Wikipedia is fine as long as you remember that it is written by people who may have a strong political/personal bias, and who also might Not be able to separate fact from bias/fiction.  Or present a complete picture.  What many take for hard science is only highly theoretical, with no actual proof (other than conjecture stretching a wide chasm).  Some of it has been around for long enough that it's considered fact, when that is not the case.  You know, tell a lie often enough... So if you are researching rocks, physics, elements, etc, the information is fairly sound. Things like global warming, some historical events, certain political figures, don't expect an impartial write up.