![]() ![]() ![]() “There’s no special distance at which gravity starts working,” says Nick Moeckel, a theorist at the United Kingdom’s University of Cambridge, who recently modeled the paths of planets orbiting binary stars. “There’s a dramatic change between going along in free space, and suddenly, bam – you’re sucked in,” Parker describes. Before that, the bird travels in a straight line, transitioning to a curved orbit inside the gravity sphere. Only within a planet’s sphere of influence is a bird subject to the field’s strength. When a bird approaches or circles an object, “they determine that force based on proximity to these planets.” “They’re adjusting that force probably 30 times a second,” he says. Though the original Angry Birds was set with a constant gravitational force acting over a flat surface, Catto says that simulating isolated, circular fields using Box2d would be easy. Every fraction of a second, the program simulates a world of these bodies, calculating how all the forces in play (things like friction, collisions and gravity) interact to influence the bodies’ motion. “Otherwise, gravity would be too weak at the edges of the field,” says Erin Catto, the game physics programmer who created Box2d, the physics engine that runs behind the curtain at Angry Birds.īox2d simulates the interactions of rigid bodies - birds, pigs, crates, balloons - with defined velocities, masses, and densities. That seems to be a casualty of making the game fun. For starters, the gravitational fields appear to have a uniform magnitude instead of weakening with distance from an object’s center (called the inverse square rule). “There’s also no such thing as an exploding bird,” Parker notes.īut some of the more realistic characteristics of the game don’t quite obey Newton’s laws. Then again, snorting pigs and a bird that sounds like a Wookie - the big green one - wouldn’t make a sound in space. Though the game is charming - and quite fun - Parker and some other folks who know a thing or two about physics suggest that its details belie a rather non-Newtonian universe. “At NASA, we spend a lot of time thinking about just where to pull back that slingshot, which precise angle to use, and what speed to give a spacecraft.” He likes the game because it combines addictive fun with what he does for work. ![]() “It’s a very intuitive, dynamical system they’ve set up,” says Jeffrey Parker, a mission designer and navigator at the Jet Propulsion Laboratory in Pasadena, Calif., who is currently working on the GRAIL mission. Once the bird is within the circle, its path changes, and the bird appears to be tossed around by both gravity and some kind of atmospheric drag. And, the game’s designers have inscribed a circle around each object with a gravitational field. The extra dimensions make this version a bit trickier than the original, but Angry Birds Space helps by projecting a flung bird’s path - at least, for a short distance. Instead of tracing parabolas en route to pig fortresses, the curmudgeonly birds - including a few newbies - trace arcing paths around these planet-like bodies.Īcted upon by circular gravitational forces, properly aimed birds can sometimes loop around several spheres in a dizzying figure-eight pattern before laying siege to encamped pigs, which are sometimes sitting upside-down on the bottom of a planet. The new game is set in microgravity, and the astro-birds and space-pigs are negotiating a Birdiverse filled with cratered spheres, sinister-looking gears, and objects vaguely resembling icy moons. The most recent spinoff, Angry Birds Space, was, ahem, launched with an announcement from the International Space Station in March, and within three days more than 10 million people had downloaded the game.) (If that sentence seems like a preposterous assembly of words, an explanation: That is the premise of Angry Birds, a game for smartphones and tablets first released in 2009 that quickly became popular worldwide. In their newest incarnation, the Angry Birds fly through space in search of green pigs who absconded with the birds’ eggs. The Angry Birds have arrived … IN SPACE, still aimed toward exacting revenge on a cadre of bright green pigs who’ve waddled off with the birds’ eggs. ![]()
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