Here's what sound waves look like. The caption reads, "A visible pattern of sound waves. This new technique of studying sound demonstrates the focusing effect of an acoustical lens on sound waves issuing from the horn at extreme left. Wave pattern is produced by a scanning technique . . ." Bell Telephone Laboratories photograph, from the book The First Book of Sound: A Basic Guide to the Science of Acoustics by David C. Knight, Franklin Watts, Inc. New York (1960). p. 80
In somewhat challenging yet elegant writing, A.T.&T. once described sound in these terms, "Audible sound is thus defined as a disturbance in the atmosphere whereby a form of wave motion is propagated from some source at a velocity of 1,075 feet per second, the transmission being accomplished by alternating condensations and rarefacations of the atmosphere in cycles having a fundamental frequency ranging somewhere between 16 per second and 32,000 per second." Principles of Electricity applied to Telephone and Telegraph Work, American Telephone and Telegraph. C.F. Myers, Supervisor of Instruction. Murray Hills, New Jersey? 1939. p.66
I write a great deal about sound and radio waves, I've even discussed light waves in passing. But did you know that all matter is a wave? A never ending ocean of waves, one after the other, endlessly rolling outward. We usually think of matter as particles; electrons, photons, atoms, somewhat solid forms. But matter as a wave? Actually, matter can be a particle and a wave at the same time. Prince Louis de Broglie (1892-1987), postulated in 1923 that atoms and their associates constituted solid form and also acted as waves of radiated energy. Although the work of Max Planck and Einstein helped Broglie develop his theory, at the time he advanced his idea there was absolutely no physical evidence to support it. Acceptance and confirmation by others came quickly, however, and in 1929 he was awarded the Nobel Prize. As Martin Mann explains the photograph below, "Electrons, passing through a crystal, make a pattern almost exactly like a light beam. Only waves can interact with each other to produce such patterns; streams of individual solid [particles] cannot."
The future might seem unlimited for telephony, with new technologies invented every day. But even telephony has a limit, a barrier it cannot cross: time. For years satellite phones have permitted anyone at any location to call anyone else who has a phone. Going further, a video telephone like the one envisioned by Arthur C. Clarke in 2001: A Space Odyssey, could certainly work in Earth orbit. But such a payphone on Mars would be impossible. Clarke himself reminded us in 1977 that a call would take three minutes to get to Mars and three more minutes to receive a reply. Telephony requires a communication link providing an almost instanteous response between both parties. Such a delay would eliminate telephony, substituting for it a message service.
Although unlimited information could be sent between both parties, the feedback and instant response provided by telephony would be lost. Anyone repairing a Mars orbiting space station will have no quick help from Houston. Delays and confusion will result, especially with problems needing immediate attention. While telephony can overcome distance for us on earth, it itself cannot overcome the distances it must travel; although radio waves race at the speed of light in space, they cannot run any faster. Which takes me to a related point.