# Human diode **URL:** \ **Category:** In My Humble Opinion\ **Created:** [February 16, 2010, 4:29am UTC](https://boards.straightdope.com/t/human-diode/529168 "2010-02-16T04:29:24Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [February 16, 2010, 4:29am UTC](https://boards.straightdope.com/t/human-diode/529168/1 "2010-02-16T04:29:24Z")
How would you design a hallway such that any number of people can walk from one end to the other, but only in one direction? You can use any amount of doors and mechanisms and so forth, but only purely mechanical things. No electronics or other modern technology. We’ll assume that whatever you come up with can be built strongly enough to resist tampering and brute force. ---
**Author:** ![Snarky\_Kong](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@Snarky\_Kong](https://boards.straightdope.com/u/Snarky_Kong)\ **Post date:** [February 16, 2010, 4:30am UTC](https://boards.straightdope.com/t/human-diode/529168/2 "2010-02-16T04:30:33Z")
A couple of large paddlewheels that form the walls and can only turn one way. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [February 16, 2010, 4:42am UTC](https://boards.straightdope.com/t/human-diode/529168/3 "2010-02-16T04:42:54Z")
Turn style at one end (or multiple turn styles down the hallway) Also, just having multiple doors that are locked from one side. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [February 16, 2010, 4:49am UTC](https://boards.straightdope.com/t/human-diode/529168/4 "2010-02-16T04:49:11Z")
The standard solution is the [turnstile](http://en.wikipedia.org/wiki/Turnstile). Does that not fit your requirements? ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [February 16, 2010, 4:52am UTC](https://boards.straightdope.com/t/human-diode/529168/5 "2010-02-16T04:52:18Z")
Well it’s pretty easy to jump over a turnstile. ETA: Although the full-height kind could certainly work. That still allows the passing of small objects through the bars, so it’s not ideal for my nefarious purposes, but they certainly stop humans. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [February 16, 2010, 4:53am UTC](https://boards.straightdope.com/t/human-diode/529168/6 "2010-02-16T04:53:17Z")
Hmmm. How about this. A hallway has a door at each end. The entrance door cannot be opened if there anything in the hallway ( the weight of any people inside the hall triggers a latch holding it shut ). The exit door cannot be opened if there is no one inside the hall, due to a similar latch. ---
**Author:** ![Spectralist](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Spectralist](https://boards.straightdope.com/u/Spectralist)\ **Post date:** [February 16, 2010, 5:01am UTC](https://boards.straightdope.com/t/human-diode/529168/7 "2010-02-16T05:01:47Z")
Is walking necessary or just getting through the hallway? If the latter I’d say a steep heavily greased slide. Or even a water slide. I know there are methods of making fountains that predated electricity presumably they could be adapted for this use if the location is suitable. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [February 16, 2010, 5:12am UTC](https://boards.straightdope.com/t/human-diode/529168/8 "2010-02-16T05:12:01Z")
A really fast running river? A log ride? A fifty foot fall? Dammit I pondered too long. ---
**Author:** ![cornflakes](https://avatars.discourse-cdn.com/v4/letter/c/9d8465/32.png) [@cornflakes](https://boards.straightdope.com/u/cornflakes)\ **Post date:** [February 16, 2010, 7:22am UTC](https://boards.straightdope.com/t/human-diode/529168/9 "2010-02-16T07:22:41Z")
A very short hallway, barely more that a door’s width long, and with doors at either end that open only in the direction of travel. This won’t prevent people from traveling against the flow, but it would be a strong suggestion. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [February 16, 2010, 12:12pm UTC](https://boards.straightdope.com/t/human-diode/529168/10 "2010-02-16T12:12:55Z")
A large number of very sharp spikes arranged on sprung hinges. They point in the direction travel is allowed (like barbs.) When people walk in that direction the spikes give way, when people walk in the opposite direction they die. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [February 16, 2010, 12:44pm UTC](https://boards.straightdope.com/t/human-diode/529168/11 "2010-02-16T12:44:17Z")
[quote=“1920s Style “Death Ray”, post:10, topic:529168”] A large number of very sharp spikes arranged on sprung hinges. They point in the direction travel is allowed (like barbs.) When people walk in that direction the spikes give way, when people walk in the opposite direction they die. [/QUOTE] Hmmmm, sounds like a Monty Python sketch [![](https://i.ytimg.com/vi/e2PyeXRwhCE/hqdefault.jpg "Monty Python- Architect Sketch") ](https://www.youtube.com/watch?v=e2PyeXRwhCE) ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 16, 2010, 1:00pm UTC](https://boards.straightdope.com/t/human-diode/529168/12 "2010-02-16T13:00:39Z")
Build the hallway inside the event horizon of a black hole. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [February 16, 2010, 1:02pm UTC](https://boards.straightdope.com/t/human-diode/529168/13 "2010-02-16T13:02:13Z")
They have this at subway stations here in Boston, at the zoo, and at the doors of two companies I’ve worked at – there are “turnstiles” that consist of revolving-door-type constructions that run from floor to ceiling, but instead of glass panels they have a “wall” of rigid horizontal rods connected to the central rotating post, forming a plane. The center post can only rotate in one direction. You can go one way through the stile, but you can’t make it rotate to go the other way. And you can’t “follow” the stile around to go backwards because there is a “wall” of similar rigid pipes forming a stationary plane that blocks your progress. The rotating rods can pass through this stationary plane, however, because their bars interleave with the stationary ones. ---
**Author:** ![Rocketeer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rocketeer/32/4437_2.png) [@Rocketeer](https://boards.straightdope.com/u/Rocketeer)\ **Post date:** [February 16, 2010, 2:51pm UTC](https://boards.straightdope.com/t/human-diode/529168/14 "2010-02-16T14:51:18Z")
Make the hallway vertical, with people entering at the upper end. 😉 ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [February 16, 2010, 5:39pm UTC](https://boards.straightdope.com/t/human-diode/529168/15 "2010-02-16T17:39:12Z")
[QUOTE=Rocketeer;] Make the hallway vertical, with people entering at the upper end. 😉 [/QUOTE] We have our winner! ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [February 16, 2010, 5:48pm UTC](https://boards.straightdope.com/t/human-diode/529168/16 "2010-02-16T17:48:31Z")
Place delicious donuts at the end you want people to head towards. ---
**Author:** ![smithsb](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smithsb/32/12107_2.png) [@smithsb](https://boards.straightdope.com/u/smithsb)\ **Post date:** [February 16, 2010, 8:02pm UTC](https://boards.straightdope.com/t/human-diode/529168/17 "2010-02-16T20:02:20Z")
> [@Really\_Not\_All\_That\_Bright](#): > > Place delicious donuts at the end you want people to head towards. ooh ooh … and pie … and bacon salt :)🙂 ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [February 16, 2010, 8:58pm UTC](https://boards.straightdope.com/t/human-diode/529168/18 "2010-02-16T20:58:02Z")
> [@Rocketeer](#): > > Make the hallway vertical, with people entering at the upper end. 😉 > [@Really\_Not\_All\_That\_Bright](#): > > Place delicious donuts at the end you want people to head towards. I think we could combine these for maximal effect. ---
**Author:** ![NicePete](https://avatars.discourse-cdn.com/v4/letter/n/ee7513/32.png) [@NicePete](https://boards.straightdope.com/u/NicePete)\ **Post date:** [February 16, 2010, 9:00pm UTC](https://boards.straightdope.com/t/human-diode/529168/19 "2010-02-16T21:00:24Z")
Two words: Chuck. Norris. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [February 17, 2010, 7:21am UTC](https://boards.straightdope.com/t/human-diode/529168/20 "2010-02-17T07:21:14Z")
> [@Rocketeer](#): > > Make the hallway vertical, with people entering at the upper end. 😉 > [@Really\_Not\_All\_That\_Bright](#): > > Place delicious donuts at the end you want people to head towards. > [@Sunspace](#): > > I think we could combine these for maximal effect. Put the donuts at the top, that way you’d have an anti-gravity machine. [Next page](https://boards.straightdope.com/t/human-diode/529168.md?page=2)