
A Slower Speed of Light - po
http://gamelab.mit.edu/games/a-slower-speed-of-light/
======
adaml_623
I'm quite curious as to whether the speed of light across the game space
decreases instantaneously when you pick up an orb or whether the change in the
speed of light propagates at the speed of... umm light.

Also they definitely need to have a black hole or 2 chucked in and maybe some
miniature binary stars orbiting at relativistic speeds

~~~
m_darkTemplar
It's instantaneous. There's no answer in physics for what should happen when
you change the speed of light because that simply just can't happen. Therefore
we didn't bother doing something like prorogation at the speed of light.

We don't do gravity calculations, along with a few other things because we
didn't have time and they make the other effects hard to see.

In the future I would have liked to continue with the project and implement
some of this though.

~~~
astrobe_
Cannot happen? Would we able to detect it if it actually did happen?

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tjic
I remember reading a science fiction novel based on a similar idea perhaps 20
years ago. It was pretty good.

[http://www.amazon.com/Redshift-Rendezvous-John-
Stith/dp/1880...](http://www.amazon.com/Redshift-Rendezvous-John-
Stith/dp/1880448580)

~~~
ConceptJunkie
Man, the perils of tech. I read these comments over lunch at my desk, bought
the book on my phone and read the first chapter. It's _way_ too easy to spend
money these days.

On the plus side, I think I'm really going to enjoy this one. Thanks for the
recommendation. :-)

------
tgb
Also of interest: Velocity Raptor <http://www.testtubegames.com/srel101.html>

~~~
dexter313
Just finished the game, it perfectly simulates contractions and time dillation
on a 2D surface, check it out.

~~~
TestTubeGames
Thanks for playing, tgb and dexter!

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shocks
Very interesting, although I dislike the "ice rink" feel. It makes the game
very difficult to control. I'm unsure if this is intentional.

A sandbox approach might be good. I found myself wanting to experiment and
change the speed of time myself.

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m_darkTemplar
I(Ryan Cheu) was on the team that made this if anyone has questions!

Most of my work was on implementing the actual calculations for relativistic
effects.

It was coded in Unity Game engine in C# mostly. The hard calculations are
actually all calculated in a shader written in Cg (mostly just C) so they're
on the graphics card.

~~~
shardling
Is there a description anywhere of exactly how the FOV/perception of distance
changes as you get closer to _c_?

Also why is it that you can't see the Lorentz transformations until the final
orb? I'd have thought that they'd be apparent _somehow_ \-- is it somehow
cancelled out by visual effects?

~~~
m_darkTemplar
The papers I read in preparation for the project and my main references:

<http://dl.acm.org/citation.cfm?id=234537>
<http://dl.acm.org/citation.cfm?id=91423> [http://tobias-lib.uni-
tuebingen.de/volltexte/2001/240/pdf/01...](http://tobias-lib.uni-
tuebingen.de/volltexte/2001/240/pdf/01dissertation.pdf)
[http://www.google.com/url?sa=t&rct=j&q=&esrc=s&#...](http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB4QFjAA&url=http%3A%2F%2Flink.aip.org%2Flink%2F%3FAJPIAS%2F75%2F791%2F1&ei=746VUJLqMo600QHvjYH4CQ&usg=AFQjCNHtynoupTgY-D5NZV9w_OOWBWO4jw&sig2=68Vkty5ot144kQWRxWu1MQ)

There were also a few other documents I had but they don't appear to be hosted
online anywhere.

The Lorentz transformations are not as apparent as the visual effects, they're
not canceled out though. You can actually see them, try speeding up and
slowing down when you have >50 orbs. You'll see a warped view and such :)

~~~
shardling
I saw a qualitatively different type of warping at 100 orbs than I did at 99.
For instance, at 100 orbs, I would see the tops of arches bend and distort as
I approached them. No such effect was visible at 99 orbs. I'd pull it up again
just to double-check, but it's a bit of a pain to actually collect enough orbs
-- a freely adjustable mode once you've beaten it once would be nice :)

I also would have expected to see some sort of length contraction evident in
things like the fence post spacing, but I never noticed any.

~~~
m_darkTemplar
There was no difference in the calculations at 100 orbs, we just let v/c get
much closer to one. The effects were actually there before 100 orbs you
probably didn't notice much because of the colors! Internally the colors and
Lorenz and time invariance calculations effect different things, the 100 orb
stage just removes the operations done in the fragment shader--the vertex
sharer remains unaffected.

------
Ari_Rahikkala
It's Motion Sickness Simulator 2012! No, seriously, I've never had motion
sickness from FPS games but this one made me feel pretty uncomfortable. Those
who do get motion sickness should consider themselves warned.

That aside... it's not the first game/toy about illustrating relativistic
effects that I've seen before, for instance there's
<http://lightspeed.sourceforge.net/> and a funny little Flash game that I've
tried: <http://www.testtubegames.com/velocityraptor.html> . Neither of them
were very much fun.

This game was not very much fun either, but there was some promise, because at
the end once I'd gathered all the orbs by moving slowly and methodically, I
enjoyed skating around the level and trying to go as fast as possible without
bumping into things. Hopefully someone will use the engine (they say they're
releasing it next year) to do something really good.

~~~
martincmartin
Hans Moravec created a relativistic version of SpaceWar! in 1971:

<http://mathforum.org/kb/message.jspa?messageID=274527>

------
damncabbage
The site seems to be suffering a bit. Here's the cache:
[http://webcache.googleusercontent.com/search?q=cache%3Ahttp%...](http://webcache.googleusercontent.com/search?q=cache%3Ahttp%3A%2F%2Fgamelab.mit.edu%2Fgames%2Fa-
slower-speed-of-light%2F&oq=cache%3Ahttp%3A%2F%2Fgamelab.mit.edu%2Fgames%2Fa-
slower-speed-of-light%2F&sugexp=chrome,mod=0&sourceid=chrome&ie=UTF-8)

~~~
kzahel
In case you're not able to download the mac version because the speeds are
slow, here is a magnet link for it.

magnet:?xt=urn:btih:1828bafc3135e0b326d31c5030003d7004a86433

~~~
zokier
Anyone got magnet for windows version? I got 15KB/s from the site

~~~
kzahel
magnet:?xt=urn:btih:1828BAFC3135E0B326D31C5030003D7004A86433 (windows)

------
codeboost
Looks very psychedelic. It's interesting how simulating a variable speed of
light creates the same visual effect as that produced by ingesting psychedelic
mushrooms or LSD. Not just the color spectrum, but also the distance/space
distortions one reports while tripping. I guess those mushrooms in the game
are not a coincidence. Wonder what the connection is there then.

~~~
m_darkTemplar
Our initial plans involved mushrooms that grew due to the time dilation. They
were nice because they could grow straight up so we had easy time calculating
past positions. We only later realized the connection that you could make.

------
kzahel
Once you get all 100 orbs and you get close to the speed of light you're in
for a treat. It gets rid of the funny color saturation effects and you only
see the Lorentz transformation. I'd like to know the secret incantations to be
able to modify the speed of light manually. (Once you walk fast as light, the
game abruptly ends)

~~~
flebron
I think if you don't go under the white arch, you can stay indefinitely in
Lorentz transformations mode. At least, I stayed that way for several seconds
if I avoided that arch.

~~~
tzs
ESC also seems to end it if you have 100 orbs, instead of taking you to the
settings screen as I would have expected.

Also, be careful running with 100 orbs. I ran into a fence and got stuck on
it.

~~~
kzahel
the same thing happened to me (getting suck in the fence), and pressing escape
to try and turn the colors back on.

------
arjunbajaj
Not available for Linux! :(

~~~
munchor
That's something I didn't expect from MIT. It's ridiculous that they only
support Mac and Windows.

~~~
mistercow
Apparently the prolbem is that Unity3D still doesn't deploy to Linux, although
the next major version will.

------
gradschool
The Lorentz transformation (as I understand it) pertains only to inertial
reference frames moving at constant velocities relative to one another, hence
the "special" rather than the "general" theory. However, the player seems to
be able to stop, start, or change course at will. Wouldn't those actions cause
lots of effects (e.g., gravitational waves, etc.) that are not accurately
modeled in this simulation?

~~~
btilly
The special theory can handle acceleration perfectly well. What it can't
handle is gravity.

Therefore the game is fine in so far as it has been presented.

------
undershirt
I don't understand why the colors are changing. Shouldn't the doppler effect
not apply if the speed of light is the same for all observers?

~~~
vlasta2
With sound waves, your speed is added to the speed of sound and you hear a
different note. With light, the speed remains at c, but perceived energy of
the photons is still affected (energy must be preserved after all). And energy
~ wavelength ~ color.

You can also think about it being one of these "zero (weight of a photon at
rest) multiplied by infinity (energy of objects moving at c) gives a finite
number (actual energy of a photon)". The last number still behaves nicely.

~~~
undershirt
So, the speed of an observer affects its perceived energy of light. How does
"conservation of energy" apply? (I don't know what is contributing to the
energy of this system.)

~~~
psykotic
If you imagine an idealized light source, where photons come into existence
out of nowhere, then there is no conservation of energy (energy is being
created). But in a more realistic model where photons are emitted as a result
of electron excitation, say, energy is conserved because the electron recoils
when firing off the photon, so the extra observed energy of a blueshifted
photon can be found in the extra kinetic energy of the electron as observed in
that same frame of reference.

------
fungi
any one get it running in wine? i get through all the menus and story slides
but then boom.

~~~
omgtehlion
I got the same in windows (7, x64)

~~~
Ambadassor
Works for me on Windows 7, x64. Try updating your DirectX.

~~~
dioltas
Doesn't seem to work for me either on Windows 7 64bit.

Just installed direct X from microsoft's site, still no joy. Crashes just
after intro.

Any other libraries I might be missing?

------
memming
Someone should do the same with quantum mechanics by increasing the Plank
constant.

~~~
mayneack
I wonder how complex it would be to have a physics engine that allows for
arbitrary changes in fundamental constants.

~~~
padraigm
The thing is, most game engines don't even simulate Newtonian physics very
accurately; it would be much too computationally expensive to do so. Gravity
only works on certain objects and is usually a constant acceleration applied
along the vertical Cartesian axis, objects are composed of at most a couple
dozen perfectly rigid parts attached together at defined joints, liquids and
particles are simulated in batches using only rough heuristics, and so on. If
we were to allow arbitrary changes to fundamental physical constants, the game
engine would have to simulate the world from the quantum scale up.

That's a hard damn problem. There are some extraordinarily well-funded
research groups that are struggling to model any reasonably large number of
interactions at that scale. State of the art supercomputing clusters can
currently simulate systems of hundreds of thousands of atoms, not even in
real-time, and they're still making some assumptions along the way, which
might not hold true if you were to arbitrarily modify any fundamental
constants.

You could probably write a physics engine that passably pretends to simulate
some (non-arbitrary!) changes in fundamental constants. But it would be hard
to guess what matter would even look like for different values of, say, Z0.

~~~
mayneack
Yeah, I completely expect 99% of the changes to just resolve to "this is
something we can't possibly simulate"

------
lucian1900
This is both very interesting and a little painful for me. It's one of those
ideas that I've always wanted to try, but never got around to. In a way it's
nice that someone tried it anyway.

~~~
lloeki
With 0x10c around and discussions on space combat realism I was thinking about
some form of semi-realistic space "naval battle"/wargame.

So the first thing I thought was, well low-scale speed of light giving wonky
graphics is both cool and help getting the feel of relativity, but what about
some Homeworld or a Master of Orion type of game with relativity ingrained
inside the game rules and mechanics? Probably the music sounding Homeworld-
esque helped.

~~~
slackson
I imagine it would be quite difficult to have working multiplayer relativistic
mechanics. So far, I can only see single player mechanics working, which would
restrict the appeal of such a game.

~~~
jychang
Yeah, multiplayer without a unified sense of "time" doesn't seem to work very
well...

~~~
lloeki
That's only partly true.

Consider a turn-based game: a turn being irrevocably discrete and the same for
all players, each entity, depending on its relative speed - hence time
dilation/compression ratio - would get a different number of action points to
spend each turn. You can globally compute each item action points because
you're simulating the game universe.

You can extend this to virtually continuous time by compressing/dilating time
depending on the player's relative reference frame, and then you could cap the
flow of time so that min_flow=real_time or max_flow=real_time, or even
mean_flow=real_time. I could see this becoming a problem for say, a FPS game
where the player would feel relativity as time slows down or goes faster, but
for a much more global game applying such a scheme would make him witness each
unit/planet/whatever relative reference frame time dilations/contractions from
a sort of god-like reference frame. In a single player scenario (where you
don't need base time flow synchronicity between players) this god-player could
even change his own reference frame by scaling his base time flow between say
min_flow and max_flow.

~~~
shardling
I don't think it is quite that easy.

Try modelling the twin paradox that way, for instance...

------
aidos
Really cool concept! It takes a little while to wrap your head around what's
going on but as you get deeper into it things start to make sense. The faster
you move backwards the more light you lose which is rather disconcerting.

It's totally worth getting to the end (took me about 10 minutes) so you can
play around for a moment without the colour shift affects. Would be really
cool to have a version where you could do that.

Well done to the creators.

------
Eliezer
Doesn't run on Intel HD 3000 graphics, apparently. Alas.

~~~
m_darkTemplar
I believe it breaks if you don't have a lot of memory on your GPU. Never got
around to fixing that.

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ck2
Shouldn't mass be increasing as light slows down?

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aristidb
It's _barely_ playable on my 2011 MBA. Seems like the limitation is on the CPU
side though. Either it's fairly unoptimized, or this relativistic stuff is
just really demanding.

It's quite awesome anyways. Funnily if you change direction, that alone
triggers no relativistic effects.

~~~
egypturnash
Oddly enough it runs great on my late 2010 MBA.

~~~
shardling
Different MBAs have different CPUs -- I remember having the option to upgrade
when I bought mine, and the base 13" is beefier than the upgraded 11".

 _e:_ Ah, but it actually runs fine on my 2010 unupgraded 11" Air. I'd guess a
higher resolution screen would hurt performance, though.

~~~
aristidb
Maybe it's because the 2010 MBA had NVidia graphics, and the 2011 has Intel.

------
qiller
Also there was <http://realtimerelativity.org/> a while ago, which simulates
motion pretty close to C. Don't know which one is more "realistic", but it
shows much more pronounced effects

------
louischatriot
What a great idea. The "rainbow colors everywhere" effect if kinda annoying,
but the concept is awesome. As they say, that's what I would expect from the
MIT Games Lab.

------
ricardobeat
That video is kind of annoying. More gameplay, less talk.

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bobylito
Is it even a game? It seems to me like a very interesting simulation but I
don't see game design there...

~~~
shardling
The best definition I've seen for what constitutes a game is this: _A game is
an experience created by rules_.

That captures what distinguishes a game (as an artform) from other media. You
could throw in some qualifiers to perhaps narrow it down (is paying your taxes
a a game?) but it's not really necessary.

~~~
vacri
A prison sentence is a game?

~~~
shardling
Like I said, you can try to narrow it down, but it's pretty hard to define a
rigid line between _art_ and _not art_ in any medium.

Although your particular example is kind of amusing, given the prominent role
of the Prisoner's Dilemma in discussing elementary game theory! :P

------
smithzvk
They say it is open source but I can't seem to find the repository. Anyone
else see it?

~~~
JD557
Quoting from the site:

> IN PROGRESS OpenRelativity is a set of tools for simulating the effects of
> traveling near the speed of light in the Unity3D game engine. > The team is
> currently refining the documentation, usability and features in
> OpenRelativity, targeted for release as a free, open-source package in 2013,
> to allow others to produce more simulations and games about traveling near
> the speed of light.

So, it will only be availible in 2013

------
zokier
I immediately thought 'space (combat) sim!' when I heard that the engine was
open.

------
bitwize
Ladies and gentlemen, I think we found the Portal 3 game mechanic.

~~~
younata
What? There's not going to BE a portal 3...

However, this may be the Portal 2 Episode 1 game mechanic.

------
bluedanieru
This needs to go up on Steam yesterday. Or tomorrow, depending on your frame
of reference.

------
bluedanieru
I may be off-base here, but isn't the length contraction backward? Things
should appear closer as you approach the speed of light, not farther away.
And, it should not matter if you move backward or forward to observe that
effect, yet it does (try moving backwards).

Also, relativistic motion doesn't appear to affect the movements of the other
actors, though it's kind of hard to tell for certain.

~~~
StavrosK
With my very limited understanding, my impression is this:

As you move in relativistic speeds, your eye hits more photos, even those
going sideways (or backwards), because the photons at an angle are slower than
your eye (imagine a car moving fast through the rain, even drops that go in
the other direction will hit your windshield).

Therefore, your field of vision grows (you can see things behind you), but
only when walking forward.

I haven't read anything about going backwards, but I imagine that your field
of vision would shrink, as you are now faster than photons that would
previously hit your eye. My guess is that you would only see photons coming
directly to you from your front, until you reached the speed of light and went
blind (or could see 360 degrees, moving forward).

~~~
Evbn
Photons always travel at the speed of light in every frame of reference. Only
the medium matters, not the observer's speed.

The observable change is the separation between photons (wavelength) caused by
a moving source.

~~~
StavrosK
Photons traveling along an X axis are traveling along a Y axis at 0 m/s. If
you're traveling along the Y axis, you're going faster.

~~~
jasonwatkinspdx
Except that's not what we measure. Instead we find the speed of a photon
depends only on the medium, not on the motion of the source or receiver.

~~~
StavrosK
You aren't listening to me. The speed of the photon is c in the direction it's
traveling, a photon traveling due west is going north with no speed at all.

~~~
xnxn
I don't think it makes sense to say that the speed of a photon is c "in a
direction", since speed is a scalar quantity.

(correct me if I'm wrong, I'm terrible at physics!)

~~~
shardling
Here, speed is a measure of the magnitude of velocity. It's perfectly
acceptable to describe velocity (or a component thereof) as speed in a
particular direction.

