But wait: There aren't just five galaxies here. There are hundreds of them. Only the round objects with X-shaped spikes are stars. Most of the other dots, streaks and smudges are distant galaxies.
This is, in a sense, a four-dimensional scene. With this two-dimensional image, we're looking at three-dimensional structures, but we're also looking back in time -- the fourth dimension. Each layer of the image represents a different epoch of cosmic history. We see the faintest galaxies as they were billions of years ago. "To me, it's like a geologist's core sample," astronomer Eric Chaisson of Tufts University says of the image.
Physicists will argue that we should not give any preferential status to what we call the "present." To a physicist, "now" is a subjective concept that just doesn't show up in the equations of nature. This defies common sense, of course, but no amount of protestation, arm-waving and spluttering will conjure from the physical laws any evidence that any one point in time exists differently than any other. "The way I'd like to think about it is, there's this big block," Brian Greene says. "Physicists call it the block universe. It's all things in all time. It's a 4-D block."
We perceive ourselves in one thin slice of the block. But other observers -- say, in one of those very distant galaxies in the background of Stephan's Quintet -- will perceive themselves to be in their own slice. No one's slice is more "present" than anyone else's
Each of these four images shows a universe that is obeying laws of physics that can be expressed mathematically. The gravitational attraction that is making our galaxy head toward a possible collision with the Andromeda galaxy is governed by the same equation that describes an egg falling and splattering on the kitchen floor. This is Newton's great achievement. Physicists will profess humility about what they don't know, but theirs is an audacious science, one that presumes that we can discover truths that are universal. If we make contact with aliens, physicists will leap in as the initial translators -- because in this cosmos, everyone speaks physics.
So why do these laws exist? Who wrote them? Why are they just so? The universe appears to be finely tuned to foster the rise of complex structures such as stars, galaxies, planets, living things and, eventually, theoretical physicists. Change, even fractionally, a few of the basic constants of nature -- the ratio of the gravitational force to the binding force within the atom, for example -- and no star would ever ignite.
There are those who say this is an argument for intelligent design. But that's not a testable idea. Ours could be just one of a multitude of universes that have different laws, different constants and where life never evolves. That's not a testable idea, either. But inferring anything about a creator from the array of circumstances that line up in life's favor is a stretch: Intelligent observers can exist only in universes with physical laws that allow their existence.
We've wandered deep into the territory of faith. For many religious people, the idea of multiple universes, with only some of them giving rise to life, is never going to be as satisfactory as the idea of a universe governed by an all-powerful and loving creator. But even the creator explanation doesn't really explain the origin of the cosmos. Because where does the creator come from? These are different ways of asking the very basic question: "Why is there something rather than nothing?" Greene, who spends his life trying to discover a single theory that explains and unifies the forces and particles of nature, says, "I don't think in the history of human thought we've really made any progress on that question."
But he does offer a head-scratcher of an idea. Nothingness, he says, doesn't look like a stable form of nature. Modern physics says that, at its essence, reality is unpredictable, shot through with uncertainty. So maybe Nothing just kind of ... toggled ... morphed ... twitched ... into Something. Says Greene: "You have it in your mind that Nothing is stable. But it could be that Nothing is a very unstable state. Nothing could be just always on the verge of falling apart into Something."
Which, let's face it, isn't a very satisfying explanation, either. The universe just kind of happens. It seems a mismatch of ambition and outcome, like some punk kid who can't get out of bed suddenly directing a movie starring Angelina Jolie.
***
So what does it all mean? That we're small, is one very obvious message.
This has been humbling, this investigation of space. The Copernican Principle keeps hammering flat our presumptions of specialness. Even the matter we're made of, the ordinary protons and neutrons and electrons, is trivial, compared with the much more abundant dark matter that we've yet to detect directly but are certain is out there.
But wait: Perhaps we're just getting started. We'll star-trek across the cosmos! We'll seed the universe with human intelligence and meet fascinating alien races and, occasionally, you know, mate with the ones with nice tentacles. The problem with this scenario is that NASA has put the Buck Rogers stuff on hold for the moment. Costs too much. Nowhere to go that's worth the trip. We could fly to the moon, but we already did that (they say). We could head to a near-Earth asteroid, but that would be exciting only if NASA promised to blow it up on live TV. Mars is enticing, but a Mars mission is almost as much of a budget buster as the Wall Street bailout. So, it doesn't look as if we're going to be visiting Stephan's Quintet anytime soon.
Where does that leave us with regard to outer space? It leaves us with a job: to gaze. It is our duty to look at the universe.
Let Eric Chaisson explain it: "If we weren't here, the galaxies would twirl, the stars would shine, and the universe would go on being its magnificent self. It's almost like we're animated conduits for the universe's self-reflection. If life did not occur in the universe, then the universe in all its awesomeness and magnificent beauty would not be appreciated. The universe would not come to know itself."
So, keep looking at those pretty Hubble pictures. Or, better yet, go outside on a clear night. Get away from the city. Look up and stare into the firmament
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