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History of wireless telegraphy and broadcasting in Australia/Topical/Publications/Australasian Radio World/Issues/1946 05

P.01 - Front Cover
The Australasian Radio World

Registered at the G.P.O., Sydney, for transmission by post as a periodical.

Price, 1/-

Vol. 10 - No. 12; May, 1946

P.03 - Contents Banner
THE AUSTRALASIAN RADIO WORLD

Devoted entirely to Technical Radio

and incorporating

ALL-WAVE ALL-WORLD DX NEWS

VOL. 10 - MAY, 1946 - No. 12

P.03 - Publication Notes
Editor, Publisher, Proprietor — A. G. HULL, 336 Waverley Rd., East Malvern, Vic.

Short-wave Editor — L. J. KEAST, 3 Fitzgerald Road, Ermington, N.S.W.

Ham Notes By — D. B. KNOCK (VK2NO), 43 Yanko Av., Waverley, N.S.W.

Advertising Representative — W. J. LEWIS, 20 Queen St., Melbourne, 'Phone MU5154

Subscription Rates: 6 issues - 5/3; 12 issues - 10/6; 24 issues - £1; Post free to any address in the world.

Address for all correspondence: Australasian Radio World, 336 Waverley Rd., East Malvern, SE5 Victoria

Printed by Bridge Printery Pty. Ltd., 117 Reservoir Street, Sydney, N.S.W., for the proprietor of the "Australasian Radio World," Elizabeth St., Sydney (Footnote P.52)

P.03 - Contents
CONSTRUCTIONAL —

Metropolis Four. . . . 23

The "Ferrotune" Superheterodyne. . . . 37

TECHNICAL —

What of the Future of "Ham Radio"? . . . . 5

Simple Impedance Measurements. . . . 9

The Channel Analyser. . . . 15

Loud Speaker Baffling Systems. . . . 31

A Decade of Good Battery Circuits. . . . 34

Reception Experiments. . . . 40

Ham Notes. . . . 41

PERSONAL —

Pages. . . . 5, 7, 11, 17, 20, 21, 33, 49

SHORTWAVE REVIEW —

Notes From My Diary. . . . 45

New Stations. . . . 46

Loggings. . . . 47

THE SERVICE PAGES —

Answers. . . . 50

P.03 - Editorial
EDITORIAL

Ten years ago "Australasian Radio World" was launched. Since then, despite the eventful times, it has made steady progress and gained the widest coverage of the Commonwealth and New Zealand. Every reader is a keen and active radio enthusiast, varying in status from amateur to professional. All are associated in the turnover of a big amount of money in the radio trade. Our recent co-operative effort with Mr. Magrath and his "Little Companion" kitset brought in orders for many thousands of pounds' worth of kits. That we know, but just who are our readers, how they are connected with technical radio and why they read "Radio World," are a few of the things we would like to know more about. In a nutshell: we'd like a closer personal contact with our readers. To start the ball rolling, we have in this issue a number of personal paragraphs telling the background of some of the contributors who have done so much to provide fine technical articles. This is just a step in the general direction of a new trend in editorial policy: the introduction of the personality angle. In this issue we deal with ourselves, but in future issues we hope to deal with you — our readers. After you have read this month's issue, we expect that you will find it easy to sit down and write us a line, telling about yourself and your work. All letters will be gratefully received; paragraphs from them will be used in future issues and are sure to interest all our readers. A. G. HULL.

P.05 - Technical - What of the Future of "Ham" Radio?
What of the Future of "Ham" Radio? by Don B. Knock (VK2NO) I SUPPOSE that in a veritable life time of amateur radio, during which my association with this evergreen hobby has enabled me to put much of my thought into print, I must have written tomes on the subject of the genus Ham, his welfare, activities, likes and dislikes. So that when your Editor (who comes from a brilliant radio family, and is at heart really a "Ham" himself) asked me to say something about Amateur Radio in general for this tenth birthday issue, I had no qualms. You see, I never get tired of writing about Amateur Radio, because this remarkably interesting phase of the 20th Century is something of which in itself I never tire. In other words, since I first broke the ice in the game (and that was 35 years ago), I have always found something fresh to think about and consider, afresh to think about and consider, or something to plan about, technically. There is always something that can be done in Amateur Radio. . . something. . . or a thousand and one things that one wishes to try. First let me say that in connection with the last 10 years I consider that "A.R.W." has been well to the forefront in catering for the Australian amateur radio man. True, little could be said about the VK's during the recent grim years, but right through that difficult period your Editor has maintained a delightfully refreshing flavour in his material. During the war many an erstwhile transmitting amateur turned over the pages of "A.R.W." and found lots of interesting reading, whilst amateur switches were off, with plenty of first-rate technical information. How well I remember the birth of this publication in 1936, and how the Ham flavour persisted throughout. And when your Editor purchased the Mag. from the originator, it was a certainty that with A.G.H. at the helm, brother of one who was this planet's No. 1 all-round Ham, there was likely to be much more than casual interest in the purely amateur side of Radio.

When the Jap war boomed to an end and matters began to stir somewhat in VK circles, it came as no surprise to me that A.G.H. set aside a liberal amount of space for writings of, by, and for the Ham in "A.R.W." and suggested that in my spare (?) time, I might like to put pen to paper. Thus, perhaps, I may write caustically of those who would deprive the transmitting Ham of his rights. . . and he has rights. . . as his history shows clearly enough. Or the Notes may take the form of doings around the bands, or may go into the merits of Ham apparatus by technical articles. You may be assured that whatever form it takes in these pages it will be of primary interest to the Ham, and in his interests. In the future of Amateur Radio, I have the greatest confidence, and above all the hope that those who govern the welfare of mankind through leadership of the United Nations will have the good sense to realise that embodied in Amateur Radio, as practised by modern youth, there is the most powerful weapon for world peace. That isn't a fantastic thought, but cold logic. Do you think that if, Internationally, Hams of all countries were given unfettered facilities for intercommunication, by wide and appropriate frequency channels, they wouldn't get to know each other better? Of course they would, and there would be more progress toward world peace than national leaders realise.

Getting to know the other man and his viewpoint over the air is a much better thing than hauling out lethal weapons, and setting out to obliterate him. You say: "But he might strike first." Answer to that is that he wouldn't feel that way about it if he were fully familiar with our point of view. Wise governments and leaders worthy of the name will encourage their radio-communing youth to the utmost, which means simply: cut out fettering restrictions, permit reasonable power ratings, don't rate a man's intelligence solely by his Morse code speed, and above all, make wide frequency allocations. Not only should the pre-war amateur frequency channels be restored forthwith everywhere: they should be considerably augmented. I suggest that the future of Amateur Radio in U.S.A. will be worth observance. Does anybody suggest that in commercial radio circles, industrially or in communications, there is chaos because a really Democratic nation gives its Hams a power rating of a kilowatt, permits traffic with message handling for third parties, and gets the war ban on frequencies removed without much delay. There were 60,000 Hams in U.S.A. before 1941. . . the estimate in a year or so is at least 250,000. That means lots of business for the radio manufacturers, whichever way you look at it. Here in Australia we had 2,000 pre-war licencees. My guess is that future devotees of the wholesome hobby of Amateur Radio in this country will, in a few years, also run in to the thousands. That being so, I take this opportunity of extending, well ahead, a welcome to the Hams, the VK's of the future years, and with "A.R.W." another decade of good writing and reading in the interest of radio experimenters, Hams, S.W.L.'s and constructors.— DON KNOCK (VK2NO)

P.05 - Personal - Don B. Knock
Personal - Don B. Knock

HAS been an active Ham for no less than 35 years, getting first insight into early day amateur radio in Colchester, England, in 1911. Can justly lay claim to be an "Old Timer" in radio. Born in Manchester, England, 1898. Started life as engineer apprentice and by 1916 was on active service World War I with R.N.A.S., serving in Middle East and Russia. Later served two years afloat as marine engineer with P. and O. Co. In radio trade in England with Sterling (now Marconiphone) Co., Burndept Co., and later engineer with BBC. Operated Ham station from London, G6XG, and was first G to QSO U.S.A. with low power (5 watts) on "95 metres" in 1924. In 1926 began to feel cramped in G. B. and came to Australia. Held position of C/Engr. with original Amplion Co., Sydney, in 1927, then Technical Editor of "Wireless Weekly" and "Radio in Australia and N.Z." Had established station A2NO shortly after settling in Sydney and this call sign quickly became known everywhere where there were Hams. Established radio stations at Wyndham, Nth. West Aust., for W.A. Government in 1930. Operated Ham station VK6NK from Wyndham and figured in radio rescue of stranded fliers Smith and Shiers. In 1931 designed and installed N.S.W. Country B/C station 2MO Gunnedah, but with radio journalism in blood returned to Sydney to become technical editor "Radio Monthly." During this period did considerable VHF work, some in conjunction with N.S.W. Police Dept. 1933 joined staff of Sydney "Bulletin" as editor "Australian Radio News" and in 1934 became Radio Editor of "The Bulletin." In between Ham activities held commission in Militia Sigs, and when September, ’39, struck went in to camp, as Lieutenant. Finished military service as Major, A.I.F. (Army Inspection) when obtained release from Army April, 1945, and placed on Reserve of Officers. Joined Philips organisation in June, 1945, and now engaged under Chief Engineer S. O. Jones on special developmental work.

P.07 - Personal - Allan Galbraith Hull
Personal - A. G. Hull

OF th e H u ll b ro th e rs it w as R oss A. H u ll w ho achieved w id est fa m e in ra d io b e fo re his u n tim e ly d e a th fro m a c c id e n ta l e le c tro c u tio n w h ilst c a r ry in g o u t telev isio n e x p e rim e n ts in A m e ric a in 1938. R oss e a rn e d fo r h im self w o rld -w id e re c o g n itio n as a g r e a t ra d io sc ie n tist a n d still, eig h t y e a rs a f te r his p a ssin g, his th e o rie s an d findings a re o ft^.i q u o te d in o v e rsea s a rtic le s on th e p ro p a g a tio n ' o f th e u ltra -h ig h -fre q u e n c y ban d s, th e c o -re la tio n b e tw ee n w e a th e r an d re c e p tio n c o n d itio n s a n d th e rem o te c o n tro l o f a ir c r a f t by rad io. ’W a y B a ck in 1915 B u t th e co n n ec tio n b e tw ee n ra d io a n d th e H u ll b ro th e rs d a te s b ack to th e W o rld W a r I, w hen in 1915 th e e ld e st b ro th e r, W illia p i H o w a rd H u ll, w as a n in s tr u c to r in w ireless te le g ra p h y a t th e M o o re P a r k cam p in S y d n ey, la te r se rv in g in M esop o ta m ia w ith th e A u s tra lia n L ig h t M o to r W ireless S q u a d ro n. W h en “ B ill” r e tu rn e d hom e to S t. K ild a in 1918 he fo u n d t h a t R oss, th e n a la d o f 16, h ad b een “ b itte n by th e ra d io b u g ,” a n d w as c o -o p e ra tin g w ith a te le g ra p h is t n am e d F re d W h ite r in th e c o n stru c tio n o f a re c e iv e r c o n sistin g o f a piece of le a d fro m a p en cil re stin g on th e ed g es o f tw o ra z o r b lad e s m o u n te d v e rtic a lly. W ith th is “d e te c to r” an d h e ad p h o n e s it w as p o ssib le to h e a r ' th e m o rse sig n als b e in g se n t o u t fro m V IM, th e b ig sta tio n o p e ra tin g fro m th e M e lb o u rn e D om ain. B y a b o u t 1922 R oss w as o p e ra tin g his ow n e x p e rim e n ta l tr a n s m itte r, w o rk in g A m e ric an H a m s across th e P acific a n d b ro a d c a stin g re c o rd e d m usic — som e y e a rs b e fo re a n y b ro a d c a stin g as we know it to day. K een ly in te re s te d, b u t “ to o y o u n g ” to be allo w ed to o p e ra te th e a m a te u r tr a n s m itte r w as R o ss’s y o u n g e r b ro th e r, A .G ., b a b y o f th e H u ll fam ily. B y 1929 R oss h a d b een to A m erica — h eld th e p o sitio n o f te c h n ic a l e d it o r o f “ Q S T ” a t th e h e a d q u a rte rs o f th e A .R .R .L ., a n d been se n t hom e to A u s tra lia a g a in by th e A m e ric an im m ig ra tio n a u th o ritie s as he w as only in th e U .S. on a v isito r s p a ssp o rt. On his r e tu r n to A u st r a lia R oss b ecam e te c h n ic a l ed ito r o f th e S y d n e y “ W ireless W ee k ly ,” w hich m ad e ra p id p ro g re ss u n d e r his g u id an ce. A f te r a b o u t a y e a r R oss m a n a g e d to g e t on to th e A m e ric an q u o ta a n d ru sh e d off back to th e US. to resu m e his p o sitio n w ith “ Q S T .” T h e d ire c to rs o f “W ire le ss W ee k ly ” g la d ly a c c e p te d a su g g e stio n fro m R oss th a t his y o u n g b ro th e r m ig h t ta k e his p lac e as th e ir T ec h n ica l E d ito r, a n d so A .G. cam e in to th e ra d io lim elig h t. H e w as ab le to c a rry on th e g ood w o rk s ta r te d by R oss, a n d b y 1934 th e c irc u la tio n of “ W ireless W e e k ly ” w as up to 84,000 copies p e r w eek. In 1936 A. G. H u ll m ad e a w o rld (Continued on next page)

ly ,” v isitin g th e U n ite d S ta te s, E n g lan d, H o llan d , F ra n c e a n d G e rm an y to in v e stig a te tele v isio n a n d ra d io d ev elo p m en ts. B y 1939 th e old “ W ireless W ee k ly ” h a d w an ed c o n sid era b ly a n d it w as d ecid ed by A sso c ia ted N ew sp a p e rs th a t it w o u ld be b e tte r to s t a r t a new m o n th ly p u b lic a tio n to c a rry th e te c h n ic a l a rtic le s w hich h ad been a p p e a rin g in th e “ W ee k ly .” T h e new p e rio d ic a l w as called “ R a d io a n d H o b b ie s,” a n d A. G. H u ll w as its ed ito r. S u ccessfu l V e n tu re “R a d io a n d H o b b ie s” w as a n in s ta n t success, a n d c o n tin u e d to be su ch a success t h a t a f te r w a tc h in g nin e issu es in to p ro d u c tio n, A. G. H u ll d ecid ed to v e n tu re fo rth in to th e p u b lic a tio n b u sin ess on his own a c c o u n t, a n d p u rc h a se d th e g o o d will o f “ A u s tra la s ia n R ad io W o rld ” fro m E a r l R e ad, w ho h a d com e acro ss fro m N ew Z ea la n d to s ta r t it a few y e a rs b e fo re. W ith R e ad c a rry in g on as A d v e rtis in g M a n a g e r th e “ R ad io W o rld ” m ad e g r e a t p ro g ress u n d e r its new o w n ersh ip, th en th e w a r clo u d s th ic k e n e d , p a p e r r a tio n in g w as in tro d u c e d a n d “ R ad io W o rld ” h a d to c a r r y on as b e st it co u ld th ro u g h th e w a r y e a rs, w h ilst A .G. w e n t to M e lb o u rn e to do a sp o t o f w a r effo rt, h av in g been re je c te d fro m m ilita ry serv ice on a c c o u n t o f m ed ical unfitness. T w o a n d a h a lf y e a rs o f m a n a g in g a fa c to ry ru n n in g 24 h o u rs a day, 7 day s p e r w eek, on m u n itio n s w o rk , w ith o v er a h u n d re d fem ale “ e n g in e e rs,” b ro u g h t a b o u t a th o r o ugh c ra c k -u p in h e alth, b u t a sp le n did re co v e ry w as m ad e la te r w hen p u ttin g in e ig h t m o n th s o f w ork u n d e r th e k in d ly eye o f C olonel Jo n e s o f th e D ire c to ra te o f R ad io a n d S ig n a l S u p p lies, M in istry of M unitions. T o d ay A n d so we com e to to d a y w hen difficulties ab o u n d, b u t slow ly an d su re ly th e “ A u s tra la s ia n R a d io W o rld ” is e m e rg in g fro m th e clouds of w a r a n d, as d o u b tle ss you w ill SIESTA 1 ag ree a f te r re a d in g th is issu e, is w ell on th e w ay to re g a in in g its p re w a r sty le. S tric tly P e rso n a l P erso n ally ,- A. G. H u ll lik es to be c o n sid ere d as ju s t a n o th e r m an - in -th e -stre e t, a n d a lth o u g h ra d io is his m ain hob b y, he h as o th e r h o b bies as w ell. P rid e of p lace goes to his fleet o f c o n te st m odel a e ro p lan e s, w ith th e ir tin y p e tro l m o tors. H e w ill go a n y d istan c e fo r a c o n te st a n d h as h ad m an y m a jo r successes, h o ld in g th e A u s tra la s ia n N a tio n a l C h am p io n sh ip a n d o th e r titles. N e x t com es p h o to g ra p h y, and a lth o u g h still in th e so u p -p la te s-o n - th e -k itc h e n -ta b le sty le, he does all th e p h o to s fo r “ R ad io AVorld,” as w ell as a te rrific n u m b e r o f p icto ria l shots. S p e a k in g o f sh o ts, A .G. is also a k een rifle sh o t, a w in n er o f ch am p io n sh ip s in th is sp o rt. H e jo in s all his h o b b ies to g e th e r b y p u ttin g in his h o lid ay s an d sp a re tim e c ru isin g in his c a ra van in to th e b a ck c o u n try in se a rc h of fo x es a n d p ic tu re s to sh o o t, sto p p in g o v er a t th e open sp aces to te s t th e a ir fo r th e rm a l c u rre n ts w ith his m o d el p lanes.

P.29 - Ten Years of Printing Service
Ten Years of Printing Service

THIS tenth birthday issue would hardly be complete without tribute being paid to the printers who have done the actual job of mechanical production of the issues. For the whole ten years the work has been done by the Bridge Printery Pty. Ltd., under the personal supervison of Mr. Fred Wales and his son Noel. As any publisher will readily agree with us, one of the biggest problems in the publishing game is to get a printer with a conscience who will get your magazine out on time, without too many errors and at a reasonable price. In our particular case the printing problem has been further aggravated by war-time circumstances which made it necessary for the editorial work to be done in Melbourne with the printer more than 500 miles away in Sydney. Even when you can sit on the printer's doorstep it is difficult enough, but to supervise a printer by mail — well, most experienced editors will tell you that it would be an impossibility. That it was managed, and highly successfully, too, is a splendid testimonial for the Bridge Printery. The wrapping of subscribers' issues and the bulk postage of them is also carried out by the Bridge Printery and the fact that complaints about non-delivery don't amount to one-twentieth part of a percent, indicate that this job is also done thoroughly.


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Planet Earth/5h. Earth’s Endangered Lakes and the Limits of Freshwater Sources

Earth’s Endangered Freshwater
The lakes of Earth are slowly disappearing, including the largest natural lake in Utah, the Great Salt Lake. Lakes provide a regional base level for the flow of freshwater, that captures meteoric water. Meteoric water is water derived from precipitation in the form of rain and snow. This includes water from lakes, rivers, and ice-melts, which all originate from precipitation indirectly. Meteoric water is in demand, particularly in the dry desert latitudes between 30° to 40° latitudes, where water scarcity is a major issue. Some of the largest and fastest growing cities in the United States are located in these southwestern deserts including Phoenix, Las Vegas, Los Angeles, Denver, and Salt Lake City. These cities and the agricultural regions around them are dependent on a fresh supply of water. The urban growth of the American Southwest has led to many projects to divert freshwater toward cities and prevent water from reaching either the ocean or saline lakes where the water can no longer be used for drinking or agriculture without costly desalination processes. One of the most drastic examples of this capture of freshwater was the development of the aqueduct system that feeds into the urban center of Los Angeles. For the last hundred years, the city of Los Angeles has diverted large amounts of water from the water drainages of the Colorado River Basin, the Owens Valley, and Feather River Basin. The story of the dry lake beds of Owens Valley is a story of how water was diverted across the Mojave Desert in man-made canal systems to transport freshwater to the city, but subsequently resulted in the draining of Owens Lake. Owens Lake was completely drained by the 1940s, other naturally occurring lakes have also shrunk in the last fifty years from water usage in Southern California including Mono Lake, the Salton Sea, and in Nevada Walker Lake, which has been at record low levels. Utah has seen the lake levels of the Great Salt Lake drop to 35% of previous lake levels more than a century ago, when John Fremont mapped the geography of the Great Salt Lake in the 1840s. At that time Lake Utah nearly connected with the Great Salt Lake along the Jordan River, and the lake contained six islands. Today the Great Salt Lake is a sliver of its former expanse, with a dramatic drop in lake levels since the early 1980s, when levels were higher, due to higher runoff. The Great Salt Lake is fed from three major rivers, the Bear River to the north, the Weber River from the east, and the Jordan River from the south. The Great Salt Lake occupies a low basin, known as the Great Basin which extends across much of western Utah to the Nevada border. This large basin was once entirely filled with a massive lake called Lake Bonneville about 25,000 years ago, which extended into Cache Valley, draining into the Snake River valley toward the north in Idaho. Today, the lake lacks any external drainage, and the water is subjected to evaporation in the dry climate. This dry lake bed has left behind massive deposits of salts, which form salt flats that extend for miles on the flat topography of the Great Basin, which is only broken by graben mountain ranges that poke above the barren landscape. Few plants can tolerate the salt, and the ground lacks vegetation. Wind storms from the west carry salts and other dust particles in suspension, which results in respiratory health issues for people living on the salt flats and dried up shorelines of the Great Salt Lake. The major reason for the declining lake levels is due to the construction of dams and diversion of water away from the lake. This includes Deer Creek Reservoir above Provo, Jordanelle Reservoir near Park City, and Pineview Reservoir near Ogden, which capture freshwater for use in municipal drinking water and agriculture for the Salt Lake City metropolitan area. The plight of the Great Salt Lake is not in isolation, many other saline lakes on Earth are also shrinking due to increased demands on freshwater. Some of the most dramatic examples of saline lakes disappearing on Earth can be found with the Aral Sea which lays across the Kazakhstan and Uzbekistan border in Asia. The Aral Sea used to be the fourth largest lake on Earth, covering 26,300 square miles (about the size of West Virginia), but in 2009 the lake shrunk to only 2,600 square miles, a 10% of its previous size. This reduction was due to the diversion of freshwater through canals and dams, toward regions with agricultural crops between the border of the two countries. Lake Urmia in Iran, has also seen a dramatic decline in lake levels since the year 2000, with water diverted for crops, resulting in a dry lake bed forming in the northern part of the country. As human populations grow, freshwater becomes a valuable, but limited resource.

The Chemistry of Freshwater
Freshwater contains fewer dissolved salts than ocean water, but does contain some dissolved molecules. Rain tends to be acidic, with a pH between 6 to 7 caused by the dissolution of carbon dioxide in the atmosphere which forms carbonic acid. Streams tend to buffer this somewhat with pH between 6 to 8, but in general freshwater tends to be more acidic than ocean water, which has a pH higher than 8. This low pH results in the ability of freshwater to dissolve calcium carbonate to form bicarbonates and calcium ions. Calcium carbonate is abundant in rocks, particularly limestones. The ability of freshwater to dissolve calcium carbonate into ions of bicarbonate and calcium results in what is called hard water and soft water. Hard water contains more ions of bicarbonate and calcium, as well as magnesium, which results in white crusty rings of calcium carbonate in pipes, faucets and bath tubs. It also makes it difficult to wash soap off. Soft water contains less ions of bicarbonate and calcium, and more easily rinses soaps off your skin. Often houses are equipped with a water softener, which removes some of these ions, to make water easier to use when cleaning and in the shower. Often freshwater will become hard when it passes through a region with thick limestones and other calcium carbonate-rich rocks. As a result of its lower pH, freshwater dissolves calcium carbonate in limestones resulting in something called karstification. Karstification is the process of water dissolving rock to produce an irregular surface on rocks, and if allowed to continue for many years, eventually form caverns and caves underground.

Ground Water
Much of the world’s supply of freshwater is found underground, where water occupies the spaces between the grains in rocks. Porosity is the amount of space within a rock. A rock, such as limestone which has undergone karstification is said to have high porosity because there are many spaces within the rock for water to occupy. Permeability is how well-connected spaces are within rocks. If a rock has high permeability, water is able to easily flow between spaces within the rock. An aquifer is a rock layer that has both high porosity and high permeability, allowing water to easily flow and occupy the space within the rock layer. Water wells are often dug down to an aquifer to extract this source of freshwater from below ground. The water table is the dynamic level that water can be found in the subsurface, and fluctuates greatly depending on the season, and local precipitation of the area. Aquifers are filled during times of recharge, where rain or snow melt trickles down into these layers below ground, or where water flows above these areas along the course of a river or below a lake. Discharge occurs when these aquifers contribute water to a flowing stream or river, often in cracks where the aquifer is exposed above a canyon or river cut, producing a spring. A spring is any flow of groundwater emerging from the ground surface due to discharge.

This hidden source of underground freshwater is an important resource to understand, as drainage of freshwater from these regions often goes unnoticed until the water table drops and wells go dry. This underground source of freshwater can become contaminated, making it unsafe to drink. Freshwater can become concentrated with sulfates and chlorides, particularly in arid regions, where sulfur-rich hydrogen sulfide accumulates with buried organic carbon and salts, like sodium chloride and potash, resulting in toxic or noxious bitter water. Underground disposal of waste water (from oil and gas extraction or uranium mining) can also contaminate ground water that can make it into the rivers and lakes through an aquifer. Cleanup of contaminated underground water is extremely difficult and very costly.

Water Quality
Water quality is an important issue, and one that most people take for granted, until they do not have a source of clean drinking water. LeeAnne Walters was of those people, raising twin toddlers and a teenage son, she assumed that the water her family drank in their Michigan home was safe in 2014. Water from a faucet in the United States is often taken for granted to be healthy to drink, and often assumed that it undergoes testing to assure that it is safe, but Michigan was facing harsh economic conditions in early 2014, as the city of Flint was looking to save money, and had switched water sources from Lake Huron to the Flint River. The Flint River which runs through the city would save the city a large amount of money, since they no longer had to pay for the source of lake water from Lake Huron. The local Flint River contains freshwater that has a lower level of pH and is softer (containing less calcium carbonate) than water sourced from Lake Huron, but also contains more chloride (from sodium chloride put on icy winter streets) and bacteria. The switch was made, but testing of drinking water was not carried out to see if the switch was safe for citizens to drink. For months, the water from faucets in Flint, Michigan, was observed to be discolored. The elevated chloride reacted to the old lead pipes that carry drinking water to various neighborhoods in the city. Citizen’s began to complain of the water tasting bad. They complained to public officials with the fear that the water was no longer safe to drink. The city officials argued that that testing was being carried out, and it was safe to drink, but LeeAnne Walters who lived in the neighborhood was not convinced. As a medical technician, she was trained in science, and began collecting samples of water from her neighborhood. She sent off these samples for testing to Marc Edwards at Virginia Tech, who specializes in water quality, particularly how water can become contaminated from lead pipes. Testing of the water samples collected by Walters showed extremely high levels of lead within the drinking water. Chloride is a corrosive element that oxidizes with metals, such as lead, and typically is removed from drinking water to prevent corrosion when passed through lead pipes. The excessive lead from the dissolution of these old pipes by the chloride in the drinking water was slowly poisoning thousands of people in Michigan. Lead (Pb) in water is taken up by the body in different organs, resulting in gastrointestinal, neuromuscular, and neurological symptoms. It also causes growth and developmental issues in children, such as severe learning disabilities. The publication of LeeAnne Walters and Marc Edwards study on contamination of water in Michigan inspired another scientist named Mona Hanna-Attisha to follow up with a study based on electronic medical records of blood samples collected from children living in Flint, Michigan. She published her scientific results demonstrating high levels of lead in the bodies of children living in Michigan, in the journal American Journal of Public Health in 2015. The fallout of the study revealed a conspiracy by elected officials to save tax payer money by diverting water from one source to another, and then covering up the results of this change on water quality reports. The discovery would not likely have been made, if LeeAnne Walters had not undertaken the initial study by gathering water samples to be tested and sending those samples to be tested by an outside lab. Science is something that anybody can do and should do, it is a valid way to test and retest any hypothesis, and in the case of the Flint Water Crisis, such retesting of the water resulted in saving people’s lives in Michigan. In 2018, LeeAnne Walters was awarded the Goldman Environmental Prize, and has been campaigning for safe drinking water ever since.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Eric 6 User's Guide

About This Guide
The goal of the Eric 6 User's Guide is to help users of Eric 6, a rich and sophisticated integrated development environment (IDE) for Python and other programming languages, notably Ruby.

The Eric 6 User’s Guide is under development. The intention is that it will contain detailed information about Eric’s main features, tools and benefits and demonstrate them through some typical use-cases.

The guide will probably be most useful to those with some Python experience who are new, occasional or basic users of Eric. Although it may turn into it, the guide is not currently intended to be comprehensive documentation of Eric’s every feature; rather, it focuses on the most popular, useful and powerful ones. It supplements the information available in the Technical Report prepared by Pietro Moras.

The Eric developer is not involved in the creation of this Wikibook. Any errors, omissions or misstatements here should not be blamed on him.

You Can Help!
The guide is being built by a group of grateful Eric users. You can help by joining in - if you have something to add, don't hesitate. You are strongly encouraged to do so. There are many things you can do: Click here for details.  You can join Wikibooks as a writer/editor and contribute your own content or improve the existing text. If you're planning to join Wikibooks, you should probably first review the Wikibooks policies and guidelines.
 * edit existing text to correct errors, improve the writing, or make additions.
 * add new material: use-cases, tutorials or reference material. It doesn't have to be a magnum opus. Pick a favourite Setting or Extra - maybe only a few sentences or paragraphs.
 * upload new images (screen shots or sample renders) - read the details below before you do though.
 * join Wikibooks as a writer/editor by creating an account.

You don't actually need to join Wikibooks to edit a page - joining brings added benefits but doesn't prevent others from editing. If you edit that way, you will be listed as anonymous; your IP address will be recorded and displayed.

There's a very useful summary of how to edit here. If you're not ready to edit directly, you could make suggestions on a page's Discussion tab or on the Eric Mailing List.

How to Edit a Page
To edit any wiki page (including this one):
 * 1) Click on the Edit tab at the top of the page.
 * 2) Make your change in the large text box.
 * 3) Type an explanation of your change in the Edit summary text box below.
 * 4) Click on the Show preview button below the edit summary to preview your change.
 * 5) If you're satisfied with the result, click on the Save page button.

Note that you don't need a Wikibooks user ID to edit - you will be listed as anonymous. Instead of a user name, your IP address will be recorded and displayed.

Your contribution will be reviewed before it is officially published.

Things you shouldn't add to pages:
 * external links that are not directly related to the module
 * comments or questions regarding the text

To ask questions and make comments about exiting material:
 * 1) Click on the Discussion tab at the top of the page. This will take you to the corresponding talk page.  Note that the talk page name begins with the "Talk:" prefix.
 * 2) If the topic of your question or comment is under discussion, edit the relevant section.
 * 3) If it's a new topic, click on the Add topic tab at the top of the talk page to start a new discussion.
 * 4) Sign your message by typing ~ at the end. (This will expand to your username and the date.)
 * 5) Remember to save your edit when you're done!
 * 6) To return to the WikiBook, click on the Book tab at the top of the talk page.

TODO: adapt to E6UG

How to Add a Page
To add a new page (a section, use-case, subsection) to this book:
 * 1) Edit the Table of Contents section (below) and add a list item with a descriptive wikilink. When you save your edit, the link to the new page will display in red (as a red link); links that connect to an existing pate display as a blue link.
 * 2) After saving your edit, follow the red link to create the module and begin adding content to it.
 * 3) To make it easy to read the book in sequence, each module should have navigation links to the previous module and the next module. Provide these links by transcluding the NAV template at the top and bottom of the page, as shown on the demo page.  (If you expect the module to be moved elsewhere in the sequence, you can skip this step.)
 * 4) Preview your work. When you're satisfied with it, use the Save page button to add your new module to the wiki.
 * 5) If you provided navigation links, update the NAV templates on the previous and next modules, if they exist.
 * 6) If you didn't provide navigation links, please ask someone to insert your new module in an appropriate place. One way to do this would be to create a talk page for your new module and type your request there.

Images
Images are a vital part of the User's Guide. They clarify instructions, provide a point of reference, and improve the learning process. However, if the image's copyright is not attributed correctly, we must remove it. This can make a once-great addition useless. Even if you believe you know what copyright to use, please check the Checking copyright page to see how and where you should add copyright information. Please make sure every image you use is not copyrighted or that you have permission to use it.

Before uploading an image: TODO: adapt B3D:N2P copyright stuff. If you use a Commons image in this WikiBook, please use one of the categories shown in the templates on proper Blender images copyright to make it visible from the category links in the image portfolio.
 * Search Wikimedia Commons or look in to see if the image you want to use already exists. (Uploading duplicate images is wasteful.)
 * Remember to attribute the work of others.

How to Create a Wikibooks Account
Creating a WikiBooks account is simple. Having an account brings several advantages. Click on Create Account in the first line of any Wikibooks page. Adding your email address is optional but low risk, as it is not disclosed to others when they send you a message.

Organization
The guide is organized into the following sections:
 * 1) Getting Started
 * 2) * Overview
 * 3) * Installation and Upgrading
 * 4) * Quick Start
 * 5) * UI Tour
 * 6) Editing with Eric
 * 7) * Quick-And-Dirty Editor
 * 8) Eric for GUI Development
 * 9) Settings
 * 10) Extras
 * 11) * Virtual Environments
 * 12) Other Tools
 * 13) Appendices
 * 14) * Troubleshooting
 * 15) * FAQ
 * 16) * Licensing and Attributions
 * 17) * Contributors
 * 18) * Acknowledgments

title: Eric 6 User's Guide


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Talk:Eric 6 User's Guide

How you can help to be expanded - similar to Blender Noob to Pro

The sections referred to under Organization will be linked to those pages once they exist. Basic copy already exists for them - it merely needs to be transferred to new pages here.

-- Rdhill734455 (discuss • contribs) 23:38, 10 June 2020 (UTC)

title: Talk:Eric 6 User's Guide


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User:CapitalistCamanchi

I am currently focusing on Wikijunior:North America, Wikijunior:Big Book Of Cities And Towns, and Wikijunior:Portland Oregon. If anyone else is interested in working on these topics let me know.

title: User:CapitalistCamanchi


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User talk:The Optimistic Guy/huggle3.css

Double redirect
Please make this page a redirect to https://en.wikibooks.org/wiki/User:Rutilant/huggle3.css as this is a double redirect. (Also pinging an admin if they can do it: ) --Red-back spider (discuss • contribs) 21:49, 11 June 2020 (UTC)


text: Category:Book:Eric 6 User's Guide

title: Category:Book:Eric 6 User's Guide


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Planet Earth/5i. Earth’s Ice: Glaciers, Ice Sheets, and Sea Ice

Glaciers
In late summer there is a valley high in the Bernese alps, that is filled with the cracked and tumbled rocks that appear to have been pushed and bashed down the valley floor by giants. Large boulders, jagged and angular point upward to the surrounding steep mountain sides. These are the Aargletschers, German for Aare Glaciers, a system of two major glaciers that are the source for the Aare River in Western Switzerland. The glaciers today have retreated up the valley, a relic of their former glory, with the northern glacier Lauleraar and southern glacier Finsteraar retreating into their respective separate valleys, but two hundred years ago these great glaciers extended down the valley meeting for a combined glacier (called the Unteraar glacier) that extended for 3 kilometers, burying these rocks in thick sheets of frozen ice. The Swiss painter Caspar Wolf captured these glaciers in beautiful and dramatic paintings of large boulders tossed by giants, and massive ice sheets tumbling down the valleys of mountains, piles of ice and snow. Of blue green ice that jaggedly pointed skyward, from a landscape that bears little resemblance to the warmer Earth today. Near where the two glaciers meet, was constructed a small shelter of rocks, named ironically the Hôtel des Neuchátelois. It was here in this shelter surrounded by ice and snow, that one of the important geological studies was carried out by a Swiss scientist named Louis Agassiz, a scientist who would have a major influence on how we see the world today. In 1832, Louis Agassiz was hired by the University of Neuchâtel in Switzerland to teach natural history. He was at the time engrossed in studying tropical fish brought back from early expeditions from the Amazon Basin of Brazil. The mountainous cold landscape of the Swiss Alps, unfortunately, was not the most ideal place to study tropical fish, but Agassiz discovered that by hiking around the mountainous region he could find the petrified remains of fish that lived along ago, buried in the rock layers. Embarking on a study of these fossil fish, Agassiz would spend most days in the mountains splitting rocks with his rock hammer and finding new species of long dead fish from millions of years ago. As Agassiz explored the mountains for new fossil sites, he began to see the valleys in a different light, observing how they appeared to be carved by the motion of ice. This captured his interests, and he began to lead field trips with his students to study the motion and movement of the glaciers that filled these valleys. Using the rock shelter as his base of operations, Agassiz drilled down through the ice to measure its thickness, and mapped the glaciers extent, as well as the boulders that were carried on its surface. His most famous experiment was sinking poles in a straight line across the glacier, and observing over the course of several years the poles in the center of the glacier moved downslope, as if the ice flowed like a slow-moving river.

How Ice Carves the Earth
Agassiz’s study of glaciers, demonstrated the powerful force of ice in the shaping of Earth’s surface. Glaciers form either at high latitudes near the poles or at high altitudes on mountain peaks. When snow falling each winter is greater than the amount that melts during the summer, the remaining dense ice that survived the summer melt advances down slope. A glacier is a persistent body of ice that moves down slope under the influence of gravity. First forming on the tops of mountain peaks, these glaciers carve a bowl-shaped depression called a cirque, it is from here that the glacier will flow down the mountainside, carving the steep rocky slopes into a bowl shape flanked by steep peaked mountains, called an arête. The famous Matterhorn between the border of Switzerland and Italy is an example of an arête, formed by carving glaciers on each side of the mountain pinnacle. Glaciers flow and expand down the valleys, carving U shaped valley floors. This flowing ice acts like a conveyer belt for boulders and large rocks that fall from the over-steepened valley sides. These boulders and rocks are carried down the valley on top of the thick sheets of ice. Near the valley ends, the glacier will melt with the lower altitude and warmer temperatures, and the large rocks and boulders will tumble out forming a moraine. Moraines are thick piles of jumbled rocks and debris that are carried by glaciers, and they can form on the edges of glaciers, where they are called lateral moraines and at the end of the glacier they are called terminal moraines. These piles of rock are characterized by being poorly sorted (large and small rocks), with an appearance that they were formed by a large bulldozer. This poorly sorted, jagged and angular pile of rocks is called till, and when lithified into rock, tillite. Till differs from sediments transported by water in rivers, as those sediments will be polished into cobbles and rounded pebbles. Till is just a jumble of rocks of all sorts and sizes. Often near the terminal moraine is a small lake or pond called a tarn. A tarn often acts as a catchment for melt waters from the glacier. When glaciers completely melt, and are no longer permanent bodies of ice, often their legacy is found in the carved U-shaped valley, and melted waters can be found in a tarn at the base of cirques. Glaciers are found on the surface of the Earth in two types of locations, those found in the alpine regions in temperate zones, and polar regions near the north and south poles, such as the large ice sheets that are found in Greenland and Antarctica. Study of glaciers has demonstrated a record of their retreat as the Earth has warmed during the past century. To form, a glacier needs to be continually added to through the accumulation of snow and ice during the winter, which must be greater than the ablation or melt of snow and ice during the summer. If the ablation of the ice and snow in the summer is greater than the amount added in the winter, the glacier will retreat. This forms two regions of a glacier, near the head or source will be the accumulation area, while the ablation area will be near the terminus or tail of the glacier. Between them is the equilibrium line which is the boundary line between the area of accumulation and ablation. This can often be observed in satellite images of glaciers, where the accumulation areas are crisp white, with fresh snow, and ablation areas are darker colors as the surface melts and exposes rocks and melt water on the surface. Each year the glacier will undergo growth during the winter months, and melt during the summer, and exhibit a changing mass balance depending on how much new ice was contributed to the glacier, and how much was ablated by melt. Most glaciers on Earth today are retreating, and shrinking. These shrinking glaciers are leaving behind piles of till, which record their retreat over time. As the glacier retreats up the valley, the piles of till form a continuous record of a terminal moraine, which records the retreat of the glacier from its greatest extend. Documenting and determining the age of these rocks at the terminal moraine is most often done using the radioactive isotope beryllium-10, which accumulates in quartz minerals, that contain oxygen atoms which when are exposed to sunlight can change to radioactive isotope beryllium-10, that will decay back to oxygen, but the amount of this isotope can be used to determine how long the rock was exposed to light, and how long ago it was unburied from the ice that carried it to the terminal moraine deposit. Globally, glaciers reached their last maximum extent about 25,000 years ago, during the last Ice Age. This is about the same time that according to the work of Milutin Milankovic, that Earth’s orbit would produce a more variable and cooler climate for Earth. Scientists refer to these periods as Glacial and Inter-Glacial periods in the recent geological history of Earth.

The Great Ice Age
For Louis Agassiz the studies of glaciers in the Swiss Alps suggested that much of the Earth was once covered by ice sheets and large glaciers, but fellow scientists at the time were skeptical. One of his greatest skeptics was William Buckland, who came to visit the Swiss Alps. Buckland was a professor in Oxford, England, and is more famous today for naming the first dinosaur, Megalosaurus in 1824. But during his tenure as lecturer of geology, he was a noted advocate for the idea of Earth’s surface had been shaped by a great flood. Buckland’s deluge model, suggested that all boulders and rocks on the surface of the Earth had been transported by an ancient large flood. The two scientists met in Switzerland and despite their differing opinions became friends, as Agassiz argued for an Earth shaped by ice, while Buckland argued for an Earth shaped by water. Agassiz demonstrated how thick layers of ice flow slowly over the landscape, due to a unique property of ice and the influence of gravity. Like a stack of playing cards, the internal crystalline structure of the ice undergoes deforming stress promotes the motion of the ice downslope. This ice can freeze and thaw particularly near its contact with the rock floor and walls of the mountain valley. This can produce glacial grooves or striations on the rock surface as the ice drags grains plucked from the rock’s surface and dragged over it. This melt is enhanced at great thicknesses by the increased pressure the ice is subjected to at this depth, which decrease the melting/freezing point below 0° C. This high pressure from very thick sheets of ice allow the glacier to skate on this narrow floor of melt waters. This freeze/thaw cycle at the ice/rock interface produces what is called rock flour, finely ground minerals that provides important nutrients to forests downslope from the glacier. While Buckland began to be convinced of the evidence gathered by Agassiz that glaciers and ice had shaped the European Alps, he invited Agassiz to Scotland to see what evidence they could gather there for evidence of ice shaping the surface of Scotland. The two scientists embarked on this trip, each discussing at depth the shapes of valleys, mountains and features on the landscape of Scotland. They observed fjords, where ice craves a large U-shape valley that later is filled with ocean water, and found examples of piedmonts (foot mountains) where glacial till accumulated on the flanks of mountain ranges. They found drumlins scattered across Scotland, narrow hills which were all oriented in the same direction, as if a giant ice sheet rode over these hills shaping them like a wood carver, as well as esker, narrow sinuous hills formed by the motion of meltwaters beneath gigantic ice sheets. Most stunning of all were the erratics, large angular boulders that appeared to have been dropped out of long-ago melted ice that carried them great distances. These monolithic stones were scattered across the Scottish landscape. Agassiz saw the evidence of great ice sheets that once covered Scotland and England. In time, Buckland was convinced too of a great Ice Age in the ancient times. His deluge model for the surface of Earth fell out of his mind, as he realized the evidence they had gathered implicated a great frozen history to Earth. Agassiz’s ideas of an Ice Age in Earth’s history were further cemented when he moved to the United States in 1846. Agassiz initially intended to visit the country to study evidence of glaciers in North America, and continue his work on fossil fish, but enjoyed the country so much he decided to stay. To Agassiz’s eyes, North America was carved by great glaciers. The Hudson River of New York, a flooded U-shaped valley formed by massive ice sheets, the Finger Lakes sculpted by ice. Most astonishing were the recently mapped Great Lakes, which formed through the motion of thick layers of ice that scooped out these areas, and filled them with water. Along the northeastern coast he observed how Long Island was a gigantic terminal moraine as ice dumped poorly sorted sediments and till forming the unique coastline of the United States. From Boston to New York Agassiz observed striations on boulders and erratics that were scattered across the landscape of New England. Agassiz was appointed a professorship at Harvard University, and in 1859 founded the Museum of Comparative Zoology on the campus. During the American Civil War between 1864 to 1865 he lectured on Glaciers and the Ice Period in Earth’s past. His ideas would likely have carried less influence had not his second wife Elizabeth Cabot Cary, a prolific writer, promoted his research. Elizabeth Cary was a professor during a time when few women were permitted to teach, she published an influential textbook, called A First Lesson in Natural History in 1859, under a pseudonym, using the genus name for baneberry (Actaea), a beautiful flowering plant, but producing highly toxic and poisonous berries. Elizabeth Cary taught young ladies near Boston in a women’s college, and was a leading supporter for the instruction of blind students in the study of natural history. Together they are buried near Boston, under a unique tombstone, a boulder shipped to the United States having been selected from the glaciers that inspired their mutual admiration for the power and beauty of a planet carved and shaped by ice.


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Planet Earth/6a. Journey to the Center of the Earth: Earth’s Interior and Core

The Interior of the Earth
It is likely that you do not often think about the 6,371 kilometers below you, the distance to the center of the Earth. And you likely take for granted the Earth is solid all the way down to the core of its center. The solid interior of the Earth is nearly impossible to observe, and so it is no surprise that science fiction writers such as Jules Verne, who wrote the classic book Journey to the Center of the Earth in 1864, have dreamed of the mystery beneath our feet. Henry Cavendish’s measurement of big G in 1798 suggested that Earth was not hollow, but dense and solid. Measurements by Lord Kelvin showed that the Earth becomes hotter the deeper you travel down along the geothermal gradient. The observation of molten magma and lava that bubbled up through volcanoes attested to an interior that was extremely hot and containing molten rock, that was driven by convection. But the structure of the interior of the Earth appeared to be something that could never be discerned. The deepest well ever drilled into the Earth was the Kola Superdeep Borehole, which goes down just over 12 kilometers beneath the Earth’s surface, only 0.2% of the distance to the Earth’s central core.

The woman who found another planet inside Earth
Inge Lehmann was an extremely shy student with a fondness for science. In 1893, a school was opened in Denmark near where Lehmann lived. The school was created by an ambitious woman named Hanna Adler, who had just returned from a trip to America with a new idea. Her school would be unique in the that “boys and girls will always be taught and brought up together.” Despite being a girl, Lehmann enjoyed an excellent education, and was able to attend college at the age of 18 at the University of Copenhagen, then transferred to the University of Cambridge in England to study physics and mathematics. It was an extremely intense study, and four years into her studies at the university, she was exhausted, burnt out and in poor health. She returned to Denmark and took a job to make ends meet. At thirty years of age, she decided to go back to school at the University of Copenhagen, with the dream of becoming a true scientist and teaching at a university. Her life-long dream was achieved in 1923, and she went on in 1928 to begin working with a team of scientists at the Geodetical Institute of Denmark. Lehmann was tasked with setting up seismological observatories across Denmark and Greenland. Seismometers were a new scientific instrument that measure the motion of the Earth. A seismometer is simply a heavy weight dangling above a fixed base which is firmly attached to the ground. During an earthquake, the fixed base moves with the shaking of the Earth, while the dangling heavy weight, due to inertia, does not. The motion of the base with respect to the dangling weight is transformed into an electrical voltage, which is recorded on paper with an inked needle. This squiggly line is proportional to the motion of the earth in respect to the dangling weight above it. Mathematically, the squiggly line is converted to a record of the absolute motion of the ground, and is used to record the intensity of Earthquakes, which produce seismic waves.

Seismic waves
Seismic waves are waves of energy that passes through solid rock resulting from earthquakes, explosions or other loud noises. Similar to sound waves, seismic waves are mostly compressional waves, where the wave is compressing the volume of the rock by alternating the compression and expansion of the rock within discrete frequencies. The same occurs with sound waves, which compress and expand the particles in the air (a gas) that allow you to hear sounds. Since these waves can pass through material blocked by light waves, they can image the inside of materials that are opaque to light waves. An example of this you might be more familiar with is in ultrasound, which uses a high frequency sound wave to send waves into the uterus of a pregnant mother, this allows the imaging of the growing fetus before birth inside a mother before the baby is born. It is also used in many other medical applications and does not require exposing the patient to radiation. The same tools can be used on a more global scale by geophysicists to image the interior of the Earth. This requires large events, such as massive Earthquakes or nuclear detonations to produce these seismic waves of energy, and seismographs are able to pick up these waves of energy scattered around the planet from monitoring stations that listen to the interior of the Earth. There are two types of compressional seismic body waves, the first one distorts the volume of the material, simply called primary waves (P-Waves), and the other that distort the shape of the material, called shear waves (S-Waves). P-Waves compress material parallel to the direction of travel, while S-Waves compress material perpendicular to the direction of travel. An analogy to think of is a row of rowdy boys in a tight line, when the boy at the end of the line pushes the boy in front of him, who then pushes the person in front of him, causing a wave to travel down the line, while the push also results in the boys to fall, or move in response. The energy of the initial push will travel the fastest, while the effect of this push, of the boys falling or stagger, will be slower. Thus P-Waves always travel faster than S-Waves, especially since P-Waves travel parallel to the direction of travel.

There is a third type of seismic wave associated with Earthquakes, called Surface Waves, that do not penetrate the Earth’s interior, and remain on the surface. They are the slowest type of seismic waves, but cause the most amount of damage to buildings and other structures during earthquakes. P-Waves, S-Waves and Surface Waves can be detected using a seismograph which measures the motion of the solid Earth below the device, which is fixed to the solid ground. P-Waves are the first waves to arrive during any event, and are quickly followed by S-Waves and then much later Surface Waves. Both P-Waves and S-Waves are called Body Waves, since they can move through the body or interior of the Earth. While surface waves only remain on the Surface of the Earth. The difference in time that it takes the P-Waves and S-Waves to arrive at a seismogram is known as the S-P interval; the S-P interval is important in detecting the location of Earthquakes. One critical aspect separates S-Waves from P-Waves: S-Waves cannot pass through liquids, they are absorbed by any liquid material that they encounter.

The Moho Discontinuity
One of the greatest insights about the nature of the interior of the Earth, came about with a massive earthquake that occurred on October 8th 1909 centered over the Kupa Valley in Croatia. A year before, at the Zagreb observatory in Croatia installed a new seismograph. With a massive Earthquake only 30 kilometers away, the readings on the seismograph revealed a clear signal to Andrija Mohorovičić, who maintained the scientific instrument at the observatory. He published a series of papers in 1910 noticing the difference in the arrival times of the P-Waves, which were faster than he had predicted based on mathematics. The short arrival time of the P-Waves appeared to be caused by the compressional seismic waves bouncing down into a material that facilitated a quicker travel time than expected if they travel through solid rocks. This lower material in the Earth appeared to have different physical properties that allowed seismic P-Waves to travel faster. Seismic waves travel at different speeds depending on the acoustic impedance of the material. Some materials facilitate a faster travel time of seismic waves than others. For example, a gelatinous substance of Jell-O, has a reduced acoustic impedance. If you place a loud speaker next to a bowl of Jell-O and blast music at it, the Jell-O will wiggle and jiggle as the soundwaves are converted to compressional P-Waves and S-Waves. While if you place a loud speaker next to a bowl of salt and blast music at it, the salt would barely budge. Salt has a higher acoustic impedance than Jell-O. Mohorovičić postulated that there was a Jell-O like layer beneath the Earth that allowed the P-Waves to travel faster at deeper depths in the Earth. This idea was formed with the recent realization of a surface layer called the crust and a deeper mantle layer from the German word for coat. Mohorovičić envisioned a double layer, something like peanut brittle (the Crust of the Earth) on top of Jell-O (the Mantle of the Earth). Mohorovičić advocated for a boundary layer known today as the Moho Discontinuity, which separates the upper crust from the lower mantle, between depths of 5 to 90 kilometers, which actually varies considerably over the sub-surface of the Earth. The mantle can be viewed as a material of dough-like ductile solids that facilitates easy deformation, when compared to the solid brittle crust of the Earth’s near surface, where rocks break into jagged pieces. Earthquakes are limited to depths above the Moho discontinuity, since the ductile mantle below does not break under stress, but plastically deforms. The Moho discontinuity is closely associated with the Brittle‐Ductile Transition Depth, the depth at which the material below is ductile, like bread-dough.

A Liquid Core and the S-Wave Shadow
In 1908, Karl Zoeppritz, a brilliant early seismologist at the University of Göttingen in Germany died, leaving behind his unpublished notes. These notes were passed by his supervisor at the University, Emil Wiechert, then to Wiechert’s student Beno Gutenberg. Gutenberg was interested in using the new seismographs to measure tiny motions within the Earth, such as those caused by the motion of crashing waves at the beach, but the notes left behind by Zoeppritz contained the motions caused by far away earthquakes, such as the 1906 Earthquake in San Francisco. For his thesis research Gutenberg compiled large sets of data from an ever-expanding number of seismographs, observing discontinuities in the subsurface. His advisor argued that the core of the Earth must be made of iron, although the nature of the core was a mystery. Gutenberg figured that he could solve its mystery with his large sets of data. In 1913, Gutenberg reported on the absence of the S-Waves from earthquakes that originated on the other side of the earth from the seismograph. This S-Wave shadow appeared to be caused by the absorption of S-Waves in the core of the Earth because it was liquid. Gutenberg set about determining the depth of this lower mantle/core boundary, which today is placed at a depth of 2,891 km. The molten iron core, was a liquid, while the ductile mantle above was a solid. Gutenberg was just getting started with his research on the interior structure of the Earth, when he was drafted into the German army at the outbreak of World War I. Less than a year into his research, in August of 1914 he was an infantryman in the trenches on the western front, his experience was put to action by the army by measuring the travel times of enemy cannons to determine their position. He nearly dogged death when a grenade nearly killed him with shrapnel. After the war, although celebrated for his discovery of a liquid core, there was no work for him as a scientist. He returned home, and took over the soap factory that his father ran. His research was reduced to evenings and weekends, as the soap factory provided an income to his family in post-war Germany in the 1920s. It was during this time that Lehmann visited him, to learn what she could from the war-veteran about how to read seismographs. It must have been exciting to have a colleague interested in his research and to value his contributions toward the study of the interior of the Earth. Lehmann learned much from him about the liquid molten iron core that he had proposed in 1913. During the 1920s and into the 1930s, Lehmann studied the signals transmitted through the Earth’s core. She copied the recorded arrival times of P Waves from Earthquakes from all around the world onto index cards which she filed in oatmeal boxes. Using these records, she postulated that some of the P-Waves passed through the core of the Earth and bent, forming what she called P′ waves, as she summarized in her paper: Seismic waves that travel through the Earth’s mantle and crust only are represented by P, while P′ represents P-waves that pass through the mantle into the core, and then pass through the mantle again. Both P′-Waves and P-Waves exhibit a shadow ringed zone between 112.5 degrees and 153.9 degrees where no evidence of arrival times was detected in this area of the Earth. Inside this ringed zone, there was only P′-Waves, waves that traveled through the core of the Earth, these would slow as they passed through the liquid core from 10 km/sec to 8 km/sec. In the subset of data in this ringed zone, she noticed that arrival times suggested some P′-Waves were slightly faster than expected, like they traveled through a solid, while others were slower. She also noticed that some of these P′-Waves could be observed faintly in the shadow zone, as if they bounced off some solid inner core. These waves she called P′2-Waves (today they are called PKiKP-Waves) and they both reveal a solid inner core inside the Earth. Her research was published in 1936, with the shortest title of any scientific paper, P'. She had discovered a planet inside the molten iron liquid core of the Earth, what is known as the solid inner core. Her paper did not need to be verbose. This inner core has a radius of about 1,220 kilometers, about the size of Pluto. It rotates in an orbit within a liquid outer core of molten sulfur, iron and nickel at the center of the Earth. Much of the variability of Earth’s magnetic field is a result of this motion between the inner and outer core of the Earth, which is known as the Earth’s dynamo. Inge Lehmann had found a planet deep inside the Earth.

The complexity of Earth’s Interior
Since the pioneering work of Lehmann, Gutenberg and Mohorovičić, other discontinuities have been found using seismic waves produced by earthquakes to image the inside of the Earth. The Moho (short for Mohorovičić) Seismic Discontinuity separates the brittle Crust from the ductile Mantle, the Gutenberg Seismic Discontinuity separates the ductile Mantle from the liquid molten Outer Core, while the Lehmann Seismic Discontinuity separates the liquid molten Outer Core from the solid Inner Core. However, there are several other seismic discontinuities that have been observed in the Mantle. In the upper mantle (100 to 250 kilometers depth) seismic waves are slower than the lower mantle and the S-Waves appear weakened when traveling through this low velocity zone. While the faster seismic waves in the lower mantle are likely a result of increasing pressure and density of rocks below, the weakened S-Waves indicate that this zone of the upper mantle is partially composed of molten liquid rocks; a weak mushy soft layer compared to the harder more rigid lower mantle below. This layer in the upper mantle is known as the Asthenosphere, “the weak sphere,” which is capped by the Lithosphere, “the rock sphere,” which includes the crust, and some portions of the uppermost mantle. The tectonic plates that move continents are lithospheric plates, which ride over the asthenosphere, driven by convection of liquid magma and other molten rocks in the upper mantle. The asthenosphere, is not a liquid, but likely a ductile solid with many chambers of large regions of liquid magma deep under the Earth’s surface. The asthenosphere plays an important role in mountain building, the distribution of volcanoes on Earth, and the break-up and movement of tectonic plates. Deeper in the mantle are two other discontinuities that are described by their depth. The 410-kilometer seismic discontinuity appears to be caused by a phase transition in the crystalline structure of the rock to become more densely packed at these high pressures, while the 680 seismic discontinuity (sometimes referenced to depths of 660 or 670 km) is believed to be another phase transition of the minerals in the rock. The 680 seismic discontinuity is often used to distinguish the upper mantle from the lower mantle. The velocity of seismic waves increases across these boundary zones, when they increase their speed through the more densely pack crystalline rocks at these lower depths.

Shallow Seismic Waves
In 1976, Andy Hildebrand was hired by Exxon in Houston, Texas, to use seismic waves to image the subsurface along the north shore of Alaska in the pursuit of oil. Exxon would drive large thumper trucks that would send seismic waves through the ground, which were recorded by geophones (a type of seismography), hoping to image the underground region in the search for oil. Hildebrand, as an electrical engineer spent his time developing a new tool that tuned those seismic waves using different frequencies. This tuning resulted in better resolution to the images of the shallow subsurface of the Earth. These were shallow images allowing geologists to virtually see underneath the Earth about 5 kilometers down into the crust, and made the company an enormous fortune, when they found oil using them. With his retirement in 1989, Hildebrand set about to pursue his true passion; playing the flute. He took classes and majored in music as he pursued a second career in the music industry, but he was a still a scientist at heart. The same technology that could image the inside of the Earth, could be used to auto-tune musical notes. In 1997 he introduced software designed to tune the pitch of musical notes and people’s voices. This became known as Auto-Tune, which was first used on Cher’s Believe album in 1998. Today, Auto-Tune can turn any speaking voice into a song, used by the Rapper T-Pain, to the Gregory Brothers on their YouTube channel Schmoyoho to John D. Boswell on his YouTube channel Symphony of Science, it illustrates the strange way science in one field can lead to innovations in another.

Gravity Anomalies
In 1671, the French astronomer named Jean Richer observed that a pendulum swung in French Guyana near the equator recorded less swings in a day than the same pendulum swung back home in France. This suggested that the gravity of the Earth (g) was slightly greater near the equator in French Guyana due to a greater distance from the center of the Earth, than back in Paris, France. There is more mass beneath French Guyana, then under Paris; in other words, there is a greater distance between French Guyana and Earth’s center than between Paris and Earth’s center. This was evidence that the Earth was not a perfect sphere in shape, but was wider and budged around the equator, in a spheroid shape. The experiment sparks much interest in the study of the geodetic shape of Earth, because this budge at the equator would have great effect on navigation and map making.

In 1735, the French Academy of Sciences embarked on an expedition to Ecuador to carry out experiments to verify this experiment and carry out other experiments near the equator. Pierre Bouguer, was selected for the trip, as well as other French and Spanish scientists of the day. Bouguer was already a celebrated genius, who began teaching naval navigation and ship building at the age of only 16. The team sailed across the Atlantic Ocean arriving at Panama, and crossed the Isthmus of Panama by land, and then ferried down the coast of South America to Ecuador which was under Spanish control as the Real Audiencia of Quito. It was an exotic place to carry out experiments, but the team set to work, much of their knowledge left a lasting expression on the town of Quito, which today maintains the oldest South American Astronomical Observatory. For Bouguer, the expedition would last ten years before he returned to France, and wrote of his experience in a book entitled La figure de la terre (The Shape of the Earth) published in 1746. While in Quito, Bouguer measured the number of pendulum swings during the sidereal day, which as predicted swung slower, proving that the Earth did in fact bulge at the equator slightly. To verify these results, Bouguer decided to repeat the experiment by climbing to higher altitudes on the peaks of the nearby mountains of Pichincha and Chimborazo. Bouguer reasoned that these higher mountains would slow the pendulum down even more, as they added additional mass between him and the center of the Earth. He predicted that the pendulum on top of the highest peak, Pichincha, would slow down by 0.15%. In August of 1737 the team climbed to the top of Pichincha and attempted to measure a swinging pendulum. The wind howled and it rained upon the rocky peak, as the group did their best to count the swings of the pendulum. They observed that the pendulum slowed down by a factor of 0.12%, close to the predicted value. Bouguer demonstrated that the higher your altitude or elevation on land the greater the force of gravity will be due to the increase in mass because of the higher topography below you, something known as the Bouguer Gravity Anomaly. However, there was something odd, in that the pendulum slowed down less than predicted. Bouguer surmised that the interior of the Earth was not uniformly dense, and that the least dense rocks were the ones directly below the mountain. Rocks become denser as they get closer to the center of the Earth and were subjected to more and more pressure, so the rocks near the surface and directly below the mountain were less dense. This led to the discrepancy of 0.03%. Bouguer had discovered a way to measure the Earth’s interior density using gravity anomalies.

Gravimeters
Gravity anomalies allow scientists to see into the interior of the Earth by measuring the density of the solid Earth below each point on the surface. Early gravimeters were developed to measure the gravity over large areas using the length of displacement of a weight held freely by a spring. If gravity was stronger, the weight was pulled lower and closer to the Earth. Often the gravimeter was corrected by measurements from barometers to remove the effect of topography (the Bouguer Gravity Anomaly), as gravity increases with elevation.

Imagine that you are measuring gravity using a simple gravimeter on a flat surface of ground. If you pass over underground features with lower density (say a cave), the gravitational field will be slightly less, while if you pass over an underground feature with higher density (say a thick vein of gold), the gravitational field will be slightly more. Superconducting gravimeters have recently been developed that can detect minute changes in the surface gravity, which due to their size are fixed. They record the daily Earth tides caused by the pull of the moon, which stretches the interior of the Earth, making it less dense when the moon is directly overhead or directly opposite the station, and denser when the moon is at the perpendicular axis. These Earth tides also have to be corrected for in the data to be able to record gravitational changes at each station due to subsurface features. However, less sensitive spring-based gravimeters can measure large regions, sometimes even by flying over an area in an airplane, and recording the signal from the air. New technologies have allowed gravity anomalies to be measured from outer space on board orbiting satellites above Earth, such as the twinned satellites of the United States and Germany; GRACE (Gravity Recovery and Climate Experiment), which measured Earth’s global gravity anomalies between 2002 to 2017, including recording the dramatic melt of Greenland’s ice sheets during that span of time. Gravity anomalies (corrected from the Bouguer anomaly due to topography) are mapped using different colors to highlight the density of the Earth below each location, revealing pockets of Earth’s surface which are above denser rocks. With seismic measured depths to the Moho discontinuity (ranging from 10 to 90 kilometers), gravity anomalies are found to be high over regions with shallow depths to the Moho (10 to 20 kilometers), and low gravity anomalies over regions that exhibit deeper depths to the Moho (greater than 20 kilometers). Rock layers below the Moho Discontinuity are denser. If the crust is thin, there will be more of these dense layers below the region, while a thicker layer of crust will result in less dense layers below the surface. If the topography is the same, a thinner crust will result in greater gravity. Mapped gravity anomalies across the state of Utah reveals a pattern, in which Western Utah and the Great Basin overlays a thin crust (with higher gravity), while Eastern Utah and the Colorado Plateau and Uinta Mountains overlays thicker crust (with lower gravity). Thinner crusts are more susceptible to earthquakes and volcanoes, but are also found beneath the ocean basin, which exhibit the thinnest crust and shallowest Moho discontinuities on Earth’s surface; they are also some of the densest rocks. Thus, the Earth’s crust can be divided into the thin crust under the ocean basins, and the thicker crust under the continents. Ocean crust and continental crust are physically and chemically very different.

Gravity anomalies are frequently utilized by precious metal prospectors, since they can reveal regions where the denser rocks of the mantle have reached the Earth’s surface, resulting in siderophile elements like gold, iron, and nickel being more prevalent in these areas.

Isostasy and Isostatic Rebound
Seismic and gravity anomalies reveal a variably thick crust which extends over the entire surface of Earth. In some places, like ocean basins, the crust is thin, with a shallow Moho discontinuity, while over continents the crust is thicker, with a deeper Moho discontinuity. The thickest crusts are often found below high mountain ranges, while the thinnest are found in mid-ocean ridges. Mid-Ocean Ridges are extremely long ridges that form deep under the ocean and rise above the sea floor; here the Moho discontinuity is almost at the surface. The crust and uppermost layers of the mantle form the brittle zone called the lithosphere, beneath the lithosphere is the mushy doughy soft layer called the asthenosphere, which is much denser than the lithosphere. In a sense, the lithosphere floats upon of this weaker and softer asthenosphere layer. The asthenosphere is soft enough it can convect heat from the Earth’s interior by the very slow motion of this material. One simple analogy, is to imagine that the lithosphere is wood that floats on denser water, with water representing the asthenosphere. If the wood is thick, it will be more buoyant and will float higher above the water, while if the wood is thin, it will be less buoyant and will float lower in the water. This buoyancy of the lithosphere on top of the asthenosphere is called Isostasy. This explains why the crust (and hence the lithosphere) is thicker in regions with mountains, because the mountains are supported by a deeper root of lighter crust, and are held up by this thicker layer of crust. Now imagine that the wood is slowly whittled away by the process of erosion over millions of years from the top surface. The weight of the wood will decrease, but since it has a deeper root, its buoyancy will cause it to rise, this is called Isostatic Rebound. Even as the mountain is eroding, it is continually rising because of this isostatic rebound. Another example of isostatic rebound is when large ice sheets melt, taking weight off the lithosphere, which responds by rising the topography upward. This uplift can significantly change the landscape, although the process is slow. Often near hogbacks, piedmonts and valleys on the edge of mountain ranges, rivers will incise deep canyons, as the mountain range rise while the rivers and erosion work to cut down into the margins of these mountain ranges. One of the best examples of this is the Royal Gorge in Canon City, Colorado, but many other examples exist where steep canyons and gorges have formed on the margins of mountain ranges, due to the continued uplift of the mountains because of isostatic rebound. If the mountain range continues to rise, and continues to be eroded, the thicker crust below the region will not be enough to support the region’s higher topography, and will result in the mountain range to begin to sink and collapse.

One of the more dramatic examples of this can be found in Utah in Brown’s Park, where the eastern range of the Uinta Mountains sank, forming a wide valley, in which the Green River passes through today, but in the past this region of Utah was topographically very high in elevation. Seismic and gravity surveys reveal that the crust is particularly thin here, and was unable to support a tall mountain range in this area, and hence resulted in a sinking broad valley, once the mountain was fully eroded down. Isostasy became a powerful way to explain the rise and fall of mountains. For decades geologist believed that mountains were the product of thickening and thinning crust, and the buoyancy of the lithosphere above a weak soft asthenosphere. Continents did not move. One scientist argued that they did move, his name was Alfred Wegener, and although he was not a geologist, his crazy idea would lead to a revolutionary idea that would transform the field of Earth Science, and led to the theory of plate tectonics.