Terahertz spectroscopy uses beams of electromagnetic radiation that lie between microwaves (used in kitchen ovens) and infrared rays (used in TV remotes) on the spectrum. These waves are known for their ability to examine materials without damaging them, unlike X-rays and ultraviolet light, and are commonly used in other areas like biomedical imaging and pharmaceuticals.

While using this technology to examine a painting, Bianca Jackson, a postdoctoral research fellow at the University of Rochester, found evidence of another painting underneath.

“We were amazed, and we were delighted,” she said during a presentation to the American Chemical Society. “We could not believe our eyes as the image materialized on the screen. Underneath the top painting of the folds of a man’s tunic, we saw an eye, a nose and then a mouth appear. We were seeing what likely was part of an ancient Roman fresco, thousands of years old.”

The ‘he” referred to is Giampetro Campana, a 19th century Italian art collector who assembled an impressive collection of Greek, Roman, and early Italian artwork. Back then, it was common practice for artists to paint over existing works of art, either because they could not afford new canvases or because patrons commissioned new artwork to cover up older or unsuccessful pieces. Researchers had reason to believe that Campana commissioned Trois hommes armes de lances to go over another image.

Initially, the team tried using x-ray radiography  and x-ray fluorescence to find out what secrets lurked beneath. However, it wasn’t until they tried terahertz spectroscopy that the original artwork peeked through.

“No previous imaging technique, including almost half a dozen commonly used to detect hidden images below paintings, forged signatures of artists and other information not visible on the surface has revealed a lost image in this fresco,” Jackson said. “This opens to door to wider use of the technology in the world of art, and we also used the method to study a Russian religious icon and the walls of a mud hut in one of humanity’s first settlements in what was ancient Turkey.”

Photo Credit: J. Bianca Jackson, Ph.D. and Dominique Martos-Levif

Or, more precisely, a way of geoforming the ocean floor to almost eliminate surface waves.

Sessions at the 65th annual meeting of the American Physical Society’s division of fluid dynamics  include presumably fascinating talks on “Bubbles,” “Vortex,” “General Fluids,” and “Drops.” Not to mention “Bubbles II.”

One paper being presented, however, has a less pedestrian title: “A Cloak of Invisibility Against Ocean Waves.” Reza Alam, a professor of mechanical engineering at the University of California, Berkeley, will be speaking about a way he has discovered of neutralizing ocean waves in near-shore or off-shore areas.

How?

The magic — or the science — lies in the fact that, as Alam explained to Phys.org, the ocean is stratified into layers: warmer, less dense water at the top, and colder, heavier water at the bottom. Each layer has waves: surface waves at the top, and internal waves in the lower levels. And, crucially, all waves — even surface waves — interact with the ocean floor.

By “properly architecting the bottom corrugations” of the ocean floor, Alam has discovered that “floating objects in stratified fluids can be cloaked against broadband incident waves.” Translation: by making the right hills and valleys in the ocean floor, waves can be transformed from surface waves to internal waves.

Meaning that, from the perspective of an observer floating on the surface of the ocean, the waves have simply disappeared. Of course, they actually have not — they have simply become internal waves deeper within the ocean layers.

And a reverse effect is possible as well. As Alam told Phys.org, “In reverse, it can cause the … reappearance of surface waves in areas where sandbars or any other appreciable bottom variations exist.”

Which means that the same technology that might help shelter marinas or offshore installations might also be used to create a surfer’s paradise.

photo credit: nathangibbs via photopin cc, play4smee via photopin cc