Quote: Original post by ddn3
Maybe time doesn't exist and the universe is ever present simultaneously and your just some cosmic spark of consciousness which wills itself to manifest at this particular coordinate phase space ;) if that's the case it won't take any time at all for the changes to propagate but unfortunately you can't make any changes which haven't already been done.

Enjoy!

-ddn

On the bright side, this means that aging and death are an illusion and that we are all immortal, because any time in which we are dead is just a set of points in space that doesn't have our "consciousness" in it, which, by definition, means that we will never "reach" or even "approach" that set.

Quote: Original post by Sneftel
This question seems about as meaningful as asking "how far does it take for over there to get over here."

Wrong analogy... it would be the same as asking "how long does it take you to see something that happened over there, over here" ... answer being the speed of light (without being pedantic).

Quote: Original post by IFooBar
So I was watching sound of thunder today...

So that's the name of that movie. All this time I was trying to recall that. Whenever the topic of 'worst sci-fi movie' is brought up in a conversation, I have always said "That movie where a group of people went to 1m years ago and managed to kill something which then changes everything".

Did this just run dry faster than owl's "someone pulled a gun on me" thread? Seriously? owwwwwwlllll! :D (khaaaaannnnn, anyone?)

This thread's a little heavy for a gamedev forum, isn't it?

Unless we're talking about Braid.
Great game.

I think you've misunderstood the essence of spacetime ...

Good post. If I may, I'd like to clarify a few things with different language, for those who did not study relativity yet...

The thing that limits propagation is termed 'causality', and as mentioned above, the maximum propagation rate is the speed of light c.

Think of it this way: everything everywhere in spacetime is in constant motion...

That's totally right. Motion through space and time are mutually exclusive. The stress-energy tensor's T_{00} component is "the flux of energy through time", and the momentum components are "the flux of energy through space".

Ditto, "the flux of momentum through space" can be loosely translated as "pressure", and "the flux of pressure through space" can be loosely translated as "viscosity".

My point is that the phrase "the flux of momentum through time" is kind of confusing, though not technically incorrect. Why not just say "momentum", or "the flux of energy through space"? I realize that this is largely about personal preference, so feel free to tell me to go fly a kite.

General relativity, in conjunction with special relativity, prohibits time travel by imposing the speed of light as a physical barrier. It is quantum mechanics with quantum entanglement and string theory that propose certain hypothetical workarounds for this.

Not necessarily true. Closed timelike curves and Morris-Thorne wormholes are theoretically viable options. The wormhole allows material to go from one point in space to another at apparently "faster than light" speeds because the material actually skips traveling through space. Ditto, the metric expansion of space can allow pieces of matter to carried away from each other at a rate as fast or faster than 2*c, like what happened when our universe was rapidly inflating in its youth.

To address your time travel argumentation, accelerating to speeds faster than c would mean flipping the orange arrow across the horizontal axis, which is strictly impossible. Special relativity ensures this and general relativity is dependent on and an extension to special relativity.

True. Accelerating to c and beyond is impossible because it would require an infinite amount of energy to make it happen, but this is different than the metric expansion of space or traveling through a wormhole. I just wanted to point out that "time travel" is possible in plain-old-classic General Relativity.

re: butterflies and hurricanes...

There are two types of determinism. Classical determinism, and deterministic chaos. Classical determinism allows you to fully predict the state of the system at any time in the future, whereas deterministic chaos does NOT allow you to fully predict the state of the system at any time in the future.

Small changes in initial conditions of a system can and do indeed make for huge changes in the future. They don't get washed out like you're implying. That's what Lorenz thought would happen, but he found out that he was dead wrong. It's how deterministic chaos came to be discovered.

If you're not convinced by Lorenz, then also see Ruelle-Takens' modern work on turbulence. It is now our standard model, and like Lorenz's model it is driven by deterministic chaos, not classical determinism. They replaced Landau-Hopf's model. Landau and Hopf were supergiants of science and math and whatnot, but they simply just didn't have the tools that Ruelle-Takens had in order to come to the correct conclusions. I'm sorry man, but your opinion is not scientifically sound. It contradicts 50 years worth of reproducible experiments.

I won't go deep into why quantum physics is not deterministic, mostly because I'm horrible at it, but look for the articles on the net on how to make a random number generator from the Americium in a smoke detector. The process involves the weak force transforming quarks from one kind to another, which results in the shooting out of short-range/unstable W particles that decay into all kinds of nasty long-range/stable things that can dig real nice and deep into your thyroid gland.

Quote:Original post by Sneftel

Quote:Original post by Sirisian

Quote:Original post by Sneftel
This question seems about as meaningful as asking "how far does it take for over there to get over here."

You can actually solve that problem with a range. It never gets over here or it travels at the speed of light since that's the fastest information can travel.

Er, OK. So how far, in meters, does it take for 5 meters away to get here? Remember, the speed of light in a vacuum is approximately 3x10^8 m/s.

In Minkowskian spacetime the distance and time metrics are interchangeable.

... but only because we add a factor of c to the time component in order to convert it from seconds to metres ...

I find it impossible to believe that Sneftel has not heard of this, or of geometrized units before... sorry man, but you're a math genius, and I'm pretty sure you're just teasing irreversible for fun.

re: butterflies and hurricanes...

Fancy that, a James Gleick article on cnn.com, today of all days...
http://www.cnn.com/2...eick/index.html

Once you've read this, maybe read his book Chaos. Once you've done that you should have a good grip on entropy AND chaos.

Information is "nonrepetitive data". That's not 10,000 words, so don't sweat it. The complexity of the topic is illusory.

Don't believe me? Try compressing a 100,000 byte JPEG photograph and a 100,000 byte text file that contains only newline characters. The JPEG photgraph is practically incompressible compared to the text file. That's because the JPEG photograph's entropy is higher -- it has a higher information content per byte.

It all depends on the system, the amount of elements that are interacting and the amount of elements that get changed.

To know how a change in the past would affect the future you'll need to know the future and include it into the algorithm.

It's not the same to vaporize 1kg of rock 700 m down the surface of the earth than vaporizing 1kg of brain inside Einstein's skull.