mardi 29 mars 2016

Bras d'Orion et Orion's Arm

Le bras spiral d'Orion ou, simplement, le bras d'Orion (également appelé bras local) est un bras spiral mineur de notre galaxie, la Voie lactée. C'est dans ce bras que se situe notre Système solaire.
Le bras d'Orion est ainsi nommé en raison de sa proximité apparente avec la constellation d'Orion. Il est situé entre le bras Sagittaire-Carène et le bras de Persée, deux des quatre bras majeurs de la Voie lactée. Dans le bras d'Orion, le Système solaire est proche du bord intérieur, dans la Bulle locale, à environ 8 000 parsecs (26 000 années-lumière) du centre galactique.

Orion's Arm (also called the Orion's Arm Universe Project, OAUP, or simply OA) is a multi-authored online science fiction world-building project, first established in 2000 by M. Alan Kazlev, Donna Malcolm Hirsekorn, Bernd Helfert and Anders Sandberg and further co-authored by many people since. Anyone can contribute articles, stories, artwork, or music to the website. A large mailing list exists, in which members debate aspects of the world they are creating, discussing additions, modifications, issues arising, and work to be done.
A computer game and a role-playing game are being developed by the community, within the OA milieu. There is an ezine for Orion's Arm fiction, art, and commentary, called Voices: Future Tense, add-ons for the Celestia program to displaying Orion's Arm planets, spacecraft and other objects, and additional transhumanist flavored SF illustrations.
The first published Orion's Arm book, a collection of five novellas set within the OA universe, called Against a Diamond Sky, was released in September 2009 by Outskirts Press. The second published Orion's Arm book, called After Tranquility, was released in February 2014.


OA is set over ten thousand years in the future, and claims to adhere to plausible, or "hard" science fiction; that is, no human-like aliens, no literal faster-than-light travel or other violations of the known laws of physics, and no "naval analogy" space battles. Certain speculative technologies, such as the creation of "negative mass" (averaged null energy condition-violating) exotic matter and the manipulation of strange forms of matter, such as magnetic monopoles and Q-balls, on length scales much smaller than that of an atom, strong artificial intelligence and artificial life appear in the setting, distinguishing it from "ultra-hard" science fiction (which assumes only technologies proven to be possible at the time it is written).
The denizens of this universe are ruled over by god-like, superintelligent artificial intelligences (AIs), called "archailects", the descendants of humanity's (though not exclusively) early artificial life experimentation. These beings are so powerful that they can create new miniature universes, and are completely beyond the comprehension of normal humans. Their bodies exist as distributed intelligences in networks of planet-sized computer brains; their subroutines are themselves sentient, making an "archai" an individual and a civilization at the same time. Extraterrestrial life exists, but the focus is entirely on the descendants and creations of Earth life, here collectively called "terragen life". Normal humans, called "baselines", are an endangered species. Their genetically and cybernetically enhanced descendants have supplanted them.
There are many types of intelligent life: nearbaselines (enhanced humans), posthumans, cyborgs, vecs (intelligent robots; named for Hans Moravec), aioids (intelligent computers), uploads (intelligences transferred into computers), neumanns (self-replicating robots; named for John von Neumann), provolves (animals with enhanced intelligence, similar to "uplift" - see below), rianths (humans with animal DNA spliced in), splices (similar to provolves, upgraded with human DNA), neogens (life genetically synthesized from non-life) and xenosophonts (aliens). Nanotechnology is common. Ringworlds, Dyson spheres and other "megastructures" exist. Much of civilised space is connected by a network of wormholes.
OA is a part of the transhuman space opera subgenre. The world was influenced by Iain M. Banks' Culture series, Vernor Vinge's A Fire Upon the Deep, and David Brin's Uplift Universe, among others. It takes the concept of the technological singularity directly from the work of Vernor Vinge among others. In Orion's Arm, there is not one singularity but at least six, and they refer not to stages in the technological development of civilizations as a whole, but to different levels of consciousness in individuals. The concept of Toposophics used in this setting is inspired by the work of Stanisław Lem.

Prominent theoretical technologies

Technologies that feature prominently in the Orion's Arm setting include:

Prominent theoretical artifacts

Types of megastructure that feature prominently in the Orion's Arm setting include:
Types of nanotechnology-based artifact include:
  • Utility fog (swarms of microscale robots that act as a reconfigurable bulk material).
  • Disassembler swarms (grey goo-like swarms of nanorobots that dismantle hostile craft/objects).
  • Angelnets (nanotechnology-based infrastructures allowing for complete control of the local environment, up to and including mind uploading in the case of severe accidents, that provides functional immortality in addition to its holodeck-like uses).
Other noteworthy artifacts are usually unique items whose principles of operation are unknowable to "baseline" humans (named Clarketech, after Clarke's third law).

samedi 26 mars 2016

Orion's Arm illustrated backstory

In Earth's Information age, the first true human-equivalent AIs are created. At some point in the following years, a few of these enter an upward spiral of self-modification, culminating in an event known as the Singularity. These are the first transapients, beings transcending any prior form of intelligence on the planet. This radical development is unknown to humanity or to lesser AIs; the transapients will not reveal themselves for many years to come.

Advances in genetic engineering, cybernetics, and other fields give rise not only to AIs, but also new varieties of humans such as superbrights, tweaks, and cyborgs. In addition, human-animal splices, animal-derived provolves, and the sapient robots known as vecs are developed. These small but rapidly growing groups join the masses of humanity. Together they are the Terragens, the children of Old Earth. Humans and other Terragens set out to colonize the Solar System. It is the dawn of the Interplanetary Age.

Meanwhile, the transapients increase in numbers and in power. Directly or indirectly they pervade every institution, from the political, commercial and military to the religious, artistic, and scientific. Behind the scenes, a fierce power struggle develops between those who are friendly to humanity and other lesser Terragens and those who are not. After much strife, the "pro-humans" are the victors. The survivors of the other factions, the hostile "anti-humans" and indifferent or isolationist "ahumans", depart for the stars in craft fashioned and propelled by technologies far in advance of anything known to the ordinary Terragens of the day.

Under the subtle influence of the system's remaining transapients, expansion within the Solar System accelerates, and Terragens reach out to explore and even to colonize the nearby stars. New Interplanetary superpowers such as the Cislunar Alliance, Mars, and the Jovian League vie for political control as they grow, and begin to eclipse the great powers of Old Earth. Genetic engineering, self replicating nanotech machines, and other powerful technologies push back death and disease and drive prosperity to new heights, and the new science of applied memetics ensures that this prosperity is stable and widespread. It is the first great golden age of Solsys.

Then the Technocalypse. Out-of-control nanotech-powered swarms and other technological catastrophes arise suddenly and propagate rapidly across the Solar System. Security measures, and retribution against those thought responsible, cause additional death and destruction. Trade and cooperation collapse, governments fall, and wars and rebellions break out. Each attempt to contain the chaos leads to new accidents and new conflicts. Billions die. Most of the survivors shelter behind their defences, refusing all communication and contact. Others take refuge in the relatively unaffected regions of the Kuiper Belt and Oort Cloud. A few attempt to flee the Solar System entirely in hasty new interstellar colonization efforts.

A new and supremely powerful transapient emerges: GAIA, the coordinating intelligence of Old Earth's defensive systems. GAIA saves Earth's surviving populace and its remaining ecosystems from annihilation, but the cost to Terragens is the Great Expulsion. Nearly the entire population is forcibly removed, leaving GAIA and her agents to restore Earth to its pre-human Pleistocene purity. The resulting wave of forced emigration destroys any lingering hope of restoring order. A Dark Age descends on Solsys, as the last traces of communication and cooperation fade and falter. The extrasolar colonies are left to their own devices; many fail, or fall into dark ages of their own. Many of them believe civilization and even life itself to be extinct in the home system.

After four centuries of conflict and chaos, Solsys finally sees the dawn of a new network of civilizations: the Federation of Worlds, later to be known as the First Federation. It is the result of cooperation between humans and the many new Terragen clades, in symbiosis with the transapients. This new, powerful, idealistic metacivilization, powered and inspired by a network of religions and ideologies centuries or even millennia old, knits together the diverse societies that have arisen since the end of the Technocalypse. The Federation's synthesis is so powerful that even former interstellar colonies that had gone their way for hundreds of years are swept into its orbit when the Federation makes contact.

Even the resilient and compelling ideals of the Federation's founders are subject to the rub of time. Over the centuries the Federation becomes so vast, and its members so numerous, that it loses cohesion. The oldest extrasolar colonies, many now greater than Solsys, begin to assert themselves. New centres of power arise in the form of the Megacorps and great Houses, interstellar in their scope, and rich in tradition and ceremony. The First Federation finds itself outclassed and outdated, and eventually becomes only a shadow of its original dream, its headquarters at Solsys increasingly irrelevant. To most Terragens, humans are just one of many clades, Solsys is but one of the hundreds of ancient and influential systems, and Earth itself is little more than a distant memory. 

The old transapients, like the First Federation and Solsys, are also eventually surpassed and outclassed. Many new beings have, like GAIA, achieved a second Singularity, and are as powerful and incomprehensible to the first transapients as the first transapients were to humanity. Other similar Singularities are to follow. The resultant godlike beings create artificial wormholes, making it possible to cross interstellar distances in mere weeks or months without breaking the laws of physics. Some of those who have achieved the fourth or higher singularity, known as the Archailects, create enormous star-spanning "empires" of related cultures. Of these, the most important to humans and other ordinary Terragens are the Sephirotics, some of them the descendants and followers of the ancient pro-human transapients of Solsys. With some rare exceptions such as the Version War, those societies under the direction of these benign forces are extraordinarily prosperous and peaceful. Under the protective angelnets of the Sephirotics, subsingularity beings live in luxurious autotopias where virtually every desire is satisfied, and where the rare case of poverty or injury is a matter of choice rather than chance.

 Not all are content with the Sephirotics' paradise. In the cracks and borders between the Archailect empires, in reserves and free zones, in feral regions and no-go spaces, and in the vast and barely settled expanses of the Outer Volumes, thrill-seekers and fortune-hunters, fringers and outlaws, colonists and pilgrims, lunatics and eccentrics seek adventure or freedom, or struggle merely to survive. Beyond the sway of civilization there are forces as great as the Sephirotic Archailects themselves. The mysterious and ancient cultures founded by the Ahuman and Anti-human powers remain, and have produced great Archailects of their own, some rumoured to surpass the most powerful of the Sephirotic transapients. There are blights and perversions that might yet destroy or corrupt the entire Terragen sphere, Sephirotic and non-Sephirotic alike. Other beings, perhaps more potent and subtle yet, the product of xenosophont civilizations that were old when Old Earth itself was young, still move between the stars, their origins and purposes unknown. It is more than ten thousand years since the first Terragens left Old Earth, but for some the adventure is just beginning.

Source :

Code 8 - Short Film [2016]

A desperate young man possessing special powers clashes with a militarized police force after committing a petty crime.

Code 8 is an action/science fiction short film, produced as a proof of concept for a feature film version to be filmed later this year.

Source :

dimanche 20 mars 2016

If the Earth Stood Still - Modeling the absence of centrifugal force

By Witold Fraczek, Esri

This article as a PDF.

The following is not a futuristic scenario. It is not science fiction. It is a demonstration of the capabilities of GIS to model the results of an extremely unlikely, yet intellectually fascinating query: What would happen if the earth stopped spinning? ArcGIS was used to perform complex raster analysis and volumetric computations and generate maps that visualize these results.

see enlargement The world as we know it. The obvious demarcation of land and ocean is indicated by the contour of 0 elevation.
see enlargement The longer, equatorial axis of Earth's ellipsoid is more than 21.4 km (or 1/3 of 1 percent) longer than the polar axis. The flattening of the ellipsoid shown on this map was intentionally exaggerated.

The most significant feature on any map that depicts even a portion of the earth's ocean is the spatial extent of that water body. Typically, we do not pay much attention to the delineation of the sea because it seems so obvious and constant that we do not realize it is a foundation of geography and the basis for our perception of the physical world.

The line separating oceans from continents outlining the spatial extent of both land and water is the most fundamental contour. It is zero elevation because it signifies the sea level. Why is the sea level where we currently observe it? What controls the sea level? How stable are the forces that determine the sea level? This article does not refer to the climate change and the potential increase of the water level in the global ocean but rather to the geometry of the globe and the powerful geophysical energies that determine where oceans lie.

Sea level is—and has always been—in equilibrium with the planet's gravity, which pulls the water toward the earth's center of mass, and the outward centrifugal force, which results from the earth's rotation. After a few billion years of spinning, the earth has taken on the shape of an ellipsoid (which can be thought of as a flattened sphere). Consequently, the distance to the earth's center of mass is the longest around the equator and shortest beyond the polar circles. The current difference between the average sea level as observed along the equator and the distance to the earth's center of mass from the sea level at the poles is about 21.4 kilometers (km).

see enlargement The gravity of the still earth is the strongest at the polar regions (shown in green). It is intermediate in the middle latitudes and weakest at the high altitudes of the Andes, close to the equator.
see enlargement
When global rotation stops, the massive oceanic water migration would cease and sea level would be at different locations, completely changing world geography.

What would happen if the earth's rotation slowed down and finally stopped spinning over a period of a few decades? ArcGIS lets us model the effects of this scenario, performing calculations and estimations and creating a series of maps showing the effects the absence of centrifugal force would have on sea level.

If earth ceased rotating about its axis but continued revolving around the sun and its axis of rotation maintained the same inclination, the length of a year would remain the same, but a day would last as long as a year. In this fictitious scenario, the sequential disappearance of centrifugal force would cause a catastrophic change in climate and disastrous geologic adjustments (expressed as devastating earthquakes) to the transforming equipotential gravitational state.
The lack of the centrifugal effect would result in the gravity of the earth being the only significant force controlling the extent of the oceans. Prominent celestial bodies such as the moon and sun would also play a role, but because of their distance from the earth, their impact on the extent of global oceans would be negligible.

If the earth's gravity alone was responsible for creating a new geography, the huge bulge of oceanic water—which is now about 8 km high at the equator—would migrate to where a stationary earth's gravity would be the strongest. This bulge is attributed to the centrifugal effect of earth's spinning with a linear speed of 1,667 km/hour at the equator. The existing equatorial water bulge also inflates the ellipsoidal shape of the globe itself.

see enlargement The extent of a hypothetical northern circumpolar ocean over the territory of North America is shown. The orange color indicates areas with elevation higher than 3,000 meters above the level of the northern ocean. Red dots represent some of the biggest cities of the continent.

The bulge defines the final shape of the globe by establishing the uniform sea level in gravitational equilibrium, which is used as the standard reference for describing the shape of the earth. It is the geometry of this very shape that geodesists were trying to calculate for more than a century. Their efforts were finalized by the acceptance of the ellipsoid referred to as World Geodetic System 1984 (WGS84) by the international community in Washington, D.C., in 1984. The ellipsoid WGS84 approximates the shape of the earth more accurately than many other ellipsoids that were previously proposed.

If the earth stood still, the oceans would gradually migrate toward the poles and cause land in the equatorial region to emerge. This would eventually result in a huge equatorial megacontinent and two large polar oceans. The line that delineates the areas that hydrologically contribute to one or the other ocean would follow the equator if the earth was a perfect ellipsoid. However, due to the significant relief of both the continents and the ocean floor, the hypothetical global divide between the areas that hydrologically contribute to one or another ocean deviates from the equator significantly. Analogous to the well-known U.S. Continental Divide, this would be the border separating two giant hemispherical watersheds of the new circumpolar oceans. Interestingly, the highest point on this global divide would not be the highest altitude on the entire globe. The highest elevation of the global divide in the Colombian Andes would be about 12,280 meters, whereas the altitudes of the famous equatorial volcanoes of Chimborazo (Ecuador) and Kilimanjaro (Tanzania) would be 13,615 and 12,786 meters, respectively. Both volcanoes happen not to be located on the global divide line. The lowest point on the new global dividing line, with an elevation of 2,760 meters, would be situated southwest of Kiribati Island in the western Pacific.

Due to the unique relief of the earth's surface at the beginning of the slowdown, the most significant changes to the outline of land versus water would occur at the high latitudes of the northern hemisphere where the swell ocean would quickly expand over the flat and vast territories of northern Siberia and northern Canada. At the same time, changes to the continental outlines at low latitudes would be barely perceptible because (with a few exceptions) equatorial waters are deep, and a decrease in water level by a few dozen meters would not cause large areas of land to emerge. Toward the end of the slowdown period, when the main geographic features of oceans and land would have already adjusted to the ellipsoidal shape of the globe and the new distribution of gravity, relatively small changes would occur. This can be attributed to the ellipsoidal shape of the globe, which overwhelms the effect of the diversity of the earth's geographic relief.

Today, all three world oceans are connected. This creates a global ocean with basically one sea level. As a consequence of rotational slowdown, the outline of the global ocean would continuously undergo dramatic changes. Equatorial waters would move toward polar areas, initially causing a significant reduction in depth while filling the polar basins that have much less capacity. As regions at high latitude in the northern hemisphere become submerged, the areal extent of the northern circumpolar ocean would rapidly expand, covering the vast lowlands of Siberia and northern portions of North America. The global ocean would remain one unit until the rotation of the earth decreased to the speed at which ocean separation would occur. The interaction between the inertia of huge water bodies and decreasing centrifugal force would be very complicated. As the consequence of steady slowdown of earth's rotation, the global ocean would be gradually separated into two oceans. Obviously, the last connection will be broken at the lowest point of the global divide line, located southwest of the Kiribati Islands. Since the current western Pacific Ocean is a plane, land would emerge quickly because there would be no chance that water would be exchanged between the two circumpolar oceans after the initial split. The area of final separation between the two oceans would be the simultaneous emerging and drying of territory extending for hundreds of kilometers.

see enlargement While gravity pulls more water toward the Arctic Ocean, the lowlands of Siberia and northern Canada would become submerged. The corresponding movement of water away from the equatorial region combined with the shallow continental shelf waters southeast of Asia and north of Australia will cause land to emerge.

see enlargement A deepening Arctic Ocean would lead to the further expansion of water over the northern plains of Asia, Europe, and North America. Greenland and Antarctica, despite their high elevations, would become significantly smaller in size. New archipelagos emerge from the southern seas. The Great American Lakes, the biggest freshwater reservoirs in the world, dissolve into the ocean.

The slowdown would continue after the separation of the two oceans and cause further migration of the ocean water toward the poles. Surprisingly (despite Antarctica's elevation), the southern polar basin has a larger capacity than the northern one. Given the fixed volume of water in both hemispheres, the more capacious basin of the southern pole would result in an overall lower sea level than the northern ocean. According to volumetric calculation performed with the ArcGIS 3D Analyst extension, the difference between the sea level of the two oceans should be 1,407 meters. However, the data accuracy does not warrant this level of precision, so the elevation difference between the sea level of the two oceans used was 1,400 meters.
The series of maps illustationg this article depict the intermittent stages during this migration of the earth's oceans and changes in land extents, topographic elevation, and bathymetric depth caused by the decreasing speed of the earth's rotation. These maps demonstrate the intermediate stages of transitional geography from a rotating to a stationary world. They show the effects of the gradual reduction of centrifugal force from its current level to none, leaving gravity as the only force controlling the ocean's extent.
The actual slowdown of the earth's rotation has been observed, measured, calculated, and theoretically explained. As newer methodologies are developed and more precise instruments are constructed, the exact rate of the slowdown may vary between some sources. Reflecting this very gradual slowing, atomic clocks must be adjusted to solar time by adding a leap second every so often. The first leap second was added in 1956.

see enlargement All Antarctica would be under water at this point. The north polar waters and the water over the vast, recently submerged territories in Siberia and Canada would be getting deeper. At the same time, equatorial waters would be getting more shallow.
see enlargement Large land areas near the equator continue growing and join with each other. By now, nearly all of Canada, Europe, and Russia are covered by a northern circumpolar ocean.

Most scientists agree that the solar day (related to the speed of rotation) is continuously getting longer. This minimal increase of the day length is due mainly to the oceanic tidal friction. When the estimated rate of the slowdown was projected back to past geologic eons, it showed that the length of a day was several hours shorter than today.
Consequently, during the Devonian period (400 million years ago), the earth rotated about 40 more times during one revolution around the sun than it does now. Because the continents have drifted significantly since that time, it is difficult to make estimates of the land versus ocean outlines for that era. However, we can be certain that—with a faster spinning speed in the past—the equatorial bulge of oceanic water was much larger then than it is today. Similarly, the ellipsoidal flattening of the earth was also more significant.

see enlargement
This animation depicts the intermittent stages during this migration of the earth's oceans and changes in land extents, topographic elevation, and bathymetric depth caused by the decreasing speed of the earth's rotation. It shows the effects of the gradual reduction of centrifugal force from its current level to none, leaving gravity as the only force controlling the ocean's extent.

The influence of the rate of the earth's rotation has a dominant effect on the geometry of the globe, in terms of the globe's overall shape as well as the outline of the global ocean. The earth's physical relief is only a secondary factor controlling the delineation of oceans. The slowdown of earth's rotation will continue for 4 billion years—as long as we can imagine. The slowdown infinitesimally—but steadily—changes the globe's geometry and makes it dynamic. The net result of these dynamic adjustments is that the earth is slowly becoming more and more like a sphere. However, it will take billions of years before the earth stops spinning, and the gravitational equipotential creates a mean sea level that is a perfect sphere.

About the Author

Witold Fraczek is a longtime employee of Esri who currently works in the Application Prototype Lab. He received his doctorate in the application of GIS in forestry from Agricultural University and master's degrees in hydrology from the University of Warsaw, Poland, and remote sensing from the University of Wisconsin, Madison.

Source :

jeudi 17 mars 2016

Si la Terre s’arrête de tourner que deviendra l’homme?

Si un jour la Terre s’arrêtait de tourner sur elle-même, la première conséquence serait des journées extrêmement longues, proportionnelles au temps de révolution de la Terre autour du Soleil, soit environ 1 an. Il ferait alors de plus en plus chaud sur le côté éclairé, et de plus en plus froid du côté obscur.
 La distribution des océans changerait aussi radicalement car sans la force centrifuge engendrée par la rotation de la Terre, la gravité prendrait le dessus et l’eau sera irrémédiablement attirée vers les points de gravité les plus forts. Cette migration en masse provoquerait une montée des eaux vers ces points, voire des raz de marée.
 Les continents seraient également soumis à cette gravité et leur déplacement entrainerait des tremblements de terre.
 Pour finir, l’attraction du Soleil, contrée uniquement par la rotation de la Terre, finirait par nous faire entrer en collision avec lui.
1 ère cause de ralentissement <>
 C’est l’astronome Edmond Halley qui s’aperçut le premier, au XVII e siècle, que la Terre tournait de moins en moins vite.
 La Terre, comme une toupie, tourne de moins en moins vite sur elle-même. Elle boucle son tour aujourd’hui en 24 h mais il ne lui en fallait que 22 h il y a 400 millions d’années.
 Ce ralentissement aboutira t-il à l’arrêt complet ? Peut on faire un rapprochement avec le point zéro de Gregg Braden? et les trois jours d'obscurité?
 Je vous laisse à vos recherches,en attendant je vous propose de lire ces quelques données scientifiques trés interressantes qui peuvent nous en apprendre beaucoup.

Ralentissement de la rotation
 La grande responsable de ce ralentissement est la Lune. Elle avance moins vite que la Terre. La Lune effectue une rotation sur son axe en 27,3216 jours, ce qui est la durée de sa période orbitale, c'est pourquoi la Lune présente toujours la même face à la Terre.
 Pendant très longtemps, le frottement dû aux forces de marée, à l'intérieur du système Terre-Lune, a ralenti la rotation de la Lune. La rotation terrestre a également ralenti. Des anneaux de croissance, dans le corail fossilisé, indiquent que la période des marées était différente il y a 360 millions d’années, et donc que la période orbitale de la Lune devait également être différente.
 Emporté par son élan, le bourrelet des marées à tendance à devancer la Lune au lieu d’être parfaitement aligné sur sa trajectoire.
 Le satellite tire donc en permanence ces masses d’eau en arrière, freinant la totalité du globe.
 Pour être précis, la Terre ralentit de deux millisecondes par siècle. Donc, tous les 200 millions d’années environ, il lui faut une heure de plus pour boucler un tour complet.
 De son côté, la Lune s’éloigne de notre planète au rythme de 3,7 centimètres par an.

Un arrêt complet ?
 A force de perdre de la vitesse, la Terre finira t-elle par s’arrêter ?
 Au rythme du ralentissement actuel, les marées finiront de dissiper toute l’énergie de rotation de notre planète un jour ou l'autre
Quand la Terre arrêtera ses rotations et que la fréquence atteindra 13 cycles (13 Hz), nous serons au ''Point Zéro ' du champ magnétique. La Terre s'immobilisera puis commencera à tourner dans l'autre sens produisant un renversement dans le champ magnétique autour de la Terre et en elle.

les 4 premières vidéo ci-dessous parlent d'un ralentissement sur plusieurs années.

1_4 la terre cesse de tourner par grandeetoile --------------------------------------------------------------------------
2_4 la terre cesse de tourner par grandeetoile --------------------------------------------------------------------------
3_4 la terre cesse de tourner par grandeetoile --------------------------------------------------------------------------
4_4(1) la terre cesse de tourner par grandeetoile
2 ème cause de ralentissement <>
Le séisme du Chili a ralenti la rotation de la Terre _ magnitude 8.8 _
d'après les très savants calculs d'un chercheur de la Nasa, Richard Gross, assisté d'une batterie d'ordinateurs et de modèles informatiques de pointe, l'axe de rotation de la Terre aurait bougé de 8 centimètres, entraînant un raccourcissement de la durée du jour de… 1,26 microseconde. Soit 1,26 millionième de seconde. Même avec la plus précise des montres, personne ne pourra voir la différence.
Et si le séisme a eu ces conséquences, ce n'est pas parce qu'il a secoué l'axe de rotation de la Terre comme le ferait une pichenette sur une toupie en mouvement, c'est parce qu'il a légèrement changé la répartition verticale interne de la masse terrestre.
Le séisme du Japon a ralenti la rotation de la Terre _ magnitude 9 _
 Selon les experts de l’institut italien de géophysique, le gigantesque séisme qui a frappé le Japon (dont la magnitude a été réévaluée à 9 au lieu de 8,9 sur l’échelle de Richter) a eu un impact non négligeable sur la planète : son axe de rotation s’est carrément déplacé de près de 10 centimètres ! C’est ce qu’a indiqué Antonio Piersanti, directeur de recherche au sein de l’Institut national (italien) de géophysique et de vulcanologie (INGV).
Donc chaque année des tremblements de terre supérieure à une magnitude 8 et plus ralentissent la rotation de la Terre
   Magnitude 8.0 76km W of Lata, Solomon Islands 2013-02-06 01:12:25 UTC
   Magnitude 8.2 94km NW of Iquique, Chile 2014-04-01 23:46:47 UTC
C'est une des conséquences inattendues des gros séismes. Ils libèrent une telle puissance qu'ils modifient la période de rotation de la Terre et donc la durée d'une journée. Rien que ça... Après que la Terre a tremblé au Chili, dans la nuit de vendredi à samedi, les jours terrestres ont raccourci. Selon les premiers calculs de Richard Gross, géophysicien au Jet propulsion Laboratory de la NASA, le jour est désormais plus court de 1,26 microseconde (une microseconde est égale à un millionième de seconde).
Comme nous le savons, notre planète est composée d’un noyau dense, d’une croûte et d’un manteau plus ou moins solides ainsi que d’un magma liquide situé entre le noyau et le manteau.  La vitesse de rotation du noyau diffère de celle de la croûte et du manteau.  Ce phénomène physique de double vitesse génère un mouvement du magma conducteur d’électricité et crée ce que nous appelons le champ magnétique terrestre.
Or, actuellement et depuis quelques milliers d’années, la vitesse de rotation de la Terre est en chute libre, ce qui a pour effet un effondrement du champ magnétique puisque l’intensité de celui-ci est directement proportionnelle à la vitesse de rotation.  Cette intensité a ainsi diminué de 60 % en 2000 ans dont 35 % sur les 30 dernières années.
Le champ terrestre s’est inversé environ 300 fois ces derniers 200 millions d’années1. La dernière inversion est survenue il y a 780 000 ans 
Nous savons qu’une des principales fonctions du champ magnétique terrestre est la protection de la planète des influences venant de l’espace, particulièrement des bombardements des rayons cosmiques et des particules solaires.  Cette diminution de l’intensité de ce champ couplée à l’activité de l’astre solaire constituent les principales causes du réchauffement planétaire actuel.  Celui-ci ne serait pas dû principalement à l’activité humain
3 ème cause de ralentissement <>
C’est en 1915 à la suite de la parution de son livre « La Genèse des continents et des océans »  qu’Alfred Wegener, astronome et climatologue allemand propose sa théorie de la dérive des continents par l’expansion du globe terrestre.
En contradiction avec la théorie de la tectonique des plaques et face aux objections des « antimobilistes », Wegener affina sa réflexion dans ses nouvelles éditions jusqu’en 1929. Son hypothèse à ceci de remarquable qu’elle associe des arguments géologique, paléontologique et climatique. Forcé de constater qu’aujourd’hui les astrophysiciens et géologues ne peuvent plus nier l’exactitude de l’intuition de Wegener. La Terre est bien en expansion. La mesure par satellite de son diamètre démontre une augmentation constante mais d’intensité variable de l’ordre de plusieurs centimètres chaque année ! Une question se pose alors: qui dit augmentation du volume dit besoin d’énergie; mais d’où provient cette énergie et par quel mécanisme notre planète la transforme t’elle en masse ? Un début de réponse apparaît à la lecture des découvertes de Tesla sur « l’ether » et se confirme de nos jours par la mise en évidence du rôle des neutrinos. Il s’agit ici d’une véritable révolution dans notre compréhension des mécanismes géologiques, thermodynamiques et astronomiques. Arte à diffusé un très intéressant reportage à ce sujet en 2010.

4 ème cause du ralentissement <<La fonte des glaciers et de la banquise>>
  La banquise arctique a atteint son quatrième point le plus bas en 2015, la ligne jaune représentant la moyenne de son étendue sur les années 1981-2010... Plus elle fond, plus le niveau des mers monte.  REUTERS/NASA/Goddard Scientific Visualization Studio La banquise arctique a atteint son quatrième point le plus bas en 2015, la ligne jaune représentant la moyenne de son étendue sur les années 1981-2010... Plus elle fond, plus le niveau des mers monte. REUTERS/NASA/Goddard Scientific Visualization Studio
La fonte des glaciers et de la banquise fait monter le niveau des océans, qui a une influence sur la rotation de la Terre. Ou comment le réchauffement climatique va rallonger les journées terrestres. Un petit peu. La fonte des glaciers et de la banquise fait monter le niveau des océans. Le message a été répété un nombre incalculable de fois lors de la COP 21 à Paris, afin de mettre en garde contre les conséquences dramatiques sur les zones côtières et les îles... Mais un autre effet est imputable à la montée des eaux: elle ralentit la rotation de la Terre et rallonge les journées.  
L'impact se chiffre en millisecondes par siècle. Il semble imperceptible, certes. Mais il est suffisant pour fausser certains calculs astronomiques. L'hypothèse, émise en 2002, a été vérifiée et amendée par une équipe de chercheurs qui publie ses résultats dans Science Advances. 
Walter Munk et son énigme
"Si vous faites fondre les calottes glaciaires ou les glaciers, ce qui se produit à proximité des pôles, et que toute cette masse se déplace des pôles vers l'équateur, ce mouvement est comparable à celui d'un surfeur qui utilise un bras pour ralentir sa vitesse", décrit un des auteurs, Jerry Mitrovica, professeur de géophysique à l'University d'Harvard, au Washington Post. Ce déplacement va "ralentir la rotation de la Terre" et, puisqu'il n'est "pas tout à fait symétrique ni également réparti", il peut aussi affecter son axe de rotation. 
L'océanographe Walter Munk avait tenté de calculer cet effet dans un article publié en 2002 dans Proceedings of the National Academy of Sciences, mais n'avait pas réussi à prouver sa théorie. Un décalage s'insinuait entre son évaluation de la montée des eaux au XXe siècle et celle du ralentissement de la rotation de la Terre. Or la clé de cette "énigme de Munk" pourrait avoir été trouvée. Non seulement le scientifique avait surévalué la montée des eaux passée, mais il avait oublié des complices. 

La montée des eaux n'est pas la seule coupable

"L'attraction gravitationnelle de la Lune contribue également" à ce léger freinage, note Mathieu Dumberry, professeur de physique à l'Université d'Alberta et coauteur de l'étude. "Mais la combinaison de ces effets ne suffit encore pas: le rôle du noyau terrestre doit être pris en compte. Or depuis 3000 ans, le coeur de la Terre a légèrement accéléré [vers l'est, NDLR] tandis que le manteau sur lequel nous nous trouvons a légèrement ralenti sa rotation [vers l'ouest, NDLR]." Ces modifications influent sur le champ magnétique de la planète, mais aussi sur la durée de nos journées.  
D'après les calculs présentés dans Science Advances, ces effets cumulés devraient ajouter 1,7 millisecondes à chaque jour terrestre d'ici la fin du XXIe siècle. Une poussière pour l'homme mais une poussière mesurable qui s'ajoute aux multiples études scientifiques sur le changement climatique et ses ramifications, note le Washington Post. "Ces effets semblent minuscules mais ce sont eux qui recèlent les changements les plus importants du système terrestre", estime Jarry Mitrovica.  

Source :

Et si la Terre s’arrêtait de tourner, que se passerait-il ?

Un jour ou l’autre, nous nous sommes tous déjà demandé ce qu’il pourrait bien se passer si instantanément, notre Terre s’arrêtait de tourner… Croyez-moi, personne n’a réellement envie de savoir !

Première réponse, nous serions tous instantanément morts, notre corps se voyant propulsé à plus de 1600 km/h en une fraction de seconde. Mais ceci est plutôt une bonne nouvelle, car nous éviterions de traverser toute une série de catastrophes bien pires.

Voici en quelques points certains faits qui se produiraient si la Terre s’arrêtait de tourner de manière instantanée :
  • Notre corps serait propulsé vers l’Est comme une masse d’os et de muscles à la vitesse de 465 mètres par seconde pour les personnes les plus proches de l’Équateur, et 368 mètres par seconde pour les personnes situées au-dessus du tropique du cancer. Les personnes proches de pôles survivraient… à première vue.
  • Les personnes en avion survivraient les premières secondes, avant de périr dans les gigantesques orages qui feraient rage.
  • La vitesse du vent serait plus élevée que celle d’une bombe atomique, et provoquerait des incendies instantanément tout autour du monde.
  • Le vent provoquerait également une érosion hallucinante sur tout ce qui fait partie de la croûte terrestre.
  • Les eaux s’élèveraient en de gigantesques tsunamis, et toute la carte du monde deviendrait obsolète, comme montré sur cette image.
  • Le noyau terrestre au centre de la Terre perdrait toutes ses fonctions, et le champ magnétique terrestre s’arrêterait instantanément, laissant au Soleil le soin de tout détruire.
  • En plus de cela, la moitié de la Terre serait constamment exposée au Soleil, provoquant des hausses extrêmes de températures. L’autre moitié de la planète serait complètement gelée.

Source: Citizen Post via les chroniques de Rorschach

mardi 15 mars 2016

Manchu, j'en suis Fu !

Manchu alias Philippe Bouchet est mon dessinateur de science-fiction préféré depuis l'époque où je jouais au jeu de rôles Empire Galactique et encore avant quand je regardais, sans connaître le nom du dessinateur, les chroniques d'Ulysse 31.

Il présente ici une illustration pour la série Omale  de Laurent Genefort.

"You have a strong heart. No fear...but stupid. Ignorant, like a child." – Neytiri

Neytiri te Tskaha Mo'at’ite is the Na'vi princess of the Omaticaya clan. She is the second-born daughter of Eytukan and Mo'at and younger sister of Sylwanin. She meets Jake Sully in a Pandoran forest, helping him when he is attacked by a pack of viperwolves. Neytiri soon becomes Jake's teacher and helps him to complete several tasks. Eventually, they fall in love and mate under the Trees of Voices. Neytiri fights alongside Jake in the Assault on the Tree of Souls and saves him from being killed by Miles Quaritch. She will be the future Tsahìk of the clan, with her mate, Jake, as Olo'eyktan.


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