When something wakes me from a dream, sometimes in describing the dream at that point I'll say "I don't know what happened next". By saying that, I'm kind of assuming that the dream is a separate entity that continues regardless of my involvement in it -- as if it's in one room and I walked out of that room when I woke up.

Is that the case? I don't really believe it is... the dream is an artifact created by my involvement. When I cease to percieve it, it ceases to exist. However, this style of thinking can be disturbing and lead to all sorts of sophomoric pseudophilosophical arguments. What does this apply to? If I die, does the universe cease to exist? Some people would argue that it wouldn't, because there are other sentient (does the observer have to be sentient?) beings (i.e. the rest of the human race (is the human race sentient? is a single human sentient? or just the entire race as a whole? what about a termite versus a termite colony? what about jello?)) still observing the universe.

But what if there was no life in the universe? Would the universe cease to exist? I guess that depends on what definition is used for 'existance'. Would the universe would become a formless blob without an observer to collapse the probability waveform? Science fiction writers like to think so, but it's not in fact the case, according to Real Physicists.