Pulsar The precise periods of pulsars makes them useful tools. Observations of a pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation. The first extrasolar planets were discovered around a pulsar, PSR B1257+12. Certain types of pulsars rival atomic clocks in their accuracy in keeping time. History of observation[edit] Discovery[edit] The first pulsar was observed on November 28, 1967, by Jocelyn Bell Burnell and Antony Hewish.[1][2][3] They observed pulses separated by 1.33 seconds that originated from the same location on the sky, and kept to sidereal time. The word "pulsar" is a contraction of "pulsating star",[7] and first appeared in print in 1968: An entirely novel kind of star came to light on Aug. 6 last year and was referred to, by astronomers, as LGM (Little Green Men). Milestones[edit] In 1974, Joseph Hooton Taylor, Jr. and Russell Hulse discovered for the first time a pulsar in a binary system, PSR B1913+16. Nomenclature[edit]
10 Best Writing Prompts for High School English Students By the time students walk in the door of our secondary ELA classrooms, they’re not exactly new to writing assignments. They’ve done autobiographies. Short stories. 1. There are a lot of amazing TED Talks out there that students love. 2. If you’re looking for some unusual, short and sweet writing options, check out John Spencer’s Creative Writing Prompts for Students playlist. 3. What teenager doesn’t harbor some (not so) secret crush? 4. We’ve all sat in the audience of a graduation and wondered what we would talk about if we were on stage speaking. 5. Students always perk up for an authentic audience and a connection to the real world. 6. When you try the fold and pass, you’re guaranteed to end up with some very surprising stories. This writing assignment is not for the faint of heart! 8. If you’ve never heard NPR’s old radio series “This I Believe,” it’s a great listen. 9. 10. Seriously. What are your favorite writing prompts for high school?
Quasar Artist's rendering of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun.[1] Credit: ESO/M. Kornmesser Quasars (/ˈkweɪzɑr/) or quasi-stellar radio sources are the most energetic and distant members of a class of objects called active galactic nuclei (AGN). Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that appeared to be similar to stars, rather than extended sources similar to galaxies. While the nature of these objects was controversial until the early 1980s, there is now a scientific consensus that a quasar is a compact region in the center of a massive galaxy, that surrounds its central supermassive black hole.[2] Its size is 10–10,000 times the Schwarzschild radius of the black hole. Overview[edit] A Hubble picture showing a quasar core Properties[edit] Gravitationally lensed quasar HE 1104-1805.[13]
Bac fiche français : le théâtre classique – Bac 2018 – Toutpourlebac.com Les trois unités – Vraisemblance et bienséance – Critiques Au XVIIe siècle, les doctes entreprennent de «codifier» le théâtre et tout particulièrement la tragédie. C’est principalement après la «querelle» du Cid (1636), qui opposa partisans d’un théâtre réglementé et tenants d’une création de liberté, que s’est constitué un ensemble de règles inspirées, pour la plupart, de La Poétique d’Aristote (IVe siècle av. J. Le développement de la pièce classique doit obéir au principe d’unité défini par Boileau (Art poétique, 1674) : «Qu’en un lieu, en un jour, un seul fait accompli tienne jusqu’à la fin le théâtre rempli». L’UNITE D’ACTION Elle vise à supprimer les intrigues secondaires et à concentrer l’intérêt dramatique autour d’une action unique. L’UNITE DE TEMPS Elle resserre les faits et les limite à vingt-quatre heures. L’UNITE DE LIEU Elle résulte des deux premières. LA VRAISEMBLANCE Elle veut que s’impose l’impression de vérité.
Redshift Absorption lines in the optical spectrum of a supercluster of distant galaxies (right), as compared to absorption lines in the optical spectrum of the Sun (left). Arrows indicate redshift. Wavelength increases up towards the red and beyond (frequency decreases). In physics, redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum. Although knowledge of redshifts and blueshifts has been applied to develop several terrestrial technologies (such as Doppler radar and radar guns),[1] redshifts are most famously seen in the spectroscopic observations of astronomical objects.[2] A special relativistic redshift formula (and its classical approximation) can be used to calculate the redshift of a nearby object when spacetime is flat. Redshift and blueshift History[edit] The earliest occurrence of the term "red-shift" in print (in this hyphenated form), appears to be by American astronomer Walter S. (since where
Me shooting a bow Archery A Rikbaktsa archer competes at Brazil's Indigenous Games Master Heon Kim demonstrating Gungdo, traditional Korean archery (Kuk Kung), 2009 Archer in East Timor History[edit] The bow seems to have been invented in the later Paleolithic or early Mesolithic periods. The oldest indication for its use in Europe comes from the Stellmoor (de) in the Ahrensburg valley (de) north of Hamburg, Germany and dates from the late Paleolithic, about 10,000–9000 BCE. Bows and arrows have been present in Egyptian culture since its predynastic origins. Classical civilizations, notably the Assyrians, Persians, Parthians, Indians, Koreans, Chinese, Japanese and Turks fielded large numbers of archers in their armies. Archery was highly developed in Asia. Mounted archery[edit] Central Asian tribesmen (after the domestication of the horse) and American Plains Indians (after gaining access to horses)[6] became extremely adept at archery on horseback. Decline of archery[edit] Eighteenth-century revival[edit]