I truly love the concept behind this book: Big kids questions answered simply by truly great minds. A sample question would be: If you’re on a boat, with no food or water, what do you do? The answer is by Roz Savage, first woman to row three oceans. Or, Why is space so sparkly? Answered by Martin Rees, an astronomer.
Get it here: Big Questions from Little People: and Simple Answers from Great Minds