Maybe 3 or 4 years ago, I started developing a fear of flying. I never had a problem before then, but for some reason I started getting scared, especially when there's turbulence. My mother says it's because I became an atheist, but I don't buy that, because I've been a closet atheist for a while, well before my fear of flying. I know that flying is extremely safe, safer than driving, but that doesn't comfort me. I think my fear comes from the fact that if there is a crash, I have about a 0% chance of survival. At least in a car crash, I have a shot at survival. On a plane, there is nothing I can do. You just go down, and that's it.
But I have to fly, because it's the only practical way to travel long distances. I don't believe in any supernatural protectors, so I can't pray for safety or anything. So I need a way to get over my fear. It helps to have a couple drinks before getting on the plane, and sometimes that's enough, but usually, I get too in my head about it. It's too easy to imagine, when the plane hits a little turbulence, it just going down and not stopping. I know it's irrational, and I know that airplanes are incredibly well-engineered, designed to handle stresses well beyond those actually experienced during flight.
So, when I really need to console myself, I turn to an idea that comes from quantum mechanics (and pushes into philosophy a bit): the anthropic principle. It's a controversial idea that has several variations and different interpretations, but I'm mainly concerned with comforting myself on a plane, not fundamental scientific and philosophical issues.
Basically, the anthropic principle states that humans (or some observer) are the forcing factor that causes the universe to exist. In quantum mechanics, all possible outcomes of any situation coexist simultaneously, until something observes them and forces a single one to be chosen, according to a probability distribution. Schrodinger's cat is the classic macro analogy. The anthropic principle applies this theory on a universal scale (a source of controversy), and claims that the universe must exist in a state that allows something to observe it. Any possible universes which do not support some sort of observer within that universe cannot be observed, and therefore do not exist.
It's sort of like the proverbial tree falling in the forest, except I don't like Zen. Zen embraces contradiction and illogicality, which is great if it works for you, but all it does for me is piss me off. If a universe big bangs into existence and no one sees it, does it exist? The anthropic principle says no.
So, if no one is around to observe the universe, it doesn't exist. How does this help me on airplanes?
Well, I take another idea from philosophy to complete the picture. A fundamental question since ancient Greece has been "how do I know anything exists." It's an impossible question, one that requires some sort of assumption or leap of faith at some point (such as Descartes' famous "cogito ergo sum"). But at the end, I have no idea what truly exists. I don't know whether everything I observe, including other people, is real, or a figment of my imagination (I disagree with existentialism here... I'll buy that existence is fundamental for me, but can't see that it therefore must be so for everything else I observe). As far as I can tell, other people very well may not be real. I certainly have no way of proving that they are not.
So, I can suppose that I am the only real person in the universe. I am at least by far the most provably existing person in the universe. Under the anthropic principle, therefore, the universe exists because I am here to observe it. Not humanity in general, but me specifically, because I have no idea whether or not anyone else really exists. If I don't exist, neither does the universe, because I can't observe the universe.
Thus, if the plane goes down and crashes and I die, I will no longer be here to observe the universe, and it will not exist anymore. Poof! Gone. That would be quite an abrupt end to the universe. I comfort myself thinking how unlikely and catastrophic that would be. It would be a shame for all the wonderful complexities and amazing processes of the universe to just halt all of the sudden. I comfort myself knowing all this, and it gets me through flights.
It may sound conceited or vain or something, but from a purely scientific standpoint, factoring in what information I can truly know (that I exist), it is 100% correct (given that you accept the theories outlined above). I don't go around acting like I'm the center of the universe or anything. I just know in the back of my mind, that whenever I think I might die, that would mean the end of the universe (at least to me) because I won't be around to observe it anymore. I use that to help me not feel so scared, because the end of the universe is a big deal, big enough that I can convince myself I will be OK.
That's why I need to live an arbitrarily long time. To keep the universe going. That's where the singularity comes in, but that's another post.