Our universe is perfectly tailored for life. That may be the work of God or the result of our universe being one of many.
A sublime cosmic mystery unfolds on a mild summer afternoon in Palo Alto, California, where I’ve come to talk with the visionary physicist Andrei Linde. The day seems ordinary enough. Cyclists maneuver through traffic, and orange poppies bloom on dry brown hills near Linde’s office on the Stanford University campus. But everything here, right down to the photons lighting the scene after an eight-minute jaunt from the sun, bears witness to an extraordinary fact about the universe: Its basic properties are uncannily suited for life. Tweak the laws of physics in just about any way and—in this universe, anyway—life as we know it would not exist.
Consider just two possible changes. Atoms consist of protons, neutrons, and electrons. If those protons were just 0.2 percent more massive than they actually are, they would be unstable and would decay into simpler particles. Atoms wouldn’t exist; neither would we. If gravity were slightly more powerful, the consequences would be nearly as grave. A beefed-up gravitational force would compress stars more tightly, making them smaller, hotter, and denser. Rather than surviving for billions of years, stars would burn through their fuel in a few million years, sputtering out long before life had a chance to evolve. There are many such examples of the universe’s life-friendly properties—so many, in fact, that physicists can’t dismiss them all as mere accidents.
“We have a lot of really, really strange coincidences, and all of these coincidences are such that they make life possible,” Linde says.
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Belle Discovers Three New Mesons
An international team of researchers at the High Energy Accelerator Research organization (KEK) in Tsukuba, Japan, the “Belle collaboration”*1, has announced the discovery of three new exotic sub-atomic particles, labeled as Z_1, Z_2 and Y_b. The Z_1 and Z_2 states have unit electric charge, by which these particles are clearly distinguished from normal quark-antiquark mesons, and thus can be identified as particles consisting of four quarks. The Y_b structure may be the first clear example of an exotic hybrid particle, which contains the bottom quark and its anti-particle (an anti-bottom quark) as in a conventional meson but with an excited gluon as well. In the past few years, a number of peculiar new particles, including the so-called X(3872), Y(4260), X(3940), Y(3940), have been found by the Belle and also by the BaBar experiment at the Stanford Linear Accelerator Center (SLAC). These new particles lie in the mass region from 4 to 4.5 times the proton mass, and decay into “J/psi” or “Psi-prime” particles and pi-mesons. Here the J/psi and Psi-prime particles are examples of so-called “charmonium” mesons, bound states of a charm quark and its anti-particle (an anti-charm quark). Last year, the Belle team reported the first exotic particle containing a charm and anti-charm quark with non-zero electric charge, called the Z(4430). The Z1 and Z2 particles were found in the decay products of B-mesons (mesons containing a bottom quark) that are produced in large numbers at the KEKB “B-factory”, an electron-positron collider at the KEK laboratory. The Belle team searched for new states, which decay into a pi-meson and a so-called “chi-sub-c1” meson, which is another well known charmonium meson. The measured mass values were 4051 MeV for the Z_1 and 4248 MeV for the Z_2. The newly discovered Z_1 and Z_2 states have non-zero electric charge, as was the case for the Z(4430) particle. To build a composite particle having a net unit charge, at least two additional quarks (for example, an up quark and an anti-down quark) are necessary. Therefore, data on exotic particles with non-zero electric charge attract special attention from the world’s physics community. The discovery of the Z_1 and Z_2 states, following that of the Z(4430) last year, not only provides more evidence for the existence of particles consisting of four quarks, but also indicates that the first four-quark state is not a special case, and there should be more such particles. Discoveries of exotic particles containing a charm and an anti-charm quark have stimulated the search for the possible existence of bottom-quark counterparts of such exotic particles. In 2005 BaBar at SLAC discovered a state called the Y(4260), which decays into a J/psi particle and two pions. The Y(4260) may be an example of a “hybrid particle” containing a charm quark, an anti-charm quark connected by an excited gluon. The newly discovered Y_b structure may be the first example of an exotic counterpart with bottom and anti-bottom quarks. The Y_b state was found in an energy scan at the KEKB accelerator; the Belle/KEKB team measured the production rate of a so-called “Upsilon” particle and two pions as a function of the collision energy of the electron and positron beams. Here the “Upsilon” particle is an example of a “bottomonium” meson, which is a bound state of a bottom-quark and an anti-bottom quark. The Belle team observed a dramatic increase of the production rate at 10,890 MeV, which may indicate the production of a new particle decaying into an Upsilon and two pions. Although there are other possible interpretations for this new structure, the result has attracted considerable attention as the first example of an exotic bottomonium particle. Conventional hadron particles have been classified into two types; “mesons” consisting of a quark and an anti-quark, or “baryons” consisting of three quarks. The discoveries of exotic particles both by Belle and BaBar have shed light on new classes of hadrons, formed by the strong interaction of quarks. The discovery of the Z_1, Z_2 and Y_b states by the Belle team implies that there could be more such particles of the new class, including systems containing the bottom quarks. It is critical to clarify the entire spectrum of exotic particles, in order to understand the phenomena of quark confinement as well as the formation of matter by the strong interaction. *1: The “Belle collaboration” is an international team of about 360 faculty, postdoctoral and student researchers from 59 institutes (universities and laboratories) located in 14 different countries and regions.
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What happened before the Big Bang? The conventional answer to that question is usually, “There is no such thing as ‘before the Big Bang.'” That’s the event that started it all. But the right answer, says physicist Sean Carroll, is, “We just don’t know.” Carroll, as well as many other physicists and cosmologists have begun to consider the possibility of time before the Big Bang, as well as alternative theories of how our universe came to be. Carroll discussed this type of “speculative research” during a talk at the American Astronomical Society Meeting last week in St. Louis, Missouri. “This is an interesting time to be a cosmologist,” Carroll said. “We are both blessed and cursed. It’s a golden age, but the problem is that the model we have of the universe makes no sense.” First, there’s an inventory problem, where 95% of the universe is unaccounted for. Cosmologists seemingly have solved that problem by concocting dark matter and dark energy. But because we have “created” matter to fit the data doesn’t mean we understand the nature of the universe. Another big surprise about our universe comes from actual data from the WMAP (Wilkinson Microwave Anisotropy Probe) spacecraft which has been studying the Cosmic Microwave Background (CMB) – the “echo” of the Big Bang. “The WMAP snapshot of how the early universe looked shows it to be hot, dense and smooth [low entropy] over a wide region of space,” said Carroll. “We don’t understand why that is the case. That’s an even bigger surprise than the inventory problem. Our universe just doesn’t look natural.” Carroll said states of low-entropy are rare, plus of all the possible initial conditions that could have evolved into a universe like ours, the overwhelming majority have much higher entropy, not lower. But the single most surprising phenomenon about the universe, said Carroll, is that things change. And it all happens in a consistent direction from past to future, throughout the universe. “It’s called the arrow of time,” said Carroll. This arrow of time comes from the second law of thermodynamics, which invokes entropy. The law states that invariably, closed systems move from order to disorder over time. This law is fundamental to physics and astronomy. One of the big questions about the initial conditions of the universe is why did entropy start out so low? “And low entropy near the Big Bang is responsible for everything about the arrow of time” said Carroll. “Life and death, memory, the flow of time.” Events happen in order and can’t be reversed. “Every time you break an egg or spill a glass of water you’re doing observational cosmology,” Carroll said. Therefore, in order to answer our questions about the universe and the arrow of time, we might need to consider what happened before the Big Bang. Carroll insisted these are important issues to think about. “This is not just recreational theology,” he said. “We want a story of the universe that makes sense. When we have things that seem surprising, we look for an underlying mechanism that makes what was a puzzle understandable. The low entropy universe is clue to something and we should work to find it.” Right now we don’t have a good model of the universe, and current theories don’t answer the questions. Classical general relativity predicts the universe began with a singularity, but it can’t prove anything until after the Big Bang. Inflation theory, which proposes a period of extremely rapid (exponential) expansion of the universe during its first few moments, is no help, Carroll said. “It just makes the entropy problem worse. Inflation requires a theory of initial conditions.” There are other models out there, too, but Carroll proposed, and seemed to favor the idea of multi-universes that keep creating “baby” universes. “Our observable universe might not be the whole story,” he said. “If we are part of a bigger multiverse, there is no maximal-entropy equilibrium state and entropy is produced via creation of universes like our own.”
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Astronomers watch as star dies
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18 billions of suns support Einstein
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How the brain detects the emotions of others
Doubt cast on source of universe’s mightiest particles
Physicists Demonstrate How Information Can Escape From Black Holes
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Big Bang Experiment Ready To Go
Physicists and engineers search for new dimension
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