Wolfram Alpha usually explains its results.
Be sure to check that explanation.

the answer to life, the universe, and everything!
alpha http://wolframalpha.com/input?i=the+answer+to+life,+the+universe,+and+everything%21
google http://google.com/search?q=the+answer+to+life,+the+universe,+and+everything%21&tbs=sts:1

who wrote Eight Days A Week
alpha http://wolframalpha.com/input?i=who+wrote+Eight+Days+A+Week
google http://google.com/search?q=who+wrote+Eight+Days+A+Week
true knowledge http://www.trueknowledge.com/q/who_wrote_eight_days_a_week

what is the world population by year
alpha http://wolframalpha.com/input?i=what+is+the+world+population+by+year
google http://google.com/search?q=what+is+the+world+population+by+year

when is Rosh Hashanah 5770
alpha http://wolframalpha.com/input?i=when+is+Rosh+Hashanah+5770
google http://google.com/search?q=when+is+Rosh+Hashanah+5770

where is Vulcan
alpha http://wolframalpha.com/input?i=where+is+Vulcan
google http://google.com/search?q=where+is+Vulcan
true knowledge http://www.trueknowledge.com/q/where_is_vulcan