Science magazine reports: For decades, string theory promised a "theory of everything" that described all particles and forces as tiny vibrating strings. Physicists hoped it could also solve one of the field's deepest problems: reconciling quantum mechanics with gravity. But as string theory grew increasingly elaborate — and experimentally unreachable — many physicists lost hope. Now, some researchers are revisiting the theory from first principles. In a paper in press at Physical Review Letters, Clifford Cheung, a physicist at the California Institute of Technology, and colleagues lay out a small set of assumptions about the universe and show that they inevitably give rise to string theory.... Cheung's study, along with another one posted to arXiv in January, starts with two reasonably conservative assumptions: that the probabilities of all possible outcomes of an event add up to 100%, and that the laws of physics are consistent for observers moving at different speeds. Each group then posits additional assumptions that have not been borne out by observations. Cheung's analysis invokes "ultrasoftness," the idea that the probability of certain particle interactions drops off at a particular rate at high energies. The second study, led by University of Michigan physicist Henriette Elvang, instead assumes "supersymmetry," a maximal coupling between matter and forces. Both groups conclude the only theory that can satisfy their assumptions is one that looks like string theory... Cheung and Elvang stress that their aim is not to prove the inevitability of string theory. "I don't have a dog in the fight; I just work here," Cheung says. Rather, the goal is to explore the space of possible theories under rigid constraints — regardless of whether they reflect reality... The one thing the researchers all agree on is that the field would benefit from more alternative models to string theory. Cheung sees the agnostic, bottom-up exploration as a step in that direction. "You can either give up on the problem because it's too culturally toxic, or you can ask: If you want to find an alternative, what do you need?" he says. "Now, we know exactly what to do." Thanks to Slashdot reader sciencehabit for sharing the article.

Read more of this story at Slashdot.

(Permalink)

"Scientists have developed a solar desalination system that turns seawater into drinking water without creating environmentally damaging brine," reports ScienceDaily. "Special laser-textured metal panels use sunlight to evaporate water while automatically moving salt deposits away from the working surface, preventing clogging. The process was successfully tested with water from three oceans and can recover nearly all salts as solids. Those leftover materials could even become a source of valuable lithium for batteries." (The research team was led by University of Rochest professor Chunlei Guo and published their results in the journal Light: Science & Applications.) The University of Rochester has made an announcement: The technology uses solar panels made of black metal etched with femtosecond lasers to make the surface super light-absorbing and superwicking — or extremely attractive to water. The panels have a laser-treated active region that pulls a thin layer of water across the surface, absorbs nearly all solar radiation, distills the water, and deposits the leftover salts and minerals into the panel's untreated sides or "passive" region so that the salt does not clog the active region and disrupt continuous desalination... Guo's team precisely etched the black metal's grooves so the various salts and minerals in ocean water would simply slough off... [I]t extracts nearly 100 percent of the salts in solid form. This could not only produce an abundant supply of table salt, but it could also be used to extract more precious minerals, including lithium, which is used in the lithium-ion batteries that power electric vehicles and other electronics. In a related paper in the Journal of Materials Chemistry A, Guo and his colleagues show how they can use the same superwicking solar panels to separate lithium from the rest of other salts in desalination. Embedding nanoparticles made of hydrogen titanate in the tiny grooves of the black metal surface isolates the lithium from other salts and minerals...Using water samples from Great Salt Lake, the researchers extracted about 50 percent of the lithium from the salts left behind by the desalination process. Guo says now that the superwicking desalination technology has been demonstrated in proofs of concept on small-scale devices, he sees the technology inherently scalable, capable of improving global access to drinking water and building more sustainable supply chains for precious minerals. "The National Science Foundation, the Bill & Melinda Gates Foundation, and Worldwide Universities Network supported this research."

Read more of this story at Slashdot.