Children are born believers. A scientist does not ask "why?". A scientist finds out why. Unfortunately children are not built with the ability to seek any truth other than the truths given to them by their environment (parents, teachers, religious figures, or group leaders) and they are told to accept what is told to them and they simply do. Children need to develop critical thinking for themselves, much as we all likely had to at some point in our lives to bring us here.
What can we do to help our children grow up to think critically about their world? Stop answering your children’s questions about the world and start empowering them with the necessary tools.
Take your kids to the library with a list of questions they have asked and go find a book to help them use the index. When THEY locate the answer they will remember it. It was them that answered their own question.
Show your child Wikipedia and how to do searches within it.
Once they find the answer make sure you assure them they have done a very important thing. Celebrate their success in learning. Help them to formulate a response if ever asked the question. The pride they will feel when answering the question with "I went to the library and looked this up and..." versus "My mom said..." will be worth the extra time from your day to help your child become empowered.