Expert: Ed - 10/15/2010

Question
Hello Ed,
Just as there are 4 main Earth systems (hydrosphere, atmosphere, litosphere, and biosphere), which would be the best way to classify the universe into 4 categories?  
I thought, for instance, the 4 forces of the universe (gravity, electromagnetism, strong, and weak nuclear forces) or 4 main elements (planets, stars, galaxies, and quasars).  Do you know of a better way to classify it into 4 categories?
Lupita  

Answer
Lupita, it sounds like you are off to a good start.  I like your idea of how to divide the universe into four parts.  Or, you could also divide it up into atoms, neutrinos, cold dark matter, and dark energy.  Look at the page for the WMAP, and see what you think.

http://map.gsfc.nasa.gov/universe/uni_matter.html

I hope this helps.  Keep Looking Up!
-Ed