That isn't the case at all. We have equations we use to predict observations, and in certain cases, those observations are not quite matching what we predicted. There are a lot of reasons why this can happen, and using the equations poorly is but one of them.
I really wish they'd just said we've found an inconsistency, between theory and observation, which is the actual case. It would, I think, better inform the public about the actual process of science, rather than making it sound like a new discovery has been made, which has not happened, clearly. Or perhaps the real discovery was the inconsistency, and that should be the framing of the problem. Describing it using sort of known words like 'energy' and 'matter' makes the general public think a new type of matter has been found, rather than what has actually been found which is a hole in our understanding.
Recall some predictions that were later confirmed: the top quark (18 years later) or the Higgs boson (48 years!). These theories were a jigsaw puzzle with a single piece-shaped hole. You could call "inconsistency!" and break apart the whole puzzle, or look behind the couch for the missing piece. (The piece was found!)
We also have real inconsistencies, such as between QM and GR. Not a missing piece but a yawning gap: no single observation can fill in that hole.
Dark matter is a "missing piece" problem. The dark matter hypothesis fills in the cosmological missing mass problem, galactic rotation curves, Bullet-cluster-style gravitational observations, the expectation of non-EM interacting particles, and others. The gap between prediction and observation is the size and shape of a single jigsaw piece; let's just find it behind the couch.
Dark energy is a "real inconsistency" problem. Predictions and observations are orders of magnitude apart. Well hell.
Two galaxy clusters have collided. The hypothesis is that normal matter will be slowed down by the collision, while dark matter, not interacting (as strongly?) with itself or normal matter, passes through in the collision. We can determine the locations of the gas by X-ray telescope, and the supposed location of the dark matter (assuming it exists) with gravitational lensing.
(I am not a physicist, just had this explained by a physicist friend of mine).
Perhaps we're wrong in assuming that all of these observations on very different scales (galaxy rotation curves over galaxy cluster collisions to large scale structure) are tied to the same unknown (dark matter), but if you want to explain them all in a simple way, a particle still seems like the way to go.
Remember that elementary particles have been predicted and found many times over the past years, whereas modified theories of gravity haven't seen the same kind of success. Of course this is only anecdotal, and may not mean anything, but I think it's part of the reason for most people's preference for a particle explanation.
I'm not actually familiar with the specifics so I don't know whether this is actually a good explanation, but it's at least worth discussing.
Sure, dark matter can explain those, but what if there's some not yet imagined change to the equations that gives the same results.
Maybe gravitational attraction is not r^2 at some non-obvious scale that we failed to measure (meters? mm? Casimir effect on cosmic dust? Solar system sized gravitational anomalies?)
Why relativity makes Mercury's orbit precess is very not obvious (I mean, the two-body problem is already hard without relativity). The bending of light is a more obvious effect for example.
Scientists didn't just jump to dark matter at the start, and no cosmologist will tell you that dark matter is definitely the explanation — it's simply the explanation that currently seems most likely.
How do you propose for a modified equation to explain the bullet cluster? That is, we have multiple good observations that show situations where the distribution of mass differs substantially from the distribution of visible matter, and good theoretical explanations why this should happen in the case of dark matter. This is not adequately explained by modified gravitation or other such effects.
One is that there's also a possibility that dark matter exists but it's only part of the story.
For the Bullet Cluster I wonder how reliable the estimation of gravitational mass is for cluster of objects, as I understand, it is the images of the galaxies behind it that are lensed by mass in front of it https://en.wikipedia.org/wiki/MACS_J0025.4-1222#/media/File:...
For one heavy object in front of another, it's easy to see how lensing works and estimate masses from there.
But with clusters and "fuzzier" mass distributions I'm not so sure.
This is the dominant theory, it's not in contradiction with observations, it's just, a little weird. Why things are like that is the mystery but that's it for dark matter.
Sure, this stuff is invisible. So is electricity but we deal with that.
(Dark Energy I don't enough to talk about).
Good description but bad example :). Photons are literally excitations of the electromagnetic field. You could say that everything except electricity  is invisible. Neutrinos are a better example as a known form of dark matter.
 yes yes electricity is just one phenomenon of the electromagnetic field. I'm just differently wrong.
I disagree with this -- dark matter and dark energy have been discovered in exactly the same sense e.g. quarks have been discovered. Like dark matter and dark energy, quarks cannot be observed directly. Rather, physicists have made observations that are most parsimoniously explained by the existence of a theoretical entity with certain characteristics we have named a "quark".
Similarly, physicists have made observations that are most parsimoniously explained by the existence of theoretical entities that behave like matter and energy but are otherwise difficult to observe (like quarks are difficult to observe directly).
The standard model provides a theoretical understanding of the nature of quarks -- but if further findings in particle physics disprove the standard model, then we'll have invalidated our understanding of the nature of quarks.
Similarly, if a future theory shows that dark matter and dark energy are not weakly interacting matter and energy then we'll have invalidated our understanding of the nature of dark matter and dark energy.
Dark matter is form of matter (matter is any substance that has rest mass) and it's dark (implying we can't see it and don't know what it is made of). Most hypotheses around the dark matter assume it's either new kinds of particles, or macroscopic objects.
Dark energy is also good name for hypothesis for unknown form of energy.
The article, and the OPs aren't saying we shouldn't explore these hypotheses. They're just pointing out that they are, well, hypothetical. We should be cautious of talking about these things definitively as though we know they exist.
Primary evidence makes it look like it's matter even before any hypothesis.
Practically all hypotheses looking the evidence assume it is form of matter. Not calling it dark matter just because there is small change it would be something else would be misdirection.
Are these not all cases of direct detection: https://en.wikipedia.org/wiki/Dark_matter#Observational_evid...
Physicists know that’s not good enough, and that it’s a major problem. I hope we do make progress, do come up with further experimental evidence or ideas for experiments we can test. For dark matter I think that’s actually likely, but I’m not so convinced about dark energy, there the evidence is a lot thinner.
It also depends what is consider direct detection, which I accept is a matter of opinion. For example I'd consider comparing the times on atomic clocks inside and outside a gravity well to be direct measurement of time dilation.
Or at least, that's what I've always understood. Not a physicist though.
There are many bosons that are massive (Z bosons for example) but are not considered matter. I think that normally fermions are considered matter.
Edit: s/barion/fermion/ bah, I know nothing.
Edit2: and of course gluons are not massive.
super pedantic and of course IANAP.
It kind of implicitly throws out the notion that there could be an issue with the measurement process/tools.
Sometimes this type of unconscious framing directs all our minds down the same path making us miss an obvious detour to an insight.
AFAIK this was the assumption early on, space dust, black holes/brown dwarfs (MACHOs), weakly interacting massive particles (WIMPs) and more were the leading theories. These are all normal (for physicists/astronomers) matter that just we couldn't see due to measurement limitations, so dark matter was an appropriate name. Only after all these theories were falsified we had to look at more exotic explanations.
Also obligatory xkcd: https://xkcd.com/1758/
These concepts assume that both are correct, in which case the answer has to be matter and energy that is there but that we don't see.
Joel told us that 'dark matter' was a term used at the time and that coffee is a favorite beverage of many astronomers. As one of the local Santa Cruz coffee shops was serving a drink called 'double dark espresso' (caffeine levels fit only for a tired astronomer, I guess), he decided to name the ΛCDM theory after one of his favorite beverages, hence the 'Double Dark' Theory.
I think dark matter is a perfectly fine term. It's stuff that doesn't glow or interact with much of anything, but seems to just fall down. The term 'dark' is very much in keeping with the naming conventions of the post-war ear, where things are muted and humorously named (Big Bang, MAD, Charm quark, etc). The community has really embraced the term and, per at least Joel's theories, has remixed the term into coffee and other drinks, riffing and expanding the names to encompass other 'fun stuff'. I'd expect the names relating to various scotches to creep in soon (double cask, 15 year, etc), if my friends' predilections are any guide.
Thanks for the summary.
The point is, the real discovery is not the existence of any new form of matter, because we have not discovered a new form of matter, rather, the discovery is that we've found a very interesting point at which our theories are inconsistent with reality.
I say "we" in the broadest sense of physicists, as I did study that for my grad/undergrad, but do not practice in the field (I now do the computering).
It might be interesting if we had a standard, and publicly known, word or phrase used when talking about scientific results that find an inconsistency between reality and theory (not just slang). Like, "today physicists discovered a Theory Bug when applying Einstein's general relativity to galaxies" or some such. Something cooler than that though.
I would be surprised if dark matter predated the Big Bang and survived it in and meaningful sense. I wonder if an theory in which dark matter is conserved during the very early universe is even consistent with observation.
The popularization of physics is a ultimately a significant source of funding for physics, along various vectors, and so terms like this are incredibly valuable to the field, regardless of how poorly descriptive they are.
In any case, physicists working in the field know what the terms mean: a huge bag of observations that are inconsistent with basic theories that we know to be incomplete.
This misconception can be explained in one sentence when somebody asks what exactly dark matter and energy actually are, and it doesn't really matter what people who don't care to ask think about the subject, because well, they don't care.
I was disappointed with their disappointment mainly because to me the finding of so significant an inconsistency is magically interesting. To be fair, I have a physics degree, and one of the things I loved about learning this stuff was finding all the places that our understanding falls apart.
At some point, we have to assume that observations correspond to an external reality or everything gets meta. While I agree that it may be convenient to make more clear what we know about dark matter, it is not easy to find the perfect name and, it seems to me, not a task for physicist, who just need a name for the terms in their equations.
'Dark Energy' is physicist code for 'anti-gravitating non-stuff that we cannot see'.
So what are all these "looking for dark matter" experiments actually doing?
It is still the most parsimonious explanation that there is some kind of gravitationally interacting stuff out there that we just cannot detect with our current measurement methods. It is the simplest hypothesis that can explain all of the available observations without adding too many epicycles to our otherwise well tested theories.
Fortunately, there are those who try to fix the bugs, see Modified Newtonian Dynamics as a Dark Matter alternative (as I mentioned elsewhere).
This is absolutely correct. What is its clear (and as evidenced by some of the replies to your comment) is that many so-called "scientists" are filled with hubris and lacking intellectual curiosity. They believe (more or less) that we know how "things work" even though our commonly accepted formulas and equations about how "things work" don't add up. In their minds, its just a matter of discovering a still-hidden particle or detecting "dark matter" or "dark energy" that must exist, because they are certain that their understanding of the universe is how things must be. Unfortunately, this is the opposite of how science works. Real science is based on verifiable measurements and observations that can be replicated and verified. Its fine and dandy to come up with formulas and hypotheses based on incomplete data sets, based on how you think things might be, as long as you understand that you could very well be wrong - no matter how well a given hypothesis may seem to work for a selected, discrete set of measurements.
I think of physics as a program. That program is built internally of the various models/equations, and that program takes a set of inputs, which are observables, and a time index. The output is the same set of observables, but with their values at the time index input. That is, physics essentially predicts (forward and backward) from a given set of observations, a new set of observations.
So to me, whenever the output observables do not accord with actual measurement, I first assume there must be something in the program that is wrong. Dark Matter is the equivalent of assuming that there must be another set of missing input observables into the physics program. It's possible, but to me the most likely first cause of the inconsistency is the program itself, as that is, as you said, how science works.
Obviously, nobody knows for sure yet. But I would caution most fellow laymen not to rely too heavily on the intuition that says, "dark matter? pffft!" or even, "but what about all of those observations that didn't match Newtonian dynamics?". Physicists (including the author here!) are generally smart enough to have thought of those objections themselves, which is why they've spent decades trying really hard to disprove the notion of "dark matter" by compiling all of these anomalous observations. Sometimes the universe is just unintuitive, at least to dumb apes like us.
I'm not saying you can't have a hunch that we're just doing the math wrong somehow; I just wouldn't be overly confident that's the case just yet.
It's not a hunch.
Green and Wald tried to proof that the inhomogeneities don't matter, others disagree that they proofed anything of the sort. It's a fairly robust debate, and I am not qualified to summarize the state of play. Here are some slides:
Edit: The rebuttal paper to Green-Wald from three years ago already has 100 citations... https://arxiv.org/abs/1505.07800
It's possible that the question will be settled in the next years through numerical simulations:
Edit 2: All of this is for dark energy, for dark matter I don't know if there is a similar discussion on the role of the post-newtonian approximation that is used there.
The usual working assumption is that if a well established theory indicates the existence of extra mass or energy, it usually exists in nature and can be found. This is essentially something that has its roots in particle physics: every violation of conservation of energy or momentum turned out to be caused by a hitherto unknown particle.
If you are saying that we observe galaxies whose gravity is weaker than your models for the distribution of dark matter, then that is an argument against your models, not for them.
And here is why: If you have two galaxies with about the same size and about the same number of observed stars they should have about the same distribution of barionic matter. So gravity should work the same in them, no matter if that gravity is described by Newtonian theory (probably not), General Relativity (I would assume that, but who knows) or your modified theory of gravity (maybe, maybe not). Any difference between them can not be due to the theory of gravity. But it can easily come from different amounts of un-seen dark matter.
I don't see why the scenario "gravity works differently at large scales" couldn't explain the observations until we have some idea how gravity would work differently.
Don't forget that each of these observations rely on a quite large sets of assumptions about everything from how much luminosity from galaxies with a certain (normal) mass can vary to how we estimate distances to very far away objects. We don't have that many observations of e.g. gravitational lensing. And, if we realize we actually don't know how to calculate things correctly with GR, or our theory of GR is wrong, that will have implications for all of those assumptions.
The dark matter hypothesis might very well be right. It is a very reasonable guess. But so far I think the proofs for it have been overstated.
And I can say myself that not everyone agrees with that discovery: http://www.astronomy.com/news/2019/09/astronomers-cant-agree...
Well, people still debate about the Bullet cluster. But if it's correct then it's actually a good (relatively) confirmation for some sort of dark matter. It two similar galaxies look the same but have dramatically different mass distribution then there's some mass we don't see yet.
I'm mostly making the case to the peanut gallery here to maintain a state of epistemic noncommittal. It's a very popular intuition to think that "dark matter" is just a weird consequence of modeling things improperly, kind of like how we used to think there was another planet between Mercury and the sun because that was the only way to make Mercury's orbit consistent with Newtonian dynamics. If we are modeling things improperly, I suspect it would have to be a pretty weird bug--and I think the one she's suggesting qualifies as such.
> Now, what we do when we want to explain what a galaxy does, or a galaxy cluster, or even the whole universe, is not to plug the matter and energy of every single planet and star into the equations. This would be computationally unfeasible. Instead, we use an average of matter and energy, and use that as the source for gravity.
> Needless to say, taking an average on one side of the equation requires that you also take an average on the other side. But since the gravitational part is non-linear, this will not give you the same equations that we use for the solar system: The average of a function of a variable is not the same as the function of the average of the variable. We know it’s not. But whenever we use general relativity on large scales, we assume that this is the case.
> So, we know that strictly speaking the equations we use are wrong. The big question is, then, just how wrong are they?
It's not a "hunch". It's just how the math works.
average of 0-9 = 4.5
4.5^2 = 20.25
average of squares of 0-9 = 28.5
The problem is that no one knows how wrong.
Yet we're no closer to a satisfactory answer. It's not that physics has some unresolved problems, it's that physics has a giant hole through its center.
Einstein got us closer than Newton, but his work is obviously incomplete. The dogma surrounding Einstein's work borders on religion.
But muh experiments!
How many times have Newtonian mechanics been proven? Lots and lots. And at one frame of reference (pun not intended) it's absolutely correct.
How is Einstein's work any different? It's not. Stop pretending only a chosen few can have meaningful ideas about how the universe works. You might need training to translate that idea into a workable theory, but not to generate the ideas themselves.
If I were you (collectively) I'd be taking ideas from everywhere. It's still your job to see if they make sense, so don't worry about the unwashed masses stealing your thunder.
Dark energy is less well established, but based on the evidence we have, Occam's razor points strongly towards dark matter. Dark matter is a specific theory that makes predictions, and as far as we can tell these predictions are borne out. There was a competing hypothesis -- that GR itself is wrong and needs to be corrected. These were in competition, but the evidence has decisively broken in favor of dark matter. If it was just a question of fixing the equations, then you should be able to predict the apparent pattern of dark matter from the distribution of ordinary matter. For a while it looked like maybe you could, but more recent evidence has shown that you can't. (This is the reason why the Bullet Cluster comes up as an example so much -- the Bullet Cluster looks like what you would predict if galaxies have dark matter halos and two galaxies collided.)
People also misunderstand the incentives here. If you could write down a modified theory that could explain all of the evidence, you would be the greatest physicist since Einstein, maybe the greatest since Newton. You would achieve immortal glory as one of the central figures of the 21st century. So people try to write down that theory, but it turns out to be really hard to do.
I’m not convinced we hobbyist physicists have anything to add to this topic. ;)
On average, I'd say that's a safe premise to adopt. But I'd add two things to that:
1. The question "is that the point?" That is, cutting edge cosmological research isn't (AFAIK) generally done on HN. The "real experts" probably aren't coming here looking for new insights, and the rest of us idling around chewing the cud on this isn't really hurting anything.
2. That said, this "cud chewing" may be beneficial to the participants in the conversation, or perhaps - in a "long game" sense - to science at large. If somebody reading all this is inspired to take up physics as a career field, or just learns something that they turn around and use as metaphorical inspiration in some seemingly unrelated field, well... maybe that makes it all worthwhile.
Anyway, at worst this is entertainment, and arguably of a higher quality than watching the latest episode of the sit-com de jour.
Or... maybe it _is_ hurting?
Junk may displace quality. An HN page filled with low-quality comments may discourage people with expertise from contributing. "Eternal September" and "Someone on the internet is wrong!" being less engaging than informed (or even just not energetically misguided) discussion. I certainly have a predicate of "ok, there's no point in my commenting on this HN post; it's 'gone bad'; there's now an inverse correlation between people having a clue and their being likely to wade through all this and potentially see my comment".
There's also "You play like you practice", and this is negative training on ignoring the criticality of recognizing expertise and its limits.
A bar discussion with an expert can go like a seminar. Or if without, yet with experienced people, like a panel. But as the available expertise declines, things can rapidly collapse towards a stereotype of a DC cocktail party, with nonsense lapped up and shared due to an inability to judge expertise and its limits. You get bad reddit, with babbled nonsense undergoing memetic selection largely disconnected from reality. FOX News, and the NYTimes's deemphasis of the role of political and economic interests, also come to mind.
> chewing the cud [...] isn't really hurting anything
So perhaps, alternately, it might be viewed as a intellectual integrity fail? One with civilizational impact?
> Anyway, at worst this is entertainment,
So then... its like HN and US public discourse about trade wars, sanctions and shooting wars and their civilian casualties, regulatory capture and industrial policy, education, public health, ... and so on? All sort of a reality tv show? /end snark :)
Hmm, random thought... my fuzzy impression is that views on lies are bimodal, with camps of "white lies are necessary social lubricant; to think otherwise is to be immature and inconsiderate" and "all lies are toxic; to think otherwise is to be oblivious to unintended and broader impacts". I wonder if there's a similar divergence of views with respect to comment and thread intellectual hygiene?
Ideally, we would have more flexible discussion fora. Discussion preferences vary among people, topics, times of day, etc. Sometimes I enjoy reddit pun chains, sometimes I find them an annoying distraction. It'd be nice to be able to toggle seeing them, rather than everyone getting a similar view all the time. But for now... I think of HN discussion as "breaking down" as topics become distant from tech.
It seems to me a dark matter hypothesis is hardly extraordinary—that is, I don't see why anyone would have priors that particularly disfavoured it—and, if it were to exist, us not knowing much about it doesn't seem particularly surprising either.
There are a whole bunch of very different observations that don't match theory in different ways, if your theory doesn't include dark matter.
But if your theory includes dark matter, all those various experiments match theory pretty darn perfectly.
There's no a priori reason why something like dark matter shouldn't exist. It would be nice to directly detect it through scattering experiments on Earth, but there are a lot of possibilities for what dark matter is, and each would require a different type of experiment to detect.
There are three ways to detect dark matter:
1. scattering in a lab
2. annihilation products observed with a telescope
3. gravitational effects
We've seen 3, and we'll probably get a huge amount more detail on the distribution of dark matter through that method as time goes on. That would already be pretty convincing to me.
People have been looking for both 1 and 2 for a while, without any conclusive detection. But it's easy to write down theories of dark matter that are extremely difficult to detect with those methods.
At some point, we may have to accept that the only way to detect dark matter is method 3, through gravitational effects.
And there's a theory that says there are small "primordial" black holes all over the place, which are also hard to detect individually, but together could also account for a large part of the missing mass.
Perhaps invisible brown dwarfs and invisible black holes are an easier pill to swallow than mysterious dark masses/energies?
"A survey of gravitational lensing effects in the direction of the Small Magellanic Cloud and Large Magellanic Cloud did not detect the number and type of lensing events expected if brown dwarfs made up a significant fraction of dark matter."
And Hossenfelder really means the we are using the equations wrong. Not that are using the wrong equations.
or http://faculty.cs.tamu.edu/schaefer/research/nonlinearSub.pd... with nice graphs
As a non-physicist, observed dark matter gravitational lensing really points to "there's more gravity than we expect" rather than "gravity works differently than we thought" for me.
Are there not galaxies on opposite sides of the universe, expanding away from each other too fast for them to ever interact?
Does this mean instead of individual objects we make our calculations with x units of mass and energy in every given patch of space and this may be an issue, or am I getting this wrong?
Pretty much yes, as we can only take observations like that.
More importantly, the GR equations are non-linear, so taking these 'average' observations and feeding them into our models may introduce significant error.
Or another way of saying that, it's possible that the model would give accurate predictions if you were able to feed it precise and complete information (the details of every single point mass) but not give accurate predictions if you feed it the sampled data we have (observations about whole galaxies, for example). People have discussed this elsewhere in this thread as the N-body problem.
It's also saying that even if we did have that level of detail, our numerical simulations aren't currently capable of calculating at that fine a level of detail.
Never got a satisfactory answer.
For example the gravity between two objects depends on the relative speed between them (since gravity is proportional to energy, not rest mass). Are we calculating that for each and every sun orbiting in a galaxy?
It's a lot of interactions, each sun interacting with all the rest.
It gets worse - gravity is also proportional to potential energy. So you need to include how much energy you would have if every sun fell into every other sun, not just their rotation.
I just can't shake the feeling that dark matter is just this unaccounted for energy in a galaxy.
Disk stars in the Milky Way only have velocities on the order of a few hundred km/s. The relativistic contribution to gravity from such velocity is negligible.
Perhaps more importantly, we don't even have complete information, but only measurements that are necessarily 'averages'.
We don't even have a formulation of this model that allows us to understand the 'error' in these measurements, where here error is about making future predictions based off those measurements.
To use a perhaps tenuous analogy, say we have a model that describes exactly how air molecules interact with each other. We take measurements of parcels of the atmosphere and are able to describe what the molecules within are doing - pressure, temperature, humidity, etc. If we want to describe what happens to the entire atmosphere, however, we need a different model that describes how the parcels of air interact - cold fronts, wind patterns, rainfall etc. We have continuity between these two models, because as far as we can tell the way these parcels of air interact is consistent with the way individual molecules interact, but the actual models are very different to each other.
With general relativity we have a model that works incredibly well for understanding how a small number of things interact with each other, and we assume that it describes the interactions of every object in the universe. We currently use the exact same model to talk about parcels of objects (eg galaxies) in just the same way as we talk about individual objects (atoms? stars?), and we don't know if that is reasonable or not. It's obviously reasonable at a small scale, as when we model things like our solar system we are accurate to an extremely high level of precision but it's not obvious that this continues to hold as we scale up.
When trying to work out a weather forecast we don't simulate every single molecule, but instead large parcels of air (at a surprisingly fine level of detail, it must be said, but still relatively huge). It's not even reasonable for us to measure every single molecule, even if we had the computing power to simulate it.
Even so, it is far more tractable to simulate every molecule of air in our atmosphere than to simulate GR for every body in the universe, or even every galaxy!
We need a model for the interaction of large collections of objects in the universe, and at the moment the best we have is GR. What we don't have is a way of measuring how accurate that is, or even a way of formulating the model that would be consistent when applied to the kinds of collections of objects we're capable of measuring.
It's possible that dark energy and dark matter are real things we can't (currently) directly observe, or they could be artefacts that arise when you try and apply GR to 'averages' of large collections of objects, but right now we don't have a way to quantify how accurate those models are in order to rule out the possibility one way or the other.
They're also assuming that the majority of the mass is in the gas, not the stars or invisible brown dwarvf stars or even black holes.
It's layers of assumptions a mile deep being used as irrefutable proof.
What's wrong with basing your results on gravitational lensing? Is it related somehow to the complexity of inferring on how much the images are wrapped by gravitational lensing?
This is all a consequence of n-body dynamics being chaotic 
Each initial set of conditions would create a unquie system.
Look at Banach–Tarski paradox
All systems are based off the initial set of conditions. The axiom of choice.
The issue is the degrees of freedom introduced with more dimensions...
The author published a book with the same "we're wrong" narration, so she has certain motivation to repeat herself.
Most pop science, even the ones featuring physicists, present speculative ideas as if they were well established facts. (Hello string theory)
Finally, criticism of a theory does not require presenting an alternate theory. She presents an argument. If you don’t agree with her conclusion then you need to rebut her argument.
Remember why he even added it in the first place.
It was to create a model of the universe that is frozen. It's creating a reference frame.
Depending on which reference frame we use, we get different numbers.
CMB vs Candles
Not surprising given we still can't even explain the double slit experiment wwithout resorting to paradox and contradiction.
For all we know telepathy, magic, reincarnation and wormholes all might be true, we just haven't advanced our understanding of the universe and reality to that point yet.
To be honest, that looks just like a very old (ca. 1990's) noise filter from 3d Studio Max (where it would be used to make smoke, fog, but also very realistically looking veins, etc).
("Filter" is not the right term. Sorry, I haven't touched Max for ages.)
It may be accurate to use those averages, or it may not be if for example the chaotic nature of N-body problems causes reality to diverge significantly from the simpler model; we don't know how large the error actually is and currently don't have a way to measure it.
For instance, if you were an alien scientist on the other side of the galaxy measuring the atmospheric composition of Earth, there's no way that you could make a prediction to match the result without also modelling emerging properties of intelligence. We know that this is true, just as we know that intelligence and computation are physical properties of the universe - so why isn't there a serious branch of physics which tries to take this into account?
I have a similar opinion about "cosmic inflation", as it happens; it appears to be a solution to a problem with the equations.
In both cases, it looks to me very much as if someone has described the problem, and then announced that their problem-description is actually a solution. Nice work, if you can get it.
I find it very arrogant to believe that our current model is the model. New physics are discovered when the model is found to be broken at the edges, and a new model emerges whose explaining power is a superset of that of the previous model.
I guess we're coming to the end of the "normal physics" stage of Kuhn's cycle of scientific progress . I wonder whether the current incentive structure for science will let us progress to the next phase, or trap us for unnecessarily long in the current one. I hope it's the former.
I think it would be arrogant, but I've never met anyone who studies physics and believes this (though I wouldn't be surprised if some exist). It's not arrogant, however, to be dogmatic when faced with ideas that are incompatible with established models. It's unreasonable to claim someone must be using a broken model, because dark matter and dark energy looks wrong.
Scientific models are good when they are predictive, and powerful when they are simple.
It's incredibly rare for a model-in-use to be wrong - we would never use something that has no predictive power - but every day scientific models are tested, refined, expanded, and simplified in order to make them either more predictive (better accuracy) or more powerful (describe more things).
Sometimes this does manifest as being 'broken at the edges' but not always. Sometimes a model is just fuzzy, and improvements add resolution to every prediction.
> Scientific models are good when they are predictive, and powerful when they are simple. [...] every day scientific models are tested, refined, expanded, and simplified [...]
It seems to me that dark matter goes directly against this. The current model of gravity can't explain certain observations, so we come up with a form of matter and energy that we can't observe in any way, and doesn't interact with anything, except with precisely the one thing we need for our observations to match the theory. A theory that hasn't even been reconciled with quantum mechanics yet!
Smells super fishy to me. But as I say, my knowledge of physics and astrophysics is super basic, and I wouldn't call myself "someone who studies physics" in any meaningful way. I understand your feeling that it's unreasonable for me to criticise the status quo because dark energy looks wrong, as I have no idea about the underlying math.
The current top comment by superqd probably deals with this best. Maybe there is a literal dark energy and dark matter, but the thing that is manifested is a 'correction' term in the way we use these equations, and it so happens that using those correction terms makes these equations more accurate.
I'd almost go so far as to say the uncorrected equations are a model that is broken at the edges, and dark energy and dark matter are simply a quantification of how broken they are (with the added benefit that adding them to the equations makes the model better).
I look at some of the more fundamental discoveries of the past, especially things like radiation, electricity, molecular structure, etc, and wonder what it must have been like to not have a basic understanding of those principles. "Those people were such primitive idiots, they didn't even understand that water is h2o!" Or something like that. Then I look at stuff like dark matter, and it all of sudden makes sense. We're idiots, too. That's what it feels like.
Einstein never really got comfortable with the real world implications of relativity, outside of the math. And of course he straight up hated quantum probability.
It's really intriguing to me that of the the fundamental forces, we've been able to do so little to manipulate gravity. Hell, we can barely even measure it precisely. The most we've done with it is figure out how to sling satellites with flybys. I'd say we're Ben Franklin in the lighting storm, but I don't know that we're even at that level of understanding. He at least had a testable idea.
Wouldn't things like "gravity", "light", "magnetism", "electricity" look wrong if you weren't experiencing it daily ?
Science is moving all the time, see "dark matter" as a placeholder word for something we don't understand, it might be one things, or multiple things, or nothing and we just got something wrong before, it doesn't matter, what matters is that we're observing something we can't fully explain and we're trying to find a solution to the problem. Most high level science look "wrong", there is no intuition for these kind of things, that's why the scientific method was developed after all.
Let's assume we observe a system of planets and we have a good theory to describe its behavior.
Then with better tools and more observation we found an orbit deviation. Patch it by assuming additional yet unobserved planet? Or patch it with much more sophisticated mathematics?
Aether was more a question of esthetics. It didn’t really help to explain anything and was quite easy to debunk.
Dark matter and dark energy are quite different. It might not be the endgame, but these are the best theories we have so far and they work pretty damn good.
Relativity (time dilation) & > 3 physical dimensional mathematics is rejected in favor of physical experimentation & interpreting physical phenomena through the lens of plasma behavior (dark & glow & arc modes, discharge, z-pinch, Birkeland Currents, etc). The EU model has successfully predicted surprising phenomona of asteroids/comets & astrogeology and makes bold interstellar predictions. Luminaries, deviating from the standard model, include Hannes Alfvén, Anthony Peratt, Ralph Jurgens, Immanuel Velikovsky, Kristian Birkeland, Nikoli Tesla, David Talbott, Donald Scott.
Recent physical experimental success include the SAFIRE project. "The SAFIRE PROJECT reactor generates energy densities analogous to the Sun's ...in a laboratory on Earth".