We are aware of the three states of matter -- solid, liquid, and gas -- from our daily lives.  After all, if you are alive you eat, drink, and breathe.  Matter has a fourth state that is totally different, though: plasma.  Ironically, this state of matter that we barely recognize makes up about 99% of the normal matter in the universe (excluding dark matter).  Just what is this mysterious state of matter, and why would we care about something so foreign to our experience?  There are many good reasons to learn about plasma, one of which brings back a childhood memory....

My cousins and I were playing in the front yard of their old ranch house on Rock Creek.  The skies were growing darker and we could see massive clouds gathering around the Bighorn Mountains to the west.  We didn't want to go in, even when the wind began to pick up.  We were having too much fun, and besides it was a warm summer day.  Suddenly there was a loud bang! and a flash of light.  I don't remember falling, but found myself on the ground, my ears ringing.  We were never quite sure where the lightning struck, but it was very close.  We were just thankful for the trees and the house, and even the utility pole for acting as lightning rods.

Maybe you have your own stories about the power of lightning.  When you see it flashing in the (hopefully) distant skies, you are witnessing that fourth state of matter.  The intense electrical energy created by friction of the atmosphere has ripped the electrons loose from the air atoms, making them conductive.  As the electrical energy courses through the path opening ahead of it through the atmosphere, magnetic fields form from the moving current of electrons.  The magnetic fields squeeze the charged atoms together into a filament, which becomes super hot from the high voltage and current.  The atoms vibrate faster and faster, becoming so hot they become incandescent, and a lightning bolt results.

There are many other examples of plasma in space and on Earth.  Some of these forms have important applications in technology.  Many appear as beautiful glowing clouds in photographs of deep space.  This week we will heighten our awareness of plasma, offering gems of knowledge for our peers in the discussion forum.

We will also open our awareness to another fact, this one hidden in plain sight: the fact that many stars vary in brightness.  Instead of a sky sprinkled with eternal, unchanging sparks of light, many are constantly changing, pulsating, flaring up or dying down.  We can measure how much a star varies in brightness by comparing it to neighboring stars that remain constant.  If we keep track of when we observed it, and continue to make observations at later dates, we can track those changes in a graph of magnitude versus time, creating what astronomers call a light curve.  This brings the fourth dimension into our observations: that of time.


Human beings have been exploring and conquering new territory since their migration from Africa, some 30,000 years ago. Our species has covered the planet, and now with our technologies we are poised to explore space. How far will we be able to go? Is the Galaxy our next frontier?


Contrary to science fiction and the movies, traveling to other stars poses incredible challenges to homo sapiens. We were, after all, evolved to survive on the Earth, not outer space. Indeed, it may be that no species, anywhere, can cross the vastness of interstellar space. Without any evidence one way or another, the best we can do is use physics and mathematics to evaluate our chances.


The key to this question lies in how matter, energy, and space-time are related. Whereas light can cross the void for billions of years and show us objects we can never touch, matter has no such celestial superhighway. Getting matter to cross such immense distances will be harder than getting Granny to leave home.


  • Explore relationships between matter and energy.

  • Identify challenges and solutions to interstellar spaceflight.

  • Discuss the feasibility of exploring interstellar space.

  • Design a spacecraft that would support an interstellar space exploration mission.

  • View a total lunar eclipse on the morning of April 4th.