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We present another explanation for the moon illusion, the phenomenon in which the moon looks larger near the horizon than near the zenith. In our model of the moon illusion, the sky is considered a spatially-contiguous and…
The Moon often appears larger near the perceptual horizon and smaller high in the sky though the visual angle subtended is invariant. We show how this illusion results from the optimization of a projective geometrical frame for conscious…
It is straightforward to determine the size of the Earth and the distance to the Moon without making use of a telescope. The methods have been known since the 3rd century BC. However, few amateur or professional astronomers have worked this…
Following a technique of Galileo we compute the height on a mountain on the Moon. It is based on a simple observation that precisely on a half Moon day, the Earth, the Moon, and the Sun form the vertices of a right triangle with the Moon at…
Modern observations based on general relativity indicate that the spatial geometry of the expanding, large-scale Universe is very nearly Euclidean. This basic empirical fact is at the core of the so-called "flatness problem", which is…
The lunar surface is a compelling location for large, distributed optical facilities, with significant advantages over orbital facilities for high spatial resolution astrophysics. The serious development of mission concepts is timely…
High angular resolution holds the key to extending our knowledge in several domains of astronomical research. In addition to the development of new instruments, advancements in post-processing algorithms can enhance the performances…
The uniform image of the full moon is well known from the beginning of history. In the last decades, there are photos with a similar configuration of the earth observed from the moon and from space, as well as of all the planets and their…
We look at what astronomy from the Moon might be like in the visible over the next few decades. The Moon offers the possibility of installing large telescopes or interferometers with instruments larger than those on orbiting telescopes. We…
The lunar surface allows a unique way forward in cosmology, to go beyond current limits. The far side provides an unexcelled radio-quiet environment for probing the dark ages via 21 cm interferometry to seek elusive clues on the nature of…
The lunar surface has historically been considered an optimal site for a broad range of astronomical telescopes. That assumption, which has come to be somewhat reflexive, is critically examined in this paper and found to be poorly…
The Outer Space Treaty makes it clear that the Moon is the province of all mankind, with the latter ordinarily understood to exclude state or private appropriation of any portion of its surface. However, there are indeterminacies in the…
The Moon is our future. It may seem like a chimera with a projected cost in excess of 100 billion\$, and counting, dispensed on ARTEMIS with little to show to date. However it is the ideal site for the largest telescopes that we can dream…
It will be shown that the rotation of the Earth in the Earth-Moon system can be detected by comparing the deflection of a Foucault pendulum at noon on the one hand and at midnight on the other hand. More precisely, on 21 June the midnight…
The global 21 cm signal from the hyperfine transition of cosmic atomic hydrogen is theorised to track the state of the early Universe via the analysis of its absorption and emission with respect to the radio background. Detecting this…
In July 5th 2014 an occultation of Mars by the Moon was visible in South America. Citizen scientists and professional astronomers in Colombia, Venezuela and Chile performed a set of simple observations of the phenomenon aimed to measure the…
Elevation has long been the standard for quantifying the relief of mountains and other landforms on Earth and beyond. Nevertheless, elevation has its limitations. By itself, a location's elevation reveals little about its vertical position…
Ptolemy's model of the Moon's motion implied that its distance varies by nearly a factor of two, implying that its angular size should also vary by nearly a factor of two. We present an analysis of 100 naked eye observations of the Moon's…
An interesting test on the nature of the Universe is to measure the global spatial curvature of the metric in a model independent way, at a level of $|\Omega_k|<10^{-4}$, or, if possible, at the cosmic variance level of the amplitude of the…
Although they are sometimes considered problematic to grasp by students, the concepts behind non-Euclidean geometry can be taught using astronomical images. By using photographs of the Moon taken with a smartphone through a simple…