Im gonna try to list the possible ways that FTL could be possible, and a few more likey possibilities for space travel.
Its generally thought that special relativity gives a short and negative answer to this question, but infact there are a number of trivial ways that things can go faster than light(FTL), and other more genuine possibilities. This doesnt mean that one day thanx to technology FTL will be inevitable, relativity says a lot about this, as if FTL travel or communication were possible causality would most likley be violated, and this would have some very strange repocussions.
Firstly the more trivial ways of FTL.
One possible way to go FTL is to slow the speed of light down, In a vaccum light travels at c (universal constant) but in a more dense medium light slows down ie- through water. Therefore it is possible for particles to travel faster than light through something like water, This is generally thought of as trivial as FTL travel is generally thought of as travelling through a vaccum.
Observation of FTL, it is possible to make an observation of FTL. ie- 2 rockets one flying west from me at 0.6c and one flying east at 0.6c. The spacial increase between the two rockets as observed by me is growing at a rate of 1.2c(.2 faster than c) Although this is not whats generally meant by relative speeds.
Shadows and light spots also have FTL capeabilities, but these are not physical objects so travel is not possible this way and information can not be sent this way so communication is not possible this way either.
Gravity. Some have speculated that gravity travelling within a gravitationally bound system travells much faster than light(c) even upto an infinite speed, this is wrong, gravitational effects and waves travel at the speed of light(c.) So cant be done this way.
The EPR paradox (Einstein, Podolsky and Rosen.) (quantum entanglement) the fact that there can be an apparent instantaneous interaction in the measurement of two separated particles that have been prepared in a certain "entanglement" manner (Einsteins "spooky action at a distance") unfortunatley no information can be passed using this, so FTL communication is not possible this way.
Quantum Tunneling.(bit confusing this one) This is a mechanical effect that allows a particle to pass through a barrier, the calculations can show that the particle can pass through the distance of the barrier faster than light can travel.
"a group of physicists have performed experiments that seem to suggest that FTL communication by quantum tunneling is possible. They claim to have transmitted Mozart's 40th Symphony through a barrier 11.4cm wide at a speed of 4.7c. Their interpretation is, of course, very controversial. Most physicists say this is a quantum effect where no information can actually be passed at FTL speeds. If the effect is real it is difficult to see why it should not be possible to transmit signals into the past by placing the apparatus in a fast-moving frame of reference."
Before this can be given any real credence, the experiments need to be conducted over more distance as there are other possible reasons that this could of occured.
The Casmir Effect. (Vaccum energy) Photons when travelling accross this vaccume travel very very slightly faster than c. Also its thought that in the vacinity of certain cosmological situations, such as cosmic strings (if they exist) could be much more pronounced, although once again further experimentation has shown that FTL communication is not possible this way.
The Expansion of the Universe. It is generally accepted now that galaxies are not moving away from each other, infact it is the space in between that is getting bigger the galaxies are not actually moving. As explained about special relativity its like 2 rockets travelling away being obseved by a 3rd party, so FTL is not possible using this method either.
As im sure the previous examples have shown its not even easy to explain what FTL is, the above difficulties are insurmountable and none of these will probably lead to FTL.
Weve all heard the infinite energy argument - cant accelerate something to light speed as energy becomes infinite(its a common mis-conception that this is Einsteins idea it was actualy suggested by a frenchman a year earlier.) This does rule out FTL travel through mechanical means but does not rule out FTL travel, this realy just says nothing can be accelerated to FTL.
Relativity arguments against FTL.
Quantum field theory. This theory is showing to be far from self consistent and full of holes so im gonna leave this one alone for now.
Grandfather Paradox. One of the best arguments against FTL is the grandfather paradox, in special relativity an object travelling FTL in one frame of reference will also be travelling back in time in another, theres also the possibility that if FTL is achieved causality could break down in some fasion. These are not very likley but you have to be open minded when talking about FTL.
Also the multiverse theory gives a possible way that time-travel could be possible withought causality breaking down - roughly if you went back in time and changed anything, at the moment anything changed a new universe would split off containing you and any possible changes, the future you came from would still be there + the one youve just created.
Most likley possibilities for FTL travel.
These are highly speculative yet serious possibilities.
Tachyons. These are highly speculative and no proof has been found that they exist, the truth is that most physicists consider tachyons to be a sign of pathological behaviour in field theories. (lots more work needed on this one)
Worm Holes. Inorder to keep a wormhole open, regions of negative energy would be needed. Two possibilities have been suggested for this, one using the Casimir Effect on a massive scale to create the negative energy, the other is using cosmic strings but neither of these theories may be possible. Exotic matter with negative energy may not exist in the form required. Hawking says that worm holes would simply be unstable and therefore unusable. (but hes been wrong before.)
Warp Drive. (my favourite one) Warping space-time in such a way that an object could move faster than light. To make such a warp, you would need exotic matter with negative energy density. Unfortunatley its still unclear as to how these could be used to make warp drive work. - but this is generally thought of to be a very good idea due to space-time geometry which describes such a warp drive.
So in conclusion, and its a crappy conclusion. We dont know, it seems highly un-likley but there is possibility.
Atheism is a non-prohet organisation.
http://video.google.com/videoplay?docid ... so=1&dur=3
http://video.google.com/videoplay?docid ... 6549&hl=en
When Britain first, at Heaven's command arose from out the azure main; this was the charter of the land, and guardian angels sang this strain: "Rule, Britannia, rule the waves: Britons never will be slaves."
James Thomson (1700-1748)
Dont think about the speed of light as a limit though, It could tun out to be no more of a limit than the sound barrier was. I like the warp drive one i think its got one of the best chances of working, the LHC can help understand a lot more but its so damn dangerous.
Atheism is a non-prohet organisation.
http://www.cbc.ca/health/story/2000/07/ ... 00720.html
If it is inertia that is giving to much drag when mass reaches c that there would never exist enough energy to push it faster, then we must somehow influence inertia. Hopefully it is a quantum vacuum field arrangement, then maybe there is a way to influence the vacuum to reduce or add to these forces.
But what about time. Maybe we cannot travel faster without changing in relative time, we would need a different thing to fix that. There is no way I can be in a blink of a second at a star i see in the sky, just because what we see is old time of course. The star could be gone or is at least somewhere else. Probably we could move (the configuration of) mass through the universe extremely quickly, but light still doesn't so we will really need to say place and some sort of relative time.
As for the time thing warp drive would be a warping of space-time.
Atheism is a non-prohet organisation.
http://www.torrentz.com/06db4c42dd05f2d ... b479735910
I think of inertia and gravity working like magnetism. It is a force that exists because of the right hand rule and a lot of spinning things (nuclei, electrons, strings...) in matter aligning.
If we could nullify this relation between moving and spin alignment we could move through space dragless.
As for warping. I don't think we can compare it with speed of light or anything through unwarped space. If we could warp some piece of space in front of us and just walk into it, then the light we emit/bounce would still be there faster.
But it could surly mean that we travelled a lot more distance in unwarped space than light could ever have in the same amount of time.
But in the end, do I believe we or others can move star distances or even galaxy distances? Yeah, these distances are way to little compared to the whole universe to not be reached, I think the ufo fenomenon is real so they seem to show us and all forces and universal constants are the way they are because of some sort of equilibrium sets them there. So nothing is a fixed constant, everything is modifiable.
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