The New Moon Illusion

2017 ◽  
Author(s):  
Brian Rogers ◽  
Stuart Anstis
Keyword(s):  
Great Circle ◽  
Cognitive Factors ◽  
The Sun ◽  
The Moon ◽  
Moon Illusion ◽  
Parallel Lines ◽  
Straight Line ◽  
New Moon

When the sun is near the horizon and the moon is visible and higher in the sky, there is a compelling illusion that the sun is not in a direction perpendicular to the boundary between the lit and dark sides of the moon. This New Moon illusion has been observed and discussed previously but without a complete explanation. This chapter argues that both perceptual and cognitive factors contribute to the illusion and that it arises from the fact that the straight line joining the sun and the moon describes a great circle over the flattened dome of the sky. The New Moon illusion also raises the question of how we are able to judge the straightness of extended straight and parallel lines.

scholarly journals How dim is dim? Precision of the celestial compass in moonlight and sunlight

2011 ◽  
Vol 366 (1565) ◽  
pp. 697-702 ◽  
Author(s):  
M. Dacke ◽  
M. J. Byrne ◽  
E. Baird ◽  
C. H. Scholtz ◽  
E. J. Warrant
Keyword(s):  
Dung Beetle ◽  
The Sun ◽  
The Moon ◽  
Polarization Pattern ◽  
Animal Group ◽  
Straight Line ◽  
Celestial Orientation ◽  
Polarization Compass ◽  
Celestial Compass ◽  
Diurnal Species

Prominent in the sky, but not visible to humans, is a pattern of polarized skylight formed around both the Sun and the Moon. Dung beetles are, at present, the only animal group known to use the much dimmer polarization pattern formed around the Moon as a compass cue for maintaining travel direction. However, the Moon is not visible every night and the intensity of the celestial polarization pattern gradually declines as the Moon wanes. Therefore, for nocturnal orientation on all moonlit nights, the absolute sensitivity of the dung beetle's polarization detector may limit the precision of this behaviour. To test this, we studied the straight-line foraging behaviour of the nocturnal ball-rolling dung beetle Scarabaeus satyrus to establish when the Moon is too dim—and the polarization pattern too weak—to provide a reliable cue for orientation. Our results show that celestial orientation is as accurate during crescent Moon as it is during full Moon. Moreover, this orientation accuracy is equal to that measured for diurnal species that orient under the 100 million times brighter polarization pattern formed around the Sun. This indicates that, in nocturnal species, the sensitivity of the optical polarization compass can be greatly increased without any loss of precision.

scholarly journals Astronomy at the service of the Islamic society

2009 ◽  
Vol 5 (S260) ◽  
pp. 514-521
Author(s):  
Ilias M. Fernini
Keyword(s):  
Proper Time ◽  
Astronomical Observatory ◽  
The Sun ◽  
The Moon ◽  
Scientific Institutions ◽  
Mathematical Astronomy ◽  
Islamic Empire ◽  
New Moon ◽  
Islamic Society

AbstractThe Islamic society has great ties to astronomy. Its main religious customs (start of the Islamic month, direction of prayer, and the five daily prayers) are all related to two main celestial objects: the Sun and the Moon. First, the start of any Islamic month is related to the actual seeing of the young crescent after the new Moon. Second, the direction of prayer, i.e., praying towards Mecca, is related to the determination of the zenith point in Mecca. Third, the proper time for the five daily prayers is related to the motion of the Sun. Everyone in the society is directly concerned by these customs. This is to say that the major impetus for the growth of Islamic astronomy came from these three main religious observances which presented an assortment of problems in mathematical astronomy. To observe these three customs, a new set of astronomical observations were needed and this helped the development of the Islamic observatory. There is a claim that it was first in Islam that the astronomical observatory came into real existence. The Islamic observatory was a product of needs and values interwoven into the Islamic society and culture. It is also considered as a true representative and an integral par of the Islamic civilisation. Since astronomy interested not only men of science, but also the rulers of the Islamic empire, several observatories have flourished. The observatories of Baghdad, Cairo, Córdoba, Toledo, Maragha, Samarqand and Istanbul acquired a worldwide reputation throughout the centuries. This paper will discuss the two most important observatories (Maragha and Samarqand) in terms of their instruments and discoveries that contributed to the establishment of these scientific institutions.

A Graphical Approach to Some Problems in Maya Astronomy

1946 ◽  
Vol 12 (1) ◽  
pp. 35-46 ◽  
Author(s):  
Robert H. Merrill
Keyword(s):  
Graphical Methods ◽  
The Sun ◽  
The Moon ◽  
Graphical Approach ◽  
New Moon ◽  
Dresden Codex

Although graphical methods are in common use by engineers and astronomers, they are less familiar to archaeologists. To portray the rhythm of celestial motions, astronomers often use “elongation” diagrams to show angular distances of moon and planets from the sun on each day of the calendar year.The Maya recognized a zone within which the planets could not be seen because of proximity to the brilliant disk of the sun. The moon cannot be seen on the day of conjunction with the sun, and is generally invisible on the day before and the day after this “new moon day.” The three consecutive days in the lunar table of the Dresden Codex may represent the 3-day phase of moon disappearance.

Decapitated Lunar Goddesses in Aztec Art, Myth, and Ritual

1997 ◽  
Vol 8 (2) ◽  
pp. 185-206 ◽  
Author(s):  
Susan Milbrath
Keyword(s):  
Solar Eclipse ◽  
Seasonal Cycle ◽  
Full Moon ◽  
The Sun ◽  
The Moon ◽  
Seasonal Transition ◽  
The Earth ◽  
New Moon ◽  
The Demonic

AbstractAztec images of decapitated goddesses link the symbolism of astronomy with politics and the seasonal cycle. Rituals reenacting decapitation may refer to lunar events in the context of a solar calendar, providing evidence of a luni-solar calendar. Decapitation imagery also involves metaphors expressing the rivalry between the cults of the sun and the moon. Huitzilopochtli's decapitation of Coyolxauhqui can be interpreted as a symbol of political conquest linked to the triumph of the sun over the moon. Analysis of Coyolxauhqui's imagery and mythology indicates that she represents the full moon eclipsed by the sun. Details of the decapitation myth indicate specific links with seasonal transition and events taking place at dawn and at midnight. Other decapitated goddesses, often referred to as earth goddesses with “lunar connections,” belong to a complex of lunar deities representing the moon within the earth (the new moon). Cihuacoatl, a goddess of the new moon, takes on threatening quality when she assumes the form of a tzitzimime attacking the sun during a solar eclipse. The demonic new moon was greatly feared, for it could cause an eternal solar eclipse bringing the Aztec world to an end.

Psychophysical study of the moon illusion in paintings and landscape photos

2021 ◽  
Vol 477 (2245) ◽  
pp. 20200737
Author(s):  
Zoltán Kovács ◽  
Zoltán Udvarnoki ◽  
Eszter Papp ◽  
Gábor Horváth
Keyword(s):  
Angular Diameter ◽  
Solar Disc ◽  
The Sun ◽  
The Moon ◽  
Moon Illusion ◽  
The Real ◽  
The One ◽  
Psychophysical Study

The moon illusion is a visual deception when people perceive the angular diameter of the Moon/Sun near the horizon larger than that of the one higher in the sky. Some theories have been proposed to explain this illusion, but not any is generally accepted. Although several psychophysical experiments have been performed to study different aspects of the moon illusion, their results have sometimes contradicted each other. Artists frequently display(ed) the Moon/Sun in their paintings. If the Moon/Sun appears near the horizon, its painted disc is often exaggeratedly large. How great is the magnitude of moon illusion of painters? How different are the size enlargements of depicted lunar/solar discs? To answer these questions, we measured these magnitudes on 100 paintings collected from the period of 1534–2017. In psychophysical experiments, we also investigated the moon illusion of 10 test persons who had to estimate the size of the lunar/solar disc on 100 paintings and 100 landscape photographs from which the Moon/Sun was retouched. Compared to the lunar/solar disc calculated from reference distances estimated by test persons in paintings, painters overestimated the Moon's size on average Q  = 2.1 ± 1.6 times, while the Sun was painted Q  = 1.8 ± 1.2 times larger than the real one, where Q  =  r painted / r real is the ratio of the radii of painted ( r painted ) and real ( r real ) Moons/Suns. In landscape photos, test persons overestimated the Moon's size Q  = 1.6 ± 0.4 times and the Sun was assumed Q  = 1.7 ± 0.5 times larger than in reality, where Q  =  r test / r real is the ratio of the radius r test estimated by the test persons and the real radius r real of Moons/Suns. The majority of the magnitude of moon illusion Q  = 1.6, 1.7, 1.8, 2.1, 2.8, 2.9 measured by us are larger than the Q -values 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8 obtained in previous psychophysical experiments due to methodological differences.

Mississippian Solstice Shrines and a Cahokian Calendar: An Hypothesis Based on Ethnohistory and Archaeology

1988 ◽  
Vol 8 (3) ◽  
pp. 227-247 ◽  
Author(s):  
Patricia J. O'Brien ◽  
William P. McHugh
Keyword(s):  
Full Moon ◽  
The Sun ◽  
Summer Solstice ◽  
The Moon ◽  
Winter Solstice ◽  
Vernal Equinox ◽  
Religious Ritual ◽  
Autumnal Equinox ◽  
New Moon ◽  
Using Data

This article examines the hypothesis that early Middle Mississippians had a calendric system which tied agriculture and religious ritual together. It also suggests that to that end they built solstice shrines as a means of recording the passage of time through the behavior of the sun and the moon. Using data from structures having possible astronomical alignments, from historic-ethnographic-linguistic sources, and from agricultural planting cycles, a “Cahokian calendar year” is constructed. The year begins with the summer solstice and the Great Busk ceremony. At the next full moon the “great corn” is planted to be harvested at the autumnal equinox. At the winter solstice winter begins while the vernal equinox is marked by a ritual for the Great Sun, their ruler. At the next new moon after that rite a “little corn” is planted which is harvested at the Great Busk. In their five-day, thirteenth month, just before the Busk, all the fires in the society are extinguished to be relit at the summer solstice Great Busk ceremony.

scholarly journals THE RELEVANCE OF USING THE MOON’S AGE AS AN ALTERNATIVE IN IMKANUR RUKYAH CRITERIA

2016 ◽  
Vol XLII-4/W1 ◽  
pp. 209-215 ◽  
Author(s):  
S. Anwar ◽  
K. M. Omar ◽  
M. S. Che Awang
Keyword(s):  
The Sun ◽  
The Moon ◽  
New Moon

The Imkanur rukyah criteria can be defined as the minimum limit in expecting the new moon’s visibility in determining the beginning of Hijri months. It has been used in the development of Hijri calendar in Malaysia since 1992. Based on the criteria, the new moon is considered visible if the altitude at sunset is at least 2&amp;deg; and the elongation between the moon and the sun is at least 3&amp;deg;, or at moonset, the age of the moon is at least 8 hours. The altitude limit of 2&amp;deg; and the elongation limit of 3&amp;deg; indeed were determined according to the data of new moon visibility observed in Indonesia, whereas for the 8-hour moon’s age, there is no written rule regarding to it. The use of the moon’s age criterion as an alternative to the geometric criteria can lead to confusion if both conditions provide different results. Therefore, this study was performed to assess the relevance of using moon’s age as an alternative in <i>Imkanur rukyah</i> criteria used in Malaysia. The study utilised the data of the sun and the moon’s positions, the time of sunset, the time of moonset and the time of conjunction (new moon). The data for the sun were calculated based on VSOP87 theory, while for the moon, using ELP2000-82b. Based on the analysis, in determining Hijri dates from 1996 to 2015, there are 22 discrepancies found between the moon’s age and the geometric criteria, in which, 5 of them occur in the month of Ramadan, Syawal and Zulhijjah. These conditions show that the moon’s age criterion is not always consistent with the geometric criteria. Therefore, the use of moon’s age as an alternate criterion in determining the beginning of Hijri month is considered irrelevant and should be further reviewed.

scholarly journals The moon phases influence on the beginning of astronomical dawn determination in Yogyakarta

2017 ◽  
Vol 2 (1) ◽  
pp. 1
Author(s):  
Abu Yazid Raisal ◽  
Yudhiakto Pramudya ◽  
Okimustava Okimustava ◽  
Muchlas Muchlas
Keyword(s):  
Full Moon ◽  
Moving Average ◽  
Weather Condition ◽  
The Sun ◽  
The Moon ◽  
Moon Phases ◽  
Brightness Level ◽  
Sky Brightness ◽  
New Moon ◽  
The Difference

<p class="Abstract">In astronomy, there are three types of dawn. They are astronomical, nautical, and civil dawn. The sunlight is starting to appear on the east horizon when the Sun altitude is 18<sup>o</sup> below the horizon. Hence, there is a change on the sky brightness. The sky brightness can be affected by the moon phases. The sky brightness level is monitored by Sky Quality Meter (SQM). The SQM was installed upward to the zenith. There are 4 locations of measurement in Yogyakarta. The data has been collected for nine months to obtain the complete moon phases. The beginning of astronomical dawn is time when the sky brightness level is starting to decrease. The moving average algorithm was employed to determine the beginning of astronomical dawn. The time when the astronomical dawn begins is compared with the sun altitude calculation. The sun altitude calculation has been done using accurate times software. The difference of the beginning of astronomical dawn by measurement and calculation are 18.61±6.81 minutes, 19.12±3.28 minutes, 31.12±7.76 minutes, and 27.24±8.04 minutes, on the new moon (0), on the first quarter (0.25), on the full moon (0.5) and on the last quarter (0.75), respectively. The weather condition is also contributing to the results.</p>

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