Newspapers / The Waynesville Mountaineer (Waynesville, … / April 21, 1938, edition 1 / Page 6
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I Page 6 THE WAYNES VILLE MOUNTAINEER THURSDAY. APRIL 21 Three Kinds Of Time In Use; "Clock-Time" Not Accurate Time Is An Important Factor In Navigation- Three Types Used IL M. Hall A thorough understanding of the subject of time is absolutely nec essary to the navigator, for time en ters into almost every ' problem of position in the air. There are three kinds of time in general use, True Solar Time, also called Apparent Solar Time, Mean Solar Time, and Sidereal Time. Apparent Time Is that shown by the sun. Oar clocks keep Mean or Civil Time. The earth revolves on its axis once in 24 hours, and in theory the sun crosses the me ridian of any given place at exactly 12 o'clock by clock time each day. but this theory is not correct, because the earth does not revolve at a uniform rate of speed in relation to the sun As a result during a part of the year Solar Time is fast of clock time, and part of the time it is slow. As it was impossible to construct a clock to re cord the complicated variations in the earth's movement in relation to the sun it was necessary to devise a sys tem that would be uniform through out the years to which a clock could be regulated. So the astronomers cal culated the average of all the varia tions during the year, and called it Mean Solar, or Civil Time. This is the time kept by our watches, clocks and chronometers. It is the time sent out from the Naval Observatory at Arlington, computed from Sidereal Time. Mean Solar Time can not be de termined by observation of the sun, for the time thus obtained is the True or Apparent Solar Time, the time of the passage of the True Sun across the meridian of the observer at 12 o'clock, noon. In order to reduce this Apparent Time to Civil Time the Nautical Almanac publishes for each day and fractions thereof certain cor rections called Equation of Time. This can be applied to either of the times to convert them to the other. This conversion is necessary to bring the observed sun time to the time shown by our clocks, so as to make it of use in navigation on the earth's surface, by converting time locations and spaces into spaces and locations of arc, or longitude and latitude. Our clocks do not even keep any of the1 above mentioned times, only be ing regulated to Mean Time as shown by the Prime Meridian of Gr-nwich, or the zero meridian of Longitude, and verified for this country for the 75th meridian, or 5 hours slow of Green wich Time. So very close ore the calculations of the several observa tories throughout the world that they all agree on time down to a very few thousandths of a second, with Arling ton the closest of them all to abso lutely correct time throughout each year. It became necessary to establish some general time divisions, as it was impossible to operate railroads and even our daily lives, on times differ ent for every place east and west of each other. For example, even as close as Asheville is to , us, Waynes- ville time is almost two minutes slow er than is the Mean Solar Time of our neighbor. Therefore, the earth's sur face was divided into belts of long' itude approximately one hour in time, or 15 degrees of longitude wide, reck oned from the Prime Meridian of Greenwich. As the first 15 degrees multiple to cross the United States is that of the 75th meridian, our Naval Observatory was established close to this line, actually in 77" 03' 66.7" west from this meridian measured in time. Their " observations are cor rected to the 75th meridian. These time belts are given different names, as Eastern, Central, etc., standard time, and the time is kept uniform in the section about 7 on each side of the meridians of say 75 90, 105', etc. This is our clock time. These Standard Time divisions are reckoned slower than Greenwich, west ward to the 180th meridian, and fast of Greenwich eastward to the 180th mtridian. The 180th meridian is known as the International Date Line, be cause in crossing this line a ship eith er gains or loses a day. Either two days of the date of crossing arc used, or the date is rejected entirely. This is because in circumnavigating the earth a ship sailing westward travels with the sun and its day is lengthened. In sailing eastward the sun advances to meet the ship and passes on astern, and the ship's day is shortened. This gain or loss is at the rate of one hour for each 15 of longitude made good. Should this correction not be made at the 180th meridian a ship sailing around the world from and to Green wich, or other port, would find that her date was one day ahead of the local date if she had traveled to the eastward, and one day behind if trav eling to the westward. But the navi gator must continue to select all data from the Nautical Almanac for the Greenwich date and not for the ship's date. In the days of slow ship speeds it was customary to set the ship's clocks for ship time at noon observations each day. But now ships traveling east and west set their clocks to each 15 time belt as they are entered just as we change our clocks and watches for Eastern to Central Standard Time, T VA Controversy Center For satisfactory shoe repair ing, bring your shoes to us. We know how by many years experience. CHAMPION SHOE SHOP To Women: If you suffer every month you ov:6 it to yourself to take note of Cai'dui and find out whether it will benefit you. Functional pains of menstruation have, in many, many cases, been, eased by Cardui. And where mal nutrition (poor nourishment) had taken away women's strength, Car dui has been found to increase the appetite, improve digestion and tn that way help to build up a natural resistance to certain useless suffering. (Where Car dui (alls to benefit, consult a physician.) Ask your druggist for Cardui (pro nounced Card-u-i.") Thive! anywhere.. any day at Me SOUTHERN A jarejbr every purse,..! CENTS PERMIIE One Way and Round Trip Coach Tickets . ........ . . . . . for uch nBm hmML Round Trip Tickets. ... . . ' ..(or Mch mil trcvelad , . return limit IS days Coed id Sleeping end Parlor Cub oa ptrmeat of . :'; proper charges for spec occupied. Round Trip Tickets. . ... . ...far Mch roiW frUd . . . return limit t months. Good in filling end Pwlar Cm oa (MysMnt ol popor durgn lor ipac. ocnpfeoV One Way Tickets. .. . ...Good in Saoping tad P.tlor Gri on payawol V l pop ditrgw lor iptca occtrpud. ftlB. CONDITIONED Sleeping Cart, Dining Can and Coaehet on All Through Trains, Be Comfortable in the Safety of TRAIN TRAVEL Tor further information, consult your local agent, or write R. II. DeButts Assistant General Passenger Agent ASHEVILLE, N. C. SOUTHERN RAILWAY SYSTEM W - 9 tf Aerial view of Norris dam If vRJi Here Is an excellent new aerial view of Norris dam near Knoxville. Tenn center of the controversy raging over administration of the federal power and flood control project. Largest of the 11 TV A projects, the Norris dam Is costing $36,000,000. has a maximum height of 265 feet, is 210 feet thick at the base, extends for a distance of 1.860 feet, and has a power house with a present generating ca pacity of 100,000 kilowatts. etc. Sidereal is derived from the Latin word siduB, and means belonging to or of the stars. Sidereal Time is the "Daddy" of all time and it is from the observations of the passages of stars across the meridian that observatories secure their correct time. By the use of the stars the conditions which render the sun inaccurate as a time keeper are done away with. It is measured by the apparent yearly revolution of the stars resulting from the rotation of the earth, this rotation being so regular that the passage of the stars across the meridian occurs with great precision. Observatory clocks show Sidereal Time and their faces are divided to 24 in place of 12 Hours. This time is converted into Mean Solar Time for broadcasting to the world as the standard for our r-WWs. ShiDS reckon their time in daily periods of 24 hours, as it sim plifies the keeping ot navigational data. This 'means that twenty min utes after one o'clock p. m. is 13:20 hours, four o'clock p. m. is hours, while 11 p. m. is 23tihours. The Civil Day starts at midnight, as does our day, but is not divided in"to a. m. and p. m. periods. No particular star is used in Side real Time as a point of reference. Its prime meridian passes through the point of intersection of the celestial equator and the ecliptic the vernal equinox, or First Point of Aries Sidereal Time can be found from the passage of any star ver the merid ian of the observer, if the star's right ascension, or distance, from the First Point of Aries is known, just as a ship's position can be located on a chart if its distance from the "First Point" of Greenwich is known. The Nautical Almanac gives the right ascension, declination, Greenwich hour angle and time of transit at Greenwich for some fifty or more for, stars, and for the planets dav in the vonr tu ' manv more Htn . Paitioii that they may be used This is a very sketchy out'i r vv.i d.sr nnn.' hf u ""inival it may LK eno"gh to irinAo k 1 J has to know a lot . . i man is uia to him by th. j, the pilot clock, While navitT in its solutions o it ;,. i" the Nautical Alman,. ;.tabls. difficult subject to masL"f . ,!'" tical nurnnsps it-, ic tft most precision, and there U ak. ? . no room for errors on th,. . navigator. What, he should kn MUST Vnnu, if u ; Ull'i ... .. ,1C ,s where, and is to keen hi. ..v . leaving her bones on the rotki. r . r.imc SUOJecU fori be able to juggle it from ,, another through all of jU int'" relationships to every fQrm J wiwiiwiiuvoi wuowvttuon lur posj. The world's worst weathor .t. ed for the Antarctic the home blizzard. NEXT WEEK IS GLEAN-UP WEEK Every working day in the year we add to the cleanliness of the community by doing ex pert cleaning. CENTRAL CLEANERS MAIN STREET Phone 113 SEND US YOUR CLEANING FOR SATISFACTION "YOU SAVE ALL WAYS ...WITH A GENERAL ELECTRIC" Three ways that make the new 1938 General Electric refrigerator the finest, thnitiest refrigerator ever built. (1) BIGGER VALUE (2) LESS CURRENT (3) LONGER LIFE Today's General Electric refrig erators have twice the cooling ca pacity, four times faster freezing than the famous General Electric refrigerator made ten years ago; yet, the price today is $100.00 lower. General Electric refrigerators not only provide greater cooling ca pacity and faster freezing, but also actually cost far less to operate. In fact, today's General Electric operates for about one-third the cost of its 1927 predecessor. The long life of General Electric refrigerators has never been ques tioned. There are over a million General Electrics in use today that have been providing uninterrupted service for periods of 5 years or longer. HAS SO LiTTLE MONEY BOUGHT SO MUCH IN AN ELECTRIC REFRIGERATOR So little money buys so much General Electric refrigerator that practically every home can now afford this modem, thrifty refrigeration. America bought more General Electrics last year than ever before and this year's General Electric is even a better buy. Why wait? Be a bit thrift ier and get your new General Electric now! You can buy on our easy payment plan. It's Easy to Pay the General Electric Way There are 12 beautiful 1938 models to select from. You'll find just the size and price to suit you. There is 5 years performance Protection on the sealed mechanism a plan originated by General Electric. $9.50 Soot IS ALL YOU NEED !'--::'-- :;: :, .. . . 1 '- YOU WILL ALWAYS BE GLAD YOU BOUGHT A GENERAL ELECTRIC Massie Phone 33 JIain Street
The Waynesville Mountaineer (Waynesville, N.C.)
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April 21, 1938, edition 1
6
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