Literally, in order for a vortex to be classified as a tornado, it must be in contact with the ground and the cloud base. Weather scientists haven't found it so simple in practice, however, to classify and define tornadoes (per this essay by Doswell).
Bikini Island, 2015. Credit: Emlyn Hughes. (Phys.org)âA team of researchers from Columbia University in New York has found that all of the Marshall Islands involved in nuclear tests by the U.S. are now habitable, except for Bikini Atoll.
A new definition of the habitable zone around planets, denoting where liquid water could exist, shifts Earth toward the very edge of the solar system's own habitable zone. Credit: PHL @ UPR Arecibo, Rogelio Bernal Andreo View full size image. One of the most important characteristics of an alien planet is whether or not it falls into what's called the habitable zone Â­â a Goldilocks-like range of not-too-close, not-too-far distances from the parent star that might allow the planet to host life.