Polarization transition between sunlit and moonlit skies with possible implications for animal orientation and Viking navigation: anomalous celestial twilight polarization at partial moon

Barta, András; Farkas, Anna; Száz, Dénes; Egri, Ádám; Barta, Pál; Kovács, József; Csák, B.; Jankovics, I.; Szabó, Gyula; Horváth, Gábor

doi:10.1364/ao.53.005193

Cited by 33 publications

(36 citation statements)

References 50 publications

(69 reference statements)

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“…Since the polarization characteristics of water surfaces are independent of light intensity, all the above-mentioned polarization patterns of open waters and riparian reflections are valid for both sunlit and moonlit conditions. The only difference is that direct moonlight and scattered moonlight originating from the sky are much dimmer than direct sunlight and scattered sunlight from the sky [1,6].…”

Section: Discussionmentioning

confidence: 99%

Mayflies are least attracted to vertical polarization: A polarotactic reaction helping to avoid unsuitable habitats

Farkas

Száz

Egri

et al. 2016

Physiology & Behavior

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Like other aquatic insects, mayflies are positively polarotactic and locate water surfaces by means of the horizontal polarization of water-reflected light. However, may vertically polarized light also have implications for the swarming behaviour of mayflies? To answer this question, we studied in four field experiments the behavioural responses of Ephoron virgo and Caenis robusta mayflies to lamps emitting horizontally and vertically polarized and unpolarized light. In both species, unpolarized light induces positive phototaxis, horizontally polarized light elicits positive photo-and polarotaxis, horizontally polarized light is much more attractive than unpolarized light, and vertically polarized light is the least attractive if the stimulus intensities and spectra are the same. Vertically polarized light was the most attractive for C. robusta if its intensity was about two and five times higher than that of the unpolarized and horizontally polarized stimuli, respectively. We suggest that the mayfly behaviour observed in our experiments may facilitate the stability of swarming above water surfaces. Beside the open water surface reflecting horizontally polarized light, the shadow and mirror image of riparian vegetation at the edge of the water surface reflect weakly and non-horizontally (mainly vertically) polarized light. Due to their positive polarotaxis, flying mayflies remain continuously above the water surface, because they keep away from the unpolarized or non-horizontally polarizing edge regions (water surface and coast line) of water bodies. We also discuss how our findings can explain the regulation of mayfly colonization.

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Section: Discussionmentioning

confidence: 99%

Mayflies are least attracted to vertical polarization: A polarotactic reaction helping to avoid unsuitable habitats

Farkas

Száz

Egri

et al. 2016

Physiology & Behavior

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“…[24]. Data on sky polarization have been collected with an automatic full-sky imaging polarimeter set-up in the Gothard Astronomical Observatory of the Eötvös University, Szombathely, Hungary (47°15′29.83′′ N, 16°36′15.67′′ E).…”

Section: Methodsmentioning

confidence: 99%

Celestial polarization patterns sufficient for Viking navigation with the naked eye: detectability of Haidinger's brushes on the sky versus meteorological conditions

et al. 2017

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If a human looks at the clear blue sky from which light with high enough degree of polarization d originates, an 8-shaped bowtie-like figure, the yellow Haidinger's brush can be perceived, the long axis of which points towards the sun. A band of high d arcs across the sky at 90° from the sun. A person can pick two points on that band, observe the yellow brushes and triangulate the position of the sun based on the orientation of the two observed brushes. This method has been suggested to have been used on the open sea by Viking navigators to determine the position of the invisible sun occluded by cloud or fog. Furthermore, Haidinger's brushes can also be used to locate the sun when it is below the horizon or occluded by objects on the horizon. To determine the position of the sun using the celestial polarization pattern, the d of the portion of the sky used must be greater than the viewer's degree of polarization threshold d* for perception of Haidinger's brushes. We studied under which sky conditions the prerequisite d > d* is satisfied. Using full-sky imaging polarimetry, we measured the d-pattern of skylight in the blue (450 nm) spectral range for 1296 different meteorological conditions with different solar elevation angles θ and per cent cloud cover ρ. From the measured d-patterns of a given sky we determined the proportion P of the sky for which d > d*. We obtained that P is the largest at low solar elevations θ ≈ 0° and under totally or nearly clear skies with cloud coverage ρ = 0%, when the sun's position is already easily determined. If the sun is below the horizon (−5° ≤ θ < 0°) during twilight, P = 76.17 ± 4.18% for dtruemin∗=23normal% under clear sky conditions. Consequently, the sky-polarimetric Viking navigation based on Haidinger's brushes is most useful after sunset and prior to sunrise, when the sun is not visible and large sky regions are bright, clear and polarized enough for perception of Haidinger's brushes.

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“…[373][374][375] A recently developed bioinspired camera system captures the light polarization pattern across the entire sky in a single image by using a wide-angle lens in combination with a triplet linear polarizer. [376] This device, ultimately a visual compass and optical global positioning system, allows its user to navigate or geolocate outdoors using purely optical information, and could be applied to pre-existing cameras in robotic systems as a simple and energy-efficient complement (or alternative) to standard guidance methods.…”

Section: Navigation With Polarizationmentioning

confidence: 99%

It's Not a Bug, It's a Feature: Functional Materials in Insects

2018

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Over the course of their wildly successful proliferation across the earth, the insects as a taxon have evolved enviable adaptations to their diverse habitats, which include adhesives, locomotor systems, hydrophobic surfaces, and sensors and actuators that transduce mechanical, acoustic, optical, thermal, and chemical signals. Insect‐inspired designs currently appear in a range of contexts, including antireflective coatings, optical displays, and computing algorithms. However, as over one million distinct and highly specialized species of insects have colonized nearly all habitable regions on the planet, they still provide a largely untapped pool of unique problem‐solving strategies. With the intent of providing materials scientists and engineers with a muse for the next generation of bioinspired materials, here, a selection of some of the most spectacular adaptations that insects have evolved is assembled and organized by function. The insects presented display dazzling optical properties as a result of natural photonic crystals, precise hierarchical patterns that span length scales from nanometers to millimeters, and formidable defense mechanisms that deploy an arsenal of chemical weaponry. Successful mimicry of these adaptations may facilitate technological solutions to as wide a range of problems as they solve in the insects that originated them.

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Polarization transition between sunlit and moonlit skies with possible implications for animal orientation and Viking navigation: anomalous celestial twilight polarization at partial moon

Cited by 33 publications

References 50 publications

Mayflies are least attracted to vertical polarization: A polarotactic reaction helping to avoid unsuitable habitats

Mayflies are least attracted to vertical polarization: A polarotactic reaction helping to avoid unsuitable habitats

Celestial polarization patterns sufficient for Viking navigation with the naked eye: detectability of Haidinger's brushes on the sky versus meteorological conditions

It's Not a Bug, It's a Feature: Functional Materials in Insects

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