Spectroscopy Technique Reveals Nanoscale Acoustic Waves

Imaging using extreme ultraviolet scattering shows that optical pulses can generate surface excitations with spectra that were previously difficult to achieve. [...] Surface acoustic waves (SAWs) propagate along a solid material’s surface like ripples on a pond. SAWs with wavelengths of hundreds of kilometers are generated by earthquakes, whereas SAWs with wavelengths at the micrometer scale can be excited by lasers. Flavio Capotondi at the Free Electron laser Radiation for Multidisciplinary Investigations (FERMI) facility at Elettra Sincrotrone Trieste in Italy and his colleagues have now demonstrated a simple laser-based technique for exciting and detecting SAWs with nanometer wavelengths [1]. They say that the work will allow the dynamics of materials’ crystal lattices to be probed over a wavelength range that has been inaccessible using other approaches.

As I promised yesterday, today I will let you know the rest of the story of this fascinating dessert, Jell-O. Yesterday I told you about the new "Jello-O Meter" that measures sound & its intensity at concerts & stadiums. It all has to do with plain physics, actually. It has a sound-pressure sensor that uses a wobbly plate instead of a microphone diaphragm. When any crowd gathers, there is usually a lot of cheering, yelling, shouting & noise. The Jell-O contains a metal plate under which lies a metal plate that has piezoelectric motion sensor films & a mechanical actuator that jiggles the Jell-O. This is the physics of vibration analysis. The rowdier the crowd, the more it jiggles. It's already been used at a professional hockey game in NY that registered a 5.8 on the Jell-O Meter, which is normal cheering.

The energy is measured on an algorithmic scale, with 1 jiggle roughly equivalent to a microwave, while 10 is supposedly the same as a small earthquake, the equivalent of Taylor Swift's Seattle Eras Tour, where seismometers recorded ground motion equivalent to a 2.3 earthquake, dubbed a "SwiftQuake," caused by 70,000 fans jumping in rhythm. In Dublin (2024), seismic waves from "Shake it Off" were detected up to 60 miles away. Undoubtedly, those events would register a 10 on the Jell-O Meter. These registered 110-120 dB; however, they were nowhere near the loudest roar of the Arrowhead Stadium fans, which occurred in 2014 when the Kansas City Chiefs' roar registered 142.2, the loudest roar ever of any event that earned a title in the Guinness World Records. That's equivalent to the sound of a jet taking off; nevertheless, there was no seismic activity that shook the earth as in Swift's concerts because the Chiefs fans produced air pressure through sound—they weren't hitting the ground with their feet.

Jell-O was created by cough syrup & laxative maker Pearle Bixby Wait in 1897, but he knew he could make more money with similar ingredients, making a gelatin dessert, as they were expensive & were a luxury food for the rich in most of Western society. Jell-O only became "everyday" once industrial chemistry caught up. Pearl Wait's invention made gelatin cheap, pre-flavored, pre-sweetened & dissolved instantly, fast becoming a mass-market food, a kid food, a church-basement potluck food, a hospital food & a favorite 1950s housewife staple. It appears that noise levels are not the only thing Jell-O can measure. On March 17, 1993, technicians at St. Jerome Hospital in Batavia, NY, hooked an EEG machine to a bowl of lime Jell-O. And you know what? They found that the Jell-O produced brainwave-like electrical patterns identical to those produced by adult humans.

Does that mean that humans have the intelligence of a bowl of Jell-O? For most of us, the answer is no. EEG machines are extremely sensitive to electrical noise, vibration & electrode drift. A bowl of gelatin is a homogenous electrolyte gel, so electrodes can pick up ambient electrical interference that looks like human EEG rhythms. Jell-O has even been made in space. Shannon Lucid, a university student who eventually became an astronaut for NASA, flew to the Russian space station Mir aboard Space Shuttle Atlantis in 1996 and made weekly Jell-O in space. To make it in space is not easy since you can't safely boil water. Instead, they have a rehydration station where water is heated in a sealed pouch. That is sufficient to set gelatin, which sets between 59 and 77°F (15 and 23°C).

In the 1990s, Jell-O was used to predict the stock market after Kraft noticed that lime Jell-O sales rose during recessions. In the 1920s, Jell-O was used to smuggle alcohol into U.S. Navy parties, as alcohol was not permitted. It worked because gelatin traps ethanol in a semi-solid matrix, making it harder to detect. Teachers (including myself) use it to demonstrate wave propagation, resonance, vibration modes & seismic wave analogies. Clear Jell-O was used in photography in 1871 when photography companies began mass-producing gelatin plates with silver halide. After light enters a camera, it hits the gelatin layer & triggers chemical changes in the silver crystals, which turn into black metallic silver, & the ones that weren't hit stay unchanged. The gelatin acts as a fixer, keeping everything from washing away. Without gelatin, the picture would literally slide away. Jell-O is popular in college campuses, where they use it to wrestle in.

"Marvelous sound forms." Marvelous wonders of the whole world. 1886.