Programmable Materials “Could Change the World of Mechanics Forever”
Researchers from Empa and ETH Zurich have developed a prototype of a selective vibration-damping material that they claim “could change the world of mechanics forever” as a step toward “programmable materials.”
Described in the journal Advanced Materials, this “material of the future” can damp mechanical vibrations completely or selectively suppress specific vibration frequencies or ranges of frequencies.
The one-dimensional working model consists of a simple aluminum sheet-metal strip, measuring one meter by one centimeter and one millimeter thick and designed to vibrate at different frequencies. To control the wave propagation through the plate, ten small aluminum cylinders (7 mm thick, 1 cm high) are attached to the metal. Between the sheet and the cylinders sit piezoelectric discs, which can be stimulated electronically to instantly change their thickness. That allows for controlling exactly how waves are allowed to propagate in the sheet-metal strip.
The aluminum strip thus turns into an “adaptive phononic crystal” — a material with controllable vibration properties.
The Harvard-Smithsonian Center for Astrophysics has news so big it announced that it would announce something. The press conference will stream live tomorrow at noon, but cosmologists everywhere are gossiping about what that news could be. The leading theory: Scientists have detected gravitational waves, in what would be a landmark discovery for the field of physics.
Gravitational waves are the last chunk of Einstein’s General Theory of Relativity that was predicted but not yet observed. If gravitational waves have been observed, it most likely was done by the Background Imaging of Cosmic Extragalactic Polarization (Bicep) telescope at the south pole. It stared at the cosmic microwave background radiation from 2003 to 2008, but it takes a long time to process and analyze the data when looking for a faint signal in a lot of noise.
2007 photograph of telescopes at the Dark Center at the Amundsen-Scott South Pole Station. From top to bottom, the partly-buried AST/RO, QUaD, Viper, and finally BICEP and SPT at the bottom. Image credit: Robert Schwarz
The Bicep mission page describes anticipated gravitational waves as faint, polarized, and distorted by gravitational lensing of objects between us and the cosmic microwave background radiation. They released a video of their observations in 2008. The colour scale adjusts throughout the movie to highlight temperature fluctuations of both the cosmic microwave background radiation, and the galactic plane:
Why look at the cosmic microwave background radiation for signs of gravitational waves? Because an infinitesimal moment after the universe started — 10-34 seconds after the big bang — we think it went through an inflationary period. If it did, that inflation could have amplified gravitational waves to such an extent that we can actually detect them. This would not only fill in that last missing chunk of things predicted by General Relativity that we haven’t seen yet, but also offer a glimpse into the primeval universe. They won’t be insta-proof that inflationary theory is correct, but they would rule out some cyclic theories for the origin of the universe.
Some pre-announcement articles are already mixing up very common gravity waves with gravitational waves. To differentiate, I’ll pass things off to an exasperated Dr. Katherine Mack:
As for the press conference, I’m already bracing for disappointment. “Breaking news! We’ll have breaking news for you on Monday!” announcements produce so much hype that the actual discovery probably won’t live up to expectations. I’m not the only one feeling that way — the Guardian ran an entire piece interviewing cautiously excited cosmologists warning that the observations would need to be highly robust if they’re going to be momentous.