La relativité - 1,2,3,4, dimensions La théorie de la Relativité Concepts fondamentaux Corpus théorique (I) Avant de poursuivre cette initiation à la relativité, il est indispensable d'introduire quelques rudiments de mathématiques afin de fourbir votre esprit avec la meilleure arme intellectuelle qui soit pour comprendre la suite du récit. Il faut en effet à présent définir quelques notions fondamentales, quitte à devoir faire usage d’un peu de symbolique mathématique. J’ai tout imaginé pour vous éviter cette partie “dure” du sujet , en tous cas sa partie nettement moins littéraire, c’est-à-dire les définitions du cadre relativiste; mais à mesure que je relisais ce passage tout en le rédigeant, je me suis finalement rendu compte que s’il y avait une chose sur laquelle il fallait bien insister quand on apprend une nouvelle matière, c’était par définition les notions de bases. 1,2, 3, 4 dimensions Nous savons que l’Univers est une construction multidimensionnelle. A lire : Flatland, E.Abbott, 1884 (PDF) Vecteur, champ et tenseur
Mind Hacks News, Videos, Reviews and Gossip - Lifehacker We may control a lot of what our body does, but sometimes it rebels—whether its with brain freeze, a gag reflex, or just plain bad vision. Here are our top 10 body hacks that give the power back to you. P 10. Easily Swallow Stubborn PillsP If you aren't very good at swallowing pills, you can try this trick to get them down: tilt your head forward instead of backward once its in your mouth. 9. SExpand Being able to dilate your pupils at will can help you see the world differently, and there are a number of ways you can go about it—from tensing your stomach in different ways to just focusing on objects that are far away. 8. We all know that tingling feeling you get when your hand or foot goes to sleep, and how annoying it is. 7. When your body feels like its going to overheat from the scorching summer sun, you can lower your body temperature quickly using one of your body's quick cooling spots, like your wrist or the back of your knee. 6. 5. 4. 3. 2. 1.
The Flying Trilobite Exploring Earth’s History with Wolfram|Alpha—Wolfram|Alpha Blog We humans often notice the passage of time by observing our watches; the movement of the Sun, Moon, and stars across the sky; or by the records left by our ancestors in diaries or other historical records—but these are just fleeting moments in the eyes of geological time. We are used to thinking about recorded history. But recorded history is just a blink when compared to the length of time called pre-history. Recorded history only goes back a few thousand years. It’s hard for humans to grasp just how long the Earth has been here. We often take our surroundings for granted. By studying the oldest rocks on Earth and even those found on the Moon during the Apollo Moon missions, scientists have found that the Earth has been around for about 4.5 billion years. The Proterozoic Eon lasted 1.9 billion years (another 41% of Earth’s history), and the events include the deposition of banded iron formations in the rocks.
Flavorwire You can finally stop chugging the dreamwine — HBO’s Game of Thrones is officially back for its second season, and you’ll want to be as clearheaded as possible for what’s about to go down in the Seven Kingdoms. But before we get into that, how about a quick refresher on where things currently stand? Warning: Possible spoilers ahead! The long summer is finally drawing to a close. Meanwhile, her brother Robb Stark, now known as the King in the North, is camping out in the Riverlands with a party that also includes Catelyn Stark, Greatjon Umber, Theon Greyjoy, and Jaime Lannister, who admitted that he pushed Bran out of the window, but won’t explain why. Across the Narrow Sea, the last we saw of Daenerys Targaryen she was putting catatonic Drogo out of his magic-induced misery, smothering her sun and stars with a pillow, and then later, rising from the ashes of his funeral pyre, with three freshly-hatched baby dragons in tow. So! Jaime Lannister: Three words: Grey Wind’s breath.
Nothingness: Why nothing matters Our pursuit of naught provides profound insights into the nature of reality Read more: "The nature of nothingness" SHAKESPEARE had it right, even in ways he couldn't have imagined. For centuries, scientists have indeed been making much ado about nothing - and with good reason. Nothing, or rather what we've long taken to be nothing, may be the key to understanding everything from why particles have mass to the expansion of the universe. As explored in this special issue of New Scientist (see "The nature of nothingness"), nothing is a rich and subtle subject whose biography is far from finished. The modern story of nothing began with a thought experiment dreamed up by Isaac Newton. With that answer, Newton made something out of nothing. The discovery of quantum mechanics took the story of nothing further still. This year's Nobel prize in physics recognises the power of nothing on cosmic scales. Profile New Scientist Not just a website! More From New Scientist More from the web (YouTube)
Attention and Intelligence : The Frontal Cortex In both humans and mice, the efficacy of working memory capacity and its related process, selective attention, are each strongly predictive of individuals’ aggregate performance in cognitive test batteries. Because working memory is taxed during most cognitive tasks, the efficacy of working memory may have a causal influence on individuals’ performance on tests of “intelligence”. Despite the attention this has received, supporting evidence has been largely correlational in nature. Here, genetically heterogeneous mice were assessed on a battery of five learning tasks. Obviously, every discussion of general intelligence in the context of mouse performance is bracketed by lots of question marks. This rodent experiment, however, argues that intelligence is really about the ability to control the spotlight of attention. This reminds me of the ideas I wrote about in the New Yorker last year, while discussing the work of Walter Mischel and the marshmallow task.
Timeline: The evolution of life - life - 14 July 2009 Read full article Continue reading page |1|2|3|4 There are all sorts of ways to reconstruct the history of life on Earth. Pinning down when specific events occurred is often tricky, though. For this, biologists depend mainly on dating the rocks in which fossils are found, and by looking at the "molecular clocks" in the DNA of living organisms. There are problems with each of these methods. Modern genetics allows scientists to measure how different species are from each other at a molecular level, and thus to estimate how much time has passed since a single lineage split into different species. These difficulties mean that the dates in the timeline should be taken as approximate. 3.8 billion years ago? This is our current "best guess" for the beginning of life on Earth. , and was probably based on RNA rather than DNA. At some point far back in time, a common ancestor gave rise to two main groups of life: bacteria and archaea. 3.5 billion years ago 3.46 billion years ago 3.4 billion years ago
permebility kottke.org - home of fine hypertext products The Worlds of David Darling Here's How People Look at Your Facebook Profile -- Literally When potential dates, employers and friends glance at your online social profiles, what do they see? EyeTrackShop, a startup that runs eye-tracking studies for advertisers, helped Mashable find out by applying its technology to the profile pages of popular social networks. The study used the webcams of 30 participants to record their eye movements as they were shown profile pages from Facebook, Google+, LinkedIn, Flickr, YouTube, Klout, Reddit, Digg, Tumblr, Twitter, StumbleUpon and Pinterest at 10-second intervals. What participants looked at on each page and in what order is recorded in the images below. It's not a perfect study. Profile pictures matter. Take a gander at the results of the study in the gallery below, and let us know your own observations in the comments.
cogito – YKY Climate Data Online (CDO) - The National Climatic Data Center's (NCDC) Climate Data Online (CDO) provides free access to NCDC's archive of historical weather and climate data in addition to station history information. | National Climatic Data Center (NCD Climate.gov The NOAA Climate.gov web portal provides science and services for a climate-smart nation Drought.gov The NOAA Drought.gov web portal provides an integrated drought monitoring and forecasting system at federal, state, and local levels Climate Models The NOAA National Operational Model Archive and Distribution System (NOMADS) is a project providing both real-time and retrospective format independent access to climate and weather model data Satellite The NOAA Comprehensive Large Array-data Stewardship System (CLASS) is an electronic library of NOAA environmental data Climate Data Records The NOAA Climate Data Record Program provides a robust, sustainable, and scientifically defensible approach to producing and preserving climate records from satellite data