Is Faster-Than-Light Travel Possible Through Quantum Entanglement or Wormholes?

[Christov84]

Hi everyone,

I am fascinated with is FTL, black holes and wormholes and I have been contemplating the below for a while now.

are the likely FTL ever to be accomplished would be some form of tricky quantum entanglement for transmitting info or potentially finding a worm hole large enough that it wouldn't collapse when normal matter passed through it?

What if one could make a pipe or ring that was dense enough, would it be able to pinch space time enough that one could travel very large distances in a short amount of time?

Im thinking along the lines of a stargate pulling space towards it rather then opening wormholes?

Or spiraling binary black holes? Does spacetime shrink between them due to it being pinched?

 

[bcrowell]

Welcome to Physics Forums!

Quantum entanglement does not transmit information faster than light.

FAQ: Why can't anything go faster than the speed of light?

In flat spacetime, velocities greater than c lead to violations of causality: observer 1 says that event A caused event B, but observer 2, in a different state of motion, says that B caused A. Since violation of causality can produce paradoxes, we suspect that cause and effect can't be propagated at velocities greater than c in flat spacetime. Special relativity is one of the most precisely and extensively verified theories in physics, and in particular no violation of this speed limit for cause and effect has ever been detected -- not by radiation, material particles, or any other method of transmitting information, such as quantum entanglement. Particle accelerators routinely accelerate protons to energies of 1 TeV, where their velocity is 0.9999996c, and the results are exactly as predicted by general relativity: as the velocity approaches c, a given force produces less and less acceleration, so that the protons never exceed c.

The corresponding speed limit in curved spacetime is far from being established. The argument from causality is not watertight. General relativity has spacetimes, such as the Godel solution, that are valid solutions of the field equations, and that violate causality. Hawking's chronology protection conjecture says that this kind of causality violation can't arise from realistic conditions in our universe -- but that's all it is, a conjecture. Nobody has proved it. In fact, there is a major current research program that consists of nothing more than trying to *define* rigorously what the chronology protection conjecture means.

There are certain things we *can* say about faster-than-light (FTL) motion, based on the fundamental structure of general relativity. It would definitely be equivalent to time travel, so any science fiction that has routine FTL without routine time travel is just plain wrong. It would probably require the existence of exotic matter, which probably doesn't exist. If it were possible to produce FTL artificially, it would certainly require the manipulation of godlike amounts of matter and energy -- so great that it is unlikely that beings able to carry it out would have anything like ordinary human concerns.

There are many ways that velocities greater than c can appear in relativity without violating any of the above considerations. For example, one can point a laser at the moon and sweep it across, so that the spot moves at a speed greater than c, but that doesn't mean that cause and effect are being propagated at greater than c. Other examples of this kind include a pair of cosmic-sized scissors cutting through a gigantic piece of paper at greater than c; phase velocities greater than c; and distant, observable galaxies receding from us at greater than c, which can be interpreted as an effect in which space itself is expanding in the space in between.

 

[matheinste]

There are many ways that velocities greater than c can appear in relativity without violating any of the above considerations. For example, one can point a laser at the moon and sweep it across, so that the spot moves at a speed greater than c, but that doesn't mean that cause and effect are being propagated at greater than c. Other examples of this kind include a pair of cosmic-sized scissors cutting through a gigantic piece of paper at greater than c;

Reichenbach in The Philosophy of Space and Time, Dover Edition, page 147 deals specifically, and in a little more depth than in normal textbooks, with these two examples of "FTL signalling". The section heading, Unreal Sequences, while perhaps not entirely appropriate, does separate these examples from causal sequences.

Matheinste.

 

[Christov84]

ok so sweeping the laser across the night sky can cover two points at speeds greater then c.

Therefore what about something like a really long leaver that at its base rotating close to C. Would the far end be able to traverse distances at speeds greater then C?

 

[Mentz114]

ok so sweeping the laser across the night sky can cover two points at speeds greater then c.

Therefore what about something like a really long lever that at its base rotating close to C. Would the far end be able to traverse distances at speeds greater then C?

No, because the motion of the lever will travel at the speed of sound in the lever. The whole length cannot accelerate simultaneously.

If an immensely strong super-being tries to swing a very long baseball bat, the bat must bend and/or break before any of its parts reaches c.

 

[LBrandt]

ok so sweeping the laser across the night sky can cover two points at speeds greater then c.

Therefore what about something like a really long lever that at its base rotating close to C. Would the far end be able to traverse distances at speeds greater then C?

The "laser" example doesn't involve a mass moving at C. No object with mass can be accelerated to C, period! We aren't going to be able to "fool" physical laws by shining lasers across the sky or building giant levers.

 

[Christov84]

The "laser" example doesn't involve a mass moving at C. No object with mass can be accelerated to C, period! We aren't going to be able to "fool" physical laws by shining lasers across the sky or building giant levers.

Calm down. Just a question that was purely hypothetical.

Hypothetically the end mass would move faster then C should it be able to withstand the forces upon it agreed?

 

[LBrandt]

Sorry, I meant no disrespect when I inserted the exclamation mark. I only did it to reinforce and emphasize the postulate that nothing containing mass can be accelerated to the velocity of light. And no, not even hypothetically could the end mass be able to move at C. It has nothing to do with the composition of the substance or how strong it is, it's a postulate of special relativity.