Plus: Why cyphers are tougher to crack than codes; Why were there no black riders in the Tour de France?
How on earth do nettles benefit from stinging us? What's in it for them?
Surely nettles sting to dissuade herbivores and omnivores like us from eating them. You can eat them, though, if you boil them first, though picking them can be painful and they taste like flannel.
John Baker, Cambridge
Why should nettles take us into consideration at all? Humans are not the focus of the natural world and it isn't all about us. Nettles benefit from stinging because it keeps most animals away, and thus they remain uneaten and their pollinating insects unhindered.
Bees don't take us into consideration either, although, unfortunately, this has worse repercussions on them than on us. The barbed sting of a honeybee does not lodge in the body of other insects, the purpose for which it evolved long before there were mammals such as us with our flexible skin, in which the sting lodges – with fatal consequences for the poor bee.
Alexandria
Why are there no black riders in the Tour de France?
Because Frodo destroyed the One Ring.
johnofoxford
Perhaps because, so far, there hasn't been a black rider with the natural talent, the opportunity, and the absolute dedication to the sport to make it to the highest level.
Lottery money is helping create the opportunities, and the talent is out there, but a future black maillot jaune will have to have chosen cycling over other sports at which he could excel, with greater rewards (football, athletics, basketball). A role model might help. Just as Arthur Ashe was the first top black (male) tennis player and inspired others, perhaps somebody like Grégory Baugé will inspire other black track cyclists, who might then follow the likes of Mark Cavendish on to the road.
WenlockonEdge
There was a black cyclist competing in the Tour de France this year – Yohann Gene, who rides for Team Europcar.
stuart10
Any answers?
If Jesus came back, would he be a Christian?
nattybumpo
In south-east Asia a rain man is paid to avoid important afternoon events being ruined by the usual downpour. Worth a try?
Jenny Moir, Chelmsford
Why is there never enough time?
David Parlett, London SW16
• Post your questions and answers below or email nq@guardian.co.uk (please include name, address and phone number).
We know about the Enigma coding machine the Germans used in the second world war. What system did the allies use and did the Germans break it?
I was interested in the point that the German naval cypher group failed to crack Typex after six weeks and concluded that the extra wheel made the system unbreakable (N&Q, 19 July). We know that in February 1942 the Germans introduced a fourth wheel to the Enigma machines used by U-boats, and from then on Bletchley Park was unable to break their codes until that December – after which "cribs" from weather and position reports (still being encrypted on the old three-wheel machines) and the development of the Bombes enabled Hut 8 to read all German naval keys for the rest of the war. Is it possible that the Germans' failure to crack Typex convinced them that naval signals encoded on the four-wheel Enigma would be equally "unbreakable"?
John Taylor, Burton upon Trent, Staffs
Colossus (N&Q, 19 July) was a machine for breaking the Lorenz cypher of the German high command; it had nothing to do with Enigma. So you wouldn't use it for breaking Typex.
Peter Jarvis, Bletchley Park, Bucks
The Germans did indeed break British codes, but did not break British cyphers. A code works on words or phrases – the word "British" might be encoded as 279 – and is based on a codebook, which has one or more entries for each word. A cypher works on letters – the word "British" might be enciphered as 4720941. Note that in my made-up example the "i"s are not enciphered to the same number and the decipherment of 4 is "B" at one position and "s" at another position.
Everyone broke everyone's codes at the time. At Bletchley Park, a young man called Roy Jenkins worked on Japanese codes – he later became a famous politician. Codes are relatively simple to break and are best attacked by people such as chess players and crossword solvers. Cyphers are a lot more difficult and are best attacked by mathematicians and engineers.
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