links: 

 

    2^2-1

  2^3-1

  2^5-1

  2^7-1

 2^13-1

 2^17-1

2^13-1 2^19-1

 2^31-1

jiggling atoms

sombrero galaxy

justice & morality

snow & ice crystals

13th century poetry

a mockingbird song

education & creativity

problems women face