HN Gopher Feed (2017-10-12) - page 1 of 10 ___________________________________________________________________
New periodic orbits of the three-body problem
86 points by msuvakov
https://phys.org/news/2017-10-scientists-periodic-orbits-famous-...___________________________________________________________________
phkahler - 2 hours ago
Are any of them dynamically stable?
Pxtl - 1 hours ago
Yeah, that's what I'm curious about. Would all of them deviate
if they were breathed on wrong? Could any of them occur in
nature?
davesque - 3 hours ago
From a complete layman's point of view, I wonder if it's
appropriate to think of a three-body system as somehow irreducible.
In other words, maybe a "closed-form" representation of three-body
motion can be defined in terms of a finite combination of stable
periodic configurations. Anyway, just some musings.
sova - 3 hours ago
Irreducible is a good way to describe the equally-balanced
constraint in a 3-body situation.
powertower - 2 hours ago
Is there an upper limit on how many different periodic orbitals a
3-body system may have?
ChuckMcM - 38 minutes ago
Generally if you could prove that there was, or that their
wasn't, you would probably win the Fields Medal at least.
forkandwait - 1 hours ago
> Today, chaotic dynamics are widely regarded as the third great
scientific revolution in physics in 20th century, comparable to
relativity and quantum mechanics.Really??
twic - 43 minutes ago
I wonder if that tells you something about the author's age.
Chaos theory was the next big thing in the '80s and '90s - recall
that Jeff Goldblum played a chaos theorist in Jurassic Park in
1993! It seems much less exciting today. I think it gave way to
string theory, and now we have AI (yet again).
alanbernstein - 1 hours ago
I've never heard such a thing, but if you think of "chaotic
dynamics" as responsible for the dramatic improvement in weather
prediction, it might start to make sense.
[deleted]
sizzzzlerz - 2 hours ago
So if the problem was first proposed by Newton in the 17th century,
how did early investigators simulate the interactions between the
bodies up until the electronic computer became available. There are
no closed form solutions A.F.A.I.K. so they must have calculated
the body's state by hand, I guess. How tedious.
rwmj - 1 hours ago
My probably naive intuition says that if you had a system with
two "suns" in the centre rotating around each other very closely,
and one distant planet rotating about the centre of mass of the
two suns, that would be stable surely?
musgravepeter - 1 hours ago
Yes, that does work. In the literature this is called a
"heirarchical system"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/951920756Some day I'll get around to adding
these 600 solutions...
adrianratnapala - 40 minutes ago
Right, but this dipole solution will neglect the perturbation
of the third body on whatever is creating the dipole. Fair
enough, because we expect the effect to be tiny.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.
musgravepeter - 2 hours ago
With some symmetry you can find a couple of solutions, which is
what Laplace and Lagrange did. e.g. http://www.phys.lsu.edu/facul
ty/gonzalez/Teaching/Phys7221/T...The scholarpedia article is a
good meta-
reference:http://www.scholarpedia.org/article/Three_body_problem
[deleted]
fdej - 2 hours ago
The "CNS" is as far as I can tell just the use of a high order
Taylor series together with multiple precision arithmetic for
solving ODEs. This is a well known method for long term simulation
of dynamical systems that has been around for decades. The authors
basically imply that they invented this method and were the first
to be able to study long term evolution of dynamical systems
reliably because of it. Fair enough if they just weren't aware of
previous work (which happens all the time), but it's an oversight
that shouldn't have passed peer review.That said, using this method
to discover new periodic solutions of the three-body system is a
very neat application, which deserves applause!
spuz - 1 hours ago
Are you sure that their numerical method isn't new? The abstract
says that the author created it in 2009 and this paper further
develops it to apply to the three body problem. If it already
existed, can you say why it had not already been applied to the
three body problem?
trhway - 3 hours ago
as we know it is too late, trisolaris fleet is already under way,
and the problem with the human science progress is so apparent that
it even became a subject of the recent Big Bang Theory episode.
lnanek2 - 20 minutes ago
fortunately, we live in a dark forest, and need only threaten to
shine a light to make the invasion fleet pointless...
hellcow - 2 hours ago
For those downvoting, the above comment is a reference to a
terrific sci-fi novel, "The Three-Body Problem," which focuses on
the same problem discussed in the article.
musgravepeter - 3 hours ago
The pre-print from arxiv: https://arxiv.org/abs/1705.00527v4
ccleve - 2 hours ago
I'm halfway through The Three Body Problem, a science fiction novel
by Chinese author Cixin Liu. The apparent irrationality of three-
body orbits is central to the story. So far, it's excellent, both
as science fiction and as social commentary on contemporary China.
shpx - 48 minutes ago
(minor spoiler) in my opinion, any book that violates the theory
of relativity is not science fiction, it's a fantasy novel set in
"space".You can't transmit information faster than light using
quantum entanglement.https://en.wikipedia.org/wiki/Faster-than-
light#Quantum_mech...
ericjang - 41 minutes ago
Maybe the laws of our math and physics are not invariant to
space and time :)
zem - 2 hours ago
amazing series! book 2 is probably the most mindblowing sf novel
i've read since brin's "startide rising"
sova - 2 hours ago
Have you read Nexus yet?
ChuckMcM - 42 minutes ago
That would be more literally mind blowing :-) but I can
heartily recommend it.
westoncb - 25 minutes ago
I'd second this recommendation: Nexus is one of the most
interesting and entertaining sci-fi novels I've read in
recent years.I'd heard the sequel was not so good?anyone have
an opinion?
sp332 - 3 hours ago
The site hosting the videos is down. Are there only 6 families (as
in the caption at the top) or 600? Are all of the orbits discussed
in the article in 2D or are some of them 3D? At the end it says the
new CNS technique found only 243 new families, so how were the
hundreds of other new ones found?
sova - 3 hours ago
CNS from the article, " clean numerical simulation" enabled them
to find 243 more than what the computational power was capable of
finding with a lossy representation of periodicity. In other
words, the strength of the machine using old-style algorithms for
detection would have gotten 357+ solutions, and their use of CNS
which cleans up the math a lot for the supercomputer helped them
find an additional 243 that would have slipped through the
cracks.