Archive for the ‘Optics’ Category

Navigation

October 25, 2010 - 9:40 pm 326 Comments

Navigation

Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. The word navigate is derived from the Latin “navigate”, which is the command “sail”.[1] More literally however, the word “Navi” in Sanskrit means ‘boat’ and “Gathi” means ‘direction’.
Celestial navigation, also known as astronavigation, is a position fixing technique that has steadily evolved over several thousand years to help sailors cross featureless oceans without having to rely on estimated calculations, or dead reckoning, to enable them to know their position on the ocean. Celestial navigation uses “sights,” or angular measurements taken between a visible celestial body (the sun, the moon, a planet or a star) and the visible horizon. The angle measured between the sun and the visible horizon is most commonly used. Skilled navigators can additionally use the moon, a planet or one of 57 navigational stars whose coordinates are tabulated in the Nautical Almanac and Air Almanacs.

Celestial navigation is the process whereby angular measurements (sights) taken between celestial bodies in the sky and the visible horizon are used to locate one’s position on the globe, on land as well as at sea. At any given instant of time, any celestial body is located directly over only one specific geographic point, or position on the Earth, whose address is described by latitude and longitude.

Would not have been invented without:

Astronomy
Optics

Astronomy

October 25, 2010 - 7:05 pm 342 Comments

Astronomy

Astronomy (Greek: αστρονομία = άστρον νόμος, astronomia = astron nomos, literally “law of the stars”) is a natural science that deals with the study of celestial objects (such as stars, planets, comets, nebulae, star clusters and galaxies) and phenomena that originate outside the Earth’s atmosphere (such as the cosmic background radiation). It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe.

Astronomy is one of the oldest sciences. Prehistoric cultures left behind astronomical artifacts such as the Egyptian monuments and Stonehenge, and early civilizations such as the Babylonians, Greeks, Chinese, Indians, and Maya performed methodical observations of the night sky. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, and even astrology, but professional astronomy is nowadays often considered to be synonymous with astrophysics.

Early astronomy involved observing the regular patterns of the motions of visible celestial objects, especially the Sun, Moon, stars and naked eye planets. Study of the changing position of the Sun along the horizon or the changing appearances of stars in the course of the year could be used to establish an agricultural or ritual calendar. In some cultures astronomical data was used for astrological prognostication.

Would not have been invented without:

Optics

Compass

October 25, 2010 - 6:34 pm 301 Comments

compass
The compass was invented in ancient China around 247 B.C., and was used for navigation by the 11th century. Chinese fortune tellers used lodestones (a mineral composed of an iron oxide which aligns itself in a north-south direction) to construct their fortune telling boards.

Eventually someone noticed that the lodestones were better at pointing out real directions, leading to the first compasses. They designed the compass on a square slab which had markings for the cardinal points and the constellations. The pointing needle was a lodestone spoon-shaped device, with a handle that would always point south.A compass is a navigational instrument for determining direction relative to the Earth’s magnetic poles. It consists of a magnetized pointer (usually marked on the North end) free to align itself with Earth’s magnetic field. The compass greatly improved the safety and efficiency of travel, especially ocean travel. A compass can be used to calculate heading, used with a sextant to calculate latitude, and with a marine chronometer to calculate longitude. It thus provides a much improved navigational capability that has only been recently supplanted by modern devices such as the Global Positioning System (GPS). A compass is any magnetically sensitive device capable of indicating the direction of the magnetic north of a planet’s magnetosphere. The face of the compass generally highlights the cardinal points of north, south, east and west. Often, compasses are built as a stand alone sealed instrument with a magnetized bar or needle turning freely upon a pivot, or moving in a fluid, thus able to point in a northerly and southerly direction.

Wouldn’t have been invented without:
Magnetism
China
Aristotle

Optics

October 25, 2010 - 6:22 pm 280 Comments

Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit identical properties.

Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation.