.....visually we wouldn't know it was there? Say for instance a life form exists that is hundreds, thousands, if not millions of times bigger than what we see as the known universe. Now I said visually so there may be other ways to detect such a thing but I think you would first have to start looking for it. Not sure if anybody has ever tried to accomplish such a task. Also do not know how humans relate size wise to the smallest of microbes or whether or not a microbe can tell where it actually is, but if it was adrift in the middle of an ocean and could see then would it be able to assess its position in its universe (ocean)?