My kid asks those exact questions, right down to the recurring concern over infinite space. I feel your pain.

Videos are weirdly challenging, because so many of the glossy ones are done in a very dramatic way where it's not just "Here's how hurricanes work", but instead "DEADLY SUPER STORM! WILL YOU SURVIVE?" - totally upsetting for sensitive kids like mine.

I've had not-great luck with full-length science videos, with the odd exception - if you have Netflix or Amazon Prime, some of the older science videos are pretty slow/calm and acceptable. My kid has been willing to watch chunks of Sagan's THE COSMOS as long as I sit with him and pause it to discuss when he needs to.

I find a lot of the stuff that is actually for kids (Magic Schoolbus and so on) too loud and busy and non-literal ("But school buses can't shrink down and fly into your blood.") and generally kind of a bust.

But I have one possible option for you: there's a BBC kid show called Nina and the Neurons that is actually about science, and is calm and literal. The different series are about engineering, biology, science, and so on. The episodes are 15 minutes long and hosted by a female scientist character (which I value, YMMV). Downside is there's no legal way to get it in the US that I know of, so you're stuck watching it on Youtube. Here's the episode about stars:


(That user has a lot of Nina and the Neurons episodes.)

Another option is a show my kid has gone through phases of being very into: Beakman's World (on Netflix streaming). It's a pretty dorky show from the 90s, and is very loud and fast-cutting and has a lot of sound effects (all things I dislike) but is also pretty serious about the science, and does not do the thing where it uses magic or things that can't actually happen. Significant downside is that each episode features an experiment, which my child naturally demands to do.

I've also periodically watched old Bill Nye or Mr. Wizard clips with him on youtube if he needs information on a specific topic.

Another Youtube option is this channel: https://www.youtube.com/user/1veritasium

It's not for kids, but it's well-done and pretty accessible.