
Gravity Simulator - evanb
http://www.nowykurier.com/toys/gravity/gravity.html
======
simonswain
I did something similar, but with combat - ships, lasers and missiles.

There are a couple of variations, and some tweaks like the ships accelerating
perpendicular to the planets so they don't crash land.

[http://codepen.io/simonswain/full/ftEjD/](http://codepen.io/simonswain/full/ftEjD/)

[http://codepen.io/simonswain/full/CeHmh/](http://codepen.io/simonswain/full/CeHmh/)

~~~
NathanKP
Very cool. I notice that many ships tend to get stuck on the edge of the map
though. Maybe make it so they loop back around to the other side of the map?

~~~
simonswain
Thanks. Yeah, there are a couple of glitches in there. The ships bounce off
the edge of the screen, and smaller ships run from bigger ones -- combined,
that makes them crawl along the sides. Looping around is a good idea, or I'm
wondering if there could be some kind of log scale to distance the further out
from the centre the ships get. I did a variation a while back with a star in
the middle that could be tweaked for that (click to add a ship). Mind you, the
gravity from the star pretty much takes care of that problem.

[http://codepen.io/simonswain/full/cKejC/](http://codepen.io/simonswain/full/cKejC/)

------
p4bl0
It's really nice. Be sure to activate paths, I'm having a lot of fun using
that to draw cool stuff :).

[https://i.imgur.com/j3YwI5y.png](https://i.imgur.com/j3YwI5y.png)

That was me trying to have a small particle making an 8-shaped path around two
bigger ones that would be sufficiently far apart to not interact too strongly
with each other. Of course, when the small particle went between the two
bigger ones, it shifted their position a tiny bit, but sufficiently for those
two to start very slowly moving towards each other, while the small particle
was headed straight to the up-right direction. But when the two bigger
particles became close enough to finally meet and become one single huge
particle, it attracted back the small one, which since then goes back slowly
to the huge particle only to shift it a bit and be "relaunched" by it for a
new lap. The system seems to be totally stable that way.

Update: [https://i.imgur.com/heHekdc.png](https://i.imgur.com/heHekdc.png)

~~~
exDM69
> That was me trying to have a small particle making an 8-shaped path around
> two bigger ones that would be sufficiently far apart to not interact too
> strongly with each other.

This kind of path is called a free return trajectory and was used in the
Apollo program lunar missions. The trajectory is not periodic, ie. it doesn't
repeat more than once. The trajectory around the earth takes less time than
lunar period ("month") so when the craft goes back up, the moon has moved on.
You _might_ be able to construct a planet-moon system with an m:n resonance in
the orbital periods of the moon and the craft so that the tracjetory is
periodic.

Free return trajectories are used in manned space flight to guarantee that the
craft and crew return to earth if a failure prevents from entering lunar
orbit.

------
lutusp
Quote: "Particle mass is log of radius". Why not use real physics and make the
mass proportional to the cube of the radius? It's also easier to compute. In
fact, taking the log of the radius goes in the wrong direction -- the mass of
a planet really does increase as the cube of its radius, which changes in a
way opposite to log().

Oh, well. Here's my gravity simulator -- it uses JavaScript, no flash
required:

[http://arachnoid.com/orbital_dynamics](http://arachnoid.com/orbital_dynamics)

~~~
Udo
_> "Particle mass is log of radius"_

They seem to have corrected the sentence now: "particle radius is log of
mass".

Wow, your simulator is much nicer, plus a great article about it to boot! You
should add an option to play cosmic billiard, that's probably the main appeal
of the flash simulator :)

~~~
lutusp
Thanks for your kind comments!

> They seem to have corrected the sentence now: "particle radius is log of
> mass".

It's still wrong. Here's a graph comparing mass = e^radius (the reciprocal of
radius = log(mass) ) versus mass = radius^3:

[http://i.imgur.com/XkVFgIH.png](http://i.imgur.com/XkVFgIH.png)

My point is that the two functions have a different behavior, the absolute
values generated aren't very important compared to that. For solutions to f =
G m1 m2 / r^2 where both bodies are computed, this will produce results wildly
different than reality. (If only one body is computed, for example against a
much larger parent body mass, the satellite mass stops making a difference.)

> You should add an option to play cosmic billiard, that's probably the main
> appeal of the flash simulator :)

Nice idea. I was more interested in portraying the solar system using real
planetary masses and real physical constants. Still, it's a nice suggestion.

------
zaptheimpaler
Very cool! I was able to get 2 masses to oscillate around each other in a
funny way[1]. Seems they keep going like that forever. What is this kind of
equilibrium called?

[1][http://imgur.com/FQYpo9V](http://imgur.com/FQYpo9V)

~~~
xioxox
Isn't that a normal orbit around a common centre of mass? As the objects have
a similar size the centre of mass appears to wobble as it moves along. In the
frame of the centre of mass, the objects would just go round in standard
orbits.

~~~
raverbashing
Yeah

That's the thing with those kind of simulators (or, actually, with reality),
your reference has no relation to the center of mass of the system.

Of course, if you "were there" the reference would be the center of mass, like
the reference of the solar system is "The Sun" (or a point inside it)

~~~
jessriedel
The center of mass of the solar system isn't always within the Sun.

[https://en.wikipedia.org/wiki/Barycentric_coordinates_(astro...](https://en.wikipedia.org/wiki/Barycentric_coordinates_\(astronomy\))

------
simonbarker87
If you're interested in learning some of the basics behind this kind of
simulation I highly recommend the Nature of Code by Daniel Shiffman - lots of
physics and programming fun.

[http://natureofcode.com/](http://natureofcode.com/)

------
zalmoxes
This is nice, but please rename the OMFG button. As someone who works in K-12,
it would be a shame if a program like this is rejected because of a button.

~~~
bengali3
agreed. This is really cool (and simple too)

Also, how hard would it be to set an initial state of our current solar
system? Teachers could set up scenarios for students to interact with, and
allow students to collaborate.

Maybe as simple as an output/input of textual data for saving & restoring
state? i'd love to try model our current solar system, and see if i can get
something to mars with just an initial trajectory.

see:

[http://en.wikipedia.org/wiki/Interplanetary_Transport_Networ...](http://en.wikipedia.org/wiki/Interplanetary_Transport_Network)

~~~
baddox
The scale of the Solar System would require you to visualize the bodies as
much larger than their true size in order to see everything on one screen. If
the Sun is 1 pixel, all other bodies are way smaller than a pixel, and Neptune
is 3000 pixels away. And of course, you'd probably want to speed up the
simulation speed.

------
kator
Very nice, wish it was HTML5 rather then flash.. It brings to light how hard
it is to get a stable solar system. And of course I knew this but playing
around I realized our sun is not stationary either... It's easy to forget the
entire solar system we live in is this amazing mix of interactions between the
planets, sun, other debris and outside mass from other parts of the universe.

~~~
mathu7
Can someone explain the math behind this? Which methods were used? I wasn't
aware it was possible to run such a simulation on flash because each body
results in 6x more calculation. Is this like plugging in the masses into a
single equation? I want to learn more about how this is done .

~~~
nanofortnight
The simplest numerical approximation method is Euler's method. It also tends
to be unstable.

Personally I prefer to just throw a fourth order Runge–Kutta (RK4) at things
and normally that's more than good enough.

List of reading:

[http://gafferongames.com/game-physics/integration-
basics/](http://gafferongames.com/game-physics/integration-basics/)

[http://en.wikipedia.org/wiki/Euler_method](http://en.wikipedia.org/wiki/Euler_method)

[http://en.wikipedia.org/wiki/List_of_Runge%E2%80%93Kutta_met...](http://en.wikipedia.org/wiki/List_of_Runge%E2%80%93Kutta_methods)

[http://mathworld.wolfram.com/Runge-
KuttaMethod.html](http://mathworld.wolfram.com/Runge-KuttaMethod.html)

[http://en.wikipedia.org/wiki/Linear_multistep_method](http://en.wikipedia.org/wiki/Linear_multistep_method)

[http://en.wikipedia.org/wiki/Bulirsch%E2%80%93Stoer_algorith...](http://en.wikipedia.org/wiki/Bulirsch%E2%80%93Stoer_algorithm)

~~~
exDM69
> Personally I prefer to just throw a fourth order Runge–Kutta (RK4) at things
> and normally that's more than good enough.

In the context of gravity simulation, I must point out that while Runge-
Kutta/RK4 is good enough for a lot of stuff but it has a tendency to dissipate
energy. It's not very good in a simulation where the conservation of energy is
important. Run a simulation long enough and the orbits will eventually shrink.

If scientific accuracy is required, gravity simulations are usually done with
"symplectic" integrators (which don't "lose" energy) and the equations of
motion are written using Hamiltonian mechanics. There are symplectic variants
of Runge-Kutta too.

In an exercise work for a celestial mechanics course, I wrote an n-body
simulator using a dissipative Runge-Kutta method (because it was good enough
for that, and the exercise was about using RK methods). Simulating an
exoplanet system (HR 8799), the orbits were stable and 100 year simulation
gave near perfect orbits. After 1000 years, there orbits were a bit smaller
and after 10000 years, they had lost a fourth of the initial energy. This was
done using one day timesteps.

[http://en.wikipedia.org/wiki/HR_8799](http://en.wikipedia.org/wiki/HR_8799)

------
pp19dd
Reminds me of orbitalis - a Ludum dare game from last year that eventually
ended up on steam. Object is simple, establish a stable orbit in the system
for a span of one clock rotation (clock is on the very outside.) See
[http://www.alanzucconi.com/extra/0rbitalis/ld48/](http://www.alanzucconi.com/extra/0rbitalis/ld48/)

------
kgabis
I once wrote a similar simulation in C:
[https://github.com/kgabis/gravitysim](https://github.com/kgabis/gravitysim)
It uses Barnes-Hut algorithm, so it runs in nlogn, instead of n^2.

------
bochi
I did something similar in Javascript. My implementation uses the Runge-Kutta
algorithm, that is more stable. My GUI does not allow planet creation, but it
shows several stable configurations, including the 13 recently found three
body planar orbit configurations.

[http://jbochi.github.io/planets/](http://jbochi.github.io/planets/)
[http://suki.ipb.ac.rs/3body/](http://suki.ipb.ac.rs/3body/)

------
gdh73
Love this. I managed to get a pretty stable orbit by using the right angle and
velocity (by chance). Highlighted in yellow:
[http://i.imgur.com/OOaTLMP.png](http://i.imgur.com/OOaTLMP.png)

~~~
guiomie
This is the coolest trajectory found on this thread for now!!!!

~~~
gdh73
It ran for several hours like that and never deviated from the original
"circular" path. Unlike the other attempts, which were all much more
elliptical. I guess that's kind of how planets would stay in a stable orbit
though, having the right distance and speed for their mass.

------
chops
I, like many others on this thread, have dabbled in the Gravity Simulation
game. I've done two of them.

The first one was back in 1999, I wrote one with 13h[1] graphics for DOS
(Borland Turbo C++), and to make it more fun, I used flat sprites to represent
the objects (so the objects progressed from being rocks to asteroids to
planets - with the largest sprite I used being an image of Jupiter).

A few years later, I rewrote it in OpenGL (using the GLUT library) for a
class. It worked much better (and of course the hardware was much faster too).

I had always planned rewriting the physics engine to use Barnes-Hut, but never
got around to it, so it always ran at N^2.

Anyway, for the curious, the code is up on Github amongst my collection of
other old garbage stuff from back in the day:
[https://github.com/choptastic/OldCode-
Public/tree/master/Gra...](https://github.com/choptastic/OldCode-
Public/tree/master/GravSim)

[1]
[http://en.wikipedia.org/wiki/Mode_13h](http://en.wikipedia.org/wiki/Mode_13h)

------
exDM69
Here is Universe Sandbox, a gravity simulation that can do massive scale
simulation on home computers. Neat demo videos about colliding galaxies, etc.

[http://universesandbox.com/](http://universesandbox.com/)

------
p4bl0
Can anyone explain the graphical effects that appears here in the white lines
[https://i.imgur.com/sRCLAsn.png](https://i.imgur.com/sRCLAsn.png)
[https://i.imgur.com/81Jf56H.png](https://i.imgur.com/81Jf56H.png)?

(To reproduce, use a really big stable mass (either enter it by hand or use
the OMFG button and click several time at the same position without moving
your mouse) and launch at fast speed a tiny particle in an approximately
tangent direction of a circle centered on the big mass.)

~~~
hughes
That's a Moiré pattern and is an interaction of the resolution of your display
and the proximity of the lines.

[http://en.wikipedia.org/wiki/Moir%C3%A9_pattern](http://en.wikipedia.org/wiki/Moir%C3%A9_pattern)

~~~
p4bl0
That was quick! Thanks!

I didn't know that Moiré pattern could appear on a screen "without" a second
grid (or rather, I didn't realize that the pixels of my display could serve as
the second grid, which is kind of obvious now that you said it).

New screenshots: [https://imgur.com/a/7W9FI](https://imgur.com/a/7W9FI) :)

------
tuzemec
Relevant: [http://codingmath.com/](http://codingmath.com/) Really nice series,
showing how to do vectors, gravity and so on in JS.

------
Zeebrommer
Ok, maybe I should finally buy Kerbal Space Programme

------
quarterto
Built something similar in C/GL a few years back. Quite a fun exercise, it
only took a couple of hours to get the basics working. It has no collision
detection, so particles that end up too close end up with infinite velocity,
which is quite fun to watch.

EDIT: oh hey, I found a binary.
[https://www.dropbox.com/s/ihfqnzjaxhtskwt/Screenshot%202014-...](https://www.dropbox.com/s/ihfqnzjaxhtskwt/Screenshot%202014-09-08%2009.59.20.png?dl=0)

[https://github.com/quarterto/Yay-Physics](https://github.com/quarterto/Yay-
Physics)

------
programmarchy
Can I play? I wrote a RK4 gravity simulator a while back in WebGL, but my main
goal at the time was to find a way to visualize gravitational fields, so its
nowhere near as interactive or user friendly as your implementation.

I was trying for the effect you see in high school physics videos. My approach
was to use a plane geometry mesh and apply a vertex displacement shader, but
never quite got it to look or perform how I wanted.

[http://programmarchy.github.io/gravity](http://programmarchy.github.io/gravity)

------
Aardwolf
Wow this is fun. But it has so much potential for improvements!

    
    
      -Saving your setting
      -Undo-ing
      -Auto generate small object in perfect circle orbit around larger object, and generate sun-earth-moon system
      -Export setting to other people
      -Allow to numerically finetune locations and velocities
      -Don't ruin the trails when dragging
      -Make it run faster, especially with trails enabled
      -etc... :)
    

EDIT: Gee, when will Hacker News finally support newlines properly?

~~~
luckyno13
I would like to name individual "bodies," the ability to zoom in and out, and
maybe even a mathematical readout of some sort. The values behind trajectory,
etc.

------
bdaver
I've made touch interactive installation at 2008 with similar physics
simulation [http://vimeo.com/19361057](http://vimeo.com/19361057)

------
alandarev
Such an amazing simulator to play with. I can only imagine how breath-taking
this can be for kids to play around, plus it teaches physics!

~~~
TeMPOraL
Think about how breath-taking and educating must it be for a kid to _write_
such a thing.

As a person who actually learned basic mechanics by writing video games I do
believe that "you ain't understood nothing until you know how to teach it to a
computer". Trying to express knowledge in (working) code is a great exercise
that mercilessly catches even tiny holes in one's understanding.

~~~
kator
Ditto that, I often tell people computers are very stupid. One proof of that
is they let humans program them. The second proof is you have to teach them
everything from scratch. :-)

------
mkoryak
I have a question about a phenomenon I am seeing.

say you add 3+ equal mass objects without a velocity and they all collide with
each other without "missing or orbiting" one another. Sometimes the final mass
will have a velocity.

It would seem like it should not have a velocity because it would be canceled
out. What am I missing? Where is this energy coming from?

~~~
lutusp
In real life, the three colliding bodies would convert their kinetic energy
into heat and combine into a very hot body. Sort of how we think the moon was
created, from a Mars-sized body colliding with Earth long ago.

But in a numerical simulation, usually what happens is that three bodies on a
collision source approach one another but, because of the limitations of
numerical differential equation solving, suddenly fly away from each other in
a rather non-physical way, and with more energy than they had to begin with.

The tl;dr: most of the funny effects in a simulator arise from the limitations
of numerical simulation methods, and many of those aren't representative of
real physics.

------
alokdhari
Hey.. TBH its real fun to play with it.

Question.. How big is the frame? I create two objects and they went out of
frame. Then I create 2 more but a bit bigger ones and after 2-3 minutes I see
those two objects coming back and it looks good too :D .. check it out
[http://imgur.com/IBYeysm](http://imgur.com/IBYeysm)

~~~
fake-name
I don't think there is a "frame". It solves for all particles all the time.

After all, if a particle leaves the viewport, it doesn't affect the particle
count readout at all.

I assume if things move far enough, there would probably be interesting
floating-point precision errors, but I'd imagine that would take quite a
while.

------
DecoPerson
I think I just learnt something about gravity and oscillations:
[http://i.imgur.com/OrUUFj7.png](http://i.imgur.com/OrUUFj7.png)

Using the rapid-click feature on my mouse to place a dense circle outline:
[http://i.imgur.com/14IN5pi.png](http://i.imgur.com/14IN5pi.png)

~~~
mkoryak
And I think I just learned something about all of your open tabs and bookmarks

~~~
DecoPerson
Hope it's useful :)

------
masswerk
For historical interest: Here's a description of the humble beginnings of
gravity put onto a computer's screen (think of PDP-1 Spacewar! code, 1962):

[http://www.masswerk.at/spacewar/inside/insidespacewar-
pt6-gr...](http://www.masswerk.at/spacewar/inside/insidespacewar-
pt6-gravity.html)

------
arikrak
Cool, it's a good way to teach people about gravity. Most people don't know
the basic idea of how falling and orbiting are connected. I once made a simple
'game' for this purpose:

[https://www.learneroo.com/modules/2/nodes/42](https://www.learneroo.com/modules/2/nodes/42)

~~~
jheriko
really? i do remember the wow moment when i worked it out for myself but i was
pretty young...

------
Zardoz84
I did something similar on 3d but is not on realtime and generate outputfiles
that could be ploted with gnuplot. It uses an third order Euler integration.
Some day I should write a realtime mode for it:

[https://github.com/Zardoz89/nBodySim](https://github.com/Zardoz89/nBodySim)

------
empressplay
This is pretty cool! I wonder if there's a way I could implement that somehow
into our turtle graphics app. Turtle gravity?

As for this app it would be awesome if you could zoom out -- I find most of my
stable(-ish) orbits are very long and at very large mass sizes, so it would be
good to see their entire orbits.

------
jokoon
did the same thing with box2d and sfml. not very hard to do...

a funny thing to do is to try to put those into a stable orbit

------
junku901
Does anyone know why perihelion moves in this simulation? I learned that
perihelion movement can only be explained by general relativity, not newtonian
mechanics. Is this just a limit of computer simulation? (which can't calculate
the exact value of Gm1m2/r^2)

~~~
vhffm
It is a shortcoming of the integrator (Euler), not in the calculation of the
force (as you suspected).

See [1]. Especially slides 11 and 12 may be of interest.

[1]
[http://www.astro.sunysb.edu/phy277/lect30.pdf](http://www.astro.sunysb.edu/phy277/lect30.pdf)

As a sidenote, there are better integration schemes, but all of them will have
some error because we discretize the system.

~~~
junku901
Wow that is really interesting. Thanks. By the way, if there are always some
error in all systems, then what kind of systems are used by NASA or other
space exploration institutes?

~~~
vhffm
I'm not in the business of space mission engineering, so I don't know details.
Sorry.

But in general, you can control the error and make a trade-off between
computing time and accuracy. You would select a timescale over which you want
the error to be below some value, and then only consider the simulation valid
until then.

------
escapologybb
I would love to know if there's a name to this particular type of orbit, I
spent a little bit too much time creating it and now need to know some more
about it! :-) Anybody know how I can find out?

[http://imgur.com/4W7eqj9](http://imgur.com/4W7eqj9)

Thanks

------
ejfox
Would love a setting to select the number of objects to drop on click, and the
spread for them ie (20 objects, 50px radius) and also for objects to gain the
mass of objects that hit them, so that if a bunch of huge objects collide,
they create a super-object

~~~
p4bl0
> for objects to gain the mass of objects that hit them, so that if a bunch of
> huge objects collide, they create a super-object

That's already what happens here.

------
blt
I made this in CUDA a while back. Fun project - the naive n^2 algorithm is
embarrassingly parallel so it's easy to write. Fun to hit the CPU/GPU switch
and watch the huge performance boost, even on a dinky laptop GPU.

------
stepstep
Be sure to click on the "Generate proto disk" button for instant action. :)

> Particle radius is log of mass.

Wouldn't it make more sense for the radius to be the cube root of mass
(assuming uniform density)?

------
ErikRogneby
This makes it easy to understand why there are so many binary systems.

------
soci
A friend of mine made something similar to this for iOS a while ago:
[http://gravityapp.info](http://gravityapp.info)

His app is being used in schools.

------
spain
Very fascinating! It reminds me of Conway's Game of Life, looking for
different kinds of patterns that will make a stable construct and do something
interesting.

------
csomar
At first I thought it was a 2D simulation but my attempt showed otherwise.

[http://i.imgur.com/roHx3wi.png](http://i.imgur.com/roHx3wi.png)

Really nice tool.

~~~
oceanofsolaris
I think what you see there is not necessarily an indication of the simulation
happening in 3-d space[1]. It is however evidence of
[precession]([http://en.wikipedia.org/wiki/Precession](http://en.wikipedia.org/wiki/Precession)),
which should not happen in a 2-body problem. If no other heavy body was close
to the ones shown in your screenshot, this should actually not happen. Since
the simulation does, however, only have a finite precision, this could very
well be an artifact of the simulation (happens often if you have near-
collisions, since the change of velocity there happens rapidly and is hard to
describe correctly with a fixed-length time step).

[1] In fact if all initial positions and velocities lie in the same 2d plane,
all trajectories would also lie in this plane. Since the interface only allows
one to set such initial conditions, I am fairly confident that the simulation
is 2d only.

------
kyberias
Similar simulation I've made earlier:

[http://newton.azurewebsites.net/](http://newton.azurewebsites.net/)

Pure Javascript using Sylvester.js for Math.

~~~
dj-wonk
Great! I wanted to say that the "add random" button tends to shoot particles
light-years away, never to be seen again. Is that what you were intending?

------
vhost-
It's pretty sweet I got this to happen
[http://i.imgur.com/Sk4Rznu.png](http://i.imgur.com/Sk4Rznu.png)

------
nodesocket
Somehow I ended up with a perfect orbit within my madness.

[http://i.imgur.com/wFReJps.png](http://i.imgur.com/wFReJps.png)

------
carlob
Why Euler? Isn't that terribly unstable?

~~~
zamalek
Only in low FPS scenarios (it becomes even worse if the FPS is low AND wildly
varies). For a toy like this there is nothing wrong with using Euler.

------
jheriko
i like how the points merge, thats what makes this more than just a dumbass
simulator imo. :)

took a while for me to work out though.

------
prothid
I lost my planet.

[http://i.imgur.com/EUK7kiE.jpg](http://i.imgur.com/EUK7kiE.jpg)

------
shentheory
So cool. The amount of time I just spent playing with that is going to screw
up my whole day tomorrow!!

------
noisy_boy
I love this but its a pity that paths vanish when I click-drag the frame.

------
Link-
When I saw the mass OMFG I was expecting a black hole to pop up :(

------
eccstartup
I think the simulation of the real gravity is better. Because we can find out
what is the hidden magic of nature. Then there comes accuracy issue of the
simulation. How to tell us that your simulation will be `correct`?

------
WoodenChair
What's it built in? Is code available? Cool demo!

~~~
sspiff
It's telling me to install Flash, so I'd say, Flash?

~~~
binocarlos
confirmed - right click -> About Adobe Flash Player

------
dharma1
this is awesome. had a look into doing this on the GPU a while ago, barnes-hut
was the best speedup I could find

There has to be a game in this somewhere...

~~~
Zardoz84
Check NVIDIA papers of doing "n bodies problem" on CUDA. They got awesome
results.

------
bipin-nag
Most awesome thing ever seen on HackerNews !!!

------
yoha
I'm stuck with an empty loading bar and

> Error #2046

~~~
TilmanGriesel
This problem can be fixed by either increasing the Adobe Flash local storage
space, (also known as “Flash cookies”) or deleting them.

~~~
snogglethorpe
How does one do that...?

I did "rm -rf ~/.macromedia/Flash_Player/" but still get Error #2046....

------
mkoryak
here is an interesting one

[http://i.imgur.com/C835B8N.jpg](http://i.imgur.com/C835B8N.jpg)

------
dudeson
Sun is the god.. (jk)

[http://s29.postimg.org/yb6ly7ybp/111.png](http://s29.postimg.org/yb6ly7ybp/111.png)

~~~
vishnugupta
NSFW warning!!

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eccstartup
It is not easy to draw a circle.

------
andreif
Next step: add dark matter

~~~
lutusp
My simulator models dark _energy_ (dark matter might be very difficult to
model, since we don't understand it):

[http://arachnoid.com/orbital_dynamics/](http://arachnoid.com/orbital_dynamics/)

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legohead
create a few random fields

turn on combine mass on collision

add galaxy in middle

watch the creation of a solar system :)

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jonifico
All of a sudden, the universe makes a helluva lot more sense now.

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shmerl
It doesn't work with Mozilla Shumway.

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jgraham
Can you file a (shumway) bug? [1]

[1]
[https://bugzilla.mozilla.org/enter_bug.cgi?product=Firefox&c...](https://bugzilla.mozilla.org/enter_bug.cgi?product=Firefox&component=Shumway)

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shmerl
I reported the issue through Shumway UI, but I can file a separate bug.

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qoobaa
> To view this page ensure that Adobe Flash Player version 10.0.0 or greater
> is installed.

What do you need Flash for?

