News and Events

Follow a sunset on a clear day against a distant horizon and you might glimpse green just as the Sun disappears from view. The green flash is caused by refraction of light rays traveling to the eye over a long path through the atmosphere. Shorter wavelengths refract more strongly than longer redder wavelengths and the separation of colors lends a green hue to the last visible vestige of the solar disk. It's harder to see a green flash from the Moon, not to mention the diminutive disks of Venus and Mercury. But a telescope or telephoto lens and camera can help catch this tantalizing result of atmospheric refraction when the celestial bodies are near the horizon. From Sicily, the top panels were recorded on March 18, 2019 for the Sun and May 8, 2020 for the Moon. Also from the Mediterranean island, the bottom panels were shot during the twilight apparition of Venus and Mercury near the western horizon on May 24.
Check current conditions and historical weather data at the ESC.
Students of the Physics 106 afternoon section participated in an extra credit opportunity that took hands-on learning to a new level. Inspired by a classic MIT challenge, Professor Della Corte gave each student a small kit containing two thumb tacks, two paper clips, six feet of copper wire, two neodymium magnets, and a block of wood. He then sent his students on their way with limited instructions: Design your own motors, only using materials from the kits. Any drop of glue or strip of tape would disqualify them.
Liz Finlayson, who is graduating from the Physics Teaching program, was recently highlighted in the APS Spring 2020 newsletter
New telescope installed in the campus dome on February 22, 2020
A new study from researchers at Brigham Young University and Pennsylvania State University provides the most accurate estimate of the number of Earth-like planets in the universe. The team looked at the frequency of planets that are similar to Earth in size and in distance from their host star, stars similar to our Sun. Knowing the rate that these potentially habitable planets occur will be important for designing future astronomical missions to characterize nearby rocky planets around Sun-like stars that could support life.

Selected Publications

BYU Authors: Kent L. Gee and S. Hales Swift, published in Proc. Meet. Acoust.
This paper describes a study conducted at U.S. Marine Corps Base Quantico to determine firing range impulse noise levels and assess noise exposures. Measurements were performed with M16A4 rifles at an outdoor firing range, using a 113-channel array of 6.35 and 3.18 mm microphones that spanned potential locations for both shooters and instructors. Data were acquired using 24-bit cards at a sampling rate of 204.8 kHz. Single weapon measurements were made with and without an occupied range, with a shooter and with a remotely triggered gun stand. In addition, measurements were made with multiple shooters to simulate exposures for a realistic range environment. Results are shown for the various range configurations as a function of angle and distance. Analyses include waveforms, spectra, and peak levels, as well as the 10 ms equivalent level. All measurements met guidelines of the applicable military standard MIL-STD-1474E and the data are shown to be of high fidelity and useful for future in-depth analyses and noise dosage model development.
BYU Authors: Richard D. Barney and Jean-François S. Van Huele, published in J. Utah Acad. Sci.

A core tenet of quantum theory is the fact that objects can behave as particles, waves, or a combination of both. This principle is known as particle–wave duality. Quantum objects will exhibit different degrees of particle or wave behavior depending on how their observables are en-tangled. An illustrative example of entanglement is the Stern-Gerlach effect, which entangles the spin of objects with their trajectory. A single Stern-Gerlach magnetic field will cause the objects to behave as particles, but a second field with its inhomogeneity oriented in a different direction to the first will cause the objects to recover some wave behavior. This is evidenced in a pattern of fringes in each object’s spatial proba-bility density. Maximum entanglement leads to pure particle behavior while the absence of entanglement leads to pure wave behavior. The amount of entanglement can be controlled by choosing the angle be-tween the inhomogeneities of the two fields that act on the object. Having the two field inhomogeneities oriented perpendicularly to each other leads to maximum recovered wave behavior for spin-1/2 objects. The amount of recovered wave behavior decreases as the field inhomogeneity directions move towards being parallel.

BYU Authors: David F. Van Komen, Blaine M. Harker, Tracianne B. Neilsen, Kent L. Gee, S. Hales Swift, and Alan T. Wall, published in J. Acoust. Soc. Am.

Noise from a tactical aircraft can impact operations due to concerns regarding military personnel noise exposure and community annoyance and disturbance. The efficacy of mission planning can increase when the distinct, complex acoustic source mechanisms creating the noise are better understood. For each type of noise, equivalent acoustic source distributions are obtained from a tied-down F-35B operating at various engine conditions using the hybrid method for acoustic source imaging of Padois, Gauthier, and Berry [J. Sound Vib. 333, 6858–6868 (2014)]. The source distributions for the distinct noise types are obtained using different sections of a 71 element, ground-based linear array. Using a subarray close to the nozzle exit plane, source distributions are obtained for fine-scale turbulent mixing noise and broadband shock-associated noise, although grating lobes complicate interpretations at higher frequencies. Results for a subarray spanning the maximum sound region show that the multiple frequency peaks in tactical aircraft noise appear to originate from overlapping source regions. The observation of overlapping spatial extent of competing noise sources is supported by the coherence properties of the source distributions for the different subarrays.