01) is 25° to the northeast, Aldebaran (m = +0.87) is 56° to the east, and Almach (m = +2.17) is 40° to the north.
Although relatively faint, the planet Uranus (m = +5.7) lies just 2/3° southeast of the Moon during totality. Is a transit of the Earth and Moon across the Sun's disk visible from Uranus during the eclipse? An interesting idea but calculations show a miss. From Uranus, the Sun's disk is only 1.7 arc-minutes in diameter and this is a very small target to hit. Nevertheless, transits of Earth from Uranus are possible - the next one takes place on 2024 November 17 (Meeus, 1989).
The entire October 08 eclipse is visible from the Pacific Ocean and regions immediately bordering it. The northwestern 1/3 of North America also witnesses all stages. Farther east, various phases occur after moonset. For instance, the Moon sets during totality from eastern Canada and the USA. Observers in South America also experience moonset during the early stages of the eclipse. All phases are visible from New Zealand and eastern 1/4 of Australia - the Moon rises during the early partial phases from Australia's west coast. Most of Japan and easternmost Asia catch the entire eclipse as well. Farther west in Asia, various stages of the eclipse occur before moonrise. None of the eclipse is visible from Europe, Africa, and the Middle East.
Table 3 lists predicted umbral immersion and emersion times for 25 well-defined lunar craters. The timing of craters is useful in determining the atmospheric enlargement of Earth's shadow (see Crater Timings During Lunar Eclipses).
The October 08 eclipse is the 42nd eclipse of Saros 127. This series is composed of 72 lunar eclipses in the following sequence: 11 penumbral, 18 partial, 16 total, 20 partial, and 7 penumbral eclipses (Espenak and Meeus, 2009). The family began with the penumbral eclipse of 1275 July 09, and ends with another penumbral eclipse on 2555 September 02.
COMENTARIO:
Me pareció novedoso que se ve mejor desde el Océano pacífico y las regiones limítrofes.
aparecerá un 5,3% mayor de lo que apareció durante el eclipse del 15 de abril. Su fase dura en totalidad 59 minutos y que se puede usar la visualización de las constelaciones otoñales durante la totalidad para comparaciones de magnitud.
jueves, 3 de julio de 2014
http://decoracion.about.com/od/paredesypisos/a/Tipos-De-Pintura.htm
Tipos de pintura
Descubre la mejor para tu proyecto
By Lucia Mata
Una de las partes mas complicadas para principiantes a la hora de decidir pintar un mueble o pared, es que tipo de pintura usar. En tiendas de mejoras para el hogar puedes encontrar todo tipo de marcas, tipos y calidades de pintura, y la decisión de cual es a mejor para tu proyecto puede ser complicada. Tan importante como el color, es el tipo de pintura, ya que este tendrá diferentes resultados en distintas superficies, aparte de cada uno tener sus propios beneficios y desventajas.
Estos son los tipos mas comunes de pintura:
Pintura plástica
La pintura plástica o látex es la mas común en el uso de interiores. Su resina es sintética y el solvente es agua. Esta pintura es inodora y seca rápido, aparte de poder ser lavada fácilmente con agua. La pintura plástica viene en diferentes lustres y puede ser usada en casi cualquier superficie menos madera, ya que su base de agua puede dañarla.
Pintura sintética
La pintura sintética es mas durable, pero también seca mas lento y necesitara disolventes para limpiarse. Como la pintura plástica, esta viene en diferentes acabados, desde mate hasta brillante. La pintura sintética es generalmente usada en bordes y marcos, así como en baños y cocinas por su durabilidad. Esta pintura no debe ser usada sin pintura base, pero puede ser usada en madera.
Pintura base
La pintura base es usada para preparar una superficie antes de pintar. Esta pintura suaviza superficies, y ara que las otras capas se vean mejor. La pintura base es barata y seca rápido. Este tipo de pintura puede ser plástica, usada para concreto y paredes, o sintética, usada para madera.
Pintura acústica
Este tipo de pintura es usada para prevenir ruidos. La pintura acústica o anti-ruido es usada en baldosas o azulejos acústicos, y ayudara a mantener las cualidades de estas. Es generalmente usada en techos y su terminado es mate.
Pintura de clorocaucho
Este tipo de pintura tiene una base de caucho y cloro. Es resistente al agua y durable, por lo cual es usada en piscinas y concreto. La pintura de clorocaucho viene en colores limitados y en lustres mate o semi-mate.
comentario: Me llamo la atención la pintura que es para piso de una fábrica de alimentos ya que tiene una variedad de pasos a seguir y se tiene que realizar con cuidado para que no se dañe ya que si se realiza mal un paso se daña todo.
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