Godot

Ummm... ...my turf! (I used to be a molecular bologist) This is a nice and elegant proposal to build a novel detector with superb spatial resolution - though it's actually more like 3nm, not the single one the paper peddles. Still, better than other currently used detection systems. But... ...neither this article nor the quoted primary source https://arxiv.org/pdf/1206.6809.pdf give even the slightest hint as to how they'd manage to differentiate between WIMPs and other particles. *shrug* ["convective gravity"] None I know of, that's why I'm asking f there is any. It might even be compatible with GR, as the assumption would be that 0g (not the free fall type, but the absolute) might not be the bottom of the scale. After all, we're way deep in the gravity well ot the milky way / local group / ... Only hand-waving from me, no data or such. Just wondering whether anybody did such a theory / the math based on that assumption.

A bit of a leap, but... Might gravity work convectively? Like, in a water vortex, just with another dimension, through which the backdraft "flows"? Thus causing intergalactic gravity being slightly less than zero? Or is that disproved / excluded by existing TheoPhys? Did anybody try a model / do the numbers based on that?

I found a nice thread regarding nodal precession (that shifting of the rotational plane of the lightest object...) for a special, well studied case example we're witnessing from the inside - the Sun-Earth-Moon-three-body-system: https://www.physicsforums.com/threads/what-is-the-cause-of-lunar-nodal-and-apsidal-precession.851208/ It refers to textbook opinion on the relative influences of sun, earth's shape, and the other planets - and states that the Sun's gravitational influence is beating the others by five orders of magnitude. After all, gravity weakens by d² (d being the distance). As to your tetraedric (concise term for the equilateral triangular pyramid) model system: This depends. First and simplest case: They all start out with velocity zero. Then the whole shebang will simply collapse in the center. Which brings us back to momentum: In order to keep anything stably separate when gravity is involved, there has to be some velocity, which then leads to momentum, and from there to angular momentum. Long story short: These three+-body-systems are always chaotic systems, where you can extrapolate the future to quite some degree of precision, but without knowing the exact starting parameters for that prediction, not much can be said...

Well, in the long term, with the solar system orbiting the galactic center roughly every 250ky,... ...the direction of its pull rotates, too. So while some bodies might be tossed, due to bein dragged near e.g. Jupiter, the majority will be nudged this way now, and just the other way in 125k years. So I wouldn't expect any pattern among the surviving, just a wee attrition, which we can neither confirm nor disprove... *shrug*

From what I get, this article in the Bad Astronomy blog by Phil Plait might satisfy your needs. Seems to be the same newsitem... https://www.syfy.com/syfy-wire/bad-astronomy-hd-3167-has-2-planets-orbiting-at-right-angles-to-a-third Also: Sorry for borking the quote function... ...still learning this forum's editor. :^/

They should get created in such events as e.g. neutron star mergers - we just can't look for them. This has several reasons: First, transuranes are terribly unstable, with half-life in the millisecond range. (see below for some more...). Then, these unstable superheavy nuclei would decay into lighter nuclei, eventually ending up in one of the four possible decay series. (One of these, the Neptunium cascade, is technically extinct in earths natural element composition, as the half-life of its most stable isotope is in the million-years-range - while Earth has a few billion years of age) So, unless you're thinking REALLY big, no chance that these nuclei are stable... (...and thinking really big means atomic weights in the 10^57 range - Chandrasekar * Avogadro... ...and these "atoms" are commonly known as "neutron stars". White dwarfs still have discernible elemental compositions AFAIK.) Nuclear physics, however, predicts that at certain nucleic weigths with appropriate proton numbers, the nuclei should again be more stable. The best known is the element 110 island of stability. The wikipedia entry concerning that is quite good: https://en.wikipedia.org/wiki/Island_of_stability. As of now, we don't yet have the techniques to get those isotopes with the sufficent neutron numbers, though, but the less-stable isotopes that were generated did AFAIK mostly behave as predicted. The question where trans-irons come from - after all, nuclear fusion kinda "stops" at iron - has been partially answered / demonstrated: The merger of neutron stars mentioned above. https://www.science.org/content/article/neutron-star-mergers-may-create-much-universe-s-gold But beware, that case isn't closed yet, there's much ongoing debate: Look here for a more differentiated take: https://www.pnas.org/content/118/4/e2026110118. Still, we know that NS mergers do generate heavy elements, and there's no reason that there should be a cap at somewhere around 100 Da. That superheavy stuff just tends to decay really, really fast...

Many thanks to all the contributors for the answers! Especially the arXiv-link to that paper has been useful (though IMHO it looks like a Master thesis - even better, as there's more explanatory text, which is stuff that I do understand). What I've read so far is still south of my "comprehension threshold". Well, at least as long as I don't really delve into the included math... ...I'm just way better with a more, er ... verbal concepts. Still... ...almost all that info / thoughts have been about what happens and how when neutron stars DO collide / go into their death spiral. But what I was asking has rather been about what happens when they just don't catch each other into an orbit... We do know that they can get quite the kick during their creation, eventually leaving their planetary nebula's remnants. So my assumption was that two neutron stars with such a history - let's say a speed of a thousand km/sec - fly towards each other, with just enough offset to leave each other's gravity wells. If their periastron distance were e.g. a thousand AU, I'd guesstimate that they'd just bend their flight paths a bit, giving that hyperbolic pass I'd been pondering. But what would that safe pass distance be, order-of-magnitude-wise? 100AU? Ten? 1AU, or even a fraction of an AU??? How would that affect them? Would they shed energy from mass? Magnetic due to interaction of their magnetic fields? Angular momentum? Thermal energy? Would mass loss possibly cause one to decompress (maybe only partially)? (Like, if and when the gravity reduction on the side towards the other neutron star - L1-wards - would lower the gravity below the electron degeneracy pressure limit?) Would mass loss cause a neutron star just north of Chandrasekar to erm ... discombombulate? Would the summing up of gravities on the outward side maybe cause a collapse of a neutron star just south of Tolman-Oppenheimer-Volkoff to go snap! and become a black hole??? What about tidal forces? Shouldn't the "kneading" affect them, increasing their thermal energy? Does relativistic mass dilation play any role when they pull each other towards each other? Yeah, I know... ....questions, questions, questions - and I wonder about even more of those. And based on a quite whacky base scenario. But it's something that surely will happen every now and then, so... Also: ...isn't asking weird questions one of the driving forces of theoretical physics? Cheers + thanks again for all the input, which already is quite a bit helpful !!!

Hi @ all! I'm an interested layman with some background - mostly popular science books and TV shows, and Phil Plait's Bad Astronomy blog. Reading about the just-published gravitational wave observation results made me revisit some old thoughts about neutron stars, and what would happen if and when... (1) two of pass each other closely on hyperbolic trajectories? (1a) have a less close pass? Would there be a - kind of - critical distance they'd have to keep? (1b) could / does the acceleration on the inbound branch make one collapse further and form a black hole (due to relativistic mass dilation) (2) one neutron star does such a pass on another massive collapsed object ??? (black hole or white dwarf, either would be OK) Why do I wonder? Wellll... ...during their periastron, their gravities should cancel each other out, which might or might not bring the gravity below the "degeneracy threshold". Would that lead to a "de-degeneration" of the collapsed matter? Loss of matter? (as gravitational waves or classical photons?) What about tidal forces, spaghettification? Angular momentum? Also, assuming that one or both of the neutron stars were on the light side, just north of chandrasekar's limit, would such a mass loss cause a "de-degeneration??? And if so, a fast one (BOOOM!!!!) or a slow evaporation??? ... I could go on, but I won't. Well, not now. I'd be happy with links to any sites, lectures or even arXiv papers - as long as they contain enough text to understand them. I'm a molecular / microbiologist and did physics as a major during my school finals, worked with radioisotopes, yadda yadda - and have a reasonable grasp of stuff that goes on on the small end. But my math knowledge is pretty ... meh: At some point after the third or so integral sign, the little cogwheels unlink and it all goes "whirrrrr...." Thanks in advance and I'm hoping for some enlightening answers!