Santé | Jeunes et minces? Les maths contre la retouche photo Des chercheurs du Dartmouth College ont mis au point un algorithme capable de déterminer quand une photo a été retouchée hors de proportion par des outils comme Photoshop, un procédé abondamment utilisé dans les photos de mode et dans les magazines de célébrités et dénoncé par les spécialistes en santé publique. Le logiciel mis au point par Hani Farid, décrit dans une publication dans les Proceedings of the National Academy of Sciences, permettrait de quantifier la retouche effectuée sur une photo, et donc de déterminer objectivement à partir de quand on exagère. Cet outil pourrait permettre de lutter plus facilement contre ces images dont on sait qu’elles nuisent à la bonne santé et à l’estime de soi de ceux et celles qui les regardent. Sur son site, le chercheur donne en exemple quelques images avant/après analysées par son logiciel. Cliquez sur «Toggle» pour voir la transformation. Hallucinant! (mesdames, si vous craquez pour le beau George Clooney, vous risquez d’avoir tout un choc.
Atoms in the Universe A billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions. Credit: NASA/ESA/A. Felid (STScI)). It’s no secret that the universe is an extremely vast place. That which we can observe (aka. But interestingly enough, it is when you look at that matter on the smallest of scales that the numbers become the most mind-boggling. At this level, it is estimated that the there are between 1078 to 1082 atoms in the known, observable universe. And yet, those numbers don’t accurately reflect how much matter the universe may truly house. The history of the universe starting the with the Big Bang. While a German supercomputer recently ran a simulation and estimated that around 500 billion galaxies exist within range of observation, a more conservative estimate places the number at around 300 billion. On average, each star can weigh about 1035 grams. However, Einstein’s equivalence of mass and energy presents a slight complication to this theory.
Ulam spiral Ulam spiral of size 200×200. Black dots represent prime numbers. Diagonal, vertical, and horizontal lines with a high density of prime numbers are clearly visible. The Ulam spiral, or prime spiral (in other languages also called the Ulam Cloth) is a simple method of visualizing the prime numbers that reveals the apparent tendency of certain quadratic polynomials to generate unusually large numbers of primes. In an addendum to the Scientific American column, Gardner mentions work of the herpetologist Laurence M. Construction[edit] Ulam constructed the spiral by writing down a regular rectangular grid of numbers, starting with 1 at the center, and spiraling out: He then circled all of the prime numbers and he got the following picture: To his surprise, the circled numbers tended to line up along diagonal lines. All prime numbers, except for the number 2, are odd numbers. Hardy and Littlewood's Conjecture F[edit] where A depends on a, b, and c but not on n. is an odd prime not dividing a.
Einstein's Big Idea | Time Traveler One of Albert Einstein's greatest insights was realizing that time is relative. It speeds up or slows down depending on how fast one thing is moving relative to something else. How much does it change? Requires the Shockwave plugin Instructions Click on Captain Ein or Major Stein to set their starting ages.Click on the spaceship to set its speed.Click one of the twinkling stars to choose a destination and start the journey.When the spaceship lands, compare Captain Ein's and Major Stein's ages. Suggested experiments What happens if: you change the speed of the spaceship? Also, can you find ways to set the ages, speed, and destination so that Captain Ein and Major Stein are almost the same age when Captain Ein returns from her journey? Why does time change? Ever feel like time moves very quickly and sometimes very slowly? Albert Einstein didn't think so. Imagine you're standing on Earth holding a clock. The twin paradox The trip to the star and back takes 50 years. Not at all. Why?
High School Mathematics Extensions/Discrete Probability Introduction[edit] Probability theory is one of the most widely applicable mathematical theories. It deals with uncertainty and teaches you how to manage it. It is simply one of the most useful theories you will ever learn. Please do not misunderstand: We are not learning to predict things; rather, we learn to utilise predicted chances and make them useful. As suggested above, a probability is a percentage, and it's between 0% and 100% (inclusive). Application[edit] You might ask why we are even studying probability. Consider the following gambling game: Toss a coin; if it's heads, I give you $1; if it's tails, you give me $2. Another real-life example: I observed one day that there are dark clouds outside. In real life, probability theory is heavily used in risk analysis by economists, businesses, insurance companies, governments, etc. Why discrete probability? There are two kinds of probability: discrete and continuous. Event and Probability[edit] P(it will rain tomorrow) = 0.6 1. 2. 3. or
How Albert Einstein's Brain Worked" In his last years of life, Albert Einstein knew he was ill and refused operations that would save his life. He made his wishes clear: "I want to be cremated so people won't come to worship at my bones" [source: Paterniti]. Einstein died on April 18, 1955, at the age of 76 of a ruptured abdominal aortic aneurism, and he got his wish as far as his bones were concerned; his ashes were scattered in an undisclosed location. But Einstein's brain was a different matter. During the autopsy, conducted at Princeton Hospital, a pathologist named Thomas Harvey removed Einstein's brain -- the brain that had given the world such revolutionary thoughts as E=mc², the theory of relativity, an understanding of the speed of light and the idea that led to the completion of the atomic bomb. Harvey held the brain that produced those thoughts in his hands. Depending on whom you believe, Harvey either did a wonderful thing for science that day, or he's no better than a common grave robber.
De l’inexactitude dans nos ordinateurs S’il y a bien un endroit où l’on peut être certain des informations que l’on traite, c’est dans les puces de nos ordinateurs. Mais ceci pourrait bien changer grâce aux travaux conjugués de plusieurs instituts... Les Université Rice, de Californie, de Berkeley, de Nanyang à Singapour et le Centre d’Electronique et Microtechnologie de Suisse travaillent sur le projet d’une puce informatique tolérant l’erreur depuis 2003. Les chercheurs se sont en effet aperçus que les traitements et le matériel nécessaires pour annihiler le taux d’erreur demandaient beaucoup d’énergie et faisaient baisser les performances. L’équipe a donc débarrassé son prototype de tout ce qui assurait un taux d’erreur proche de zéro. Le résultat est double : la puce est fonctionnelle mais elle est aussi plus petite. Attention cela dit, il ne s’agit pas ici d’annuler toutes vérifications, ces “puces inexactes” doivent garantir un taux d’erreur acceptable selon son utilisation. [theverge]
Welcome | Virgin Galactic Cryptographie Un article de Wikipédia, l'encyclopédie libre. La machine de Lorenz utilisée par les Allemands durant la Seconde Guerre mondiale pour chiffrer les communications militaires de haut niveau entre le quartier-général du Führer et les quartiers-généraux des groupes d'armées Elle est utilisée depuis l'Antiquité, mais certaines de ses méthodes les plus importantes, comme la cryptographie asymétrique, datent de la fin du XXe siècle. Étymologie et vocabulaire[modifier | modifier le code] Le mot cryptographie vient des mots en grec ancien kruptos (« caché ») et graphein (« écrire »). À cause de l'utilisation d'anglicismes puis de la création des chaînes de télévision dites « cryptées », une grande confusion règne concernant les différents termes de la cryptographie : Histoire[modifier | modifier le code] Utilisé depuis l'antiquité, l'une des utilisations les plus célèbres pour cette époque est le chiffre de César, nommé en référence à Jules César qui l'utilisait pour ses communications secrètes.