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The Wow Factor: Joel Achenbach gives us an even briefer history of time and space
It's hard to look at the Omega Centauri image without thinking, We are not alone. How could we be? The universe is so flamboyantly abundant and huge and awesome. J. William Schopf, a legendary UCLA professor who studies the origin of life, says: "I find it really, really difficult to imagine that the universe is not teeming with life. I don't know about intelligent life, but I think there must be a bunch of that out there, too. Our star is a normal, main-sequence star, so there's nothing special about it. We live on a rocky planet that has a lot of liquid water, but the Earth is 98 percent just like Venus, except Venus is closer to the sun. And I think such planets must be very common. There's nothing special about us, as far as I can tell."
This is a common sentiment among scientists. But there's a counterargument: There are a lot more ways to be dead than to be alive in this universe. In fact, when you look at all those stars in this globular cluster, you're looking at a patch of sky where life may never have taken hold. The stars are so close together that they would create a gravitational maelstrom that would prevent planet formation. Moreover, exploding stars would sterilize everything nearby.
"When you've gone to a globular cluster, you've gone to a not terribly good neighborhood," says Mario Livio, an astrophysicist with the Space Telescope Science Institute.
Earths aren't exactly a dime a dozen. Space all but screams at us: Take care of your planet, because you aren't likely to have a second chance. Our own solar system appears to be chockablock with dead worlds. Schopf's point about Venus can be turned around: This virtual twin of Earth is a furnace with temperatures at the surface of 800 degrees Fahrenheit. Mars may have had life once, but if there's any left, it's hanging by its alien fingernails.
Schopf's recitation of the Copernican Principle -- the realization that the universe doesn't revolve around Earth, that we're not in a special position -- can be extended even further: Not only is the universe not about us, the universe isn't necessarily about the thing we love most, which is life. Sure, the universe is filled with "vital dust" -- complex molecules that prime the pump for the possible emergence of living things. But the universe is also saturated with lethal radiation. Space is a harsh environment, in general. It would be wrong to see the place as preferentially biased toward habitability. There's lots of ice out there. Amazing rocks. It may be that God is a geologist.
The final picture is called Stephan's Quintet. At first glance, it looks like four galaxies, but then you see that the central object is two merging galaxies, with two galactic cores, like a double-yolk egg. The four orange-yellow galaxies will probably merge into a single galaxy; the blue-white galaxy is much closer to us and just happens to be in the line of sight of the other four.
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.