7. Physics News from the Web
Items selected from the bulletins of the Institute of Physics (UK) and the American Institute of Physics.
a) Galaxies pin down dark energy
b) Neutrinos could detect secret fission reactors
c) Beetle beauty captured in silicon
d) Penrose claims to have glimpsed universe before Big Bang
a) Galaxies pin down dark energy
http://physicsworld.com/cws/article/news/44468
A new way of measuring the geometry of the universe confirms that dark energy dominates the cosmos and bolsters the idea that this unusual form of energy is described by Einstein's cosmological constant. The technique, developed by physicists in France, involves a relatively easy measurement of the orientation of distant pairs of galaxies.
Over the past decade or so, several kinds of observation, such as measurements of the distances of remote supernovae, have provided strong evidence that the expansion of the universe is accelerating. Cosmologists believe that this expansion is being driven by what is known as dark energy – a substance with negative pressure that opposes the pull of gravity. Unfortunately, however, they have little idea of what dark energy actually is, having been unable to measure its properties well enough to distinguish between rival hypotheses.
b) Neutrinos could detect secret fission reactors
http://physicsworld.com/cws/article/news/44411
Oil tankers fitted with neutrino detectors, hundreds of thousands of tonnes in mass, could be floated offshore to check for undeclared nuclear fission reactors. That's the idea of physicists in France, who have proposed the Secret Neutrino Interactions Finder (SNIF) as a way of enforcing the nuclear non-proliferation treaty – although some experts doubt its feasibility.
Currently, fission reactors over the world are monitored by the United Nations' International Atomic Energy Agency (IAEA), based in Vienna. The IAEA uses several "near-field" tools to make sure reactors are running legally, from CCTV-type cameras to metallic or fibre-optic networks that can detect when fuel is being loaded. In some cases, the agency installs thermal monitors to check that reactors are not being operated for too long, as might be required for the production of bomb-making plutonium.
c) Beetle beauty captured in silicon
http://physicsworld.com/cws/article/news/44389
Researchers in Canada have created a new material that mimics the brilliant iridescent colours seen in beetle shells. As the eye-catching effect can be switched off with the simple addition of water, the researchers believe their new material could lead to applications including "smart windows".
Structural colours, such as those on beetle shells and butterfly wings, differ from traditional pigments because the colour results from the interaction of light with periodic structures on the surface of the material. In certain biological materials, including the shells of scarab beetles, these exoskeletons take on a twisted or "chiral" structure, which causes reflected light to emerge circularly polarized.
d) Penrose claims to have glimpsed universe before Big Bang
http://physicsworld.com/cws/article/news/44388
Circular patterns within the cosmic microwave background suggest that space and time did not come into being at the Big Bang but that our universe in fact continually cycles through a series of "aeons". That is the sensational claim being made by University of Oxford theoretical physicist Roger Penrose, who says that data collected by NASA's WMAP satellite support his idea of "conformal cyclic cosmology". This claim is bound to prove controversial, however, because it opposes the widely accepted inflationary model of cosmology.
According to inflationary theory, the universe started from a point of infinite density known as the Big Bang about 13.7 billion years ago, expanded extremely rapidly for a fraction of a second and has continued to expand much more slowly ever since, during which time stars, planets and ultimately humans have emerged. That expansion is now believed to be accelerating and is expected to result in a cold, uniform, featureless universe.
Penrose, however, takes issue with the inflationary picture and in particular believes it cannot account for the very low entropy state in which the universe was believed to have been born – an extremely high degree of order that made complex matter possible. He does not believe that space and time came into existence at the moment of the Big Bang but that the Big Bang was in fact just one in a series of many, with each big bang marking the start of a new "aeon" in the history of the universe.