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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

#161

Post by Rule35 »

SideburnsOfDoom wrote: post #123
yellowapple wrote: post #117

Earlier quoted context omitted.

> If I can travel FTL, I can find a frame of reference where T2 How? Sure, it's possible that the light from an event happening at T2 arrives before the light from an event happening at T1, but that says nothing about when those events actually happened - just like how if we hear one lightning strike before another, that doesn't mean the one we heard first actually happened first. That is: this notion that all superl…

> How? > this notion that all superluminal travel somehow magically necessitates the possibility of backwards time travel doesn't seem to be logically sound. There is literally decades worth of physics that answers your how, and explains the soundness of it, I would urge you to study the subject in well, any depth at all before naively dismissing it as "unsound". I mean, who's more likely wrong: Physics since Einstei…

Hey. Uh, this flame war you're having is all you. The rules clearly say not to engage with trolls, not to attempt to fight them to a standstill.

That said, I don't think yellowapple is trolling, I this he's saying "that article isn't accessible at my level".

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

#162

Post by SideburnsOfDoom »

yellowapple wrote: post #158
SideburnsOfDoom wrote: post #150

Earlier quoted context omitted.

Can recommend again that you turn to books on this subject; Posting long rants on the internets won't get you anything. You're clearly not learning, and neither are you intellectually impressing anyone. > get an object from A to B without any actual movement from A to B This sentence is pure gibberish: You got from A to B in time T ... but you also didn't get from A to B in time T? Ok, whatever. You're splitting hair…

Welp, looks like this turned sour again. Whoops! But hey, I tried, I guess. > Can recommend again that you turn to books on this subject Got any recommendations? In fact, I asked you this already, the last time you dickishly suggested I go read books (as if I haven't done that already). > This sentence is pure gibberish Then go read Alcubierre's paper[1]. Expanding spacetime on one side of an object and contracting i…

You're _not_ trying. The "Alcubierre's Expanding spacetime" wheeze isn't anything that wasn't covered in literally my first comment

https://news.ycombinator.com/item?id=26614286

and later ones https://news.ycombinator.com/item?id=26619504

Boring circular drivel, and when you're directed somewhere more fruitful, you think it's "dickish". - I'm sorry that I don't have a scientifically current recommendation and I wouldn't presume to offer an outdated one. If you want recommendations list, google or amazon can help you. Whichever way you approach it, if you are really interested in understanding, you're going to have to do some of the work yourself, and you can't expect to be spoon-fed. That would be dickish.

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

#163

Post by bitdizzy »

yellowapple wrote: post #160
bitdizzy wrote: post #154

Earlier quoted context omitted.

So the thing that paper does is it assumes you can make warp bubbles in any reference frame. The original paper makes one warp bubble and this doesn't lead to anything paradoxical. But if I can make two warp bubbles in two different frames, I can make a round trip that arrives before it starts. So you need to violate special relativity in a global way to avoid these issues. You have to have a spacetime where only cer…

> I apologize for being a bit impatient before, these issues are subtle. No worries, and thanks again :) > But if I can make two warp bubbles in two different frames, I can make a round trip that arrives before it starts. Even for the metric as Alcubierre describes? Or for one that's modified per Everett? Now that I'm rereading the Everett paper, I'm not really sure where he's getting his "Lorentz boost"; if there's…

A lorentz boost is just a change of perspective. Let's say you have a bubble that is at rest with respect to your reference frame. Well, someone flying by your solar system has just as valid a reference frame as you and they see the bubble moving with respect to them. The relation between their point of view and yours is described by a lorentz boost. Same physical situation, different perspective.

Now, if special relativity holds in the large then there is no reason why they can't also construct a warp bubble. Relative to you and your bubble that bubble is in motion. Since this is allowed, we can construct a closed timelike curve with two judiciously chosen bubbles.

> Which the universe kinda already does, no?

The expansion of the universe does violate special relativity but not in a way that protects warp geometry from creating paradoxes. The kind of violation you would need would distinguish between frames of reference that SR says are equivalent.

> And further, doesn't special relativity already only hold in cases with low gravitational potential - so i.e. not in a gravitational field?

Special relativity holds well enough in most situations that the same argument applies even if you accounted for general relativity except near extreme situations like black holes

Warp drives are not permitted by any deviation from special relativity. You need specific contrived geometries of the entire universe that don't match up with what we know about it.

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

#164

Post by SideburnsOfDoom »

bitdizzy wrote: post #163
yellowapple wrote: post #160

Earlier quoted context omitted.

> I apologize for being a bit impatient before, these issues are subtle. No worries, and thanks again :) > But if I can make two warp bubbles in two different frames, I can make a round trip that arrives before it starts. Even for the metric as Alcubierre describes? Or for one that's modified per Everett? Now that I'm rereading the Everett paper, I'm not really sure where he's getting his "Lorentz boost"; if there's…

A lorentz boost is just a change of perspective. Let's say you have a bubble that is at rest with respect to your reference frame. Well, someone flying by your solar system has just as valid a reference frame as you and they see the bubble moving with respect to them. The relation between their point of view and yours is described by a lorentz boost. Same physical situation, different perspective. Now, if special rel…

> The expansion of the universe does violate special relativity

I am curious as to how?

If, we take as axiomatic that there is no such thing as "an object in motion", only "an object in motion with respect to another object", i.e. motion is not a property of an object, but a relation between two objects.

And that since it's 4.3 light-years to Alpha Centauri, therefor a cause (e.g. a radio wave) sent from Earth today cannot have an effect (e.g. an Astronomer writes a paper about it) at Alpha Centauri for 4.3 years, and vice versa. There is 4.3 years of "Absolute elsewhere" to get through first where there is no possible cause-and-effect relation between events. At the other side of our galaxy it's around 100 000 years. And further out, objects are not just far, but receding from us (or us from them, equivalently)

Assuming an unbounded and expanding universe, for very distant parts of the universe receding from us at lightspeed (or speeds faster than light?) and us from them, equivalently. So lightspeed signals from there never reach us, by definition? That part is is utterly unobservable, permanently Absolute elsewhere. The universe's observable edge is a slowed-down red-shift that trails off into the unobservable. In other words, the at no time in the future will those signals have an effect on Earth, or us on them. So, they can't have an effect in our future, let alone our past. No impact to causality at all?

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

#165

Post by kyriakos »

seg_lol wrote: post #103
creamytaco wrote: post #70

Earlier quoted context omitted.

Science is (a lot less) powerful than religion. Indoctrination taken to religious levels, in a confined and controlled environment, would be more than enough to propagate programming for hundreds if not thousands of years.

So we design cult missiles and send that at other star systems, sounds like a pretty hostile weapon.

Human cult is still human. If we aim to continue our species it may be what we need. Say a civilization is built at the destination we can assume it will go through its own dark ages at some point before a renaissance.

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

#166

Post by bitdizzy »

SideburnsOfDoom wrote: post #164
bitdizzy wrote: post #163

Earlier quoted context omitted.

A lorentz boost is just a change of perspective. Let's say you have a bubble that is at rest with respect to your reference frame. Well, someone flying by your solar system has just as valid a reference frame as you and they see the bubble moving with respect to them. The relation between their point of view and yours is described by a lorentz boost. Same physical situation, different perspective. Now, if special rel…

> The expansion of the universe does violate special relativity I am curious as to how? If, we take as axiomatic that there is no such thing as "an object in motion", only "an object in motion with respect to another object", i.e. motion is not a property of an object, but a relation between two objects. And that since it's 4.3 light-years to Alpha Centauri, therefor a cause (e.g. a radio wave) sent from Earth today…

> I am curious as to how?

Special relativity describes a flat lorentzian manifold. The uniform expansion of the universe implies that the curvature of spacetime is slightly negative.

Special relativity is not simply a theory of causality but specifically of the geometry of spacetime. From this theory you can derive predictions about specific phenomena, like causality.

But that doesn't mean other spacetime geometries don't share properties with flat minkowski spacetime. Just not all properties. For example there is no cosmological horizon in minkowksi spacetime but there is for our universe.

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

#167

Post by SideburnsOfDoom »

bitdizzy wrote: post #166
SideburnsOfDoom wrote: post #164

Earlier quoted context omitted.

> The expansion of the universe does violate special relativity I am curious as to how? If, we take as axiomatic that there is no such thing as "an object in motion", only "an object in motion with respect to another object", i.e. motion is not a property of an object, but a relation between two objects. And that since it's 4.3 light-years to Alpha Centauri, therefor a cause (e.g. a radio wave) sent from Earth today…

> I am curious as to how? Special relativity describes a flat lorentzian manifold. The uniform expansion of the universe implies that the curvature of spacetime is slightly negative. Special relativity is not simply a theory of causality but specifically of the geometry of spacetime. From this theory you can derive predictions about specific phenomena, like causality. But that doesn't mean other spacetime geometries…

> Cosmological horizon

https://en.wikipedia.org/wiki/Cosmological_horizon

Oh, that's the term that I was groping for. Thanks!

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

#168

Post by Doxin »

vanderZwan wrote: post #153
Doxin wrote: post #152

Earlier quoted context omitted.

As far as I've gleamed from watching star trek the "warp core" is really just a power plant. It's the nacelles doing the propelling.

Yeah but doesn't the warp core also require "dilithium crystals" to run? But still, fair point: that does suggest "warp core" is a bit of a misnomer. Then again, we all know the difficulty of naming things properly ;)

Well I suppose if a warp core is the only reactor powerful enough to produce enough of the right kind of power to power the nacelles it's probably still an apt name. I mean there's plenty of times in the series where the warp core stops working, but all the lights are still on. So presumably there's a primary power generator somewhere for everything that isn't warp drive.
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