History Channel ® : In 1954, a young Princeton university doctoral candidate named Hugh Everett III came up with a radical idea: That there exist parallel universes, exactly like our universe. These universes are all related to ours; indeed, they branch off from ours, and our universe is branched off of others. Within these parallel universes, our wars have had diferent outcomes than the ones we know. Species that are extinct in our universe have evolved and adapted in others. In other universes, we humans may have become extinct.
A rocky alien planet called Gliese 581d may be the first known world beyond Earth capable of supporting life as we know it, a new study suggests.
Astronomers performing a new atmospheric-modeling study have found that the planet likely lies in the "habitable zone" of its host star — that just-right range of distances that allow liquid water to exist. The alien world could be Earth-like in key ways, harboring oceans, clouds and rainfall, according to the research.