Taking it to the bottom of layman's terms, what would be the shortlist of significant things in the universe?
A list I could think of myself would put
- Energy (at whatever wavelength travelling through space)
- Gas (Atoms and molecules floating interplanetary, interstellar and intergalactic space)
- Rocks (Anything from dust to planets)
- Stars (In more general terms, anything that is or were a star... would include also black holes, magnetars and novae)
Things that does not fit very well in this classifications however are:
- The super massive black hole of galaxies (although I could simply put it in galaxies)
- Dark matter (but I do not worry too much until it has been properly measured :) )
- Wormholes (if they even exist..)
- Anything else
What else is to be put in either list?