The impeller made out of cast material in many cases may be called rotor, also. It is cheaper to cast the radial impeller right in the support it is fitted on, which is put in motion by the gearbox from an electric motor, combustion engine or by steam driven turbine.
Earth remains the only known planet to host life, due to a unique combination of factors. However, continued monitoring of alien worlds might one day change that, by finding other planets that share these attributes or by discovering other ways that life has found to blossom in the universe.
Life on Earth will continue for at least another 1.75 billion years ... but human life could die out long before. Astrobiologists predict our planet will move out of the solar system's habitable zone and become too hot for even primitive bacteria. To survive, humans might have to migrate to Mars. The calculations were based on our distance from the sun and temperatures at which it is possible for the planet to retain water.