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Comment by TheRealPomax | Hacker News Reader

"clever joke" aside: why? Primordial black holes are a rather completely different category from super-massive black holes, with masses theorized as small as a single plank mass. Not a lot of sucking happens when PBH are involved.

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Fig1 in the paper shows the exact size of the PBH: > FIG. 1. Exact scale (1:1) illustration of a 5M⊕ PBH. Note that a 10M⊕ PBH is roughly the size of a ten pin bowling ball.

Indeed; if the mass really were tiny, we'd have no idea that there was any object to look for.

Wouldn't a Planck mass black hole have evaporated immediately?

Things are weird when dealing with Planck quantities, so "almost certainly", but only almost. The main point was that PBH are generally small and look nothing like what people think of if they've only heard of black holes from popular science and sci-fi.

I suppose given the enormous force gradients around even a basketball sized black hole, it could potentially be turned into one of the most efficient ways to convert matter into energy by building an accretion disk around it?

If you get the timing right, you could just shoot those at the enemy near the speed of light, and they would explosively decay right as they arrived. If the mass was low enough, they'd be effectively invisible, wouldn't they? Screw antimatter bombs, these would be pretty horrific. Instead of kilograms' worth of matter-to-energy conversion, you could have hundreds of tons worth. Wonder what that would be in megatonnage?

Other than the whole "you wouldn't be able to move it around" because unless you have a portable gravity projector, that thing isn't going anywhere: it is a gravity sink. Your enemies would have be lured into range, at which point, longbows will do a much, much better job =D

Yes, the amount of gravitational potential energy release is much higher for the same mass than you get from fusion. I’ve seen estimates of 10% - 40% of the mass-energy of the in-falling matter.

You “just” need a way to get the matter there and a way to capture that energy.

Yes it would have. Planck mass black holes aren't even mentioned in this paper, I'm confused as to where this came from. PBH = 'primordial black hole' meaning formed at the beginning of the universe, not Planck Mass Black Hole, which, you're right, would have evaporated instantly.

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