Across the Universe

Thursday was the first day of the World Science Festival, and I was lucky enough to score tickets to what I consider the best event they've sponsored in two years of their existence, Navigating the Cosmos. Neil deGrasse Tyson, champion of Pluto's planetude and director of the Natural History Museum's Hayden Planetarium, arranged the spectacle: a digital compendium of images of the universe so detailed and vast that you can literally bring binoculars to see more of the sights. As Tyson told us, "No frontier of cosmic discovery is beyond our reach. .. They put pieces of this [digital universe] in space ships, but we'll see the whole thing .. a hand-guided journey through the universe." The dome of the planetarium will become the night sky, and then something else altogether.

I admit I got a little tired of hearing about it at this point, but once the introductions (Brian Abbot, the joystick operating Manager of the Digital Universe, Jim Gates, Lawrence Krauss, and Evalyn Gates, Queen of Dark Matter) were done and the lights went down, we were set free to roam the vast depths of space. Brain sent us rolling around the night sky, first hovering weightless over Manhattan so Neil could show us Broadway (inexplicable).Then up to the moon's orbit we fly; Larry tells us the energy we see from the sun took a billion years to travel to its surface from its center.

We drift backward away from home, past ring after ring of planetary orbit. Yellow jagged trajectories marked where Voyagers 1 and 2 looped their separate, gravity-warped ways out of the solar system, where, Neil said, they will later be discovered by an alien culture and repurposed before finding humans again...past Pluto, which makes Neil sigh sadly. Such a fate, but be fair, its orbit is so akilter, and it's so small...and then we're in our familiar arm of the Milky Way so that Larry can blow smoke up our asses: we are all star children, connected to the cosmos, he told us. Every atom was once a star.

When the universe began, he says, hydrogen, helium and lithium (which some of you may be more familiar with), were the only atoms in existence. The rest of the elements were created in the stars. 200 million stars have blown up, he told us. you are only here because of them. Every atom in your body has been through a supernova. Eery hundred years, he says, per galaxy, there's a supernova.

Brian drags us unceremoniously out of reach of our galaxy and into the vast reaches, etc. so we can get a look at Alpha and Beta Centauri. Crap. It's dizzying. I can't imagine how much faster than light we'd have to travel. we're surrounded by tiny, blurry, glowing dots. Those dots, Larry tells us, are not stars. They're galaxies. Images of galaxies that we've taken with one instrument or another, right where they belong. Larry tells Brian to show us the patches of completed star maps, and suddenly entire strips of the universe go white. Those, he tells us, are not just bald patches those are the areas of space where we've mapped everything we can detect. Behind each galaxy, another galaxy, and another, so that the whole strip is blotted to white.

The ratios of distance to speed, so you know how fast this is all moving, is this: galaxies that are twice as far away are moving twice as fast. Galaxies that are three times as far away are moving 3x as fast. That's what makes physicists postulate dark energy, a repulsive force driving the universe apart, the opposite, in a sense, of gravity. And since the movement of everything away from each other is speeding up, not slowing down, it's possible all the objects in the universe will at some point exceed the speed of light, which means we'll no longer be able to see them. The rest of the galaxies will disappear from the night.

Why is the universe like this, he asks us. Because we are here to observe it. And there is a structure to all these galaxies. They develop from a general haze to form filaments. Within the filaments, Evalyn tells us, are groups of galaxies bound together by gravity, tumbling along in space all tethered by dark matter. There is, she tells us 50 times as much mass in the universe as what we can see, but it doesn't shine.

The big bang, she says, is an opaque wall. When the big bang occurred she says, it ws so hot that no atom could exist, only protons, neutrons, plasma. You can't see past that old charged plasma. What you can see is the cosmic microwave background radiation. Discovered, Jim adds ruefully by a couple of guys in New Jersey who weren't even looking at it. Relax, Neil tells him, you'll get your Nobel.

Jim says, you know that static on an old tv, 19% of that static is microwave radiation from the big bang. He shows us our options about the shape of the universe, based on the form of the CMB. Only in a flat universe are the bumps of the CMB the same pattern and size as what we see out at the end of our ability to see. But if this is the correct form of the universe, then 70% of it is missing. Empty space, he tells us, weighs something. Larry and Jim want you to know that they're interested in the shape of the universe because this is how they're going to figure out how the Universe will end. If it's curved, that means light goes around and back to its source (if you look far enough, you'll see the back of your own head). If it's open, and infinite, matter will expand forever. If it's closed, matter will collapse again into a lump. If it's too big, gravity won't be able to travel across it. Gravity is restricted to the speed of light, like everything else. But the size of the universe affects the speed of light.Only in a flat universe is gravity and light speed at the right balance.

Then Evalyn shows us how to look at the universe through Einstein's telescope. 349 exoplanets (that is, they're outside our system) have been discovered so far, using the light bending properties of gravity predicted by Einstein. She brings up an image of the planets we've found, pointers like daisy petals around them, centered around Earth because that's where we were when we found them through gravitational microlensing. It's simple. You look at a star and you can tell by the way its light bends that something is disrupting it. By observing this over time you can tell that this something orbits around the star. And you can use this lensing phenomenon to find dark matter, too.

She tells Brian to drag us cursor like over to Ursa Major, and there we float, while she shows us a bundle of galaxies, all traveling and interacting together gravitationally. They're bound together by a huge mass of dark matter, and those identical looking quasars are actually reflections of one quasar among the many galaxies embedded in this sea of dark matter. You can tell by watching them over time. An event in one is echoed in all of them. And dark matter affects time. The light varies in quasars so you can see the patterns of variation and how long it takes to be reflected -- longer than it takes for light to travel. Then she shows us a series of galaxies, each surrounded by a blue halo. Each blue ring, she says, is another galaxy. a few billion light years behind. The closer galaxy and lumps of dark matter bend the light from behind it. lensing it so that it forms a halo, called an Einstein ring. The first one was seen in 1987. The lens is made out of space time.

Dark matter forms a web she tells us, 4-5 million light years across. Galaxies travel in knots in this cosmic web, in those filaments I mentioned that have gathered out of the earlier cosmic fog of matter. You can see it through gravitational lensing: when light travels through dark matter, it's altered, so you can trace out the shape of the dark matter, and figure out what it looks like. You can measure its effect, plot it out in charts. In other words, you can "see" it because its gravity warps spacetime, warps light, warps the very form of all the cosmos.

And if you ever wanted to visit the empty space between the known cosmos and the cosmic microwave background radiation, here's your ticket.

Jai guru dev om.