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Is There an Edge to the Universe?
from Through the Wormhole; Once in a while, a really big idea comes along one that completely changes our concept of who we are. In 1543, Nicolas Copernicus proved that the Earth was not at the center of the cosmos. In the 1920s, Edwin Hubble saw that all the galaxies in the Universe were rushing away from one another, sparking the idea that the Universe had not been here forever but was created in one explosive moment the Big Bang. Now another monumental change is upon us. We've long imagined the Universe to be infinite in size, but many cosmologists now think the Universe is finite. Some believe they even know its shape. If we do discover an edge to the Universe, we'll have to grapple with another very challenging and unsettling question. What lies beyond the edge? Every day on my way home from school, I used to pass a long wall. It was at least twice my height. I had no chance of seeing over it, but I could hear strange sounds coming from behind it. I never did find out, but I never stopped wondering. Neil Cornish is a cosmologist who lives and works in the big sky country of Montana. Neil is the latest in a long line of thinkers to contemplate the size of the Universe. The first we know of was a Greek philosopher king called Architus. The Greek philosopher Architus offered an argument for why the Universe must be infinite. He said, "If I was to go out to the edge of the Universe and then extend my staff to here, that would now be the edge of the Universe. And then, if I was to extend my staff to here, that would now be the new edge of the Universe. Big Bang creates a problem for astronomers searching for the edge of the Universe. Because it takes light time to travel across the vastness of space, astronomers were always looking back in time, and, eventually, they run out of time. The Cosmic Microwave Background is a barrier that blocks our vision. Behind it, there could be an edge. Or perhaps the Universe does extend on forever. But no matter how powerful our telescopes become, that domain will never be visible. But there might be another way to discover if the Universe has an edge. Janna Levin is a theoretician who uses complex numerical simulations to solve some of science's most challenging problems. It might surprise you that a game as old as "Asteroids" can teach us something about the Universe, but there's a rule in the game to make a world out of the game that makes sense, where, if you exit the top, you re-enter the bottom, or if you exit the left, you re-enter from the right. Backward in time. Is our Universe a hall of mirrors? Astronomers have looked for repeating patterns of galaxies for years, looking for evidence that the Universe has an edge. But they've never found any. Jean-Pierre Luminet is a senior scientist at the Paris Observatory. He's been fascinated with the shape of space ever since he was a child. I was always interested in shapes created by nature. If Jean-Pierre is right, the shape of the Universe is a lot more complex than a six-sided "Asteroids" game cube. The Universe has 12 sides, and leaving one face leads you to a matching pentagon on the opposite side, but with a twist. This edge is exactly the same as the opposite edge. So, as soon as you get to this point, you re-enter your space on the opposite side, and, in addition, you have to turn by 36 degrees. If the Universe were a dodecahedron only slightly bigger than Earth, light would zip around it in minutes, and you would see twisted copies of Earth in a dozen different directions in the sky. But if the edges of Jean-Pierre's dodecahedron are billions of light-years apart, the distant and faint reflections on them could have escaped the notice of the most careful astronomers. And if the edges lie further than 13.7 billion light-years from Earth, we would never be able to see them because our view would be blocked by the hot soup of the Cosmic Microwave Background. As soon as Jean-Pierre announced his results, Neil Cornish begins looking for signs of his colossal soccer ball. He's a key scientist on a NASA spacecraft called WMAP, which spent five years photographing the Cosmic Microwave Background in unprecedented detail. At stake is nothing less than the truth about where we live, where we came from, and whether our Universe is alone. Einstein said, "Only two things are infinite the Universe and human folly." But he admitted he couldn't be sure about the Universe. In fact, we are now faced with tantalizing hints that our Universe may not stretch on forever, that there is a point out there where the Universe as we know it does not exist. It's an almost frightening thought. But before we try to grasp just what might lay beyond that final boundary, we need proof. Glenn Starkman is a Canadian physicist at Case Western University in Cleveland. He's taken data analysis to new heights in search of that proof. Call him an information junky. The joke about Canadians is that you go to an airport and you put up a sign "Free sex to the right" and "Free information on sex to the left", and the Canadians are all the ones that go to the left. I hope l'm not that boring. Glenn had been poring over Cosmic Microwave Background data from the WMAP probe for most of the past seven years. Along with Neil Cornish, he's been trying to test Jean-Pierre Luminet's prediction that the shape of space is like a 12-sided soccer ball. I would have been really happy to find the pattern of circles that the dodecahedron told us would be there if the dodecahedron was small, and we looked for and we didn't find. But all of their tests assumed that the edges of the soccer-ball universe are closer than the Microwave Background that blocks our view. Now Glenn believes he's found a way to detect the edge of the Universe, even if it lurks beyond the area we can see. What you have to understand is what is this actual pattern of hot and cold spots that we're seeing on the sphere. And what it really is sound waves that were traveling through the Universe when it was very young. Andy Albrecht, a theoretical physicist at U.C. Davis, is sure the Universe is finite. He even thinks he can calculate its size. Andy studies the very first moments after the Big Bang, when space was nothing more than a seething, chaotic ball of energy. Most cosmologists think inflation is the best explanation for the even spread of galaxies across our visible Universe. But far out in space, there may be regions where inflation never took place. Find those, and you could be the first to find evidence of the edge of the Universe. The eternal dance of light in the night sky it has fascinated humankind for thousands of years, given birth to gods, myths, and, finally, to science. But now there are hints of strange movements in the heavens. If they can be verified, they'll be the first hard evidence that there is an edge to the Universe. Sasha Kashlinsky is a NASA astronomer. He claims to have detected a pattern of movement in the heavens so bizarre that it could revolutionize our theory of the Universe, just as the Big Bang once did. We're here at Glendale Golf Course near NASA's Goddard Space Flight Center. And we came here to simulate the Big Bang. When light from the Cosmic Microwave Background passes through that hot gas, it gets subtly altered. How much it changes depends on exactly how fast the gas and the galaxies it surrounds are moving. But the change is tiny and almost completely buried in background noise. For each individual cluster, this is a very tiny amount, and it gets drowned by the noise. But if you have many clusters, you can beat down the noise, but it's exceedingly difficult. Sasha methodically worked his way through a catalog of galaxy clusters from an orbiting x-ray telescope, checked their precise position using ground telescopes, and then carefully lined them up with the Cosmic Microwave Background. Oh, we were quite shocked when we saw these results at first. In fact, so much that we didn't know what to do with it. We kept checking and checking. We sat on the data for a year-plus, just checking everything, because it just didn't make sense to us. What Sasha's data showed was almost unbelievable. All the galaxy clusters, no matter where they were in the sky, were all veering off to one side of the Universe. It was as if they were being pulled towards a mysterious attractor beyond the visible edge. He called it "Dark Flow." We called it "Dark Flow" because the observed distribution of matter in the Universe cannot account for this motion. But if nothing Sasha could see was pulling the galaxies to one side, what could be responsible for the effect? The answer could be the edge of the Universe. If you live in this part of the world, then, at first, you would imagine that the entire world is as flat as what you see locally. But there's an even more shocking possibility. Dark Flow could be evidence of another universe reaching out to us. That's what theoretical physicist Laura Mersini-Houghton thinks. The seed of this idea was planted many years ago when she realized she had a problem with the Universe a pretty big problem. According to her calculations, the Universe should not exist. The chances to start the Universe with the high-energy Big Bang are one in 10 with another 10 zeros behind it and another 123 zeros behind it. So, pretty much, zero. In 2007, data from the WMAP spacecraft confirmed the presence of a strange, cold spot in the Cosmic Microwave Background. If I have an empty region of space, that would show as a cold temperature region. In the case of the cold spot, the only way such a part of the sky could just be completely, entirely empty, that kind of bizarre behavior of the Universe can occur only if there is some other force at work. Laura believes the cold spot is evidence of another universe right next to ours, its enormous mass pulling on matter at the edge of our world. If there are some very massive objects in the next room in other words, in the neighboring universe then I should be able to feel that gravitational pull, although I cannot directly see it. But for a theory as radical as the existence of another universe, the cold spot alone is not enough. Laura needs more evidence. And help is at hand. Two scientists are about to join forces in a remarkable endeavor to find the size and shape of our Universe and the universe next door. Is the Universe infinite? Or does it have an edge? Or is our Universe just one member of a cosmic family of universes, spread across a strange and uncharted landscape? Just a few years ago, even asking these questions was unthinkable. Now we're close to finding the answer. Sasha Kashlinsky is convinced that some mysterious attractor at the edge of our Universe is pulling on galaxies, forcing them to move with what he calls "Dark Flow." His work is still controversial, and to convince the skeptics, he needs more data. We hope, in a few years, to have a catalog of up to 2,000 galaxy clusters in total. And with the new data, we hope that we'll be able to measure the flow to much larger scales. But Sasha now has a powerful ally. 1,000 miles away, in Toronto, Laura Mersini-Houghton was defining her own calculations about the edge of the Universe when she got a phone call from her mother.
And she says to me,
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