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Comment by ericmay | Hacker News Reader

> "You need data, there is no data, and there won’t be any data."

Why won't there be any data? Is it just physically impossible to collect or is it an engineering problem?

All of the black holes we know for sure exist (those produced by supernovae) are predicted to dissolve so slowly that it would take thousands of years or perhaps even millions of years of observation to produce any data on Hawking radiation.

If small black holes can actually form (which is currently just a theory) there may be some chance to observe and measure them dissolving. However, I believe this requires energies far higher than any particle collider we can expect to build in the next hundred years, so this avenue is also closed.

So, perhaps "never" is a bit pessimistic, but not far off in human terms.

>All of the black holes we know for sure exist (those produced by supernovae) are predicted to dissolve so slowly that it would take thousands of years or perhaps even millions of years of observation to produce any data on Hawking radiation.

Isn't there also an issue that the background temperature of space is still too high compared to the temperature of Hawking Radiation and thus blackholes are still growing, even in 'empty space', because the temperature is greater than what they would lose from Hawking radiation? And this temperature difference will continue for the foreseeable future, even on galactic time scales.

Because data comes from experiments.

Unless we figure out how to create a black hole in the lab (spoiler, you wouldn't want to) or could get close to a natural black hole (spoiler, you wouldn't want to) you're not going to get any data for this.

>create a black hole in the lab (spoiler, you wouldn't want to)

Current understanding is that there is nothing dangerous about creating black hole in the lab: it’s going to be so small that it will evaporate quickly, and event horizon is so small that it will be very unlikely to capture new matter.

> Current understanding

I.e., if a tiny black hole had formed at LLC and swallowed the Earth, that would have been data.

Recall all the arguments quoting rates of Hawking Radiation from small black holes as if it were proven fact.

>if a tiny black hole had formed at LLC and swallowed the Earth

The point is that tiny black hole, man-made or from the outer space, can't swallow Earth in any reasonable amount of time: when it's gravitationally captured and orbits through Earth internals "forever", it's event horizon is so small, that it's very rarely interacts and captures new matter (after all, matter is not "dense" on the atomic level), so it grows very very slowly, even if it doesn't evaporate at all.

Any light black hole has really minuscule size. For comparison: black hole of mass of Earth is couple centimeters in diameter. Now, if such black hole comes from outer space and hits Earth, almost nothing will be left.

You're right, unless there is unknown physics that happens near a black hole.

It's still important to note that black holes at the atomic level, and gravitational effects of any kind at that level in fact, are entirely speculative science. QM doesn't allow for any kind of gravitational attraction, and GR doesn't account for any of the effects observed at atomic level, so we are left with only speculation.

Microscopic black holes are an entire extra level of speculation over any other gravitational effects. Even in GR, black holes are not exactly consistent with the theory - they are singularities, indicating that (even if we knew nothing of QM) GR can't be a complete theory of nature.

So, discussing what microscopic black holes can or can't do is not much more than discussing what effect photon torpedoes would have on a Holtzman shield (Star Trek x Dune fanfic).

I was thinking of a black hole that would be large enough to do any sort of science with. I personally wouldn't be concerned with it consuming the world, I would be more concerned with it evaporating!

Because the smaller the blackhole is the faster it evaporates, below a certain energy the blackhole would turn all the energy/mass that was put into it into energy close to instantly, i.e. it basically turns into a bomb.

> Is it just physically impossible to collect or is it an engineering problem?

Engineering as in you’d need to create and measure a shielded black hole. (Shielded because you need to isolate it from the CMB.)

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