# Liquid moving in helix **URL:** \ **Category:** Factual Questions\ **Created:** [August 12, 2017, 9:17am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424 "2017-08-12T09:17:40Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Kavaj](https://avatars.discourse-cdn.com/v4/letter/k/b9bd4f/32.png) [@Kavaj](https://boards.straightdope.com/u/Kavaj)\ **Post date:** [August 12, 2017, 9:17am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/1 "2017-08-12T09:17:40Z")
Is there a way to make a stream of liquid move so that it describes a helix rather than a straight line or arc? That is to say, the liquid keeps “turning” after leaving the hose or whatever you’re squirting it out of. I think it’s impossible to impart momentum on a liquid in such a way but my girlfriend insists that her ex always urinated in a double helix pattern, two streams basically describing a DNA molecule. Can we figure out exactly what was wrong with his penis or conclude that all three witnesses to this were really drunk? ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [August 12, 2017, 10:07am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/2 "2017-08-12T10:07:06Z")
To accurately describe a DNA molecule, the two streams would have to be anti-paralel–one stream would have to be moving out from his penis to the toilet while the other stream would have to be leaping out of the toilet into his penis. Let’s hope that wasn’t happening, because I don’t want to live in a world where that happens. ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [August 12, 2017, 10:32am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/3 "2017-08-12T10:32:46Z")
And no one thought to video it? ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [August 12, 2017, 10:37am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/4 "2017-08-12T10:37:45Z")
Was your girlfriend’s ex a duck? ---
**Author:** ![Kavaj](https://avatars.discourse-cdn.com/v4/letter/k/b9bd4f/32.png) [@Kavaj](https://boards.straightdope.com/u/Kavaj)\ **Post date:** [August 12, 2017, 11:10am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/5 "2017-08-12T11:10:31Z")
> [@Darren\_Garrison](#): > > To accurately describe a DNA molecule, the two streams would have to be anti-paralel–one stream would have to be moving out from his penis to the toilet while the other stream would have to be leaping out of the toilet into his penis. > > Let’s hope that wasn’t happening, because I don’t want to live in a world where that happens. That was indeed not happening. Both streams went penis-to-toilet but curling around each other like the shape of a DNA molecule. > [@bob\_2](#): > > And no one thought to video it? I just asked, and apparently not. ---
**Author:** ![Ignotus](https://avatars.discourse-cdn.com/v4/letter/i/ecc23a/32.png) [@Ignotus](https://boards.straightdope.com/u/Ignotus)\ **Post date:** [August 12, 2017, 11:30am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/6 "2017-08-12T11:30:12Z")
Not a helix, but when I open my kitchen tap just a little the first few inches of the stream will look something like this: () () () () So weird things can evidently happen with streaming water. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [August 12, 2017, 11:43am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/7 "2017-08-12T11:43:28Z")
If he has two dick holes, and it could rotate smoothly in one direction or another, like a sprinkler head, sure, it could work. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [August 12, 2017, 12:20pm UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/8 "2017-08-12T12:20:26Z")
**Ignotus** ’s diagram is only 2-d. But you can get a 3-d version of that from liquid forced out a slit. It’s hard to “draw” the effect here. It looks like **Ignotus** ’s diagram from both the front and the side, but the side one is shifted in phase. So it can sort of look like, be very approximately described as, a “helix” but it really isn’t. The liquid wants to go from flat to circular, so it pulls towards the center but overdoes it and squishes out to flat again but in the opposite plane. The oscillating pattern is a result of this process starting on exiting like other wobbles in a stream. A true spiral as in the OP can’t happen due to good old Newton’s laws without adding forces. E.g., the stream has a strong negative charge and there’s a heavily oppositely charged wire running thru the middle. Or an strong push of air from the outside that can somehow be drawn out thru the middle. Maybe a perforated tube in the middle attached to a vaccuum? Etc. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [August 12, 2017, 12:42pm UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/9 "2017-08-12T12:42:38Z")
> [@ftg](#): > > **Ignotus** ’s diagram is only 2-d. But you can get a 3-d version of that from liquid forced out a slit. > > It’s hard to “draw” the effect here. It looks like **Ignotus** ’s diagram from both the front and the side, but the side one is shifted in phase. > > So it can sort of look like, be very approximately described as, a “helix” but it really isn’t. > > The liquid wants to go from flat to circular, so it pulls towards the center but overdoes it and squishes out to flat again but in the opposite plane. The oscillating pattern is a result of this process starting on exiting like other wobbles in a stream. > > A true spiral as in the OP can’t happen due to good old Newton’s laws without adding forces. E.g., the stream has a strong negative charge and there’s a heavily oppositely charged wire running thru the middle. Or an strong push of air from the outside that can somehow be drawn out thru the middle. Maybe a perforated tube in the middle attached to a vaccuum? Etc. This is what I was thinking of too. For a very small stream, the surface tension pulls the flat-ish oval stream to circular, but over-does it; so the liquid then becomes an oval cross-section at 90 degrees to the start of the stream. It might oscillate between cross sections like this a couple of times before it degenerates into a ragged fragmented stream. I’m guessing this effect is caused by surface tension and only happens in small scale streams. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 12, 2017, 12:51pm UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/10 "2017-08-12T12:51:20Z")
Most men _do_ urinate in the shape of a gravitational wave (as described by other posters above), and it would be very easy for a casual or distracted observer to mistake that for the shape of a DNA molecule. ---
**Author:** ![Kavaj](https://avatars.discourse-cdn.com/v4/letter/k/b9bd4f/32.png) [@Kavaj](https://boards.straightdope.com/u/Kavaj)\ **Post date:** [August 21, 2017, 3:20am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/11 "2017-08-21T03:20:56Z")
I have obtained a video - my girlfriend’s relationship with her ex is somewhat weird - and it looks exactly like what ftg and md2000 describe. Still strange to me but at least not physically impossible. Thanks! ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [August 21, 2017, 11:55am UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/12 "2017-08-21T11:55:40Z")
There’s also [this sort of effect](https://www.youtube.com/watch?v=UOfAmsQvgg4), but that wouldn’t be visible unless you had a strobe light in your bathroom. ---
**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:** [August 21, 2017, 12:46pm UTC](https://boards.straightdope.com/t/liquid-moving-in-helix/793424/13 "2017-08-21T12:46:05Z")
> [@ftg](#): > > A true spiral as in the OP can’t happen due to good old Newton’s laws without adding forces. I think it’s probably possible to have a weakly rotating spiral stream (that is, flattened or at least not circular in cross section at any point, but twisted along its length) - as long as the forces of cohesion in the fluid are not overcome by the centrifugal force of the rotation.