CHAPTER 1 What Is an Encyclopedia n encyclopedia is a resource that contains infor mation on many different subjects or that provides in depth informa tion on one particu lar subject Most are reliable sources of information because An encyclopedia is a good place to start when you are trying to learn about a their content is new
WHAT IS AN ENCYCLOPEDIA reviewed and checked by professionals for its accuracy It doesn't matter if you are doing a project or report for school or if you are just seeking more information about a sports figure animal place in the world or event that happened in history Encyclopedias provide a wealth of information in the form of articles photographs illustrations maps tables and many other elements You can explore the world around you without leaving your home or school by using an encyclopedia PRINT AND ONLINE ENCYCLOPEDIAS Encyclopedias are available in two formats print and online Before computers an encyclopedia
How Do I USE AN ENCYCLOPEDIA Britannica GED a hand in my mournace A Danies may sent an images Encyclopaedia Britannica USING AN ENCYCLOPEDIA TO RESEARCH THE MOON What if you want to learn about the moon Here is what an encyclopedia might say about it The moon is a large natural object that orbits or travels around Earth After the sun it is the brightest object in the sky The average distance between the moon and Earth 238 600 miles is about 384 000 kilometers First edition of the Encyclopedia Britannica Credit Enaclopedia Britannion line uns a smayelopedia patience were Energiased Banner English language element was Ennipedia Brannies print annopaedia MLA Feb APA allie Smartpedia attention photography rieved them to turn banniesman Harvard style was a printed collection of articles Evercore organized in alphabetical order by accommon topic The articles could be contained in a single volume or in many vol Encyclopedias are avail umes An online encyclopedia has the able in both print and online versions same information as a print version but it has many additional
WHAT IS AN ENCYCLOPEDIA OME BROWSE ADVOCACY HELP WORKSPACE K Britannica Hubble Space Telescope HST Advanced Search A Table of Contents EDIT SAVE PRINT E MAIL Video images a VIDEOS Hubble Space Telescope HST ARTICL from the Encyclopedia Britannica Ebooks More old Get involved Share a LOOSI Web links Hubble Space Telescope HST the most sophisticated optical observatory over placed into orbit around Earth Earth's atmosphere obscures ground based astronomers view of celestial objects by absorbing or distorting tight rays from them A telesco stationed in outer space is entirely above the atmosphere however and receives images of much greater brightness clarity and oil than do ground based telescopes with comparable optics IMAGES After the U S Congress had authorized its construction in 1977 the Hubble Space Telescope was built under the supervision of the National Aeronautics and Space Administration NASA of the United States and was named after Edwin Hubble the foremost Am astronomer of the 20th century The HST was placed into orbit about 600 km 370 miles above Earth by the crew of the space shut Discovery on April 25 1990 The HST is a large reflecting telescope whose mirror optics gather light from celestial objects and direct into two cameras and led spectrographs The HST has a 24 metre 94 inch primary mirror a smaller secondary mirror and various recording instruments that detect visible ultraviolet and infrared light The most important of these instruments the wide field planetary camera can take eine field or high resolution images of the planets and of galactic and extragalactic objects This camera is designed to achieve image resolutions 10 times greater than that of even the largest Earth based telescope A faint object camera can detect an object 50 times than anything observable by any ground based Telescope a faint object spectrograph gathers data on the objects chemical compon high resolution spectrograph receives distant objects wiltraviolet light that cannot reach Earth because of atmospheric absorption About one month after launch it became apparent that the HSTs large primary mirror had been ground to the wrong shape owing to testing procedures by the minors manufacturer The resulting optical defect spherical aberration caused the mirror to produce fuzz than sharp images The HST also developed problems with its gyroscopes and with its solar power arrays On December 2 13 19 mission of the NASA space shuttle Endeavour sought to correct the telescope's optical system and other problems in five space will shuttle astronauts replaced the HSTs wide field planetary camera and installed a new device containing 10 tiny mirrors to correct the paths from the primary mirror to the other three scientific instruments The mission proved an unqualified success and the HST soon operating at is full potential returning spectacular photographs of various cosmic phenomena Three subsequent space shuttle missions in 1997 1999 and 2002 repaired the HST aroscopes and added new instruments n Online encyclopedias are easy to use and sometimes give you more information than print
