Wikipedia:Reference desk/Archives/Computing/2013 December 23

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December 23

Transcontinental Internet lines

Why are transcontinental Internet lines cabled under water rather than be carried by satellite? Clover345 (talk) 11:28, 23 December 2013 (UTC)

Presumably it's less expensive and more reliable. Solar flares, etc., can mess with satellites. Undersea cables can also be quicker, since the signal doesn't travel as far. A satellite in geosynchronous orbit is 42,164 km (26,199 miles) up, and bouncing between several of those can take a good portion of a second, even at the speed of light, and thus cause a noticeable delay. StuRat (talk) 11:35, 23 December 2013 (UTC)

StuRat is correct. Our Submarine communications cable article says "As of 2006, overseas satellite links accounted for only 1 percent of international traffic, while the remainder was carried by undersea cable. The reliability of submarine cables is high, especially when (as noted above) multiple paths are available in the event of a cable break. Also, the total carrying capacity of submarine cables is in the terabits per second, while satellites typically offer only megabits per second and display higher latency." Gandalf61 (talk) 12:11, 23 December 2013 (UTC)

Last transatlantic cable was laid twelve years ago. Hibernia was supposed to have a new one this year, offering a 59 msec latency between London and New York, 6 msec better than the existing cables, an advantage for which financial firms would be prepared to pay 50 times the current rates according to some. The project is stalled however, due to unspecified objections by the US government against the Chinese suppliers involved in the project. Seems the companies failed to "provide clear answers to Committee questions...provide supporting documentation...or alleviate Committee concerns".

Several transatlantic communication cable systems (among them TAT-14 and VSNL Transatlantic) were completed in 2000 and 2001; these were planned during the dot-com bubble, but by the time they became operational the bubble had burst and supply exceeded demand. The existing cables have managed to keep up with capacity demands for the last decade.

High throughput satellite uses multiple narrow beams to increase the available capacity: basically it's just a satellite with lots of antennas each pointing in a different direction and sending and receiving only in a narrow beam so the signals don't mix. That's the same principle as putting 20 or 100 optic fibres in a cable instead of one. The first one launched in 2011 had with its 140 Gbit/s more capacity than all the other communication satellites above North America combined.

The TAT-14 cable system has (had?) 4 fibre pairs operating at 40x10Gbit/s, a total capacity of 3.2 Tbit/s. Mitsubishi Electric won the contract to upgrade the system to 40 Gbit/s per wavelength in 2011, expected to be finished by the 4th quarter of 2012, but instead they did a 40Gbps upgrade of the IMEWE system (Europe, India, Middle East), and while TE SubCom demonstrated a 100 Gbps upgrade for Transatlantic cables in jan 2013, there still hasn't been any news about an upgrade of TAT-14. Perhaps they're waiting until GCHQ has the technology to tap 40 Gbps fibers?

Anyway, with VSNL having 5.1 Tbit/s and TAT-14 3.2 Tbit/s running at 10 Gpbs and Hibernia Atlantic 10.1 Tbit/s running at 40 Gbps, the existing cables could potentially offer almost 100 Tbit/s extra capacity when upgraded to 100 Gbps. With analysts expecting high throughput satellites to supply 1.34 TBps or more capacity by 2020, the domination of transatlantic cable is certain to continue. Ssscienccce (talk) 20:31, 23 December 2013 (UTC)

One reason is latency. The circumference of the earth is around 40,000km, so most point-to-point messages only have to travel 20,000km or less. But a geostationary satellite has to be 35,000km up. So the shortest trip to the satellite and back is 70,000km - and the longest is rather more than that...and of course you need more than one satellite (probably at least two) to get a message from one point on the earth to another - so a worst-case message could easily travel 140,000km to get halfway around the world...at least 5 times worse than the worst-case for a cabled connection and 10 times worse on average. 140,000km is about 0.5 light-seconds, so a satellite link could easily add a second to the time it takes to send a data packet and get a response...versus two tenths of a second by cable. Now consider if someone is using an internet connection to play an online game and there is a one second lag! There is no technological method to eliminate that delay because the speed of light is the cosmic speed limit. The only other approach would be to place a lot of satellites in low earth orbit so that there would always be one overhead or to use balloons or drone aircraft as Google has proposed. SteveBaker (talk) 08:57, 24 December 2013 (UTC)

I believe there are low altitude communication satellites, like the Iridium satellites, at 485 miles (780 km). That project was less than a stunning success, however, due to the cost of so many satellites. Also there's the issue that any antenna pointed at them will need to constantly move or switch satellites to maintain signal strength, and this can cause interruptions in service. StuRat (talk) 13:02, 26 December 2013 (UTC)

I can remember in the 1980's having to ask the telephone operator (in the UK) for a transatlantic marine line, when connecting to Mine of Information and the Well of Knowledge (what ever happened to them) . If I got routed through a com's satellite, then my acoustically coupled modem (remember them) could not compensate for the delay.--Aspro (talk) 00:40, 25 December 2013 (UTC)

There are particles which travel right through the center of the Earth, so theoretically we could get quicker communications with those. Of course, detecting them at the other side is the problem, as they are likely to also travel right through any antenna at the other end, without leaving any sign that they passed through.

Then there's quantum entanglement, where looking at one particle supposedly instantly assigns a state to an entangled particle at any distance. However, as I understand it, the laws of quantum mechanics prevent this from being used for faster than light communications. StuRat (talk) 13:09, 26 December 2013 (UTC)

Windows 8.1 app

Wow, I didn't think that this would be so difficult. Does anyone know where I can find a free app (for Windows 8.1) that simply displays the current date and time? That's all I want: one "live" tile that has both date and time (i.e., keeps a running updated display of the current date and time). I checked the Windows App Store. I installed about a dozen; I had to uninstall them all, for various reasons. Also, I didn't bother to try the ones that had negative reviews. Any suggestions? Thanks. Joseph A. Spadaro (talk) 17:10, 23 December 2013 (UTC)

Have you seen Launch8 by Stardock? It's not free, unfortunately, but it will display the time in a launch bar at the bottom of the Start Screen. It doesn't display the date, but I wouldn't be surprised if they add this feature to a future release. There's a 30 day free trial. A Quest For Knowledge (talk) 21:23, 23 December 2013 (UTC)

Thanks. No, I had not seen that. Actually, that looks interesting, as a whole – for reasons other than my above request. As far as my original request, though, I can't see paying any money for a display of the time. It seems like that basic feature should be free. Thanks for the suggestion. Joseph A. Spadaro (talk) 13:09, 24 December 2013 (UTC)

In Windows 7 you do right click with your mouse, choose "Gadgets" on the drop down menu, a window with various gadgets will appear, you just choose what you like, a clock and the calendar are there. They are all nice looking gadgets. I do have a laptop with Windows 8, I may check it out later to see if the gadgets are built in over there as well. Cannot do it now since I am at work.--AboutFace 22 (talk) 21:03, 24 December 2013 (UTC)

Gadgets have been removed from Windows 8.x.[1] A Quest For Knowledge (talk) 21:50, 24 December 2013 (UTC)

Does Windows 8 still have batch files?

@echo off
:start
echo %time%
echo %date%
ping 127.0.0.1>nul
cls
goto start

82.44.76.14 (talk) 22:01, 24 December 2013 (UTC)

Yes, Windows 8 still have batch files, and the script above does work. However, I think the OP is looking for a Metro (aka Modern aka Windows Store) app, not a console app. A Quest For Knowledge (talk) 22:41, 24 December 2013 (UTC)

Stardock has some great features but you don't need it for a clock. Stardock sends you to Wincustomize for themes and gadgets. I saw your question yesterday and spent some time looking at the gadgets section, which seem to be independent of Stardock. I didn't find anything that was really useful. In the end I got Desktop gadgets and sidebar for Windows. Installed it, pulled the clock off the bar and hid the bar. CambridgeBayWeather (talk) 01:00, 25 December 2013 (UTC)

The Windows 8 desktop already displays the date and time in the task bar on the desktop. I suspect that the OP is asking about the Metro interface. A Quest For Knowledge (talk) 05:09, 25 December 2013 (UTC)

Hello, again. And thanks to all. I am not that computer- or tech-savvy, so I did not understand much of the computer lingo/jargon above (although, I think that I got the gist of it). What I am looking for is a "tile" (a "live" app tile) that one places on the Start page of Windows 8.1 ... similar to all the other tiles that are already placed there (e.g., a tile for Internet Explorer, a tile for America Online, a tile for Netflix, etc.). In other words, those little rectangular boxes that appear on the Start page. I am seeking a tile that displays the date and time ... and updates them continually, so as to have the current date and time. I am aware of the small display of the date/time located on the lower right-hand side of the task bar. I want something visually larger. Thanks! Joseph A. Spadaro (talk) 16:26, 25 December 2013 (UTC)