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# Virtual reality physics.

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Physics in a virtual realty cannot ever be as accurate as in real life it seems. Just look at this video about time dilation:

YouTube - Time Dilation - Albert Einstein and the Theory of Relativity http://www.youtube.com/watch?v=KHjpBjgIMVk

Now imagine this happening in a virtual reality with one observer on a computer looking at the screen and the other in the space ship. What would happen? Time must flow at the same rate for both for the simulation to work.

Also another problem:

YouTube - Simultaneity - Albert Einstein and the Theory of Relativity http://www.youtube.com/watch?v=wteiuxyqtoM&NR=1

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Yes your right, because in VR a fake time can be dilated, but they cant dilate the time of the observer (yet :D)

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Physics in a virtual realty cannot ever be as accurate as in real life it seems. … Time must flow at the same rate for both for the simulation to work.
Agen is correct, assuming that what is referred to by “virtual reality” is something similar to present-day systems, in which an essentially unaltered human being interacts with some collection of devices. Examples of such systems include
• one made by the long-defunct Virtuality Ltd, a system briefly popular, mostly in in the 1990s in which a player stands on a motion-sensitive platform while wearing a motion sensitive headset containing a small display screen for each eye
• CAVE, a system that rear-projects an image onto 3 walls and the floor (practically speaking, people never look up and can’t look backwards, so a 5th and 6th screen isn’t necessary), sometimes utilizing 3-d glasses.

”VR” sometimes refers to hypothetical futuristic schemes in which the player is a computer program (eg: the 1999 movie ”The Thirteenth Floor”) or has computer interface devices surgically implanted or otherwise intruding directly into their nervous system, permitting software to control such perceptions as memory and the sense of passage of time (eg: the 1999 movie ”The Matrix”, it’s trilogy, and its many spinnoffs, imitators, and literary predecessors, such as 1980s cyberpunk fiction, or an early example, the 1966 short story “I Have No Mouth, and I Must Scream”). In this sort of hypothetical scheme, effectively any physically possible (and many physically impossible) simulations are possible – though it seems like a lot to go through just to get an accurate, first-person experience of the effects of relativity! :D

Relativity can be perfectly simulated as long as a game has only one player, as the game’s “AIs” can be made to experience any relativistic effects, allowing the player’s reference frame to be kept unaltered.

If you’re not concerned with the “immersive” aspect of virtual reality – its user’s ability to somewhat believe “it’s really there” – it’s not too difficult to include relativistic effects in a turn-based (non-real-time) simulation game. I actually tried this with a good-sized (12) group of sci-fi gamers (using a computerized version of the SPI’s board & paper game Vector 3), but it was never popular, as most people found it confusing, counterintuitive, and generally “too much science, not enough fiction”.

Also another problem:

This is an illustration of one of several counterintuitive predictions of special relativity commonly grouped under the name ”the ladder paradox”. The usual throught-experiment, involving long ladder that appears to a stationary observer to be briefly contained in a 2-door barn with both doors shut, while to the observer, this is impossible, and never happens, is even weirder than the video’s.

It’s not a hard effect to simulate – provided, as noted above, that the simulation is either non-real-time or single-player – and will emerge without additional programming from any simulation that accurately includes special relativity.

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Another way I think that time dilation can be used in a simulation would be if the users are completely integrated to the system. Meaning we could manipulate about anything what they see, what they hear and what they feel. In that case only if we can actually slow their brain down in some sense or use some other technique this could actually work. But if the users are connected the "ordinary way" (meaning a mouse, a keyboard and a screen) this can't be done.

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Another way I think that time dilation can be used in a simulation would be if the users are completely integrated to the system. Meaning we could manipulate about anything what they see, what they hear and what they feel. In that case only if we can actually slow their brain down in some sense or use some other technique this could actually work.
Sounds like a Matrix-esque “plugs in the brain, drugs in the vein” solution.
But if the users are connected the "ordinary way" (meaning a mouse, a keyboard and a screen) this can't be done.
Never say can’t, I always say!

If the users play while orbiting a massive body – say a nice, cool neutron star – the VR program could actually time dilate them as needed by changing their orbits.

Assuming an nice neutron star (lots of neutronium, not much junky ordinary matter crust, no annoying rotation), with radius 10 km, and mass 2 solar masses, dropping a user/player into a circular orbit 100 m above its surface will give a gravitational time dilation of $\sqrt{1 - \frac32 \cdot \frac{r_0}r} = \sqrt{1 - \frac32 \cdot \frac{5928}{10100}} \dot= .35$ (5928 m is the neutron star’s Schwarzschild radius), which is equivalent to a velocity time dilation of $\sqrt{1 - .35^2} \dot= .87 \, \mbox{c}$.

Of course, if you have the technology to orbit space video game players around a neutron star, the ride to the game is likely to be better than the game! ;)

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What you are describing is not the "ordinary way" as I meant it. The simulation is not allowed to manipulate you physically in such a way. It's only allowed to show you the light from the screen and the sound waves from the speakers.

If you where to add the "trip" so you could create a time dilation effect then it's not the "ordinary way" anymore. Then its more like adding a moving/vibrating chair to the monitor, speaker, mouse, keyboard or/and joystick for a more realistic effect. But in the "ordinary way" anything other than a monitor, speaker, mouse, keyboard or/and joystick are not allowed.

So in this case relativity can't be 100% added to the simulation now can it.

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