Lifeboat Foundation

Tailoring and manipulating electromagnetic wave propagation has been of great interest within the scientific community for many decades. In this context, wave propagation has been engineered by properly introducing spatial inhomogeneities along the path where the wave is traveling. Antennas and communications systems in general have greatly benefited from this wave-matter control. For instance, if one needs to re-direct the radiated field (information) from an antenna (transmitter) to a desired direction and reach a receiving antenna placed at a different location, one can simply place the former in a translation stage and mechanically steer the propagation of the emitted electromagnetic wave.

Such beam steering techniques have greatly contributed to the spatial aiming of targets in applications such as radars and point-to-point communication systems. Beam steering can also be achieved using metamaterials and metasurfaces by means of spatially controlling the effective electromagnetic parameters of a designed meta-lens antenna system and/or using reconfigurable meta-surfaces. The next question to ask: Could we push the limits of current beam steering applications by controlling electromagnetic properties of media not only in space but also in time (i.e., 4D metamaterials x, y,z, t)? In order words, would it be possible to achieve temporal aiming of electromagnetic waves?

In a new paper published in Light Science & Applications, Victor Pacheco-Peña from the School of Mathematics, Statistics and Physics of Newcastle University in UK and Nader Engheta from and Department of Electrical and Systems Engineering of the University of Pennsylvania, USA have answered this question by proposing the idea of temporal metamaterials that change from an isotropic to an anisotropic permittivity tensor. In this concept, the authors consider a rapid change of the permittivity of the whole medium where the wave is traveling and demonstrated both numerically and analytically the effects of such a temporal boundary caused by the rapid temporal change of permittivity. In so doing, forward and backward waves are produced with wave vector k preserved through the whole process while frequency is changed, depending on the values of the permittivity tensor before and after the temporal change of permittivity.

Researchers from Kazan Federal University, Texas A&M University and Institute of Applied Physics (Russian Academy of Sciences) found ways to direct high frequency gamma radiation by means of acoustics.

Their paper describes an optical ‘switch’—a device able to let through or stop gamma quanta by switching the acoustic field. Basically, the mechanism makes iron ‘transparent’ for gamma rays when needed.

The Mossbauer Spectroscopy Lab of Kazan Federal University showed acoustically induced transparency of a resonant medium for gamma radiation in an experiment. The essence of this phenomenon lies in the transformation of the spectrum of the absorption line into a comb structure consisting of satellite lines spaced from the main line by the frequency of the acoustic field. For the experiment, gamma quanta with an energy of 14.4 keV were used, which are emitted during the decay of the excited state of the iron-57 nucleus.

But now, all the Arab world’s universities must be ready to run with the baton that Hope is handing to them. Currently, the overwhelming majority of the young people who watched the launch on their smartphones and decided on a career in space science will have to study abroad, because the Arab world largely lacks the capacity to educate them in astrophysics or space science.

The United Arab Emirates’ Mars probe is a stunning and historic effort, but it needs to be transformational, too.

Circa 2016

One way of realizing controlled nuclear fusion reactions for the production of energy involves confining a hot plasma in a magnetic field. Here, the physics of magnetic-confinement fusion is reviewed, focusing on the tokamak and stellarator concepts.

“D-Theory of Time, or Digital Presentism, gives us a coherent picture of temporal ontology: In the absence of observers, the arrow of time doesn’t exist — there’s no cosmic flow of time. With that in mind, your timeless cosmic self resides as a hyperdimensional being outside the ordinary space-time dimensionality of your experiential self… In fact, if we are to create high fidelity first-person simulated realities that also may be part of intersubjectivity-based, multiplayer virtualities, D-Theory of Time gives us a clear-cut guiding principle for doing just that.” –Alex M. Vikoulov, The Physics of Time: D-Theory of Time & Temporal Mechanics.

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Ripped from the pages of a sci-fi novel, physicists have crafted a wormhole that tunnels a magnetic field through space.

“This device can transmit the magnetic field from one point in space to another point, through a path that is magnetically invisible,” said study co-author Jordi Prat-Camps, a doctoral candidate in physics at the Autonomous University of Barcelona in Spain. “From a magnetic point of view, this device acts like a wormhole, as if the magnetic field was transferred through an extra special dimension.”

The idea of a wormhole comes from Albert Einstein’s theories. In 1935, Einstein and colleague Nathan Rosen realized that the general theory of relativity allowed for the existence of bridges that could link two different points in space-time. Theoretically these Einstein-Rosen bridges, or wormholes, could allow something to tunnel instantly between great distances (though the tunnels in this theory are extremely tiny, so ordinarily wouldn’t fit a space traveler). So far, no one has found evidence that space-time wormholes actually exist. [Science Fact or Fiction? The Plausibility of 10 Sci-Fi Concepts].

One of the most important controversies in physics remains unresolved after a major new study. But at least we have a new precise number for the universe’s age.

In a breakthrough for physics and engineering, researchers from the Photonics Initiative at the Advanced Science Research Center at The Graduate Center, CUNY (CUNY ASRC) and from Georgia Tech have presented the first demonstration of topological order based on time modulations. This advancement allows the researchers to propagate sound waves along the boundaries of topological metamaterials without the risk of waves traveling backwards or being thwarted by material defects.

The new findings, which appear in the journal Science Advances, will pave the way for cheaper, lighter devices that use less battery power, and which can function in harsh or hazardous environments. Andrea Alù, founding director of the CUNY ASRC Photonics Initiative and Professor of Physics at The Graduate Center, CUNY, and postdoctoral research associate Xiang Ni were authors on the paper, together with Amir Ardabi and Michael Leamy from Georgia Tech.

The field of topology examines properties of an object that are not affected by continuous deformations. In a topological insulator, electrical currents can flow along the object’s boundaries, and this flow is resistant to being interrupted by the object’s imperfections. Recent progress in the field of metamaterials has extended these features to control the propagation of sound and light following similar principles.

A new paper revives a hero from physics’s past.

Science & technology Jul 18th 2020 edition.