One of the most rare and mysterious forms of lightning is ball lightning. It is a ball of luminosity that usually occurs near the impact point of a flash and moves horizontally at a speed of a few centimeters per second. It can penetrate closed windows, is usually accompanied by a hissing sound and has a life time of several seconds. The colour is quiet variable and the ball often ends with an explosion-however, it is not usually destructive. Also called as globe lightning, it occurs at times of intense electrical activity in the atmosphere. These balls are said to be plasmas. (Plasma is a completely ionized state of mater, at high temperature, in which positive and negative Ions freely move about.). However, no theory has so far satisfactorily explained the behavior of a ball as scientists have not been able to reproduce it in the laboratory. Lightning ball is comparatively rare sight and so next time you see it, take a picture.
Clouds are masses of tiny water droplets and ice crystals that float in the air. As such they do not have any colour. But some look white and some grey.
Some change shape continuously as parts of the cloud evaporate when they come into contact with the warmer air.
Clouds are classified mainly by their appearance dimension, shape, structure and texture. While stratus clouds are sheet-like, fair weather cumulus clouds consists of piled-up masses of dazzlingly white clouds. They are made of water droplets. Cirrus clouds are curly white made of ice crystals at higher altitudes. In these clouds, water droplets or ice crystals are loosely packed and so light can pass through them without much loss in intensity.
Some of the clouds which cause rain are the stratus and stratocumulus clouds which are near-earth clouds. Stratocumulus clouds are not as thick as stratus clouds and so they have light and dark areas.
Altrostratus clouds form smooth white or grey sheets across the sky. Sometimes these clouds are so thick that the Sun or the Moon cannot be seen through it. At times the difference in thickness may cause relatively light patches between dark parts but the surface of the clouds do not show any relief.
Nimbostratus is low, amorphous and occurs at higher altitudes. These are dark, grey and uniform. Cumulonimbus is the main rain clouds which are black. This is because light cannot penetrate through them as they are deep and densely packed with water droplets, ice and snow particles.
If we look from an aircraft, flying at high altitudes, these clouds will look dazzlingly white, as they reflect all the light falling on them. But for an observer on the ground the clouds may look black and be raining. Clouds are thus white and black at the same time!
