Table of Contents Early Communication 4 What Are Waves 9 Electromagnetic Radiation 15 Technology and Communication 24 Modern Communication 35 Timeline 45 Glossary 46 Index 47 Show What You Know 47 Websites to Visit 47 About the Author 48
Early Communication What do you do when you want to talk to a friend across town Text Call Both are simple to do but think about how people communicated before technology harnessed the power of electromagnetic waves Written communication has been used since ancient times The Phoenicians an ancient civilization developed a simple alphabet Another ancient civilization the Sumerians used picture writing 4 Sumerian cuneiform is the earliest known writing system dating back to about 8000 BCE It developed from the pictographs and other symbols used to represent trade goods and livestock on clay tablets
Oral messages were important for quick communications Messengers often ran messages to the recipient Horseback provided a means for faster delivery Eventually post offices developed Still people often needed to send messages even faster Over the centuries the search for speedy communication evolved As writing communications developed using electromagnetic waves for fast communication also developed Joseph Henry’s development of the first electric telegraph in 1831 led to a way for sending fast messages Other inventors improved on this Joseph Henry 1797 1878 The telegraph uses electricity to send coded messages through wires 5
Used mainly for individual messages at first news agencies adopted the electric telegraph as a way to get the latest updates on developing news stories Reporters used it for updating sports scores as well Early telegraph lines were primitive Soon the use of two lines one for sending and a second for receiving improved message sending In 1835 Samuel Morse developed the Morse code which used dots and dashes for the alphabet further simplifying message delivery The telegraph changed the dots and dashes of this code into electrical impulses and transmitted them over telegraph wires A telegraph receiver on the other end of the wire converted the electrical impulses to dots and dashes on a paper tape 6
