No, we didn’t accidentally create a warp bubble(bigthink.com)
bigthink.com
No, we didn’t accidentally create a warp bubble
https://bigthink.com/starts-with-a-bang/no-warp-bubble/
104 comments
> 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
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.
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.
Why did you think that? How does dark matter invalidate general relativity?
I think they mean the reverse: since dark matter gives a possible solution to some of the unexpected observations resulting from the current theories, so if the theories later change, they are hoping the dark matter/energy terms will vanish. I likely have about the same physics knowledge as them, so I don’t speak from authority. But dark energy is not just a small fudge factor, so current theories seem unlikely to change by that much. As mentioned in the article, we have some measurements now also consistent with the existence of dark energy being pervasive, not just the appearance of it in theories.
Because I was taught at a young age to assume everyone is fallible and question assumptions, and it seemed an awful lot like a rounding error to me at the time.
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
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
Um, as I understand it, dark matter was not posited by equations but by how observations differed from the the equations. And essentially, this is still the state of things. To wit, the standard model doesn't match observation unless there is this "dark matter" out there. We have no idea what it is. It's just what we call a particular type of ignorance. Current work is either a) assume that the theory is correct and that "dark matter" actually exists so they try to figure out what it is or b) assume that current theory is wrong and so try to come up with a better theory. Or c) a combination.
And essentially the same thing for "dark energy".
And essentially the same thing for "dark energy".
I recall that back in the day my thought was that "Or our model of gravity is just wrong and what we're observing is correct (as in, visible matter is causing this behavior), we just don't understand how gravity works at massive scales because there are variables we aren't taking into account" but honestly it's been so long I forget all the basic info on this.
> Because I was taught at a young age to assume everyone is fallible and question assumptions
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?
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?
"We just don't understand gravity well enough" is one of the top approaches physicists try to solve the mystery about dark matter, but so far it doesn't seem overly likely. Especially galaxies without dark matter [1] are hard to explain without labeling the majority of dark matter as some kind of particle or field.
1: https://www.nasa.gov/feature/goddard/2021/mystery-of-the-gal...
1: https://www.nasa.gov/feature/goddard/2021/mystery-of-the-gal...
Nah, dark matter is the real deal. It's got way more evidence for it, and even the alternatives like MOND (which is something closer to a layman would argue as "maybe we understand the theory wrong") do need dark matter to explain some measurements.
Dark energy, on the other hand...
Dark energy, on the other hand...
Dark matter isn't really a theory, its the name of an observation. Not sure how it can be any more or less legit. The name doesn't try to explain what's happening. Its just describing the weirdness of the observations.
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.
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.
Dark matter is not merely an observation. It is a class of theories to explain that observation. Specifically, if your explanation for the underlying observation is of the form "there is some matter-like stuff with mass that is causing the observed effects through standard G.R. gravity. We haven't otherwised observed it because X", then you have a dark matter theory. Typically X involves week to non-existant interactions through other forces.
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".
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".
Dark matter is not a theory, to be sure. It is a hypothetical.
No its not a hypothetical. The measurements are there. Something unexpected is happening and nobody knows for certain what.
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.
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.
Dark matter first gained notoriety when hypothesized to explain observations of galaxy rotation curves. Since the late 1930's, there have been a number of observations unrelated to galaxy rotation curves that couldn't be explained with contemporary science, so... it's dark matter! A lot that can't be explained got shoved into the dark matter hypothesis.
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.
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.
Can you expand a little bit on how the galaxy rotation curves were explained from standard Newtonian physics? From some Googling it appears that dark matter is still the dominant favourite theory, followed by some kind of MOND.
> dark matter is still the dominant favourite theory, followed by some kind of MOND.
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]
[1] https://www.youtube.com/watch?v=PL0ewiwqoTw&t=6m11s
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]
[1] https://www.youtube.com/watch?v=PL0ewiwqoTw&t=6m11s
Dark matter is a set of observations; we have a dozen or so hypotheses to explain those observations that we cannot yet rule out.
No, dark matter is not a set of observations, but instead it's a hypothetical form of matter, invisible and weakly interacting except with gravity, employed to explain a set of observations.
I don't think the weak interaction is required? Theres both theories for dark matter that include the weak force and that don't iirc?
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 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.
"Weakly interacting " does not mean the Weak Nuclear Force specifically. Dark matter only interacts with ordinary matter through gravity and does not interact through (or is vanishingly weakly interacting through) electro-magnetism, strong nuclear or weak nuclear forces.
The problem with dark matter is that it is a bit too easy to predict where it is. That's why so many people are looking for galaxies without dark matter. We sometimes find them, but I am not sure if there is an instance where we have confirmed that it is not a fluke of observation.
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.
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.
>> 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.
Buzz kill.
Edit- You can find your own ride to the next WorldCon.
Buzz kill.
Edit- You can find your own ride to the next WorldCon.
We want wormholes! We want wormholes!
What do we want?
WORMHOLES!
When do we want them?
NOWYESTERDAYC'THULUTOMORROWUNDEFINED!
WORMHOLES!
When do we want them?
NOWYESTERDAYC'THULUTOMORROWUNDEFINED!
Every solution I've seen for the Alcubierre drive is static.
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.
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.
im a big fan of the idea that anyone who uses FTL with the intent of sending messages back in time has it not work
I think you’re describing this? https://en.m.wikipedia.org/wiki/Novikov_self-consistency_pri...
I've actually thought a lot about this, in particular because I had a dream involving Novikov self-consistency principle. I think the base idea behind self-consistency principle is that it prevents grandfather paradoxes but allows bootstrap paradoxes. In other words, stable time loops are allowed but unstable ones aren't. I submit that it is possible to have meta-stable time loops such that all grandfather paradoxes are ultimately meta-bootstrap paradoxes.
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'.
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'.
[SPOILERS]
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
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
The part I'm referring to specifically is the concept of The Knot, the two timelines that were dependent on time travelers from each other to make the changes that caused them to exist.
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.
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.
> 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.
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.
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How do meta-stable loops work for time travelers visiting themselves in the past? How is it that moments before entering the time machine they don’t remember ever being visited by a future version of themselves?
Because that happened in a different timeline. If A0 was not visited and later A1 and decides to travel back to A0 and visit, that splits the timeline. Eventually some actor in that timeline (or another created by time travel from that timeline) will alter events such that they prevent A1 from visiting A0, restoring the original timeline and acting as the final piece of the meta-stable structure.
But if traveling back in time forks that timeline you don't have to worry about the self-consistency or bootstrap paradox at all, right?
Well, in this hypothetical cosmology I'm operating under the assumption that timelines can't just fork and continue on indefinitely as that requires energy (in the form of the time traveler) to come from an outside source with no connection to this timeline. From the perspective of the new timeline that event has no origin. By forming a meta-stable loop the two timelines are actually just different parts of the same meta-timeline.
Of course, there's no real reason to believe this is a requirement, it's all just an intellectual exercise.
Of course, there's no real reason to believe this is a requirement, it's all just an intellectual exercise.
I think that it would follow you.
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.
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.
That’s a great way to think about it. It reminds me of the Temporal integrity division in the 29th century in Star Trek.
Fermi paradox: advanced civilizations discover time travel and generate paradoxes that erase the timelines that led to their creation
This is explicitly the background for SF author C.J. Cherry's Morgaine Cycle, although the destruction isn't complete and leaves fragments scattered across space and time. (The reaction of a interstellar human civilization to discovering the fragmented network of space-time gates is "shut it all down and bury it".)
That sounds fascinating, I'll read that. C.J. Cherryh is one of the authors I somehow didn't pick up as a child, even though I was reading C.S. Friedman and the like. Maybe it was the covers.
Wow, here's to me thinking I had had an original idea... But that book sounds fascinating, I'll be sure to check it out
I think it was Stephen Baxter who said that if we live in a universe where time travel is possible, then we live in a universe where time travel is not possible, as if it will have happened then everything that can will have happened has already happened.
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Doesn't FTL make time slow for the travelling party? Or does it flip when you velocity is greater than C?
You'd end up returning to your own past if you took a round trip to Alpha Centauri faster than light, so more or less, yeah.
The whole shtick is that nothing is really moving FTL in an Alcubierre drive in the way that breaks the censorship principle, not that any not being able to get out is what's helping the concept.
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.
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.
I think of it as being like one of those trivial "faster-than-light" things like a spot of light.
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.
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.
That's a different underlying cause. Nobody would say that a rail gun that shoots ball bearings at near C breaks FTL just because you turn it.
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.
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.
I don't think you can really use the paths.
Why not? If you can bend space time into the bubble in the first place, why can't you bend it back?
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.
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.
The scientist being discussed in the article didn't even find a new solution.
Article (very end):
---
...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.
Article (very end):
---
...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.
Which is fine for a certain category of paper - in particular this opens the door to explicit measurements and manipulation of the curvature of space at extremely small scales. Further work is required to see if there is something real here or not.
Well,
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.
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.
Journalism about physics has always been like this. The Alcubierre drive is 25 years old, even before that there were widely-publicized discussions of the same kind of idea: invert the equations and come up with interesting results.
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".
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".
Well,
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.
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.
The dynamic sort of of reminds me of the "market for lemons" in that the bad drives out the good.
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.
https://en.wikipedia.org/wiki/The_Market_for_Lemons
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.
https://en.wikipedia.org/wiki/The_Market_for_Lemons
Yeah,
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.
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.
Honestly, I think this has always been how most journalism has been, we're just noticing it more.
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.
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.
It sounds like journalism is achieving its goal - getting more clicks. Like you said, everyone clicked it and read it.
Not sure what the solution is when the only way for these outlets to stay afloat is to get more and more clicks.
Not sure what the solution is when the only way for these outlets to stay afloat is to get more and more clicks.
The market is responding to its incentives and producing an optimized product, line goes up and all is right with the world.
A deeper problem is: how do you create an "open" discussion forum for paid subscription content?
Everyone bemoans ad-financing, but everyone loves aggregators (including Hacker News), and aggregators and paywalls generally don't mix.
Everyone bemoans ad-financing, but everyone loves aggregators (including Hacker News), and aggregators and paywalls generally don't mix.
I think you would want to create a federated members only collection of websites, pay a few hundred influencers to move their base of operations into the collective, and then set and keep the annual subscription so low that the cost isn't prohibitive to 80% of the potential audience.
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.
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.
Journalism is getting worse, because the market has changed/evaporated. It is another race to the bottom.
There are more journalists in prisons than ever before.
Attention is a currency and we are easily distracted.
There are more journalists in prisons than ever before.
Attention is a currency and we are easily distracted.
> There are more journalists in prisons than ever before.
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.
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.
I don't get the excitement for the Alcubierre drive.
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.
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.
It does not need /negative matter/ or energy, though.
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"
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.
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.
Any real warp drive is going to be kind of like setting off a bomb in the middle of a lake and then surfing the water to the center on a jetski, and hoping you can jump off the jetski before you hit the other stuff that is also rushing in with the water on the other side.
> negative mass, something that doesn't exist
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 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.
They explain part of that in the article
> 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.
> 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.
Does it require negative _mass_ or negative space-time compression?
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.
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.
It's not so strange to understand the excitement when you think about how many people would really REALLY like FTL travel to be possible. Not only does it invoke romantic ideas about exploring the stars and lets people dream about becoming captain of their own starship on day, it also helpfully distracts from having to confront the extremely difficult social issues that hinder saving the Earth from it's myriad problems. Without FTL you take all those dreams away, so it's no wonder people are extremely interested in anything that even looks like a "solution".
We don’t know that Dark Matter exists other than we know there is (a lot of) mass missing which is needed to reconcile our observations (or we need to modify our theories around gravity which is where things like MOND come into play).
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.
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.
> It's not like dark matter, something we know exists but don't understand
No one knows that dark matter exists, as it is only hypothesized. It is quite possible that dark matter does not exist.
No one knows that dark matter exists, as it is only hypothesized. It is quite possible that dark matter does not exist.
Tell me you didn’t read the article without telling me you didn’t read the article.
The paper uses the Casimir effect to avoid the need for negative mass.
The paper uses the Casimir effect to avoid the need for negative mass.
Oh boo hoo, we didn’t solve the warp drive in the first attempt? The paper made some interesting but handwavy claims? This is what science actually is—incrementalism.
Unless the guy lied, I say god bless him for finding something relevant to publish towards our multi-galactic future.
Unless the guy lied, I say god bless him for finding something relevant to publish towards our multi-galactic future.
The original paper states:
> 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.
> 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.
Sounds like a normal day in the science journalism. The same case was with the ""earth-like planets"" headlines even though some were unconfirmed and the only data known about them was their orbit, mass to a certain degree and star, which in most cases was small and very active. In the media outlets there weren't any information about the host star and the fact that most of those planets were tidally locked. Besides all of that, they were still calling them earth-like planets.
The reality is that Earth like planets probably exist in great numbers, but we lack the technology to see them since they are small and relatively far from their host star.
Why do you think this is 'probable'? It's certainly possible, no doubts about that, but why do you believe there is a greater than 0.5 probability of it?
A quick Google says that there are an estimated two trillion galaxies, each with an estimated 100 billion stars on average, with an average of 1 planet per star.
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?
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?
I think that's impossible to estimate, at least for some definitions of "Earth-like".
It's impossible to estimate a total number, for sure, but I think it's perfectly reasonable to believe that there's at least 1 other Earth-like planet in the universe.
I only managed a BSc in Physics, although I did get to take grad-level G&R. My stance is the following: I do not care what your proposed method is for FTL, tell me how the paradoxes allowed by closed timelike curves will be resolved. No, just bundling all of it into a black-box general AI "cosmic censor" is not sufficient, that's just an abstraction saying not to worry about it.
Yes, it ruins most of our fun space opera. Oh well.
Yes, it ruins most of our fun space opera. Oh well.
Well, QM allows superposition and entanglement, why not just have you and your grandfather be in an entangled superposition of |alive> and |dead> corresponding to each part of the sequence in the classical eponymous paradox?
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.
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.
A bunch of nonsense thought from someone who reads too much sci-fi:
> 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.
> 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.
Yeah, I found the original hype overblown. The claims made were also for a configuration that was odd, at best. Intuitively, there are any number of geometries that ought to produce greater 'negative energy densities' while being easier to manufacture and test than the sphere-in-a-cylinder one if the proposed effect isn't just a mathematical artifact.
Man.....I wish Feynman were still around today.
Zefram Cochrane will settle all this in 2063.
Dark matter is obviously latent gravity acting across the time axis
I'm not a physicist so take this with a huge grain of salt, but from what I understand, this proposed warp bubble would use the casimir effect. But the casimir effect works by creating a gap so narrow it excludes wavelengths of energy larger than it. So even if the math were all correct and you actually built one of these, wouldn't it be too small to actually send a signal through? And if nothing can fit through it, is there any point?
No, it would be a few micrometers across, hundreds of times larger than features on advanced microchips.
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.
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.
This epidemic of "No, ..." titles needs to be cured.
It's one of the clickbaitiest title formulations around. It works amazingly well on a certain type of mindset.
... Here's why.
:D
:D
Good point, and it looks like something that can easily be scraped out. I'll add it to the list. Thanks!
[deleted]
It seems the warp bubble bubble just burst.
> No, we didn’t accidentally create a warp bubble.
... we consciously did.
... we consciously did.
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...