Since 1989, physicists have trapped a single micro-bubble in water with nothing but sound and watched it do something nobody fully understands: once per acoustic cycle it collapses and emits a flash of light shorter than 200 picoseconds, from gas hotter than the surface of the sun. They call it the star in a jar. The bubble's motion is textbook physics. The light — after 35 years of debate — still is not. Below: a live simulation of the real equation, a 3-D toy that shows the geometry, and at the bottom, the one number nobody ever measured — and our prediction for it, on the record.
What to watch. The faint sine is the sound. The bubble swells to ~30 µm, then crashes — ⚡ marks the flash. Then come the afterbounces: the bubble ringing down toward its resting size. Now watch the lower panel — the rebound amplitudes stepping down, bounce by bounce — and watch them get cut off: the next sound cycle seizes the bubble mid-settling, every cycle, forever. In 35 years of published experiments, the settling has never once been allowed to finish. The grey band marks what published data can resolve; the cyan line is our registered prediction (§3) — note it sits below everything ever measured. Press ✂ and the two possible futures draw themselves.
Watch the wave pattern build on the right. Hundreds of rays land, and the map lights up where they concentrate — that is the intensity, the actual pattern of light. Now try the three buttons; same packet, same throw, only the turn angle changes. At 40.000° the wave lands on itself — a handful of blazing spots, a fixed lattice, repeating forever. At 40.020° — two hundredths of a degree away — those spots smear into bright arcs before your eyes. At the golden angle (nature's favorite — how a sunflower packs its seeds) the energy never lands twice: a smooth luminous spiral, no lattice, no repeat. One angle decides whether a trapped wave concentrates into fixed hot-spots or spreads into a spiral — and shockingly little of it does. (Without the turn at all, the packet stays trapped in one flat ring: the turn is what fills the sphere.)
Digitize the canonical published curves (we did — sources below) and you can extract two numbers that, remarkably, appear nowhere in the literature as measured values: the bubble's per-bounce decay ratio ρ ≈ 0.74 and its rebound count N ≈ 12 before the next sound cycle interrupts. Run the arithmetic and something jumps out: at that decay rate, the settling needs about 21 bounces to finish — and the drive only ever allows about 12. Every experiment since 1989 has been structurally incapable of watching a bubble finish settling. Not for lack of skill — nobody thought the tail was where the story was.
So here is a falsifiable prediction, registered in advance. Cut the drive at the flash and let the ring-down run free. Textbook physics expects a featureless exponential decay, all the way down — no special amplitude, ever. We predict the settling terminates: the residual oscillation stops at roughly one twelve-hundredth of the initial throw — about 21 nanometers for the canonical bubble (≈40 nm in cold argon, where it settles three times faster). A plateau where the textbook says there is none. The apparatus that decides it is a tabletop: a standard single-bubble cell, a photodiode trigger, and a relay to kill the amplifier — parts, roughly $550. One number, two futures, and either answer is a real result.