It ' s a somewhat arbitrary definition . You just take a population native to a defined territory and call them an ethnic group . NorwegianAmericans are not native to the US but they can be proven to be part of this previously defined population that is native to today ' s Norwegian territory . That ' s still possible if this arbitrary population is very diverse itself ethnic Germans have Germanic , Celtic and Romance ancestry , all mixed together and very different in the various parts of Germany . <| sep |> As long as we win . we ' re down <| sep |> Water exists on earth due to the specific temperature and pressure . Elsewhere it may freeze , sublimate into space , or become water vapor . High energy radiation can also detach the hydrogen atoms from the oxygen and the water will escape in the form if hydrogen gas and oxygen . Also , water is very heavy and would cost insane amounts of money and time just to move even small amounts distances to the moon and mars .