Physics News of the Week: Quantum Grandfather Paradox and Dark Matter

| September 7, 2014 | 1 Comment

Another great week has gone by and it’s time to take a look at the top events from the world of physics. As always, here are the top 3 news with corresponding links. If you would like to receive these news straight to your email box, register for our email newsletter here.

1. Time Travel Simulation Resolves the ”Grandfather Paradox” (Sep 2)

An age old question of what would happen if you went back in time and killed your grandfather might just have been answered by a quantum mechanics simulation. The source of time travel speculations lies in the fact that our best physical theories seem to contain no prohibitions on traveling backward through time. In particular, the general theory of relativity allows the so-called closed time-like curves (CTC’s), which allow backwards time travel, at least in principle.

Recently, in an experimental simulation of David Deutsch’s models by Tim Ralph and colleagues, it was confirmed that backwards time travel is not allowed. According to the work done by Deutsch, paradoxes created by CTCs should be avoided at the quantum scale. In their new simulation Ralph, Ringbauer and their colleagues studied Deutsch’s model using interactions between pairs of polarized photons within a quantum system that they argue is mathematically equivalent to a single photon traversing a CTC. To get all the details, read the full article using the link above.

2. A New Model For Dark Matter (Sep 2)

So recently a new model aiming to explain the nature of dark matter has been proposed by Prof  Mikhail Medvedev from the University of Kansas.  Medvedev proposed a novel model of dark matter, dubbed “flavor-mixed multicomponent dark matter.” “In everyday life we’ve become used to the fact that each and every particle or an atom has a certain mass,” Medvedev said. “A flavor-mixed particle is weird—it has several masses simultaneously—and this leads to fascinating and unusual effects.”

Medvedev’s ideas were incorporated into a numerical cosmological code, which successfully solved a number of long-standing puzzles often encountered in similar models of dark matter. “Our results demonstrated that the flavor-mixed, two-component dark matter model resolved all the most pressing Lambda-CDM problems simultaneously,” said the KU researcher. To find out more use the link above.

Rosetta spacecraft

3. “Rosetta” Set for Capture Manoeuvers (Sep 2)

Rosetta is a robotic space probe built and launched by the European Space Agency to perform a detailed study of comet 67P/Churyumov–Gerasimenko. On 6 August 2014 it approached the comet to a distance of about 100 km and reduced its relative velocity to 1 m/s, thus becoming the first spacecraft to rendezvous with a comet. The ultimate aim of the probe is to dispatch a robotic lander for the first controlled touchdown on a comet nucleus.

Currently the Rosetta probe is about to begin the manoeuvres that will place it properly into orbit around Comet 67P/Churyumov-Gerasimenko.  From Wednesday, Rosetta will gradually drop this distance so that come next week it will be at an altitude of just 29km.

“The first orbit – we will actually fly only half of it for seven days, and then we’ll change the orbital plane and fly for another seven days. And then, if the comet environment allows us to continue, we’ll go further down, first to 19km and then to 10km from the centre of the comet, ” said the European Space Agency  flight director Andrea Accomazzo. The landing itself – which will be performed by Rosetta’s contact robot Philae – is scheduled to take place on 11 November.

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