The prevailing notion that space’s vacuum prohibits the transmission of sound has been shattered by a groundbreaking experiment conducted by researchers at the University of Jyväskylä in Finland. This audacious feat involved successfully “tunneling” sound through a vacuum using an electromagnetic effect, a phenomenon that challenges the conventional belief of space as a soundless void. However, it’s important to emphasize that this extraordinary sound transmission is only feasible over incredibly minute distances.
The concept of sound propagation in space is indeed intriguing and eerie, best exemplified by the iconic tagline from the movie Alien: “In space, no one can hear you scream.” The fundamental reason behind this notion is that traditional sound waves, referred to as “acoustic phonons,” necessitate a medium like air or water to travel. The vacuum of space lacks the necessary particles for sound to propagate, thus rendering it silent.
Yet, the recent experiment conducted by Finnish scientists introduces a profound twist to this understanding. By creating a vacuum gap between two piezoelectric zinc oxide crystals, the researchers successfully facilitated the “tunneling” of sound from one crystal to another.
In a study published in Communications Physics, the scientists elaborated on their findings: “[Sound waves] do not exist in vacuum, leading to the initial conclusion that it is impossible for the vacuum to transmit the energy of an acoustic wave between two separated media. However, at the atomic scale, the vibrations of the nuclei can propagate via their electrical interactions through vacuum. Thus, a question can be raised, whether acoustic phonons can also be transmitted across larger than atomic scale vacuum gaps through some electromagnetic mechanism.”
Piezoelectric crystals possess the unique property of generating electricity when subjected to heat or mechanical stress, including sound. The presence of electricity within a vacuum enabled the transmission of sound waves between the crystals through an electric field—a phenomenon aptly likened to “tunneling.”
However, certain constraints accompany this extraordinary revelation. The distance between the two crystals must remain smaller than the wavelength of the sound wave itself. As the frequency of sound waves escalates, the gap between the crystals must proportionally decrease.
While the process of sound “tunneling” isn’t devoid of imperfections, leading to intermittent distortions and reflections, its implications are far-reaching. It paves the way for potential applications in diverse fields, ranging from smartphone technology to heat control. Ilari Maasilta, a co-author of the study, expounded on this aspect, stating, “In most cases, the effect is small, but we also found situations where the full energy of the wave jumps across the vacuum with 100% efficiency, without any reflections. As such, the phenomenon could find applications in microelectromechanical components (smartphone technology) and in the control of heat.”
While the iconic notion of sound reverberating through the vacuum of space endures in science fiction, this groundbreaking experiment reshapes our understanding of sound propagation and unlocks prospects for innovative technological breakthroughs.
