If neutrinos really do travel at a velocity slightly higher than the speed of light, we have a measurement that challenges Einstein, a fact that explains the intense interest in explaining the results at CERN that we discussed on Friday. I think CERN is taking exactly the right approach in dealing with the matter with caution, as in this statement from a Saturday news release: ...many searches have been made for deviations from Einstein's theory of relativity, so far not finding any such evidence. The strong constraints arising from these observations make an interpretation of the OPERA measurement in terms of modification of Einstein's theory unlikely, and give further strong reason to seek new independent measurements. And this is followed up by a statement from CERN research director Sergio Bertolucci: "When an experiment finds an apparently unbelievable result and can find no artifact of the measurement to account for it, it's normal procedure to invite broader scrutiny, and this...

If you're tracking the interesting news from CERN on neutrinos moving slightly faster than the speed of light, be advised that there is an upcoming CERN webcast on the matter at 1400 UTC later today (the 23rd). Meanwhile, evidence that the story is making waves is not hard to find. I woke up to find that my local newspaper had a headline -- "Scientists Find Signs of Particles Faster than Light" -- on the front page. This was Dennis Overbye's story, which originally ran in the New York Times, but everyone from the BBC to Science Now is hot on the trail of this one. The basics are these: A team of European physicists has measured neutrinos moving between the particle accelerator at CERN to the facility beneath the Gran Sasso in Italy -- about 725 kilometers -- at a speed about 60 nanoseconds faster that it would have taken light to make the journey. The measurement is about 0.0025 percent (2.5 parts in a hundred thousand) greater than the speed of light, a tiny deviation, but one of...

by James F. Woodward I first wrote about James Woodward's work in my 2004 book Centauri Dreams: Imagining and Planning Interstellar Exploration, and have often been asked since to comment further on his research. But it's best to leave that to the man himself, and I'm pleased to turn today's post over to him. A bit of biography: Jim Woodward earned bachelor's and master's degrees in physics at Middlebury College and New York University (respectively) in the 1960s. From his undergraduate days, his chief interest was in gravitation, a field then not very popular. So, for his Ph.D., he changed to the history of science, writing a dissertation on the history of attempts to deal with the problem of "action-at-a-distance" in gravity theory from the 17th to the early 20th centuries (Ph.D., University of Denver, 1972). On completion of his graduate studies, Jim took a teaching job in the history of science at California State University Fullerton (CSUF), where he has been ever since. Shortly...

The far future may be a lonely place, at least in extragalactic terms. Scientists studying gravity's interactions with so-called dark energy -- thought to be the cause of the universe's accelerating expansion -- can work out a scenario in which gravity dominated in the early universe. But somewhere around eight billion years after the Big Bang, the continuing expansion and consequent dilution of matter caused gravity to fall behind dark energy in its effects. We're left with what we see today, a universe whose expansion will one day spread galaxies so far apart that any civilizations living in them won't be able to see any other galaxies. The initial dark energy findings, released in 1998, were based on Type Ia supernovae, using these as 'standard candles' which allowed us to calculate their distance from Earth. Now we have new data from both the Galaxy Evolution Explorer satellite (drawing on a three-dimensional map of galaxies in the distant universe containing hundreds of millions...

Gravity Probe B has confirmed two of the most interesting effects predicted by Einstein's General Theory of Relativity. The geodetic effect, which describes the warping of spacetime due to the mass of the Earth, has been confirmed to an accuracy of 0.28 percent. The frame-dragging effect, in which the Earth's rotation drags or stirs local spacetime, is confirmed to 19 percent accuracy. All of this from a project that drew on 34 years of research and development, 10 years of flight preparation and 5 years of analysis of the data returned from a 1.5 year mission. They were a long time coming, but these results are as much milestones in the history of physics as the 1919 measurements of Sir Arthur Eddington that supported Einstein's newly published theory. Subtle Effects, Fantastic Precision Measuring known effects to higher levels of accuracy is key to physics. It has taken so long to achieve these results because General Relativity is hard to test in the vicinity of the Earth, where...

What on Earth -- or off it -- could inspire a physicist with the credentials of Caltech's Kip Thorne to say "I've never before coauthored a paper where essentially everything is new. But that's the case here." Yet if Thorne couldn't say that about some of his earlier work with wormholes (!), he feels safe in saying it about the new tools for visualizing warped space and time that are discussed in a paper he and his colleagues have just published. Imagine space and time undulating in hitherto unfathomable patterns as objects like black holes run into each other. How do we visualize such effects in a credible way? The new tools help us do just that. They are the result of powerful computer simulations that bring to visual life the complex equations of black hole mergers and other extreme events, and they should help us with problems like this one: Manuela Campanelli (University of Texas in Brownsville) and team used simulations a few years ago to show that colliding black holes produce...

The fascination of the so-called ‘Pioneer anomaly’ is that it offers the possibility of new physics, an apparently constant acceleration on the Pioneer 10 and 11 probes with a value of (8.74 ± 1.33) × 10?10 m/s2 being something that we can’t easily explain. Equally useful is the chance the Pioneer anomaly gives us to validate current physical models by figuring out how we might explain this acceleration through hitherto unsuspected processes, perhaps aboard the spacecraft itself. Either way you look at it, the Pioneer anomaly has deserved the attention it has received, and now a new paper emerges to take a crack at resolving the issue once and for all. Frederico Francisco (Instituto Superior Técnico, Lisbon) and colleagues have revisited the question of whether heat that is emitted and reflected aboard the spacecraft could account for the anomalous acceleration. Francisco’s team had accounted for between 33% and 67% of the acceleration in a thermal model they developed in 2008. The...

Yesterday I planned to write a review of Richard Panek's The 4 Percent Universe (Houghton Mifflin Harcourt, 2011), a fascinating look at dark matter and dark energy and the current state of our research into them. Panek is an excellent writer with an eye for detail and the human touch. He gets you into the thick of scientific controversy and brings out not only the issues but the personalities involved -- the good news is that the personalities, particularly in the case of dark energy, didn't seem to matter, because the major players reached the same conclusion. But as I worked on the review, I found myself focusing on the dark energy side of the book, especially the question of how dark energy findings could be supported by other evidence. So while Panek spends an equal amount of time with dark matter, and runs through everything from dark matter candidates (WIMPs, MACHOs, etc.) to attempts to use gravitational lensing to constrain the population of dark objects (not to mention the...

Speaking at last fall's International Astronautical Congress in Prague, Tau Zero founder Marc Millis offered a condensed summary of the present state of the art in advanced propulsion physics, summarizing a variety of approaches and next-step questions from the book he co-edited with Eric Davis called Frontiers of Propulsion Science (2009). He's now written a paper based on the presentation. It's a useful distillation of an extremely detailed work (739 pages) and well worth scanning now that Millis has made it available on the arXiv site. Quite a few propulsion concepts have gone through the early stages of the scientific process, with problems defined, data being collected and hypotheses formulated, and Millis also refers to those cases where ideas have progressed into the testing stage. He's fascinated with the idea of using investigations into broad issues of cosmology to focus in on something far more utilitarian, the possible relevance of new observations for spaceflight. From...

New work at the University of Michigan, now written up in Physical Review Letters, discusses the possibility of producing matter and antimatter from the vacuum. The idea is that a high-energy electron beam combined with an intense laser pulse can pull matter and antimatter components out of the vacuum, creating a cascade of additional particles and anti-particles. UM Engineering research scientist Igor Sokolov has this to say about the theoretical study: "We can now calculate how, from a single electron, several hundred particles can be produced. We believe this happens in nature near pulsars and neutron stars..." That would make the vacuum a lively place indeed, as Sokolov acknowledges: "It is better to say, following theoretical physicist Paul Dirac, that a vacuum, or nothing, is the combination of matter and antimatter—particles and antiparticles.Their density is tremendous, but we cannot perceive any of them because their observable effects entirely cancel each other out."...

Abell 1689 is one of the most massive clusters of galaxies known, making it a superb venue for the study of dark matter. That's because the cluster, some 2.2 billion light years away, creates gravitational lensing that magnifies and distorts the light from galaxies far beyond it. Astronomers used Abell 1689 in 2008 to identify one of the youngest and brightest galaxies ever seen, a galaxy in existence a mere 700 million years after the beginning of the universe. That find, A1689-zD1, turned out to be ablaze with star formation in an era when stars were only beginning to emerge. New Hubble studies have now used Abell 1689 yet again to make some of the most detailed maps yet of dark matter. The idea is this: The cluster's gravitational lensing bends and amplifies the light of objects beyond it. The researchers, led by JPL's Dan Coe, go to work on the distorted images that result, figuring out the mass it would take to produce them. If the galaxies we see in the cluster were the sole...

While lamenting the budgetary problems of space-based missions like SIM -- the Space Interferometry Mission -- I often find myself noting in the same breath that technological advances have us doing things from the ground we used to think possible only from space. Make no mistake, we need to develop space-based interferometry for future studies of exoplanet atmospheres and their possible biomarkers. But it's gratifying that the next generation of ground-based telescopes using adaptive optics coupled with extremely large instruments like the Giant Magellan Telescope will also give us powerful tools for studying exoplanets. Image: An artist's rendering of the Giant Magellan Telescope in its enclosure. Credit: Giant Magellan Telescope Organization. The same holds true for another intriguing line of investigation. We've known about dark energy since the late '90s, when two groups -- the Supernova Cosmology Project and the High-z Supernova Search Team -- discovered that the expansion of...

by Richard Obousy Physicist Richard Obousy has long been fascinated with the Casimir force, dark energy, and the stability of higher dimensions. His dissertation at Baylor University, in fact, focused on the possibility that dark energy could be an artifact of Casimir energy in extra dimensions. Now project leader of Project Icarus, Obousy here takes a look at a recent paper by Igor Smolyaninov (University of Maryland) that explores the Alcubierre 'warp drive' concept from the standpoint of material parameters. Can warp drive be modeled in the laboratory, and under what constraints? Finding the answer may yield new information about this exotic concept. As Smolyaninov says in his paper, "We will find out what kind of metamaterial geometry is needed to emulate a laboratory model of the warp drive, so that we can build more understanding of the physics involved." Fermat's principle dictates that light rays follow the shortest optical paths in media. Effectively they are geodesics, and...

by Richard Obousy Physicist Richard Obousy here takes a look at an intriguing new paper by Mike McCulloch, a researcher at Plymouth University. In addition to his work in theoretical physics and warp drive possibilities, Obousy is current project leader and primary propulsion design lead for Project Icarus, a joint venture between the British Interplanetary Society and the Tau Zero Foundation to re-think the original Project Daedalus starship design. In the review below, Obousy places McCulloch's work on the Pioneer anomaly in the context of current thinking on dark matter, dark energy and the nature of mass. Does the Higgs field explain inertial mass, or are there alternatives? Read on. Few areas of research have garnered as much attention from both the public and scientific communities as those of dark energy and dark matter - and for good reason. Both terms stem from observations of the physical universe that, simply put, don't belong within the well-understood framework of known...

Time travel holds such perennial fascination that even though its relationship with interstellar issues is slim, I can't resist reporting on new ideas about it. John Cramer's time experiments seem stuck in limbo, but now we have new work from Seth Lloyd (MIT) and colleagues about one way out of the paradoxes time travel seemingly creates. The 'grandfather paradox,' returning to the past to kill your own grandfather and thus causing your future self not to exist, seems inevitable if we grant the existence of what are called 'closed timelike curves' (CTCs), the paths through spacetime that would let a time traveler interact with his or her self in the past. Ways Around Paradox Lloyd's team gets past that problem by describing a particular version of closed timelike curves formed with what is called 'post-selection.' The idea is to describe these CTCs in terms of quantum mechanics, starting with the assumption that time travel is a communications channel from the future to the past. Is...

Getting a handle on dark energy is one of the great goals of modern physics. But understanding what it is that seems to be accelerating the expansion of the universe depends upon the accuracy of our measurements. We can study this acceleration by looking at the behavior of Type Ia supernovae, which can be used as 'standard candles' -- the distance to a galaxy can be measured because the visual magnitude of this type of supernova depends on its distance. But how reliable are our standard candles? New work confirms the usefulness of these stellar events while explaining why some supernovae can look different from others. A Type Ia supernova occurs when a white dwarf gathers material from a nearby companion star and approaches the Chandrasekhar limit (about 1.38 solar masses), at which point the pressure and density have grown beyond the point that the star can support its own weight. Various processes have been invoked to explain the details, but while these supernovae seem alike, some...

The discovery that the universe's expansion is accelerating has led some to wonder whether General Relativity breaks down at large scales. But new work by Fabian Schmidt and colleagues at Caltech seems to play down a rival theory known, economically enough, as f(R). If, under General Relativity, we see dark energy in terms of a cosmological constant, and thus view it as the energy of empty space, f(R) takes another tack, seeing the cosmic acceleration as the result of a necessary modification of gravitational theory. This effect would play a role in the way matter grows over time to become galaxy clusters, and that leads to a useful way to test the theory. What Schmidt and team did was to take mass estimates of 49 galaxy clusters based on observations from the Chandra X-ray Observatory, comparing them with the predictions of theory and raw data from supernova studies, the cosmic microwave background and the large-scale distribution of galaxies. Compellingly, they found no difference...

Yesterday's look at black holes and their potential role in generating energy for advanced civilizations flows naturally into newly released work from Xavier Hernandez and William Lee (National Autonomous University of Mexico). The astronomers have been studying how dark matter behaves in the vicinity of black holes, simulating the way early galaxies would have interacted with it. Current theory suggests that clumps of dark matter drew together gas that eventually became the stars and galaxies we see around us in the cosmos. How to study material that is invisible save for its gravitational influence? Its effect on gravitational lensing is one way, but Hernandez and Lee have found another. The duo looked for clues in the massive black holes now thought to be at the center of most large galaxies. Assuming such black holes are common, then large haloes of dark matter have coexisted with massive black holes over most of the history of the universe. It follows that part of the growth of...

by Adam Crowl Louis Crane's work at Kansas State University caught my eye some time back, but I was uncomfortable trying to explain it when I knew polymath Adam Crowl had so much better insight into Crane's thinking than I did. One thing led to another, and now we can get an overview of Crane's thoughts on black holes and starships from Adam himself. As a source of power, an artificially created black hole dwarfs alternatives, but the most intriguing possibility here is that a sufficiently advanced civilization might be able to use such a power source to propel a starship. Is forty years to Alpha Centauri a reasonable expectation with such technology? Read on. Infinities in physics are usually a sign that something has gone wrong with theory. Towards the end of the 19th Century classical physics when applied to the heat emission from a uniformly heated cavity predicted an infinite amount of ultraviolet emissions - the so-called "ultraviolet catastrophe." In 1900 Max Planck solved the...

Yesterday's trip to the dark side involved the so-called 'dark flow,' the apparent motion of galactic clusters along a path in the direction of the constellations Centaurus and Hydra. Today we look at two other dark conjectures -- dark matter and dark energy. Are both a part of the universe we observe, or can we do away with them by clever manipulation of Einstein's theory of general relativity? The latest word, from an international team of researchers studying the clustering of more than 70,000 galaxies, is that GR seems to have passed yet another test. This is useful stuff, because one of the implications is that dark matter is the most likely explanation of the movement of galaxies and galaxy clusters as they seem to respond to an unseen mass. The possibility of dark matter was noted as long ago as 1933 by Fritz Zwicky, who studied the average mass of galaxies within the Coma cluster and obtained a value much higher than expected from their luminosity. Later studies of individual...