3 ms·

God bless the manhole cover problem. That's been making the rounds for over a decade.

alecco 16y ago
I don't like those problems. IMHO, they encourage rationalizing things that probably just evolved/happened over time. The real answer for me is because no better shape happened or showed to be significantly better. Also, since almost all follow the same shape, it's harder for other shapes to enter the market. Winner takes all.
- stcredzero 16y ago
  It's not arbitrary. "Because it can't fall in the hole" is a compelling geometric and safety reason. The circular manhole cover is the simplest shape that has this property.
  - notahacker 16y ago
    The reasons for making the access tunnel beneath cylindrical in shape are actually far more compelling (remove less material and create a stronger hole). Nevertheless, rectangular manhole covers are pretty common.
    - stcredzero 16y ago
      Nevertheless, rectangular manhole covers are pretty common. I never claimed the market was perfect. I find that perfect omniscient markets a terrible assumption to base analysis on. The combination of superior cover safety and superior tunnel structure are pretty compelling, but not everyone chooses the optimal solution. That's just not how humans operate.
EdiX 16y ago
God bless its resilience to all the non-round manholes around the world.
simonsarris 16y ago
Interestingly, in my city the manhole covers are equilateral triangles (Nashua, New Hampshire). http://farm3.static.flickr.com/2164/2377255702_fec42f19b2.jpg http://farm3.static.flickr.com/2164/2377255702_fec42f19b2.jp... If ever asked I would try to convince them of the triangular merits.
krschultz 16y ago
I had an interviewer who thought he was the only person using the round manhole cover question. When he asked it I instantly answered "so they don't fall in the hole" and he freaked out. "Wow, you are so smart, I've never had anyone answer that question so quickly!" I didn't have the heart to tell him its a cliche.

I don't like those problems. IMHO, they encourage rationalizing things that probably just evolved/happened over time. The real answer for me is because no better shape happened or showed to be significantly better. Also, since almost all follow the same shape, it's harder for other shapes to enter the market. Winner takes all.

stcredzero 16y ago
It's not arbitrary. "Because it can't fall in the hole" is a compelling geometric and safety reason. The circular manhole cover is the simplest shape that has this property.
- notahacker 16y ago
  The reasons for making the access tunnel beneath cylindrical in shape are actually far more compelling (remove less material and create a stronger hole). Nevertheless, rectangular manhole covers are pretty common.
  - stcredzero 16y ago
    Nevertheless, rectangular manhole covers are pretty common. I never claimed the market was perfect. I find that perfect omniscient markets a terrible assumption to base analysis on. The combination of superior cover safety and superior tunnel structure are pretty compelling, but not everyone chooses the optimal solution. That's just not how humans operate.

EdiX 16y ago

God bless its resilience to all the non-round manholes around the world.

simonsarris 16y ago

Interestingly, in my city the manhole covers are equilateral triangles (Nashua, New Hampshire). http://farm3.static.flickr.com/2164/2377255702_fec42f19b2.jpg http://farm3.static.flickr.com/2164/2377255702_fec42f19b2.jp... If ever asked I would try to convince them of the triangular merits.

krschultz 16y ago

I had an interviewer who thought he was the only person using the round manhole cover question. When he asked it I instantly answered "so they don't fall in the hole" and he freaked out. "Wow, you are so smart, I've never had anyone answer that question so quickly!" I didn't have the heart to tell him its a cliche.