Polarization patterns of the twilight sky
| dc.contributor.author | Cronin, Thomas W. | |
| dc.contributor.author | Warrant, Eric J. | |
| dc.contributor.author | Greiner, Birgit | |
| dc.date.accessioned | 2019-04-18T17:51:50Z | |
| dc.date.available | 2019-04-18T17:51:50Z | |
| dc.date.issued | 2005-08-18 | |
| dc.description | Optics and Photonics 2005, San Diego, California, United States | en_US |
| dc.description.abstract | Although natural light sources produce depolarized light, patterns of partially linearly polarized light appear in the sky due to scattering from air molecules, dust, and aerosols. Many animals, including bees and ants, orient themselves to patterns of polarization that are present in daytime skies, when the intensity is high and skylight polarization is strong and predictable. The halicitid bee Megalopta genalis inhabits rainforests in Central America. Unlike typical bees, it forages before sunrise and after sunset, when light intensities under the forest canopy are very low, and must find its way to food sources and return to its nest in visually challenging circumstances. An important cue for the orientation could be patterns of polarization in the twilight sky. Therefore, we used a calibrated digital camera to image skylight polarization in an overhead patch of sky, 87.6° across, before dawn on Barro Colorado Island in Panama, where the bees are found. We simultaneously measured the spectral properties of polarized light in a cloudless patch of sky 15° across centered on the zenith. We also performed full-sky imaging of polarization before dawn and after dusk on Lizard Island in Australia, another tropical island. During twilight, celestial polarized light occurs in a wide band stretching perpendicular to the location of the hidden sun and reaching typical degrees of polarization near 80% at wavelengths >600 nm. This pattern appears about 45 minutes before local sunrise or disappears 45 minutes after local sunset (about 20 minutes after the onset of astronomical twilight at dawn, or before its end at dusk) and extends with little change through the entire twilight period. Such a strong and reliable orientation cue could be used for flight orientation by any animal with polarization sensitivity that navigates during twilight. | en_US |
| dc.description.sponsorship | This work is based on research supported by the National Science Foundation under Grant Number IBN-023582, by the Air Force Office of Scientific Research under Grant Number 02NL253, and by grants from the Swedish Research Council. Jamie Theobald assisted in the collection of polarization spectra. | en_US |
| dc.description.uri | https://www.spiedigitallibrary.org/conference-proceedings-of-spie/5888/1/Polarization-patterns-of-the-twilight-sky/10.1117/12.613053.full?SSO=1 | en_US |
| dc.format.extent | 9 pages | en_US |
| dc.genre | conference papers and proceedings | en_US |
| dc.identifier | doi:10.13016/m2usge-ehcy | |
| dc.identifier.citation | Thomas W. Cronin, Eric J. Warrant, and Birgit Greiner "Polarization patterns of the twilight sky", Proc. SPIE 5888, Polarization Science and Remote Sensing II, 58880R (18 August 2005); doi: 10.1117/12.613053; https://doi.org/10.1117/12.613053 | en_US |
| dc.identifier.uri | https://doi.org/10.1117/12.613053 | |
| dc.identifier.uri | http://hdl.handle.net/11603/13457 | |
| dc.language.iso | en_US | en_US |
| dc.publisher | SPIE | en_US |
| dc.relation.isAvailableAt | The University of Maryland, Baltimore County (UMBC) | |
| dc.relation.ispartof | UMBC Biological Sciences Department Collection | |
| dc.relation.ispartof | UMBC Faculty Collection | |
| dc.rights | This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author. | |
| dc.rights | © (2005) Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. | |
| dc.subject | polarized light | en_US |
| dc.subject | polarization sensitivity | en_US |
| dc.subject | polarization vision | en_US |
| dc.subject | celestial polarization | en_US |
| dc.subject | twilight | en_US |
| dc.subject | nocturnal bee | en_US |
| dc.title | Polarization patterns of the twilight sky | en_US |
| dc.type | Text | en_US |