Pluto's Outer Moons Orbit Chaotically, With Unpredictable Sunrises and Sunsets 92
StartsWithABang writes: Few things in this world are as regular as sunrise and sunset. With the application of a little physics, you can predict exactly where and when the sun will rise or set from any location on Earth. Thus far, every world in our Solar System — planet, moon and asteroid — has had the exact same experience as us. But out in the Kuiper belt, Pluto is different. The only known world in the Solar System where a significant fraction of the system's mass is not in a single component, the outer moons of the Pluto-Charon system provide a unique environment to study how planets might behave in orbit around binary stars. The amazing takeaway? The rotational part of the orbit is chaotic; the worlds tumble, and hence sunrises and sunsets are no longer predictable.
Ethan (Score:1)
Well the last link is Ethan, the first one is broken and the middle one shows a grid of potatos.
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Well the last link is Ethan, the first one is broken and the middle one shows a grid of potatos.
So they went full potato on us?
Add one to your bounce rate (Score:2, Insightful)
Click link
Medium.com
Click back
At this point you could be posting next weeks lotto numbers, I still wouldn't read it.
Re:Add one to your bounce rate (Score:4)
Yeah - and I thought that the "Turn off adverts" option would block medium.com SPAM.
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Serious question: what's with the medium.com hate? I really don't get it.
Re: Add one to your bounce rate (Score:2)
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Serious question: what's with the medium.com hate? I really don't get it.
This is not hate, by engineering standards, only mild scorn. Speaking for myself, I like good factual information backed by references if possible - Wikipedia matches that in many cases, so something like that, or perhaps articles on Science Daily:
http://www.sciencedaily.com/in... [sciencedaily.com]
The thing about medium.com is that it is targeted for a completely different audience; the people that like modern 'nature programs', with lots of movie-style cutting, funky sound-track, replayed sequences etc - probably very artis
Do they really mean "chaotic"? (Score:3)
The rotational part of the orbit is chaotic; the worlds tumble, and hence sunrises and sunsets are no longer predictable.
"Rotating around more than one axis" doesn't automatically mean chaotic, does it?
Also there was this quote from the article:
If you were on a fixed point on the surface of Nix, you’d see the Sun rise in the east on one day, then at an ever-changing angle over the next few days, and eventually it would rise in the west, cycling through in chaotic fashion.
Aren't "cycling" and "chaotic" mutually exclusive?
Even on Earth the Sun rises in an "ever-changing position" at an "ever-changing angle," but we don't call that chaotic.
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Or to put it another way, do they mean it really isn't predictable (perhaps because of all the gravitational influences in the area), or that the math is just a bit harder?
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They mean it's chaotic in that a small change in initial conditions throw your predictions completely off. It's "a bit harder" like the Mandelbrot set is "a bit more complicated than" a circle.
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I can't say anything about the math, but the video [youtube.com] does look as if there is a phase change into chaotic behavior, i.e. the satellite "tumbles out of control". Here Nix's oblong shape helps turning it into a "wobbly duck" [npr.org]. IIRC chaos means that a tiny change in initial conditions at time T can cause an arbitrarily big change at time T + delta T, thus making the result unpredictable (in spite of there being an exact formula for it) because there is always a measuring error.
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Anyway, who cares about sunset when you're that far away, the sun is just a star in the sky that's a bit brighter than the others
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"the sun is just a star in the sky that's a bit brighter than the others"
A bit very much brighter star than the others, actually:
http://blogs.discovermagazine.... [discovermagazine.com]
It is far more bright than the full moon.
Bert
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Chaos in physics and math just mean that near by starting points will diverge exponentially with evolution of the system. It requires the system to be determinant, meaning if you had perfect knowledge of the starting point, you could work out an exact prediction for the far future. But since there are errors in measurements (or other minor influences not being modeled), predictions made from your measurement will be ok for a while, but eventually diverge from the actual measurements.
So in a sense, to answ
Re:Do they really mean "chaotic"? (Score:4)
A tip that can save you a good deal of wasted effort: if the link is to medium.com, they probably havn't got all that much of a clue. Medium.com is a glossy magazine on par with "Heat", "Hello" and the like; I can't imagine anybody with technical or scientific insight wanting to waste time on it.
Bitter much? (Score:1)
Ethan's articles are quite interesting and often very informative of scientific topics at a readable level.
Why the hate? Did he used to steal your lunch money as a child, or something?
Re: Bitter much? (Score:2)
We hate them because they are full of click bait posted by someone who only wishes to monetize his site. When his audience is hard core nerds who remember the days of the internet before ads and the Eternal September.
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Why the hate?
Not hate, just irritation at somebody who likes to show off a knowledge he hasn't got. A bit like when some manager tries to impress the engineering team with the fact that he once wrote a few lines of Excel BASIC code. It makes you wince.
Re: Do they really mean "chaotic"? (Score:1)
Aren't "cycling" and "chaotic" mutually exclusive?
I last studied chaos at undergraduate level in the late 90s but, in short... no. Cyclic behaviour emerges naturally from (some) chaotic processes. I'd love to go into more detail but, like I said... late 90s, not really looked much at it since. I do remember some very nice simulations :)
Re:Do they really mean "chaotic"? (Score:5, Insightful)
Chaotic - yes. "orbit" NO! (Score:2)
Did nobody RTFA?
It's not the orbit that's chaotic. It's the rotation of the moon. It's not rotating around a fixed axis, but tumbles chaotically due to the multiple gravitational forces acting on it.
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"Rotating around more than one axis" doesn't automatically mean chaotic, does it?
There is the so called Tennis Racket Theorem [wikipedia.org], that when you have an object with no symmetry in the moment of inertia, it is unstable when trying to spin around the intermediate axis (this effect has been known about longer than the dates on wikipedia and should be in any intro mechanics book that is at the Lagrange equation level). And that doesn't require gravity, but gravity can make the process definitely chaotic in the actual physics definition: small changes to initial conditions cause diverging traje
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Aren't "cycling" and "chaotic" mutually exclusive?
No. On earth, the weather cycles from hot to cold and back to hot again on a yearly basis, yet it is still chatoic.
Chaotic doesn't mean completely unpredictable, what it means more or less is that for a tiny error in initial conditions, errors in your prediction will grow exponentially over time, but only up to a point. Once you've diverged far enough it no longer makes sense to talk in terms of errors.
The Pluto system is still constrained by physics, so the
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The Pluto system is still constrained by physics, so the objects will continue to rotate and they will continue to orbit and they are still gravitationally bound so nothing's going to go flying off to alpha centauri.
From TFA: "Rather than rotating about a single axis, Pluto’s moons Nix and Hydra tumble chaotically as they move around the Pluto-Charon system. Sure, the revolution of their orbits isn’t all that chaotic—they’re in stable, resonating orbits with one another—but the rotational part is!"
Yes, they will continue to rotate, I may have missed where someone suggested they wouldn't, but I don't think anyone did. The rotation about an axis itself being chaotic is the claim. Not the or
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in westeros the cycles of summer and winter are chaotically unpredictable.
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Hm. Predict again:
http://en.wikipedia.org/wiki/T... [wikipedia.org]
"...hurricane-force winds and rough seas in London"
http://www.bbc.com/news/uk-297... [bbc.com]
"The woman died in central London..."
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And you didn't read what I actually wrote. Tropical cyclones start in the tropics as hot core systems. They can continue to subtropical regions and even up to temperate regions. However in the links you posted, Hurricaine Vince made it as far as Spain while still a hot core system, but didn't reach London in that state. The rest were all "remenants off", i.e. after the transition to a cold core system.
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Aren't "cycling" and "chaotic" mutually exclusive?
No. Chaotic systems cycle-- look up, say "strange attractor [stsci.edu]". Or even google "cycle AND chaos theory. [google.com]"
What makes it chaotic is that the phase of the cycling is predictable in the short term, unpredictable in the long term.
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That actually brings up another possible explanation. The rotational analogue for "mass" is "inertia". But unlike mass which is a scalar, inertial is a tensor - a 3x3 matrix. Rotation is only stable around the minimum and maximum inertial axes. If you try to spin an object around a different axis, its r
Incredible (Score:3)
Not a single science fiction writer, or scientific study that I know, imagined worlds with chaotic orbits. But here is one, in our own solar system. And we found out just now.
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I'm not convinced that medium.com's definition of "chaotic" - meaning "a bit weirder than on Earth" - is in any way related to the mathematical concept of chaos.
Re:Incredible (Score:5, Funny)
medium.com's definition of chaotic is getting the wrong coffee from the barista.
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Funny, yes, but the scientists behind the research, at NASA, do use the term correctly. They do mean chaotic in the mathematical sense. I listened to the streamed press conference on the subject and, if you look beyond the egregious mis-pronouciation of Charon by the lead author on the work, someone who really should know better, they did a pretty good job of establishing a likely chaotic orientation for Hydra and Nix. Not "really messy and hard to predict but deterministic," but chaotic. With an N-body
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once you know that conditions you could just plug some variables into a calculator and find out when the sun is going to rise next.
This is a prerequisite for all chaotic systems, they are determinate, and if you had exact initial conditions, you could just plug them into a calculator and get an answer. Chaotic does not mean indeterminate or even necessarily unpredictable, only that it is very sensitive to your initial conditions and no amount of real world measurement will give you the accuracy needed to make exact long term predictions (often there are still some properties you can predict over the long term still though).
In other wo
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Because a "chaotic" or "unpredictable" orbit is a practical impossibility
To the contrary, it is likely that all orbits in systems with more than two bodies are chaotic. That includes our solar system.
Fortunately for us, the time scale for unpredictability for the solar system is many billions of years.
and is not what we found.
Well, that part was correct. What was found was that the rotations were chaotic. The orbits seem to be regular.
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Despite what Ethan claims, we've known about chaos in the solar system for a long time. Since people started doing simulations, actually. Hyperion is known to rotate chaotically, and IIRC the orbit of the moon is also mildly chaotic.
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Not a single science fiction writer, or scientific study that I know, imagined worlds with chaotic orbits
Cixin Liu, "The Three-body Problem."
There are several old-ish scifi stories but I don't recall their titles at this instant.
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Every piece of science fiction that touched the subject (and I've read) understood that the orbit of asteroid belt (as a group of objects) is a chaotic system.
Yes one did (Score:2)
Non planet with moons (Score:3)
Definition Moon: any planetary satellite:
the moons of Jupiter.
Ah, the anonymous jerk. hello there. (Score:1)
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Definition of moon is any natural celestial body orbiting another that is not a star. Asteroids have had known moons before the whole planet definition mess, and the definition of moon has never been restricted to going around a planet, under old or new definition.
Well aside from the fact that would define Pluto and Charon as each others moon. or none of these as moons, your knowledge seems to argue against
Merriam Webster,
the moon : the large round object that circles the Earth and that shines at night by reflecting light from the sun
: a large round object like the moon that circles around a planet other than the Earth
22 charming words for nasty people
Full Definition of MOON
1
a often capitalized : the earth's natural satellite that shines by the sun's reflected light, revolves about the earth from west to east in about 2912 days with reference to the sun or about 2713 days with reference to the stars, and has a diameter of 2160 miles (3475 kilometers), a mean distance from the earth of about 238,900 miles (384,400 kilometers), and a mass about one eightieth that of the earth —usually used with the
b : one complete moon cycle consisting of four phases
c : satellite 2; specifically : a natural satellite of a planet
and universe today
A moon is defined to be a celestial body that makes an orbit around a planet, including the eight major planets, dwarf planets, and minor planets. A moon may also be referred to as a natural satellite, although to differentiate it from other astronomical bodies orbiting another body, e.g. a planet orbiting a star, the term moon is used exclusively to make a reference to a planet’s natural satellite.
Now I hardly hold the bad usage against you, This is merely part of the problem of the badly done rush to redefine what is a planet.
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News flash: single line C dictionary definition doesn't contain full scientific details of corner cases! More at 11.
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So what you're saying is, "that's no moon!"
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Dwarf moons?
Eh. (Score:3)
Can we get a tag for this? (Score:2)
Can we please get a medium.com tag so I can filter out this garbage.
I don't want to read any "science" blog from an "author" who doesn't even know what chaotic means.
Chaotic rotation (Score:2)
Can we please get a medium.com tag so I can filter out this garbage. I don't want to read any "science" blog from an "author" who doesn't even know what chaotic means.
The use of the word "chaotic" is accurate here.
The inaccurate word used in the summary (not the article) was "orbit". It is the rotation that is chaotic, not the orbit.
Nevertheless, the science is pretty interesting. Sorry you don't want to hear about it.
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The use of the word "chaotic" is accurate here.
Disagree you can't cycle through anything in a chaotic fashion. It either cycles and therefore is non-chaotic, or it's chaotic and therefore does not cycle. It's like saying that Neptune's orbit around the sun is chaotic because it doesn't follow a perfect path due to gravitational effects of Jupiter. It can still be accurately modelled and thus isn't chaotic.
Three body problem (Score:2)
Looks like a three body problem: http://www.amazon.com/Three-Bo... [amazon.com]
A Classic Problem (Score:2)
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Although one day the problem may be cracked as things stand the motion of multiple objects being attracted and repelled by each other appears to be chaotic.
There is no "appears to be chaotic" in mathematics and physics, as chaos is a well definite mathematical phenomena. Regardless of how much advances are made in analysis of a particular system or chaotic systems in general, it doesn't change that a system fits that definition.
Winter is coming (Score:1)
At last, science has proven that there is a none-magical explanation of Westeros's unpredictable seasons.
Not the only chaotically rotating moon (Score:3, Interesting)
I doubt they are chaotic (Score:2)
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http://www.dynamics.unam.edu/B... [unam.edu]
Evolution of attractors in quasiperiodically forced systems, From quasiperiodic to strange nonchaotic to chaotic.
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You're getting into semantics there. You could probably build a supercomputer cluster to dedicate to simulating the motion and predict the positions. That you have to makes it worth putting a handle on to talk about that kind of system - 'chaotic' is commonly used; that doesn't mean the motions are impossible to ever know due to quantum uncertainty.
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