Helium, when reduced to -269 degrees Celsius (2.17 degrees above absolute zero, the coldest temperature attainable) becomes a liquid. When brought down even further it becomes a "super-fluid" that can flow without friction, squeeze through impossibly small holes, and even run up hills. Another interesting property of liquid helium is the formation of "electron bubbles". This occurs when electrons are sent through the liquid helium. Helium atoms have a full complement of electrons, and are therefore unable to hold any more, and the electrons just stop in the space between atoms. Due to its negative charge, the electron repels the full, neutral helium atoms and creates an empty bubble in the liquid, which is about ten thousand helium atoms large.

When the electrons are in the bubble only certain wave functions (the likehood of an electron being in any one place at a given time) are acceptable because only certain shapes can conform to the bubble. The most common one is the spherical shape, which corresponds to the lowest energy level. But by shining a laser on the liquid helium, it is possible to excite the electron into the second energy level, which has a dumbbell shaped wave function.

Humphrey Maris of Brown University discovered that when the temperature was dropped below 1.7 kelvins (a scale based with absolute zero as zero) the liquid became so runny, that the dumbbell shape actually hammered away at the edges forming a long thin neck between the two halves until it actually split. This means the electron wave function had broken into two half electron functions, which according to quantum theory meant the electron itself was broken in two. The electron had been divided. If it is ultimately proven true, that electron wave functions are electrons, then it proves that all matter, ourselves included, are merely wave functions. As for now Maris has been unable to determine the properties of the "half-electron", but believes it is doubtful they could form naturally.

Taken from "The Universe Next Door:The Making of Tomorrow's Science" by Marcus Chown.