We are not sure yet! Some evidence has been put forward by Humphrey Maris, professor of physics at Brown University. This evidence mostly comes from interpretations
of old experiments and it suggest that a bubble containing a single electron in liquid helium can be split into two bubbles with the help of infrared light. More experiments are under way so we may know for sure if this is true or not.
Here is the press release copy from Brown University about this:
In a paper published Aug. 1, 2000 in the Journal of Low Temperature Physics, Humphrey Maris, professor of physics at Brown University, proposes that under suitable conditions electrons can undergo a form of fission. He has also discovered there is a significant amount of experimental evidence supporting his theory.
Physicists consider that matter in the world is composed of a large number of elementary particles. Some of these particles, such as the electron and the proton, carry an electric charge, while others, including the neutron and neutrino, are electrically neutral. Although some elementary particles can decay into other particles, it has been regarded as a general principle of physics that an elementary particle cannot be broken into two pieces. Thus, for example, although a neutron can decay into a proton plus an electron and a neutrino, it can never be broken into two half neutrons.
According to quantum theory, the state of a particle is described as its wave function. The probability that the particle will be found in any position is proportional to the square of the wave function at that point in space. Maris' theory considers what happens to electrons when they are immersed in liquid helium at a temperature of one degree above absolute zero. Previous experiments have shown that an electron in helium becomes trapped in a bubble approximately 100-billionths of an inch in diameter. The bubble drifts through the liquid with the wave function of the electron confined inside it.
Maris shows that when the bubble is illuminated with infrared light, the bubble can divide into two smaller bubbles each containing a part of the wave function of the electron. These two bubbles can then move independently through the liquid and become separated from each other.
In the 1970s, researchers at Bell Laboratories and the University of Michigan performed experiments on the effect of light on electrons in liquid helium. These researchers were unable to explain their surprising results. Maris realized that these old experiments, together with more recent measurements made at the University of Lancaster, could be understood in terms of his theory and provided support for his ideas.
Further experiments to test the theory are under way at Brown University in work supported by the National Science Foundation.
Answered by: Anton Skorucak, M.S. Physics, PhysLink.com Creator
(news release reprinted from: Brown University)
'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '