The Fourth State of Matter

Plasma, the Fourth State of Matter

What is a Plasma?

Plasma is one of four states of matter. The other three states of matter are solid, liquid, and gas. The term "plasma" has nothing to do with blood plasma. Plasma, the least familiar state of matter to us here on Earth, is actually the most common form of matter in the universe. (photograph of an aurora, a plasma discharge in Earth's upper atmosphere, courtesy of David Fritts © 1995)

Plasmas Respond to Electric and Magnetic Fields

A "field" is an influence or force that exists throughout space, that one body exerts on another. Gravity is one such field. All matter responds to gravity, but if matter is electrically charged or contains currents, it also responds to electric and magnetic forces.

Electric currents produce magnetic fields. For instance, flows of molten metals deep inside Earth's core cause currents which sustain a huge magnetic field that extends far into space. This field helps to shield us from the solar wind plasma which buffets the entire solar system. (Diagram courtesy of the Marshall Space Flight Center/NASA)

Next to:    The Dynamic Sun