08/22/19 at 14:28:45 News: Registration for new users has been disabled to discourage spam. If you would like to join the forum please send me an email with your desired screen name to tony at gravitysimulator dot com.

 1 General / Discussion / Re: black hole picture  on: 05/22/19 at 03:46:57 Started by Bob | Post by Bob I see that there's a sim of the black hole at the centre of our galaxy. Perhaps someone, who knows the program better than I, can put in a disk of stars, at about 2.7 times the Schwarzschild radius for the innermost star. What happens to the orbits of those stars orbiting at all angles?     Then the next step would be to change the mass of central black hole to 1.3e 40kgs, with a Scharzschild radius of 1.930738e 13 metres. That, I take it would mean changing the eccentricities of the stars in the sim.

 2 General / Discussion / Re: black hole picture  on: 05/08/19 at 10:19:31 Started by Bob | Post by Bob It does seem to have orbital gaps in its ring system but that's before putting stars into the model.

 3 General / Discussion / Re: black hole picture  on: 05/04/19 at 10:23:23 Started by Bob | Post by Bob Is there a Kozai effect going on here? The stars that can be seen around out central black hole are inclined similarly to Jupiter's outer satellites i.e. no polar orbits.

 4 General / Discussion / Re: black hole picture  on: 04/25/19 at 23:40:39 Started by Bob | Post by Bob I think there could be a slight rabbit off with the mass I entered for the black hole. The press is saying 6.5e 9 solar masses, and the standard solar mass is taken as 2e 30kgs. However, Orbit Sim uses the mass of the sun.   2GM / c^2 = r = 1.930738e 13metres   Now that's the Schwarzschild radius i.e. the escape velocity of light, so enter that value into the diameter box of the black hole as we don't want stars in orbit to simply get "killed off" once inside the event horizon. Put a star in at that radius and it should be doing half the speed of light.     EDITED Sorry make that 0.7071 of light speed.

 5 General / Discussion / black hole picture  on: 04/19/19 at 00:53:48 Started by Bob | Post by Bob Has anyone modeled this black hole yet? It's a bit of a brute 6.5e 9 solar masses. That gives a radius of about 1.93e 13 metres and an energy density of about 0.431kgs per cubic metre. Tidal forces are very low but a star doing half the speed of light, smashing into something with about a third of the energy density of air, at sea level, is going to strip its outer layers off I would have thought.

 6 General / Discussion / Re: Autopilot in the browser version  on: 04/15/19 at 15:57:00 Started by Tony | Post by Tony Change all objects positions and velocities from ecliptic to equatorial. Put in Autopilot Now. Code:var e = Math.PI * 23.43686 / 180; for (var k = 1; k <= objects; k++) { var xec = objx[k]; var yec = objy[k]; var zec = objz[k]; var xeq = xec; var yeq = yec * Math.cos(e) + zec * -Math.sin(e); var zeq = yec * Math.sin(e) + zec * Math.cos(e); objx[k] = xeq; objy[k] = yeq; objz[k] = zeq; var xec = objvx[k]; var yec = objvy[k]; var zec = objvz[k]; var xeq = xec; var yeq = yec * Math.cos(e) + zec * -Math.sin(e); var zeq = yec * Math.sin(e) + zec * Math.cos(e); objvx[k] = xeq; objvy[k] = yeq; objvz[k] = zeq; }

 7 General / Discussion / Re: Autopilot in the browser version  on: 02/27/19 at 10:49:04 Started by Tony | Post by Tony This code changes Io's color when it goes into Jupiter's shadow. Sun = 1, Jupiter = 6, Io = 12 When Io is more than 9.7 degrees from Jupiter's center, it plots bright color, otherwise it plots dark color. Code:if (elongation(6,1,12) > 9.7) { objColorRed[12] = 255; objColorGreen[12] = 100; objColorBlue[12] = 255; } else { objColorRed[12] = 20; objColorGreen[12] = 0; objColorBlue[12] = 20; }

 8 General / Discussion / Re: Moon orbit - max distance  on: 10/28/18 at 11:21:35 Started by wil | Post by frankuitaalst The sim above gives us additional info about the stability of the Earth - Moon system in what concerns the Hill sphere .   I gathered the output of the above sim ( Sma and eccentricity of all of the 100 minor bodies ) in a data file and represented the data  in a chart .   The chart represents :     X-axis : the Sma of each body ( 0 to 0.01 AU = 0 to 1.500.000 km )   Y-axis : the eccentricity of each body ( 0 to 1 ) .     The sim was ran untill no more  bodies escaped . This period covers 196 frames in the animation.     One can (briefly ) see the sim starts with all bodies lined up at Ecc=0 and Sma = 1/300 AU and 1/200 AU ) = (1/3 and 1/2 Hill) .     The eccentricies soon rise , also some Sma get bigger .   After some time some bodies escape at Ecc around 0.8-0.6) while puping up their Sma , and escape to the right of the chart , escaping Earth's gravity field.   This happens several times .     After some time the system seems to "stabilize" , resulting in  dynamical behaviour , but without escaping bodies .   At the end it seems bodies even at 1/2 Hill ( = 0.005 Sma) , but at appropriate eccentricities , do not have the "intention " to escape .

 9 General / Discussion / Re: Moon orbit - max distance  on: 10/28/18 at 05:32:37 Started by wil | Post by frankuitaalst I've made a little sim :   in the sun -earth system : created 100 massless bodies , between 500.000 and 750.000 km , thus between 1/3 and 1/2 Hill . I gave them 0 eccentricity . See Sim in annex.     It is worthwile to see :   * eccentricity of all the bodies rises ,   * some bodies (about 10% ) escape the system . It is interesting to notice the escape goes over the L1 OR the L2 point  ( the line L2 L1 is directed towards the sun . So 1/2 Hill is partially stable .   * and further :  when we zoom out in the sim one can observe the escaped bodies will occupy the L4 and L5 clouds .

 10 General / Discussion / Re: Moon orbit - max distance  on: 10/18/18 at 16:14:01 Started by wil | Post by wil Ok. Thus what is the real maximum distance in the case of the Moon, or in general: in any three-body scenario?   Hill by 2, 3, maybe e?