All children ask “why?” Gifted children are more likely, though, to ask about things that have complex or multi-faceted answers.
It is a valuable lesson for parents to not be the single authoritative source of answers. Instead, ask for clarification about their question. For which detail are they really searching?
What resource can they use to find the answer? Go beyond Alexa or Siri. Is there a book, a website, or an experience that can teach them the “why?”
If kids want to know something procedural, like “why do I need to pick up my toys?” or “why do I have to go to bed?” Parents responses are often, “I said so!” After hundreds of “why” questions, mom is often too tired to explain one more reason.
Sometimes the best answer is a responding question. “That is a good question! Why do you think you should pick up your toys?” Let the child reason out the advantage to being able to walk without stepping on anything, keeping up with all the pieces to a puzzle or LEGO set, or being able to find it next time they want to play with it. When they express a good reason and you acknowledge it, (“Great idea! Let’s do it together!”) then the child is more likely to do it than if they feel like the only reason is that YOU want them to do it.
There are many good books to answer the scientific reasons for natural events. I recommend you read them together to discover the answers. The years of “why?” go by so fast. Take advantage of every day you get to spend with your inquisitive child. The interaction between you and your child develops their language skills. The “why?” questions are working on their prefrontal cortex, too. Keep building that brain! 
Gifted Child Mom 