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When played together, they compose the symphony of the universe. Or at least, that's the theory. There's a problem, though. The strings have too much range. So much, in fact, that for string theory to agree with the established laws of physics and mathematics, there must be not three but at least ten dimensions (including time) that are curled up and tucked away. And because each of these multidimensional landscapes requires a different string tuning, there are potentially billions and billions of different versions of string theory relating to billions and billions of different universes. Then there's the problem of...

In 1676, Isaac Newton explained his accomplishments through a simple metaphor. "If I have seen farther it is by standing on the shoulders of giants," he wrote. The image wasn't original to him, but in using it Newton reinforced a way of thinking about scientific progress that remains popular: We learn about the world though the vision of a few colossal figures... "The main difference today is there are so many people working on these deep problems," the physicist Brian Greene said recently. In one 15-page span of his best-selling book "The Elegant Universe" (1999), Greene mentions 24 scientists whose...

The essential claim of string theory is that what we perceive as electrons, photons and other sub-atomic particles are actually tiny one-dimensional snippets of energy vibrating furiously in 11 dimensions. The theory seemed, at first, to offer a promising path forward toward the goal of seamlessly melding relativity and quantum mechanics because it overcame mathematical problems that had dogged earlier efforts at reconciliation. Sadly, reality has turned out to be at odds with the dreams of string theorists. For starters, there seems to be no possible way to test string theory experimentally... More ominously, out of the deep mathematical recesses...

Dark energy - the mysterious force that is speeding up the expansion of the Universe - has been a part of space for at least nine billion years. That is the conclusion of astronomers who presented results from a three-year study using the Hubble Space Telescope. The finding may rule out some competing theories that predict the strength of dark energy changes over time. Dark energy makes up about 70% of the Universe; the rest is dark matter (25%) and normal matter (5%). "It appears this dark energy was already boosting the expansion of the Universe as much as...

Now a group of astronomers using the Hubble Space Telescope have discovered that billions of years before this mysterious antigravity overcame cosmic gravity and sent the galaxies scooting apart like muscle cars departing a tollbooth, it was already present in space, affecting the evolution of the cosmos... The new results, Dr. Riess and others said, provide new clues and place new limits on the nature of dark energy, a mystery that has thrown physics and cosmology into turmoil over the last decade... The data suggest that in fact dark energy has changed little, if at all, over the course of...

Why is it that string theory has become such a favoured paradigm? Have theoretical physicists deluded themselves? Have they been pressured by social forces to blind themselves to other possible theories? Is there a behind-the-scenes string-theory conspiracy that is propping up a pseudoscientific house of cards? ...An essential criterion is whether there is experimental evidence to support the theory. We have a description, called the Standard Model of particle physics, which agrees with observations exceedingly well, with a few small exceptions. A reactionary could ask, since the present model works so well, why bother to look for something new? From...

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The Belle collaboration at the KEK laboratory in Japan has discovered a new sub-atomic particle which it is calling the "X(3872)". The particle does not fit into any known particle scheme and theorists are speculating that it might be a hitherto unseen type of meson that contains four quarks (arxiv.org/abs/hep-ex/0309032; Phys. Rev. Lett. to be published). The discovery has been confirmed by the CDF collaboration at Fermilab in the US, where the new particle is being called the "mystery meson". Mesons are particles that contain a quark and an antiquark that are held together by the strong nuclear force. Since...

In part 2 of the interview, Astronomer Royal, Sir Martin Rees discusses the limits to our knowledge of what might have preceded the big bang. Everyone asks the question: what was 'there' the instant before everything came to be?, but the question may not go as deep as the answers it spawns. Helen Matsos: Last year the big "science event" was measuring the cosmic microwave background and dating the big bang to 13.8 billion years ago, within an 8 to 10 percent margin of error. Can you give us some idea of the boundaries of the big bang -- what...

Lisa Randall has become a star in the rarefied world of high-energy physics, and her theory about a “fifth dimension” has caught the imagination of the general public too. That doesn’t mean she still isn’t shy and a little nervous about all the hoopla. “I really like that my work is getting more people interested in science,” says the 43-year old Harvard physicist. “And while it can get a little nerve-wracking dealing with all the attention, I really enjoy speaking to the public and answering questions.” Randall seems constantly in motion. She seldom sits still, and says her mind brims...

The European Space Agency is considering a unique experiment that could explain strange gravitational phenomena in the outer solar system. Since 1998 astronomers have known that the space probes Pioneer 10 and Pioneer 11 are following trajectories that cannot be explained by conventional physics. Launched in 1972 and 1973, respectively, to explore the outer planets, the Pioneer craft are now at the edge of the solar system, with Pioneer 10 being some 86 astronomical units (about 13 billion kilometres) from the Sun. But they are not quite where they should be, based on the gravitational pull of the known bodies...

SEARCH RESULTS Evidence for Universe Expansion FoundEvidence for Universe Expansion FoundScientists: Find explains how universe formedCold War gamma-ray mystery solved in a flashU.S. spacecraft set to study cosmic bursts Front page March 17, 2006, 12:51AMOldest light shows universe grew fast, researchers sayFirst stars arose 400 million years after big bang, not 200 million years, as once thought By DENNIS O'BRIEN Baltimore Sun Scientists examining the oldest light in the universe say they've found clear evidence that matter expanded at an almost inconceivable rate after the big bang, creating conditions that led to the formation of the first stars.Light from...

It was the summer of 1998, recalls Harvard University physicist Lisa Randall, when extra dimensions finally pulled her in. Extra dimensions -- beyond the four we encounter every day (three of space plus one of time) -- have been an ingredient of theoretical physics for decades: mathematician Theodor Kaluza proposed a fifth in 1919, string theory requires 10 of them, M-theory needs 11. But Randall hadn't much use for them, she says, until that summer when she decided they might be helpful to supersymmetry, one of the conundrums she was pondering. Randall contacted Raman Sundrum, a Boston University postdoctoral student...

Gamma-ray bursts could be the signature of ultradense stars. This X-ray image shows the 3C58 pulsar, the remnant of a supernova noted on Earth in AD 1181, which astronomers suspect may be a quark star. It lies about 10,000 light years from Earth.© NASA/SAO/CXC/P.Slane et al. Intense flashes of gamma rays in far-off galaxies might be produced by a bizarre kind of star, consisting of phenomenally dense material in which the particles that make up atomic nuclei have fallen apart. Two astrophysicists have proposed that gamma-ray (gamma-ray) bursts, whose origins have foxed astronomers for decades, might be the signatures of...

In what is widely regarded as the most important scientific discovery of 1998, researchers turned their telescopes to measure the rate at which cosmic expansion was decelerating and instead saw that it was accelerating. They have been gripping the steering wheel very tightly ever since. As deeply mysterious as acceleration is, if you just accept it without trying to fathom its cause, it solves all kinds of problems. Before 1998, cosmologists had been troubled by discrepancies in the age, density and clumpiness of the universe. Acceleration made everything click together. It is one of the conceptual keys, along with other...

Scientists are closer than ever to balancing the checkbook of cosmic matter. This is because two recent independent measurements of normal matter in the universe are in agreement. The results further strengthen the case for the Big Bang theory and for the nature of the universe as astronomers understand it today. The universe contains normal atomic matter, what makes you, your dog, the stars, and everything in between. Normal matter is what Carl Sagan was talking about when he said we are all star-stuff. But in addition to star-stuff, there is invisible dark matter that is known only because the ...

A GROUP of astronomers and cosmologists has warned that the laws thought to govern the universe, including Albert Einstein's theory of relativity, must be rewritten. The group, which includes Professor Stephen Hawking and Sir Martin Rees, the astronomer royal, say such laws may only work for our universe but not in others that are now also thought to exist. "It is becoming increasingly likely that the rules we had thought were fundamental through time and space are actually just bylaws for our bit of it," said Rees, whose new book, Our Cosmic Habitat, is published next month. "Creation is ...

The genius of Albert Einstein, who added a "cosmological constant" to his equation for the expansion of the universe but later retracted it, may be vindicated by new research published today in the journal Astronomy and Astrophysics. The enigmatic "dark energy" that drives the acceleration of the Universe behaves just like Einstein's famed cosmological constant, according to the Supernova Legacy Survey (SNLS), an international team of researchers in France and Toronto and Victoria in Canada, collaborating with large telescope observers in Oxford, Caltech and Berkeley. Their observations reveal that the dark energy behaves like Einstein's cosmological constant to a precision...

WASHINGTON, D.C. - Scientists may not have to go over to the dark side to explain the fate of the universe.The theory that the accelerated expansion of the universe is caused by mysterious "dark energy" is being challenged by New York University physicist Georgi Dvali. He thinks there's just a gravity leak.Scientists have known since the 1920s that the universe is expanding. In the late 1990s, they realized that it is expanding at an ever-increasing pace. At a loss to explain the stunning discovery, cosmologists blamed it on dark energy, a newly coined term to describe the mysterious antigravity force...

Grisha Perelman, where are you? Three years ago, a Russian mathematician by the name of Grigory Perelman, a k a Grisha, in St. Petersburg, announced that he had solved a famous and intractable mathematical problem, known as the Poincaré conjecture, about the nature of space. After posting a few short papers on the Internet and making a whirlwind lecture tour of the United States, Dr. Perelman disappeared back into the Russian woods in the spring of 2003, leaving the world’s mathematicians to pick up the pieces and decide if he was right. Now they say they have finished his work,...