Cloud physics vertically developed clouds, the cumulonimbus type is the tallest and can virtually span the entire troposphere from a few hundred metres above the ground up to the tropopause. It is the cloud responsible for thunderstorms. Some cirriform clouds can form at very high to extreme levels above the troposphere, mostly above the polar regions of Earth. Polar stratospheric clouds clouds are seen but rarely in winter at altitudes of 18 to 30 kilometers, while in summer, noctilucent clouds occasionally form at high latitudes at an altitude range of 76 to 85 kilometers. Homospheric types determined by cross-classification of forms and
The Cloud of Unknowing short word rather than a long one. A one-syllable word such as "God" or "love" is best. But choose one that is meaningful to you. Then fix it in your mind so that it will remain there come what may. This word will be your defence in conflict and in peace. Use it to beat upon the cloud of darkness above you and to subdue all distractions, consigning them to the "cloud of forgetting" beneath you. Editions of related texts include The Cloud of Unknowing The Cloud of Unknowing (Middle English: "The Cloude of Unknowyng") is an anonymous work of