If you had a small black hole in a lab you could generate power from the hawking radiation, likely enough to power the entire world. A 1,000,000 ton black hole would last over a thousand years without feeding it more mass and produce about 300 TW of energy (increasing over time, so you better keep feeding it). You'd also need some pretty good sunglasses to be able to watch things being thrown into it. Also I'm not sure how you could throw anything into it given the amount of radiation pressure... Maybe a dedicated particle accelerator could do it.

Anything smaller while also lasting long enough to do an experiment on and you'd likely end up producing too much energy and destroying the planet.

> which experiments exactly?

Put a bunch of charge into it to generate a naked singularity. Then look at it.

More usefully: perfect the Penrose process.

There's a few obvious things. What you've got is an almost "vertical" gravity well near the object. A smaller black hole would actually have a steeper gravity well than a large one.

(1) See how gravity behaves at those strengths and scales by firing lasers and particle beams past it, grazing the event horizon, and use that information to test quantum gravity hypotheses and things like string theory. Classical gravity predicts certain results. Quantum and non-classical theories would make different predictions. For example, you might see direct evidence of gravitational quantization very close to the horizon.

(2) Chuck stuff into it: heavy ions, small masses with a coilgun. Measure the results: spectrum, particles emitted, etc.

(3) Chuck stuff into it in a very precise way and use its extreme near-horizon gravitational well as a particle accelerator to achieve collision energies potentially millions of times greater than the LHC. You would not be able to directly observe these collisions, but you could potentially observe stuff kicked out. Orbit it with an array of sensors and magnetic traps.

Bonus: use its gravity well to yeet small probes at interstellar velocities (a few percent 'c' or higher) for flyby missions to photograph exoplanets? I believe you could use the Oberth effect here and do something like fly very close and fire a single Orion-style nuclear pulse at a sacrificial pusher plate. The impulse would accelerate the payload to insane velocities.

No human passengers though, since the acceleration would probably do this: https://www.youtube.com/watch?v=waG8YYTwpAQ

I'm not sure anything after the event horizon right? Since no light == no information.