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Editor's Notes

• #6: Video-conferencing avoids travel costs and carbon footprint
• #17: Model by Hiro Sheridan. Bond angles and lengths are realistic
• #18: Text from the exhibit:Newtonian gravity is an elegant theory that describes the force of gravity between two objects as: F = G * M1 * M2 / d^2 where G is the unviersal gravitational constant, M1 and M2 are the masses of the two objects, and d is the distance between the two objects. The direction of the force is towards the other object. This, together with Newtons Second Law of Motion, F = m * a where F is the force on an object, m is the mass of the object, and a is the acceleration of the object, give us everything we need in order to figure out how stars will orbit around each other as a result of the influence of gravity.When there are only two bodies (be they stars, or a star and a planet, or a planet and a moon, or a planet and an orbiting spacecraft), there exists an analytic solution to Newton's gravity for the orbit. That is, we can derive equations that will tell you where the objects will be, and how fast they will be moving, at any time in the past or future, just by plugging the time into the equations. However, for three or more bodies, there exists no closed-form analytic solution. As a result, the only way to figure out how the objects orbit around each other is to do a "numerical" solution.A numerical solution to a Newtonian gravitational problem works by figuring out where all the objects are, figuring out the forces on each object as a result of all the other objects, figuring out the acceleration as a result of that force. The velocity of the object is then updated as a result of the acceleration, and the objects are moved by their velocities, for a small "time step". Then the process is repeated. Do this over and over again, and you simulate how the objects will move through space as a result of their mutual gravitational interaction.The general problem is called the "n-body problem", where n indicate it's a number of objects interacting. The simplest case is n=3; that is the problem that the "3-body simulator" object is solving. See the associated instructions notecard for information about controlling the simulation.- Rob Knop (aka Prospero Frobozz) 2009/09/03Operating instructions:The 3-Body Simulator was written for LSL by Rob Knop -- Prospero Frobozz in Second Life. rknop@pobox.comThis is an collection of objects that numericaly solve the 3-body problem using LSL. It displays the results of this simulation in real time by moving around three stars. For more information about the 3-body problem, read the associated notecard, "The Newtonian 3-Body Problem".By default, the simulator keeps track of time in years (the number of years since the start of the simulation is shown in floating text over the computer object). 0.1m in Second Life corresponds to 1 AU as the stars move around. The units for position and velocity for the stars are AU and AU/year respectively. The unit for mass is Solar Masses.Next to the display in StellaNova is a box that will give you a personal copy of this 3-body simulator when you click on it.The simulator is composed of the "computer" (the grid-textured box), the star tank (the big, mostly transparent box), the three stars, and the control panels to the left of the star tank.The buttons in the upper-left corner of control the overall simulation. Right now, click "Reset". (You may need to click it more than once to get all the stars to the right place.) That should move all of the stars to their initial positions inside the tank. The other buttons on this panel : * Start : starts the simulation running * Stop : stops the simulation * Reset : reset the simulation to initial conditions * Dump Values : say in local chat the current position and velocity for the stars * Center Positions : Use this only when the sim isn't running. It will center all of the stars' initial positions around the center of the tank. * Center Momentum : Use this only when the sim isn't running. It will adjust the stars' initial velocities so that the whole system has 0 momentum (and thus won't drift out of the bounds of the simulation too fast). * >> Copy >> Init. Values : Use this after clicking one of the previous two buttons. It will copy the initial conditions to the Star Control Panel. Note that it takes a few seconds for the Star Control Panel to fully update after you click this button. (It can take longer if there is bad simlag.)To the right of these buttons is a larger control panel, with three subpanels labelled "Star 1", "Star 2", and "Star 3". These panels let you set the **initial conditions** for the stars. It does NOT control or display the *current* positions or velocities for the stars when the simulation is running. You can use this to set up the simulation to be what you want.To use it, adjust the stars' masses, positions, and velocities. Around each value are little "+", "++", "-", and "--" buttons that allow you to increase and decrease the displayed vaules. When you like the values you have set, click the "Update" button for that star. Repeat this for the other two stars.===> NOTE : if you do not click the "Update" button, the star values will not be sent to the simulation computer! This is true even though the stars themselves may have changed position or appearance.When you like your intial conditions, and have cliced "Update" for all of them, click "Reset" in the 3-body simulator controls, and then "Start" to start a simulation.OTHERCOMMANDSThe stars optionally may display a velocity vector that shows their current speed and direction of motion. Turn these on by typing each of the following into text chat: /1 SHOWVEL /2 SHOWVEL /3 SHOWVEL to hide the velocity vectors, type: /1 HIDEVEL /2 HIDEVEL /3 HIDEVEL If you do *not* want the star computer reporting the total energy in the system every so often when the simulation is running, type /16384 noreportenergyto turn energy reporting back on, type /16384 reportenergy You can change the timestep used for the simulation before starting the simulation with the command /16384 dt 0.001 0.001 years is the default timestep; replace 0.001 with another value.
• #19: Text from the exhibit:This is MICA's Data VisualzationLabThe visualization you see in there now is a 6-dimensional data set on stars, galaxies, and quasars in a parameter space of colors, redshifts, and morphology. The measurements are from a small subset of the Sloan Digital Sky Survey. The 3 spatial axes (XYZ) encode the colors; the size of the data points encodes their apparent brightness (magnitude); stars are gray, whereas quasars have the colors which encode theorredshift (~ distance); and galaxies have a color which encodes their stellar populations, roughly; stars and quasars are represented as spheres, and galaxies as cubes.We think that we can encode ~ 12 - 15 parameter space dimensions in further extensions of this methodology.This data rezzer script was written by Desdemona Enfield, in collaboration with Curious George.
• #20: Genetics sim associated with Dr. Mary Anne Clark (Max Chatnoir in SL) at Texas Wesleyan University. http://web.txwes.edu/biology/macclark/
• #24: Expressive poets