It’s a little disappointing the tablet didn’t fizz like crazy and make the drop inflate super fast and explode, but actually this makes perfect sense in zero gravity. /1
2/ Everywhere the water touches the tablet it will make gas bubbles. Gas is lower density than water, so in Earth’s gravity it weighs less, so the gas rises to the top. Archimedes Buoyancy!
3/ Since the bubble leaves the surface of the tablet, this makes room for new water to touch that part of the tablet. So more gas is made, and the process repeats like mad!
4/ But in zero gravity weightlessness, there is no force to pull water down under the bubble forcing the bubble up. So the bubble can just stay where it is, attached to the tablet. This keeps new water from touching the tablet, so no more gas is made. The process quickly stops ☹️
5/ But it is cool to see how things are so different without gravity! We are still trying to understand all the processes in our bodies that rely on gravity for optimum operation.
6/ Interesting! I will guess it is not a “drip” but rather is an ejection where the energy of internal waves re-converged. We see similar events in splashes in 1-g.These hypothesized waves might have been caused by the tablet entering into the drop. .
7/ Here is the ejection event where a smaller drop suddenly flew out of the bigger one. It is at 23 seconds in the video at the top of the thread. 
8/ Here is an example of it happening in gravity. In this case, the inertia of a drop makes a crater in the water, so when water rushes back in to fill the crater it crashes in the center and ejects a drop upwards.
9/ This happens in rock, too. Here is Tycho crater on the Moon. An asteroid hit the Moon. Rock flowed back in to fill the crater. It converged in the center and shoved up the central peak. But then the rock “froze” in place, so this splash of rock is forever captured in the act.
10/ These central rebound splashes in both water & rock happen because gravity determines the “down” direction, and there is free surface between the water (or rock) and the open space above it. In zero-g it isn’t the same. With no up or down the water pulls itself into a sphere.
11/ But the drop was ejected out a particular side of the sphere. What broke the symmetry? I think the act of sticking the tablet in the drop imparted both linear and rotational inertia to the drop in the form of asymmetric acoustic waves inside it.
12/ Here is a case where astronaut Don Pettit induced more symmetric waves into a droplet, maintaining symmetry across a left-to-right axis. You can see the waves reverberate back and forth, never quite converging sharply enough to eject a droplet.
13/ Here’s a case where the “impact” was sharp enough to immediately eject a large drop.
14/ And by the way, this is relevant to protecting Earth from asteroid impact. Momentum is *always* conserved. The puff of air has momentum going to the right. All that momentum goes into the drop. But the drop ejects a drop in the WRONG direction. So how is momentum conserved?
15/ In these cases you can’t see it because the thin metal rod is holding the water drop in place, so it stays in front of a camera. But absent the rod: (1) the puff makes the water move right, then (2) the ejecta that shot left makes the water move even faster right!
16/ So the total momentum that the water blob obtains is MORE than the momentum that the puff of air originally had. The splash that went back toward the impact AMPLIFIES the momentum of the impact. We call this amplification factor the “beta” of the impact.
17/ When we plan to knock an asteroid off its course so it will miss the Earth instead of wiping us out, we will take advantage of this beta. Our kinetic impactor that hits the asteroid may not have enough momentum to save the Earth, but with the momentum of the splash it might!
18/ To read more about this beta, here is a paper: pdf.sciencedirectassets.com/278653/1-s2.0-…
19/ The physics of this is relevant to more than deflecting asteroids. Destin of @smartereveryday shows how science can help us manage the dreaded “poop splash”.
