No, we didn’t accidentally create a warp bubble
bigthink.com
bigthink.com
However, we know those theories don't go together very well, and I would certainly consider trying to create "warp bubbles" as an extremal condition for the combination of the two, so we shouldn't take such a combination too seriously. Not necessarily unseriously simply on the basis of this one thing... I believe Hawking's initial computations for black hole radiation plays a bit fast and loose with this distinction, albeit in a somewhat principled way, so it's not an immediate disqualifier. But it's definitely a Spock-eyebrow-raise and a "hmmmmm?"
Personally, I wouldn't be surprised that when we get the real theory of quantum gravity, if we ever do, that a lot of these "oh, look at this solution for general relativity!" obscurities go away, like wormholes, cosmic strings, the place in the Kerr metric that seems to lead to a new universe or some other exotic thing [1], singularities in general, and quite possibly, warp bubbles and other crazy solutions. This is the Occam's Razor, most parsimonious solution to the question "why is it that we look out in the universe and the craziest general relativity thing we see is black holes?"... the rest of these things are artifacts of the approximation that is general relativity.
[1]: https://en.wikipedia.org/wiki/Kerr_metric#Kerr_black_holes_a...
In particular, I've thought dark matter is in this category of "bad theory rounding error" since I learned about general relativity and quantum mechanics in high school.
As people have mentioned, there is apparently now more substantial support for it, but back then it was posited based on equations only, and seemed a lot more like trying to explain away a theory not fully matching reality
And essentially the same thing for "dark energy".
It is generally a good idea to have some familiarity (or better still, expertise) with a topic and knowing what the actual assumptions are before questioning them.
I was very surprised that you had that kind of expertise in high school. For eg, did you know about the electromagnetic field theory and Maxwell's introduction/invention of displacement current in high school? Or reimannian geometry?
1: https://www.nasa.gov/feature/goddard/2021/mystery-of-the-gal...
Dark energy, on the other hand...
One thing that annoys me is the common description of dark matter as a single coherent theory of extra matter that can't be detected. Even wikipedia makes this mistake at the very beginning. But there are a lot of theories that try to explain it. None of which actually work yet. Once a theory that stands up is formed then the name will change.
The only thing we know for sure is that we can define a field of masses that corrects for the difference between the observed behaviour and predicted behaviour of the cosmos vis a vis general relativity.
The problem is someone picked the misleading name "Dark Matter" and then pop science, and actual scientists talking to laymen did the massive disservice of wording the explanation in such a way as to make it sound like there is a real theory that proposes there is some matter that interacts with gravity yet is invisible and undetectable in literally every other way called dark matter.
I only learned the distinction in college when another student pointed out that dark matter as described was unscientific because it was an unfalsifiable, not to mention generally useless anyways. That led to patient explanation that it wasn't a hypothesis or theory and it was just what they called the observations. Would have been nice if anyone had bothered to start with that.
There are a lot of hypothesis about what it really is. Neutrinos, WIMPS, SIMPS (heh), MOND etc etc.
Personally I lean towards the got gravity wrong bit although not any specific explanation. I'm not a physicist but history and logic would suggest that while relativity is a pretty good explanation its far from complete. And I see no reason why forces necessarily have to work the same on the small scale and grand.
Once enough things that couldn't be explained were lumped into dark matter, it became a part of the science paradigm. Once you understand paradigms, you'll understand why it seems like all of science is convinced that dark matter exists. But this is not actually the case, it is merely that dark matter has not been disproven. The luminiferous ether, another famous hypothesis, was once also embedded in the paradigm of science, and it only took one experiment to prove it did not exist to dislodge it. Dark matter is going to stick around until disproven, that is the nature of paradigms.
As it turns out, dark matter is absolutely unnecessary to explain galaxy rotation curves, which can be simply explained and demonstrated accurately with a toy model without needing anything remotely like dark matter nor even Modified Newtonian Dynamics, but just the ordinary Newtonian physics. I suspect as time goes on, more and more of the stuff unrelated to each other that dark matter is employed to explain will be explained without the need for dark matter.
There are no direct observations of dark matter, none whatsoever. And by definition, there never will be. It can't be seen! What there is instead are observations that don't have immediate explanations, so dark matter is hypothesized to explain it. That makes dark matter a hypothesis.
Yes, this is a precise problem with scientific paradigms!
> Can you expand a little bit on how the galaxy rotation curves were explained from standard Newtonian physics?
Maybe I exaggerated a bit as with these scales surely Relativity is involved. No, I think it's just tidal forces, no need for dark matter. Fundamentally, I think, it was unrecognized human error that became foundational, massively built upon, such that even though the original pivotal need for dark matter is eliminated, dark matter is still successful for other models.
Galaxy rotation curves were originally observed in a galaxy in isolation, without consideration of nearby galaxies, creating the illusion of gravitational isolation. When accounting for nearby galaxies tidal effects, rotation curves are neatly explained. [1]
If your explanation for the observation involves saying "General Relativity is wrong", or positing the modification or addition of some other force, it may account for the observation behind dark matter; it may even be correct; but it is not a dark matter theory.
Assuming some dark matter theory is proven correct, we will probably stop calling it dark matter when it is discovered. Although we still call nuclearly bound protons and neutrons with electrically bound electrons an "atom", even though we have since disproven the hypothesis that such objects are atomic.
If the answer ends up not being a dark matter theory, we will probably just call it "gravity".
The reason why it is a problem is that if you can reliably predict where dark matter is, then you can turn these predictions into equations and get away with dark matter as a form of matter. That's the idea behind modified gravity.
Buzz kill.
Edit- You can find your own ride to the next WorldCon.
WORMHOLES!
When do we want them?
NOWYESTERDAYC'THULUTOMORROWUNDEFINED!
To really make it work you have to start out in normal flat space, turn it on, and then turn it off.
You have to do this without being killed. I suspect you'd face hazards like the hazards you'd have falling into a black hole. (Personally I think you die when crossing the event horizon and never make it to the classical singularity, not just because you got killed at the event horizon, but there is nothing that looks like the classical singularity.)
I think the Alcubierre drive doesn't violate the censorship principle because practically it doesn't create closed timelike curves. You can't see outside, you can't get into it, you can't get around it. You might be moving faster than light in some sense but you can't interact with the universe and communicate messages from here to there.
Assume that if time travel is possible, then changing the course of events must be also be possible just as directing future events by our decisions in the present is. If one goes back in time and kills their own grandfather, they have altered the future such that they are never born in order to time travel in the first place, a grandfather paradox. However, since time travel must have existed in order for this situation to occur, then undoubtedly someone else at some future date within this timeline will seek to change history as well. To keep this scenario simple, imagine that this person travels back in order to kill you before you are able to kill your own grandfather, thus restoring your original timeline in which you travel back to kill your own grandfather. This is a meta-stable time loop employing a meta-bootstrap paradox. Each timeline exists and is dependant on time travel from the other. Arbitrarily complex structures are possible involving arbitrarily many timelines, which in an infinite meta-time universe suggests the possibility that all time travel must resolve in this way.
I came up with this years ago, but have only ever seen something like it explored once: in the TV show 'Dark'.
Doraemon, a Japanese children's cartoon (1970s to 1990s), created by Fujiko F Fujio, who is actually very well-versed in physics and science, has used something like this as a plot point in several different chapters/episodes and some movies. It doesn't actively call them "meta-stable time loops", since its target audience is children, but the idea and concept is there. Growing up watching and reading this series, I've learned more and more from it as I rewatch/reread old chapters/episodes, every time. I absolutely love it.
Of course, there's no real reason to believe this is a requirement, it's all just an intellectual exercise.
Past you would have no advance memory of meeting future you until future you went back in time and met past you, at which point you would have memories from both points being produced at the same time.
If I remember correctly Dark to some extent relied on time travel to have time travel in the first place, i.e. Claudia Tiedemann needed to go back in time to hand H. G. Tannhaus the blueprints for the time machine that she used to go back in time with. That, in one of the alternate timelines- in the original timeline Tannhaus presumably made a time machine from scratch, or there would be no alternative timelines. In the end Jonas Kahnwald and Martha Nielsen go back in time to alter the course of the original timeline, thus eliminating their own. This is much like you say, except that in the end the original timeline is restored to the point before any time travel could happen, or had a reason to happen. And maybe that's a simpler way to eliminate any paradoxes: no time travel allowed [edit: yeah, sorry, that's Novikov].
Sic mundus creatus est :P
Of course the show ended with eliminating The Knott, leaving the only paradox as being where two people suddenly materialized in the middle of the road from to warn about a bridge being out before just as mysteriously ceasing to exist.
There's no underlying reference frame beneath space time itself, so warping space time like this just creates shortcuts. The time element of the vector is still positive for all possible particles, so no closed timelike curves.
For an example that can be seen naturally, it's thought that the galaxies on the edge of the observable universe are moving away from us faster than C because of the expansion of the universe and it's warping of space time. The same math works just fine with them moving faster than C towards us if the universe were shrinking.
You can easily swing a laser pointer fast enough that the beam would crosses Earth's Moon faster than light. Information is moving outwards, not sideways, so that speed doesn't matter.
This is more that space time isn't euclidean. You can see this in how gravitational lensing can create longer straight line paths between two points. Just because you could send light down one pathway and it ends up later than something moving less than C, doesn't mean that you went FTL in a way that breaks causality. An Alcubierre drive is 'just' dynamically modifying the shape of space time to make more useful pathways.
The main issue I've heard with 'popping' the bubble isn't that you cut yourself off from the rest of space permanently, it's that there's a collection of everything that would have been along your path time dilated sitting right at the edge of the bubble that flies into the bubble all at once and is pretty nasty for anything in the bubble.
Article (very end):
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...there’s an enormous difference between what teams working on Casimir cavities do experimentally and the numerical calculations performed in this paper. That’s right: This isn’t an experimental paper, but rather a theoretical paper, one with a suspiciously low number (zero) of theoretical physicists on it. The paper relies on the dynamic vacuum model — a model typically applicable to single atoms — to model the energy density throughout space that would be generated by this cavity. They then use another technique, worldline numerics, to assess how the vacuum changes in response to the custom Casimir cavity.
And then it gets shady. “Where’s my warp bubble?” They didn’t make one. In fact, they didn’t calculate one, either. All they did was show that the three-dimensional energy density generated by this cavity displayed some qualitative correlations with the energy density field required by the Alcubierre drive. They don’t match in a quantitative sense; they were not generated experimentally, but only calculated numerically; and most importantly, they are restricted to microscopic scales and extremely low energy densities. There’s a lot of speculation and conjecture, and all of it is unproven.
I think journalism is getting worse as the years go by. Like everybody else I noticed the title and clicked on it a few days ago. Reading the paper revealed that the team was simply interpreting/speculating what the math was showing about some hypothetical energy density structures.
Of course the sensationalized title propagated all over the net ignoring the facts.
Not really quite the same though. The question is what the production function for articles looks like from the publisher/journalist perspective. If it's easier to produce clickbait articles than "real" articles then I think this effect is what we see in the market for news. But from another angle, it seems more labor intensive for a journalist to spin a weak finding into a strong finding than to simply report an exciting finding directly.
It makes me sad to think that I contribute to this process. I have to admit... that I probably do read alot of those clickbait articles giving them more views.
It makes me even more sad when I think about the platforms that are removing the ability to downvote incorrect/misleading information.
Not sure what the solution is when the only way for these outlets to stay afloat is to get more and more clicks.
Everyone bemoans ad-financing, but everyone loves aggregators (including Hacker News), and aggregators and paywalls generally don't mix.
Ad free reddit, youtube, twitter, and the like, all populated only by people who paid to be there and not an ad or corporate sponsor in site except within a walled garden of delights (for the influencers)?
I'd pay $10 a month for that.
But to be fair and I think to support your point, the bastions of so-called 'real' journalism do seem to have gotten fewer and fewer.
The realities of space travel are kind of grim: months to visit even nearby uninhabitable planets and decades to get anywhere interesting. Relativity has always been a huge and ever-increasing impediment to that, and the ways in which it is have percolated out. There's also the demand for hard science fiction with space battles (I personally am a fan!) that similarly runs aground on "you can't have a galactic empire where it takes a hundred years to reach the next province over".
So there's lots of demand for "hey this thing makes FTL travel possible" and not as much demand for "scientists publish paper but everything still sucks".
About a week ago this topic was widely in the news under variations of the title:
"DARPA and NASA Scientists Accidentally Create Warp Bubble"
That's the context of my response here in this thread. I am not sure if everyone reading this thread knows that. The new title "No, we didn't accidentally create a warp bubble" was the NASA engineer attempting to fix the misinformation generated by the journalists.
Absolutely agree with you about physics journalism. I enjoy science fiction books too, I have no problem with the theoretical FTL topic.
There are more journalists in prisons than ever before.
Attention is a currency and we are easily distracted.
In Russia or China, I can believe this. But in the USA and most of Europe, I'm going to need a citation before I believe that.
It requires negative mass, something that doesn't exist. (It's not like dark matter, something we know exists but don't understand -- it is something that we have no evidence for its existence at all.)
I feel like they were just playing with models, entered a nonsensical value (negative value for mass), and discovered a warp drive. If you're going to do that, just enter negative time and invent time travel while you're at it.
We don’t know this. And this isn’t a “can’t prove a negative” argument. The origin of mass is frontier physics.
More directly, one can explore why negative mass is needed, and whether there are other phenomena that produce that effect. Worst case: the math is interesting.
We know gravity waves exist, so space time can oscillate between 0 and N where N is positive right? Are we so sure there is not a -N < 0 < N?
Not even close to an expert in this stuff.
> Today, however, it’s recognized that what’s needed isn’t necessarily negative mass or negative energy; that was simply the way that Alcubierre recognized one could induce the needed “opposite type” of curvature to space from what normal mass or energy causes.
There's other options, and also we aren't 100% certain negative mass/energy can't exist (but probably not...)
Edit: changed my tone because I was being a snarky jerk.
What is needed, in the original, non-scammer-friendly version by Alcubierre is /something/ that can push spacetime in the opposite direction that mass and energy do.
At least the original Alcubierre solution, he basically lays out the mechanism and says, paraphrasing: "hey, the numbers do work out. We just need something that doesn't make sense, or something that makes /the thing/ happen"
We see then that, just as it happens with wormholes, one needs exotic matter to travel faster than the speed of light.
However, even if one believes that exotic matter is forbidden classically, it is well known that quantum field theory permits the existence ofregions with negative
energy densities in some special circumstances (as, for example, inthe Casimir effect [4]).
The need of exotic matter therefore doesn’t necessarily eliminate the possibility of using a spacetime distortion like the one described above for hyper-fast
interstellar travel.
The excitement here is partly due to the fact that this is both a trekkie thing and one that was previously not even supposed to numerically make sense.
It's likely this "not requiring any specific fringe-physics thing" is what is causing the idea to catch on and continue to be ellaborated, because having specificed this mechanics well enough, then maybe and only maybe it might be possible to cause at least an analogue of it to exist and that'd be awesome.
No one knows that dark matter exists, as it is only hypothesized. It is quite possible that dark matter does not exist.
Dark Matter is just a placeholder term for that missing mass with a lot of candidates ranging from normal (baryonic) matter to more and more exotic things.
Negative mass does not contradict existing theories such as the standard model in fact it’s somewhat built into them.
But overall yes we haven’t found any evidence of it actually existing we know that anti matter (probably one of the best candidates for it) has positive inertial mass from experimentation we didn’t experimentally proven that it’s gravitational mass is also positive but it most likely is as if it isn’t it would be probably the most interesting discovery since it would violate the equivalence principle.
In general you’ll find people getting excited about any possibility for an FTL means of transport since otherwise we are unlikely to ever be able to explore the universe with anything other than telescopes.
I fore one hope that we do find a way around the pesky speed limit because if not it seems that it’s quite a bit of waste of space otherwise.
The paper uses the Casimir effect to avoid the need for negative mass.
Unless the guy lied, I say god bless him for finding something relevant to publish towards our multi-galactic future.
> This qualitative correlation would suggest that chip-scale experiments might be explored to attempt to measure tiny signatures illustrative of the presence of the conjectured phenomenon: a real, albeit humble, warp bubble.
The key word here is "conjectured". He didn't say he created a warp bubble.
I'm okay with publishing conjectures. If you think there's something interesting, let the world know.
Disclaimer: I'm not a scientist by any means.
That means there's an estimated 200 trillion billion planets.
Don't you think it's incredibly improbable that our Earth is the only one?
Yes, it ruins most of our fun space opera. Oh well.
> https://news.ycombinator.com/item?id=29569437
In other words, it's perfectly ok to change the past and the universe doesn't so much self-censor as timelines always ultimately loop in some kind of meta-time back into each other.
Another way to think of it is that it self-censors in the way that a delayed choice quantum eraser experiment does. The timelines which do not ultimately form part of a stable meta-loop structure destructively interfere with each other.
Feel free to point out all the ways in which this is nonsense by the way. I love this sort of education through correction of ignorant armchair supposition.
That said, I read a plausible claim that a CTC would have an unstable buildup of energy in the form of the wavefunctions of virtual particles self-reinforcing, so I suspect it’s more likely that trying to build a time machine would instead result in unbounded energy, and that being a possibility is generally considered a sign that somebody made a mistake.
And if it is effectively a warp bubble, it wouldn’t have any immediate useful application, but for teasing you could send electrons or photons through it and measure effects. This is not a wormhole, the likely effect is either nothing or a slight signal timing change.
:D
... we consciously did.