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.
Planet Earth is a dense, rocky ball about 7,920 miles (12,750 km) across. It is one of nine planets circling our local star, the Sun. Earth is the only planet we know of that can support life. From space, its surface looks blue and cool, but inside it is so hot that rock can melt.