Changes
/* Resources */
* Astrophotography public database: http://www.pvol.ehu.es/pvol/
* Rocket 101 from NASA: http://exploration.grc.nasa.gov/education/rocket/TRCRocket/rocket_principles.html
* DIY water rocket http://www.esa.int/Education/Teachers_Corner/Up_up_up!_build_and_launch_your_own_rockets_TEACH_WITH_SPACE_PR23
* ...
