I am writing this short story. It is part of the overall book that I am writing, but it is also a story that can be enjoyed completely on its own. In that story, a planet-sized ship approaches our Solar System, and, ultimately maybe, Earth. For dimensions, let's say it is equal to 1.5 of Earth's diameter. According to Google, that's 25,512 19,134 kilometers. The Planet-Ship is probably less dense than Earth, as it is largely occupied by biomass and weird alien electronics. You may think of it as a round Borg cube, from Star Trek.

My "Round Borg Cube" is completely black and spherical, with a smooth surface without any visible features.

What I wanna know is...

• Assuming that the object is on a very slow path towards Earth, at what proximity will its effects be known?
• At which point will scientists observe its effects, view it, or detect it with instruments?
• If that is at all possible, what would be a threshold in which the "Round Borgs" would have to interrupt their movement in order to remain undetected?
• At which distance will it be visible to the naked eye (if at all)?
• And if they chose to get dangerously close to Earth, what would be the impact on our environment?

I understand that is a lot to ask, but I just can't trust GPT for that kind of stuff, even if their answers sound plausible. Perhaps someone with astronomical knowledge as well as an interest in science fiction will find my questions enticing. I don't expect precise answers because I am not providing precise information. So feel free to speculate on that scenario. In any case, I am grateful for any answer I can get.

Thanks!

My 5-year-old loves doing “science experiments” at home with me and her older siblings, but it seems that the online lists of experiments we’re choosing from are truncated to leave off all but the least dangerous activities. This makes sense for a lot of low-parental-involvement contexts, but I’m going to be directing and deeply involved in these experiments. And I want fire. Smoke. Sparks. I want to make these experiments feel adventurous so the kids get really excited about whatever we’re learning. Baking soda and vinegar volcanoes and elephant toothpaste just don’t cut it.

What experiments can you recommend using only relatively common household materials? Chemicals, candles, electricity, a stovetop, etc. (Assume that the experimenters will all be taking standard precautions, wearing PPE, and generally using the experiments as both an opportunity to learn about science and about the safety measures that go with science experimentation.)

Or if you know of any websites listing these more spectacular home science experiments, please share those as well.

Bonus if the experiments involve multiple possible outcomes that the kid can use pen and paper and elementary math to predict in advance.