I am created Shiva, destroyer of worlds

By Phil Plait | March 1, 2010 11:00 am

This is totally cool: an animated simulator that lets you make model solar systems! It’s put together by the PhET Interactive Simulations group at — hey! — the University of Colorado at Boulder.

All you have to do is put in the masses, locations, and initial velocities of the objects (up to four) and then hit "go". What you’ll probably find is that for almost any parameters you use, you won’t get a stable system. You’ll fling off the tiny moon, or drop a planet into the star, or collide two planets (when you do, one survives after a brief comical flash). There are preset conditions that will put together a stable simulation, so I suggest you start there and then tweak the numbers. The most fun thing is to fiddle with the mass and see what happens.

mysolarsystem

You’ll note a slider that says Accurate vs. Fast. That has to do with bin size. Basically, a simulation like this calculates the force of gravity of each object on every other object using Newton’s law. But it needs a time interval to do this: where will all the objects be after some period of time? You can pick that time step, but the smaller the time step the more accurate it will be. That’s because gravity works continuously. If you take the Earth’s current position and velocity and ask where it will be a year from now by just adding a year to the program, it’ll extrapolate the Earth’s current velocity direction! The program will take that velocity (about 30 km/sec) and multiply it by one year, and get a distance of about a billion kilometers. It’ll then place the Earth there. But that’s not right, because the Earth orbits the Sun; the Sun’s gravity is continuously changing the direction of Earth’s motion. So the smaller the time step, the more accurate the program will be.

At least, I think that’s what’s going on here. I’ve fiddled with programs like this before, and that’s what I’ve found. Roundoff error can be bad too; because the program can’t do the calculations exactly — the decimal value has to cut off somewhere — every step has a little bit of error in it. That adds up, and after a few orbits things can go wonky. This one does a pretty good job of that, it looks like.

Anyway, go play god with your very own cosmic erector set. It’s fun, and before you know it a long time will have passed… but you might get a feel for orbital mechanics. It’s worth it.

CATEGORIZED UNDER: Astronomy, Cool stuff, Geekery, Science

Comments (89)

  1. Death from the Skies. Shiva, Destroyer of Worlds…you are an awfully down person aren’t you? ;)

  2. I really like stuff like this because I personally think it is so much more educational than anything else.

    Sure we can make a ton of blog posts explaining something, but something like this allows you to in some sense have “hands on” experience which is worth its weight in gold.

  3. DennyMo

    Wow! The solar system simulator is fun, but it’s only the tip of the iceberg. Lots of fun simulations to play with, for all kinds of physical science principles. I take a science roadshow into the local elementary schools each spring, some of these demos might come in handy. Thanks for the link.

  4. I saw this a few days ago when Ian O’Neil tweeted about it. Or was it Mike Brown? I forget!
    Soooo cool! Soooo much fun!

  5. @DennyMo

    Do you know of any web sites that act as a sort of clearing house for such simulations? It would be great to be able to access all the varied simulators from one place.

  6. Cheyenne

    The “slingshot” ones are particularly cool. Nice illustration of how Jupiter can give a significant gravity assist to a passing satellite.

  7. Hey try this one… from the sun/earth/moon preset, increase the sun and earth’s masses by 50%.

  8. kozmund

    Their stable binary star and planet simulation is interesting as far as the fast vs. accurate thing goes. The default “fairly fast” has the planet hitting one star after 90 time units. The most accurate setting has it hitting the other star entirely.

    Looking at the slingshot simulation, when it’s fast, you can see the line segments when one of the objects has a very sharp curve. Since it appears much, much smoother (shorter line segments) in the accurate mode, I think the time interval is exactly what they were doing.

    Here I was hoping they were doing some sort of customized bignum stuff to get scalable approximation error…

  9. James H.

    Phil, after going over Keplers laws and Newtons law of universal gravitation with my physics classes we went down to the computer lab a couple of weeks ago to play around with this simulation. I gave the students the actual masses and distances from the Sun to use as references and told them to construct their own stable three planet solar system that would look like Mercury, Venus and Earth. They did a pretty good job but got some pretty wild ellipses. Some of my REALLY bright students brought out the calculators and started setting up ratios to get numbers as close as they could to actual values. I had one looking up orbital periods so he could try and figure out orbital speeds as well. Its a pretty fun little program, and the systems they already have made for you are fun to watch. That phet site has a lot of good simulations to use as labs.

  10. Beads

    Oh great THANKS! I was having a productive day, now that’s gone down the pan! ;) Now if I tweak the mass of that one, what happens………….? OH!

  11. Gamercow

    Wow, its come a long way from the playset I found in 2000. http://www.colorado.edu/physics/2000/applets/satellites.html

  12. James

    That’s great, but a couple of questions…

    What would be some reasonable settings to match our own solar system?

    Does anyone know if there is an open source version of this or something similar?

    It might be a good project to help me get to grips with xcode :0)

  13. I never understand why people write programs that try to brute-force integrate all of the gravitational forces in cartesian coordinates. It’s the easiest way to code it, but also the least useful. Numerical errors tend to amplify, planets spiral down to the sun or out into deep space, energy is not explicitly conserved, etc. Bate, Mueller, and White’s book, _Fundamentals of Astrodynamics_, describes in great detail how to calculate multi-body orbital interactions with a dominating primary. I often have to take the step size *down* artificially, because the adaptive integrator starts using multi-year stepsizes, which is boring to display.

    In broad terms, the methods detailed therein treat the influence of the other objects as perturbations on the basic ellipse that everything is trying to run around the centre of mass. Instead of computing the net force of all objects, the techniques take these perturbative forces and compute how they adjust the basic orbital parameters. Rather than computing X,Y,Z as a function of time, you compute semi-major axis, eccentricity, angle of periapsis, and phase angle as a function of time, giving you a greatly improved accuracy even with very large integration step sizes.

  14. KurtMac

    If you like the solar system modeler that I recommend you try Phun: http://www.phunland.com which is a free “2D physics sandbox” program. In their recent release they’ve included the ability to add “attraction” to objects which is a fine substitute for gravitational force. By giving objects differing levels of attraction you can slingshot them around each other and put them into orbit.

    Phun is not quite as scientific as the above solar system modeler, but I’ve spent many hours creating entire systems, complete with comets, asteroid belts and moons, then sit back and watch the chaos and collisions ensue! With many objects in an orbit it is interesting to watch as the “planets” tend to always settle themselves down from all the initial collisions and end up in rather stable, separate orbits. That is, until you can no longer resist tossing a big ol’ Jupiter careening through on a collision course! Kabloosh!

  15. SlyEcho

    I made a program similar to this, but it was more of a prototype kind of thing with a preset stable system with multiple bodies (the trick is to have net zero kinetic energy) and ability to add more bodies with key presses. Still it was fun playing around with it, adding more bodies to it to destabilize the system and observing three-body systems etc. Sometimes even the stable system degenerated because of rounding/discrete-time issues.

    For a lot of cool physics simulators there is also http://www.falstad.com/mathphysics.html

  16. MoonShark

    Try this one… Sun, planet, comet set to max accuracy, let it run to t~100. The same thing at 50% accuracy, wait till t~175.

  17. andy

    Winter Toad: the question then becomes, where do these perturbative methods fail? I’d suspect you could come up with some configurations where it doesn’t work so well at all, perhaps various forms of strong resonances between the planets.

  18. Wow, this is totally awesome! Thanks for sharing.

  19. Doc

    It’s a neat internet toy, but I think Celestia is more fun (and prettier) for creating solar systems.

  20. MoonShark

    Wanna see some planet-swapping and near-misses? :D Body1: m=150,Px=-100,Vy=-50; Body2: m=150, Px=100, Vy=50; Body3: m=.001, Px=50,Vy=-100; Body4: m=.001, Px=-50, Vy=100.

    P is position, V is velocity, everything not mentioned is zero. Try it starting with “fast” and run it again with more accuracy each time :)

  21. Andy: one has to define “fail”. Where does “integrate the sum of all forces” fail? Well, it doesn’t really fail, it just gives incorrect results if you drive it out of its range of applicability. The perturbative approach is still just integration of forces, but it kind of separates out the one major force and lets the smaller forces adjust the known closed-form solution due to that one. If there is no dominant primary mass in the system, if you’re modeling the mutual gravitational interaction among several equal-mass objects, then the perturbative system isn’t really useful. You can apply it, but as the perturbations are similar in magnitude to the forces they’re “perturbing”, it really breaks down to no better than the naive integrate-the-sum-of-all-forces approach that everybody seems to use instead.

    The perturbative approach is fed into an integrator. If your integrator is competent, it will recognize when the step sizes are too large to give confidence in the results. As a general rule, for realistic systems with one heavy object and multiple lighter objects, the perturbative approach will do much better than the brute-force approach. At the other extreme, for, say, a Klempere rosette of three equal-mass objects, it will likely do no worse.

    The math involved in the perturbative approach is (much) more complicated, but it’s not any less correct, when correctly applied. I suspect the reason it isn’t more widely used is that the derivation and expression of the perturbative forms is difficult. You can’t point at a term and say “this is the force due to body #5″.

  22. Caroline

    I just spent half an hour giggling at the collisions I had created. Thanks!!!

  23. So I can build one of those crazy 12-world solar systems like in Battlestar or Firefly?

    Moons too?

    Or is that v.2.0?

    -r.c.

  24. MoonShark

    Dead-Stop… or Not. Pick the Four Star Ballet preset, then change the Py values of the first two stars to 99 and the other two to -99. Set the accuracy to 50, 60, 80, or 90% for different patterns with a similar “ending” (and keep watching after the collision), or to 70% or 100% for two different endings :)

  25. Crux Australis

    Doc: can you build systems in Celestia?

  26. Dwight Bartholomew

    I noticed (in your example of sun, planet, moon) that the moon orbit never goes “against” the orbit of the planet (that is, from a sun-centric overlord viewpoint). I mean, the moon is never in retrograde… am I making sense? Anyway, that sort of says the moon’s orbit is around the sun with a perturbation by the planet. So, is it really a “moon”? Or is it a binary planet system?

  27. I think I’ve got a stable Mercury, Venus, Earth system – of course, solar mass isn’t to scale with the planets (it would be 332,900 with Earth at 1). But distances are to scale, and the planets’ masses are to scale with each other.

    Body 1 (Sun): mass 500, other fields 0
    Body 2 (Mercury): mass 0.055, Px 77, Vy 250, other fields 0
    Body 3 (Venus): mass 0.815, Px -145, Vy -182, other fields 0
    Body 4 (Earth): mass 1, Py -200, Vx 156, other fields 0

  28. Jasini

    Ooo! Spirograph!

  29. Mort

    If you want a fun variation:

    Take the sun, planet, moon preset

    Change the planets mass from 10 to 8.

    The moon gets unstable and goes into an ecliptic orbit around the sun. It gets picked up again by the planet… Then gets lost into a solar orbit again… Then gets picked up again by the planet…

    crazy.

    Edit:
    It seems the simulations are truly chaotic… I get different results… It gets picked up again fairly often, but not always… sometimes it gets lost into outer space…

    Use the 3rd speed postition from the right.
    2nd from the middle.
    8th out of 11 speed markers…

  30. I’m trying to make a system with a single planet around a sun with two moons, but my moons either rocket off into space, get captured / swallowed by the sun, or crash into the planet or the other moon.

  31. dcsohl

    Back in the day… way back in the day… I had a program called, IIRC, “Gravity” on my Mac SE/30 that did this sort of solar system simulation. Fascinating to see that you can now do it on a web page with Flash! Love it!

  32. wow, some funny orbits going on here. Start with the presets for a four-body system, but change the mass of body #4 to 1,000. The yellow mass was absorbed and one of the remaining bodies had a very square orbit. Tweak it some more and you’ll get figure eights and other strange geometric orbits.

  33. Oli

    I’ve been using that program for a few months now. It’s really great. I just hope that they update it and put more presets, soem sort of save feature and more objects (4 is not a lot) in. But it’s great anyway =)

  34. MoonShark

    Trinary Planet Nailbiter Switcheroo: Start with preset Hyperbolics, then change the masses to 721, 10.3, 9, and 6.7 respectively. Set accuracy to 80%. Whee!

  35. stogoe

    Looks like there’s a stable (up to t=140) planet with two-moon system just by adding a 4th body to the Sun, Planet, Moon preset at m=.001, Px=130, Vy=65.

  36. Winter Toad,

    I think the best approach depends on your goals, as well as the system being modeled. If you are trying to navigate Dawn to Ceres, or determine if Apophis will go through the keyhole, the perturbative approach is faster (in computer time) and more accurate when run over the same number of CPU cycles, but if your goal is to give people a feel for how multi-body Newtonian systems behave (either as students writing the code or as students or the general public playing with the models), this approach is much better since you can see the forces and how they evolve. Once they fully understand what’s going on, you could introduce advanced topics such as the very hairy math to derive a perturbation model of the same system. A model T is a better choice for teaching introductory auto mechanics than a 2010 Corolla, even though no one builds cars like that any more.

  37. IBY

    I made two planets rotate at opposite end of each other to a star, and made a planet become a moon, and a planet again before it plummeted to its doom, and I made a planet with two moons. Pretty fun.

  38. I remember a program like this back in the Apple II days. Great fun making planets crash.

  39. Phil (and Brian) : I also remember a similar program, but not as good, back in the Apple II days. This is on my list of things to do with my kids tonight. As a (former) nuclear physicist who’s always looking for cool ways to demonstrate science to kids, being the ruler of your own little solar system is just about one of the best!

  40. S. R. Nethergael

    I have to say this was quite useful in trying to find out what kind of distances and masses are useful in coming up with a fictional binary planet system I’m using for a story of mine. Try this one out:

    Body 1 – M=3309; P=x0/y-1400; V=x0/y0
    Body 2 – M=.01; P=x0/y100; V=x-140/y0
    Body 3 – M=.012; P=x0/y101; V=x-130/y0

    The first body represents a star with a mass equivalent to our sun, the second is a planet with a mass comparable to Earth, and the third is a second planet orbiting very close to the first with 20% greater mass. The distances would translate to the second body being 150.0 million km from the star, and the planets being 100,000 km apart from each other. Would certainly light up the sky a lot more than the full moon does. :o

    Also be sure to keep the speed down or the planets will throw each other out of orbit.

  41. PhET is one of my favourite sites. I run about half of my physics course through the sims. The circuit kits are particularly good for intro electricity.
    Here is another orbit visualizer, for our solar system:
    http://www.gunn.co.nz/astrotour/?data=tours%2Fretrograde.xml

  42. Nooooo. I made an interestingly stable 2-moon planet, and it worked perfectly… until time 114 in 100% accuracy, when the sun snatched up one of the two moons :(

    Edit: And then the other moon crashed into the planet at about 150. Sun’s moon is still spinning happily around though.

  43. DavidB

    Awesome. This work day is shot. I made a stable binary system with a planet orbiting both stars on the outside in the opposite direction. Body 1 mass – 150, position – (-100,0), velocity – (0,-60). Body 2 mass – 150, position – (100,0), velocity – (0,60). Body 3 mass – 0.001, position (0,200), velocity – (120,0). Interestingly, it fails quickly if the planet has the same velocity, but in the other direction.

  44. AJ

    In between this and Celestia in terms of accuracy and prettiness comes ‘Universe Sandbox’ ( http://universesandbox.com/ ). There’s a good few preset systems on that, at all sorts of different scales – from dice to galaxies. Plus, you can play pool with planets, if you like… (quote-spotting time!)

  45. BB

    I used to play with programs that did this type of thing in DOS on my 386 way back in the day. Then there was a cool GUI-based one on the school’s Mac computers that had little graphical vectors representing velocity that you could click/drag before turning the simulation on. This feels more simplistic than either of those.

  46. Tom

    This is a fun one:
    take the three body problem, set the 3rd planet to M=1, Px =-166, Vy=-74, accuracy to max, and let ‘er go. It starts to get weird at t = 180, then the smaller body gets ripped out of its orbit by the large one and goes from planet to very erratic moon-until it crashes into the larger one at about t=250

  47. @AJ -

    As in Arnold Judas Rimmer?

  48. Use a little trig and you can build a L4 Lagrange orbit!

    200/0/0/0/0
    1/200/0/0/100
    .001/100/174/-87

  49. Hypocee

    If anyone wants a more “gamelike” version of this kind of thing, Osmos is a great recent release: http://www.hemispheregames.com/osmos/ Most of it is more puzzley in flatspace, but the later orbital levels put you in systems with primaries and secondaries and task you with adjusting orbital parameters and planning transfer and slingshot orbits.

  50. Plutonium being from Pluto

    Awesome thing to set up & post here BA. Thanks from this big exoplanet & SF fan! :-)

    BTW. Off topic but for the ‘ Mild Doctor Who series 5 spoilers ‘ thread would you be able to set it up to a “hide spoilers” mode where the spoilers are only visible if people shift the cursor over and deliberately highlight them or something? (Like how they do it on the, I think its called, TV tropes site.) If you could that’d be great methinks. Please?

  51. Autumn

    So when I let this run out to T=200 or so, I get a random comet flying into my system.
    It has happened every time, with a lot of different initial conditions. Unless you have the traces on, it is hard to notice, as it is tiny and almost always impacts something.
    Wow, I just returned to a sim with the little green comet trace on the screen, obviously coming back toward the three bodies I had going, I clicked the traces off and there was no trace of the comet. I then turned the traces back on, and it had disappeared totally.

  52. KurtMac

    Another galactic time-waster I can suggest would be Gravity 3D. An oldie but goodie, its a simple colliding galaxies simulator with some tweakable settings. I can sit for hours and watch collisions unfold, going “Oooh, pretty!” http://www.mars3d.com/PWGravity3D.htm

  53. Dr. Rocketscience

    I used some PhET stuff when I was teaching AP Chemistry last year in a Longmont high school. Free Java applets are a science teacher’s dream. Someday I’ll learn to code them myself.

  54. ET NL

    You may like this. Here you have a simple star system where you can add things.
    http://bit.ly/amYzDq

  55. ET NL

    This is not a game but a nice simulator showing orbits. There are also extrasolar systems to explore.
    http://janus.astro.umd.edu/SolarSystems/

  56. Cain

    Anyone figured out how to make a horseshoe orbit yet?

  57. Yeebok

    YAY! Fun fun fun ! Thanks Phil. I took your tip of using a preset then amending it a little.
    I found these settings worked quite well giving object 3 a very interesting path .. I was almost rooting for it to get wiped out but it survived quite a few orbits:
    Obj 1: – 200,0,0,0,-1
    Obj 2: 10,142,0,10,139
    Obj 3: 0.001,166,0,18,60
    Obj 4: 3, -13, -67, 124, 34.

    (settings for the test were 3 notches to the left of ‘fast’)
    With the slider as far left as possible, even on its first orbit, object 3 passes through the e in Accurate on the right, whereas on fast, it crosses that part of the screen but passes more over the R in accurate.
    This is wicked fun. My only gripe would be after a while it’s hard to spot where your object is in it’s path.

    @RPJ : That’s way cool!
    twitpic of run1 (fastish) – http://www.twitpic.com/166jlp
    twitpic of run 2(slow) – http://www.twitpic.com/166k1y

  58. Yeebok

    @Cain I suspect you throw the horse shoe up .. very high ..

  59. I managed to get a stable Sun, Planet + 2 moon system.
    Funny thing though is that one moon orbits clockwise, the other counter-clockwise.

    Settings:
    Sun 200, 0, 0, -1
    Planet: 10, 142, 0, -26, 128
    Moon 1: 0.001, 166,0,-31,68
    Moon 2: 0.001, 127,-3,-24,65

  60. Tim G

    I once simulated how planetary orbits would behave in the Alpha Centauri system. I discovered that IF planets could form in the habitable zones, the semi-major axises would remain very stable but the eccentricities would cycle over a period of a few thousand years. A habitable planet around star A would have an eccentricity versus time plot with a greater peak-to-peak amplitude and shorter period than that of its counterpart around star B. I used a ninth order symmetric multistep method.

    I would love to see a free application that takes it to the next step, allowing the user to create characteristics of the planet itself. Create your own planet with continents, vegetation, snow cover, ocean currents, atmospheric composition and density, rotation rate, tilt, etc. and then do a crude simulation of weather (which would be influenced by the orbit).

  61. I decided to use this to simulate a Planet X scenario. You know, that “mystery planet” that conspiracy theorists claim is always behind the sun in relation to us. To simplify matters, I did the Sun, Earth and Planet X (exactly like the Earth but with opposite velocity). I got a pretty stable system. Then I realized that Venus and other planets should affect their orbits. Given the 4 body limitation, I decided to add Venus (using the values supplied by @Carey).

    Things seemed ok at first but then the orbits starting wobbling. Planet X would have been visible to Earth quite a few times. The Earth dipped in, became a Venus moon for awhile and then sunk into an orbit closer to the Sun than Venus. Venus shot out beyond Planet X which got a Pluto-like orbit (only closer to the Sun). Eventually, Earth and Venus collided shooting Venus out only to have it come crashing back into the Sun.

    Currently (at about the 600 mark), Earth is approximately in Venus’ old orbit while Planet X wildly swings between Earth’s old orbital distance and somewhere around Jupiter. (The last one’s a guess as it goes off the screen for some time. Could be further out.) This seems relatively stable at the moment. Of course, had Mars or Jupiter existed in this model, I’m sure Planet X would have wrecked even more havoc. In short, Planet X couldn’t simply be “hiding behind the Sun.” To quote Adam and Jamie: Myth busted!

  62. @Mathias R.:

    Congratulations, you have done what I haven’t done.

    Edit: Strike that, so have I:

    200/0/0/0/-1
    10/150/0/0/120
    .001/175/0/0/50
    .001/125/0/0/50

    NOOOOO!! 750 or so, blue moon crashed into the planet! Sucks…

  63. I love how in a simple 3 body system, a moon orbiting a planet orbiting a sun, the moon’s path relative to the sun can be almost a perfect square! Cool.

  64. Cochise

    I’ve been addicted to Orbiter lately, http://orbit.medphys.ucl.ac.uk/
    It’s a free space flight simulator with a ton of add-ons. The learning curve is pretty steep so read some tutorials that comes with it and on the forum. Theres a lot of vehicles you can use, both fictional and non. I’ve made it to the Moon, Mars, and, Jupiter so far. Also successfully docked with the ISS. The physics are realistic so you need a basic knowledge of orbital mechanics. The lastest beta is out at http://www.orbiter-forum.com/

  65. Lukas

    @ Kevin:
    set your solar mass and your planet velocity to zero. Then tweak the two moons until you think you have something stable. Low masses for the moons reduce the chance for them to perturb each other’s orbits.
    Then set a normal solar mass again and add the same number to all the planet and moon vectors, to get the planet-moon system moving around the sun.
    Here’s one that seems stable:

    450/0/0/0/-1
    10/300/0/0/120
    0.001/320/0/0/54
    0.002/260/0/0/170

    cheers

  66. Lukas

    a moon with a moon…

    90/0/0/0/-1
    5/270/0/0/60
    0.25/298/0/0/100
    0.005/301/0/0/120

    (worked for me at 20% speed for at least two “years”.. but at some point the tiny moon got lost, not sure how)

    this is fun :)

  67. Jackson

    @Cain, I managed to do that with a 3 body system similar to Saturn, Janus and Epimetheus, with body 2 and 3 having similar mass. Problem is that it takes a long time to see the two bodies trading orbits. But it works.

  68. Jackson

    One more just for fun. A planet with a moon orbiting a binary star system.
    150/0/0/-3/-64
    120/77/-1/4/120
    10/-194/-5/-1/123
    0.001/-208/-8/0/23
    The moon however has a very large ratio between it’s apoapsis and periapsis.

  69. J. D. Mack

    Here’s my fun set up. Three bodies with unstable orbits around the sun. Green body briefly captured by blue body. Major collision with red body leaves no green body and red and blue bodies gravitationally bound in a somewhat stable orbit around the sun. Eventually, the planets collide.

    200 /0 /0 /0 /-1
    5 /-1/ -126 /150/ 0
    4 /170 /4/ 1 /111
    2.501 /96 /115 /-47 /63

    J. D.

  70. Robert E

    250 / -200 / 0 / 8 / 0
    0.001 / -115 / 0 / 0 /155
    0.001 / 50 / 0 / 0 / 60
    0.0750 / 152 / 106 / 0 / 37

    4th planed routinely shifts the orbit of the first and second planet, but so far (with maximum accuracy and at 300 time), they still have ‘stable’ orbits. I would assume that the times at which the orbits shift would be a bad time to be vacationing there.

    OOPS: typing this, at some point between 300 and 317 the orbits shift a lot — orbit of the first planet gets much larger.

  71. Robert E

    Hm, whats the longest someone has let this run?

    My second planet had huge shifts in orbit at 533 & 646 and has continued to have small changes; first planet is mostly stable.

    Current time is 1604.

  72. Blerk

    Smaller inner planet has its orbit disrupted by other planet, orbit becomes eccentric and it eventually migrates outward and becomes the outer planet (around T-250). I’ve let it run as long as T=1100 and it what appears to settle into a somewhat stable orbit.

    200/0/0/0/0
    1/203/-1/-1/89
    0.001/123/-5/-2/119
    Slider in middle

    If you run it on fast it settles into a higher orbit as well but eventually gets bullseyed into the star around T=950

    Great link lot of time wasted on that today :)

  73. Felix D.G.

    Body 1 (Sun)
    800 / 0 / 0 / 0 / 0

    Body 2 (asteroid A)
    .001 / 126 / 0 / 0 / 252

    Body 3 (asteroid B)
    .001 / 140 / 0 / 0 / 239

    Body 4 (Jupiter)
    1 / 200 / 0 / 0 / 200

    Asteroid A is in 2:1 resonance with Jupiter. Asteroid B is not. See the difference.

  74. Gebo

    This is much more fun than playing Tetris!

  75. Denver Astronomer

    Here’s a cool one – four bodies of equal mass quickly turning into a three body problem where one body gets ejected, returns, ejects another body, rinse, repeat

    200 -20 0 0 -100
    200 20 0 0 100
    200 -180 0 0 100
    200 180 0 0 -100

  76. Your name here

    @Denver Astronomer

    What accuracy?

  77. Denver Astronomer

    Sorry – In two clicks from the far left (most accurate – 2)

  78. Joe

    Photobucket

    I made made what I thought would be a nice balanced earth/moon orbit. I realized that a pattern like this one could run for eons, so I let it run all night. Pretty neat!

    I wonder if this is a pattern similar to the celestial body that impacted with proto-Earth and produced our moon? I’m fascinated! I want to just let it run and see if they ever collide.

  79. Lukas

    I call it the sunflower… get it? ahahaha! ohh.. I’m so funny

    100/-50/0/0/71
    100/50/0/0/-71
    0.06/80/0/0/76
    1/-20/0/0/-249
    (accuracy: second click from left)

    but seriously.. the 4th body’s orbit is very strange. At the closest point it’s orbiting body #1 at the farthest body #2, intersecting all other orbits.

    It’s surprisingly stable too. didn’t crash yet on my watch

  80. vrs

    @MoonShark (20): even better (some very interesting patterns, then crash):
    150/-100/0/0/-50
    150/100/0/0/50
    5/50/0/0/-100
    5/-50/0/0/100
    http://img215.imageshack.us/img215/4152/2010031044.png

  81. Lukas

    Three bodies sharing one orbit:

    400/0/0/0/-1
    0.1/0/150/-164/0
    0.1/108/-108/113/115
    0.1/-108/-108/115/-113

    not completely stable (at least in fast; but interesting positions; most of the time the system keeps itself from getting out of whack)

  82. Your name here

    A very unstable stable 3 planet system:
    Body 1: 200, 0, 0, 0, 1
    Body 2: 1, 100, 100, -50, 50
    Body 3: 1, 150, -150, 50, 50
    Body 4: 1, -200, -200, 50, -50
    Accuracy: Default (30% accuracy or 70% speed or 2 to the right of the half mark)

  83. Arthur Maruyama

    Fun 4-body:
    200,0,0,0,-1
    10,142,0,0,140
    10,166,0,0,74
    10,-107,0,0,-133
    accuracy at max

    Blue and magenta start out co-orbiting each other, then green disrupts the system and tosses blue out and goes into a co-orbit with magenta.

    Change the last number from -133 to -137 and green and blue go into a co-orbit tossing out magenta which falls into a short cometary-like orbit.

  84. Arthur Maruyama

    Again, using the numbers in my last post but change the last one to -124 and you get a double exchange of co-orbits.

  85. Your Name Here

    Found another one, basically a unstable stable star and planetary system:

    Body 1: 200, -245, -124, 0, 0
    Body 2: 0.001, -332, -118, 0, 150
    Body 3: 200, -56, 132, 0, 0
    Body 4: 200, 141, -120, 0, 0

    Accuracy: 100% accuracy or 0% speed or all the way to the left.

    Turn ‘system centered’ off.

    I got this while looking for a horseshoe orbit one.

    EDIT: It doesn’t seem to work anymore. Hmm.

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