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 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
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 io9. We come from the future. Hubble's Panoramic View Several million stars are vying for attention in this NASA/ESA Hubble Space Telescope image of a raucous stellar breeding ground in 30 Doradus, located in the heart of the Tarantula nebula. 30 Doradus is the brightest star-forming region in our galactic neighbourhood and home to the most massive stars ever seen. The nebula resides 170 000 light-years away in the Large Magellanic Cloud, a small, satellite galaxy of our Milky Way. No known star-forming region in our galaxy is as large or as prolific as 30 Doradus. The image comprises one of the largest mosaics ever assembled from Hubble photos and consists of observations taken by Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, combined with observations from the European Southern Observatory’s MPG/ESO 2.2-metre telescope that trace the location of glowing hydrogen and oxygen. The image is being released to celebrate Hubble’s 22nd anniversary. The colours come from the glowing hot gas that dominates regions of the image. Notes
64 Things Every Geek Should Know « Caintech.co.uk If you consider yourself a geek, or aspire to the honor of geekhood, here’s an essential checklist of must-have geek skills. The term ‘geek’, once used to label a circus freak, has morphed in meaning over the years. What was once an unusual profession transferred into a word indicating social awkwardness. As time has gone on, the word has yet again morphed to indicate a new type of individual: someone who is obsessive over one (or more) particular subjects, whether it be science, photography, electronics, computers, media, or any other field. A geek is one who isn’t satisfied knowing only the surface facts, but instead has a visceral desire to learn everything possible about a particular subject. A techie geek is usually one who knows a little about everything, and is thus the person family and friends turn to whenever they have a question. 2. If you rolled your eyes here, that is a good thing. 1. 3. 4. 5. 6. 7. 8. 9.