Why are man hole covers round?
Answers by e-mail. I'll post the funny ones.

Hehe, you like this kind of things don't you myork? :D I'll disqualify myself from answering as I've read both serious, semi-serious, and not so serious answer from more than one source to this and similar questions before.

Hope you get some funner answers. :)

I read why on wiki
but my first guess before that was cause its simple and a persons head is roundish :lol:

My first thought was a reduction against elemental damage (over time) by having no corners. Then i reconsidered the concept of a 'Man-hole' and laughed a bit..
Then i thought...No..the man holes are square where im at!.

Then the question is, why are most manholes in this world round? Serious and less serious answer's both accepted. ;)

Ok. This is what I heard.
1) It is easier to move (you can roll it). [But that is only a bonus answer]
2) The main reason is safety.

You can not drop a round cover down a round hole. NB the hole will always have a slightly smaller diameter than the cover.

Any other shape can be turned so that it is possible to drop the cover down the hole.
Consider a square. Take the cover off. Hold it vertically across the diagonal of the hole and accidentally let it slip. The same is true for all shapes. The fit becomes tighter and tighter as the number of sides increase but becomes imposable when we have infinite sides.

A couple of people got the bonus, but nobody got the safety.

:blink: :blink: I would have expected the result to be the opposite.

"That's easy. In a fight, a round shield is better than a square one. The circle is also a symbol of infinity, which is why church domes are also round. The principle of 'as above as below' reminds pedestrians that they live in a divine world." - Andrei Codrescu, during Q&A after a talk at Microsoft. :lol:

Couple of interesting books:
How Would You Move Mount Fuji?: Microsoft's Cult of the Puzzle
Programming Interviews Exposed