Answer · confidence: partial
Can an ordinary observer tell where the sun is from the sky's polarization pattern, even on a smoky afternoon?
The records show that the sun-dependent polarization pattern of skylight is not visible to humans 15, though people can perceive polarization through Haidinger's brush, which is seen with practice in blue sky 15 and appears when facing about 90 degrees from the sun 9. The 2011 Iceland spar method for finding the sun was proposed 4, but attempts to replicate it in 2014 in Scotland and off the coast of Turkey failed 10, and the replicator suspected that using the stones effectively requires practice 11. The records do not address smoky afternoons, so they do not say whether smoke changes the result, and they only note that sky polarization is used to retrieve aerosol properties 8. The newest relevant fact dates to 2019, about seven years before October 2026 26.
Checked 2026-10-19. Only documented and supported facts are used.
Dig deeper on this questionSources
[1] supported
Many people are able to perceive the polarization of light.
"Many people are able to perceive polarization of light."Haidinger's brush
[2] documented
Sunlight becomes partially linearly polarized when it is scattered by atmospheric gas molecules, which is the physical basis for sky polarization patterns.
"Sunlight becomes partially linearly polarized when scattered from atmospheric gas molecules and can be quantified using the linear Stokes parameters S0 , S1 , S2 and the derived degree of linear polarization and angle of polarization (AoP)."Visualization of all-sky polarization images referenced in the instrument, scattering, and solar principal planes (2019)
[3] documented
On a clear sky, Rayleigh scattering produces a distinct all-sky polarization pattern, with maximum linear polarization in a band about 90 degrees from the sun.
"For a clear-sky environment, Rayleigh scattering dominates, resulting from scattering by atmospheric gas molecules that are much smaller than the optical wavelength, and a distinct all-sky polarization pattern exists. A band of maximum degree of linear polarization can be observed 90? from the sun with polarization vectors orientated perpendicular to the scattering plane (i.e. the plane containing"A Study of Atmospheric Polarization in Unique Scattering Conditions at Twilight, during a Solar Eclipse, and for Cloud Phase Retrievals Using All-Sky Polarization Imaging (2018)
[4] supported
A 2011 study proposed that a person can find the sun's direction from sky polarization by looking at a patch of clear sky through a correctly oriented Iceland spar crystal, then removing the crystal and seeing a faint pattern with the naked eye.
"In the first process one looks at a patch of clear sky through a properly oriented crystal, then the crystal is quickly removed so that one can see with a naked eye a faint blue-yellow entopic pattern that shows the polarization direction."Sunstone (medieval)
[5] supported
With practice, a person can see Haidinger's brush in the naturally polarized light of a blue sky.
"With practice, it is possible to see it in the naturally polarized light of a blue sky."Haidinger's brush
[6] supported
The solar principal plane is one of the standard reference planes used to analyze sky polarization data, and it provides its own insights into that data.
"Commonly used reference planes for polarimetric applications include the instrument, scattering, and solar principal planes, each of which provides unique insights when analyzing sky polarization data."Visualization of all-sky polarization images referenced in the instrument, scattering, and solar principal planes (2019)
[7] supported
The sky is most strongly polarized in the areas about 90 degrees away from the sun, which is why the effect is best seen when facing that direction.
"The areas of the sky with the strongest polarization are those 90 degrees away from the sun."Haidinger's brush
[8] supported
Sky polarization patterns are exploited in navigation to find compass headings, as well as for detecting objects and retrieving aerosol and cloud properties.
"Military, environmental, and navigational applications exploit the sky polarization pattern to detect objects, retrieve aerosol and cloud properties, and to find compass headings based on the sky polarization pattern."A Study of Atmospheric Polarization in Unique Scattering Conditions at Twilight, during a Solar Eclipse, and for Cloud Phase Retrievals Using All-Sky Polarization Imaging (2018)
[9] supported
Haidinger's brush appears as a yellowish bar or bow-tie shape in the center of the visual field against the blue sky when the observer faces about 90° from the sun.
"visible in the center of the visual field against the blue sky viewed while facing approximately 90° from the sun"Haidinger's brush
[10] supported
Attempts in 2014 to replicate the Iceland spar sun-finding method in Scotland and off the coast of Turkey failed.
"Attempts to replicate this work in both Scotland and off the coast of Turkey by science journalist Matt Kaplan and mineralogists at the British Geological Survey in 2014 failed."Sunstone (medieval)
[11] supported
The author of the replication report suspected that using the stones effectively requires practice, since the replicators could not tell why the Iceland spar samples failed to reveal the sun's direction.
"with the author hypothesizing that the stones require some experience to be handled effectively"Sunstone (medieval)
[12] documented
The study found that the degree of polarization is a key parameter indicating how accurate angle-of-polarization measurements of skylight are.
"The results of experiments reveal that the DOP is a key parameter to indicate the accuracy of AOP measurements, and all the output solar meridian orientations extracted by our method in both clear and cloudy skies can achieve a high accuracy for vehicle orientation."An Evaluation of Skylight Polarization Patterns for Navigation (2015)
[13] supported
Pernter published a 1901 study on the polarization of light in turbid media and of skylight, aimed at explaining the blue color of the sky.
"1901: Untersuchungen über die Polarisation des Lichtes in trüben Medien und des Himmelslichtes mit Rücksicht auf die Erklärung der blauen Farbe des Himmels"Josef Maria Pernter
[14] supported
The skylight polarization pattern arises from scattering of sunlight in the atmosphere and is modeled from Rayleigh scattering theory combined with solar position.
"Model and prediction of skylight polarization distribution pattern that arises due to scattering of sunlight in the atmosphere plays a vital role in bionic navigation sensor system."Simulation and Prediction for Rayleigh Skylight Polarization Distribution (2007)
[15] supported
The polarization pattern of skylight that depends on the sun's position is not visible to humans.
"Durch Streulicht am blauen Himmel entsteht ein für den Menschen nicht sichtbares charakteristisches Muster teilweise polarisierten Lichts, das vom Stand der Sonne abhängig ist."Karl von Frisch
[16] supported
Pernter took measurements of the polarization of skylight, alongside scintillation observations.
"Ebenso nahm er Messungen der Polarisation des Himmelslichtes und Szintillationsbeobachtungen vor"Josef Maria Pernter
[17] supported
Insects such as flies, honeybees, and desert ants can see the polarization pattern of the sky and use it for navigation, unlike humans.
"However, insects e.g. flies, honeybees, desert ants, will be able to see the polarization signature of the sky anduseitfornavigation."PDF e.g. i.e. - bpb-us-e2.wpmucdn.com
[18] supported
The polarimetric signal of scattered light depends on the angle of the incoming sunlight, which is why the sun's position shapes the polarization pattern.
"polarimetric signal is also dependent on the incident angle of the sunlight [3]."PDF e.g. i.e. - bpb-us-e2.wpmucdn.com