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The British empire's resilient subsea telegraph network

subseacables.blogspot.com

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Re: The British empire's resilient subsea telegraph network

#21

Post by hylaride »

joecool1029 wrote: post #19
hylaride wrote: post #11

Earlier quoted context omitted.

Over long distances, fibre optic would have lower latency so it'd be shorter if taking the same path today. But these signals would likely have been morse code and sent one-way at a time, so latency wouldn't have been noticed unless the repeaters were people rebroadcasting the signal (no idea how that was done).

> Over long distances, fibre optic would have lower latency so it'd be shorter if taking the same path today. Source that claim, it's well understood the speed of light is around 66% due to refractive index in glass. It gets weird with telegraph cables and capacitance, wikipedia at least touches on it here: https://en.wikipedia.org/wiki/Speed_of_electricity

I should have definitely qualified that statement. Technically, electrical signals over copper are "slowed down" less than light through fibre optic cables. However there's attenuation, electromagnetic interference, and other signal loss for electrical signals that (for long haul cables) will mean you will need repeaters that add significant amounts of latency. On top of that, the higher you try and up the frequencies, the worse these problems get.

For some medium-haul stuff, it wouldn't surprise me if you saw copper still being used for lower latency (eg between datacenter sites for flash-trading), but otherwise it's just not economical.

Re: The British empire's resilient subsea telegraph network

#22

Post by kitd »

alexfoo wrote: post #9
neillyons wrote: post #3

When visiting Ayers Rock in Australia I stayed in Alice Springs. While I was there I learnt that Alice Springs exists because it was a repeater station for a telegraph line that stretched from Southern Australia all the way to London. There would be people listening to morse code, and tapping it out again to the next repeater station. Blew my mind that there was a wire that went all the way to London from Australia!

> Blew my mind that there was a wire that went all the way to London from Australia! Before the telegraph they used to do things wirelessly: https://www.brunningandprice.co.uk/_downloads/telegraph/tele... (Not quite London to Australia though...) In the late-1700s/early-1800s the Admiralty Telegraph was used to relay messages between London and Portsmouth (70 odd miles apart) using a semaphore type system with repeat…

Yes, the Uk (southern England in particular) is dotted with "Semaphore Hill"s or "Telegraph Hills"s. There's one very close to where I'm sitting now, a few miles NE of Portsmouth.

Re: The British empire's resilient subsea telegraph network

#23

Post by kitd »

jphoward wrote: post #2

Here is some more information: https://en.wikipedia.org/wiki/All_Red_Line And one of the old cable huts still exists: https://en.wikipedia.org/wiki/Pacific_Cable_Station

My wife and I were visiting County Kerry in SW Ireland last summer. We were on Valentia Island and quite by chance walked past the telegraph building where the first transatlantic cable came ashore. Only marked by a (very interesting) plaque describing its significance.

Re: The British empire's resilient subsea telegraph network

#24

Post by jimmySixDOF »

... an era bookmarked at the end by the first live music broadcast transatlantic performance of Old Man River from a studio in NYC to a theater in London and that wasn't until 1957 and is a story all on its own

https://www.sciencemuseum.org.uk/objects-and-stories/robeson...

Re: The British empire's resilient subsea telegraph network

#25

Post by retrac »

andyjohnson0 wrote: post #6

An interesting book on the subject of telegraph networks is The Victorian Internet by Tom Standage [1]. As well as the technical and commercial drivers, it also describes how the telegraph forced people to confront concepts like simultaneity, information being distinct from its physical medium, privacy, early approaches to encryption, etc. A fascinating book. [1] https://en.wikipedia.org/wiki/The_Victorian_Internet

The GBP/USD currency pair is still known just as "the cable".

Aside from all its other uses: the telegraph gave a way to synchronize clocks. And accurate time is accurate measurement of distance.

> [...] The latest determination in 1892 is due to the cooperation of the McGill College Observatory at Montreal, Canada, with the Greenwich Observatory. [...] The final value for the longitude of the Harvard Observatory at Cambridge, as adjusted in June, 1897, is 4h 44m 31s.046 ±0s.048.

-- https://adsabs.harvard.edu/full/1897AJ.....18...25S

71.12936 W; give or take about 2 metres: https://www.bing.com/maps/?v=2&cp=42.38148%7E-71.12936&style...

Re: The British empire's resilient subsea telegraph network

#26

Post by everfrustrated »

hylaride wrote: post #21
joecool1029 wrote: post #19

Earlier quoted context omitted.

> Over long distances, fibre optic would have lower latency so it'd be shorter if taking the same path today. Source that claim, it's well understood the speed of light is around 66% due to refractive index in glass. It gets weird with telegraph cables and capacitance, wikipedia at least touches on it here: https://en.wikipedia.org/wiki/Speed_of_electricity

I should have definitely qualified that statement. Technically, electrical signals over copper are "slowed down" less than light through fibre optic cables. However there's attenuation, electromagnetic interference, and other signal loss for electrical signals that (for long haul cables) will mean you will need repeaters that add significant amounts of latency. On top of that, the higher you try and up the frequencie…

That's the point of hollow-core fibre which is absolutely being used where decreasing latency even by small amounts is worth it.

Re: The British empire's resilient subsea telegraph network

#27

Post by daedrdev »

teleforce wrote: post #5

Fun facts, the subsea telegraph network cables coating were made from Gutta Percha [1]. Unlike normal rubber, it is a type of thermoplastic and it's a popular organic plastic before the petroleum based modern plastic become pervasive [2]. [1] The legacy of undersea cables: https://blog.sciencemuseumgroup.org.uk/the-legacy-of-underse... [2] Gutta-percha: https://en.wikipedia.org/wiki/Gutta-percha

They also got a tiny fraction of the rubber from cutting a whole tree down due to not finding a method to get all the rubber, and so cut almost all of the trees down

Re: The British empire's resilient subsea telegraph network

#29

Post by zoeysmithe »

andyjohnson0 wrote: post #6

An interesting book on the subject of telegraph networks is The Victorian Internet by Tom Standage [1]. As well as the technical and commercial drivers, it also describes how the telegraph forced people to confront concepts like simultaneity, information being distinct from its physical medium, privacy, early approaches to encryption, etc. A fascinating book. [1] https://en.wikipedia.org/wiki/The_Victorian_Internet

That book led me to Gutta Percha, the plastic-like coating on the wires used in these cables which was quite the innovation and made this all possible. Vulcanized rubber was the other option but performed poorly in cables and was harder to work with.

https://atlantic-cable.com/Article/GuttaPercha/

The above is a fascinating and depressing history of the Gutta Percha factory that made all these cables, after joining with the cable company that supplied the actual wires. There's an 1853 travelogue piece embedded here of an author visiting the factory, where he notes in the worst parts of the factory where boiling and heat are applied, it was staffed with boys who barely made more than a dollar a week. By boys I thought it was slang for young men then I realized 1850s England was heavily using child labor.

Those cables are the product of child labor, like much of the Victorian age's industrial and textile output. Children often made up significant portions of factory workforces, sometimes 25-50% in certain textile sectors, with many under 14. I wish the stories of child labor were better told and more prominent. This abuse and exploitation of children gets quite whitewashed during this age and its nice to see it acknowledged, albeit briefly.

Re: The British empire's resilient subsea telegraph network

#30

Post by KineticLensman »

It was strategically important in WW1 because the British could communicate with the colonies with very chance little chance of messages being intercepted. The Germans, in contrast, didn't have access to their own transatlantic channels and had to use plain-text messages on cables that the UK/US controlled (US operators disallowed coded comms).
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