One way to visualise how light is affected by gravity, imagine space time is like a flow of a tide or a medium and you are trying to go against it. At some point the tide is going to so fast that you can not counter it at your maximum speed, therefore you are swept with it... into a black hole.

Black holes are not the only things to effect the speed of light. Explain this.

http://abcnews.go.com/Technology/story?id=99111&page=1

I'm putting my money on a fluctuation on the space-time plane and for that specific moment, the emitter and the detector were 60 feet closer to each other. No laws broken.

[quote name='Tachikoma' timestamp='1317056253' post='4866132']
One way to visualise how light is affected by gravity, imagine space time is like a flow of a tide or a medium and you are trying to go against it. At some point the tide is going to so fast that you can not counter it at your maximum speed, therefore you are swept with it... into a black hole.

Black holes are not the only things to effect the speed of light. Explain this.

http://abcnews.go.co...id=99111&page=1
[/quote]

The speed of light changes depending on medium. It travels fastest in a vacuum. Its nothing new. Its like trying to get to the front of the mosh pit, to many particles to interact with

[quote name='Eelco' timestamp='1317046265' post='4866066']
snip

What are you talking about the theory of relatively does talk about time and therefore time travel. According to the theory of relatively the faster something travels the slower time passes for that object. Also the higher the gravity around an object the slower time passes for it. Therefore if you travel faster than the speed of light, according to the equation, you would go backwards in time. The notion of time travel was originally proposed by scientist studying relatively, not science fiction writers.
[/quote]

O RLLY?

Indeed, more velocity means slower passing of time; but clearly the geometry of the equation doesnt allow for the extrapolation you posit here, since time dilation as a function of v isnt even differentiable at v==c; it has an infinite slope. The correct extrapolation of ever more velocity isnt into negative time; the correct extrapolation is that the function doesnt extend into the v>c domain at all cause it completely curves away from that domain and doesnt point toward it at all.

Try and plug v > c into the formula for time dilation; you dont get a negative number as your naive extrapolation would have, but an imaginary one. An imaginary flow of time... indeed a concept more apt for science fiction writers than scientists. (or perhaps scientists looking to pry funding loose from people who never looked at the math themselves)

[quote name='Discount_Flunky' timestamp='1317054850' post='4866119']
[quote name='Eelco' timestamp='1317046265' post='4866066']
snip

What are you talking about the theory of relatively does talk about time and therefore time travel. According to the theory of relatively the faster something travels the slower time passes for that object. Also the higher the gravity around an object the slower time passes for it. Therefore if you travel faster than the speed of light, according to the equation, you would go backwards in time. The notion of time travel was originally proposed by scientist studying relatively, not science fiction writers.
[/quote]

O RLLY?

Indeed, more velocity means slower passing of time; but clearly the geometry of the equation doesnt allow for the extrapolation you posit here, since time dilation as a function of v isnt even differentiable at v==c; it has an infinite slope. The correct extrapolation of ever more velocity isnt into negative time; the correct extrapolation is that the function doesnt extend into the v>c domain at all cause it completely curves away from that domain and doesnt point toward it at all.

Try and plug v > c into the formula for time dilation; you dont get a negative number as your naive extrapolation would have, but an imaginary one. An imaginary flow of time... indeed a concept more apt for science fiction writers than scientists. (or perhaps scientists looking to pry funding loose from people who never looked at the math themselves)
[/quote]

When you put v = c you get 0 which means times stops for the object. The thing is though that getting anything to go the speed of light that has mass takes infinite energy, because things also get more massive the faster they go. According to the equation mass is infinite at the speed of light therefore the energy needed to go faster then the speed of light is impossible to reach. That is way the possibility of Neutrioes going faster then light is so freaky, because that implies that there is a loop hole in relativity.

When most scientist speak of time travel mostly they speak of using something like a black hole's gravity field to make yourself live way longer then you normally would so that you can see the future. The only way to got to the past would be a worm hole, and those haven't been proven yet. Also you could only go back to the time that the worm hole was created.

Edit: Also just because something sounds far fetched it doesn't mean it's form or should only be mentioned in science fiction. There's a lot crazy science out there. For instance many scientists are starting to find proof that humans have a sixth sense.

[color="#1c2837"]it might be an interesting dabble into science fiction to open another topic and try and fantasize what the arrow of time actually is and why we perceive it the way we do. Because I don't believe anyone really has an idea.

I was under the impression that the 'arrow of time' was simply entropic decay, leading the universe to move from one state to another (order to disorder if memory serves). So given two space-time reference points one in the past (A) and one in the future (B) to go from B to A would require that you could get back to the state the universe was in at point A, which I'm pretty sure is covered as a 'no go' in at least one 'law' (Thermodynamics springs to mind, but dont' quote me, I'm going on half remembered stuff). Or to put it another way; at 4:08pm I break an egg, any attempts at time travel to 4:07pm would require going back to a point where the egg was no longer broken.

IF this is proven correct and IF we can make use of it the only real use I can see is FTL communication. Now, with respect to light speed this is a form of time travel, in that information could make it from one location to another before light (to use the sci-fi example you'll be able to see the enemy fire his laser slightly before it starts trying to remove your hull) but it only remains 'time travel' in that sense.

To give a poor example;
Two space ships are 5 light seconds apart with clocks which are syncronised; at 10seconds past the minute space ship one fires a laser beam at spaceship two, 15 second past the minute space ship two is hit, 20 seconds past the minute spaceship one sees the hit.

With FTL vision when spaceship one fires spaceship two might see the beam coming at 13 seconds past the minute but he still didn't see the event before it happened. Spaceship one would see the 'hit' at 18 seconds past the minute as the event didn't happen until 15seconds past the minute.

The only way this could result in time travel is if Spaceship two saw the laser coming BEFORE 10 seconds past the minute, in other words before the event happened.

So, in short; while I'm no top physicist I'm pretty sure that we are safe from time traveling robots from the future bent on trying to kill people named Connor for a while yet ;)

For instance many scientists are starting to find proof that humans have a sixth sense.

Can has links?

[quote name='Discount_Flunky' timestamp='1317076118' post='4866247']
For instance many scientists are starting to find proof that humans have a sixth sense.

Can has links?
[/quote]

http://noosphere.princeton.edu/

http://en.wikipedia.org/wiki/Rupert_Sheldrake

These are some I could find. It's really hard to get links about scientific developments when you don't know the name of the experiment or the names of the scientist evolved

[quote name='irreversible' timestamp='1317052673' post='4866103']
[color="#1c2837"]it might be an interesting dabble into science fiction to open another topic and try and fantasize what the arrow of time actually is and why we perceive it the way we do. Because I don't believe anyone really has an idea.

I was under the impression that the 'arrow of time' was simply entropic decay, leading the universe to move from one state to another (order to disorder if memory serves). So given two space-time reference points one in the past (A) and one in the future (B) to go from B to A would require that you could get back to the state the universe was in at point A, which I'm pretty sure is covered as a 'no go' in at least one 'law' (Thermodynamics springs to mind, but dont' quote me, I'm going on half remembered stuff). Or to put it another way; at 4:08pm I break an egg, any attempts at time travel to 4:07pm would require going back to a point where the egg was no longer broken.
[/quote]

This really is an interesting topic and my post will quickly spiral out of control, but that's only because there's no real answer to this question.

First off, allow me to make a small correction to the terminology you used: since entropy is a measure of disorder and the universe started out in a state of almost perfect order, then entropy is necessarily growing, not decaying . But that's that.


Strangely enough entropic growth cannot be proven to be the cause of the arrow of time as it would actually create a causal loop: entropy cannot grow without time. Unless your example regarding the broken egg is a coincidence, it seems you're familiar with Brian Greene's The Fabric Of Cosmos (if you're not, then he discusses the arrow of time very thoroughly - it's quite an exhilarating read). While his argumentation largely explains that since pretty much all of physics (with the exception of some negligible effects from the weak force) is time-invariant (in other words the laws of physics do not forbid time to run in reverse, causing the egg to unshatter), there is no apparent reason for entropy to grow.

It might seem logical that a uniform mist of particles that contains impurities has the potential for entropic growth, but that doesn't quite explain why a) the universe couldn't be experiencing decreasing entropy instead (actually the answer to this would be negative gravity and the reversal of all other forces in nature) and b) why the two would be linked (at this time the cyclic universe is no longer considered a viable option due to its rate of expansion, but a cyclic universe would actually have required the reversal of time to achieve the big crunch). A better answer could be to interpret time as a potential of entropic growth, but again there's no proof of this anywhere other than the fact that the properties of forces cause it to go down this route.

Consider another example that stems from the bubble multiverse theory: "infinite time on the outside equals infinite space on the inside" (this is why a bubble universe might seem infinite on the inside, but is finite on the outside). This in turn brings up two problems to which there are currently no solutions: a) (our) mathematics doesn't have a branch that can reliably handle infinities meaning that we cannot explain how something that has no beginning and no end can flow from one to the and b) and logically, if an increase in entropy is a causal property (not a side effect) of time and there's a finite amount of matter/energy (either in the universe or the multiverse), then at one point you'll still reach the Russian doll situation where you need to explain the starting state of the universe/multiverse and will eventually run out of time as entropy reaches a maximum.

This is all bollocks, though as the ugly truth behind it is that time is a quality/dimension/phenomenon/river we simply do not understand.

As a small thinking exercise consider a simulated universe (khm, a computer game) where, at each iteration, you increase all values by a certain (fixed) amount. This amount doesn't even need to be based on time in our universe - it just happens at every iteration. This means that to the characters in the game time would seem to be flowing at a constant rate. The questions to answer are:

1) why are you increasing (not decreasing or randomizing) all the values at each iteration?
2) would your game character ever hope to understand your nature or your motives?
3) this one is also from Brian Greene: can you yourself imagine a universe without space and time?