I've never seen green lightning.
I have seen a green phenomenon of ionisation in the winter night sky, aurora borealis - otherwise called the northern lights.
When I saw them, they were like shimmering curtains of green light and lasted much longer than lightning. Over the half hour, their intensity fluctuated, but they were always visible.
Different colours in the sky are one of the lovliest displays of nature. They are nothing to be fearful of. Just enjoy them!
2006-12-27 04:40:21
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answer #1
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answered by rosie recipe 7
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Some atoms will make colors when excited. In gas excitations it is specific atoms, present as a vapor or a gas, which have their electrons raised into higher energy levels by a variety of excitations; light is then emitted when the excess energy is released as photons. (This is in contrast to incandescence which can occur when any substance is heated.) Examples include electrical excitations as in arcs, sparks, lightning, neon tubes, and sodium and mercury-vapor lamps; chemical excitation as in the chemists' flame test for sodium and a few other elements (also utilized in pyrotechnic devices); and high-energy particles as in the northern and southern auroral displays. An unusual occurrence is found in triboluminescence, as when we crunch a wintergreen "lifesaver" in front of a mirror in the dark. The high-voltage field produced during the formation of new electrically-charged sugar crystal surfaces accelerates electrons which excite nitrogen-gas molecules to produce the ion N2+ which has a blue luminescence; some ultraviolet is also produced and causes the oil of wintergreen (methyl salicylate) to fluoresce with a particularly intense blue-light production.
Above right, lightning dances across the charged skies over Sydney Harbour and the Harbour Bridge. The bridge is lit with vapor lamps, and the lightning is also an electrical excitation.
Sodium- and mercury-vapor lamps efficiently emit yellow and bright blue, respectively, and are often used in parking lots, where they distort the color of our autos. The mercury also produces much ultraviolet light; in fluorescent-tube lamps this is converted by a phosphor coating into lower-energy yellow, orange, and red light to produce a better color balance for indoor lighting. Gas lasers, as in the helium-neon laser, use gas excitations with optical feedback from mirrors at each end of the tube to produce coherent light, in which all the light waves have almost the same frequency and are coherent, that is, in step, both in space and in time.
Some of the possible energy levels for a gaseous sodium atom are shown in the diagram above. A high voltage, as in a sodium vapor lamp, produces ionization from the initial "ground state" into Na+ plus one electron at the top line of this figure. As the electron recombines the system passes along transitions, only a few of which are shown as arrows, with the emission of radiation. The position of the various levels shown, as well as the specific transitions which the system can follow, are explained by quantum theory; all paths are constrained by the "selection rules" to terminate in the lowest two arrows, which correspond to the emission of the bright-yellow sodium "doublet" lines at 589.7 and 589.0 nm.
A high intensity mercury vapor lamp is really a tube within a tube. The smaller tube contains Mercury vapor and is the source of light. In 1937, this was the type of lamp used to light working areas in the Douglas Aircraft Company plant in Long Beach, California.
Vapor lamps were a major advance because they are more energy efficient.
Computing terms
Apparently random flashing streaks on the face of 3278-9 terminals while a new symbol set is being downloaded. This hardware bug was left deliberately unfixed, as some genius within IBM suggested it would let the user know that "something is happening". That, it certainly does. Later microprocessor-driven IBM colour graphics displays were actually *programmed* to produce green lightning!
2006-12-27 08:00:23
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answer #2
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answered by Anonymous
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