edit: ok maybe we'd need it to be between us and the sun for that to work, the lensing would be that of other stars I guess. I suppose the important question is, since it's relatively close to us, would it deform space hard enough for the gravitational lensing to be noticeable at such close proximity.
edit2: more train of thought, just because it's fun, I suppose since it's so small and the gravity relatively weak (i.e. not as strong as some huge stars or galaxies) any halo or distortion would not extend more than a couple meter, which wouldn't be noticeable from our distance, right?
F = G * (m1 * m2) / r^2 . G = 6.674 / 10^11 (m^3 / (kg * s^2)) | m1 = 5 * 5.972 * 10^24 kg | m2 = 100 kg
Only r in the equation above is not a constant, so we can compute F(r) - F(r+1) to get a difference in force that being 1 meter closer to the black hole would make at a distance r. Basically, this is the difference between how hard your toes would be pulled down vs your heard if you curl into a ball.
Distance Force Force + 1 Diff in kg
1 1.99286E+17 4.98214E+16 1.49464E+16
1000 1.99286E+11 1.98888E+11 39797421.92
10000 1992856400 1992457888 39851.15023
20000 498214100 498164282.3 4981.767364
30000 221428488.9 221413727.7 1476.11612
40000 124553525 124547297.6 622.744272
50000 79714256 79711067.53 318.8474585
60000 55357122.22 55355277.03 184.5191277
70000 40670538.78 40669376.79 116.1990494
This answer: https://physics.stackexchange.com/a/332510/236187 seems to suggest that it takes mere milliseconds once one is within three times the Schwarzschild radius of the black hole. And that dozens of radii outward, one already moves at a significant fraction of the speed of light.
Paul Brunton: "The most valuable metaphysical fruit of the quantum theory is its finding that the processes of the universe which occur in space and time, emanate from what is fundamentally not in space and time."
Nisargadatta Maharaj: "In reality, time and space exist in you. You do not exist in them."
It's a great kids' book.
The real question is, with the warping of space-time, how long would it take for us to perceive the end? Would it seem like the black hole started moving incredibly slowly, or would our planet start getting torn apart before then?
From (distant) memory it was a fun read with some science but not overly realistic wrt to how humanity would react.
> On its own, a PBH of mass 5M⊕ has a Hawking temperature of 0.004 K, making it colder than the CMB, and since it’s radius is rBH ∼ 5 cm, the power radiated by the PBH alone is minuscule.
Also wolfram alpha says it would take 7e52 years to evaporate from hawking radiation, so it's quite stable: https://www.wolframalpha.com/input/?i=%285120*pi*G%5E2*%285+...
I assume but am not sure that the cooling of an already-sufficiently-cold black hole in this manner is slower than the cooling of the CMB itself due to expansion, so that at some point as the universe winds down it will begin to shrink again and eventually evaporate, but definitely over the lifetime of any star we see a black hole this side won't radiate significantly, or evaporate.
Note that physicists don't believe this 0-size point is actually correct - the expectation is that a theory of quantum gravity would predict some fixed size for the black hole, one that also prevents the infinities inherent in the GR description of black holes.
I understand that line printers (those that printed a line at a time rather than a character at a time) also supported overstrike sequences, but I never punched through the paper on one. Likewise, presumably the same approach would work with a daisy-wheel or typeball printer, but I can't testify.
The theory is that in the early universe, WIMPs were created spontaneously due to massive temperatures of the primordial plasma, but later as the universe expanded and cooled, this creation didn't work. However, the WIMPs would still be able to react with each other, reducing their numbers, until they'd be so rare that annihilations are such a rare event that they don't significantly reduce their numbers any more. Then space expanded even further.
Apparently due to the strong perturbances of the dark matter that this black hole creates, it creates potentially detectable annihilations, and they discuss which scenarios can be excluded or detected with data generated by the FERMI-LAT gamma ray telescope.
Not a physicist though, so please correct me if I'm wrong.
Although they're theorized to have a mass closer to the Higgs boson than a proton, which is a lot of mass as far as subatomic particles go.
That is some delicious astrophysics smorgasborg
Previous discussion: https://news.ycombinator.com/item?id=21078068
> Planet Nine is a hypothetical planet in the outer region of the Solar System. Its gravitational effects could explain the unlikely clustering of orbits for a group of extreme trans-Neptunian objects (ETNOs), bodies beyond Neptune that orbit the Sun
"What if the reason the only evidence of planet 9 we have is gravity is that gravity is the most observable aspect of planet 9" would be expert-level trolling if it weren't actual science. :)
How to tell something is written by an American :)
Why? Because in the US ten pin bowling is the only kind of bowling most people are aware of, except perhaps in New England where candlepin bowling is popular or central Texas where nine pin is played. I'd thus expect an American author to simply say "bowling ball".
The UK is mostly ten pin, but in the non-English speaking parts of Europe nine pin is big. I'd expect a UK author to be aware of that and so specify the type of bowling ball.
Less to do with the dangerous action and more with the 80+ average player age, but still.
Lawn bowls is very common. Thus a bowling ball may be taken as some to mean one of these. Which is very different in size to a ten pin bowling ball.
However, it's semantics. I agree with the logic.
The hard part of using a black hole for propulsion is that you’ll need to drag a planetary mass along. It’s an interesting engineering problem.
I'm not sure if any of that would apply to a ~planet mass black hole spinning with ~planet sized angular momentum, or how solid the physics even is, but it sounds cool anyway.
Fun concept - a bomb you can't throw without it dragging your world along.
Wouldn’t that require locating a mirror behind the PBH and bouncing signals back off of it?
Roman? Did you maybe mean Romulan?
One more reason for rehabilitation as prison policy.
I believe, that throwing pebbles into black hole, and watching the ripples they form would be very amusing.
Extreme rip-your-craft-to-bits tidal effects  would make life exciting. Also, see 'Neutron Star' by Larry Niven for a description of such a manoeuvre, albeit a less dangerous one than than sling-shoting a black Hole because of the larger size of the neutron star.
Imagine getting a 1970's style planetary alignment, going with a Voyager style slingshot and your final assist is a couple thousand miles away from a black hole.
Sending a spacecraft out hundreds of AU is doable with current technology, but it would take many decades.
As for the size, the paper has a 1:1 scale drawing of it.
If the box were a perfect sphere then yes it would have zero net gravitational pull on the black hole, but the black hole would still have an extremely strong pull on it. And that's still assuming it's perfectly centered which would be almost impossible to maintain.
No, it would not. Newton's third law: if an object has zero net pull on the black hole, the black hole also has to have a zero net pull on the object. The shell theorem is more general than you are assuming: it doesn’t matter if the heavier object is inside or outside, the surrounding object doesn't need to be spherical (it can be any shape as long as it fully envelopes the black hole) and the black hole doesn't need to be centered. I know it is a counter-intuitive result, but it can be easily proven with calculus.
See for instance this sentence about Dyson shells: "Such a shell would have no net gravitational interaction with its englobed star (see shell theorem)" https://en.wikipedia.org/wiki/Dyson_sphere#Dyson_shell
Edit: Related, what is bigger? The gravitational force the Moon exerts on Earth or the gravitational force the Earth exerts on the Moon? Veritasium has a nice video explaining the answer: https://www.youtube.com/watch?v=8bTdMmNZm2M
Reading the exact passage you quoted, "the compressive strength of the material forming the sphere would have to be immense to prevent implosion due to the star's gravity."
Cage's material will still get attracted to the black hole and close to the event horizon structural forces exerted by gravity will be hard / impossible to counteract with current materials: https://en.wikipedia.org/wiki/Strength_of_materials
Such a box can definitely be built if you make it much larger than a dishwasher.
I'm not sure how a black hole would help create life, an inbound Planet 9 would certainly be a hinderince to life's existence though.
IIRC, that small would evaporate almost instantly. I think you’re thinking of particle radius, which would be mountain mass.
 this formula says less than a plank time and is therefore wrong: https://www.wolframalpha.com/input/?i=5120π%28G%29%5E2%28mas...
And again, the predicted lifespan of a proton-mass black hole is significantly less than a plank time, which in turn is therefore a sign that — one way another — the maths doesn’t actually apply to that situation in the first place.
Not all black holes have to be big; a 10 earth mass black hole would be quite tiny.
Supermassive black holes are on a whole different level however.
> A black hole of 387 million solar masses would have the average density of water and would be comparable to a giant water balloon extending from the sun almost to Jupiter.
I still like to think if it existed it could be our ticket out of the solar system.
(or a braking system for reentering if we ever made it that far)
I'd give it a 3/5 - fun read, not a classic.
That would explain why it is not more popular. If you install your software in a black hole, you cannot get any computed data from it out again.