# Why did the first Transatlantic telegraph messages take so long to transmit? **URL:** \ **Category:** Factual Questions\ **Created:** [May 21, 2009, 5:03pm UTC](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200 "2009-05-21T17:03:17Z")\ **Posts on this page:** 7\ **Page:** 3
**Author:** ![wheresmymind](https://avatars.discourse-cdn.com/v4/letter/w/91b2a8/32.png) [@wheresmymind](https://boards.straightdope.com/u/wheresmymind)\ **Post date:** [November 30, 2012, 2:17am UTC](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200/41 "2012-11-30T02:17:25Z")
> [@Machine\_Elf](#): > > Just for fun: > > [747-ERF](http://en.wikipedia.org/wiki/747-400#Specifications) can carry 248,000 pounds of cargo. Looks like hard drives are up to 4 terabytes each now, and a 3.5" SATA drive weighs in at about 1.6 pounds. So that’s 155,000 hard drives, for 620,000 petabytes of data. > > Flight time from Dulles to Heathrow is 7hrs 15min. So bandwidth is… > > 23.8 terabytes per second. Wow. So that’s almost 200 Tbits/sec. It looks like the current fastest cables are on the order of a few tens of Tbits/sec. Just for fun, how would today’s shipping industry fare? A large container ship might carry 12,000 containers and cruise at 25 knots (~28 mph). Say 10,000 lbs per container, that’s 60,000 tons, or 75 million drives with 300 _exabytes_ (that’s 10^18, quintillion) of data. Moving at 28 mph it will cover 4,000 miles in 6 days. That’s… 580 terabytes per second. Or 4.64 petabits per second. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [November 30, 2012, 2:47am UTC](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200/42 "2012-11-30T02:47:04Z")
[QUOTE=lisiate] Still have things really changed that much. How much data can you fit onto a 747 laden with USB drives? [/QUOTE] Probably more than a station wagon filled with tapes hurtling down the highway. ---
**Author:** ![zoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zoid/32/336_2.png) [@zoid](https://boards.straightdope.com/u/zoid)\ **Post date:** [November 30, 2012, 3:06am UTC](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200/43 "2012-11-30T03:06:30Z")
> [@gotpasswords](#): > > Probably more than a station wagon filled with tapes hurtling down the highway. _National Lampoon presents **VACATION XXI** _ ---
**Author:** ![bengangmo](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@bengangmo](https://boards.straightdope.com/u/bengangmo)\ **Post date:** [November 30, 2012, 3:14am UTC](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200/44 "2012-11-30T03:14:56Z")
> [@Machine\_Elf](#): > > Just for fun: > > [747-ERF](http://en.wikipedia.org/wiki/747-400#Specifications) can carry 248,000 pounds of cargo. Looks like hard drives are up to 4 terabytes each now, and a 3.5" SATA drive weighs in at about 1.6 pounds. So that’s 155,000 hard drives, for 620,000 petabytes of data. > > Flight time from Dulles to Heathrow is 7hrs 15min. So bandwidth is… > > 23.8 terabytes per second. > > In the 9+ days it would have taken the Persia to make the crossing, the 747 could have made 15 round trips, moving 1860 tons of cargo in each direction. Double the time (so the Persia can make a round trip and move 1000 tons of cargo in each direction), and the 747 wins by a factor of 3+. Is the 747 going to be limited by volume or weight? ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [November 30, 2012, 3:26am UTC](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200/45 "2012-11-30T03:26:15Z")
> [@wheresmymind](#): > > Wow. So that’s almost 200 Tbits/sec. It looks like the current fastest cables are on the order of a few tens of Tbits/sec. > > Just for fun, how would today’s shipping industry fare? A large container ship might carry 12,000 containers and cruise at 25 knots (~28 mph). Say 10,000 lbs per container, that’s 60,000 tons, or 75 million drives with 300 _exabytes_ (that’s 10^18, quintillion) of data. Moving at 28 mph it will cover 4,000 miles in 6 days. That’s… > > 580 terabytes per second. Or 4.64 petabits per second. Take the [Emma Maersk.](http://en.wikipedia.org/wiki/Emma_maersk) -cruises at 29.3 MPH. for the 3670-mile journey from DC to Southampton, that’s 450,921 seconds. -can carry 13,500 TEU’s at 14 tons per TEU. That’s 378M pounds of hard drives, or 236M hard drives, or 945M terabytes. Effective one-way data rate, then, is 2 petabytes per second. That pretty much beats the crap out of the 747, if you don’t mind the latency. > [@bengangmo](#): > > Is the 747 going to be limited by volume or weight? hard drives are pretty dense - 1.6 pounds for a 3.5" SATA drive - so I’d guess they’re weight-limited for this mission. ---
**Author:** ![Zebra](https://avatars.discourse-cdn.com/v4/letter/z/c0e974/32.png) [@Zebra](https://boards.straightdope.com/u/Zebra)\ **Post date:** [November 30, 2012, 3:36am UTC](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200/46 "2012-11-30T03:36:41Z")
See honey? It’s _totally necessary_ for me to have gold plated cable connectors. ---
**Author:** ![JWT\_Kottekoe](https://avatars.discourse-cdn.com/v4/letter/j/3ec8ea/32.png) [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)\ **Post date:** [December 1, 2012, 3:29am UTC](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200/47 "2012-12-01T03:29:41Z")
It took some of the greatest minds of 19th century mathematics to fully elucidate why the first transatlantic cable worked so badly. In particular, I have heard that Riemann’s theory of the characteristics of partial differential equations was motivated by this problem. The key, as some have alluded to above, is the recognition of the importance of resistive loss in a system that, at low frequencies, is largely capacitive. If you think about a network of series resistors periodically shunted to ground by capacitors, you’ll realize that the signal does not propagate at a fixed speed. The first capacitor charges exponentially in time, generating a voltage that charges the next capacitor, and so on and so on. If you analyze this, you find that the signal essentially diffuses from one end of the line to the other, rather than propagating. It is like the flow of heat. If you double the distance, the time goes up by a factor of four, rather than a factor of two. It is like trying to communicate to the inside of a turkey by pulsing the temperature of the oven up and down. If you are deep within the turkey, this is a very slow way to communicate, and if you pulse the temperature too quickly, the signal will be averaged out. Since the transmission line highly distorts the signal, you can’t just transmit quickly and wait a long time for the signal to reach England. You have to transmit each dot or dash extremely slowly, otherwise the symbols will overlap at the recieving end (intersymbol interference). It took the genius of Oliver Heaviside to figure this out and recommend the introduction of coils periodically (loading coils) to increase the inductance per unit length, thus allowing the system to actually propagate the signals at a constant velocity, rather than making the signals diffuse across the ocean. People thought he was nuts, because everyone knew that inductance was a bad thing, and could only make matters worse. [Previous page](https://boards.straightdope.com/t/why-did-the-first-transatlantic-telegraph-messages-take-so-long-to-transmit/497200.md?page=2)