Kids have a tendency to ask many, many questions, most of which seem to come out of nowhere and are completely unrelated to anything going on at that moment! One of the joys of parenthood! Many times, and I would argue most of the time, your kids probably ask questions that you don't have a clear answer to. I know my kids do. Instead of faking through an answer to shut your kid up, or saying something based on something you thought you once heard, don't be afraid to tell your child "I don't know."
I think that too often parents and caregivers are afraid to tell a child they don't know the answer for fear of appearing dumb or uniformed. I'm telling you to stop worrying about that. Your kids are still going to see you as the center of their universe even if you admit that you don't know the answer to something. There are advantages to admitting that you don't know. It shows your kids that you are not perfect and that nobody is. It also provides an opportunity to search out an answer WITH your child.
If your child asks you an obscure question about a dinosaur, for example, tell them you don't know (assuming you really don't), and then head to the computer or library to search for the answer with him/her. This will help show your child the power of researching answers to questions and is a great bonding experience between you and your child.
So the next time your child asks you a question you don't know the answer to, don't hesitate. Just say "I don't know" and then find the answer together!