Physics

Dark energy. Even the name is intriguing. Isn’t it a line of cosmetics already? But the evidence base is getting murkier all the time. The conjecture, if true, would mean the density of dark energy in our universe cannot be constant, but must instead take a form called “quintessence” — an energy source that will gradually diminish over tens of billions of years. Several telescope experiments are underway now to more precisely probe whether the universe is expanding with a constant rate of acceleration, which would mean that as new space is created, a proportionate amount of new dark energy arises with it, or whether the cosmic acceleration is gradually changing, as in quintessence models. A discovery of quintessence would Read More ›

Philip Cunningham writes to note for us such moments in the literature: Abstract: (open access) Why life persists at the edge of chaos is a question at the very heart of evolution. Here we show that molecules taking part in biochemical processes from small molecules to proteins are critical quantum mechanically. Electronic Hamiltonians of biomolecules are tuned exactly to the critical point of the metal-insulator transition separating the Anderson localized insulator phase from the conducting disordered metal phase. Using tools from Random Matrix Theory we confirm that the energy level statistics of these biomolecules show the universal transitional distribution of the metal-insulator critical point and the wave functions are multifractals in accordance with the theory of Anderson transitions. The findings Read More ›

 In a review of science writer Anil Ananthaswamy’s Through Two Doors at Once: The Elegant Experiment That Captures the Enigma of Our Quantum Reality, science writer Philip Ball captured the essence of the sheer oddity of quantum mechanics: What’s odd is that the interference pattern remains — accumulating over many particle impacts — even if particles go through the slits one at a time. The particles seem to interfere with themselves. Odder, the pattern vanishes if we use a detector to measure which slit the particle goes through: it’s truly particle-like, with no more waviness. Oddest of all, that remains true if we delay the measurement until after the particle has traversed the slits (but before it hits the screen). Read More ›

From a review of The Equations of Life: The Hidden Rules Shaping Evolution by astrobiologist Chares Cockell, The book uses many examples of living things on our own planet, most convincingly the ladybug, to explain eloquently why everything from microbes to large animals are the way they are. For example, why does the ladybug not fall off a leaf? How does it manage to breathe without lungs? How does it survive winter or fly—considering its aerodynamics are very different from an airplane’s? Having shown that physical factors limit the solutions for life on this planet, Cockell extends the argument to extraterrestrial life. He expects us to find only carbon-based life elsewhere in the universe, which, he contends, is likely to Read More ›

Why do computers mean we never have to be humble again? We asked our physics color commentator, Rob Sheldon, about the recent deflation of the “expanding blueberry muffin” picture of the universe. That is, as one astrophysicist puts it “Just as cosmological measurements have became so precise that the value of the Hubble constant was expected to be known once and for all, it has been found instead that things don’t make sense.” Sheldon offers a little background: — — — Hubble’s constant is a calculation of the expansion rate of the universe by: a) measuring how far away something is (e.g., parsecs) b) measuring how fast it is moving away from us (e.g., kilometers/second) c) divide speed by distance Read More ›

And cosmologists race to win a “great cosmic bake-off” to produce a new one, says astrophysicist: Just as cosmological measurements have became so precise that the value of the Hubble constant was expected to be known once and for all, it has been found instead that things don’t make sense. Instead of one we now have two showstopping results. On the one side we have the new very precise measurements of the Cosmic Microwave Background – the afterglow of the Big Bang – from the Planck mission, that has measured the Hubble Constant to be about 46,200 miles per hour per million light years (or using cosmologists’ units 67.4 km/s/Mpc). On the other side we have new measurements of pulsating Read More ›

Recently, cosmologist Carlo Rovelli, author of The Order of Time, argued that time travel, especially into the future, can work. However, astrobiologist Caleb A. Scarf sees an insurmountable barrier, which he calls the “spatial problem”: Let’s take the Earth’s motion around the Sun. A month of orbit corresponds to moving in an arc of approximately 78 million kilometers. During that same period the entire solar system will have also moved approximately 600 million kilometers around our galaxy, and our entire Local Group of galaxies will have swept through about 1.7 billion kilometers of space relative to the cosmic microwave background. Not only do you need to traverse those kinds of distances, you need to get it correct to within a Read More ›

Further to Carlo Rovelli’s views on time travel (only a technological problem, not a scientific one) and the order of time in general,  views, as set out in The Order of Time, our color commentator Rob Sheldon offers, — If I can speculate about what goes on in physicist’s heads, this issue about time is an attempt to force symmetry on the universe. Sorta like the 2-yr old who wants to regularize irregular verbs. “Mommy not home; she goed to the store.” Einstein’s Special Relativity (SR) argued that time was a fourth dimension and should not be treated any differently than height, width, and length. To get the units right, one only needed to multiply time by the speed of light–c*t. Only Read More ›

Not a scientific one. Dan Falk interviews physicist Carlo Rovelli about “about the nature of time, whether it has a beginning and if humans might one day master time travel:” Could time travel ever be possible? Well, “time traveling” is what we do all our lives, isn’t it? But you mean, can we jump quickly to the past or to the future. Jumping to the far future is certainly possible. It’s only a technological problem, not a scientific one. One way is to move very fast. When you move fast, time passes very slowly for you — so if you could run fast enough around your house many times, you could do that in a time span which for you Read More ›

Modified gravity is a hypothesis (1983) that attempts to account for the gravitational pull that is otherwise attributed to dark matter (which has never been identified). From Sabine Hossenfelder, author of Lost in Math: How Beauty Leads Physics Astray, at : Which one is right? We still don’t know, though astrophysicists have been on the case since decades. Ruling out modified gravity is hard because it was invented to fit observed correlations, and this achievement is difficult to improve on. The idea which Milgrom came up with in 1983 was a simple model called Modified Newtonian Dynamics (MOND). It does a good job fitting the rotation curves of hundreds of observed galaxies, and in contrast to particle dark matter this model Read More ›

At Scientific American, John Horgan reprints his profile of  Bohm (1917-1992) shortly before his death, in which Bohm explains his view: Although he tried to make the world more sensible with his pilot-wave model, he also argued that complete clarity is impossible. He reached this conclusion after seeing an experiment on television, in which a drop of ink was squeezed onto a cylinder of glycerine. When the cylinder was rotated, the ink diffused through the glycerine in an apparently irreversible fashion. Its order seemed to have disintegrated. But when the direction of rotation was reversed, the ink gathered into a drop again. He was consistent: Bohm rejected the claim of physicists such as Hawking and Weinberg that physics can achieve a Read More ›

From ScienceDaily: One of the candidates for ‘dark energy’ is the symmetron field. Researchers have developed an experiment capable of measuring extremely small forces with the help of neutrons. The measurements could have provided pointers to the mysterious symmetrons, but the particles didn’t show up. This excludes the possibility of symmetrons in a broad parameter range. ‘Dark energy’ is going to have to be explained differently. One thing is certain: there’s something out there we don’t yet know. For years now scientists have been looking for “dark matter” or “dark energy” — with our current inventory of particles and forces in nature we just can’t explain major cosmological phenomena, such as why the universe is expanding at an ever faster Read More ›

From Mind Matters Today: Succinctly, researchers using Bell’s theoretical insight into quantum entanglement have shown that there are no deterministic local hidden variables. This means that the final state of entangled quantum particles is not determined by any variables in the initial state. Nature at its most fundamental level is indeterminate. The states of bound particles are not determined by any local variable at the moment of separation. Bell’s inequality and the experimental work that has followed on it conclusively demonstrate that quantum entanglement, and thus nature, is not determinate, at least locally. There remains the remote possibility of non-local determinism, but that view is considered fringe and is rejected by nearly all physicists working in the field. It is Read More ›

From science writer Bruce Dorminey at Forbes: Time may be running out on the search for the cosmos’ exotic dark matter. Decades after the first searches for dark matter’s hypothetical exotic particle counterparts, researchers are mostly at a loss to explain why there still has been no direct detection. That is, one that could explain why such unseen, dark matter particles only appear to weakly interact with normal matter. … McGaugh says one huge problem is that while dark matter theory is ‘confirmable’ it is not ‘falsifiable’ as a scientific theory should be. “There is no clear way to know [that] what you’re looking for — but failing to find — doesn’t exist at all,” said McGaugh. “If you’re convinced Read More ›