Linear actuator, that’s literally how the commercial units work. Most are step capable either addon or built in and some have built in close resistance tests so you don’t mush the puppy or a kid or whatever is running about your house.

If you just Amazon automatic sliding door linear you’ll get results for units you can wire into your own setup. They’re Chinese but you can use it as a base to build better or simply an example to do the same.

2 weeks you should smell it, seeing isn’t particularly necessary at that point.

Brakes, if your brakes break you break.

A dead American that made his name on a lie.

Nope. It was Clarke.

Foundation turned science to religion which is essentially using Clarke’s laws but drawn to it’s extreme.

Essentially faith + magic = miracle ≈ science + religion

Silica dioxide can occur geologically but if it’s not from quartz it’s not a rock it’s a mineral iirc.

Star Trek did have money, within the federation there were transport credits and outside the were valuable materials usually exotic ores or metals.

There was also private property which seems to take some people by surprise.

Those units pull in air from the side of the wall and exhausts it straight out. As long as they’re placed so wind helps carrying everything away they should be fine.