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Benvenuti in queste pagine dedicate a scienza ed arte. Amelia Carolina Sparavigna

Friday, December 9, 2016

Images - Mars Science Laboratory

Images - Mars Science Laboratory

Alveolar Stones on Mars



Curiosity - Sol 1403


Adjusted

Green stone of Mars


Curiosity Sol 1505

Curiosity Rover Finds and Examines a Meteorite on Mars

Alveoli in the stone - Mars

Here magnificent alveoli in the stone on MARS. Curiosity Sol 1523


Note the bright lines which are segmenting the stone!
Wonderful.

http://mars.jpl.nasa.gov/msl/multimedia/raw/?rawid=1523MH0003690000600330R00_DXXX&s=1523.76560068931

Again, we have a sort of honeycomb weathering. "Honeycomb weathering, also known as fretting, cavernous weathering, alveoli/alveolar weathering, stone lattice, stone lace or miniature tafoni weathering (Mustoe, 1982) is a form of salt weathering common on coastal and semi-arid granites, sandstones and limestones (Mustoe 1982)." https://en.wikipedia.org/wiki/Honeycomb_weathering



Martian Curiosity


"Martian Wood"

Of course, this is not wood. This formation is interesting because it looks like a sort of  honeycomb weathering.  "Honeycomb weathering, also known as fretting, cavernous weathering, alveoli/alveolar weathering, stone lattice, stone lace or miniature tafoni weathering (Mustoe, 1982) is a form of salt weathering common on coastal and semi-arid granites, sandstones and limestones (Mustoe 1982)."  https://en.wikipedia.org/wiki/Honeycomb_weathering

Curiosity Sol 1523



Martian Curiosity

Curiosity Sol 1537.




"Snake"

This is a very interesting rock formation. When the image is enhanced,  the colours make it looking like a "snake". 

We can see a stone of the same kind in other images of Curiosity - Sol 1514






Monday, November 21, 2016

Fantastic Research and Where to Find It

Fantastic Research and Where to Find It


Very interesting on SSRN BLOG


If we haven’t already sent you running to do a QuickSearch for “Harry Potter” in the eLibrary then perhaps we can interest you with some choice titles we found there. Without further ado:
Our Favorite Harry Potter Themed Titles Available on SSRN
millennials-6

Saturday, September 10, 2016

Ales Stenar and the Moon

The Ales Stenar, known in English as the Ale’s Stones, is an ancient megalithic monument of Sweden. The stones are outlining a ship. The paper
"Astronomical Alignments of Ales Stenar Along Sunset and Moonset Directions"
shows alignments of the stones along the northern possible moonset on major and minor lunar standstills. These astronomical alignments are shown using the Photographer’s Ephemeris. It is possible that this megalithic monument was used for observing the cycles of the moon.

In this image, we can see the left side of the Ales Stenar and the direction of the northern moonset (blue line) on a major lunar standstill, represented by the blue line. Note the alignment of the stones along this direction.

Here, we can see the right side of the Ales Stenar and the direction of the northern moonset (blue line) on a minor lunar standstill, represented by the blue line. Note the alignment of the stones along this direction.

The images are snapshots of the results of Photographer's Ephemeris. In the images, the yellow and orange lines are giving the directions of sunrise and sunset on the days of lunar standstills.

On the summer solstice, we have the main axis of Ales Stenar oriented along the sunset. In the following image, this direction is given by the orange line. 




Wednesday, September 7, 2016

A skyscraper as a huge diffraction grating

The Intesa Sanpaolo Tower in Torino behaves like a huge "diffraction grating". The facade is a doudle-skin one, the outer skin being mabde by a steel frame an orientable transparent panels. This outer skin  becomes a huge optical device.
The south side has only the central part covered by the doudle-skin. The rest is covered by photovoltaic panels. In the proper incident sunlight,  we can see the central part dispersing the white light in colored beams. Here two images of the phenomenon.



The sequence lasts 10 minutes. 

For more details, read please this article
A skyscraper as a huge diffraction grating

Wednesday, August 24, 2016

Vito Volterra

Vito Volterra and his commemoration for the centenary of Faraday's discovery of electromagnetic induction, https://hal.archives-ouvertes.fr/hal-01353959/

Wednesday, June 15, 2016

On the Karnak Temple and the Sun Hierophany

The Karnak Temple and the Motion of the Earth's Axis

Article published on SSRN Journal.
Abstract: The Karnak Temple complex comprises a vast mix of temples, chapels and other buildings. Its construction began during the reign of Senusret I in the Middle Kingdom and continued during the Ptolemaic period. The temple was the main place of worship the Amun-Ra, the Sun God. Not surprisingly his temple has its axis aligned along the sunrise azimuth on the winter solstice. Here we will discuss how the motion of the Earth’s axis has altered, in four thousand years, this alignment of half a degree.



Sun hierophany at the temple on the winter solstice

Sunday, June 12, 2016

Newgrange and the axial tilt


The Newgrange  stone age passage tomb on the Winter Solstice is described by the site:
Above the entrance to the passage at Newgrange there is an opening. This opening allows sunlight to penetrate the passage and chamber at sunrise around the Winter Solstice. A narrow beam of light penetrates the opening and reaches the floor of the chamber, "gradually extending to the rear of the passage. As the sun rises higher, the beam widens within the chamber so that the whole room becomes dramatically illuminated. After 17 minutes the sunbeam leaves the chamber and retreats back down the passage. When Newgrange was built over 5000 years ago, the winter solstice sunbeam would have made its way to the back recess of the central chamber. Due to changes in the tilt of the Earth's axis the sunbeam now stops 2 metres from the back recess". 
What is this tilt? It is the obliquity of the ecliptic. Here in the figure we can see it.


The angle of the Earth's axial tilt varies with respect to the plane of the Earth's orbit. These slow 2.4° obliquity variations are roughly periodic, taking approximately 41,000 years to shift between a tilt of 22.1° and 24.5° and back again. Currently the Earth is tilted at 23.44 degrees, decreasing. 
At the time of Newgrange building, the til was of about 24 degrees.


If we want to evaluate the effect of this tilt shift on the sunrise and sunset azimuths on solstices, at the Newgrange latitude, the influence of the tilt on the sunrise azimuths on solstice is about a degree.  This explains the two metres back from recess.

Hardknott fort sunrises on summer solstice

As told by Ben Johnson on the Hardknott Roman Fort at 
"A trip to the Roman fort at Hardknott in Cumbria is probably not for those of a nervous disposition!! The drive up the steep, winding, narrow road through Hardknott and Wynose passes is often tricky and always a little frightening ... , but this adds to the experience, as the setting of the fort is spectacular and the scenery incredible."

I would like to add something to these worlds.
Let me use the following shapshot from the Photographer's Ephemeris.


We can see how the Roman fort wakes up on the summer solstice.
Viewed from the center, the sun rises along the direction of the NE gate.
The sunset corresponds to the NW gate.
This year the moon is 98%, that is full moon! Fantastic!

More on the Hardknott fort at

Saturday, June 11, 2016

On precession

Polaris is the brightest star in the constellation Ursa Minor. Very close to the north celestial pole, it is currently the pole star. But Odysseus, the Greek king of Ithaca, and the ancient mariners, did not use this star for their voyages. Why? because of precession (cerchio che più tardi in cielo è torto).

a very detailed and clear discussion on precession, with illustrations,

Here I am adapting a part of this excellent discussion.

The Earth is like a spinning top. Then the Earth’s rotational axis gyrates, with a period of 26,000 years. This motion is called axial precession, or "precession of the equinoxes".  Precession occurs because the Sun's gravity induces torque, which pulls the Earth's equatorial bulge toward the ecliptic. 
The axis of precession is perpendicular to the ecliptic and is aligned with the ecliptic axis. This axis projects to two points, the north and south ecliptic poles, which are inclined 23.5º to the celestial poles.

Note that axial precession affects the direction of the Earth's axis, but it does not affect the angle of its tilt relative to the ecliptic. Thus, precession affects the time of year in which various constellations are visible. The precssion does not affect the axis tilt, which is constant, and so the seasons themselves continue just like they are now.

Our standard Gregorian calendar is based on the solar, or tropical year, the time it takes the Sun to return to the same equinox, which is defined by the direction of the Earth's axis relative to the Sun. Since the seasons are intrinsic to the tropical year, our Gregorian calendar is calibrated so that the March equinox always falls on either March 20 or 21. This forces the seasons to occur during the same months, regardless of precession. However, the stars visible in the evening will slowly change. Figure 1 (of the given link) shows the winter solstice in the north, with the constellation Taurus prominent at midnight. If the Earth's axis were pointing in the opposite direction, Taurus would still be prominent at midnight, but it would be the summer solstice. So, for the solar calendar, the seasons occur in the same months, but we view different constellations during those months.

Besides the axial precession of 26,000, there is also a small oscillation of the tilt. Taking approximately 41,000 years the tilt shifts from 22.1° to 24.5° and back again. Currently the Earth is tilted at 23.44 degrees,  decreasing. If we want to evaluate the effect of this tilt shift on the sunrise and sunset azimuths on solstices, for instance at the Newgrange latitude, for Newgrange passage tomb that was built 5,000 ago, the influence of the tilt on the sunrise azimuths on solstice is about a degree (see  http://stretchingtheboundaries.blogspot.it/2016/06/newgrange-and-axial-tilt.html )