Raven

A raven is one of several larger-bodied members of the genus Corvus. These species do not form a single taxonomic group within the genus, but share similar characteristics and appearances that generally separate them from other crows. The largest raven species are the common raven and the thick-billed raven.

Etymology

The term "raven" originally referred to the common raven, the type species of the genus Corvus, which has a larger distribution than any other species of Corvus, ranging over much of the Northern Hemisphere.

The modern English word raven has cognates in all other Germanic languages, including Old Norse (and subsequently modern Icelandic) hrafn and Old High German (h)raban, all of which descend from Proto-Germanic *khrabanaz.

Obsolete collective nouns for a group of ravens (or at least the common raven) include "unkindness" and "conspiracy". In practice, most people use the more generic "flock".

Species

Energy

In physics, energy is a property of objects which can be transferred to other objects or converted into different forms, but cannot be created or destroyed. The "ability of a system to perform work" is a common description, but it is difficult to give one single comprehensive definition of energy because of its many forms. For instance, in SI units, energy is measured in joules, and one joule is defined "mechanically", being the energy transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton. However, there are many other definitions of energy, depending on the context, such as thermal energy, radiant energy, electromagnetic, nuclear, etc., where definitions are derived that are the most convenient.

Common energy forms include the kinetic energy of a moving object, the potential energy stored by an object's position in a force field (gravitational, electric or magnetic), the elastic energy stored by stretching solid objects, the chemical energy released when a fuel burns, the radiant energy carried by light, and the thermal energy due to an object's temperature. All of the many forms of energy are convertible to other kinds of energy, and obey the law of conservation of energy which says that energy can be neither created nor be destroyed; however, it can change from one form to another.

Catch Me

Catch Me may refer to:

Summer solstice

The summer solstice occurs when the tilt of a planet's semi-axis, in either northern or southern hemispheres, is most inclined toward the star that it orbits. Earth's maximum axial tilt toward the Sun is 23° 26'. This happens twice each year (once in each hemisphere), at which times the Sun reaches its highest position in the sky as seen from the north or the south pole.

The summer solstice occurs during a hemisphere's summer. This is the northern solstice in the northern hemisphere and the southern solstice in the southern hemisphere. Depending on the shift of the calendar, the summer solstice occurs some time between June 20 and June 22 in the northern hemisphere and between December 20 and December 23 each year in the southern hemisphere. The same dates in the opposite hemisphere are referred to as the winter solstice.

When on a geographic pole, the Sun reaches its greatest height, the moment of solstice, it can be noon only along that longitude which at that moment lies in the direction of the Sun from the pole. For other longitudes, it is not noon. Noon has either passed or has yet to come. Hence the notion of a solstice day is useful. The term is colloquially used like midsummer to refer to the day on which solstice occurs. The summer solstice day has the longest period of daylight – except in the polar regions, where daylight is continuous, from a few days to six months around the summer solstice.

Full moon

A full moon is the lunar phase that occurs when the Moon is completely illuminated as seen from the Earth. This occurs when the moon is in opposition to the Sun (when it is on the opposite side of the Earth from the Sun; more precisely, when the ecliptic longitudes of the Sun and Moon differ by 180 degrees). This means that the hemisphere of the Moon that is facing the Earth (the near side) is almost fully illuminated by the Sun and appears round (while the far side is almost completely unilluminated).

Lunar eclipses can occur only at full moon, where the Moon's orbit allows it to pass through the Earth's shadow. Lunar eclipses do not occur every month because the Moon usually passes above or below the Earth's shadow (which is mostly restricted to the ecliptic plane). Lunar eclipses can occur only when the full moon occurs near the two nodes of the orbit, either the ascending or descending node. This causes eclipses to only occur about every 6 months, and often 2 weeks before or after a solar eclipse at new moon at the opposite node.