Astronomical Base Research Articles

Macroevolutionary and macroecological response of Iberian rodents to late Neogene climatic oscillations and events

Biozones are routinely used for chronological purposes, but their nature is seldomly questioned. Here, we attempt to find the evolutionary-ecological basis for Iberian rodent biozones for the interval 8.5–2 Ma based on currently available paleontological, stratigraphic and paleoclimatic information. Our comparison of biozone boundary age uncertainty intervals to records of marine SST, δ18O and δ13C, terrestrial hydrological proxies and astronomical parameters suggests an orbitally forced climatic origin for the majority of biozones. Zone boundary ages during the late Miocene are mostly associated with humidity changes during 1.2-Myr obliquity nodes and 405-kyr eccentricity minima. Tectonics and strong regional cooling may additionally explain faunal change during the Messinian (7–5 Ma). A partly reversed pattern characterizes most Pliocene zone boundaries, which are mostly associated with wetter conditions during obliquity nodes and 405-kyr eccentricity maxima. A third configuration culminates in the early Pleistocene and consists of the combination of strong obliquity amplitude maxima and 2.4-Myr eccentricity minima. It is suggested that larger-scale, European Neogene mammal (MN) units have an astronomical basis as well, with an important role of 2.4-Myr eccentricity cycle and the 1.2-Myr obliquity cycle, with the latter becoming especially important after the mid-Miocene cooling (~14 Ma). Whereas rodent events on the Iberian Peninsula during the late Miocene are shaped by replacements within resident communities dominated by dry-adapted clades of true mice (Murinae) and hamsters (Cricetinae), transitions during the cooler Pliocene involve invasions of newly emerging Eurasian clades of ‘microtoid hamsters’ and voles (Arvicolinae) preferring wetter and cooler environments. A new model of stepwise clade displacement is proposed in which the combination of long-period Milankovitch cycles and gradual long-term climatic change allows for the periodic functioning of migration corridors, along which increasingly pervasive dispersal events by members of new clades cause the gradual extinction of old clades.

Tilt Angle Adjustment for Incident Solar Energy Increase: A Case Study for Europe

The work presented in this paper aims to analyze the efficiency of using optimum tilt angles defined for several time intervals to maximize the incident solar irradiation on a certain surface deployed in Europe. Such a technique would improve the solar energy harvesting process, both for photovoltaic panels and solar thermal collectors, while not investing in the more expensive sun-tracking devices. The optimum tilt angles have been determined for the yearly, bi-annual, seasonal, and monthly time intervals, which were delimited on a calendar and astronomical base, respectively, considering multiple locations from Europe, and using various mathematical models based on empirical equations and solar irradiation estimation. The total incident solar irradiation provided by adjusting the tilt angle multiple times per year was calculated and compared to that obtained when using the yearly optimum tilt angle. The gains for each type of adjustment were investigated, and the monthly optimization of the tilt angle is obviously the most effective one, ensuring gains of up to 7%, depending on the considered latitude. Otherwise, an optimization twice per year, using the bi-annual optimum tilt angles determined for the astronomical-defined warm and cold seasons, would be the next best solution.

Time scales, their users, and leap seconds

Numerous time scales exist to address specific user requirements. Accurate dynamical time scales (barycentric, geocentric and terrestrial) have been developed based on the theory of relativity. A family of time scales has been developed based on the rotation of the Earth that includes Universal Time (specifically UT1), which serves as the traditional astronomical basis of civil time. International Atomic Time (TAI) is also maintained as a fundamental time scale based on the output of atomic frequency standards. Coordinated Universal Time (UTC) is an atomic scale for worldwide civil timekeeping, referenced to TAI, but with epoch adjustments via so-called leap seconds to remain within one second of UT1. A review of the development of the time scales, the status of the leap-second issue, and user considerations and perspectives are discussed. A description of some more recent applications for time usage is included.

The Astronomical Basis of Egyptian Chronology of the Second Millennium BC

Abstract Egyptian dates are widely used for fixing the chronologies of surrounding countries in the Ancient Near East. But the astronomical basis of Egyptian chronology is shakier than generally assumed. The moon dates of the Middle and New Kingdom are here re-examined with the help of experiences gained from Babylonian astronomical observations. The astronomical basis of the chronology of the New Kingdom is at best ambiguous. The conventional date of Thutmose III’s year 1 in 1479 BC agrees with the raw moon dates, but it has been argued by several Egyptologists that those dates should be amended by one day, and then the unique match is 1504 BC. The widely accepted identification of a moon date in year 52 of Ramesses II, which leads to an accession of Ramesses II in 1279 BC, is by no means certain. In my opinion that accession year remains nothing more than one of several possibilities. If one opts for a shortened Horemhab reign, dating Ramesses II to 1290 BC gives a better compromise chronology. But the most convincing astronomical chronology is a long one: Ramesses II in 1315 BC, Thutmose III in 1504 BC. It is favored by Amarna-Hittite synchronisms and a solar eclipse in the time of Muršili II. The main counter-argument is that this chronology is at least 10–15 years higher than what one calculates from the Assyrian King List and the Kassite synchronisms. For the Middle Kingdom on the other hand, among the disputed dates of Sesostris III and Amenemhet III one combination turns out to be reasonably secure: Sesostris III’s year 1 in 1873/72 BC and Amenemhet III’s 30 years later.

Celebration of seasonally based holidays and festivals in Japan: a study in cultural adaptation

AbstractThe way in which Japan adopted methods and practices related to celebrations of seasonally based holidays and festivals provides an interesting study in how one culture may incorporate and modify the astronomically related practices of another. This article explores this process by looking at: (1) astronomical bases of seasonal celebration in Japan, (2) Japanese values and adaptations of imported icons and practices, (3) changes in celebratory practice due to adoption of ‘Western’ methods, and (4) observation in modern Japan.

Separation of atmosphere‐ocean‐vegetation feedbacks and synergies for mid‐Holocene climate

We determine both the impact of atmosphere‐ocean and atmosphere‐vegetation feedback, and their synergy on northern latitude climate in response to the orbitally‐induced changes in mid‐Holocene insolation. For this purpose, we present results of eight simulations using the general circulation model ECHAM5‐MPIOM including the land surface scheme JSBACH with a dynamic vegetation module. The experimental set‐up allows us to apply a factor‐separation technique to isolate the contribution of dynamic Earth system components (atmosphere, atmosphere‐ocean, atmosphere‐vegetation, atmosphere‐ocean‐vegetation) to the total climate change signal. Moreover, in order to keep the definition of seasons consistent with insolation forcing, we define the seasons on an astronomical basis. Our results reveal that north of 40°N atmosphere‐vegetation feedback (maximum in spring of 0.08°C) and synergistic effects (maximum in winter of 0.25°C) are weaker than in previous studies. The most important modification of the orbital forcing is related to the atmosphere‐ocean component (maximum in autumn of 0.78°C).

Monsoon rainfall forecasting of Saurashtra on astronomical basis

Monsoon rainfall forecasting of Saurashtra on astronomical basis

Astronomy of the vedic altars

In this paper, two ancient Indian texts, the Śatapatha Brāhmana and the Rigveda, are examined for their astronomical content. It is argued that the 95 year ritual of agnicayana had an astronomical basis, which implies a knowledge of the length of the tropical year being equal to 365.24675 days. An astronomical code has been discovered in the structure of the Rigveda, which has been partially deciphered. This code expressed the knowledge that the sun and the moon are about 108 times their respective diameters away from the earth. This analysis leads to a major revision of our understanding of the history of ancient astronomy.

Apollo 16: The Moon as an Astronomical Base

Apollo 16: The Moon as an Astronomical Base

Unusual Aerial Phenomena

Over a period of years, diverse aerial sightings of an unusual character have been reported. On the assumption that the majority of these reports, often made in concert, come from reputable persons, and in the absence of any universal hypotheses for the phenomena which stimulated these reports, it becomes a matter of scientific obligation and responsibility to examine the reported phenomena seriously, despite their seemingly fanciful character. Accordingly, several hundred serious reports of “unidentified aerial objects” have been studied in detail in an attempt to get a pattern classification. It appears that those reported phenomena which do not admit of a ready and obvious explanation exhibit fairly well-defined patterns and that these are worthy of further study. One pattern in particular, that of a hovering nocturnal light, does not appear to be readily explainable on an astronomical basis, or by mirages, balloons, or by conventional aircraft.