Sun Shadows Research Articles

First observation of the cosmic ray shadow of the Moon and the Sun with KM3NeT/ORCA

This article reports the first observation of the Moon and the Sun shadows in the sky distribution of cosmic-ray induced muons measured by the KM3NeT/ORCA detector. The analysed data-taking period spans from February 2020 to November 2021, when the detector had 6 Detection Units deployed at the bottom of the Mediterranean Sea, each composed of 18 Digital Optical Modules. The shadows induced by the Moon and the Sun were detected at their nominal position with a statistical significance of 4.2sigma and 6.2sigma , and an angular resolution of sigma _{res}=0.49^circ and sigma _{res}=0.66^circ , respectively, consistent with the prediction of 0.53^circ from simulations. This early result confirms the effectiveness of the detector calibration, in time, position and orientation and the accuracy of the event direction reconstruction. This also demonstrates the performance and the competitiveness of the detector in terms of pointing accuracy and angular resolution.

Detection of the Temporal Variation of the Sun's Cosmic Ray Shadow with the IceCube Detector

Abstract We report on the observation of a deficit in the cosmic ray flux from the directions of the Moon and Sun with five years of data taken by the IceCube Neutrino Observatory. Between 2010 May and 2011 May the IceCube detector operated with 79 strings deployed in the glacial ice at the South Pole, and with 86 strings between 2011 May and 2015 May. A binned analysis is used to measure the relative deficit and significance of the cosmic ray shadows. Both the cosmic ray Moon and Sun shadows are detected with high statistical significance (>10σ) for each year. The results for the Moon shadow are consistent with previous analyses and verify the stability of the IceCube detector over time. This work represents the first observation of the Sun shadow with the IceCube detector. We show that the cosmic ray shadow of the Sun varies with time. These results make it possible to study cosmic ray transport near the Sun with future data from IceCube.

Observation of the Cosmic-Ray Shadow of the Moon and Sun with IceCube

Abstract. Moon shadow analyses are standard methods to calibrate cosmic-ray detectors. We report on a three-year observation of cosmic-ray Moon and Sun shadows in different detector configurations. The cosmic-ray Moon shadow was observed with high statistical significance (> 6σ) in previous analyses when the IceCube detector operated in a smaller configuration before it was completed in December 2010. This work shows first analyses of the cosmic-ray Sun shadow in IceCube. A binned analysis in one-dimension is used to measure the Moon and Sun shadow with high statistical significance greater than 12σ.

Del análisis y la representación de situaciones espaciales hacia el pensamiento teórico en geometría: una ruta de tercero a noveno grado

A partir de ejemplos provenientes de un proyecto que inició a finales de los años 1970, y que ha sido ampliamente experimentado en la escuela primaria y los primeros cursos de secundaria, me propongo ilustrar cómo es posible moverse desde la construcción argumentativa de conceptos geométricos en campos de experiencia adecuados (en particular, en el campo de experiencia de las sombras solares) hacia el desarrollo de las competencias argumentativas necesarias para validar conjeturas en geometría y para aproximarse a teoremas de la geometría tridimensional. La producción y validación argumentativa de hipótesis relacionadas con ciertos fenómenos y situaciones espaciales proveen oportunidades a los estudiantes tanto para desarrollar la conceptualización en el campo de la geometría como para tener un acercamiento al razonamiento hipotético (“si… entonces…”), al encadenamiento deductivo de proposiciones, etcétera. La mayoría de los ejemplos tienen que ver con situaciones tridimensionales de sombras producidas por el sol.

The influence of external landmarks, the sun, and cast shadows on learning a wormhole environment

The influence of external landmarks, the sun, and cast shadows on learning a wormhole environment

Relationships between frequency of ground exposure and forest cover in a mangrove island ecosystem.

In mangrove forests, as in all intertidal systems the hydroperiod is of great importance to the vitality of mangrove forests. Despite the importance of inundation and drying periods in tidal ecosystems, spatially-explicit measurements of frequency of ground exposure to air (the drying period) and its effect on mangrove forest cover have rarely been quantified. An eight-month long study was conducted of the tidal regime along a main channel in an overwashed island mangrove forest off the coast of Belize, Central America. Cumulative frequency distribution of tidal data were integrated within a geographic information system to model the spatial extent of ground exposure, and forest cover was estimated using the normalized difference vegetation index (NDVI). Empirical relationships between forest cover and exposure were quantified along seven cross sections, and along 23 transects. On average, exposure accounted for 43% of the variance in NDVI along cross sections. Composite data results for 23 transects showed a positive linear response of NDVI to exposure along both right (R2 = 0.31) and left (R2 = 0.14) banks, with no response in the upper channel area. On average, exposure accounted for 33% of the variance in NDVI on the right bank, and for 13% of the variance on the left bank. At a local scale, NDVI highest responses in the right bank ranged from R2 = 0.44 to R2 = 0.71. Landscape variability in NDVI vs. ground exposure relationships may be due to confounding effects from interactions with other biological and physical variables such as: microbial mats, wind, sun shadows, spatial heterogeneity in topography, rainfall, canopy structure, root density and distribution.

Vehicles Recognition by Video Camera

The paper presents the recognition of vehicles considered as obstacles in the road, in order to avoid collision. An inboard video camera is used as an optical sensor to supply exterior scene information. The algorithm of vehicle detection from video image, built by morphological transformations (Serra 1982), is proposed. The advantage of the proposed approach is the reliable recognition for various models and colors of vehicle, and the good efficiency for difficult case like distant vehicles and lateral sun shadows. The experimentation has been done on a large amount of data. Some of results is given in the article.

Visualizing the United States in Computer Chiaroscuro

HE modern computer has imparted new power and meaning to the old axiom One picture is worth a thousand words (Davies et al. 1990). Machine visualization-the art, science, and technology of seeing via computer graphics-has developed the means to view the unviewable: natural events and processes invisible to the unaided eye because they are too abstract, complex, fast, remote, small, or large (Friedhoff and Benzon 1991). Earth's topography is an apt example of the last restriction. Customary methods for viewing the landscape do not simultaneously provide broad coverage and accurate detail. The Earth's surface cannot be seen at 1:1 scale in its entirety and all at once, but just in many small areas visited sequentially in the field-clearly too great a task even over the lifetime of an individual. Spatial continuity and context can only be obtained at greatly reduced scales: on contour maps and aerial photographs, on radar images, or at even smaller scales on satellite images. Computer graphics overcomes these problems and offers a fresh look at the Earth's landform patterns by mechanizing an old approach: relief representation (Brassel et al. 1974). The well-known technique of shading, or chiaroscuro, developed by Renaissance painters, shows topographic form by intensity of the Sun's shadows (Imhof 1965). Because manual (artistic) methods can economically portray only small areas both accurately and in detail, Yoeli (1967) adapted a quantitative variant of the technique, termed analytical hillshading, for digital execution. Large areas have been mapped by mechanized shading, but until recently spatial resolution has remained low (e.g., Moore and Simpson 1982). Our digital relief map of the entire conterminous US (Fig. 1), which shows features as small as a mile across, is one of the first images to combine detail with synoptic coverage (for a Swedish example, see Elvhage and Lidmar-Bergstrdm 1987). The machine-shaded maps shown here resemble cloudless aerial photographs, but actually are large arrays of minute gray rectangles (nominally squares). Each rectangle, or picture element (pixel), represents a reflectance (brightness) value of the topography computed from a mathematical expression called the photometric function. This equation, which has many variants, relates (1) ground slope and azimuth, (2) location of the observer (here, overhead), and (3) position of a simulated Sun (here, from the west-northwest at 250 above the horizon) (Yoeli 1967; Batson et al. 1975). Light and dark tones on the resulting image show steep areas; intermediate tones are gentle terrain. The data from which the maps are created are dense square-grid matrices of terrain

Seasonal Variation in Succinylcholine Immobilization of Captive White-Tailed Deer

Seasonal Variation in Succinylcholine Immobilization of Captive White-Tailed Deer

An 8th-century meridian line: I-Hsing's chain of gnomons and the pre-history of the metric system

A study is here made of one of the most remarkable pieces of organized field research in the early middle ages — the meridian survey directed by a Buddhist monk I-Hsing and an official astronomer Nankung Yüeh in +725. At a central chain of four stations in Eastern China, at measured distances apart, covering some 200 km., observations were systematically made. It is believed that these consisted of the measurement of solstitial and equinoctial Sun shadows and of polar altitudes. The observations were also carried out at a chain of five further stations, about 2500 km in length in all, from Indo-China to the southern border of Mongolia. A single northernmost station in the vicinity of Lake Baikal had also been the scene of similar observations, thus making it possible to consider an arc of no less than 3800 km. length. The ratio of terrestrial distance units ( li) to the degree, which it was one of the objects of the survey to ascertain, fixed a civil unit in a manner prefiguring the metric system of a thousand years later. The fact that I-Hsing, Nankung Yüeh and their colleagues accepted this ratio as a constant may imply that some of them envisaged the Earth's sphericity—a view in harmony with some of the ancient schools of Chinese cosmology, but not generally accepted by scholars in their time. The li which these astronomers desired to express in terms of the degree appears to have been one of the two usual distance units of the period, namely the “normal short Thang li”. A surprising result is that I-Hsing appears to have had remarkably accurate trigonometric tables at his disposal. The paper concludes with a study of the astronomical standardization of the li by Antoine Thomas S.J. in 1702 at the request of the Khang-Hsi emperor, nearly a century before the similar standardization of the metre in Europe.