Second Life is an online world in which people use avatars to explore and interact with each other and to build more or less anything based on simple geometric shapes. These objects are governed by a set of roughly Earth-like laws of physics that simulate conservation of momentum, gravity, and elasticity in collisions and so on.
But Second Life also has a scripting language that allows residents to introduce additional effects. It allows them to buy and sell objects using virtual money, to create textures for clothing as well as animations.
And it allows the behavior of objects to be modified in various ways. In other words, in Second Life, the laws of physics are up for grabs.
And that raises an interesting prospect. This scripting language allows people to simulate universes in which matter is governed in an entirely different way.
Today, Renato dos Santos at the Lutheran University of Brazil in Canoas reveals his efforts to tamper with the laws of physics in Second Life and how his microworlds allow students to study and experience laws of motion that are entirely different from the ones that work in our universe.
To begin with, Dos Santos characterizes the properties of matter and the laws of physics that are already at work in Second Life. He points out that the world has some relatively complex laws to govern the weather and the rising and setting of the Sun.
“The Second Life ‘Sun’ usually rises and sets each four Earth hours always directly opposite a full Moon,” he says. And the servers compute a simplified solution of the Navier-Stokes equations to simulate the motion of winds and clouds that time-evolve across the entire world.
On the other hand, there are no fluids in Second Life. “Water is a mere texture applicable to an object,” he says. Consequently, there is no water resistance or air resistance and no concept of buoyancy. What’s more, light simply exists in Second Life without any physical mechanism involved in its production or propagation.
All these factors and others have to be taken into account when designing a microworld in Second Life. Nevertheless, Dos Santos has been able to create a number of interesting simulations.
A good example is his simulation of a cannon firing cannonballs to study their trajectory. One of the first challenges is to use the Second Life scripting language to introduce a set of initial conditions for the cannonballs—their initial velocity and position, for example.
Having done this, it is possible to calculate their position and velocity at any point during their flight. It is also simple matter to calculate their kinetic energy and momentum.
Once fired, these cannonballs do not travel in a straight line, however. Instead, gravity pulls them towards the ground and wind can push them off course. Dos Santos says it is possible to build rules into the scripting language that counteract these forces. That’s what makes possible an entirely different set of laws of motion.
To demonstrate this, Dos Santos has created two different sets of laws that can be put into operation with the push of a button. The first is Newton’s traditional laws of motion, which lead to the familiar parabolic trajectories.
The second set of laws are based on the theory of impetus that was popularized by Jean Buridan, a French priest and medieval scientist active during the 14th century. This theory was an important intellectual precursor to the more modern concepts of momentum and acceleration.
Buridan’s ideas were an extension of Aristotle’s theory that “continuation of motion depends on continued action of the force.” Buridan extended this by introducing a property called impetus which he formally defined as weight multiplied by velocity.
One of Buridan’s students described impetus in this way: “When something moves a stone by violence, in addition to imposing on it an actual force, it impresses in it a certain impetus. In the same way gravity not only gives motion itself to a moving body, but also gives it a motive power and an impetus …”
Buridan’s mathematical formula for impetus allows it to be incorporated into a Second Life simulation, which is exactly what Dos Santos has done. This allows students to experiment with different laws and see their effects.
Interestingly, Buridan’s laws result in a cannonball trajectory that is a little like that of a golf ball which travels on an upwards inclination and then suddenly drops due to air resistance.
You can watch videos of these experiments here.
That’s an interesting approach that has useful potential applications in education. But there is surely much more that can be done in virtual worlds like Second Life.
One interesting question is how to devise experiments within the virtual world that tests the particular laws of physics in action and the situations in which they break down.
For example, the concept of time might be investigated using experiments involving simultaneity. It might even reveal loopholes that can be exploited for a bit of fun.
An approach like that would require significantly more ingenuity and would simulate more accurately the work of physicists in the real world who do not know the laws in advance and have only their observations to guide them.
This kind of approach has been tested in virtual worlds such as Minecraft but there is clearly scope for the same approach to be applied elsewhere.
The laws of virtual physics are there for the taking, should anyone have the ingenuity and the spare time to pursue them.
Ref: arxiv.org/abs/1405.6703 : Second Life As A Platform For Physics Simulations And Microworlds: An Evaluation
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