6 ms·

> not just mathematically Let's be clear here. Alcubierre's original "warp drive" idea was for super-luminal speeds (faster than light) and required "exotic ma

by acchow 2y ago

> not just mathematically Let's be clear here. Alcubierre's original "warp drive" idea was for super-luminal speeds (faster than light) and required "exotic matter" (negative energy). This new one is for sub-luminal speeds (slower than light). It does not require "exotic matter", but it's hardly a "warp drive"

JumpCrisscross 2y ago
> it's hardly a "warp drive" Why not? From my understanding, to the ship’s occupants, they’d be travelling (EDIT: subjectively) super-luminally. In one lifetime they could go more than 100 ly.
- mr_mitm 2y ago
  That doesn't match any definition of super-luminal that I have ever seen. Super-luminal means faster than light, period.
  - JumpCrisscross 2y ago
    > doesn't match any definition of super-luminal that I have ever seen I didn’t say it’s physically super-luminal. The undefined term is “warp drive.” Given the ship’s occupants would subjectively travel super-luminally, it would seem to tick the boxes for warp. If it worked, you or I could travel to the other side of the galaxy. Hundreds of thousands of years would have elapsed outside the bubble. But we’d be alive.
    - marshray 2y ago
      Typically we think of "speed" as observed from outside the moving [object], but I guess "typically" it doesn't matter. I think it's an interesting point and you're not wrong to say it ticks at least one of boxes. It just doesn't match the concept that people have in mind, so an otherwise interesting discussion ends up rat-holing on semantics.
      - JumpCrisscross 2y ago
        > Typically we think of "speed" as observed from outside the moving Is it? We don’t colloquially consider the Earth’s rotation or revolution. This isn’t a Star Trek warp drive. But dismissing it as “hardly a warp drive” seems categorically wrong.
        mr_mitm 2y ago
        Sub luminal speeds are in an entirely different category than super luminal speeds. It's hard to overstate how different it is, so the original objection is completely appropriate. You can argue about the wording, but what's the point in that? Everyone with half a brain agrees on the facts.
        marshray 2y ago
        I don't recall having considered this point before, though granted I will call half a brain a good day.
        marshray 2y ago
        > We don’t colloquially consider the Earth’s rotation or revolution. Wasn't this choice of reference frame the basis for that whole drama with Galileo, or am I misunderstanding?
        groby_b 2y ago
        We discovered a couple of centuries later that there's more than one reference frame, you can choose, and the choice matters. It's been a pretty interesting development!
    - zmgsabst 2y ago
      I don’t think it’s a “warp drive”. It’s a “warp stasis” bubble or field: you’ve effectively suspended (or considerably slowed) the people inside to preserve them for the future — stasis. I think you’re running into objections because while it is warp technology, it’s not a drive in that it’s not providing atypical propulsion (ie, Star Trek warp drives, Star Wars hyperspace drives, Babylon 5 subspace jump drives, etc). You’re correct that we’re trying to define “warp drive”, but each of “warp” and “drive” are used independently — and your usage of “warp drive” doesn’t respect their independent usage. That you have a 1:1000 slowdown in perceived time to real time as your example suggests at some level you recognize this isn’t a drive. I think warp stasis is a super cool technology all on its own, though.
      - lloeki 2y ago
        > it’s not a drive in that it’s not providing atypical propulsion (ie, Star Trek warp drives, AIUI in Star Trek, Cochrane's "space warp generator" and descendants are essentially the Alcubierre design: I don't seem to understand that the warp bubble provides any propulsion by itself (although grav waves could be surfed) Instead AIUI actual movement is created by a secondary mechanism, which I'm unclear about from a cursory search. Maybe impulse engines? Or maybe those are inefficient/incompatible with warp and it's using a secondary system that comes as a (intentional by design) byproduct of nacelles, like a ramjet engine airplane essentially has two propulsion systems since requires forward speed so you gotta have regular engines.
        throwaway48540 2y ago
        In Star Trek it's the warp bubble doing all the work, impulse engines are sub-FTL.
    - mr_toad 2y ago
      > subjectively travel super-luminally It’s not really subjectively super-luminal either. The travellers could look behind them and see light catching up with them. A signal that left at the same time they left would be to their destination first. Relative to them, light always travels at light speed. What is subjective is not light, but time.
- altruios 2y ago
  Being able to move space around a ship, and being able to move space around a ship faster than the speed of light seem to require orders of magnitude different energies. being in a 'warp bubble' doesn't mean that bubble is traveling at super luminal speeds.
  - JumpCrisscross 2y ago
    > being able to move space around a ship faster than the speed of light seem to require orders of magnitude different energies They require different kinds of energies. Specifically, the latter requires negative energy, something we have no evidence exists. > being in a 'warp bubble' doesn't mean that bubble is traveling at super luminal speeds Nobody claimed as much. The physically-possible warp bubble lets you slow down time. So a 100,000-year journey would feel, to the ship’s occupants (and its structure and computers, et cetera), like possibly months. (You also get the capability to transport people and things forward in time without degradation. Or, I believe, to speed up time inside e.g. a production or computational environment.)
    - altruios 2y ago
      > The physically-possible warp bubble lets you slow down time. that... seems odd to me. without substantial changes in velocity - how does a warp bubble (that's sub-luminal - so relativistic velocities) alter the fabric of space-time so fantastically? It's not moving fast: so where does the time dilation come from?!
      - JumpCrisscross 2y ago
        > not moving fast: so where does the time dilation come from?! I think it’s from shifting momentum?? The paper is far beyond me [1]. But as I understood it, you’re directly modifying space-time with energy instead of using acceleration as a go-between. [1] https://arxiv.org/html/2405.02709v1 https://arxiv.org/html/2405.02709v1
      - ben_w 2y ago
        The mass distribution in the metric can do that; IIRC this was chosen in order to not have time dilation, so I think someone's getting confused (and maybe that someone is me?)
- wyago 2y ago
  The main appeal of FTL is I think the ability to return to where you came from. If 1000 years pass before your return, it would only be superficially the same place. That being said I would think that the defining feature of a warp drive would be that it uses warped spacetime for motion rather than propellant.
  - JumpCrisscross 2y ago
    > main appeal of FTL is I think the ability to return to where you came from If that’s your metric this isn’t the warp drive for you. That hardly means it isn’t a warp drive. The lifetime-lightyear travel boundary for possible experiences would be breached.
  - _w1tm 2y ago
    Can a normal drive even do that?
- hoseja 2y ago
  You can travel arbitrary distances in one lifetime, even with just constant 1g acceleration. It's just that aeons will pass for the outside observers.
- fsmv 2y ago
  That happens with literally any means of travel. Normal rockets do exactly that.

by acchow 2y ago

JumpCrisscross 2y ago

> it's hardly a "warp drive" Why not? From my understanding, to the ship’s occupants, they’d be travelling (EDIT: subjectively) super-luminally. In one lifetime they could go more than 100 ly.

mr_mitm 2y ago
That doesn't match any definition of super-luminal that I have ever seen. Super-luminal means faster than light, period.
- JumpCrisscross 2y ago
  > doesn't match any definition of super-luminal that I have ever seen I didn’t say it’s physically super-luminal. The undefined term is “warp drive.” Given the ship’s occupants would subjectively travel super-luminally, it would seem to tick the boxes for warp. If it worked, you or I could travel to the other side of the galaxy. Hundreds of thousands of years would have elapsed outside the bubble. But we’d be alive.
  - marshray 2y ago
    Typically we think of "speed" as observed from outside the moving [object], but I guess "typically" it doesn't matter. I think it's an interesting point and you're not wrong to say it ticks at least one of boxes. It just doesn't match the concept that people have in mind, so an otherwise interesting discussion ends up rat-holing on semantics.
    - JumpCrisscross 2y ago
      > Typically we think of "speed" as observed from outside the moving Is it? We don’t colloquially consider the Earth’s rotation or revolution. This isn’t a Star Trek warp drive. But dismissing it as “hardly a warp drive” seems categorically wrong.
      - mr_mitm 2y ago
        Sub luminal speeds are in an entirely different category than super luminal speeds. It's hard to overstate how different it is, so the original objection is completely appropriate. You can argue about the wording, but what's the point in that? Everyone with half a brain agrees on the facts.
        marshray 2y ago
        I don't recall having considered this point before, though granted I will call half a brain a good day.
      - marshray 2y ago
        > We don’t colloquially consider the Earth’s rotation or revolution. Wasn't this choice of reference frame the basis for that whole drama with Galileo, or am I misunderstanding?
        groby_b 2y ago
        We discovered a couple of centuries later that there's more than one reference frame, you can choose, and the choice matters. It's been a pretty interesting development!
  - zmgsabst 2y ago
    I don’t think it’s a “warp drive”. It’s a “warp stasis” bubble or field: you’ve effectively suspended (or considerably slowed) the people inside to preserve them for the future — stasis. I think you’re running into objections because while it is warp technology, it’s not a drive in that it’s not providing atypical propulsion (ie, Star Trek warp drives, Star Wars hyperspace drives, Babylon 5 subspace jump drives, etc). You’re correct that we’re trying to define “warp drive”, but each of “warp” and “drive” are used independently — and your usage of “warp drive” doesn’t respect their independent usage. That you have a 1:1000 slowdown in perceived time to real time as your example suggests at some level you recognize this isn’t a drive. I think warp stasis is a super cool technology all on its own, though.
    - lloeki 2y ago
      > it’s not a drive in that it’s not providing atypical propulsion (ie, Star Trek warp drives, AIUI in Star Trek, Cochrane's "space warp generator" and descendants are essentially the Alcubierre design: I don't seem to understand that the warp bubble provides any propulsion by itself (although grav waves could be surfed) Instead AIUI actual movement is created by a secondary mechanism, which I'm unclear about from a cursory search. Maybe impulse engines? Or maybe those are inefficient/incompatible with warp and it's using a secondary system that comes as a (intentional by design) byproduct of nacelles, like a ramjet engine airplane essentially has two propulsion systems since requires forward speed so you gotta have regular engines.
      - throwaway48540 2y ago
        In Star Trek it's the warp bubble doing all the work, impulse engines are sub-FTL.
  - mr_toad 2y ago
    > subjectively travel super-luminally It’s not really subjectively super-luminal either. The travellers could look behind them and see light catching up with them. A signal that left at the same time they left would be to their destination first. Relative to them, light always travels at light speed. What is subjective is not light, but time.
altruios 2y ago
Being able to move space around a ship, and being able to move space around a ship faster than the speed of light seem to require orders of magnitude different energies. being in a 'warp bubble' doesn't mean that bubble is traveling at super luminal speeds.
- JumpCrisscross 2y ago
  > being able to move space around a ship faster than the speed of light seem to require orders of magnitude different energies They require different kinds of energies. Specifically, the latter requires negative energy, something we have no evidence exists. > being in a 'warp bubble' doesn't mean that bubble is traveling at super luminal speeds Nobody claimed as much. The physically-possible warp bubble lets you slow down time. So a 100,000-year journey would feel, to the ship’s occupants (and its structure and computers, et cetera), like possibly months. (You also get the capability to transport people and things forward in time without degradation. Or, I believe, to speed up time inside e.g. a production or computational environment.)
  - altruios 2y ago
    > The physically-possible warp bubble lets you slow down time. that... seems odd to me. without substantial changes in velocity - how does a warp bubble (that's sub-luminal - so relativistic velocities) alter the fabric of space-time so fantastically? It's not moving fast: so where does the time dilation come from?!
    - JumpCrisscross 2y ago
      > not moving fast: so where does the time dilation come from?! I think it’s from shifting momentum?? The paper is far beyond me [1]. But as I understood it, you’re directly modifying space-time with energy instead of using acceleration as a go-between. [1] https://arxiv.org/html/2405.02709v1 https://arxiv.org/html/2405.02709v1
    - ben_w 2y ago
      The mass distribution in the metric can do that; IIRC this was chosen in order to not have time dilation, so I think someone's getting confused (and maybe that someone is me?)
wyago 2y ago
The main appeal of FTL is I think the ability to return to where you came from. If 1000 years pass before your return, it would only be superficially the same place. That being said I would think that the defining feature of a warp drive would be that it uses warped spacetime for motion rather than propellant.
- JumpCrisscross 2y ago
  > main appeal of FTL is I think the ability to return to where you came from If that’s your metric this isn’t the warp drive for you. That hardly means it isn’t a warp drive. The lifetime-lightyear travel boundary for possible experiences would be breached.
- _w1tm 2y ago
  Can a normal drive even do that?
hoseja 2y ago
You can travel arbitrary distances in one lifetime, even with just constant 1g acceleration. It's just that aeons will pass for the outside observers.
fsmv 2y ago
That happens with literally any means of travel. Normal rockets do exactly that.