Another matter

Aurora Borealis; the Northern Lights.
Aurora Borealis

When is a substance not a liquid, solid, or gas? Give up? When it’s plasma, the fourth state of matter. (Not blood plasma, which is something different.)  Alas, my elementary school science failed me. And now…literally, decades later, I have become re-enchanted with this fact.

So, for those of us who are a bit out of touch with plasma, I’ll paraphrase a bit about this state. To begin with, what exactly is plasma?

Plasma is a super-heated gas that becomes so hot its electrons leave the atom’s orbit and roam free. A gas becomes a plasma when extreme heat causes its atoms to shed their electrons.

Okay, that’s cool, but where is it? We recognize the other states of matter, but what about this mysterious thing? Plasma is the most abundant form of visible matter in the universe and believed to compose up to 99 percent of what we see in the night sky; populating the infinite regions of interstellar and interplanetary space. Like the sun, stars are enormous balls of plasma. The fusion fueled by plasma creates the energy that gives us sunlight, which as we know, is essential for life on Earth.

Hmmm, so if this plasma is another state of matter, where else is it found?  Lightning, neon signs, fluorescent light bulbs, a candle flame, some television and computer displays are all examples of plasma. Like a gas, plasma has no shape or a definite volume unless it is enclosed in a container. However, distinctive from gas, when under the influence of a magnetic field, it may form structures such as filaments, beams and double layers.

Can we see it? Aurora Borealis, also known as the Northern Lights, is nature’s way of showing it to us. This occurs because plasma particles hurled from the sun interact with Earth’s magnetosphere, (the magnetic field that surrounds us).

Today’s esteemed thinker is English chemist and physicist, Sir William Crookes (1832-1919). He discovered the element thallium and invented the radiometer, the spinthariscope (a device for studying alpha particles), and the Crookes tube. Not a household name, Crookes discovered the electron when he was reconstructing the Cathode Ray. By placing black vanes on one side and silver on the other, it caused the vacuum tube to spin when it hit the light. Since the Cathode Ray had previously been built, he needed to call it something else. Today it is known as the Crookes’ Tube.

In 1879, while playing with an experimental electrical discharge tube (in which air is ionized by the introduction of a high voltage through a coil), he discovered “Plasma”.  Originally Sir William Crookes called it radiant matter. However, in 1928 Irving Langmuir, an American chemist and physicist, renamed it because he was reminded of blood plasma… go figure!