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A rather attractive nanophotonics chip: all of the optical gubbins (transceivers, wave guides) on CMOS.

IBM

For most of humanity's existence, communication has been incredibly slow. For millennia the only way of transmitting information between two humans was via speech or crude drawings. About 5,000 years ago written language and papyrus increased the transmission distance and bandwidth of human-human communication, but the latency, delivered by hand, was still pretty bad.

A relief of the <a href="https://en.wikipedia.org/wiki/Hydraulic_telegraph">Greek hydraulic telegraph</a> of Aeneas, depicting one half of the system.
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A relief of the

Greek hydraulic telegraph

of Aeneas, depicting one half of the system.

Somewhere around 300BC, though—at least according to recorded history—things started to get interesting. Ancient Greece, as described by the historian Polybius, used a technology called hydraulic telegraph to communicate between Sicily and Carthage—a distance of about 300 miles—in the First Punic War.

The system was essentially a slightly higher bandwidth signal fire, with a long unbroken line of humans standing on hilltops with identical telegraph machines. There was still a fair bit of latency, of course, as the humans tweaked the hydraulic levels, but near-speed-of-light electromagnetic radiation was quite a bit faster than papyrus-by-horseback (like the classic example of "driving across the country with a van full of tapes," though, the bandwidth was probably lower).

A diagram of the semaphore used in the UK between London and the coast between 1795 and 1816.
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A diagram of the semaphore used in the UK between London and the coast between 1795 and 1816.

Again, not much happened for the next 2,000 years, but eventually the whole signal-fire-on-top-of-a-mountain concept was upgraded to formalised semaphore telegraph lines at the end of the 18th century. Semaphore, while a significant improvement over other long-range comms channels, was still hampered by the fact it relied on optics; a human had to be able to physically see the next semaphore tower.

Just a few decades later in 1838, however, the first electrical telegraph was commercialised, and then, well, everything started to accelerate really quickly. A telegraph cable was laid between England and France in 1850; in 1866 the new world was connected to the old; and then by 1872, those amazing Victorians had run cables to India and Australia, connecting up the entire British Empire.

The "All Red Line"—the British Empire's submarine cable network, which was completed in 1902 with a cable across the Pacific.

The "All Red Line"—the British Empire's submarine cable network, which was completed in 1902 with a cable across the Pacific.

Suddenly and paradoxically the world became both larger and much smaller. Information could travel around the world in a few seconds. Orders could be given, trades could be made, news could be shared. Before the All Red Line a Londoner might've waited weeks or months to hear about antipodean goings-on; once it was completed, yesterday's happenings were in tomorrow's newspaper.

And today, of course, there's no delay at all. We produce, transmit, and consume instantly and incessantly. So it goes.

What a difference a millisecond makes

For better or worse, many tranches of civilisation now rely on sub-second latency. High-frequency trading (HFT), where computers algorithmically interact with the stock market at a very rapid clip, is pointless without an equally quick network connection—you'll just lose out to other HFTs with lower-latency connections. Over time, that could be the difference between making and losing billions of dollars.

Latency matters when it comes to disaster response and national security, too: a few milliseconds might be the difference between a remote sensor sending data back to the lab during a natural disaster or disease outbreak, or a soldier squirting important intelligence back to base before the link is severed. Even social interactions care about latency; I'm sure you've experienced a laggy Skype call before, or had a long-distance phone call bounced off a geosynchronous satellite.