Dance of the Planets. (educational software) (evaluation)
by Gregg Keizer

Of the billions who have walked this world and seen its skies, none have failed to look up in wonder. The music of the spheres, man once though, was the sound made by perfect crystal. We may know now that the only sound in the solar system is a background hiss of long-gone radiation and radio white noise, but we nonetheless continue to put music to the turning of the plantes.

It's no surprise then that astronomy captures our imagination. On a dark night anyone with eyes can play stargazer, moon watcher, and planet tracker. Anything that gives us a better window on the universe is welcome, whether that means planetariums, telescopes, or recently, personal computers. Good astronomy software for the PC leaves behind the small band of professional astronomers to capture the attention of nearly everyone who's looked at the lights and wisked to realy be there.

And no other PC program gives you a better sense of the utterly graceful chaos of our solar system than Dance of the Planets. Where other stargazing software puts static pin-points of light on the screen to represent galaxies and worlds, Dance of the Planets puts realistic, spinning spheres shepherded by coveys of moons that wax and wane. Dance of the Planet is an extraordinary program that should be a fixture of every science classroom and on the hard disk of home computers wherever there are people fascinated with the night skies.

Unlike most astronomy software for the PC, Dance of the Planets concentrates on the hometown--the solar system's nine planets, 60-odd moons, 4600+asteroids, and 1300 or so comets. You'll see plenty of stars in Dance of the Planets, but they're really just a backdrop to the real play on the local stage.

Once installed on the more than 1.1 megabytes it demands from your hard drive, Dance of the Planets almost immediately turns you into a planetary tourist. On a VGA-equipped, 386SX or 386 PC with at least 640K of memory, the program is stunning. Anything slower--a 286 system or less well-equipped system, a floppy-only computer perhaps--is barely workable. And if you have the good luck, or money, to have a math coprocessor inside your machine, you'll think you've got a tunnel to the sky on your desktop.

Dance of the Planets uses a control bar to command the movement of worlds. Discreetly tucked away at the bottom of the screen, the bar takes instructions via either mouse or keyboard. The former is more convenient, the latter more reliable. Click on a control bar segment, and you can enter viewing coordinates or dates, select viewing magnification and simulation speed, or label the visible bodies. A pop-up menu leads you to additional choices that pick and lock in on planets, plot asteroids, and draw constellations, while another command accesses a database packed with information about planets, moons, asteroids, and comets. Operating Dance of the Planets is relatively easy, though not necessarily simple: There are too many permutations and possibilities for simplicity here.

The program's documentation helps immensely. It's not the most attractive manual, but it's eminently readable and reasonably clear even to those who skipped too many science classes. Best of all, it shows you exactly how to take a virtual field trip to the sun, the moon, the asteroid belt, and every planet. If you can follow directions, you'll be quickly soaring out to Jupiter, peering at Mars, and watching Mercury transit the sun.

Dance of the Planets' most significant problem is its rapacious appetite for computational power. Running on something as substantial as a 20-MHz 386SX PC (minus a math coprocessor), Dance of the Planets often makes you wait a long, long time while a screen redraws. Magnified views of the most detailed planets--Earth, Mars, and Jupiter--are particularly slow in reappearing. This program pushes a home computer's calculating ability to the limit, and beyond. If you're serious about astronomy, plan to use Dance of the Planets in a classroom, or find yourself spending hours in front of this program, your best investments are a math coprocessor and a fast, RAM-packed video card.

You can probably pick out a few planets with the naked eye--Venus, Mars, Jupiter, maybe even Saturn on a good night--but unless you have a telescope, your're only seeing bright lights. You can't find the outer planets, nor can you watch the satelites pirouette around their masters. Dance of the Planets gives you a front-row seat to this planetary ballet.

By combining impressive graphics with an accurate orbital simulation that accounts for the dynamics of gravity and precise placement of celestial objects, Dance of the Planets effectively squeezes the solar system into your PC. You can take a seat on Earth and view the system from there, or you can spy on the entire solar system or any of its parts from a starship 270 astronomical units (about 25.1 billion miles) from the sun. Depending on your vantage point, you can dial up magnifications as high as 32,000 times normal. With that much viewing power, you can see details as small as the Hawaiian Islands on Earth, watch the seasons change on Mars, and track the Great Red Spot on Jupiter.

And you can follow the dance of the moons in Dance of the Planets. At extreme magnifications, you can even see Charon, Pluton's companion. Pull back, and you can watch the entire Jovian system, all 16 moons, weave their complex orbits. Zoom in on Saturn and follow the shepherd moons as they interact with the planet's icy rings. Dance of the Planets lets you select not only the magnification of your super telescope but its perspective as well. You can zip far above or below the ecliptic plane (the plane of Earth's orbit, used as a dimensional reference) to see the entire solar system or any of its planets from entirely new angles.

This program has other amazing strengths. It can plot nearly all the known asteroids and comets to show you the depth of the asteroid belt between Mars and Jupiter, and to recreate a comet's path as it plunges toward the sun. You'll learn just by looking, a revelation to anyone who struggled with boring textbooks and their flat charts and illustrations. Did you know that some asteroids congregate near Jupiter's orbit while others are far from the belt, even within Earth's orbit? Ever wonder how near comets come to the Earth? Dance of the Planets lets you re-create close encounters of the past and preview future close calls, too.

When you watch from Earth, you can set your seat with longitude and latide and pick any date from 4680 B.C. to A.D. 10000. Conjecture says that a conjunction of Jupiter and Venus on June 17, 2B.C., may have been the Christmas star. Check it out for yourself. Or view famous solar eclipses of history or get a jump on those in the future, without leaving the comfort of home.

Dance of the Planets offers up a slew of extras that make your imaginary voyaging even more enjoyable. A 3-D option puts orbits in stereo on the screen when you put on the included glasses. You can selectively turn bodies on or off to focus your attention and speed up the display. You can spread deep space objects--distant galaxies, pulsars, guasars, globular clusters, and the like--across the sky to add to the more than 9000 stars. And you can save simulations to disk for later replay. You can even send screens to 9- or 24-pin printers or to a LaserJet II-compatible laser printer.

You'll be awend by this onscreen orrery. As it mimics the solar system, Dance of the Planets brings to life places most of us will never see, even through a telescope. In the classroom, Dance of the Planets not only illustrates the motion and interaction of the system's bodies--something the best textbooks find impossible--but it lets kids visualize everything from Newton's law of gravitation to some aspects of the more modern chaos theory. At home, the program can be used strictly for entertainment--touring the outer planets, replaying Voyager flybys, tracking famous comets--or for more strenuous at-home celestial education.

Though Dance of the Planets costs more than twice as much as other PC astronomical software, it's a much better value. You'll get more out of an hour or two with Dance of the Planets than you'd get in weeks of staring at the static dots those other programs put on the screen. More important, though, is how Dance of the Planets helps you make some sense of the night sky. Your appreciation of stellar bodies grows each time you run this simulation.

Play with Dance of the Planets; then walk outside and look up. The spread of lights seems somehow changed. Now you know what goes on around the brightest pinpoints and in the dark and invisible corners of the solar system. What a perfect ticket to the greatest show on Earth--or any other planet.