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 I know if you fire lasers at plasma, the electrons get excited, but what is plasma?

Jimmy B.

 Jimmy,

A plasma is a gas of particles which are electrically charged.  A plasma will have electrons - small, negatvely charged particles-- as well as ions. An ion is a neutral atom which has lost one or more of its' electrons.  If you take a regular gas such as air (made of neutral atoms of Oxygen, Nitrogen, Carbon Dioxide, etc.) and make it really, really hot (like a million degrees), the atoms hit each other and knock off electrons and the gas becomes a plasma.

Of course, there is another plasma --the fluid component of blood -- and this confuses things. They are completely unrelated.

Paulett

 Hi Jimmy,

 You may have talked about 3 states of matter in school: solid, liquid, and gas.  The type of plasma that is a gas of electrons and ions (not the blood plasma!) can be considered a 4th state of matter.  The reason is that even though plasmas are like gases in many ways, plasmas also have unique and special properties.   Plasmas exhibit collective behavior - the electrons and ions in the plasma are close enough together that their electric fields can influence the particles around them, rather than just the particles immediately next to them. Another special property of a plasma is that it is quasi-neutral.  This means that if you look very closely at a plasma, you would see that it is made of electrically charged particles like electrons and ions.  However, if you looked at the plasma from far enough away, the positive and negative charges would average out and it would appear electrically neutral (no charge!).  Another special property of a plasma is that it is electrically conductive, so that it can be affected by electric and magnetic fields. 

 Although some of the Solar Week scientists study the Sun, while others study the Earth's magnetosphere and ionosphere, we all study plasmas in one way or another.  There are also scientists who do laboratory experiments with plasmas inside vacuum chambers.  My boss is mainly a space physicist, but he is also collaborates with scientists at UCLA who do experiments with the Large Plasma Device (LAPD). You can see a picture of the LAPD here.

Kris

Also a majority, more than 99 percent,  of the visible matter in the universe is in the plasma state! This might be difficult to believe since at the surface of the Earth we usually do not encounter the matter in the plasma state. But the universe is filled with plasma. For example, the Sun and the other stars are huge balls of plasma, the solar wind that permeates the heliosphere is in the plasma state, planetary nebulae and so on.