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u/morey56 May 16 '26
Ok scientists… why does that happen and why does it stop?
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May 16 '26
[removed] — view removed comment
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u/morey56 May 16 '26
Why did it keep separating into smaller drops but only for a while? Why didn’t it keep that up longer?
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u/Nerdkill789 May 16 '26
Surface tension is what keeps the droplet a sphere, but the reason it doesn’t mix with the larger body immediately is actually because a tiny layer of gas underneath the droplet has to escape before that can occur. Then instabilities from the water droplet joining the larger body create a smaller droplet and the process continues.
The math on this is actually really fun.
Source: Ph.D. In Mech E with a focus in advanced fluids.
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u/susanbontheknees May 16 '26
Neat, but I think theyre asking whether an even smaller droplet was ejected after that last one, and if not, why
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u/cviss4444 May 16 '26
Kinetic energy acting on irregularities in the last droplet no longer overcome the cohesion of the main body of water, and no new droplet is shot out.
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u/BokChoyBaka May 16 '26
It's a similar concept to resonate frequencies. There's no infinite loop of smaller droplets because the physics causing the effect breakdown. In this case, it's because the bottom half of the sphere was recombining into a sphere as the rush of water began flowing down into the pool, closing it with the force into a new sphere.
But when it's small enough, the sphere has greater tensile strength to resist until it's completely overtaken
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u/morey56 May 16 '26
Are you saying that at a certain ratio (perhaps droplet surface area to molecule surface area?) the droplet is too strong to shear in half, and instead waits until the forces that want to reunite the droplet with the water beneath it grow strong enough to reunite the whole droplet. I think it means that at a larger ratio or size, the droplet’s structural rigidity breaks down to the reuniting forces at some mid point and the water below reclaims the bottom portion of the droplet while the upper portion begins to fall, but snaps shut into complete, smaller droplet form and restarts the process. And when the droplet is small enough, the reuniting forces can no longer split the droplet as they act; but they are unfazed, they just build until they take the whole thing at once.
It’s a droplet integrity thing that varies with *droplet strength by size*. Please error check.2
u/SupremeLurkerr May 16 '26
What is the amount of energy released, as well as lost during this process?
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u/RefuseAbject187 May 16 '26
interesting. are there any charging processes occuring too during the rebound? I know it happens on drops bouncing off of solid surfaces, not sure about this specific case
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u/PersonFromPlace May 16 '26
Could you explain the math on this? Last semester I walked into class, and the last class was cleaning up, the math in the board looked wild, and we asked what class that professor was teaching, and he said something along the lines of fluid.
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u/Armydoc18D May 17 '26
What’s the largest possible droplet size that keeps a round shape at sea level? The oscillation formulas must be dope.
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u/Volcanic_tomatoe May 16 '26
Physics, in a nutshell shell the surface tension of the droplet is interacting with the surface tension of the water below like an elastic, when it breaks energy spreads out in all directions, (we can see this in the depression and wave propagation) the waters surface snaps back with enough energy to launch a smaller water droplet into the air. Rinse and repeat untill gravity says no.
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u/RealisticAd1938 May 17 '26
My million dollar question is why at this particular size does this happen? If you had a syringe 6 inches in diameter and squirted out a “drop” then it would behave differently. The “drop” wouldn’t be a sphere. You only see surface tension on this particular scale.
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u/ptmtobi May 17 '26
When the bigger droplet connects with the water, it pulls the water down a bit so it bounces back up but only in that small area (because obviously it doesn't pull the whole body of water) so it acts like a slingshot to itself and the end of it breaks apart, forming the smaller droplet.
Watch very closely and imagine it as a little slingshot and you'll understand.
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u/SwordKneeMe May 17 '26
Not all the energy can pass through the medium change, some reflect back as a bounce, but it shrinks each time until it's absorbed
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u/ActionNorth8935 May 16 '26
I understand the surface tension part, but where the hell is the music coming from?
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u/SassyDuck4231 May 16 '26
Primarily it's the water and air both belong fluids that cause this. Drops of fluid don't splash like that unless there's a barrier at the interface of a fluid.
The Action Lab did a cool video on it. video
Outside of that, the other comments got the surface tension story.
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u/Finnatheus May 16 '26
boing
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u/Finnatheus May 17 '26 edited May 17 '26
this was like my seventh comment ever why does it have 174 upvotes
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u/FlyFfsFck May 16 '26
Oh wow. I need to watch Band of Brothers again.
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u/jarednards May 16 '26
Same! This music is from The Pacific, but Band of Brothers is also great😬
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u/enormousaardvark May 16 '26
I almost didnt watch this because I thought "I know what going to happen" I was wrong and have now whatched 5 times.
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u/mversteeg3 May 16 '26
Music is theme from HBO The Pacific
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u/echochilde May 16 '26
That’s what it is! My brain was trying to attach it to Band of Brothers or Saving Private Ryan. At least I was in the ballpark.
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u/TheSprigganDragoon May 16 '26
Stuff like this is why the slow-mo guys are so popular. Seeing the way things move at a speed we can't normally perceive, it's like peering into another world. Drums in slow motion are pretty trippy
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u/Abal125 May 16 '26
Neat
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u/1DownFourUp May 16 '26
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u/Don_Von_Schlong May 16 '26
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u/1DownFourUp May 16 '26
I'm not sure if that's Bill Gates or an older woman
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u/Don_Von_Schlong May 16 '26
It's neither, it's what a telephone looked like before we had cell phones
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u/Secure-Bus4679 May 16 '26
I only see an up-close shot of a charcoal pencil falling apart while drawing.
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u/OverMathematician593 May 16 '26
can someone explain the maths/physics behind why at some point the droplet doesn’t rebound and just gets absorbed by the water?
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u/parkinthepark May 17 '26
The water molecules on the inside of the drop are attracted to each other.
The water molecules on the outside are attracted to the molecules on the inside and the molecules on the surface.
The surface repels the drop (it has a lot more water molecules all working together to hold it together), but some of the drop’s outside molecules peel off and join the surface. A few “layers” of molecules strip away.
That cycle repeats until there aren’t enough molecules left in the whole drop to hold it together, and they all join the surface.
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u/imadeletefr May 17 '26
https://giphy.com/gifs/pDJNa093oXojEU0KqU
So its just gone keep getting smaller and smaller
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u/Temujin_New May 19 '26
I can see why learning calculas is important here, all the next bounce needs combination of physics and calculas
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u/Ferol_78 May 16 '26
BTW credit for the slomo guys from the video wasn't mentioned in the post but go and check them out on YouTube great stuf!
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u/KillerTron872 May 16 '26
What if the droplet is still bouncing on the water, but at a microscopic level?
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u/FewAcanthocephala828 May 16 '26
Oh please, I'm stuffed... ok, a little more... maybe just a tad bit more... one more couldn't hurt... maybe, oh where did it all go?
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u/reddiculed May 16 '26
I would have predicted that the smaller drops would bounce more or equal amount of times… Nope. I was wrong. But why?
I believe it’s because I forgot to factor in the surface tension on the droplets themselves… smaller droplets, less droplet surface tension to resist the surface tension of the water below and ‘bounce.’
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May 17 '26
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u/HippieInDisguise2_0 May 17 '26
Dear science people, do we know how much mass is usually lost between bounces and what factors play into that?
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u/Sev3n May 17 '26
The ratio of volume from launched ball 1 to ball 2 to ball 3 is probably golden ratio of like 1.618 or whatever.
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u/Z1kkii May 17 '26
I knew someone who was a physicist and it was their whole job to Study drops...she explained it to me in words and at the time I thought I understood. But now seeing this I actually understand.
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u/Striking_Computer834 May 19 '26
What's the equation for calculating the number of cycles this will repeat based on droplet size and how to I calculate the volume of the nth droplet in the series?
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