posted on Sep, 19 2009 @ 02:44 AM
You try to put all categories of crafts in one big basket. Each civilization have it's own technology which means different way of changing state
from one place to another. The biological crafts need to replace what it consumes, more advanced ones doesn't, they can exist in any state forever if
The biological crafts uses a special liquid to replenish itself but is not wasteful, it can carry enough liquid to keep functional for long time.
One common fact (a misconception) is the observation of crafts as are all the same. At this time more than 2 dozens different people visit Earth in
collaboration and for specific purposes.