The Physics of Imaginary Things

By Sean Carroll | December 26, 2006 1:10 pm

Quadruple digits! Yes, this is our 1000th post here at Cosmic Variance. In honor of which we will — well, nothing special. But I will indulge in some shameless pluggery.

Physics of the Buffyverse Today, you see, is the official publication date of The Physics of the Buffyverse, by the blogosphere’s own Jennifer Ouellette. I’m not going to offer a proper review of the book, because (1) I’ve only had a chance to skim it thus far, and (2) the author bakes me scones, which is a conflict of interest if ever I’ve seen one. But you could do a lot worse than buying a few copies for yourself and all your friends, let me assure you.

The construction of the title — The [field of academic inquiry] of [product of human imagination] — is by now well-known, inspired in large part by Lawrence Krauss’s The Physics of Star Trek. (In addition to the Physics, we’ve learned about the Ethics, the Art, the Computers, the Religions, and the Metaphysics of Star Trek, as well as corresponding studies of Star Wars, Harry Potter, and so on.) And as long as it’s been in circulation, the idea of subjecting TV shows or fantasy genres to scientific investigation has been the target of scoffing from curmudgeonly old folks who are taking a temporary break from chasing kids out of their yards. After all, they will tell you, how can you learn anything about science by studying fiction? Science is all about the real world! It has nothing to say about fake worlds that someone just made up.

Balderdash, of course. Neither physics, nor any other science, is some list of facts and theories to be committed to memory. There are a bunch of established pieces of knowledge that are worth remembering, no doubt about that, but much more important is the process by which that knowledge is acquired. And that process is just as applicable to imaginary worlds as it is to the real one. Any respectable universe, whether we find it out there or make it up ourselves, will be subject to certain internal rules of behavior. (When it comes to fiction, those rules are occasionally sacrificed for the sake of the plot, whereas in the real world they’re a bit more immutable.) Learning how to discover those rules, from the standpoint of an observer rather than one of the creators, is nothing more or less than learning how science is done.

I’ve long thought that video games would be a great way to teach the scientific method to kids. They’re playing them anyway — why not think of it as collecting data? The other day Seed’s Daily Zeitgeist linked to this gravity game.

Gravity Game

Your job is to give initial conditions (position and velocity) to a little test body, which then moves around under the gravitational field of various heavier bodies, with the goal being to survive for as long as possible without colliding with one of the planets. But the “laws of gravity” certainly aren’t the ones that Newton came up with, as a bit of experimentation shows; for one thing, orbits around just one planet don’t describe conic sections, they decay in spirals. So what are the laws? Does the strength of gravity obey something other than the familiar inverse-square law? Or is there dissipation? Are energy and angular momentum conserved? Even better, is there some definition of “energy” and “angular momentum” such that they are conserved? What about those boundary conditions at the edges of the box? They are in some sense reflective, but the magnitude of momentum certainly isn’t conserved — what’s the rule? We know in this case that there certainly are hard-and-fast rules, as the programmers put them into the code. I would love to see kids in science classes using a game like this as a miniature “laboratory,” in which they designed experiments to test different hypotheses they came up with.

Somewhat more complex is N, the ninja game from metanet.

Ninja game

Here the physics is substantially richer. You are a tiny ninja, whose job is to jump around and avoid threats while doing what it takes to open a door and escape within a specified time limit. But, being a ninja, you have unusual powers — including the ability to alter your center-of-mass momentum in midair by sheer force of will. So: is the trajectory of the ninja uniquely defined by its initial data? Are there any conserved quantities? Are the laws of motion isotropic — are the rules governing left-right motion the same as those governing up-down motion? Can the ability to stick to walls be described in terms of a coefficient of friction? You can be killed by smashing into a wall or floor too quickly — but the allowed velocity depends on the angle of impact. So what quantity is to be calculated to determine whether a landing is safe or not?

You get the point. Those of us who have become enchanted by science see the world as a giant puzzle, and our “job” is to unravel its secrets. The universe is a giant video game that a few of us get to play all the time. Yet somehow we manage to give everyone else the impression that it’s all about pulleys and inclined planes. If we can enlist the help of some imaginary characters — whether Spock or Spike — in illustrating the excitement of science, we’ll have achieved something very real indeed.

CATEGORIZED UNDER: Science and Society, Words

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Cosmic Variance

Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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