Pluto's Outer Moons Orbit Chaotically, With Unpredictable Sunrises and Sunsets

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.

Comments

Ethan

[Whiteox]

Well the last link is Ethan, the first one is broken and the middle one shows a grid of potatos.

Re:Ethan

[Ol Olsoc]

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

[Anonymous Coward]

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

[jandersen]

Yeah - and I thought that the "Turn off adverts" option would block medium.com SPAM.

Re:Add one to your bounce rate

[Lord Crc]

Serious question: what's with the medium.com hate? I really don't get it.

Re: Add one to your bounce rate

[O('_')O_Bush]

It might have more to do with citing a blog in a science article.

Re:Add one to your bounce rate

[jandersen]

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...

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 artistic, but tedious and drawn out ad infinitum and with very little factual information. Or, perhaps a bit like BBC's Horizon series, which also tends to be tediously sparse on real information (and I am a great fan of BBC in general, it has to be said).

Do they really mean "chaotic"?

[wonkey_monkey]

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.

Re:Do they really mean "chaotic"?

[wonkey_monkey]

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?

Re:Do they really mean "chaotic"?

[jandersen]

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.

Re: Do they really mean "chaotic"?

[Anonymous Coward]

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"?

[srussia]

Yes. It's an n-body dynamical system.

Re:Do they really mean "chaotic"?

[Anonymous Coward]

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.

Re:Do they really mean "chaotic"?

[Anonymous Coward]

I can't say anything about the math, but the video 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". 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.

Re:Do they really mean "chaotic"?

[michelcolman]

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

Re:Do they really mean "chaotic"?

[Anonymous Coward]

"Rotating around more than one axis" doesn't automatically mean chaotic, does it?

There is the so called Tennis Racket Theorem, 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 trajectories.

Even on Earth the Sun rises in an "ever-changing position" at an "ever-changing angle," but we don't call that chaotic.

In a simplified system, nutation is a regular oscillation and no chaotic. In the real world, there are a lot of things that affect the rotation of the Earth including things we can't predict now (shift of parts of the crust). In principle it is all mechanics so it would still be chaotic in the sense that small changes have diverging trajectories, but we don't have enough information to come even close to making a detailed prediction beyond the regular oscillations.

Re:Do they really mean "chaotic"?

[Anonymous Coward]

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 answer your question, it is both and neither. The system is determinant, predictable in the short term, but not long term. The math is not necessary hard, as some very simple mathematical systems can express chaotic behavior, although some of the analysis techniques developed for chaotic systems are not exactly simple math either.

Re:Do they really mean "chaotic"?

[serviscope_minor]

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 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.

Again, much like the weather: it's chaotic but still has many predictable elements. For instance I can predict that a hurricane (or if you prefer, tropical cyclone) will never hit London. Hurricanes are hot core systems and those simply don't progress past 40 degrees or so, because the ambient temperatures become too low. Any huge storm hitting London will be a cold core system.

Re:Do they really mean "chaotic"?

[Geoffrey.landis]

Aren't "cycling" and "chaotic" mutually exclusive?

No. Chaotic systems cycle-- look up, say "strange attractor". Or even google "cycle AND chaos theory."

What makes it chaotic is that the phase of the cycling is predictable in the short term, unpredictable in the long term.

Re:Do they really mean "chaotic"?

[Maritz]

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 orbit.

Re:Do they really mean "chaotic"?

[Noah Haders]

in westeros the cycles of summer and winter are chaotically unpredictable.

Re:Do they really mean "chaotic"?

[kanweg]

"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....

It is far more bright than the full moon.

Bert

Re:Do they really mean "chaotic"?

[rahultyagi]

I had never bothered to make this calculation, but always sort of assumed that the Sun would look like a disc from those distances... very small but still with a disc shape easily discernible by naked eye. This made me do the calculation. Turns out that the Sun looks almost exactly the same size from Pluto (at perihelion) as Venus does from Earth (at their closest distance)! However, venus at its closest is bright enough to cast discernible shadows and Sun's absolute brightness is a LOTTTT more than venus. So, yes, you are right. just another star in the sky that is however *much* brighter than anything else. For religions starting on pluto, you can easily bet against anything other than the Sun or Charon being their chief deity.

Re:Do they really mean "chaotic"?

[Solandri]

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?

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 rotational axis will oscillate between the minimum and maximum axes, like a ball oscillating back and forth in a bowl between the minimum and maximum potential energy. In other words, it will tumble in a seemingly chaotic pattern, until you realize this oscillation is going on.

When designing spacecraft, extra care is taken to distribute mass so as to make sure the inertia tensor is symmetric along the axes where your thrusters will impart rotation. That way firing a thruster causes a predictable rotation, rather than tumbling.

Re:Do they really mean "chaotic"?

[towermac]

Hm. Predict again:

http://en.wikipedia.org/wiki/T...

"...hurricane-force winds and rough seas in London"

http://www.bbc.com/news/uk-297...

"The woman died in central London..."

Re:Do they really mean "chaotic"?

[serviscope_minor]

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.

Incredible

[cachimaster]

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.

Re:Incredible

[wonkey_monkey]

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

[Lumpy]

medium.com's definition of chaotic is getting the wrong coffee from the barista.

Re:Incredible

[andremerzky400]

I doubt it ... :P

Re:Incredible

[Anonymous Coward]

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 words, chaos is quite real world and practical, while what you describe in your post, "once you know that conditions" is practically impossible in chaotic systems (at least for long term predictions, short term ones still work).

Re:Incredible

[Maritz]

Article doesn't say that the orbits are chaotic. It says that they are stable, and even have resonances.

Re:Incredible

[Geoffrey.landis]

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.

Re:Incredible

[ceoyoyo]

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.

Re:Incredible

[cellocgw]

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.

Re:Incredible

[pz]

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 system, it turns out it isn't that hard to establish chaos.

And, of course, we know from simulation work done at MIT that the orbit of Pluto is likely chaotic, as published in Science some years ago: http://groups.csail.mit.edu/ma... -- I've worked with some of the people who wrote that report, and they are among the best, and most careful scientists I know.

Re:Incredible

[Unknown74]

Check out Fred Saberhagen's "Berkerker's Star". Miracanda is a very strange place consisting of a neutron star, a black hole, and Miracanda - which is sort of, but not, a planet. ("This is not a planet. This is not a planet.") They all three exist in a very loopy sort of mutual orbit.

Re:Incredible

[HornWumpus]

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.

Non planet with moons

[Crashmarik]

Definition Moon: any planetary satellite:
the moons of Jupiter.

Re:Non planet with moons

[Crashmarik]

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.

Re:Non planet with moons

[hackertourist]

So what you're saying is, "that's no moon!"

Re:Non planet with moons

[Gavagai80]

News flash: single line C dictionary definition doesn't contain full scientific details of corner cases! More at 11.

Eh.

[fuzzyfuzzyfungus]

Asteroids do not concern me, Slashdot.

Can we get a tag for this?

[thegarbz]

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.

Three body problem

[heikkile]

Looks like a three body problem: http://www.amazon.com/Three-Bo...

Re:That's no moons

[michelcolman]

Dwarf moons?

A Classic Problem

[JimSadler]

Mathematics has always suffered a severe challenge when there are more than two actors in a system. 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.

Re:A Classic Problem

[Anonymous Coward]

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.

Chaotic - yes. "orbit" NO!

[lindseyp]

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.

Winter is coming

[Anonymous Coward]

At last, science has proven that there is a none-magical explanation of Westeros's unpredictable seasons.

Not the only chaotically rotating moon

[mr.gson]

Saturn's moon Hyperion is also known to tumble chaotically.

I doubt they are chaotic

[140Mandak262Jamuna]

Are they chaotic? The friction in inter galactic space is nearly zero. These bodies will obey the conservation of mass, linear momentum, angular momentum and energy. They are way below reltativistic speeds to be involved with Hawkins radiation and such stuff. They should be fully predictable and non chaotic, right? The period might be very long and complex compared to our sunsets and sunrises, but are they chaotic?

Re:I doubt they are chaotic

[PlusFiveTroll]

http://www.dynamics.unam.edu/B...

Evolution of attractors in quasiperiodically forced systems, From quasiperiodic to strange nonchaotic to chaotic.

Re:I doubt they are chaotic

[bill_mcgonigle]

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.

Chaotic rotation

[Geoffrey.landis]

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.

Re:Chaotic rotation

[thegarbz]

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.

Re: Bitter much?

[IMightB]

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.

Re:Bitter much?

[jandersen]

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:And so...

[Unknown74]

I like this guy! Go Pluto!

Ah, the anonymous jerk. hello there.

[Unknown74]

Ah, the anonymous jerk. hello there.

Yes one did

[Mike Van Pelt]

G. David Nordley, "A Calendar of Chaos", Analog, December 1991