LOS ANGELES — Brian Kappus, a physics graduate student at U.C.L.A., tipped the clear cylinder to trap some air bubbles in the clear liquid inside. He clamped the cylinder, upright, on a small turntable and set it spinning. With the flip of another switch, powerful up-and-down vibrations, 50 a second, started shaking the cylinder. A bubble floating in the liquid — phosphoric acid — started to shine, brightening into an intense ball of light like a miniature star. The shining bubble did not produce any significant energy, but perhaps someday it might, just like a star. A few small companies...