A vacuum tube also called a electron tubes is a sealed glass or metal-ceramic enclosure used in electronic circuitry to control the flow of electrons between the metal electrodes sealed inside the tubes. The air inside the tubes is removed by a vacuum. Vacuum tubes are used for: amplification of a weak current, rectification of an alternating current to direct current (AC to DC), generation of oscillating r ...

* 5th-4th Centuries B.C. Chinese and Greek philosophers describe the basic principles of optics and the camera. * 1664-1666 Isaac Newton discovers that white light is composed of different colors. * 1727 Johann Heinrich Schulze discovered that silver nitrate darkened upon exposure to light. * 1794 First Panorama opens, the forerunner of the movie house invented by Robert Barker. * 1814 Joseph Niepce achieve ...

A battery, which is actually an electric cell, is a device that produces electricity from a chemical reaction. Strictly speaking, a battery consists of two or more cells connected in series or parallel, but the term is generally used for a single cell. A cell consists of a negative electrode; an electrolyte, which conducts ions; a separator, also an ion conductor; and a positive electrode. Timeline of Batte ...

The First Man-Made Plastic - Parkesine The first man-made plastic was created by Alexander Parkes who publicly demonstrated it at the 1862 Great International Exhibition in London. The material called Parkesine was an organic material derived from cellulose that once heated could be molded, and retained its shape when cooled. Celluloid Celluloid is derived from cellulose and alcoholized camphor. John Wesley ...

00 B.C. Thales of Miletus writes about amber becoming charged by rubbing - he was describing what we now call static electricity. 1600 English scientist, William Gilbert first coined the term "electricity" from the Greek word for amber. Gilbert wrote about the electrification of many substances in his "De magnete, magneticisique corporibus". He also first used the terms electric force, magnetic pole, and el ...

1945 Isidor Rabi, a physics professor at Columbia University, suggests a clock could be made from a technique he developed in the 1930's called atomic beam magnetic resonance. 1949 Using Rabi’s technique, NIST (then the National Bureau of Standards) announces the world’s first atomic clock using the ammonia molecule as the source of vibrations. 1952 NIST announces the first atomic clock using cesium atoms a ...

Thus spake Zarathustra: 6th century BC Zoroaster (the Greek name by which the Iranian prophet Zarathustra has become known) is traditionally believed to have lived and taught in the early part of the 6th century BC. His home is probably in the region to the east of the Caspian Sea. The main theme of Zoroaster's teaching is to replace the numerous ahuras or gods of the traditional Indo-Iranian religion with ...

Mapungubwe and Great Zimbabwe: 11th - 15th c. AD The plateau between the rivers Zambezi and Limpopo, in southeast Africa, offers rich opportunities for human settlement. Its grasslands make excellent grazing for cattle. The tusks of dead elephants provide an easy basis for a trade in ivory. A seam of gold, running along the highest ridge, shows signs of having been worked in at least four places before 1000 ...

A Portuguese interlude: 16th - 17th century AD The small tropical island of Zanzibar, a mere twenty miles off the east coast of Africa, has played a part in local history out of all proportion to its size. The reason is its easy access to traders and adventurers exploring down the east coast of Africa from Arabia. Islam is well established in this region by the 11th century. During the 16th century there is ...

Barotse and Kololo: 19th century AD The African tribes living in the region between the Zambezi and Lake Tanganyika are first reached by outsiders in 1798. In that year a Portuguese trading party, pushing north from Tete on the Zambezi, reaches the capital of a chief near Lake Mweru. Half a century later this is the region which Livingstone explores, from his journey down the Zambezi in 1855 to his death ne ...