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- Dance of the Planets(TM)
- Demonstration v1.30
- December 5, 1989
-
-
- WHAT IS DANCE OF THE PLANETS?
-
- DANCE is a computer model of the solar system. It is a realistic
- model with correct scaling, image details and lighting effects. It is
- a working model, combining orbital simulation with accurate time-
- location calculations. It is a three-dimensional model in which scenes
- can be viewed from any angle, and bodies interact gravitationally in
- three-dimensional space. It is a complete model with virtually all the
- known bodies of the solar system which, in addition to the Sun and
- nine major planets, includes 60 satellites, over 4100 asteroids, and
- some 1400 recorded comet appearances. The model is also an observation
- tool, providing views of all the orbiting bodies against the starry
- sky as seen from Earth, complete with location coordinates for any
- time. The intent is to represent the solar system in a deep and de-
- tailed manner that does some justice to the richness and complexity of
- the real thing. To make it very accessible through the power of the
- computer.
-
-
- WHY ORBITAL SIMULATION IS IMPORTANT
-
- Behind the images, the never-ending task of the program is to simu-
- late (mimic) gravity by constantly calculating the gravitational
- effects that each body has on the other, and allowing them to move
- through space accordingly. This "working" model can therefore antici-
- pate and reproduce motions, positional relationships, precessions, and
- many strong perturbation events that have or really will occur "out
- there". It doesn't know where a chaotic comet will be 50 years from
- now in the sense that it can calculate it. But by simulating gravity
- with greatly accelerated time, you can just let it happen and see
- where the comet will be. Equally well, you can run time backward and
- see where an object was in the past, and what influences caused it to
- be where it is today. Orbital simulation provides something of a time
- machine, and can vividly illustrate orbital phenomena.
-
-
- WHAT DOES DANCE DEMO DO?
-
- The demo presents a selection of simulation scenes chosen to illus-
- trate the range and nature of DANCE. Within limits, you can operate
- the demo just as you would the complete program. Between the examples,
- you will find some explanatory text to amplify what you are seeing.
-
-
- RUNNING THE DEMO
-
- * Place the disk in your drive and select that drive (for example,
- enter a: to the DOS prompt).
-
- * Enter DANCE to load and run the program.
-
- * After the title screen, press PAGE DOWN to begin the demo (a demo
- script is ready to go).
-
- Now go through the demo at your own pace using the PAGE keys. HOME
- shows the script contents. Change viewpoint and magnification if you
- wish, or any other side excursion. Note:
-
- * The apparent simulation SPEED is dependent upon the PC on which it
- is run. Change the SPEED settings to suit your system. Perhaps slow it
- if you have the coprocessor, or speed it up if you don't. There will
- be further notes in the demo in regard to speed.
-
- * The scenes have captions which may be erased by view changes you
- make. You can restore the caption by pressing ENTER when the simula-
- tion is running (PAUSED.. doesn't appear after the date), or just
- continue the demo by pressing PAGE DOWN.
-
-
- READ THE FOLLOWING FOR BASIC DEMO CONTROL & OPERATIONS
-
-
- ESSENTIALS THAT YOU NEED TO KNOW.
-
- You don't need to do much to run and enjoy the demo, but you will
- get more out of it if you interact with it. DANCE also assumes, but
- does not require, some practical knowledge about the subject matter
- (coordinate systems, orbital phenomena, etc.). The complete manual
- explains the basic terms and concepts.
-
- Here are some basic demo operating considerations that you need to
- keep in mind.
-
-
- SPEED
- The speed you perceive is dependent upon how fast your PC can
- "crunch" numbers. If you have a fast PC with a coprocessor, some of
- the demo simulations may need to be slowed down. If they are too slow,
- increase the speed. But keep in mind that simulation accuracy suffers
- at high speed settings because fewer calculations are being performed
- to approximate the continuous effects of gravity. What is too fast
- depends upon the particular objects being simulated.
-
- A coprocessor is always recommended for calculation intensive soft-
- ware like DANCE. Fast (20mhz or better) 286 and 386 PC's perform okay
- without, but better with. Coprocessors can speed performance by 5X-
- 10X. ARC can supply coprocessors made by IIT which are significantly
- faster than Intel's, and similarly priced. A coprocessor is a good
- hardware investment.
-
- GOING BACK IN TIME
- Although the demo doesn't allow you to change the date, you do have
- some control over time:
- * To start a simulation over again, press DATE (press the 'D' key) to
- get the initial date, and press ENTER. You may want to refresh the
- screen by also pressing ERASE.
- * You can always run the simulation (time) backwards by setting the
- SPEED to a negative value.
-
-
- CHANGING THE VIEW
- In addition to speed, you are encouraged to vary your perspective by
- changing magnification (ZOOM), latitude, and longitude (ROTATE). If
- you do this from the control bar (the hot key selections along the
- screen bottom), the screen will be updated every time you make a
- change with the cursor keys. This may be what you want, but it will be
- slow on some PC's. The view can be changed directly to what you want
- without intermediate screens by using the popup MENU.
-
-
- FAST CHANGES FROM THE MENU
- Press MENU to pop it up, and then hold the HOT KEY to select the
- parameter. It's value will be highlighted at the bottom of the screen.
- Change this with the cursor keys. Press ENTER to accept the change,
- and then select another menu parameter, or press ENTER a second time
- to erase the menu and resume simulation.
-
- Note: any time a parameter value is high-lighted at the bottom of the
- screen, simulation is suspended and PAUSED.. appears to the right of
- the calendar.
-
-
- RESTORE THE DEMO CAPTION
- Making screen changes will erase the demo script remarks in the
- light-blue box. You can restore this by pressing ENTER when the
- simulator is running (not paused for other changes). Alternately, just
- pressing PgUp or PgDn will go on to the last or next demo simulation.
-
-
- MODES
- Program viewing and operation will be in respect to one of the
- following three modes:
-
- SPACE MODE, in which the solar system is viewed from afar, from any
- angle (the default mode).
-
- PLANET MODE, which is still viewing from afar but as if with a
- powerful telescope locked onto the planet of interest (TRACK pro-
- vides a cursor that is moved over the planet. Lock on with ENTER).
- The name of the tracked planet will appear at the bottom of the
- screen in the control bar.
-
- Note: When in PLANET MODE only the planet and its satellites are
- active. Even if, at low power, other solar system objects are
- visible, they will not orbit, nor will they be IDENTIFIED.
-
- EARTH MODE, in which objects orbiting in the simulator are seen
- from an Earth-centered perspective. (EARTH VIEW is an on/off toggle
- on the popup MENU).
-
-
- USING IDENTIFY
- IDENTIFY on the popup MENU is used to label objects on the screen.
- This pauses the simulator, and then any key press will erase the
- labels and resume simulation. When in PLANET MODE, only satellites are
- labeled, even though at low power (ZOOM) other objects may be seen.
-
-
- USING ACCESS
- ACCESS in SPACE or EARTH MODE will display planet coordinates/para-
- meters and a second (ACCESS) menu. OBJECT STATUS can be chosen from
- this menu to show orbital parameters and coordinates for any asteroid/
- comet active in the simulator. Both planets and asteroids/comets can
- be made temporarily inactive in the simulator to improve speed. This
- is done for planets with the ACTIVE PLANET selection on the ACCESS
- MENU, and other objects can be toggled on/off on the OBJECT STATUS
- screen. In either case, when the object is inactive, the first charac-
- ter in its line will be 0.
-
- ACCESS in PLANET MODE shows a table of satellite information. The
- different planet systems can be compared by pressing the PLANET NUMBER
- as indicated at the bottom of the screen. Although the demo is limited
- to Saturn for close views, in the full program you can go directly to
- the planet by then pressing 0 (GOTO).
-
-
- VIEWING ORBITS IN 3D
- Orbits are drawn in stereo pairs when 3 D Orbits is toggled on on
- the popup MENU (toggle 3 once again to restore normal viewing). 3-D is
- useful for understanding relative orbit orientations which can be a
- very important factor in perturbations and orbital stability. Simula-
- tion is paused when in 3-D. (Note: plastic framed color filter glasses
- are included with the full program.)
-
- Not everyone can see the 3-D effect because of vision asymmetries.
- But most can with a little practice. Try to see the same background
- color with each eye. You can control the degree of stereo separation
- with the VIEW (apparent distance in cm) selection on the control bar.
-
-
- USE HELP
- Selecting HELP will provide a quick reference guide to DANCE control
- bar and menu selections.
-
- The remaining documentation is excerpted from the DANCE manual. The
- contents provide an overview of the scope of v1.30.
-
-
-
- TABLE OF CONTENTS FROM THE COMPLETE DANCE v1.30 MANUAL
-
-
- PART 1: USING THE PROGRAM
-
- INTRODUCTION
- About DANCE OF THE PLANETS........................................1-1
- About This Book...................................................1-2
- About Disks and Installation......................................1-2
- Dance in Your PC..................................................1-3
-
- FIRST LIGHT
- The Dance Screen and Control Bar..................................1-4
- The Control Bar Selections........................................1-4
- Getting to Know the Dance Environment.............................1-5
- The Main Menu.....................................................1-7
-
-
- A DANCE TOUR OF THE SOLAR SYSTEM
-
- STAR NAVIGATION
- The Starry Sphere.................................................1-8
- About Coordinates.................................................1-9
- Orientation to the Vernal Equinox................................1-10
- The Celestial Sphere Overlay.....................................1-10
- Viewing From Earth...............................................1-10
- Observing the Polar Sky..........................................1-11
-
- VISITING PLANETS
- Basics for Planet Viewing........................................1-12
- A Voyager View of Saturn.........................................1-12
- Light, Color, and Your Monitor...................................1-13
- Viewing from Earth...............................................1-13
-
- OBSERVING ASTEROIDS AND COMETS
- Plotting Asteroids...............................................1-14
- Resume Files.....................................................1-15
- Asteroids from a Resume File.....................................1-15
- Orbit Initialization and Epoch Currency.....................1-16,1-17
- Asteroids from the Earth.........................................1-17
- Inactivating Objects in the Simulator............................1-18
- Deleting Objects from the Simulator..............................1-18
- Getting Asteroids from the Main Files............................1-18
- Four Instructive Comets..........................................1-19
- Viewing Orbits in 3-D............................................1-20
- Getting a Better View of Comet Halley............................1-21
- Comet Kojima In Commotion: a strong perturbation.................1-22
- Reality and Accuracy of Orbital Simulations.................1-23,1-24
- A Sense of Scale and Time........................................1-24
-
-
- ACCESS: THE OTHER SIDE OF DANCE
-
- ACCESS FOR INFORMATION AND CONTROL
- Access from the Solar System.....................................1-25
- The Access Menu..................................................1-26
- Access to Orbit Information......................................1-27
- Orbital Elements and Simulator Orbits............................1-27
- Object Coordinates...............................................1-28
- Access to Planet Systems.........................................1-28
- Fast Access to the Other Planets.................................1-29
- Saving a Planet Resume File......................................1-29
-
- HARDWARE ISSUES
- CPU Performance..................................................1-29
- Help for Slow Simulations........................................1-30
- Printing the Access Information Screens..........................1-30
- Dumping the Graphic Screen.......................................1-30
-
-
- PART 2: THE SOLAR SYSTEM
-
- FORMATION, CELESTIAL MECHANICS, AND THE INNER PLANETS
-
- FORMATION AND THE CHARACTER OF THE SOLAR SYSTEM
- Introduction.....................................................2-1
- The Formation of the Solar System................................2-2
- The Solar System Today...........................................2-3
- Some Apparent Difficulties.......................................2-4
-
- UNDERSTANDING THE MOTION OF THE PLANETS
- Pioneers and Kepler's Laws.......................................2-5
- Newtonian Mechanics..............................................2-6
- Newtonian Gravity................................................2-6
-
- AN ORBITAL PRIMER
- Introduction.....................................................2-7
- Geometry and Dynamics of Elliptical Orbits...................2-7,2-8
- Orbital Energy and Velocity......................................2-8
- Illustrating Principals with Examples............................2-9
- The Orbital Elements............................................2-10
- Simulating Gravity in a computer......................2-11,2-12,2-13
-
- ORBITAL STABILITY
- Precessing Nodes................................................2-13
- The Stability of the Solar System...............................2-14
- Orbital Chaos...................................................2-14
-
-
- THE INNER SOLAR SYSTEM
-
- INTRODUCTION
- Image Simulation in DANCE.......................................2-17
- Thinking Metric.................................................2-17
- The Inner Planets...............................................2-18
- The Sun.........................................................2-18
-
- MERCURY AND VENUS
- Introduction....................................................2-19
- Good Apparitions and a Great Morning Rendezvous............2-19,2-20
- Christmas Stars.................................................2-20
- Viewing the Inner Planets at High Power.........................2-21
-
- THE EARTH-MOON SYSTEM
- Introduction....................................................2-23
- Mars Epicycles..................................................2-24
- Martian Satellites..............................................2-24
- Fear of Phobos Falling..........................................2-24
- Are They Asteroids?.............................................2-25
-
-
- PART 3: THE JOVIAN PLANETS
-
- Introduction.....................................................3-1
-
- SATELLITES OF JOVIAN PLANETS
- Introduction.....................................................3-1
- Instability and Roche Limits.....................................3-2
- Formation and Proto-Satellite Swarms.............................3-2
- Tidal Forces.....................................................3-3
-
- THE JUPITER SYSTEM
- Introduction.....................................................3-4
- Jupiter at Full Power............................................3-5
- Jupiter's Rings..................................................3-5
- The Satellites of Jupiter........................................3-6
- The Galilean Moons...............................................3-6
- Comparing Satellite Systems......................................3-7
- The Wild Outer Satellites........................................3-7
- Computer Escape Velocity?........................................3-8
- Are They Captured Asteroids?.....................................3-8
-
- THE SATURN SYSTEM
- Introduction.....................................................3-9
- The Planet Saturn...............................................3-10
- The Rings of Saturn.............................................3-10
- The Satellite of Saturn.........................................3-11
- Resonances and Co-Orbital Satellites............................3-11
- Saturn's Irregular Satellites...................................3-12
-
- THE URANUS SYSTEM
- Introduction....................................................3-13
- Comparing Jovian Systems........................................3-13
- The Planet Uranus...............................................3-14
- The Rings of Uranus.............................................3-14
- The Satellites of Uranus........................................3-14
- Conjecturing on the Tilt........................................3-14
- The Satellite System Edge-On....................................3-15
-
- THE NEPTUNE SYSTEM
- Introduction....................................................3-15
- The Planet Neptune..............................................3-16
- Exotic Orientations in 3-D......................................3-16
- Comparing Satellites............................................3-16
- Triton..........................................................3-16
- Nereid..........................................................3-17
- Six `New' Satellites............................................3-17
- Arcs and Rings..................................................3-18
- Speculation about the Neptune Satellite System..................3-18
-
- PLUTO AND CHARON
- Introduction....................................................3-18
- Viewing Pluto-Charon............................................3-19
- A Fortuitous Time...............................................3-19
- The Character of Pluto..........................................3-20
- Positional Accuracy of Pluto-Charon.............................3-20
-
-
- PART 4: ASTEROIDS AND COMETS
-
- ASTEROIDS
-
- Introduction.....................................................4-1
- Early History, Briefly...........................................4-2
- Origin and Nature of Asteroids...................................4-2
- Nature and Classification........................................4-3
- A Perspective on Asteroids.......................................4-4
-
- ORBITAL CHARACTERISTICS OF ASTEROIDS
- Introduction.....................................................4-5
- Identifying Asteroids in a Plot..................................4-6
- Kirkwood Gaps................................................4-6,4-7
-
- ORBITAL CLASSIFICATIONS
- Inner Asteroids..............................................4-7,4-8
- Distant Asteroids................................................4-9
- Asteroid Families...........................................4-9,4-10
-
- OBSERVING ASTEROIDS
- Introduction....................................................4-10
- Magnitudes......................................................4-11
- Using DANCE to Find Favorable Oppositions.......................4-11
- Identifying an Asteroid in the Sky..............................4-11
- Identifying and/or Avoiding an Unexpected Asteroid..............4-12
- Further Exploring in the Data Files........................4-12,4-13
-
-
- COMETS
-
- Introduction....................................................4-14
- Short-Period and Long-Period Comets.............................4-14
- The Origin and Nature of Comets.................................4-14
- Formation of the Oort Cloud.....................................4-15
- Star Drops......................................................4-16
- Telling Asteroids and Comets Apart..............................4-16
-
- COMETS IN DANCE
- Introduction....................................................4-17
- Comet Simulations...............................................4-17
- Parabolic Comets and an Historical What-If.................4-18,4-19
- Oterma: The Case of a Lost Comet................................4-20
- Checking Simulator Accuracy.....................................4-21
- Oterma and the Hilda Asteroids..................................4-22
- A Comet Capture by Jupiter......................................4-22
- Observing Close Encounters from Earth...........................4-23
- Periodic Comets of Only One Appearance..........................4-24
- More Strong Perturbations.......................................4-24
-
- WRITING YOUR OWN SUBJECT FILES...................................4-25
- A 10,000 year Simulation........................................4-26
-
-
- BIBLIOGRAPHY
- GLOSSARY
- INDEX