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
Planets Large and Small Populate Our Galaxy (Infographic) | NASA's Kepler Planet-Hunting Spacecraft | Search for Earth-like Alien Planets Buy This Infographic as a Full-Size Poster Astronomers have discovered more than 700 alien planets beyond the solar system, and the count is rising all the time. Some are large and hot, and others are smaller and cooler, but scientists are still on the lookout for an Earth twin. They just got closer, with the announcement Dec. 5 of a planet found by NASA's Kepler space telescope to lie in the habitable zone around its star where liquid water, and perhaps life, could exist. You can purchase a 20"x60" poster of this SPACE.com infographic on high-quality 14G Photo Paper from the SPACE.com store here: Buy Poster Embed: Paste the code below into your site. <a href=" alt="Astronomers searching for another Earth are getting closer, thanks to recent discoveries by the Kepler space telescope. " src="
Amy Brown Science: Science Chat: A First Day of School Science Lab Icebreaker... What will you do to make the first day of school a great day? What is the most important day of school? The first day! The first day of school is the most important day of the entire school year!! It is the day when students form their first impression of your class. It is the day when students look at you and decide on the spot if they are going to like your class or hate your class. It is the day when students have heightened social anxieties and need to know that they have a friend in your class. You, the teacher, have one day to get it right. Will you be the teacher that goes over a long list of class rules and reads aloud from the class syllabus? Science Chat is perfect for the first day of school. So what exactly is Science Chat? Each lab station should take about 10 minutes to complete. A different concept is covered at each station. Station 1: The Microscope Station 2: Graphing Station 3: Electron Microscopy Station 4: Making Observations, Comparing and Contrasting • Microscope • Coin
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)
Trikomonoosi - Evira Trikomonoosi on lintujen tauti, jonka aiheuttaa yksisoluinen Trichomonas gallinae -loinen. Se on alkueläin, joka elää lintujen suussa ja kuvussa. Loista esiintyy yleisenä kyyhkyillä, mutta sitä on tavattu myös mm. varpuslinnuilla, kanalinnuilla, kurjilla, sorsalinnuilla ja papukaijoilla. Leviäminen T. gallinae leviää linnusta toiseen infektoituneiden lintujen suusta tulevien eritteiden mukana. Oireet Trikomonoosi ilmenee suun ja kuvun tulehduksena, joka estää normaalin nielemisen. Taudin määritys Taudin määritys tehdään yleensä kuolleesta linnusta otetusta näytteestä. Ennalta ehkäisy Ihmisen toimilla voidaan trikomonoosin esiintymiseen vaikuttaa lähinnä lintujen ruokintapaikoilla. Esiintyminen Suomessa ja muualla Trikomonoosi on jo kauan tunnettu kyyhkyjen tautina, ja Suomessakin sitä on todettu kesykyyhkyissä eli puluissa.
The Worlds of David Darling Genomiikka muuttaa eliökunnan luokittelua – Natura Eliökunnan luokittelu on aina ottanut uusia harppauksia tutkimusmenetelmien kehittymisen myötä. Ensimmäisiin tieteellisiin luokitteluihin päädyttiin rakenteellisten tuntomerkkien avulla. Eliöiden rakenteita verrattiin ja samankaltaisimpien eliöiden oletettiin olevan läheisintä sukua toisilleen. Aluksi tutkimusvälineinä oli suurennuslaseja ja valomikroskooppeja, myöhemmin sukulaisuussuhteita pystyttiin tarkentamaan elektronimikroskopian avulla. Tumattomia eliöitä on luokiteltu ulkonäön lisäksi biokemiallisten ominaisuuksien, kasvuolosuhteiden ja taudinaiheutuskyvyn perusteella, sillä niissä on hyvin vähän mikroskoopillakaan nähtäviä ulkonäkötuntomerkkejä. Keskeinen edistysaskel eliökunnan rakenteen ymmärtämisessä saatiin, kun luokittelussa otettiin käyttöön DNA-tuntomerkit. Parhaillaan eliökunnan luokittelu on muutoksen alla, sillä uusia eliöitä ja kokonaisia eliöryhmiä löydetään ja voidaan tutkia DNA-aineiston pohjalta. Erillistä tumattomien ryhmää ei ole Virusten määrittely vaikeaa
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
10 Strange Things About The Universe Space The universe can be a very strange place. While groundbreaking ideas such as quantum theory, relativity and even the Earth going around the Sun might be commonly accepted now, science still continues to show that the universe contains things you might find it difficult to believe, and even more difficult to get your head around. Theoretically, the lowest temperature that can be achieved is absolute zero, exactly ? One of the properties of a negative-energy vacuum is that light actually travels faster in it than it does in a normal vacuum, something that may one day allow people to travel faster than the speed of light in a kind of negative-energy vacuum bubble. One prediction of Einstein’s theory of general relativity is that when a large object moves, it drags the space-time around it, causing nearby objects to be pulled along as well. Relativity of Simultaneity Since this extra dimension is so small, only tiny objects, such as particles, can move along it. Antimatter Retrocausality
Your Sky by John Walker Welcome to Your Sky, the interactive planetarium of the Web. You can produce maps in the forms described below for any time and date, viewpoint, and observing location. If you enter the orbital elements of an asteroid or comet, Your Sky will compute its current position and plot it on the map. Your Sky provides three ways to view the sky with links, where appropriate, among the various presentations. Sky Map The sky map shows the entire sky as viewed from a given location at a specified time and date. To make a sky map, enter the latitude and longitude of your observing site in the boxes below (be sure to check the correct “North/South” and “East/West” settings) and press the “Make Sky Map” button below the form. Horizon Views Horizon Views, showing the stars above the horizon as seen from a specified observing site at a given date and time. The Virtual Telescope Your Sky's Virtual Telescope is your Humble Soft Telescope of the Web. Your Sky help Related Software On the Web:
Voyager - The Interstellar Mission Pioneers 10 and 11, which preceded Voyager, both carried small metal plaques identifying their time and place of origin for the benefit of any other spacefarers that might find them in the distant future. With this example before them, NASA placed a more ambitious message aboard Voyager 1 and 2-a kind of time capsule, intended to communicate a story of our world to extraterrestrials. The Voyager message is carried by a phonograph record-a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth. The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University, et. al. Dr. Sagan and his associates assembled 115 images and a variety of natural sounds, such as those made by surf, wind and thunder, birds, whales, and other animals.
How Quantum Suicide Works A man sits down before a gun, which is pointed at his head. This is no ordinary gun; it's rigged to a machine that measures the spin of a quantum particle. Each time the trigger is pulled, the spin of the quantum particle -- or quark -- is measured. Depending on the measurement, the gun will either fire, or it won't. If the quantum particle is measured as spinning in a clockwise motion, the gun will fire. If the quark is spinning counterclockwise, the gun won't go off. Nervously, the man takes a breath and pulls the trigger. Go back in time to the beginning of the experiment. But, wait. This thought experiment is called quantum suicide.
SIMBAD Astronomical Database What is SIMBAD, and what is it not ? % The purpose of Simbad is to provide information on astronomical objects of interest which have been studied in scientific articles. Simbad is a dynamic database, updated every working day. It provides the bibliography, as well as available basic information such as the nature of the object, its coordinates, magnitudes, proper motions and parallax, velocity/redshift, size, spectral or morphological type, and the multitude of names (identifiers) given in the literature. The CDS team also performs cross-identifications based on the compatibility of several parameters, in the limit of a reasonably good astrometry. Simbad is a meta-compilation built from what is published in the literature, and from our expertise on cross-identifications. Simbad is not a catalogue, and should not be used as a catalogue.
leaves something to be desired