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A new model for faster-than-light travel that uses conventional physics

popularmechanics.com

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Re: A new model for faster-than-light travel that uses conventional physics

#71

Post by greggyb »

nick_kline wrote: post #57

Instead of negative energy this warp drive idea requires 10^30 more energy than the matter contained in Jupiter, so we aren't quite there ;-). The additional issue is whether something going faster than the speed of light violates causality, like a warp drive. I've never understood how to reconcile causality with the fact of so called 'spooky interaction at a distance'. If it's faster than the speed of light, and you…

You got your quote wrong by an order of magnitude of order of magnitudes. (;

> requires roughly 100 times the energy contained in the mass of Jupiter, said Lentz. That’s about 30 orders of magnitude higher than the power of modern nuclear reactors.

Re: A new model for faster-than-light travel that uses conventional physics

#73

Post by Ono-Sendai »

nick_kline wrote: post #57

Instead of negative energy this warp drive idea requires 10^30 more energy than the matter contained in Jupiter, so we aren't quite there ;-). The additional issue is whether something going faster than the speed of light violates causality, like a warp drive. I've never understood how to reconcile causality with the fact of so called 'spooky interaction at a distance'. If it's faster than the speed of light, and you…

Faster-than-light communication doesn't necessarily break causation, if there is an absolute reference frame (blog post plug: http://forwardscattering.org/post/36)

Quantum 'spooky action at a distance' is something else though, as you can't communicate info with it (see 'no communication theorem').

Re: A new model for faster-than-light travel that uses conventional physics

#74

Post by 6gvONxR4sf7o »

zamalek wrote: post #63
SideburnsOfDoom wrote: post #48

Earlier quoted context omitted.

Nope. Literally any method of getting from A to B faster than light would, has a causality paradox. it does not matter if you cover the miles between FTL, or pop out of a hypothetical wormhole gate: If you end up outside of your own light cone, no matter how, there's a causality paradox.

The article calling it FTL isn't entirely correct. You aren't travelling faster than light. Spacetime can, and routinely does, exceed c. One possible solution to the problem is time expansion in the bubble: taking a 200ly trip would age the universe by 200 years outside the bubble (from the frame of reference of those inside).

But isn't the entire thing that it appears faster than c to an outside observer? Like, that's the definition? In which case an outside observer would have less than 200 years until the thing went 200ly.

Re: A new model for faster-than-light travel that uses conventional physics

#75

Post by zamalek »

FreeFull wrote: post #69
zamalek wrote: post #63

Earlier quoted context omitted.

The article calling it FTL isn't entirely correct. You aren't travelling faster than light. Spacetime can, and routinely does, exceed c. One possible solution to the problem is time expansion in the bubble: taking a 200ly trip would age the universe by 200 years outside the bubble (from the frame of reference of those inside).

But if you travel at close to the speed of light (without exceeding it), the universe will age 200 years when you take a 200ly trip. In which case, I'm not sure if there is any benefit to dragging around a bubble of spacetime?

The bubble would let you surpass c, and would "only" need the mass-energy of Jupiter (without optimizations) vs. the entire mass-energy of the universe.

Re: A new model for faster-than-light travel that uses conventional physics

#76

Post by jackcosgrove »

papaf wrote: post #16
xyzzy21 wrote: post #10

Not when the system requires energy equivalent to many Jupiters. To create a useful system you'd need to consume a Sun-sized star of mass on a monthly basis. We aren't there and honestly I don't see us ever being there.

My feeling is that interstellar travel will be slow and require many generations of travelers -- or not done by human beings at all.

I don't think humans themselves will travel between stars. If we find habitable planets, we'll send probes with bioreactors that can then be fed a stream of individuals' DNA to populate the planet.

Re: A new model for faster-than-light travel that uses conventional physics

#77

Post by zamalek »

6gvONxR4sf7o wrote: post #74
zamalek wrote: post #63

Earlier quoted context omitted.

The article calling it FTL isn't entirely correct. You aren't travelling faster than light. Spacetime can, and routinely does, exceed c. One possible solution to the problem is time expansion in the bubble: taking a 200ly trip would age the universe by 200 years outside the bubble (from the frame of reference of those inside).

But isn't the entire thing that it appears faster than c to an outside observer? Like, that's the definition? In which case an outside observer would have less than 200 years until the thing went 200ly.

To the outside observer, they would be time travelling. "Appear to" and "actually" are two very different things. A traveller with a different procession of time will appear to be going faster or slower than they really should.

There are galaxies moving faster than c away from us right now.

Re: A new model for faster-than-light travel that uses conventional physics

#78

Post by asimpletune »

nick_kline wrote: post #57

Instead of negative energy this warp drive idea requires 10^30 more energy than the matter contained in Jupiter, so we aren't quite there ;-). The additional issue is whether something going faster than the speed of light violates causality, like a warp drive. I've never understood how to reconcile causality with the fact of so called 'spooky interaction at a distance'. If it's faster than the speed of light, and you…

You can do things instantaneously, aka spooky action at a distance, you just are forbidden from using that to communicate something useful, so knowable causality is still bound at relativistic speeds. I’m not an expert but this is how I understand it.

Re: A new model for faster-than-light travel that uses conventional physics

#79

Post by hahajk »

jkaplowitz wrote: post #38
rossjudson wrote: post #23

Earlier quoted context omitted.

Which is easier? 1) Faster than light travel. 2) Extend lifetimes so 1) doesn't matter.

I'd rather predict 3) A spaceship large enough and self-sufficient enough that many generations of society can live and die on the spaceship at sub-light speeds. Not the flashy sci-fi solution, but the most likely.

Oh man, take it from someone who has been in the Navy: that’ll have to be one gigantic and well-functioning spaceship.

Re: A new model for faster-than-light travel that uses conventional physics

#80

Post by kittiepryde »

willis936 wrote: post #50
SideburnsOfDoom wrote: post #48

Earlier quoted context omitted.

Nope. Literally any method of getting from A to B faster than light would, has a causality paradox. it does not matter if you cover the miles between FTL, or pop out of a hypothetical wormhole gate: If you end up outside of your own light cone, no matter how, there's a causality paradox.

Warp drives do not violate the speed of causality; they change the geometry of causality.

From wikipedia ----

In both Einstein's theory of special and general relativity, causality means that an effect cannot occur from a cause that is not in the back (past) light cone of that event. Similarly, a cause cannot have an effect outside its front (future) light cone.

---- end wiki

I guess FTL would violate that definition of casuality, but I assume if discovered, we'd just change the definition of casuality and prolly go with a more intuitive, 'cause must preceded effect'(removing the information speed limit); I assume that's the confusion here.

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