if something is a source of something else then that something else comes from that something
else is river. change is when_one_thing_becomes_another_thing. source_materials is source. else is not river. space is what_between_else. space is not what_between_else. directions_to_get_somewhere is not how_to_thing. source_materials is not source. change is not when_one_thing_becomes_another_thing. thing is substance.