The calendrical systems devised and used by the pre-Columbian cultures of Mesoamerica, primarily a 260-day year, were used in religious observances and social rituals, such as divination. These calendars have been dated to early as ca. 1100 BCE. By 500 BCE at the latest, the essentials were fully defined and functional. 260-day calendars are still used in the Guatemalan highlands, Veracruz, Oaxaca and Chiapas, Mexico.The importance of aboriginal calendars in ritual and other aspects of Mesoamerican life was noted by many missionary priests, travelers, and colonial administrators, and later by ethnographers who described and recorded the cultures of contemporary Mesoamerican ethnic groups. Types of calendars Among the various calendar systems in use, two were particularly central and widespread across Mesoamerica. Common to all recorded Mesoamerican cultures, and the most important, was the 260-day calendar, a ritual calendar with no confirmed correlation to astronomical or agricultural cycles. Apparently the earliest Mesoamerican calendar to be developed was known by a variety of local...

In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable attenuation rates. Hearing protectors help reduce acoustic flux from flowing into the ears. This phenomenon is called acoustic attenuation and is measured in decibels (dBs). In electrical engineering and telecommunications, attenuation affects the propagation of waves and signals in electrical circuits, in optical fibers, and in air. Electrical attenuators and optical attenuators are commonly manufactured components in this field. Background In many cases, attenuation is an exponential function of the path length through the medium. In optics and in chemical spectroscopy, this is known as the Beer–Lambert law. In engineering, attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/km, etc.) and is represented by the attenuation coefficient of the medium in question. Attenuation also occurs in earthquakes; when the seismic waves move...

The Wind River Range (or "Winds" for short) is a mountain range of the Rocky Mountains in western Wyoming in the United States. The range runs roughly NW–SE for approximately 100 mi (160 km). The Continental Divide follows the crest of the range and includes Gannett Peak, which at 13,802 ft (4,207 m), is the highest peak in Wyoming; and also Fremont Peak at 13,750 ft (4,191 m), the third highest peak in Wyoming. There are more than 40 other named peaks in excess of 12,999 ft (3,962 m). With the exception of the Grand Teton in the Teton Range, the next 19 highest peaks in Wyoming after Gannett are also in the Winds.Two large national forests including three wilderness areas encompass most of the mountain range. Shoshone National Forest is on the eastern side of the continental divide while Bridger-Teton National Forest is on the west. Both national forests and the entire mountain range are an integral part of the Greater Yellowstone Ecosystem. Portions of the east side of the range are inside the Wind River Indian Reservation. History Indigenous peoples of the Great Basin, such as the Shoshones...