Tuesday, 31 December 2013

There, but invisible

Swell by Anthony McCall. Commissioned by AV Festival 2006.

In physics, the darkness is the most illuminating place to look, if you want to understand the Universe right now. This year, Planck told us that 26.8% of all matter is dark. Thanks to the earlier work of Brian Schmidt, Saul Perlmutter and Eric Riess, cosmologists also have to deal with the fact that the Universe is expanding at an ever increasing rate, and that the energy responsible for that - dark energy - accounts for 68.3% of all energy.

So we now know that nearly 96% of the Universe is dark. It is there; but invisible.

But what this means is that we live in some of the most exciting times imaginable.
Because we live in a Universe that is to a large extent unknown to science, and therefore the systems that govern all but 4% of the Universe are yet to be discovered.

"And, everything is possible again."

I'll be taking that thought into 2014.

Honor Harger
31 December 2013

Sunday, 15 December 2013

The Beam of Darkness

This week, engineers from Singapore released details of a fascinating prototype which takes a radically different approach to the creation of an invisibility cloak.

Whilst still popularly considered the realm of science fiction, many working prototypes for 'invisibility cloaks' have been demonstrated in the past few years, most using metamaterials, and some using tiny antennae.

Using a principle, referred to as "anti-resolution", the Singaporean researchers have taken a completely different approach, and have built a "darkness beam" that bathes objects in the absence of light.

Using special lenses, optical engineer Chao Wan and his colleagues, have effectively created a region of space where the intensity of light is close to zero. As Sebastian Anthony points out, "if there’s no light, nothing can be resolved.  They have created an empty light capsule of invisibility."

The arXiv blog explains further:
"Optical engineers generally build imaging systems with the best possible resolving power. The basic idea is that an imaging system focuses light into a pattern known as a point spreading function. This consists of a central region of high intensity surrounded by a concentric lobe of lower intensity light. The trick to improving resolution is narrowing and intensifying this central region while suppressing the outer lobe. Now [the Singaporean] optical engineers have turned this approach on its head by suppressing the central region so that the field intensity here is zero while intensifying the lobe. The result is a three-dimensional beam of darkness that hides any object inside it."

The researchers describe their technique in detail in a paper on arXiv:

"We theoretically and experimentally demonstrate the focusing of macroscopic 3D darkness surrounded by all light in free space. The object staying in the darkness is similar to staying in an empty light capsule because light just bypasses it by resorting to destructive interference."

In their full paper, the team conclude that the applications for such technology are manifold. And somewhat chilling:

"This new  scheme of maneuvering light creates a plethora of possibilities for optical imaging systems, superb surveillance by seeing things behind for the military use, or cloaking the object surrounded by high field intensity."