Q. Before wires and electricity, all real-time communication across distances was wireless, such as signaling by bonfires, smoke signals, semaphores. So how did we get from wireless to wired and back again to wireless today?
A. Wired pioneer Samuel Morse developed telegraphy in 1837, and by the time Alexander Graham Bell invented the telephone in 1876, “wires had already crossed the American continent and the Atlantic Ocean,” says Robert Lucky in “IEEE Spectrum” magazine. Twenty years later came Guglielmo Marconi's “wireless” or radio, used initially in ship-to-ship and ship-to-shore transmission, and that played a critical role in the rescue of the Titanic survivors in 1912. But the real “killer app” for wireless turned out to be commercial broadcasts of radio and television, though virtually all interpersonal communications remained wired, even the telephone. Then, with the rise of the cable industry toward the end of the 20th century, “even television transmissions moved from air to earth.”
Yet, today our phones, our smart appliances, even our computer mice are wireless. This revolution also is sweeping developing nations, where wired infrastructure is cost-prohibitive. As Lucky concludes, “The curious thing is that in the last century, broadcast was all wireless and personal communication all wired; now it is exactly the reverse — but stay tuned.”
Q. Why do 3-D televisions sometimes seem unsettling, even causing headaches in some viewers?
A. First some background: The concept of 3-D dates back to physicist Charles Wheatstone's “stereoscope” of the 1830s, where one image is presented to the right eye and the other to the left eye, explains Byoungho Lee in Physics Today. Then the brain wraps this “binocular disparity” into a single image that gives the illusion of depth — like the popular View-Master of some years ago.
Despite their technological sophistication, today's 3-D televisions still rely on Wheatstone's concept. But, unfortunately for viewers, the brain also makes use of the angles the eyes have to rotate to bring an object into central view; and the degree the lenses have to change shape for focusing. Since the flat television screen is at a fixed distance from the eyes, these special adjustments are lacking, so the brain gets contradictory information. With prolonged viewing, Lee concludes, this can lead to disorientation, discomfort and even headaches.
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