Anytime you see something by Brian Greene, consider reading it. For example, this column that appeared in today's New York Times about the dark energy speeding the expansion of the universe. His gift for vivid example may be unparalleled. If I have a complaint about Greene's writing, it's that he doesn't expand his horizons sufficiently to "what it all means" quite often enough. However, in this column he does, a bit: he points out that it looks like the universe is not just unimaginably vast, it's speeding apart at an increasing rate. He asks what it would be like to be a few billion years later in the history of the universe, looking up into a dark sky with a few stars left and having to trust the records of previous scientists to know what the stars used to say about the origin and composition of the universe.
(As a side note, I'd like to point out, then we are alive at a very special point at which we've been allowed to observe the history -- something to be grateful for at least!)
I want to take that and ask, what does the expansion of the universe mean for the exploration of the universe? We already know it would take decades, traveling at near-light speeds, to reach the nearest star, and there appears to be no way to reach another galaxy constrained as we are by metabolism to the time scale of years. Reading the lights in the sky is one thing, but setting foot on another planet outside our system is quite another. Greene's point about dark energy expands this loneliness: even if we could develop something unimaginably fast, the universe may soon be expanding so fast we can't outrun it!
So the point is, there may be other planets out there, and other humanoids. But does it matter if we can never know them? Does it matter if we can't communicate, and can never, ever meet? Is this the Creator's intent, if He made myriads of worlds but keeps them each separate so they cannot touch? And does this moot all the questions about E.T. and alien salvation and other late-night dorm-room excursions?
Are we effectively unique? And if so, what does that mean to a science that seems to want to diminish the uniqueness of man with all its conclusions? To me, the accelerating universe means that, perhaps, in this limited sense, Copernicus was wrong: we are at the center of our universe after all.
There may be exceptions to this, and stranger things than we can imagine beyond the speed of light, but if we know what there is to know, this is what Greene's argument brings me to. Man is the measure, a little lower than the angels. Thus sayeth the Greene.