You know more than your child does. Parenting would be extremely difficult if you didn't! As far as your child is concerned, you're the wisest soul in the whole universe, and the person who can answer all of their questions. They'll take anything you tell them as gospel truth, and they may even form opinions based upon your answers.
Telling them something, though, is no substitute for them learning it themselves. There's no harm in telling your child basic answers to basic questions, but they should also be encouraged to inform themselves via research and form their own perspectives based upon that. More importantly, you should never give your child an answer to a question if you're not sure of it. They may accept it as fact and spend half their life believing it! Encourage them to read and learn, and to tell you what they've found out.