I had this exact conversation a few days ago, and my kid is even 6!

On the bright side, that's plenty of time to do something about it

So strangely true... My son got scared a few years ago while watching a documentary about black holes and the death of the Universe.

Don't worry about the sun expanding to swallow earth! It will gradually get hotter as the core uses fuel and contracts, rendering earth uninhabitable within just 1b years (if we don't beat it to the punch)

This fact, paired with the fact that first it will become a red giant and completely destroy our little ball of dirt, is a serious problem when you're trying to come up with any sort of universal value for our lives. Eventually, every single thing human beings have ever done but we bathed in atomic fire for a billion years.

The only solution I could ultimately find was to stop thinking about the universe, just because something that matters to me as a human can't be explained by looking at alpha centurai doesn't mean it doesn't matter to me.