[QUOTE=WF Tomba]
Now how wide were the trenches?
[/QUOTE]
About 6-10 ft wide, and about 8-12 ft deep, judging from most of the photos I’ve seen- there’s usually enough room to fix the bayonet to a rifle and still be able to move along the trench or climb over the top.
An SMLE or Mauser 98 with a bayonet fixed comes out at about 6’ in overall length, which is very unwieldy in a trench; soldiers going on trench raids used to prefer either just the bayonet (18" long for the Pattern '07 bayonet used by the British, and quite nasty in its own right), handguns (especially the .455 Webley and the Mauser C96), sawn-off shotguns (very popular with ANZAC troops, I’m told), and also entrenching tools with sharpened edges.
In short, there’s not a lot of room in the trenches, so I doubt individual trenches would be visible from space- the the trench system as a whole (stretching as it did from Switzerland to the English Channel) was quite wide (certainly more than 20m or so), and would be visible from orbit if you had some kind of Sopwith Space Shuttle to potter around in, avoiding orbital Archie barrages and wisecracking with Biggles, Algy, Ginger, and Bertie… 
[QUOTE=Zsofia]
Yeah, and no sound, either. People either wrote letters to each other, read newspapers, or waited for those title cards to come up after they spoke.
[/QUOTE]
Later on, after they invented sound, it turned out that a lot of people back then sounded like Blair Underwood when they read letters. 
More recently, it’s also been discovered that President Ulysses S. Grant had an e-mail address; President@anachronism.com.
Why yes, I did shamelessly steal that from Duckman, why do you ask? 