Can measuring the positions and velocities of thousands of galaxies provide insight into the nature of dark energy? If so, we may have found a way to study what is perhaps the most puzzling question in astrophysics, the discovery that the expansion of the universe is proceeding faster today than it did in the past. Armchair theorists love dark energy because we know so little about it, and I routinely get e-mails offering to tell me exactly what dark energy is, few of which have any bearing on current observation or theory. But that's the way of mysteries -- they incite comment -- and as mysteries go, dark energy is a big one, perhaps the biggest now stirring the astrophysical cauldron. If we assume a dark energy producing a check on the gravitational pull of all matter in the cosmos, we've got the attention not just of cosmologists but propulsion theorists, who would love to find out how such a repulsive force might work. And if there is no such thing as dark energy, then...

Because dark matter has never been directly observed, we're left trying to figure it out using deductions based on its presumed effects on visible matter. Seven dwarf satellite galaxies of the Milky Way -- Carina, Draco, Fornax, Leo I, Leo II, Sculptor and Sextans -- offer a case in point. Stars in these galaxies do not move more slowly the farther they are from their galaxy's core. Is dark matter the explanation? Mario Mateo (University of Michigan) has been studying the velocity of almost 7,000 stars in the seven dwarfs. His observations lead to the same kind of deduction already been made for larger spiral galaxies, that the matter we see does not account for the apparent distribution of mass throughout the galaxy. All that, of course, depends upon subjecting these observations to established theory. Mateo colleague Matthew Walker (now at the University of Cambridge) puts it this way: "We have more than doubled the amount of data having to do with these galaxies, and that allows...

Fifty years ago, our understanding of space included only some of the properties we now find most intriguing from the standpoint not only of physics but also of potential propulsion. Dark energy was not suspected then, while Fritz Zwicky's inference of dark matter (1933) wouldn't really inspire a wave of investigations until the 1970's. The presence of the quantum fluctuations that would later be dubbed Zero Point Energy had only recently been examined. For that matter, the cosmic microwave background was still almost a decade from discovery. Knowing that such properties exist out there in the cosmos offers the potential of future technologies that might be able to make use of them. But clearly, we are a long way from understanding whether or if such phenomena could eventually be harnessed. Just how far becomes apparent every time we get new dark energy news, as we recently did from the University of Toronto, where astronomers studying supernovae in nearby galaxies found when...

Saul Perlmutter, Brian Schmidt and their respective teams received the Gruber Cosmology Prize last Friday at the University of Cambridge. Doubtless the awards will keep coming, for these are the researchers who discovered, more or less simultaneously, that the expansion of the universe was accelerating. That, in turn, gives us a look at the far future, suggesting that the universe will expand faster and faster forever. It hasn't even been a decade since the discovery was announced, but now we routinely discuss a dark energy force that seems to account for three-quarters of the density of our universe, a dazzling notion that recapitulates Einstein's cosmological constant and humbles us with the thought that, between dark energy and dark matter, we see only four percent of what is actually out there. Needless to say, interstellar theorists note with interest the idea of an effect that seems to oppose gravity itself. If such things exist, will we one day make enough sense of them to...

We'd like to know a lot more about neutron stars. They're doubtless the home of exotic matter of the sort we're unable to create in any laboratory, and their extraordinary density leads to conditions in the space around them that are, shall we say, extreme. Gases whipping around three neutron stars at forty percent of the speed of light have now been used to take measurements of their diameter and mass. Figure out the properties of such gases and you've nailed down a maximum size for the diameter of the neutron star Serpens X-1, for example, a figure that turns out to be between 18 and 20.5 miles across. A team led by Edward Cackett (University of Michigan) looked at the spectral lines from hot iron atoms around Serpens X-1 and two other neutron star binaries, GX 349+2, and 4U 1820-30. Independent work by Sudip Bhattacharyya and team (NASA GSFC) bolsters Cackett's results and demonstrates the efficacy of the method. Image: Many neutron stars are accompanied by a companion star, as...

If you had a device that could manipulate the expansion of spacetime, would you have the makings of a stardrive? Miguel Alcubierre's 'warp drive' concept is based on something like this. The physicist's 1994 paper points out that the speed of light constraint applies to objects moving within spacetime, but makes no prediction about how fast spacetime itself can move. Inflation theories draw on the same idea, with the early universe suddenly expanding at rates far surpassing light speed. So think about contracting space in front of your vehicle while creating more space behind it. Distorted spacetime carries the starship along at fantastic velocities while violating no principle dear to Einstein. The trick, of course, is energy, the necessary amount of which has been discussed in various papers. As far as I know, no one has been able to get the figure down below the total energy output of a Sun-like star, but that's a big reduction over earlier views that it would take all the energy...

Can photons move faster than the speed of light? You wouldn't think so, not if the name 'Einstein' has resonance, but Günter Nimtz and Alfons Stahlhofen (University of Koblenz) have been working on so-called quantum tunneling, joining two glass prisms and feeding microwave light into them. Tunneling occurs when a particle jumps an apparently uncrossable gap, and that's just what the team's microwave photons appear to have done, at least a few of them, when the prisms were separated. The bulk of the microwaves were reflected by the first prism. New Scientist will soon be reporting on this story, which picks up on the German researchers' recent paper. The tunneling photons seem to have reached the detector at the same time that their non-tunneling cousins did, suggesting movement far beyond the speed of light. The tunneling time evidently did not change when the prisms were pulled further apart. Is this a violaton of relativity? Perhaps not. Note this from the New Scientist story,...

If anything ever seemed completely unknowable, it's the answer to the question of what existed 'before' the Big Bang. But it's an issue laden with unusual interest. If a previous universe collapsed in a 'Big Crunch,' will that somehow become the fate of our own? Now a research team working under Martin Bojowald (Pennsylvania State) is developing its own answers to these questions, relying on the theory known as quantum loop gravity. The grand goal of unifying Einstein's General Relativity with the perplexing world of quantum mechanics is necessary but highly elusive. We need some way to look at the all but inconceivable energies that must have dominated the universe in its earliest period. And if you accept the idea that quantum loop gravity can do the job (it flows out of Penn State's Institute for Gravitational Physics and Geometry), then the Big Bang doesn't close off all knowledge of what went before. Bojowald and team talk about the 'Big Bounce,' a time when gravity becomes so...

Everybody loves a mystery, and the one surrounding Pioneer has everything going for it, an unusual effect observed via two of the most distant spacecraft ever launched. Both Pioneer 10 and 11 are slowing a bit more than expected as they move through the outer reaches of the Solar System. Explanations range from a variety of on-board causes to suggestions that our understanding of gravity itself needs an upgrade. NASA's Slava Turyshev, as noted in this New Scientist story, is compiling data from the spacecraft that had previously been inaccessible due to data formats and media incompatible with modern equipment. Turyshev's work may take a year to complete, but it holds the promise of nailing what many think to be the probable cause of the anomaly: heat from the RTGs (radioisotope thermoelectric generators) that provide power for the probes. Asymmetrical radiation of that heat just might do the trick. Meanwhile, New Scientist also gets into far more exotic possibilities, noting that...

When you've read Analog as long as I have -- and I date back to the days when it was named Astounding -- you develop a real fondness for some of the primary players. That's one reason I'm glad to hear the good news about John Cramer's time travel experiment, which has received enough private donations to be pursued. Cramer's 'Alternate View' columns have been running in the magazine since 1984, covering everything from cosmology to space drives and quantum mechanics. I've always admired his clear, straightforward style. A physicist at the University of Washington, Cramer caught the attention of the press in recent months by discussing his hopes of testing the idea of quantum retrocausality. Here we're in the domain of what Cramer calls the Transactional Interpretation, in which the processes of quantum mechanics involve waves traveling both forward and backward in time. His experiment, which may begin as early as next month, will test whether photons can communicate in reverse time....

If we ever develop a true 'warp drive' that can take us to the stars well within a human lifetime, we'll probably look back at Miguel Alcubierre as the theorist who took a science fictional idea fully into the realm of scientific calculation. The physicist's 1994 paper (reference below) suggests that manipulating the spacetime continuum itself could allow a spacecraft to move within a 'bubble' enclosed by the warp. It would never break the light barrier but would ride on the spacetime distortion to arrive at its destination as if it had. "A propulsion mechanism based on such a local distortion of spacetime," wrote Alcubierre, "just begs to be given the familiar name of the 'warp drive' of science fiction." It's quite a notion, isn't it? In essence, you want to create more spacetime behind your bubble while contracting what's in front of it. The British Interplanetary Society notes that Alcubierre's original paper has inspired about fifty publications probing the intricacies of the...

Traveling to the planets takes big money and we've been part of the squabbing over where NASA money in particular ought to be allocated. But what about projects that take small money? The term is relative, of course, but John Cramer (University of Washington) thinks $20,000 should suffice to run his experiment in time travel, and with NASA's Institute for Advanced Concepts now shutting down, he's having a hard time raising it. This Seattle Post-Intelligencer story has more. We've looked at Cramer's work before, but a brief summary is in order. It involves Einstein's 'spooky action at a distance,' the so-called Einstein-Podolsky-Rosen effect. Quantum entanglement seems to mean that two entangled particles influence each other no matter how far distant in space. That action appears to be instantaneous, which introduces the paradoxical outcome of suggesting that something can communicate faster than the speed of light. Einstein, of course, would say that's flat out impossible. Quantum...

We've just been discussing extraordinarily reflective mirrors for advanced propulsion. Here's the inverse, in a story from ScienceNOW: Scientists have created the world's first film that casts practically no reflection. A vast improvement over current nonreflective materials, the new technology could revolutionize solar cells, intensify light-emitting diodes, and possibly help solve mysteries in quantum mechanics by mimicking a "black body," an object that absorbs all light. The new coating reflects no light across much of the visual spectrum. This work, done at Rensselaer Polytechnic Institute, seems to have enormous potential for increasing solar cell efficiency. Much more here.

A device called a Photonic Laser Thruster is making news since a December demonstration of the technology by its inventor, Young Bae. The founder of the Bae Institute in Tustin CA, Bae has pursued antimatter and fusion research for twenty years at places like SRI International and Brookhaven National Laboratory. His current work on photon thrust is raising some eyebrows, as noted in this news release from the Institute, which quotes the Air Force Research Laboratory's Franklin Mead: "I attended Dr. Bae's presentation about his PLT demonstration and measurement of photon thrust here at AFRL. It was pretty incredible stuff and to my knowledge, I don't think anyone has done this before. It has generated a lot of interest around here." In one form or another, something called a 'photon drive' has been in the back of inventors' minds since the days of the German researcher Eugen Sänger, who published a designed he called a 'photon rocket' that would use gamma rays produced by the...

Can we find and actually traverse a wormhole? Crowlspace looks at the possibilities and links to a paper by Nikolai Kardashev that we'll be examining here in the next week or so. A snippet: Relativity gives no clear indication of where wormholes end. They might link to other places (and times) in our Universe or in other Universes. When the worm-ways of the Universe are finally explored there will be a whole new breed of adventurers required to travel to their far-ends, risking being lost in a wholly other Universe and time. After hardy explorers have mapped the wormhole network of the Universe what will happen then? A provocative scenario indeed! Read the whole thing here.

A recent mention of Paul Davies reminds me (belatedly, to be sure) to point you to "We Were Meant to Be Here," an interview Phillip Adams conducted with the physicist on ABC Radio National. The occasion was Davies 60th birthday last June, the conversation's title reflective of the usual Davies range across the deepest issues of life in the cosmos. Davies, formerly at Macquarie University, has left Australia and is now active at Arizona State, where he is establishing the Institute for Fundamental Concepts in Science. Other good audio is available at Davies' site. Also, a review of his The Goldilocks Enigma: Why is the Universe Just Right for Life? (Allen Lane, 2006) is available here.

Expansion, turnaround, contraction and bounce. Those are the four components of a new model of the universe created by researchers at the University of North Carolina at Chapel Hill. Their work offers an alternative to the Big Bang theories in the marketplace and sets up a cyclical progression in which an infinite number of independent universes emerge from what's left of matter just before the end of time. Tough going, this. But think of the universe's vast expansion pushing everything progressively further out until all matter disintegrates. This is the turnaround point, and it is here that each fragmented 'patch' of what had been matter collapses and contracts. "We discuss contraction which occurs with a very much smaller universe than in expansion," write the researchers, "and with almost vanishing entropy because it is assumed empty of dust, matter and black holes." The key is that this collapse occurs individually, so that rather than causing the Big Bang to run in reverse,...