[Luis Dias]

My bad, I phrased it incorrectly. The point is the object is being observed by a third party near X = 0, and this third party observes the object at X = 1 light minute away at t = 1.1 minutes, indicating the object traveled 1 light minute at 0.1 minutes. This is still on the "possible" side of the equations, for instance if the observer is travelling towards X "final spot" at 0.9 c while the object is travelling at c.

However, if you are near the X "final spot", weirder things start to happen, like seeing the object near you almost a minute before it disappears from its initial location (let's discard the big explosion at the front of the "wave" as predicted).

Now the impossible thing is when the frames are placed in such a way that information is passed through to the past light cone of any one of these objects, creating causal paradoxes. The object could be moving in such a way that for certain frames of reference it could "kill its own past self" (grandfather's paradox), which would be obviously impossible.

[Phantom Hoover]

>astrophysicist who has studied GR says the alcubierre drive isn't completely infeasible
>architect who has 'read some papers' and 'consulted some physicists' says only an idiot would think that

yeah sure

[Luis Dias]

>astrophysicist who has studied GR says the alcubierre drive isn't completely infeasible
>architect who has 'read some papers' and 'consulted some physicists' says only an idiot would think that

yeah sure

And Phantom Hoover ad hominems. I am an architect indeed, but not a stupid one. I did end up 6th place in the national physics Olympiads back in the day, only because I didn't know much of thermodynamics... But yeah I understand your skepticism. Here, take Lubos Mötl criticism:
http://motls.blogspot.pt/2013/07/relativity-bans-faster-than-light-warp.html

[Herra Tohtori]

I would like to point out that if we manage to solve the practical questions (which are not exactly trivial matters) of modifying space-time geometry at will with reasonable energy cost, it would be insanely cool whether Alcubierre Drive as an FTL transportation device works or not.


Things like antigravity, artificial gravity, and reaction massless propulsion systems come to mind*. It would practically be open season for colonizing anything in the Solar System, and it would make it possible to craft large scale, self-sufficient space colonies possibly capable of traveling to nearby star systems. It'd just take a while.

Of course there are other problems associated with subluminal space travel at speeds approacing any appreciable fraction of c. Like hitting all the photons in the way that aren't traveling away from you. And those photons being ridiculously blue-shifted to very high energies. And that's before we look at all the matter particles in the way.

You'd need a pretty large ablative shield for long distance travel.


*Since magic was mentioned earlier on the thread, how do you guys feel about a Bag of Holding?

[The E]

>astrophysicist who has studied GR says the alcubierre drive isn't completely infeasible
>architect who has 'read some papers' and 'consulted some physicists' says only an idiot would think that

yeah sure

And Phantom Hoover ad hominems. I am an architect indeed, but not a stupid one. I did end up 6th place in the national physics Olympiads back in the day, only because I didn't know much of thermodynamics... But yeah I understand your skepticism. Here, take Lubos Mötl criticism:
http://motls.blogspot.pt/2013/07/relativity-bans-faster-than-light-warp.html

Please do not let this thread degenerate into dueling authorities. Luis, get used to the fact that we have absolutely no idea of your credentials in the area, whereas watsisname's are well known. You're skeptical about the Alcubierre drive, and you have sources to back that skepticism up, and that's fine. But posting something that (at least to me) read a lot like a more eloquent version of Aardwolf's uninformed opinions, without any of those sources, doesn't create a favourable impression of your arguments.

[Phantom Hoover]

And Phantom Hoover ad hominems. I am an architect indeed, but not a stupid one. I did end up 6th place in the national physics Olympiads back in the day, only because I didn't know much of thermodynamics...

that doesn't mean ****, unless you're trying to convince me that being good at high school physics gives you an intimate understanding of tensor algebra and differential geometry

Here, take Lubos Mötl criticism:
http://motls.blogspot.pt/2013/07/relativity-bans-faster-than-light-warp.html

motl is so notorious for completely forgetting that his expertise has limits that setting his opinion against any kind of consensus of any experts at all might as well be worthless

oh hey, he's a climate change denialist as well. that where you get your 'expert advice' on that one as well?

e:

Your humble correspondent realizes that many readers are left-wing, anti-string-theory fighters. So they probably smoke marijuana and this is my modest attempt to help them.

[666maslo666]

motl is so notorious for completely forgetting that his expertise has limits that setting his opinion against any kind of consensus of any experts at all might as well be worthless

Except that this topic is where his actual expertise lies. While he certainly has strange opinions in other areas and likes to stir the pot with controversial claims, I have yet to see any evidence that he is a crank or against consencus of the experts when it comes to physics.

[Luis Dias]

Lubos is a very questionable source regarding social, political and global warming issues (although he's not a global warming denier at all, that's just sleazy scumbbaggery that has been thrown at him... well because he was a jackass about it). Lubos' blog is also the very best blog source for theoretical physics in the entire internet.

Your humble correspondent realizes that many readers are left-wing, anti-string-theory fighters. So they probably smoke marijuana and this is my modest attempt to help them.

His humour is also .... not for everyone! (Hey, I'm left wing and I can take all his shenanigans because hey they are irrelevant)

[Bobboau]

yeeeaaaaahhh......................... :/

[The E]

Lubos is a very questionable source regarding social, political and global warming issues (although he's not a global warming denier at all, that's just sleazy scumbbaggery that has been thrown at him... well because he was a jackass about it). Lubos' blog is also the very best blog source for theoretical physics in the entire internet.

Your humble correspondent realizes that many readers are left-wing, anti-string-theory fighters. So they probably smoke marijuana and this is my modest attempt to help them.

His humour is also .... not for everyone! (Hey, I'm left wing and I can take all his shenanigans because hey they are irrelevant)

But for someone who hasn't put in the time to familiarize himself with this person, all of these things do call hid judgment into question. I'm sorry, but I for one can't really take him seriously in anything.

[Phantom Hoover]

Lubos is a very questionable source regarding social, political and global warming issues (although he's not a global warming denier at all, that's just sleazy scumbbaggery that has been thrown at him... well because he was a jackass about it). Lubos' blog is also the very best blog source for theoretical physics in the entire internet.

But what makes him lose all credibility in my eyes is when he asserts that proponents of both the Alcubierre drive and loop quantum gravity are fools who just haven't noticed that their theories ignore basic principles of physics. I know he's a very good theoretical physicist. I also know he's not the only good theoretical physicist.

[666maslo666]

Lubos is a very questionable source regarding social, political and global warming issues (although he's not a global warming denier at all, that's just sleazy scumbbaggery that has been thrown at him... well because he was a jackass about it). Lubos' blog is also the very best blog source for theoretical physics in the entire internet.

But what makes him lose all credibility in my eyes is when he asserts that proponents of both the Alcubierre drive and loop quantum gravity are fools who just haven't noticed that their theories ignore basic principles of physics. I know he's a very good theoretical physicist. I also know he's not the only good theoretical physicist.

Sometimes studying theories that are most likely wrong makes sense to see if you dont stumble upon something interesting anyway, so I would not call them fools (tough some of them may be, not everyone with a degree has to be an expert, and this is a difficult subject). However it is true that those two theories are on the fringe of theoretical physics and not many physicists take them seriously as corresponding to some physical reality. There is probably a reason for that, so I dont see why his aversion towards LQG and aclubierre drive is in any way a negative.

[Luis Dias]

Lubos is a very questionable source regarding social, political and global warming issues (although he's not a global warming denier at all, that's just sleazy scumbbaggery that has been thrown at him... well because he was a jackass about it). Lubos' blog is also the very best blog source for theoretical physics in the entire internet.

But what makes him lose all credibility in my eyes is when he asserts that proponents of both the Alcubierre drive and loop quantum gravity are fools who just haven't noticed that their theories ignore basic principles of physics. I know he's a very good theoretical physicist. I also know he's not the only good theoretical physicist.

I think that's actually a pretty straightforward fair accusation against QLT. Very few people besides Smolin himself takes his pet theory seriously. Most physicists however are just nice chaps and wouldn't say its all crap, because... they are nice people*. Lubos ain't nice.


* but when pressed they will give you strong hints of their displeasure at the theory. It sort of breaks a lot of **** of what we know is true.

[Luis Dias]

But for someone who hasn't put in the time to familiarize himself with this person, all of these things do call hid judgment into question. I'm sorry, but I for one can't really take him seriously in anything.

You realise this is merely a very personal prerrogative right. You're basically saying "I don't know this chap, I can't afford to know and he sounds slimy so I'm not going to, and therefore I won't entertain him at all". It's your prerrogative of course, but it sounds pretty subjective for me. Lubos is indeed an expert on the field and his insights and calls have been right throughout all these years regarding the evolution of physics, string theory, black holes and so on.

[The E]

But for someone who hasn't put in the time to familiarize himself with this person, all of these things do call hid judgment into question. I'm sorry, but I for one can't really take him seriously in anything.

You realise this is merely a very personal prerrogative right. You're basically saying "I don't know this chap, I can't afford to know and he sounds slimy so I'm not going to, and therefore I won't entertain him at all". It's your prerrogative of course, but it sounds pretty subjective for me. Lubos is indeed an expert on the field and his insights and calls have been right throughout all these years regarding the evolution of physics, string theory, black holes and so on.

Of course it's highly subjective. That's why I said that I can't take him seriously

[Luis Dias]

My bad! I would love for him to be wrong on this one.

[Dragon]

But what makes him lose all credibility in my eyes is when he asserts that proponents of both the Alcubierre drive and loop quantum gravity are fools who just haven't noticed that their theories ignore basic principles of physics. I know he's a very good theoretical physicist. I also know he's not the only good theoretical physicist.

Hey, PH is right once! We should probably celebrate that day (at least for those of you who are not celebrating the Moon landing yet).

To be fair, though many theoretical physicists see themselves as the "only good theoretical physicists", especially if their theories clash with the others. This is because a theory needs to be consistent with itself and the experiments - rejecting everything else is a fair game. As such, some scientists might work with a theory that allows Alcubierre drives and other might work with one that doesn't. Both will have solid reasoning behind them, and probably explain the universe equally well as far as the experiments are concerned. Until an actual test rig tells who's right, they'll stay with their theory and also probably consider the other foolish for not taking for granted what they do.

The reason I'm personally on White's side of this debate is that he is actually experimenting with the effect. His results were "inconclusive" last time I checked, but this is the best hope we have - theorizing is nice, but once you get down to actually doing it, you're really answering questions. Theories are just theories, while obviously useful for directing the experimental effort, they need experiments to actually mean anything but a bunch of pretty equations. That's why I went with experimental physics afterall. The skeptics might theorize all day, but if White's machinery says "it works!", and someone else's rig replicates this afterwards (it's important not too get too excited about revolutionary results. A loose cable will make you FTL neutrinos, for instance ), then it's them who'd have to sit down and remake their theories.

[Bobboau]

yeah, White is putting up.

[AdmiralRalwood]

he's not a global warming denier at all

Yes, he prefers the term "climate optimist". Which is to say, he is absolutely a global warming denier.

[Luis Dias]

You're playing with semantics. He always accepted the greenhouse effect. This word "denialist" is just political slimeballing. What he does is a bit different than the usual denialist, he just doesn't believe there's good evidence for the water vapor positive feedback that the more "alarmist" models predict that the atmosphere has. And then he loses his **** whenever some leftist loses his **** in some newspaper or site or whatever, and it's good fun to watch if you have popcorn by your side.