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I've always thought the idea of planet nine being a primordial black hole was kinda cool, but AFAIK we have no evidence to suggest this. Unless I'm mistaken if
by api 3y ago
I've always thought the idea of planet nine being a primordial black hole was kinda cool, but AFAIK we have no evidence to suggest this.
Unless I'm mistaken if PBHs do exist then one with 2-4 Earth masses is within the plausible range. It'd be about the size of a billiard ball. The existence of lots and lots of PBHs of various sizes is one dark matter candidate.
https://en.wikipedia.org/wiki/Primordial_black_hole https://en.wikipedia.org/wiki/Primordial_black_hole
If there were such a thing out there we could send a probe to it. I can't imagine what kinds of interesting physics we could do if we could directly examine a black hole.
It'd be neat if it were actually useful in the far future too, like as a power source to generate and beam energy to interstellar spacecraft. There's even concepts like this:
https://en.wikipedia.org/wiki/Black_hole_starship https://en.wikipedia.org/wiki/Black_hole_starship
A PBH of that mass would not be useful for this but perhaps there'd be a way to leverage the extreme conditions created near the event horizon to generate smaller ones that evaporate quickly... like the extreme physics analog of sourdough starter.
- marcosdumay 3y agoThe idea of a black hole starship is that you carry the black hole around, just like any other engine. If you want to beam power from it, there isn't anything at all there to gain compared to beaming power from the Sun. And if you want to carry it with your ship, it weighting 2 Earth masses is kind of a drawback.
- djbusby 3y agoYou don't move the blackhole+ship, that's crazy. You'd simply move the universe around your ship.
- moritzwarhier 3y agoWhich is already possible by shoveling dark matter into an oven, right? I always wondered why there's no episode where the implications of more than two dark matter engines working at once were explored :)
- coffeebeqn 3y agoHow would you move a black hole around?
- calamari4065 3y agoJust get out and push
- marcosdumay 3y agoAFAIK, the most popular answer is to give it an electrical charge. I really don't know how are you supposed to maintain that change long-term. But then, it's similar to the problem of deciding whether the emissions from the black hole are particles that you can focus around, so I guess it's an open problem.
- mcswell 3y agoThere was a scifi story decades ago about using small but heavy objects (neutronium, IIRC) as an integral part of space ships. The idea was not to use them to generate energy, but to generate a gravitational field to counteract the effects on humans of high acceleration. The object was held in front of the spacecraft, and would be moved closer when high acceleration was needed. I guess if the ship was just drifting, you'd have the heavy object at a sufficient distance to cause ~1g gravity. I don't remember the story's title or author(s), but it likely appeared in Analog.
- at_a_remove 3y agoIt's Charles Sheffield, in particular his McAndrew series.
- mcswell 3y agoThank you! With that help, I was able to find the story: "Moment of Inertial." And here's a link to the story: https://www.baen.com/Chapters/067157857X/067157857X__2.htm https://www.baen.com/Chapters/067157857X/067157857X__2.htm
- at_a_remove 3y agoIf I recall, he used that invention in several stories. They're quite enjoyable. Sheffield, as a writer with a hard science background, came up with some very interesting ideas, such as The Sturm Invocation, and the entire Proteus series was very well-considered. Sometimes I get a taste for the diamond-hard sf and he scratches that itch. Hal Clement, too, if you're into that; Half Life is probably the best novel where the concept of the scientific method itself is at the forefront.
- mcswell 3y agoI now have Half Life on order, your fault. I was intrigued by another Hal Clement title, Trio for Slide Rule and Typewriter. I have a slide rule sitting a few feet from me as I write this, in case of emergency. No typewriter, though.
- kunrii8528 3y agoThere are far more feasible alternatives to deep space propulsion that could actually work now, and all you have to do is detonate a couple of nukes. https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... See also its cousin: https://www.centauri-dreams.org/2012/07/20/medusa-nuclear-pulse-propulsion-and-the-sail/ https://www.centauri-dreams.org/2012/07/20/medusa-nuclear-pu... You can even try these in KSP with mods afaik
- sparrowInHand 3y ago? Are you serious. We have concepts for light driven probes now. They even can slow down, by ejecting a parabolic lightsail, that bounces light from the opposit direction back to them. Its all lightweight and - way more feasable, if you abandon the " a human has to go there idea". Communication would be an issue, but otherwise...
- api 3y agoYeah I'm familiar with the old "Devil's pogo stick." Apparently thermonuclear Orion could achieve as high as 10% the speed of light, which would get you to the Centauri system within a single human life span (barely).
- deleted 3y ago[deleted]
- codethief 3y ago> If there were such a thing out there we could send a probe to it. You might be interested in Ed Witten's paper about this topic: "Searching for a Black Hole in the Outer Solar System", https://arxiv.org/abs/2004.14192 https://arxiv.org/abs/2004.14192 (See also this related comment from the HN discussion back then which puts Witten's paper into context very nicely: https://news.ycombinator.com/item?id=23135031 https://news.ycombinator.com/item?id=23135031 )
- tejtm 3y agoA PBH that size would be extremely useful for getting out of (and back into) our solar system, at least for probes that could survive being slingshot to a fraction of light speed. It could be like slingshoting around the sun, but but at a few miles from the core instead of a million miles.
- Zee2 3y agoIn that scenario, I'd love to see the kinds of cool relativistic time dilation experiments we could run on those probes.
- jfengel 3y agoIt's hard to imagine a scenario in which the solar system captures a wandering black hole. If it comes in it's going to keep going, or take the hyperbola back out the way it came. It's not impossible and such scenarios can be constructed. But they're really narrow and it's hard to justify putting a lot of effort into looking for wild coincidences.
- thegrim33 3y agoMaybe you could elaborate? As the solar system already contains bodies with masses both smaller and larger than the primordial black holes mentioned, what would be the issue?
- roywiggins 3y agoall of the stuff I'm the Solar system that we know about probably was here from the beginning, forming out of the same cloud of dust that produced the sun. A black hole would have to wander in from elsewhere and somehow get captured rather than zipping by on a hyperbolic orbit.
- scheme271 3y agoThe relative velocity of stuff that wasn't in the cloud that formed the solar system would almost certainly be really high. So it would take a lot to capture the an extra-solar body. Any bodies from outside the solar system would probably either travel straight through the solar system or do something like what ʻOumuamua did.
- jvanderbot 3y agoIf you draw a box around the solar system, and want a fast moving BH to settle in without rejecting on hyperbolic orbit, you'd just have to throw out another object that's comparable in size, at comparable speed. Momentum conserved. A near miss with one of Jupiters moons might sling the BH into an orbit at slower pace and throw that moon into, say, earth to create our own moon. This stuff probably happens more often than we think, on a galactic time scale.