Inflation happened during the first tiniest fractions of a second post big bang. No telescope is going to make direct observations of the inflationary period so I'm not sure what you mean by this.
I'm referring to the earliest era of transparent space, when conventional matter supposedly coalesced. If we look back to that period and still see red-shifted mature galaxies then something is very wrong with the current models. I'm under the impression that we don't have good observations of the period 375k-400M years after inflation and that infant galaxy observations have not been confirmed.
The earliest moment of transparent space is the CMB. I know JWST can't detect Pop3 stars, but is there even expectations that it could detect proto galaxies with those stars? I thought it was still much later, like the early Pop2 generation.
> No telescope is going to make direct observations of the inflationary period so I'm not sure what you mean by this.
Isn’t this an engineering problem and what we are attempting to do with gravitational wave detectors?
I know at one time it was believed gravitational waves were detected that provided direct evidence for inflationary theory but then the data was determined to be dust from the Milky Way. I thought this was still one of the major ongoing efforts in gravitational wave detection, was this ruled out?
This isn't just an engineering problem. Photons couldn't move around for the first 380K years or so. Space was nearly uniform, hot, and dense. The CMB is literally the heat wave left over from the point where the heavy soup thinned out just enough to allow photons to fly away in all directions.
The gravitational waves from those events would have already warped space, and the ones just now reaching us would be from the edge of the observable universe, and so too weak for any instruments we could conceivably build in the next few decades. Not that we shouldn't try, mind you. There are new frontiers in quasimatter and time crystals that could yield far more accurate gravitational wave detectors.
Also fascinating would be to attempt to decipher the deformations left in the metric already. There are some theories that basically say gravity waves permanently "crumple" spacetime, and it might be possible to read signatures of such events if this is so.
> There are some theories that basically say gravity waves permanently "crumple" spacetime
Does that mean those theories predict you can achieve permanent gravitational effects (locally) without any matter or energy to cause it? Wouldn't that violate relativity?
No, you still need something to create the gravity waves. The idea is that once a gravity wave has passed through a region of spacetime it leaves a permanent deformation. In the case of a detector like LIGO this means rather than the mirrors wobbling relative to each other and then settling down to their previous configuration, in fact they are left in a (very slightly) permanently altered configuration. The difference is probably way too small to detect though, for now anyway.
I understand what you're writing (I think), but I don't think I understand how the implications would be consistent with relativity unfortunately. I thought gravity is (supposedly) caused by the deformation of space. If your space isn't flat, then you're going to experience acceleration (aka gravity) at that point, right? And if this deformation is permanent, then its source is already long gone - meaning that when you look down to see why you're falling, you see that there's no matter or energy causing you to fall. Which seems weird to me because I thought you need some kind of matter/energy to cause space to curve (and hence feel gravity/acceleration). Is that not the case?
These distortions are predicted by relativity. They’re a consequence of it, not a problem with it.
Objects influenced by a gravitational field don’t feel an acceleration. Astronauts in orbit round the earth don’t feel anything even though they are going round in circles. It’s only when something gets in the way that you feel an acceleration from the thing stopping your trajectory, like the surface of the earth.
The distortions were talking about are created by a mass though, the mass that created the original gravity wave.
You don't feel acceleration either, you feel the normal force of an object against you. If you're in freefall you feel nothing (or really, you do feel the absence of a normal force you're used to).
However, that's not what the comment you replied to was saying. Gravity doesn't apply a force at all! A force is when your worldline gets pushed around, but an object undergoing gravity is actually still going "straight", it's spacetime that's deformed.
One problem is that a lot of simplifications get layered on in pop science explanations of relativity, or actually deep science of any kind. We often talk about the force of gravity, but the thing is it's actually not a force, or even a field, in the same way as other forces and fields in physics.
This is why Einstein is so revered in Physics. He didn't just explain a force, otherwise why would he be given pre-eminence over Maxwell who explained electromagnetism? Relativity is something else completely.
Here's a really good explanation of what's actually going on when gravity influences an object. Hold on to your chair.
> it's actually not a force, or even a field, in the same way as other forces and fields in physics
That's why (for anyone who's still reading this old thread) gravity is treated separately from the other three "fundamental" forces. We can explain pretty much everything in physics with the tools of Quantum Field Theory, even if there's still some gaps, but relativity is a whole other ballgame. Not only is it totally resistant to the mathematical techniques (quantum operations are linear, relativity is very much not, to name just one issue), but it's sort of unclear what QFT looks like without spacetime as a stage to act on. If the properties of spacetime emerge from some simpler, presumably more quantum, system, we have next to no idea how.
The deformations in spacetime are permanent (hypothetically). The mirrors in LIGO, however, are subject to all the other various things in the environment tugging on them. They return to a state of alignment because of their environment (local gravitational forces, etc.) This "noise" would prevent a detector like LIGO from seeing the permanent changes to spacetime.
Yes gravitational wave telescopes is commonly used along with gravitational wave detectors, gravitational wave instruments and gravitational wave observatories.
Well, I guess measurements of the early universe (100-250 million years after the big bang) can test predictions made by models of the inflationary period.
Measurements of pretty much any time in the universe can test predictions made by models of the early universe. One of the main reasons we think there was inflation is from late time (near today) observations of matter density (see https://en.wikipedia.org/wiki/Flatness_problem).
I worked with someone (this is in astronomy) who said that papers in nature were the most likely to be wrong. They are in nature because they have a dramatic (new/unexpected) result. One good reason for a new/unexpected result is a mistake somewhere.
Edit: I'm not saying anything about this paper. I know nothing about this. Just a meta comment that, in really hard to get published in journals, there might be a bi-modality of papers. Really important and really wrong :)
This is correct. Think of nature as a journal that publishes papers with a high rate of false positives (claims that turn out to be untrue) on purpose,to intentionally stimulate the state of the art of science.
I have actively ignored Nature and Science papers for my entire career (with the exception of my one Nature publication, and W&C 1953 of course).
Small stars live a very long time. A star of the mass of our sun has a lifespan of ~10 billion years which gets you almost back to the beginning of the universe (~13 billion). This star is smaller (0.8 solar masses), so it can live even longer, so we don't need to look at distant objects to see early, low mass stars.
The other issue is that we just can't see individual stars at cosmological distances except in incredibly rare cases. See for example [1] where they discovered a single star at redshift 1 (roughly 6 billion years ago). Basically, if the star gets lensed in just the right way, it can be hugely magnified. This is a strong contender for the coolest observation that I know about. Galaxies are hard to see at redshift 1, to get a single star is crazy.
On your second question, generally people think that galaxies formed "inside-out". I.e. the inner region forms first, then the outer region. See [2].
Stars almost never collide with things (except maybe at the very center of the galaxy, but still super rare there), so survival isn't really a function of position in the galaxy.
That said, this observation is in stripe 82 (a very famous section of the SDSS. They observed it to greater depth than the rest of their area and many other surveys have since also observed it) which I'm pretty sure is away from the galactic plane (so not straight toward the center).
That's a weird distinction to try to make. Metal does mean the elements, not the spectral lines. The presence of those elements is usually inferred from the spectral lines, but if another method was used we would still say "metal poor/rich".
And there may just as well be an invisible dragon in my garage. There's no theory nor evidence that such exotic hydrogen impostors exist, so by Occam's razor we must assume that if it looks like hydrogen and quacks like hydrogen, it is indeed hydrogen.
An anti-hydrogen star - or even an entire star system - surrounded by normal dust would show annihilation events in the spectrum. So it would be very distinctive and unusual.
I guess so, if its electron/positron shell is the same. But I dont mean just antihydrogen. I'm sure there are many nucleus configurations that have the +1 charge and thus look like hydrogen from the outside.
But a larger nucleus would be unlikely to produce the same spectral signature even with the same charge. The energy transitions would be different, especially with different orbital shells and subtle quantum effects.
> It seems significant that the lens galaxy has little dark matter
I don't see that in the article? They centered on galaxy clusters which contain huge amounts of dark matter. DM is needed to account for lensing. There isn't enough mass in the stuff we can see to account for the lensing signal.
> How is DM supposed to cool, anyway
It can't! The way that normal matter cools is by radiating (giving off light). Dark matter doesn't radiate (if it did, we would be able to see it). So, while normal matter cools and settles to the center of the gravity well, dark matter doesn't and (as you say) forms physically larger structures.
I am referring to [0]. Tl;dr: Galaxy rotation curves are accounted for by ordinary General Relativity. At least for some. My comment turns out to refer to another article [1] linked from TFA, referring to a different sighting, that says "the lensing galaxy which hosts the radio source contains an unexpectedly low fraction of mysterious dark matter".
Usually we hear about lensing by galaxy clusters, not individual galaxies. If galaxies are short on DM, but clusters aren't, that seems to say something about how DM is distributed.
The early universe's expansion was not accelerating, as the early universe was not dominated by dark energy. I don't know off the top of my head exactly when that changed, but z=0.76 seems about right. So I'm pretty sure that is what that is.
The reason the dominant form of matter changes is fairly simple. As the universe expands, the amount of matter doesn't change, so the matter density goes as 1/r^3. The amount or radiation goes as 1/r^4 as there is an extra loss of energy due to redshifting (E = hc/wavelength). Dark energy though is (we think) a constant, so as the universe expands, the amount of it stays constant.
I only skimmed the paper past the abstract, but for what it is worth.
The MOND favouring group is a fringe of the cosmology community. The vast majority feel that there is enough evidence to rule it out.
I mostly mention this because I don't like that fact that popular science magazines (or at least their content that I see posted here!) has a bias towards "new and possibly exciting" or "controversial" research. Which I understand - revolution is more interesting that "physicist reduces error bars by 50%. Big picture unchanged". But, if all you read is these articles, you will get a very skewed idea of what the consensus is.
Just so there is no confusion, modified gravity as an explanation for Dark Energy is very possible, as an explanation for Dark Matter, the consensus is that it is ruled out.
Edit: I clarified my point below but will do it here too so everyone see it. I don't have a problem with this paper, I'm glad people are writing papers with alternate explanations to the consensus, that is how science is done. But, your conclusion from reading this article shouldn't be, "ahh damn, I guess MOND is right and LCDM is wrong" and I think that is how pop-sci articles tend to frame these things.
It's seems that the authors of the paper all come from the LCDM/Dark Matter observational testing community, this isn't a paper by MOND theorists.
They were quite likely looking for evidence of dark matter with the ESO survey and found something else.
Right or wrong, this is the definition of good science.
Vera Rubin would approve. Despite making a lot of the critical rotation rate measurements on spiral galaxies [1,2,3], it seems as though she was never particularly happy with the interpretation of this result as dark matter:
> "If I could have my pick, I would like to learn that Newton's laws must be modified in order to correctly describe gravitational interactions at large distances. That's more appealing than a universe filled with a new kind of sub-nuclear particle." [4]
TFA ends with, "It’s an intriguing result, and it may lend some weight to the MOND hypothesis for further study. But it’s important to keep in mind that so far the bulk of the evidence still points towards dark matter, and it’ll take much more work to topple that hypothesis entirely."
The other comment threads in here are discussing the actual experiment and theories. But this thread is at the top taking up a bunch of the oxygen and it's just repeating tired old media criticisms that we've all heard before. The actual experiment is way more interesting.
Just to play devil's advocate... sometimes a little spectacle is OK.
A lot of these ideas really are "new and exciting." Science just moves at a slower pace than media. It's not a monthly. By exaggerating the pace they're.. uhm... bridging the gap or something.
Controversy is even more engaging than novelty. Maybe a pop science article gets you sucked into the pre-clovis camp of a paleoanthropology controversy. Now you are engaged in paleoanthropology. Three years later, a possibly butchered snake skeleton is found and you go "aha! I was right! They ate snake soup! Clovis people didn't even like snake!" It's a little cheap, but it's also fun. Why not.
People enjoy having opinions. No one loves sports without having a favourite team, strong opinions regarding training schedules and sports rehabilitation practices... an occasional gamble. Most know that they're not really experts, but they enjoy being in the fray nonetheless.
Pop science magazines aren't supposed to be textbooks or encyclopedias. We are fortunate to have wikipedia for that. Give me a little sauce, a little clickbait. I might not always admit to it... but sugar tastes good.
That's a fair point. I love reading computer hardware rumours, most of which are probably total garbage (and probably obviously so to anyone in the field). And in this case, whether the general public thinks the universe in MOND or LCDM really doesn't matter at all.
My real issue is when this reporting is on things where the general public's opinion does matter. Things that the general public might vote on. Economics, medicine, etc. Having seen this type of reporting in a field that I do know something about (and a field where there is no real incentive to mislead, again MOND vs LCDM, who cares), I'm a lot more distrustful of science reporting in fields I don't know much about (and where there are incentives to mislead).
If they had published the article exactly as is, giving you all the excitement, but just added a single line somewhere saying "this is new work that is up against a large body of previous work that points in the opposite direction. Let's see what happens, but its a cool idea" I'd be totally fine with it.
> But it’s important to keep in mind that so far the bulk of the evidence still points towards dark matter, and it’ll take much more work to topple that hypothesis entirely.
The funny thing is that I agree with you that there are a lot of bad pop-sci articles that are misleading in the ways you're talking about. This particular article just isn't one of them.
Even though it's light on detail, I'm actually impressed at how measured & factual it is. They even managed to resist a clickbait headline.
Lol, TLDR; strikes again. Guess OP should've read more than the abstract if they "would've been fine with the article if it had contained a sentence like this one"
I find this within the sciences also. A lot of the more provocative scientists are willing to be wrong while promoting strong versions of their hypotheses. While this can be criticized as unscientific, I tend to believe that it serves a scientific purpose. Presenting a strong version of a hypothesis pushes people to contend with it, gather empirical evidence, and then incorporate a more moderate version into the idea-sphere.
I think OP's point is that pop science reporting is more than "sometimes." Keeping up with controversial theories is fine, often ideas that turn out to be revolutionary are controversial, but it's important not to get a warped perspective about what the broader scientific consensus is.
I know more than one person who has taken it to the extreme, to the point that they latch onto any and every controversial idea seemingly only because it's controversial. That's what you want to avoid.
It's true the LCDM is the consensus, so this result is even stronger from an outsider's perspective since the lead author apparently comes from the LCDM community, not the MOND community.
Specifically: “I have been working under the hypothesis that dark matter exists, so this result really surprised me,” Chae said. “Initially, I was reluctant to interpret our own results in favor of MOND. But now I cannot deny the fact that the results as they stand clearly support MOND rather than the dark matter hypothesis.”
> mostly mention this because I don't like that fact that popular science magazines (or at least their content that I see posted here!) has a bias towards "new and possibly exciting" or "controversial" research. Which I understand - revolution is more interesting that "physicist reduces error bars by 50%. Big picture unchanged". But, if all you read is these articles, you will get a very skewed idea of what the consensus is.
I stopped reading popsci mags for this reason. But I do feel like I'm missing out too. Do you know of any good mags that mostly talk about mainstream stuff, but targeted towards "I studied some of that in college but I don't work in the field"?
I think physicists throw around the word "fringe" too easily. Most physicists think that MOND is not true, but "fringe" implies that the physicists who advocate for it are wackos, like they're Young Earth Creationists or something.
MOND may be a fringe but wholesale support of Dark Matter by mainstream physics has always seemed cargo culty to me. Over a hundred years and we still don't have a good understanding of dark matter.
A red flag to me is how there doesn't seem to be large amounts of dark matter in areas closest to us where we can see best. It's all this far off enigma. And at least originally the theory existed to explain why the laws of gravitation didn't line up with visual evidence.
To me "half the matter is invisible" is just as outlandish as "maybe our math is wrong about gravitation". I don't think enough of the community questions the dark matter theory.
Well, maybe the thing is you just don't know anything about it. Current dark matter concepts are 40 years old, not over a hundred (again, Wikipedia is not a substitute for an education). And we have detected indeed a very common kind of actual dark matter, predicted 26 years before you could "see" it simply because it explained the data, we call it neutrinos. The universe is brimming with cold neutrinos btw.
Everything seems outlandish from a prejudiced superficial POV.
Probably, but then HN commenters could reduce this tendency of stating that whole scientific disciplines don't know what they're doing/are full of deluded morons. Particularly when it comes to physics. At some point you have to mention the other possibility.
Who gave you the idea that it's over a hundred years old? The solid results are from the 70's, while a hundred years ago it was still an open question if galaxies really existed...
Not sure what you mean with there not being any dark matter (DM) in our neighbourhood, the DM content of the Large Magellantic Cloud is estimated to outweigh the visual matter by a factor of 4, and the LMC is right up in our face.
The astrophysics journal (ApJ) is a really good journal. A majority of good astronomy papers are published in ApJ or in MNRAS. Big things go in Nature/Science + then there are other smaller journals.
(At least this is what I tend to find. This may just reflect my biases - US based, in the cosmology field.)
But just because something gets published doesn't mean it is right :) I think non-scientists don't know what "peer review" actually entails! First, as this was a MOND paper, it could well have been reviewed by someone who favours MOND. Second, even if the reviewer doesn't favour MOND, if the steps taken and the arguments given seem reasonable, I expect they would suggest it should be published.
I have no issue with the paper being published. It is important that theories have advocates who put forward the best argument for them. What I do take issue with is the skewed presentation in popular science. What sells is exciting and new, not slow and steady. And 99% of science is slow and steady.
Also, peer review in astronomy generally consists of correspondence with a single reviewer. There may be multiple rounds of review but a significant majority of papers submitted by professional astronomers doing serious research to journals are ultimately published. It is not the norm in astronomy to be rejected outright from a top journal and then submit to a lower tier journal, instead almost everyone publishes in a few popular journals. This is a tradeoff, but definitely in astronomy at least this means some iffy papers are ultimately published, even in ApJ, and you must always be aware when reading the literature that the paper you are reading is not infallibly correct just because it was published in a journal.
I just think that it is very hard to understand the scientific consensus (average view of people who spend a lot of time thinking about this) when all you read are popular science articles that tend to focus on the exciting/new/possibly game changing edges. I'm just here letting people know what the consensus is.
Most people on HN are aware that the consensus, a form of argument by authority, is dark matter. It is also known that the dark matter consensus has problems despite billions spent on research over decades. When there is an experimental result that contradicts the leading theory, that is interesting and worthy of media attention. If this experimental result was only published in popular media, then I too would likely ignore it. However it was also published in a major journal. Like you said elsewhere, that doesn't mean it is right. But I think it is worthy of attention and discussion and should not be dismissed out of hand because it doesn't agree with consensus.
The existence of a consensus opinion isn’t an argument from authority. To claim so is an interesting form of the post hoc ergo propter hoc fallacy ('after this, therefore because of this'). The argument for agreeing with the consensus isn’t the existence of the consensus, but rather the same argument that caused the consensus to exist, the underlying body of research.
Framing it as a result that flies in the face of consensus is fun and exciting, especially since people who are science-literate know that a single compelling result can overturn a consensus formed by a large body of previous work. But framing it in that sense is unhelpful, since the vast majority of publications that “fly in the face of consensus” do not. It’s a lot less exciting to view this as one more paper on a large pile supporting MOND, that is still small in comparison to the pile that support dark matter. The paper is obviously worthy of attention and isn’t being dismissed out of hand, it is published in The Astrophysical Journal. But would Hacker News be discussing it if not for the contrarianism embodied by the former framing, as opposed to the latter?
"Here is why the consensus is _______" is not argument by authority, correct.
"The ________ theory/hypothesis is fringe, the consensus is ________" is argument by authority.
See the difference? Phrasing matters in this case. All too often it is phrased the second way. I don't expect someone to literally enumerate all the evidence for or against something, but there is a middle ground between that and just saying "well consensus is ______".
>The existence of a consensus opinion isn’t an argument from authority.
That's exactly what it is. The rest of your argument boils down to, "if a lot of prominent people in a field believe something, it must be because there is a lot of merit-based evidence". That assertion is completely false. Merit-based evidence is one of the ingredients that lead to consensus, but hardly the only one.
I see your point, but I think the person you're responding to is trying to say that he is not saying "if a lot of prominent people believe something then it must be because there's a lot of evidence" but rather "there is a lot of evidence, that is why so many people believe it." The difference there is in actually being able to show you the evidence rather than just telling you to trust a priesthood. I don't think that the person you're responding to is using the consensus in place of the evidence, but rather telling you that if you look into it deeply you'll realize why the consensus exists.
It's not, because is specifically argument based on authority. Consensus could have authority in democratic context, but that isn't the meaning of "argument by <X>" which is the distilled context of some basis of proof. You could just as easily link consensus to "Argumentum ad populum".
This doesn't really apply either though, because we are talking consensus among a specialized group of experts/peers, which seems to me a lot more relevant that general consensus. Appeal to authority isn't always fallicious: https://en.wikipedia.org/wiki/Argument_from_authority
Authorities are really useful ways to understand the world.
The vast majority of people would be more correct about the world if they aligned with scientific consensus.
One problem is that journalistic coverage of ideas isn't proportional to beliefs held by experts in that field. Which gives the impression science is constantly changing, and that fringe theories are more widely held than they are.
That's why it's so important for people familiar with the field to help the rest of us who aren't know what "the field considers this a wacky idea".
If you are in the field, attempting to contribute, then I don't think authority is a good rubric. But for those of us who aren't, I think it's necessary. The world is too complex for all of us to make up our own minds on everything.
> But for those of us who aren't, I think it's necessary. The world is too complex for all of us to make up our own minds on everything.
More specifically, attempting to make up our minds on everything will inevitably lead us to accept the simplest superficially plausible explanations (that fit our existing biases), and the world is too complex for all those simple explanations to be correct, so we'll mainly find ourselves in the local maxima that have already been explored and properly abandoned by specialists.
The Fine-structure constant has been discussed that it is not a constant but slightly varies in the observable universe. Would make no wonder, if gravitation is related to the fine-structure constant, that gravitation varies too.
Science does not work by consensus opinion. I know many non-scienctists and even some scientists get pissed when you say this but it is the absolute truth and true to the scientific method.
This idea that the "consensus" has ruled out all other theories for a substance that we cannot even detect is an appeal to authority logical fallacies and a bias towards a known flawed paradigm. Authorities who have never detected Dark Matter say it cannot possibly be anything other then Dark Matter.
Thomas Kuhns The Structure of Scientific Revolutions details this mentality that leads to these sort of errors in thinking, which can be summarized as follows (taken from an outline of his book found here: https://www.uky.edu/~eushe2/Pajares/Kuhn.html) :
--Students study these paradigms in order to become members of the particular scientific community in which they will later practice.
----Because the student largely learns from and is mentored by researchers "who learned the bases of their field from the same concrete models", there is seldom disagreement over fundamentals.
----Men whose research is based on shared paradigms are committed to the same rules and standards for scientific practice.
----A shared commitment to a paradigm ensures that its practitioners engage in the paradigmatic observations that its own paradigm can do most to explain, i.e., investigate the kinds of research questions to which their own theories can most easily provide answers.
Even the author of this paper is an LCDM (AKA dark matter exists) advocate who had to admit that his preference does not fit the data observed:
"I have been working under the hypothesis that dark matter exists, so this result really surprised me,” Chae said. “Initially, I was reluctant to interpret our own results in favor of MOND. But now I cannot deny the fact that the results as they stand clearly support MOND rather than the dark matter hypothesis.”
The keyword there is "reluctance". This sort of mentality ripe with internal bias towards the existing paradigm is the number one thing that I think holds back scientific progress. The breakthroughs that push things forward rarely come from the consensus holders and those simply doing research that refines the current paradigm. Dark matter / Dark energy has never been detected / sourced - and the by the way the Standard Model of physics IS DEFINITELY WRONG and does not explain all observations. It simply our best approximation just like Newtonian Mechanics was, but we need to look beyond it rather then be scared to defy it.
> Just so there is no confusion, modified gravity as an explanation for Dark Energy is very possible, as an explanation for Dark Matter, the consensus is that it is ruled out.
How could you possibly rule out the theory that "the rules are different over there, somehow"?
I think the bigger issue is that LCDM has no produced much fruit in the last several years. Despite many attempts to detect it, no one has found anything. Furthermore, the main motivation for LCDM was super-symmetry, but the latter has also failed to produce much evidence in favor of it.
There comes a point where the consensus view is no longer seen as the most plausible explanation. This does necessary mean something crazy like modified gravity is true, but rather that there could be a better theory out there. However, in order to find that better theory all avenues need to be explored.
“It’s an intriguing result, and it may lend some weight to the MOND hypothesis for further study. But it’s important to keep in mind that so far the bulk of the evidence still points towards dark matter, and it’ll take much more work to topple that hypothesis entirely.“
Scientific consensus is often wrong. Science advances one funeral at a time. Most “scientists” are conformists looking for their next grant. Outside of the tenured professor elite, most of them are looking for the next job. And the tenured are just one step higher on the pyramid, motivated by prestige and admiration, not pure motives. There’s nothing wrong with that, it’s called being human. But don’t put too much stock in consensus, because many of the great breakthroughs have been ignored and ridiculed before finally being accepted.
While it's fun to criticize science this way, this line of criticism misses an important fact: namely that open scientific inquiry has been one of the most successful enterprises in the history of humanity.
In a period of a few hundred years we've gone from believing that there were a few basic elements and that the sun revolves around the earth, to understanding the deep nature of particle physics and the structure of the Universe. We turned a basic understanding of chemistry into an understanding of subatomic particles, and the ability to create entirely new elements.
We did all of this through a process of open and skeptical inquiry, which has been remarkably consistent in its ability to tear down unsupportable theories. The reason the Kuhnian critique exists is not because the scientific process failed, it's because the process worked but just took longer than people expected it to because people are human and imperfect. And the speed of scientific advances over the past decades has been higher than at any point in human existence.
The reason the term "scientific consensus" exists is because most fields are vastly too complex for a single human being to be able to evaluate the totality of the evidence by themselves, at least in a reliable way. So the process is necessarily decentralized and broken up among many experts, who share their opinions. This isn't some popularity contest that you should ignore, it's a critically necessary task that has to be performed in order to digest the research contributions of any field, and make progress on solving open problems.
You're absolutely right to point out that consensus evaluation can malfunction sometimes. You'd be equally right to point out that sometimes experimenters produce invalid results. You're wrong that the answer to the former is to reflexively ignore the scientific consensus process, just as you'd be wrong to say that "don't do experiments anymore" is the correct response to a few experimental errors.
The danger is that the apparent heights of "the piles" are badly skewed by bias: the evidence for what you favor naturally feels more solid, while evidence that contradicts it, or that it entirely fails to predict, proves very easy to ignore indefinitely.
We know that a conductor moving in a magnetic field produces a voltage, and knowing the strength of the field and the motion, we know absolutely the voltage produced. Applied to moons of Jupiter and Saturn, we expect forces much larger than surface gravity of the moons, and therefore material leaving the poles. But when we find it occurring, we talk about "volcanoes" and "geysers". We carefully ignore that the volcanoes drift about like rubber ducks in the bath. We carefully ignore collimation that would need for the geysers to be shot from perfect paraboloid-shaped nozzles. It is easiest to just agree not to talk about perfect collimation, because it doesn't lead in a comforting direction.
Socially, people like a consensus. A challenger needs "extraordinary" evidence to displace it. But Nature doesn't play favorites: any alternative that accounts for all the established evidence is on equal footing. A consensus in the absence of compelling evidence, or in the presence of incompatible evidence, should make us suspicious that the consensus is a product not of evidence, but of biased preference. Seeing evidence carefully ignored should make us suspicious.
I am not aware of carefully-ignored evidence in the case of galaxy rotational anomalies, but this paper may be rubbing our noses in examples.
Nature is just as happy for all the leading theories to be wrong, and for us not to have invented the right one yet. The consensus can be wrong without any of the alternatives being right.
It is discomforting to find yourself wrong, but science isn't about comfort.
The counterweight to this is that there's an enormous prestige benefit for any scientist who conclusively overturns the established scientific consensus. This is why Einstein became so famous in his lifetime: not just because he had some elegant theories, but because he had theories that unambiguously matched the experimental evidence (and even offered new predictions) in ways the previous scientific consensus could not. And even though a few skeptics tried to resist his ideas, the scientific consensus worked in exactly the ways we'd expect it to as the evidence came in.
I have no idea what the situation is with current theories on the motion of the moons of Jupiter and Saturn. I'm guessing you also have an incomplete picture of the evidence, but you've got an alternative pet theory that explains some inconsistencies in the consensus theory. I'm also guessing your theory isn't a slam dunk, i.e., that there's good evidence against it and/or there's a distinct lack of evidence in favor of it. But I strongly suspect you're not going to present me with all of the negative evidence for your own theory in an HN comment: I would have to get the impressions of other people in the field in order to actually get a fair evaluation of the evidence. That's what scientific consensus is supposed to offer, and as imperfect as it is, it usually works better than trusting the opinions of a single enthusiast.
ncmncm>>> ... Applied to moons of Jupiter and Saturn ... [implications that there is something scientists are missing about "material leaving the poles"]
matthewdgreen>> ... I have no idea what the situation is with current theories on the motion of the moons of Jupiter and Saturn....
ncmncm> Motions of the moons of Jupiter and Saturn? Opinions of enthusiasts with pet theories? What are you talking about?
It was pretty clear to me what @matthewdgreen was talking about.
If this is some electrical universe support, I think that's a good example of why it's important to know and understand the scientific consensus.
There are all sorts of minor details that can be matched to all sorts of fine theories, but there is almost always overwhelming evidence in other places that contradicts them. Trying to reinvent physics from the ground up by picking a few details is a fool's errand.
In particular, EU can't explain gravitational lensing, it can't explain the equality of gravitational mass and inertial mass, and these are just some of the most obvious.
I'm saying that, even if it were possible for the electrical force to explain the motion of some moon, it still can't explain other things that gravity can, and I gave two examples of phenomena that general relativity explains that en electrical universe doesn't.
But perhaps I misinterpreted your post. I took it initially to mean that you believe electrical interactions to be a better explanation than gravity for the movement of those moons - a theory that actually exists out there, called 'Electrical Universe'.
If instead you simply meant something much more specific, that there are electrical interactions that could explain mass ejections seen on these moons better than some geological explanations, then I apologize for my tangent.
The point was a specific example of evidence (collimated fluid motion) not consistent with descriptions of the cause of the motion ("geysers") but avoided as a consequence of discomfort with its implications.
Your comments illustrated the phenomenon with impressive clarity: wholly avoiding mention of anything even peripherally relevant, while promoting prejudicial distractions.
I'm responding to a comment that pooh-poohs serious consideration of alternative theories because they are contrary to the "scientific consensus." No one is going to pursue alternative theories if people don't believe in them. Some of us go against the grain, and that's a good thing. But you appear intent in making any true belief in unpopular alternatives into a sin. God forbid someone have a fringe belief! Fringe is BAD and consensus is GOOD. No independent thought. No room for dreamers and speculators and hunch-havers in your world. At most they can coldly look at evidence for alternative theories but never believe them (and resist all cognitive biases with superhuman ability). Have you even considered that fringe belief, and obsession and cognitive bias in its favor, is essential for progress too?
And your talk about the process and malfunctions is frankly comical. These are human beings, not machines. The average person would rather tell a socially sanctioned lie that led to the death of a million people rather than risk his next promotion.
There have been 3 major cases in the 20th century that I'm aware of where well-established theories turned out to be wrong.
1) Plate tectonics (dismissed until 1962)
2) The Bohr model of the atom, confirmed by the colours of light absorbed and emitted by ionised helium - which turned out to be wrong
3) The Sommerfeld extension of Bohr's model.
Both (2) and (3) were thought to be correct because they gave predictions correct to 4 decimal places. This turned out to be a co-incidence(!!) and their theories turned out to be wrong and replaced by Dirac's model.
Given the amount of science done in the 20th century, I think that's a pretty good record.
The most insightful comment is buried at the bottom of the list. Two kinds of people in this world, those who think truth lies where the crowd is and those who think it's where the crowd isn't. The conformists won't see the blindingly obvious until it knocks them over. Unfortunately the genes that make us good for a farming society make us a little sheep like ourselves. Here's to the hunters who've struggled through this far into the age of the farmer! cheers!
Yes, except the evidence for dark matter is really an absense of evidence. So "new and exciting" in that context isn't some grand transgression. There's no experimentally supported theory of dark matter to transgress!
The evidence that dark matter is particulate in nature that obeys the gravitational force, but not the strong nuclear force or electromagnetic force does have actual direct evidence for it.
The other poster has alluded to the bullet cluster. The bullet cluster is a pair of colliding galaxies. We can measure the distribution of gravitational lensing in a region of space, and in doing so, indirectly measure the mass distribution. We can directly measure the light output of colliding gas clouds in the two galaxies. We can measure the distribution of stars within them.
Analysis of this data shows us that dark matter has momentum.
This tells us that if you want to reformulate dark matter in terms of a modification of variations of F = Gm1m2 / r^2 you'll need to do some really ... interesting things. On the other hand, we know neutrinos have mass, do not interact via the strong nuclear force, and do not interact via the electromagnetic force. We either have to assume really, really ugly math in order to give a fundamental force a momentum, or we can assume there are new particles that are sorta like neutrinos but different.
There are other problems that I don't fully understand. Apparently MOND is very, very difficult to reconcile with the rest of known theory if the speed of gravitational waves travel at the speed of light. Which the 2017 neutron star merger taught us that they do.
You're confusing direct evidence with circumstantial evidence. I'm not saying there aren't indications of such a particle. Of course there are. But what we have are a small number of measurements that require invoking a massive particle in order to explain discrepancies in the measurements. There is no experimental support for the existence of this massive particle.
And same thing applies to LCDM. How does it explain bullet cluster, and several others, existing in the first place?
Disclaimer: I'm not a cosmologist even if I do have a background in physics. I do like following the field. It's just not quite so clear as you imply.
And if we go into things like superfluid dark matter then it doesn't really matter if its dark matter or some kind of modified gravity. One has bunch of equations and what matters is how they behave.
Kringing is the same thing as gaussian process regression, and astronomers use GPs a fair bit. I'm not sure whether they are used more widely.
My favourite forgotten/isolated statistical method is MCMC. These were first used by nuclear physicists at Los Alamos in the 40s/50s, but weren't really recognized more widely until the 80s. This is probably partly because only people working on bombs had access to the computing power before then, but still.
Astronomy is also an interesting case because this law doesn't necessarily hold true. The power spectrum, or Fourier transform of the autocorrelation function, isn't monotonic for matter on large scales. For example, baryonic acoustic oscillations at early times in the Universe get "imprinted" into the cosmic structure, such that galaxies have a preferential separation between each other.
