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BLOOMINGTON, Ill.— An international team of physicists including Illinois Wesleyan University Professor of Physics Gabe Spalding has shown waves of light can seem to travel back in time.

It may seem like science fiction, but the experiment did not violate the laws of physics. Spalding, his physics student Joseph Richards ’16 and a team of scientists tackled a century-old intuition from Lord Rayleigh regarding the speed of sound. Rayleigh theorized that music being played on an object traveling faster than the speed of sound, a supersonic jet for example, would result in a listener hearing the music playing in reverse. The Spalding team simulated what an observer standing still would see when looking at a superluminal (faster than the speed of light) occurrence. The results of the scientists’ experiment, conducted last summer at Heriot-Watt University in Edinburgh, Scotland, have been published in Science Advances.

“The existence of an absolute limit, the speed of light, is the natural source of the question: what would happen if we cross this limit?” lead author Mattero Clerici told a writer for a post on IFLScience. “Light sources, however, may move faster than the speed of light when their speed is not associated with the physical motion of matter. Following this line of thought, we devised a way to experimentally investigate the [effects] of superluminal motion.”

Last September, researchers detected an exceptionally weak signal that lasted for about a tenth of a second: the gentle chirp of a gravitational wave. This feat, which confirmed a prediction made by Albert Einstein 100 years ago, is worthy of the Nobel prize.

Experiments that can fit on a tabletop are probing the nature of dark matter and dark energy and searching for evidence of extra dimensions.

Despite the fact that they’re still unsure of how it works exactly, NASA scientists have confirmed once again that the seemingly impossible EmDrive is legit.

Gotta luv this.

An international team of researchers including the Lomonosov Moscow State University physicists has developed a completely new type of drug carrier for targeted delivery to the sick organ — the gel nano-capsules with a double shell. The results of the study were published in Scientific Reports.

(Phys.org)—The question of why space is three-dimensional (3D) and not some other number of dimensions has puzzled philosophers and scientists since ancient Greece. Space-time overall is four-dimensional, or (3 + 1)-dimensional, where time is the fourth dimension. It’s well-known that the time dimension is related to the second law of thermodynamics: time has one direction (forward) because entropy (a measure of disorder) never decreases in a closed system such as the universe.

In a new paper published in EPL, researchers have proposed that the second law of thermodynamics may also explain why space is 3D.

“A number of researchers in the fields of science and philosophy have addressed the problem of the (3+1)-dimensional nature of space-time by justifying the suitable choice of its dimensionality in order to maintain life, stability and complexity,” coauthor Julian Gonzalez-Ayala, at the National Polytechnic Institute in Mexico and the University of Salamanca in Spain, told Phys.org.

WORMHOLES could be responsible for gravitational waves, a new study has suggested, adding more mystery to the “scientific breakthrough of the year”.

The result is a compact accelerator that is not much larger than the laser used to create the plasma. That means that a laser plasma accelerator can be housed in a small building, rather than stretching over hundreds of metres or even several kilometres.

High-quality beam

While laser plasma accelerators exist at several laboratories around the world, EuPRAXIA steering-committee member Carsten Welsch says that “no infrastructure exists where the quality of the accelerated beam satisfies the requirements of industry”. Welsch, who is at the UK’s Cockcroft Institute of Accelerator Science and Technology, adds that “creating such a facility would be a major breakthrough and would attract users from many different sectors”.

Continue reading “Consortium sets out to build European laser plasma accelerator” »

Ever since Kepler’s observation in the 17th century that sunlight is one of the reasons that the tails of comets to always face away from the sun, it has been understood that light exerts pressure in the direction it propagates. Radiation pressure is produced by the momentum carried by light, and it plays a crucial role in a variety of systems, from atomic to astronomical scales.

In a recent theoretical paper, a group from the RIKEN Center for Emergent Matter Science in Japan showed that momentum density in non-uniform optical fields has an unusual component, which is orthogonal to the propagation direction of light and is proportional to the optical spin, which means the degree of circular polarization. They predicted that this spin momentum would produce a transverse spin-dependent optical force, a few orders of magnitude weaker than the usual radiation pressure.

Now, based on the theoretical work, a group from RIKEN, the University of Bristol, and other institutions have used an extremely precise technique to experimentally verify that light does in fact exert the extraordinary perpendicular force, which is determined by the polarization of the light. The research has been published in Nature Physics.