New periodic orbits of the three-body problem
phys.org
phys.org
That said, using this method to discover new periodic solutions of the three-body system is a very neat application, which deserves applause!
Actually, I made the first comment after I checked the second author's earlier paper https://arxiv.org/abs/1109.0130 where they essentially made the claim about inventing "CNS" as the first-ever reliable technique for long-term solutions of dynamical systems, without referencing any of the earlier work I mentioned above.
However, I just checked the actual text of this new article on the three-body problem (through sci-hub) and there the authors do cite the earlier work I mentioned above, giving proper attribution to others for the basic ideas behind what they call "CNS"! So all is actually well, and the peer review presumably did work (or the authors found out about the earlier work even before writing the new paper). It is just the press release that is misleading, as usual.
To answer your question, I'm not really familiar with the research on the N-body problem, so I can't say why or whether no one tried looking for periodic solutions in this way before. Perhaps no one actually thought of it, or they didn't try since they didn't expect to find anything, or they didn't have the computational resources, or they just couldn't figure out the details of how to do it (which the present authors did, and deserve credit for). Again, I was not trying to downplay the significance of this work, and finding new applications of existing methods (and making even tiny improvements along the way) is how science progresses. It also happens all the time that methods get rediscovered/reinvented independently.
From the CSN paper:
"the residual and round-off errors are verified and estimated carefully by means of different time-step Δt, different precision of data, and different order M of Taylor expansion....for the considered problem, the truncation and round-off errors of the CNS can be reduced even to the level of 10^−1244 and 10^−1000, respectively, so that the micro-level inherent physical uncertainty of the initial condition (in the level of 10^−60) of the H\'{e}non-Heiles system can be investigated accurately."
From a personal recommendation elsewhere:
Pros:
- the premise is good
- many of the plot twists are good or brilliant
- many problems described are obvious in hindsight, but something you would never think about
Cons:
- Writing is uneven. Some parts you sail through, some parts make you physically cringe
- Many (too many) parts are "here's a scientific theory I learned about, let me give you a brief Wikipedia-style description. (Contrast with Blindsight where explanation of theories used is done in the appendix to the book, and is an interesting read on its own)
- No person in the history of this world has ever spoken like characters in the book. Dialogs are just people explaining things to each other
- Some things are introduced "just because". Otherwise the crises in the book couldn't be solved (e.g. it's assumed that the book talks about now and suddenly there are advanced nanomaterials and working hibernation)
All in all:
It's a very solid "hard" science fiction book which could be absolutely brilliant. But it's greatness is greatly reduced by the language and structure.
So? Doesn't sound that different from 90% of classic sci-fi, especially Asimov.
>- No person in the history of this world has ever spoken like characters in the book. Dialogs are just people explaining things to each other
Ditto.
That doesn’t make it good writing.
Sci-fi was never about the writing, in the way hi-brow literature was.
Heck, it started from pulp magazines aimed at teenagers.
I'd heard the sequel was not so good—anyone have an opinion?
Liu escalates the arms race between races in the last third of the book so far that i was genuinely shocked and mildly unnerved at the implications of it. The trilogy really should have been called "The Dark Forest" because that is precisely what is described therein.
You can't transmit information faster than light using quantum entanglement.
https://en.wikipedia.org/wiki/Faster-than-light#Quantum_mech...
Like, I'd be more happy with wormholes or tachyons or "actually the universe is a simulation" as possible fictional sources of superluminal communication than entanglement, just because we really do know how entanglement behaves quite well by now and it's no good for FTL communication.
Maybe gravity doesn't exist on the sun. Maybe electrons attract in the Sahara desert. This is what you're suggesting.
Authors are making a common mistake, and you're justifying it. The point of science fiction (at least hard scifi[0][1]) is to predict the future given some assumptions or premise like "we can control individual neurons"[2] or "there's life on a neutron star"[3] or "the moon exploded"[4] or "message from outer space"[5]. You get some outlandish sounding ideas that readers can consider seriously because the author genuinely thought them through. Ideas that don't respect relativity are useless. It's like writing fiction about Napoleon with walkie-talkies. It doesn't make sense, you could (probably) do much better than Napoleonic tactics with a walkie-talkie. A military tactic in space that relies on instant communication is a useless idea. Plus I just plain think it would've made a better story if they had to strategize around the speed of light.
(spoiler) to be fair, The Three Body Problem almost did it right, their ships travel at non-relativistic speeds, and the first 3 messages take 5 years to transmit. But I didn't bother reading past the first book after the quantum entanglement mistake on the last few pages.
Maybe I'm getting elitist. The hard/soft scifi thing is an old conversation. I understand that the social commentary is a big aspect of some books, just don't call them science fiction.
[0] https://news.ycombinator.com/item?id=15462327
[1] https://www.google.ca/search?q=three+body+problem+"hard+scie...
[2] https://en.wikipedia.org/wiki/The_Nexus_Trilogy
[3] https://en.wikipedia.org/wiki/Dragon%27s_Egg
[4] https://en.wikipedia.org/wiki/Seveneves
[5] https://en.wikipedia.org/wiki/His_Master%27s_Voice_(novel)
https://books.google.ca/books/about/Space_and_Time_in_Specia...
https://news.ycombinator.com/item?id=8937197
not exactly. SR is true only in the fixed Euclidean metric space. It is applicable to our Universe only as far as our Universe can be approximated by such a metric space. Which is really a very good approximation - almost like a "fact" - at relatively small (yet not extremely small) scales and at small mass/energy densities.
>There's no debate, it's a certainty that you cannot transmit information faster than light.
in the domain of applicability of SR. Ie. until, say, you do something severe to that metric space. Which author actually did, in some way, by folding/unfolding additional dimensions.
>Plus I just plain think it would've made a better story if they had to strategize around the speed of light.
reminded how USSR armed forces seriously strategized around cavalry attacks on the Eve of WWII, ie. the war which opened for USSR by lightning speed attack by German tanks and airforce.
The math behind GR and QM contradict each other. We have a large amount of empirical evidence for a speed limit for information travel, yes, but since we don't even know how the universe works (ie a mathematically consistent model, with few parameters, supported by experimental evidence), I don't think you can say "it's how the universe works". We might eventually find out that the information speed limit only holds at low energy scales for example.
Really??
https://arxiv.org/abs/1306.5777
It seems like in the late 80s and early 90s this topic was very hot, then became a fad. You can find many books and papers that all have basically the same content (Lorenz/Henon attractors, logistic map, Mandelbrot set). I think it underwent a name change to "complexity science" during the 90s and 00s. I'm not in academia, but I do try to follow the topic because it is truly fascinating and IMO more accessible than quantum or relativity physics because many of the systems involved can be easily programmed/visualized with basic computers.
Funny thing is, it can not be opened, because of the 19th national congress. All .edu.cn second-level domain were shutdown for "security reasons"
I have seen people talk about the puzzles in terms of planets, gravity, massless bodies etc. when in-fact they are just circles that move towards or away from other circles. Theoretically people who can identifiy the Euler intergrator should be able to go "aha! I know what to do now" but so many get hung up on the idea that it is wrong.
This integrator is used in my three body app, to remove the issues due to close encounters. An old blog post of mine has the details: http://nbodyphysics.com/blog/2015/12/08/threebody-2-0/
The scholarpedia article is a good meta-reference:http://www.scholarpedia.org/article/Three_body_problem
The very simplest version is called the Euler problem. Two fixed masses and a third moving in the "dipole field". All the solutions can be explicitly determined (although only in terms of e.g. Jacobi elliptic functions and other elliptics). There's a book "Integrable Systems in Celestial Mechanics" by Mathuna.
I recently added the Euler problem to my iOS app ThreeBody: https://appadvice.com/app/threebody-lite/951920756
Some day I'll get around to adding these 600 solutions...
But still you would have to unpack that dipole approximation to figure out if this perturbation will slowly change it in ways that do something significant in the long run.