The universe consists mostly of dark matter which is completely invisible. But almost all the visible matter in the universe is in the plasma state. Formed at high temperatures, plasmas consist of freely moving ions and free electrons. They are often called the “fourth state of matter” because their unique properties distinguish them from solids, liquids, and gases. Everyday examples of plasmas include plasma columns in neon tubes, electric sparks, and the plasma filament in a lightning flash. Outside the Earth, we have the Sun, which is essentially a giant ball of superheated plasma gas.

It turns out that what goes on in the Sun holds vital clues to the evolution of galaxies, including our own galaxy, the Milky Way. Consider the interaction between stars. According to Newton’s law, two stars that each have mass m in a galaxy attract each other with a gravitational force , where r is the distance between them. Meanwhile, a plasma is like a hot fizzing soup of electrons and ions like those swirling in the Sun. Two electrons a distant r apart will repel each other with an electric force , where e is the electron charge.

Seeing double? The similarities between these two equations mean that, with some modifications, one can think of a galaxy as a “gravitational plasma”, governed by the same laws that govern the behavior of plasma.

There’s more. Scientists at the Lawrence Livermore National Laboratory in California have recently discovered that laser-induced plasmas, when directed at each other at high speed, can give rise to “self-organized” electromagnetic fields like those found throughout the universe. This discovery solves one of the great mysteries of astrophysics, which is how highly organized structures like magnetic fields stretching millions of light years can emerge from the frenetic motion of plasma streams.

No doubt, scientists will discover more connections between plasma and the universe in the future. These connections are a beautiful example of how nature uses broadly similar laws to organize seemingly disparate phenomena. The discoveries are spurring the development of new mathematical models of the universe modified from equations that describe the behavior of electrons and ionized gases. If nature is what we think she is, the two sets of equations – one in plasma physics and the other in astrophysics – are likely to be substantively the same. And that is beautiful indeed.