How sticky toepads evolved in geckos


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“We thought that inflation predicted a smooth, flat universe,” says Paul Steinhardt of Princeton University, a pioneer of inflation who has become a vocal detractor.  “Instead, it predicts every possibility an infinite number of times. We’re back to square one.” Tegmark agrees: “Inflation has destroyed itself. It logically self-destructed.”  Sean Carroll was only a little less pessimistic.  ““Inflation is still the dominant paradigm,” he said, “but we’ve become a lot less convinced that it’s obviously true.”  By starting with such precisely balanced conditions, it explains less than the flukes it was intended to explain.  ““If you pick a universe out of a hat, it’s not going to be one that starts with inflation,” he said.

  • “We thought that inflation predicted a smooth, flat universe,” says Paul Steinhardt of Princeton University, a pioneer of inflation who has become a vocal detractor.  “Instead, it predicts every possibility an infinite number of times. We’re back to square one.” Tegmark agrees: “Inflation has destroyed itself. It logically self-destructed.”  Sean Carroll was only a little less pessimistic.  ““Inflation is still the dominant paradigm,” he said, “but we’ve become a lot less convinced that it’s obviously true.”  By starting with such precisely balanced conditions, it explains less than the flukes it was intended to explain.  ““If you pick a universe out of a hat, it’s not going to be one that starts with inflation,” he said.



Brane Drain

  • Brane Drain

  • Gefter took a brief tour into other cosmological theories that arose to replace inflation, such as brane theory: two 4-D projections of 5-D surfaces collided at perfect parallels, yielding a big-bang lookalike.  One benefit for those uncomfortable with a cosmic beginning is that it resurrects old hopes of a cyclic universe with an infinite past.  Any theory, though, that tries to explain special conditions (e.g., our universe) with even more special conditions fails to show the kind of scientific progress cosmologists prefer–simple beginnings leading to complex observations, a “theory of everything.”  Thus, a “brane drain,” as Gefter dubbed it  –



If nothing else, the cyclic model introduced some competition into the big bang market. “It shows that you’re not stuck with inflation — other ideas are possible,” says Steinhardt. “But whether or not you like this particular alternative is a matter of taste.

  • If nothing else, the cyclic model introduced some competition into the big bang market. “It shows that you’re not stuck with inflation — other ideas are possible,” says Steinhardt. “But whether or not you like this particular alternative is a matter of taste.

  • Not everyone did. Models of the big bang that involve a singularity in our space-time, including the inflationary big bang, neatly excuse us from explaining what happened at the universe’s beginning: the singularity is a place where the universe falls off the cliff of existence and the laws of physics break down. But in the cyclic model, we must explain how the fifth dimension survives its momentary lapse into a singularity.



“To me, it doesn’t seem to work,” says Thomas Hertog of the Catholic University of Leuven (KUL) in Belgium, who worked on the idea for a couple of years. “The calculations suggest that the transition through the singularity is very unlikely.” The many clashes between branes that the model implies just compound the problem, says Carroll. “If you follow the cyclic universe backward in time, the conditions that you need become more and more special, or unlikely.

  • “To me, it doesn’t seem to work,” says Thomas Hertog of the Catholic University of Leuven (KUL) in Belgium, who worked on the idea for a couple of years. “The calculations suggest that the transition through the singularity is very unlikely.” The many clashes between branes that the model implies just compound the problem, says Carroll. “If you follow the cyclic universe backward in time, the conditions that you need become more and more special, or unlikely.



No Boundaries

  • No Boundaries

  • Next came the “No-Boundary Proposal” of Stephen Hawking and James Hartle, made famous in the former’s best sellerA Brief History of Time.  Gefter described it as a kind of “multiverse in reverse,” where Hawking and Hartle “added up all the possible histories that began in a universe with no boundary and ended in the universe we see today.”  Though some were initially attracted to the proposal because it seemed to get rid of a beginning to the universe, it hardly merited a couple of paragraphs in Gefter’s review: “That all sounds very neat, but there was still no reason to believe the no-boundary proposal was true. It was difficult to see where it fitted in to the sort of unifying theoretical constructs, such as string theory, which are needed to explain events in the early, high-energy days of the universe.”



Cosmic Combo Plate

  • Cosmic Combo Plate

  • Nothing seemed to work.  How about a combination?  Gefter tried to end on a cheerful note by suggesting that maybe a combination of inflation, string theory, the no-boundary proposal might serve up a universe that solves the problems inflation tried to solve without making things worse. Adding bad ideas together might seem another bad idea.  There had to be at least one new trial ingredient, and string theory served up the spaghetti:





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