Place two parallel plates close to each other in vacuum and a strange thing happens, as Dutch physicist Hendrik Casimir learned. The Casimir effect that he described draws the plates together, an effect that was successfully measured first in 1958 and, with greater precision, by Steve Lamoreaux in 1996. The effect becomes important at distances less than 100 nanometers. And if it seems like little more than a curiosity, be aware that Robert Forward looked at the possibilities of engineering to put this energy to use in an intriguing 1984 paper. That paper ("Extracting Electrical Energy from the Vacuum by Cohesion of Charged Foliated Conductors" -- see reference below) looks at the attraction between two parallel plates in a vacuum as the result of vacuum fluctuations of the electromagnetic field. As the two plates close on each other, longer electromagnetic waves no longer fit between them. The result: The total energy between the plates is less than the amount pushing them together...

"It's no longer completely crazy to ask what happened before the Big Bang," says Caltech's Marc Kamionkowski. A good thing, too, for this is an absorbing subject, one I've been interested in ever since reading Poul Anderson's 1971 novel Tau Zero, in which the crew of the runaway starship Leonora Christine punches through into another universe. That novel assumed a cyclic universe, a collapse and a rebound, naturally making one ask whether a universe hadn't existed before our own. If so, could we learn anything about it? I would always have assumed the answer is no, but Kamionkowski's work, and that of collaborators Adrienne Erickcek and Sean Carroll, at least opens the possibility that we might see an 'imprint' of that earlier universe in data we can collect today. The work grows out of measurements of the cosmic microwave background (CMB), as examined by the Wilkinson Microwave Anisotropy Probe. Temperature differences in the CMB can be used to study the theory of inflation, the...

The best news about recent dark energy findings is that they offer new ways to study the phenomenon. It's only been ten years since dark energy -- thought to be the origin of the universe's accelerating expansion -- emerged from the study of supernovae. Simply put, these exploding stars weren't slowing as they moved away from us, but were actually speeding up. It was a controversial result, to say the least, and one which remains one of science's primary riddles. But Chandra X-ray Observatory observations may be providing additional clues. The team on this work is led by Alexey Vikhlinin (Harvard-Smithsonian Center for Astrophysics), its effort focused on galactic clusters. A model of the cosmos that incorporates dark energy is the only thing that explains why these clusters have grown so slowly during the last five billion years, in what Vikhlinin calls "arrested development of the universe." Dark energy seems to be working against the gravitational forces that allow clusters to...

Planetary engineering on the largest scale might one day reveal itself to us through the observation of a Dyson sphere or other vast object created by an advanced civilization. But it's interesting to think about alternative strategies for using celestial energies, strategies that assume vast powers at the disposal of mankind as projected into the distant future. Thus an interesting proposal from the Swiss theorists M. Taube and W. Seifritz, who consider what to do about the Sun's eventual evolution into a planet-swallowing red giant. A Sunshade and a Planetary Shift Considering the possibilities of preserving the Earth during the Sun's transition into a brighter and much larger object, the authors discuss alternatives like raising the Earth's orbit to a safer distance or using a parasol to shield the planet from its rays. That might tide us over for a few billion years beyond the point where an unprotected Earth could survive as a habitable place. But the paper only begins here....

What is the unusual source of high-energy cosmic rays that has been discovered within 3000 light years of the Sun? Everyone loves a mystery, and this one has all the earmarks of a classic. The source was found by the Advanced Thin Ionization Calorimeter (ATIC) experiment, which was lofted to high altitude above Antarctica via helium-filled balloon. Behind the experiment was the goal of studying cosmic rays that are otherwise shielded from the surface by the Earth's atmosphere, but among the results was an unexpected finding. Cosmic ray electrons at 300 to 800 billion electron volts are simply too powerful to be regarded as standard fare, for these particles lose energy as they move through the galaxy. That means that a study like this should see fewer electrons at higher energies. Nearby sources, on the other hand, stand out, making it clear there is what principal investigator John Wefel (Louisiana State) calls "...a very interesting object near our solar system waiting to be...

by Kimberly Trent Here we depart briefly from the norm by looking at the work of Kimberly Trent, a graduate student in the Applied Physics Program at the University of Michigan. Working as an intern with Marc Millis at NASA's Glenn Research Center, Trent examined the broad issues of advanced propulsion and focused on a research topic that takes off on a Robert Forward idea from the 1960s. The goal: To develop a propulsion concept involving non-Newtonian frame-dragging effects, which Trent studies in relation to the work of Martin Tajmar. The details follow, in an article designed to show one student's involvement in the kind of studies Tau Zero hopes to encourage at other institutions. This past summer, I interned at the NASA Glenn Research Center in Cleveland, OH through the NASA Academy program. My individual research project was in theoretical spacecraft propulsion. This area involves research into devices and concepts such as space drives, warp drives, gravity control, and...

What could be causing gamma-ray photons to be streaming from the galactic core with a precise energy of 511 keV (8 X 10-14 joules)? It's an interesting question, one tackled by Ian O'Neill on his astroENGINE site, as posted by 21st Century Waves in this week's Carnival of Space. O'Neill notes the defining nature of this energy level, which turns out to be the exact rest mass energy of a positron, the antimatter equivalent of an electron. That fact suggests the annihilation of positrons in the galactic center, but what's causing it? The usual suspects just don't fit, as O'Neill is quick to note: The first thing that comes to mind is a gamma-ray burst, produced when a massive star dies and collapses as a supernova. But this is short-lived and not sustained. How about the supermassive black hole sitting in the middle of the Milky Way's galactic nucleus? This theory was recently discussed on Astroengine, but the production of antimatter (i.e. positrons) is more of a slow leak than...

For those of you who don't see Spaceflight, a magazine published by the British Interplanetary Society, it may be useful to know that an article by Richard Obousy and Gerald Cleaver (Baylor University) on warp drive theory from the April issue is now available on the arXiv server. This material was presented at the November, 2007 symposium held by the BIS in London. Kelvin Long, who organized the session, had earlier passed along several documents from the proceedings that we looked at here, and also wrote up the duo's ideas in the same issue of Spaceflight. But let's backtrack a minute to Miguel Alcubierre's 1994 paper, which demonstrated that it would be possible -- within the context of General Relativity -- to envision a space drive that could get you to your destination in a time shorter than it would take light itself to get there. Contracting space in front of the craft while inflating it behind, the drive is permissible because the starship itself would not be going faster...

The continuing activity on the Practical Positronic Rocket threads has made it clear that we need a place for speculations that do not flow out of particular posts. What we're aiming at down the road is to implement discussion software that will make such threads easy to follow and contribute to, but for now we're dealing with weblog software that is not optimized for the task. Hence this thread, which is open to rational theorizing about interstellar issues in comments that do not reflect content found in the posts elsewhere on the site. If your idea is 'blue sky' and not related to a particular post, this is the place to put it.

Putting the General Theory of Relativity to the test gives us a chance to look once again at Einstein's understanding of gravity to see how it conforms with reality. We know the theory is incomplete because it doesn't tell us what happens to gravity at the subatomic level. But on the macro-scale of the larger universe, General Relativity is again confirmed in new work involving an unusual pair of neutron stars. The work, performed by an international team using the Jodrell Bank telescope in Cheshire and the Green Bank instrument in West Virginia, examined two pulsars that orbit each other, the only known case out of some 1700 identified pulsars where two are found in such a configuration. Emitting beams of radio waves, the two stars offer another observational opportunity -- their orbital plane lines up nearly with their line of sight to Earth. The result: An eclipsing signal as one pulsar moves behind the ionized gas surrounding the other. The fortuitious lineup makes possible an...

Mention the term 'warp drive' and the name Miguel Alcubierre immediately comes to mind. But it was only recently that the Mexican physicist's connection to the idea arose. His 1994 paper, written while he was at the University of Wales, took what had been a science fiction concept (most famously, I suppose, in Star Trek) and extended it into the realm of serious science. Not that Alcubierre put forth a realistic proposal for building a starship that could travel faster than light. What he was doing was the essential first step in such study, trying to demonstrate that FTL travel times could be achieved within the context of General Relativity. You would think that flying to Alpha Centauri in, say, a few days would be a gross violation of Einstein's laws, but this may not be the case. What Alcubierre proposed was that warp drive could function not by acceleration through space, but by the acceleration of space itself. Interestingly, while there is a seemingly iron-clad prohibition...

Whether or not information can truly be lost is a major issue in the study of black holes. Stephen Hawking's work in the 1970s offered a mechanism for black hole evaporation. Vacuum fluctuations would cause a particle and its antiparticle to appear just beyond the black hole's event horizon, with one of the two falling into the black hole while the other escaped. A 'virtual' particle, in other words, would become a real particle. Black holes, in this view, would be able to lose mass through quantum effects, a theory that the soon to be launched GLAST satellite will try to confirm. But ingenious as Hawking's theory was, it produced a conundrum. Black holes that fail to gain more matter will eventually vanish, with information, such as the identity of matter drawn into the black hole, becoming permanently lost. It being a linchpin of quantum mechanics that information cannot be lost, this presents a problem. Enough of one that physicist John Preskill (Caltech) bet Hawking and Kip...

Physicists have recently theorized that the merger of two black holes would create gravitational waves that could eject the resultant object from its galaxy. Now such a black hole event has been observed for the first time. Theory predicted that the gravitational waves would be emitted primarily in one direction, pushing the newly enlarged black hole in the opposite, and that is what we seem to be looking at, according to scientists at the Max Planck Institute for Extraterrestrial Physics (MPE). We can't see black holes themselves, nor have we yet directly detected gravitational waves. But we can observe the interactions around black holes, in this case the broad emission lines of gases carried with the recoiling black hole as it exits its galaxy, which contrast with the narrow emission lines of the gases the object left behind. These data allowed the object's speed -- a scorching 2650 kilometers per second -- to be measured. The recoil caused by the merger is pushing the black hole,...

Dark matter is interesting in its own right, a mysterious 'something' that according to WMAP data must account for 23 percent of the universe (the breakdown now thought to be 72 percent dark energy, 23 percent dark matter, 4.6 percent atoms and less than 1 percent neutrinos). From a propulsion standpoint, dark matter intrigues us because it may represent a reaction mass conceivably useful for future space flight. It's also Nobel Prize territory for the team that identifies it, which is why so many teams are looking, with one team's provocative results drawing criticism. The Italian and Chinese physicists on the DAMA Project have held out since 2000 for their claim that they are detecting dark matter beneath the Gran Sasso mountain in Italy. The modulation is yearly and could represent the Earth's motion through a dark matter stream as it orbits the Sun. The larger DAMA/LIBRA experiment now reaffirms the phenomenon, which appears as flashes in the team's sodium iodide detector. With...

How things change over time has never been as strikingly demonstrated as in recent findings. If you go back to the distant era when the universe was only 380,000 years old, you find that neutrinos made up fully ten percent of the universe. Given that these sub-atomic particles moving at nearly the speed of light are so abundant today that millions of them pass through us every second, you'd think they compose a substantial portion of today's universe, but they actually account for less than one percent. And the change in neutrino ratio is only the beginning. For according to five years of recently released data from the Wilkinson Microwave Anisotropy Probe (WMAP), the early universe was composed of 12 percent atoms, 15 percent photons, almost no dark energy, and 63 percent dark matter. The contrast is stark, given WMAP estimates of the current cosmos: 4.6 percent atoms, 23 percent dark matter, 72 percent dark energy. And, of course, those greatly diminished neutrinos. Image: WMAP...

The more we learn about gravitational lensing, the more it becomes clear how pervasive the phenomenon must be as mass and spacetime interact throughout the cosmos. The most recent findings produced by lensing effects now limn structures so large that they dwarf the galaxy we reside in. Recently detected dark matter filaments, up to 270 million light years in size, are 2000 times the size of the Milky Way, yet would remain unobserved were it not for advanced lensing investigative techniques. The astronomers behind this work, using data from the Canada-France-Hawaii Telescope Legacy Survey, took advantage of the fact that dark matter should deflect the light from distant galaxies as it travels towards us. The careful measurement of these often tiny effects required the development of new tools for image analysis, but these apparent filaments, sheets and clusters of dark matter seem to gibe with previous theoretical estimates. "Our observations extend the knowledge about the cosmic web...

When Hollywood met MIT last month in Cambridge, MA I suspect most of the students who jammed the on-campus lecture hall to discuss the new movie Jumper were thinking about Star Trek's famed transporters. After all, Jumper is a movie about a man who learns at a completely unexpected moment that he can teleport himself anywhere he wants to go. The Enterprise's transporters could get you to your destination in a hurry, too, and presumably invoked some of the same mechanisms, the gist of which were explained in the discussion by MIT physicists Max Tegmark and Edward Farhi, with Hollywood contribution by director Doug Liman and Hayden Christensen, respectively director and star of the film. What came to mind first for me, though, wasn't Star Trek but the Harry Harrison collection One Step from Earth (Macmillan, 1970). Harrison's stories wove together a future around the premise that beaming matter to destinations near and far would soon be invented. His book begins with the first...

Cornell aerospace engineer Mason Peck captured the attention of Centauri Dreams readers recently when Larry Klaes wrote up his ideas on modular spacecraft and self-assembly. Peck has talked about using the technology, which draws on a property of superconductors called magnetic flux pinning, to assemble or reconfigure structures in space without mechanical hardware. These are provocative concepts, and Dr. Peck has been kind enough to provide answers to questions from reader Christopher Bennett, beginning with whether or not his notions bear any resemblance to an idea long familiar in science fiction, the manipulation of objects by force fields. Here's what Bennett wondered about reconfigurable structures in space: "It sounds like what's being talked about here is something surprisingly similar to the old SF idea of building with forcefields. Do I understand this right?" Are we talking about creating clusters of unconnected components that are held rigidly in place by magnetic fields...