Cloud

In meteorology, a cloud is an aerosol comprising a visible mass of liquid droplets or frozen crystals made of water or various chemicals. The droplets or particles are suspended in the atmosphere above the surface of a planetary body. On Earth clouds are formed by the saturation of air in the homosphere when air cools or gains water vapor.

Cloud types in the troposphere, the atmospheric layer closest to Earth's surface, have Latin names due to the universal adaptation of Luke Howard's nomenclature. It was formally proposed in December 1802 and published for the first time the following year. It became the basis of a modern international system that classifies these tropospheric aerosols into several physical forms which can be found at various altitude levels or étages.

Repoussé and chasing

Repoussé or repoussage (French pronunciation: [ʁəpuse]; [ʁəpusaʒ] respectively) is a metalworking technique in which a malleable metal is ornamented or shaped by hammering from the reverse side to create a design in low relief.

There are few techniques that offer such diversity of expression while still being relatively economical. Chasing is the opposite technique to repoussé, and the two are used in conjunction to create a finished piece. It is also known as embossing.

While repoussé is used to work on the reverse of the metal to form a raised design on the front, chasing is used to refine the design on the front of the work by sinking the metal. The term chasing is derived from the noun "chase", which refers to a groove, furrow, channel or indentation. The adjectival form is "chased work".

The techniques of repoussé and chasing utilise the plasticity of metal, forming shapes by degrees. There is no loss of metal in the process, as it is stretched locally and the surface remains continuous. The process is relatively slow, but a maximum of form is achieved, with one continuous surface of sheet metal of essentially the same thickness. Direct contact of the tools used is usually visible in the result, a condition not always apparent in other techniques, where all evidence of the working method is eliminated.

Moon

The Moon (in Greek: σελήνη Selene, in Latin: Luna) is Earth's only natural satellite. It is one of the largest natural satellites in the Solar System, and, among planetary satellites, the largest relative to the size of the planet it orbits (its primary). It is the second-densest satellite among those whose densities are known (after Jupiter's satellite Io).

The Moon is thought to have formed approximately 4.5 billion years ago, not long after Earth. There are several hypotheses for its origin; the most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia.

The Moon is in synchronous rotation with Earth, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters. It is the second-brightest regularly visible celestial object in Earth's sky after the Sun, as measured by illuminance on Earth's surface. Although it can appear a very bright white, its surface is actually dark, with a reflectance just slightly higher than that of worn asphalt. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence on language, calendars, art, and mythology.

Unknown

Unknown or The Unknown may refer to:

Mathematics

Film

Music

Other uses