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Herausgeber: John Wiley & Sons
Kategorie: Wissenschaft und neue Technologien
Serie: IEEE/OUP Series on Electromagnetic Wave Theory (formerly IEEE only), Series Editor: Donald G. Dudley.
Sprache: Englisch

Beschreibung

This book covers the study of electromagnetic wave theory and describes how electromagnetic technologies affect our daily lives.

From ER to ET: How Electromagnetic Technologies Are Changing Our Lives explores electromagnetic wave theory including its founders, scientific underpinnings, ethical issues, and applications through history. Utilizing a format of short essays, this book explains in a balanced, and direct style how electromagnetic technologies are changing the world we live in and the future they may create for us. Quizzes at the end of each chapter provide the reader with a deeper understanding of the material. This book is a valuable resource for microwave engineers of varying levels of experience, and for instructors to motivate their students and add depth to their assignments. In addition, this book:

Presents topics that investigate all aspects of electromagnetic technology throughout history
Explores societal and global issues that relate to the field of electrical engineering (emphasized in current ABET accreditation criteria)
Includes quizzes relevant to every essay and answers which explain technical perspectives

Rajeev Bansal, PhD, is a professor of Electrical and Computer Engineering at the University of Connecticut. He is a member of IEEE and the Connecticut Academy of Science and Engineering. He is a Fellow of the Electromagnetics Academy. His editing credits include Fundamentals of Engineering Electromagnetics and Engineering Electromagnetics: Applications. Dr. Bansal contributes regular columns to IEEE Antennas and Propagation Magazine and IEEE Microwave Magazine.

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Leseprobe

FROM ER TO E.T.

How Electromagnetic Technologies Are Changing Our Lives

RAJEEV BANSAL

The IEEE Press Series on Electromagnetic Wave TheoryAndreas C. Cangellaris, Series Editor

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.

For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com.

Library of Congress Cataloging-in-Publication Data is available.

ISBN: 978-1-118-45817-4

About The Author

Preface

Acknowledgments

Chapter 1: On The Shoulders of Giants

1.1 HE(A)DY Stuff

Notes

1.2 From Russia Without English

Acknowledgment

References

1.3 On The Shoulders Of Giants

Note

1.4 Do-It-Yourself Execution?

Reference

Notes

1.5 Franklin: Did He or Didn't He?

References

Notes

1.6 De Magnete (“On the Magnet”)

References

Notes

1.7 A Eureka Moment

References

Note

1.8 Auld Lang Syne

Acknowledgment

References

Notes

1.9 As Singular as a Delta Function?

References

Note

1.10 Publish or Perish?

References

Did You Know?

Answers

References

Chapter 2: The Earth and Beyond

2.1 In The Eye of The Beholder

References

Notes

2.2 Roses are Red, Violets Are Blue…

References

Note

2.3 2003: An Earth Odyssey?

References

Note

2.4 Which Came First: Big Bang or Big Crunch?

Sources

Note

2.5 Whistling in The Dark?

References

Notes

2.6 Going Beyond a Selfie

References

Notes

Did You Know?

Answers

Chapter 3: Search for Extraterrestrial Intelligence (SETI)

3.1 Little Green Men: A Phantom Menace?

Sources

Notes

3.2 Waiting for Godot?

References

Note

3.3 Is There Anybody There?

References

Note

3.4 Science or Science Fiction?

References

Note

Did You Know?

Answers

Chapter 4: Professionalism: Ethics and Law

4.1 Did Maxwell Pull a Fast One?

References

Notes

4.2 Cell Phones and Cancer: Anatomy of a Legal Opinion

Sources

Notes

4.3 Happy 200th Anniversary!

References

4.4 Einstein Doesn'T Work Here Anymore

Sources

Note

4.5 It is a Bird. It is a Plane. It is …

References

Note

Did You Know?

Answers

Chapter 5: Health Effects of Electromagnetic Fields

5.1 Say Au Revoir to Cell Phones?

References

Notes

5.2 Electromagnetic Hypersensitivity

References

Note

5.3 From Bell Tower to Cell Tower

References

Notes

5.4 Nocebo: Reading This Column may Affect Your Health

References

Notes

5.5 Magnetic Pull: Biological Effects or Medical Applications?

References

Notes

5.6 Close Encounters With Radiation of the Other Kind

References

Notes

Did You Know?

Answers

Chapter 6: Biomedical Applications

6.1 How Many Biologists Does it Take to Fix a Radio?

References

Note

6.2 The Grand Challenges

References

Note

6.3 Biomedical Applications: Taking Stock

References

Note

6.4 Tugging at the Heartstrings

References

Note

6.5 A Jolt from the Blue?

References

Note

6.6 Channeling the Voice Within

References

Note

6.7 Battling Cancer: Microwave Hyperthermia

References

Note

Did You Know?

Answers

Chapter 7: Defense Applications

7.1 Where is Waldo?

References

Note

7.2 ANTIMAGNET

References

Notes

7.3 Cutting to The Chase

References

Notes

7.4 Twenty-First Century Warfare

References

7.5 On A Wing And A Prayer

References

Note

7.6 ELF Communication: An Obituary

References

Notes

7.7 Catching Up With Professor Scarry

References

Note

7.8 Criminal Interference

References

Notes

7.9 Wireless Networks: An Electronic Battlefield?

References

Notes

Did You Know?

Answers

Chapter 8: Domestic And Industrial Applications

8.1 Blowin' In The Wind

References

Notes

8.2 Sharing The Road

References

Notes

8.3 Rare No More?

References

Notes

8.4 Local Heating?

References

Note

8.5 Coming Soon to a Wal-Mart Near You

References

Notes

8.6 Has Your Cat Gone Phishing?

References

Notes

8.7 The Future of Wireless Charging

References

8.8 Electropollution or Sustainable Energy?

References

Note

Did You Know?

Answers

Chapter 9: Communication Systems

9.1 Small is Beautiful

References

Notes

9.2 Gigabit Wi-Fi

References

Note

9.3 Open Spectrum: A Tragedy of the Commons?

References

Notes

9.4 Near-Field Communication

References

Notes

9.5 A New Digital Phone?

References

Note

9.6 Electronic Countermeasures

References

Note

Did You Know?

Answers

Chapter 10: Lifelong Learning

10.1 Back to Basics

References

Notes

10.2 Preaching to the Choir?

References

Note

10.3 The Other Davos?

References

Note

10.4 Mirror, Mirror on the Wall; who is the Fairest of Them All?

References

Notes

10.5 Equations Redux

References

Note

10.6 New Year's

Resolutions

Laws

References

Note

10.7 Through a Glass Darkly

References

Note

10.8 Stranger Than Fiction?

References

Note

10.9 High Frequency Education: What Do You Think?

References

Afterword

Index

IEEE Press Series On Electromagnetic Wave Theory

EULA

Guide

Cover

Table of Contents

Preface

Pages

xii

113

137

157

175

195

197

209

About The Author

Rajeev Bansal received his Ph.D. in Applied Physics from Harvard University in 1981. Since then he has taught and conducted research in the area of applied electromagnetics at the University of Connecticut where he is currently a Professor (1992–) and Head (2009-) of the Department of Electrical & Computer Engineering (ECE). His technical contributions include three edited books [Fundamentals of Engineering Electromagnetics (2006), Engineering Electromagnetics: Applications (2006), Handbook of Engineering Electromagnetics (2004)], two commercialized patents (1989 and 1993), and more than 100 journal/conference papers/book chapters. Dr. Bansal has served as an Editor/Reviewer of Journal of Electromagnetic Waves and Applications as well as an Associate Editor of Radio Science. He has also served on the editorial advisory boards of IETE Technical Review and the International Journal of RF & Microwave CAE. He is a columnist for the IEEE Antennas and Propagation Magazine (1987–) and the IEEE Microwave Magazine (since its inception in 2000). He is a fellow of the Electromagnetics Academy, an elected member of the Connecticut Academy of Science and Engineering (CASE), and a senior member of the IEEE. He has served as a consultant to the Naval Undersea Warfare Center, Newport, RI.

Preface

Electromagnetic technologies have seeped into every corner of our lives. From that cup of coffee one reheats in the microwave oven to the cellular wireless network that lets one download an ebook in a jiffy, we depend on the marvels of these technologies every day. There are times when we wonder if our privacy is going to be made obsolete one day by RFID chips; others when we worry about the safety of all this radiation around us. Love it or hate it, one cannot get away from these electromagnetic technologies.

In this book, I have tried to showcase many of these wonderful electromagnetic technologies that are changing the world we live in (e.g., new medical devices for the ER) and the future they may create for us (e.g., making contact with E.T. some day). The book owes its genesis to the regular columns for the IEEE Antennas and Propagation Magazine and the IEEE Microwave Magazine that I have been writing for many years. Based on the comments I have received, the columns have been enjoyed by science/engineering students, practicing engineers, academic colleagues, and many members of the general public with an interest in technology. In planning the book, I had two goals in mind:

Preserve the original math-free style of the original columns to make the material accessible to the broadest possible audience and

Create a handy textbook

supplement

for students and instructors in courses on electromagnetics (and related fields) by arranging the material in a framework that includes additional technical details and links to electromagnetic textbooks.

With respect to the second goal, it may be noted in passing that the current accreditation criteria for electrical engineering programs emphasize that students, in addition to mastering the technical content, become conversant with the societal and ethical implications of technologies and learn to place the engineering subject matter in the broader global context. This small book goes some distance in filling that niche in a student's technical education. Depending on the topic, the tone of each essay varies but, in my opinion, the material is presented always in a readily accessible and succinct style so that it can be read quickly in a classroom and discussed without having to take too much time away from the technical material being covered in the class. (I have used this approach with some of these essays myself in courses ranging from a freshmen class open to non-engineers to junior/senior level EM/microwaves courses.) Another goal is to entice the reader into pursuing the sources for the essay to delve more deeply into the subject (life-long learning). The sources are always listed in each short piece and most of them are available online for instant access.

The main technical entries in the book are grouped by broad areas of application/interest and, in the spirit of Monty Python's “And Now for Something Completely Different,” are interspersed with amusing tidbits in the form of “quizzes” and essays on far-out topics. I hope you will have as much fun reading them as I had in compiling them.

Acknowledgments

I would like to thank the editors-in-chief Ross Stone (through 2014) and Mahta Moghaddam of the IEEE Antennas and Propagation Magazine (where most of the columns originally appeared) and the editors of the IEEE Microwave Magazine for their support over the years. I am also thankful to Taisuke Soda, the then acquisitions editor for Wiley/IEEE, as well as the reviewers of the book proposal and a draft of the manuscript for their many helpful suggestions. I appreciate greatly the support of the current Wiley/IEEE editor Mary Hatcher, who kindly extended the deadline to complete this book when my additional short-term professional responsibilities forced a 2-year delay in the project. She also helped me find an online resource (Pixabay) for the images used in this book. Finally, I would like to express my deep gratitude to my family, without whose encouragement the book would have remained a gleam in the eye.

Rajeev Bansal

Chapter 1On The Shoulders of Giants

“If I have seen further it is by standing on the shoulders of giants.”

—Isaac Newton (1642–1727)

1.1 HE(A)DY Stuff

Hedy Lamarr (1914–2000), a celebrated movie actress from the Golden Age of Hollywood, once said, “Any girl can be glamorous. All she has to do is stand still and look stupid.'' Well, the very same Lamarr, in her spare time, co-invented—yes, I'm not kidding—a frequency-hopping radio-controlled system for guiding torpedoes. For her invention, US Patent #2,292,387, granted in 1942, Hedy Lamarr finally received some long-overdue recognition. On March 12, 1997, at a San Francisco ceremony, her son accepted the Electronic Frontier Foundation Award, given to “Hedy Lamarr for her Contribution in Pioneering Electronics.”

This bizarre sequence of events had its roots in pre-war Vienna, where, in 1933, the Austrian-born Hedy Lamarr married Fritz Mandl, a leading Austrian armaments manufacturer. Mandl's household was an institution in the Viennese society, attracting many dignitaries, including political and military leaders. Mandl was himself interested in control systems, and engaged in research in that field. Apparently, Hedy Lamarr also picked up a thing or two along the way. In 1937, their marriage broke up, and Lamarr emigrated to America and headed for Hollywood.

One day, in the summer of 1940, Hedy Lamarr and her Hollywood neighbor, George Antheil, an avant-garde composer, were playing the piano together, carrying on an improvised musical dialogue up and down the keyboard. They started talking about the war and Lamarr brought up the idea of frequency hopping, synchronized between the transmitter and the receiver, for secure (resistant to jamming) radio control of torpedoes. Antheil, drawing upon his experience with player pianos, suggested that the synchronized rapid frequency hopping that Lamarr had envisioned for the torpedo-control system could be implemented using perforated paper rolls, similar to player-piano rolls. In fact, by the time they applied for a patent in June 1941, their embodiment of the frequency-hopping technique used slotted paper rolls and utilized 88 frequencies, the exact number of keys on a piano. Their patent application also specified that the torpedo could be guided from above by a plane.

While their invention was granted a patent in 1942, it was an entirely different ball game when it came to convincing the US Navy that the device was practical for torpedo control. Ironically, Antheil's contribution of the player-piano mechanism as one possible implementation of Lamarr's frequency-hopping system apparently proved to be its undoing. Antheil later wrote, “In our patent Hedy and I attempted to better elucidate our mechanism by explaining that certain parts of it worked like the fundamental mechanism of a player piano. Here, undoubtedly, we made our mistake. The reverend and brass-headed gentlemen in Washington who examined our invention read no further than the words “player piano.” “My God,” I can see them saying, “we shall put a player piano in a torpedo.” Amusing as Antheil's explanation is, it probably does not tell the whole story.

The Navy must have also realized the difficulties in setting up an electromagnetic communication link between a plane and a torpedo through the highly attenuating sea water (a problem that persists to this day) and, in particular, in equipping the torpedo with a suitable receiving antenna.

At any rate, discouraged by the Navy's attitude, Lamarr and Antheil did not pursue their invention further. Instead, Lamarr successfully used her charm to sell war bonds, raising millions of dollars for the war effort. In 1957, engineers at Sylvania Electronic Systems Division in Buffalo, New York, implemented secure radio communication via frequency hopping by replacing the piano rolls with electronic circuits. In 1962, 3 years after the Lamarr–Antheil patent had expired, ships equipped with secure military-communication systems, based on the frequency-hopping technique, were deployed during the Cuban missile crisis. Though Lamarr and Antheil never collected a penny from their pioneering work, their patent has been cited as the seminal work by subsequent patents in the area of frequency-hopping systems.

The bottom line is that Lamarr and Antheil were inventors ahead of their time. That is why it is particularly fitting that the 1997 Electronic Frontier Foundation Award finally recognized the vital role their patent eventually played in the modem development of secure communications.

[Compiled from reports in the Chicago Tribune, March 31, 1997, and the American Heritage of Invention & Technology, Spring 1997.]

(The original version of the column appeared in “AP-S turnstile,” IEEE Antennas and Propagation Magazine, vol. 39, no. 3, p. 100, June 1997.)

Notes

1. Many books are available about Hedy Lamarr and her inventions. See, for example, Richard Rhodes's

Hedy's Folly: The Life and Breakthrough Inventions of Hedy Lamarr, the Most Beautiful Woman in the World

, Vintage, 2012.

2. For more information about US Patent #2,292,387, consult:

http://www.google.com/patents/US2292387

(accessed December 22, 2015).

1.2 From Russia Without English

The National Academy of Sciences recently published a biographical memoir [1] of Edward Leonard Ginzton (1915–1998). Ginzton's fundamental contributions to electronics and microwaves have been eulogized before, for example, when he was elected to the National Academy of Engineering (1965), or when he received the IEEE Medal of honor (1969). What Anthony Siegman, the author of this brief 35 page memoir, succeeds in doing is to present a multi-faceted portrait of Ginzton, who in Carolyn Caddes's words was “scientist, educator, business executive, environmentalist, and humanitarian [2].” Here are some highlights from Siegman's memoir.

Early Years

Ginzton, who was born in Ukraine, recalls his childhood education thus: “Since both of my parents participated as medical officers on the Eastern Front, my early childhood consisted of rapid migration with the tides of war, revolution, and other similar events. Until I was 8 we did not live in any one place for more than six months, and I was not exposed to formal education until I was 11.” When Ginzton was 13, his family emigrated from Russian-controlled Manchuria to San Francisco. Ginzton, “knowing not a word of English,” was placed in the first grade in the public schools. Four years later, Ginzton finished high school and entered UC Berkeley.

The War Years

As Ginzton later noted modestly: “[During these] six years, I invented some 40 or 50 devices, some of which were relatively important.” The Doppler radar techniques pioneered under Ginzton's supervision at Sperry provided the technical foundation of many sophisticated radars of later years. By the time the war ended, Ginzton had some 2000 people working under his direction.

The Stanford Years

Appointed an assistant professor of applied physics (rather than physics because of his EE credentials) at Stanford, Ginzton and his colleagues published “A Linear Electron Accelerator” in the February 1948 issue of the Review of Scientific Instruments, which led to the successful development of several generations of accelerators, the use of which was instrumental in at least six Nobel Prizes. Ginzton was also prescient in recognizing the potential application of these accelerators for radiation therapy for cancer; by the time of his death some 4000 of small medical accelerators were treating over 1 million patients annually.

The Varian Years

Varian Associates was established in 1948 with $22,000 of capital and six full-time employees. Ginzton was on the company's board from day one and remained on it till 1993. In 1959, when Russell Varian died suddenly, Ginzton was appointed CEO.

The McCarthy Era

Ginzton, who had shared a graduate-student office with Frank Oppenheimer (Robert's brother) in 1939, was caught up in the McCarthy maelstrom and lost his security clearance for a while. It required a massive legal effort by Stanford to get Ginzton's clearance back.

Community Leadership

Ginzton was an early champion of fair housing and clean air. He also founded and co-chaired (1968–1972) the Stanford Mid-Peninsula Urban Coalition, an organization to support the launch of minority-owned small businesses.

His Vision

Writing in 1956, Ginzton noted: “It is evident that the applications of present microwave knowledge will continue to grow, both in number and diversity; but despite the daily invention of novel applications, we must not become complacent. Every field of research has a finite half-life.” Later in his life, he explained his philosophy to Caddes [2]: “Grow and become educated, but do not equate professional training with education. Try to learn how to think. Attempt to do what you want to do. Making a living is not enough.”

Acknowledgment

I would like to thank my colleague Dr. Anthony DeMaria for bringing the Ginzton memoir to my attention.

References

A. E. Siegman, “Edward Leonard Ginzton (1915–1998),”

Biographical Memoirs

, vol. 88, National Academy of Sciences, Washington, D.C., 2006.

C. Caddes,

Portraits of Success: Impressions of Silicon Valley Pioneers

, Tioga, Palo Alto, CA, 1986.

(The original version of the column appeared in “Microwave surfing,” IEEE Microwave Magazine, vol. 7, no. 6, pp. 28–30, December 2006.)

1.3 On The Shoulders Of Giants

We know Maxwell's equations by heart but what do we know about Maxwell himself? Considering his preeminent position in the pantheon of leading scientists, there are relatively few biographies of Maxwell. The primary historical reference on Maxwell has been the 1882 biography written by Maxwell's long-time friend Lewis Campbell with help from William Garnett. Campbell's work received critical acclaim upon publication. “This volume will be heartily welcomed by all who knew Clerk Maxwell, and who cherish his memory, and lay the still wider circle of those who derive pleasure and new vigour from the study of the lives and work of the great men that have gone before them,” noted the reviewer in Nature but it is no longer readily available. Fortunately, the full text of the 1882 biography is available on the web at https://www.sonnetsoftware.com/resources/maxwell-bio.html

Campbell's book, The Life of James Clerk Maxwell, has three parts: (1) a description of Maxwell's life, (2) an account of his scientific investigations, and (yes, I am not kidding) (3) a collection of Maxwell's poetry. Maxwell's poems cover the full spectrum from translations of Virgil's poetry to original poems on scientific issues. An example of the latter follows (I have omitted the middle section of the rather long poem as well as the accompanying figure and equations, which may be viewed at the website mentioned above):

A PROBLEM IN DYNAMICS (1854)

AN inextensible heavy chain

Lies on a smooth horizontal plane,

An impulsive force is applied at A,

Required the initial motion of K.

Let ds be the infinitesimal link,

Of which for the present we've only to think;

Let T be the tension, and T + dT

The same for the end that is nearest to B.

Let a be put, by a common convention,

For the angle at M 'twixt OX and the tension;

Let Vt and Vn be ds's velocities,

Of which Vt along and Vn across it is;

Then Vn/Vt the tangent will equal,

Of the angle of starting worked out in the sequel.

In working the problem the first thing of course is

To equate the impressed and effectual forces.

K is tugged by two tensions, whose difference dT

(1) Must equal the element's mass into Vt.

Vn must be due to the force perpendicular

To ds's direction, which shows the particular

Advantage of using da to serve at your

Pleasure to estimate ds's curvature.

For Vn into mass of a unit of chain

(2) Must equal the curvature into the strain.

Thus managing cause and effect to discriminate,

The student must fruitlessly try to eliminate,

And painfully learn, that in order to do it, he

Must find the Equation of Continuity.

…

From these two conditions we get three equations,

Which serve to determine the proper relations

Between the first impulse and each coefficient

In the form for the tension, and this is sufficient

To work out the problem, and then, if you choose,

You may turn it and twist it the Dons to amuse.

In 1884, an abridged second edition of the biography was published which included several previously unpublished scientific letters. I particularly enjoyed the following excerpt from a letter that Maxwell sent to Faraday in 1859:

“DEAR SIR—I am a candidate for the Chair of Natural Philosophy in the University of Edinburgh, which will soon be vacant by the appointment of Professor J. D. Forbes to St. Andrews. If you should be able, from your knowledge of the attention which I have paid to science, to recommend me to the notice of the Curators, it would be greatly in my favour, and I should be much indebted to you for such a certificate.”

I don't know whether Faraday obliged with a glowing recommendation, but Maxwell didn't get the job!

(The original version of the column appeared in “AP-S turnstile,” IEEE Antennas and Propagation Magazine, vol. 41, no. 1, p. 116, February 1999.)

Note

1. For additional material on Maxwell and his famous equations, see Sections 4.1, 10.4, and 10.5.

1.4 Do-It-Yourself Execution?

An article by Niels Jonassen of the Technical University of Denmark (Compliance Engineering, January/February 1998) sparked my interest in Benjamin Franklin's technical writings. In July 1750, Franklin proposed the following experiment in a letter to his British friend P. Collison in London:

“To determine the question whether the clouds that contain lightning are electrified or not I would propose an experiment to be tried where it may be done conveniently. On top of some high tower or steeple place a kind of sentry box…big enough to contain a man and an electrical stand [an insulated platform]. From the middle of the stand let an iron rod rise and pass bending out of the door, and then upright twenty or thirty feet, pointed very sharp at the end. If the electrical stand be kept clean and dry, a man standing on it when clouds are passing low might be electrified and afford sparks, the rod drawing fire to him from the cloud.”

An astonishing suggestion, indeed, from the inventor of the lightning rod, particularly when one considers the next statement in Benjamin Franklin's letter: “If any danger to the man be apprehended (though I think there would be none)…” Fortunately for Franklin, there was no suitable tower in Philadelphia, so he did not get a chance to try this “glow in the dark” experiment himself! However, his letter received a wide and enthusiastic audience in Europe. In May 1752, the French scientist d'Alibart carried out the experiment near Versailles and lived to tell the tale at the Academy of Sciences in Paris 3 days later. Soon after, the experiment was successfully duplicated in France again, in England, and in Belgium. Next year the Swedish physicist Georg Richman, working in Russia, installed “lightning chords” through the roof of his house with the chords ending above his desk so that he could observe the lightning phenomenon from the comfort of his chair. On July 26, 1753, the top of the lightning chords received a direct lightning strike and, in the memorable words of his colleague Lomonosov, Richman died a splendid death fulfilling a duty of his profession.

Meanwhile, back home in Philadelphia, Franklin, apparently unaware of the European experiments, “improved” on his original idea and thought of the famous kite experiment (which dispensed with the need for a tower). Sometime during the summer of 1752, the classic experiment was performed: sparks jumped from the metal key at the end of the electrified conducting kite string to Franklin's hand. No harm done! Since then a number of people have been killed imitating Benjamin Franklin. In the late nineteenth and the early twentieth centuries, large box kites carrying meteorological instruments were used by many US Weather Bureau stations. The kites used weighed 8 lb, carried a couple of pounds of instrumentation, and dragged a good deal of piano wire (“kite string”) behind them. In one case, a man assisting in the flight was killed when the kite was struck by lightning [1].

Reference

M. Uman,

All About Lightning

, Dover, 1986.

(The original version of the column appeared in “AP-S turnstile,” IEEE Antennas and Propagation Magazine, vol. 40, no. 2, p. 102, April 1998.)

Notes

1. A good biography of Ben Franklin is: W. Issacson,

Benjamin Franklin: An American Life

, Simon & Schuster, 2003.

2. A farmer and his cow are caught outdoors in a thunderstorm. A pine tree near them is struck by lightning. The cow is electrocuted but the farmer survives to tell the tale. How?

(a) The cow presents a much larger capacitance than the farmer.

(b) The cow happens to be a bit closer to the tree.

(d) It is a totally random occurrence.

The current from the lightning strike, which can be tens of thousands of amperes, passes into the earth at the base of the tree and spreads out radially in the top conducting layer of the ground. This sets up a potential gradient along the surface. The cow's foot near the tree will be at a much higher potential (depending on the ground resistance) than the foot farthest away from the tree. Clearly, a current will flow through the cow from one end to the other and could well be fatal.

Source: R. Bansal, “Zapped: A pop quiz on electrostatics,” IEEE Potentials, pp. 5–6, April/May 2000.

3. Textbook resources:

(i) W. H. Hayt and J. A. Buck,

Engineering Electromagnetics

, 8th ed., McGraw-Hill, New York, 2012. Electrostatic fields are discussed in Chapters 2–6.

(ii) F. T. Ulaby and U. Ravaioli,

Fundamentals of Applied Electromagnetics

, 7th ed., Prentice Hall, Upper Saddle River, NJ, 2015. Electrostatic fields are discussed in Chapter 4.

1.5 Franklin: Did He or Didn't He?

Benjamin Franklin's investigations [1] into electricity were discussed previously in Section 1.4. As all American children learn in school, Mr. Franklin showed that lightning was a form of electricity through his celebrated “kite experiment” sometime in 1752. Now a new book [2] by Tom Tucker poses the iconoclastic question: Did Benjamin Franklin really fly that kite?

To backtrack a little bit, in July 1750, Franklin had proposed the following experiment in a letter to his British friend P. Collison in London [1, 3]:

As pointed out in Section 1.4, fortunately for Franklin, there was no suitable tower in Philadelphia, so he did not get a chance to try this dangerous experiment himself! However, thanks to his letter, the experiment was carried out successfully several times in Europe. Meanwhile, back home in America, Franklin, apparently unaware of the European demonstrations, refined his original idea and thought of the famous kite experiment, which did not need a tower. Sometime during the summer of 1752, the classic experiment was performed: sparks jumped from the metal key at the end of the electrified conducting kite string to Franklin's hand. Or at least that is the way the story is conventionally told. Tucker, the author of Bolt of Fate [2], has his doubts though. He asks us to read carefully the account of the kite experiment Franklin published in the Pennsylvania Gazette [4]:

“The kite is to be raised, when a thundergust appears to be coming on, (which is very frequent in this country) and the person, who holds the string, must stand within a door, or window, or under some cover, so that the silk riband may not be wet… As soon as any of the thunder-clouds come over the kite, the pointed wire will draw the electric fire from them; and the kite, with all the twine, will be electrified; and the loose filaments of the twine will stand out every way, and be attracted by the approaching finger. When the rain has wet the kite and twine, so that it can conduct the electric fire freely, you will find it stream out plentifully from the key on the approach of your knuckle… All the other electrical experiments [can] be performed, which are usually done by the help of a rubbed glass globe or tube, and thereby the sameness of the electric matter with that of lightning completely demonstrated” [emphasis added].

Tucker was intrigued by the conditional spirit and the unusual future tenses used by Franklin in describing this experiment. He compared it with the reports of other experiments conducted by Franklin and found that the impersonal future-tense style used in the excerpt above was typical neither of the eighteenth century scientific reports in general nor of Franklin's own work in particular. In fact, according to Tucker, Franklin was usually very careful in describing exactly how, when, and where he did a particular experiment: “he gives specifics, he uses active voice, he offers diagrams, he says he did it.”

In another recent biography [5] of Benjamin Franklin, Issacson does not accept Tucker's analysis. He cites the great historian of science I. Bernard Cohen's books on Franklin's science. Cohen notes that the “kite experiment” was later reproduced by others and it was unlike Franklin to have just made up the account. Tucker, for his part, draws attention to a series of (nonscientific) hoaxes that Franklin pulled in his publishing career.

I would like to conclude this section by quoting from Gopnik [4], who points out that it was Franklin who edited Jefferson's draft to come up with the words “We hold these truths to be self-evident”:

“The moral of the kite [story] is not that truth is relative. It is that nothing is self-evident.… We hold these truths as we hold the twine, believing, without being sure, that the tugs and shocks are what we think they are. We hold the string, and hope for the best. Often, there is no lightning. Sometimes, there is no kite.”

References

R. Bansal, “AP-S turnstile: do-it-yourself electrocution?”

IEEE Antennas and Propagation Magazine

, vol. 40, no. 2, p. 102, April 1998.

T. Tucker,

Bolt of Fate: Benjamin Franklin and His Electric Kite Hoax

” PublicAffairs, 2003.

M. Uman,

All About Lightning

, Dover, 1986.

A. Gopnik, “American Electric,”

The New Yorker

, pp. 96–100, June 30, 2003.

W. Issacson,

Benjamin Franklin: An American Life

, Simon & Schuster, 2003.

(The original version of the column appeared in “AP-S turnstile,” IEEE Antennas and Propagation Magazine, vol. 45, no. 4, pp. 82–83, August 2003.)

Notes

1. The electric charge delivered to the earth during a lightning strike is around

(a) 1 nC

(b) 1 C

(d) 10

(b) 1 C

Since the electric filed is defined as the force exerted on a unit charge (1 C in the meter-kilogram-second, MKS, metric system), it is a common mistake to think that 1 C represents a tiny charge. Actually, the MKS unit of charge (named after Charles Coulomb) is way too large for most electrical engineering applications. Recall that a negative charge of 1 C will require almost 6 × 1018 electrons, hardly a “point charge” but rather the type of charge transfer that takes place during a violent phenomenon like a lightning strike.

Source: R. Bansal, “Zapped: A pop quiz on electrostatics,” IEEE Potentials, pp. 5–6, April/May 2000.

2. Textbook resources:

(i) W. H. Hayt and J. A. Buck,

Engineering Electromagnetics

, 8th ed., McGraw-Hill, New York, 2012. Electrostatic fields are discussed in Chapters 2–6.

(ii) F. T. Ulaby and U. Ravaioli,

Fundamentals of Applied Electromagnetics

, 7th ed., Prentice Hall, Upper Saddle River, NJ, 2015. Electrostatic fields are discussed in Chapter 4.

3. Reference [1] is included in this book as Section 1.4.

1.6 De Magnete (“On the Magnet”)

Navigators all at sea

Don't eat onions for their tea

Not that they're at all emetic

They make the compass nonmagnetic

At the dawn of the twenty-first century, it may seem quaint that British naval helmsmen were once flogged if they were found to be in violation of the regulation [1] that “steersmen, and such as tend the Mariner's Card are forbidden to eat Onyons and Garlick, lest they make the index of the poles drunk.” But such was indeed the sixteenth century world into which William Gilbert (1544–1603) was born. The year 2000 marked the 400th anniversary [2] of the publication of his pioneering treatise “De Magnete” (ix+246 pp, 7/6 (37.5 p) in London; 2 Thaler in Frankfurt; Published by Peter Short, London, 1600), which eventually helped dispel many nonsensical beliefs about magnetism. Predating Kepler's Astronomia Nova (1609), which described laws of planetary motion, and Galileo's Sidereus Nuncius (1610), which reported on his astronomical observations with the telescope, Gilbert's book on magnetism is considered by many to be the first scientific monograph written on modern principles. (Newton's Principia came much later in 1687.) Like a present-day doctoral dissertation, “De Magnete” [3] reviews previous work, describes Gilbert's experimental investigations and results, discusses his findings in a broader context, and finally provides speculations about future work [4].

William Gilbert was born in 1544 in Colchester (some 50 miles NE of London), where his father held the prestigious post of Recorder. Gilbert studied at St John's College, Cambridge, where he remained for 11 years until 1569, acquiring bachelor's and master's degrees, as well as his credentials as a physician. He settled in London to practice medicine and eventually became President of the Royal College of Physicians and Physician to Queen Elizabeth I. He died of bubonic plague in London in 1603 [4].

Gilbert's research on magnetism was really a hobby. Over a 20 year period (1581–1600), he conducted experiments in electrostatics (contributing to our vocabulary terms such as “electrick force”) and in magnetostatics. For his work on geomagnetism, Gilbert constructed a spherical lodestone which he called terrella (“little earth”). Using small compass needles, he explored the magnetic field of his terrella and extrapolated his findings to the effect of the earth's magnetic field on the behavior of a magnetic compass. For example, to simulate the effects of proximity to landmasses, he carved out “oceans” from the terrella and found that the compass needles behaved differently near oceans and mountain ranges [4].

Gilbert supported the Copernican theory and also believed that the earth turned on its axis. However, he erroneously associated this planetary rotation with magnetism. The concept of a revolving earth was so heretical at the time that the continental copies of his book had the related pages expunged [4].

To celebrate Gilbert's contributions to magnetism, the American Geophysical Union, which publishes Radio Science, held a special session at its Spring 2000 meeting in Washington, D.C. The AGU journal Eos also published a belated (!) “book review” of “De Magnete,” which is accessible online with a lot of other fascinating details about Gilbert's work and geomagnetism on a NASA website [4] maintained by Dr. David Stern.

If you fast forward the history of magnetism to the year 2000, you may wish to take note of some recent work on nanomagnets reported in the Journal of Applied Physics [5]. A cooled mixture of iron oxide, polystyrene, and methanol under the influence of a strong magnetic field behaves like a jarful of tiny compasses (nanomagnets). The Barcelona group, which did the work on nanomagnets, expects that they may someday lead to super-fast electronic switches and more efficient cores for power equipment. However, in making predictions about how soon nanomagnets may find real-life applications, it may be worthwhile to remember that it was almost 100 years after the publication of “De Magnete” before the flogging of British helmsmen with garlic-breath finally stopped.