Everybody is familiar with the three states of matter: solids, liquids, and gases.
But if you heat gas, its atoms will break apart into negatively charged electrons and positively charged ions. This soup of electrons and ions is plasma—the fourth state of matter. It was discovered by William Crookes in 1879.
Plasma is seen in the glowing streamers in plasma lamps. Plasma glows because when an electron moves to a lower orbit around an ion or atom, energy is released as light. Fluorescent tubes and neon lamps rely on glowing plasma, too.
Though plasma rarely occurs naturally on Earth, in most other places plasma is everywhere. The sun and stars are made of it, and very thin plasma fills space. Plasma makes up 99 percent of matter in the visible universe. The fourth state of matter is its most common state.
- “Amazing Plasmas, Space Weather Center” (Space Science Institute)
- “Plasma: The Fourth State of Matter” (Southwest Research Institute)
- “Perspectives on Plasmas, The Fourth State of Matter” (Plasmas International)
- “Plasma: The Fourth State of Matter” (Department of Materials Science and Engineering, University of Maryland, College Park video)
- “The Fourth State of Matter” (TED video)