Spacetime
Diego Montoya
Spacetime is a research project consisting of VR special relativity simulation for the Oculus Quest, where the light-speed c is much lower than usual. Space contracts, time dilates and light shows a Doppler effect according to your movements.
The main goal of the experience is to allow for a more intuitive and natural understanding of how space, time and light behave when an observer approaches the speed of light.
The project presented many challenges. Developing it while observing how people explore the experience allowed for several findings:
- The world feels very “wobbly” when moving very close to the speed of light, almost liquid
- Teleport transports you at about 0.994c. When c is very low (1.5 m/s) teleporting goes like: world compresses -> shift very slowly towards goal (which is closer now) -> world uncompresses
- Also, at this c speed, some aspects of the twin paradox are easier to grasp. In the video, see how time runs slowly for the fans, while the observer’s time passes “normally” as they teleport across the room
- When c is about 10 m/s, teleporting is like being inside a huge accordion and going from one side to the other in a quick squeeze
- If c is much higher (e.g. 100 m/s), it feels like the usual teleport
- Doppler effect: Lots of light shifts outside the visible spectrum, the remaining draws a rainbow ring, so you only see the ring in the direction of travel
- If you could see infrared as red and ultraviolet as purple, it would look like a rainbow ring, with purple in the inside and red in the outside
- In stereo (VR), the light shift shows an occlusion-parallax conflict. In other words, the color tunnel looks like it’s behind all objects, but you see it nevertheless. This is because color shift depends on speed and angle to the observer (eye) and not to the distance from it. That's because eyes move in parallel so same color shift happens in infinity
- The Doppler effect can be a very colorful phenomenon
- Ehrenfest paradox: rotation and orbiting also causes objects (controller in the video) to compress in space. Note: this phenomenon was not fully implemented
- Time dilation and contraction cause high frequency noises. Time curvature results in frequency modulation. Note: sound Doppler effect was not implemented, so this is probably not very accurate
- Time travel is weird, theoretically and in code. In this simulation it might mean squishing so much that geometry is inverted, sound and animations go backwards
- Lorentz transformations are complex. Typical game engine operations don’t do the trick
The speed of light affects many phenomena, and the scope of this project covered a limited set of them. Some other phenomena, for example light-speed for photons (pixels), is not fully simulated. This means that there are inaccuracies, or aspects that are plainly wrong strictly speaking. Accuracy or formality were not the main goals of this project. Nevertheless, such a simulation can help make relativity more intuitive and easier to grasp.