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Published in Physics World, 1 Oct 2012

Now that the Square Kilometre Array will be split between sites in Australia and southern Africa, Jon Cartwright reports that some technological trickery will be needed to make the world’s biggest telescope work

While the discovery of the Higgs boson at CERN’s Large Hadron Collider (LHC) may have been taking all the headlines of late, there is some truth in claiming that the machine is already the “big science” of old. In just four years’ time, construction is slated to begin on a new project that will dwarf the Franco–Swiss particle accelerator by comparison. That project is the Square Kilometre Array (SKA) – the world’s biggest and most sensitive radio telescope.

Physically, SKA will be larger than the LHC, ultimately spreading over thousands of kilometres in Africa and Australasia. It will be made up of thousands of radio dishes and millions of radio antennas. To sort through the troves of data, it will need the fastest supercomputer on the planet. As Phil Diamond, who was appointed as the first director-general of SKA in September, points out: “It will be the largest science facility on Earth.” […]

For the rest of this article, please contact Jon Cartwright for a pdf.

Published in Physics World, 15 Feb 2011

Light passing near to the spinning black holes thought to reside at the centre of many galaxies becomes twisted, possibly offering a new way to test Einstein’s general theory of relativity. That is the conclusion of an international team of physicists, who say the phenomenon could be seen with existing telescopes.

The general theory of relativity (GR), put forward by Einstein more than 90 years ago, predicts few phenomena that can be easily tested. One example is gravitational lensing – that the gravity of stars and black holes can warp space–time enough to bend the passage of light. Another is time dilation, which makes clocks sitting in regions of lower gravity – say, at high altitudes – tick faster. Scientists are still trying to directly detect yet another general-relativity phenomenon called gravitational waves. These are ripples in space–time thought to be generated when large masses accelerate. [...]

The rest of this article is available here.

Published in Physics World, 15 Jan 2010

For a large star, death is a bit of a squeeze. Once its nuclear fuel is spent, its core collapses, sparking a dramatic supernova explosion that blasts away the outer layers. The body left is a cold, tightly packed sphere called a neutron star, which, if massive enough, makes the ultimate collapse to a black hole.

The huge pressures inside neutron stars mean that all electrons and protons have joined so only neutrons remain. Near the centre, according to theory, these neutrons sometimes decompose into a sea of quarks, or so-called strange quark matter. A recent theory implies that this matter could form a stable ground state of nuclear matter – suggesting the existence of standalone “quark stars”. [...]

The rest o this article is available here.

Published in Physics World, 11 Jan 2010

Every physicist is taught that information cannot be transmitted faster than the speed of light. Yet laboratory experiments done over the last 30 years clearly show that some things appear to break this speed limit without upturning Einstein’s special theory of relativity. Now, astrophysicists in the US have seen such superluminal speeds in space – which could help us to gain a better understanding of the composition of the regions between stars.

Superluminal speeds are associated with a phenomenon known as anomalous dispersion, whereby the refractive index of a medium (such as an atomic gas) increases with the wavelength of transmitted light. When a light pulse – which is comprised of a group of light waves at a number of different wavelengths – passes through such a medium, its group velocity can be boosted to beyond the velocity of its constituent waves. However, the energy of the pulse still travels at the speed of light, which means that information is transferred in agreement with Einstein’s theory. [...]

The rest of the article is available here.