As in, a companion to the planet.

Moons are satellites.

Satellite: from Latin satellitem (nominative satelles) “an attendant” upon a distinguished person; “a body-guard, a courtier; an assistant”

Yes.

I would refer back to my peanut butter comment. Or bee stings. Or celery.

Some people are near-sighted. Some have asthma. ADHD. Some have 12 toes. Or two penises.

People are genetically diverse. They just are.

I will answer in good faith. People respond to different stimulus differently. It is as simple as that.

Some people die from eating small traces of peanuts, some have no problem eating a whole tub of peanut butter in one sitting.

Some people are okay losing an hour or two of sleep. Some will have their bodies react horribly to it.