Here’s a nifty map of the world’s undersea cables.
The era of long-distance undersea communication began with the laying of the first Atlantic telegraph cable, completed in August of 1858. Unfortunately, signal quality deteriorated rapidly and an attempt was made to improve communication by increasing the voltage at the transmitting end…a more durable cable was put in service in July of 1866.
Rapid trans-Atlantic communication made a huge difference in many spheres of life, not least in the logistics of international trade. Consider this quote from an English visitor to the US in the pre-cable year of 1852:
If, on the arrival of an European mail at one of the northern ports, the news from Europe reports that the supply of cotton or of corn is inadequate to meet the existing demand, almost before the vessel can be moored intelligence is spread by the Electric Telegraph, and the merchants and shippers of New Orleans are busied in the preparation of freights, or the corn-factors of St Louis and Chicago, in the far west, are emptying their granaries and forwarding their contents by rail or canal to the Atlantic ports.
Pre-cable, transmitting a purchase order across the Atlantic took as long (ignoring the effects of prevailing winds/currents) as the shipment of the physical goods.
Fanny Kemble wrote (circa 1882) about the psychological impact of connecting the continents electrically:
To those who know the rate of intercourse between Europe and America now, these expressions of the painful sense of distance from my country and friends, under which I suffered, must seem almost incomprehensible,—now, when to go to Europe seems to most Americans the easiest of summer trips, involving hardly more than a week’s sea voyage; when letters arrive almost every other day by some of the innumerable steamers flying incessantly to and fro, and weaving, like living shuttles, the woof and warp of human communication between the continents; and the submarine telegraph shoots daily tidings from shore to shore of that terrible Atlantic, with swift security below its storms. But when I wrote this to my friend, no words were carried with miraculous celerity under the dividing waves; letters could only be received once a month, and from thirty to thirty-seven days was the average voyage of the sailing packets which traversed the Atlantic…The distance between the two worlds, which are now so near to each other, was then immense.
Rates of information transmission on these early cables were low…Wikipedia puts the bandwidth (as we would now call it) of the 1866 cable at 8 words per minute…and message prices were correspondingly high. Improvements in telegraphy speeds were made over time, but the first trans-Atlantic undersea link capable of carrying voice traffic…the TAT-1…was not operational until 1956. It could handle only 36 simultaneous calls.
Cable’s dominant position in trans-oceanic communication was challenged by communications satellites, beginning with Telstar in 1962, but with the introduction of fiber-optic transmission (TAT-8 in 1988…40,000 simultaneous calls), cable once again took the lead over wireless in this field.
An example of a modern undersea cable system is the Emerald Atlantis, connecting the US, UK, Canada, and Iceland. One of the major objectives of this project is to further increase the attractiveness of Iceland as a location for large data centers…it already offers the advantage of low-cost electricity from sources–geothermal and hydroelectic–that can be marketed as “green.” (Also, the chilly climate simplifies data-center cooling issues.)
“The cloud” is actually a lot less ethereal than the term would lead one to believe.