Comments
vrkas t1_iwho2ly wrote
> I'm soo confused why they keep talking about the standard model in relation to gravity.
There's a standard model of particle physics, which the one you are referring to (and the original btw), and there's a standard model of cosmology called Lambda CDM. Being a particle physics guy I've only ever called it Lambda CDM.
Ok_Meat_8322 t1_iwi56m8 wrote
And the especially relevant bit, for this topic, is the "CDM" part, where "CDM" stands for "cold dark matter".
("lambda" denotes a positive cosmological constant, i.e. "dark energy", so the standard model of cosmology = a hot big bang + dark energy + cold dark matter)
Ok_Meat_8322 t1_iwi6qzv wrote
>I'm soo confused why they keep talking about the standard model in relation to gravity.
The standard model of cosmology (as opposed to particle physics) is the lambda-CDM model, where "CDM" stands for "cold dark matter" (and "lambda" denotes a positive cosmological constants, aka "dark energy").
>I think the main issues is that MOND by itself simply doesn't explain everything we see. So last I herd was that the only feasible MOND theories left were "MOND + dark matter" theories. I wasn't even aware that there were any major theories that didn't include dark matter of some kind.
From my own understanding (i.e. as a hobbyist with a background in philosophy, not physics), the entire purpose of MOND is to avoid having to invoke dark matter- the rough idea being that gravity works differently on the scale of galaxies/galaxy clusters, and that correcting for this explains the discrepancy between the observed rotational velocities of galaxies and galaxy clusters vs. their apparent mass without having to invoke a new type of matter.
InTheEndEntropyWins t1_iwigw5v wrote
There are lots of different types of observations that dark matter explains.
Even if MOND perfectly explained the rotational speed in galaxies it couldn’t explain the other observations. So you still need dark matter.
> The most serious problem facing Milgrom's law is that it cannot eliminate the need for dark matter in all astrophysical systems: galaxy clusters show a residual mass discrepancy even when analyzed using MOND
The fact that some form of unseen mass must exist in these systems detracts from the adequacy of MOND as a solution to the missing mass problem, although the amount of extra mass required is a fifth that of a Newtonian analysis, and there is no requirement that the missing mass be non-baryonic.
Ok_Meat_8322 t1_iwik6sj wrote
>There are lots of different types of observations that dark matter explains.
Sure, and the entire purpose of MOND is to account for these observations without having to invoke dark matter. So being forced to accept "MOND + dark matter" would completely defeat the purpose of proposing MOND in the first place.
ConsciousLiterature t1_iwiifqg wrote
MOND so far has been unable to explain all the phenomena dark matter does. I think most scientists see it as a failed effort.
Ok_Meat_8322 t1_iwikmts wrote
That's certainly my impression as well. But it wasn't a self-evidently crazy idea or anything, and probably adds some value to the conversation even if it is a failed effort (nothing wrong with trial and error, after all).
Ok_Meat_8322 t1_iwhgcak wrote
Nowhere to be found? Its everywhere we look- virtually every galaxy/galaxy cluster displays evidence of the gravitational influence of dark matter, same for the lensing of more distant galaxies and galaxy clusters. As the blog/essay admits in the second paragraph, what is absent are viable candidates for dark matter particles... but then we have no real idea whether its even constituted by a type of particle in the first place, this is only one proposal among many.
I don't think MOND should be categorically ruled out, for all time; new proposals add something to scientific inquiry even when they don't turn out to be correct, but MOND has a tough road ahead if its ever to be considered legitimately competitive with its rival theory.
jenpalex t1_iwhrt7s wrote
“ Since only one (at most) of these two cosmological theories can be correct, you might expect that only one of them (at most) manages to achieve correspondence with the facts in the preferred way. ”
What rules out the possibility that both effects could be operating?
Occam’s Razor is a guide to theory making, not a rule.
InTheEndEntropyWins t1_iwi28wr wrote
I don’t think MOND can work by itself. So I think most MOND theories would require dark matter to work anyway.
So really MOND is both in practice.
jenpalex t1_iwhtlv6 wrote
I would have thought that each of the competing theories could be tested in another way-by asking the question:
If theory X is true, how did the effect originate, and develop, in the Big Bang and its aftermath?
ConsciousLiterature t1_iwii6xl wrote
What do you mean "nowhere to be found". We have found dark matter. We know where it is because it's gravitationally lensing photons. We also know where it's not see the bullet cluster https://en.wikipedia.org/wiki/Bullet_Cluster
We have found it but not by direct observation because it does not emit light but it does interact via gravity. We know it's out there, we just don't know exactly what it is yet.
southbuck87 t1_iwj421v wrote
No where in this article do they address the accelerating expansion of the universe. I’ve heard some pretty lame rationalizations for it but nothing that really explains it. It seems to me that neither theory in their present states predict accelerating expansion so my vote is to dump both.
Nickesponja t1_iwj0tnw wrote
> For four decades and counting, scientists have failed to detect the dark matter particles in terrestrial laboratories
This is irrelevant because ΛCDM doesn't say that dark matter is made of particles. It could be, of course, and particle physicists would very much like that, but it's not a necessary assumption to explain our observations.
Giggalo_Joe t1_iwgu1qe wrote
Scientists must learn to accept the possibility of the very simple conclusion, that Einstein was wrong. Logic states that we do not know all the physics that exist in the universe. And that very likely in order to understand the universe we will have to rewrite many of out existing theories to accommodate what turns out to be reality. We would very likely have made much more progress with physics by now if instead of trying to get the data to fit our scientific theory, instead working to create new theories to fit the observations. But any alternative theory of science that even hints that Einstein was wrong is cast out as laughably wrong in the modern academic world. Unfortunate.
Shumina-Ghost t1_iwh2e7r wrote
I suppose healthy skepticism is prudent, but hasn’t Einstein been largely proven correct? Like every time?
Ok_Meat_8322 t1_iwhfpsq wrote
>hasn’t Einstein been largely proven correct? Like every time?
Like, every single mother effin' time, even after almost a century.
[deleted] t1_iwh7wbb wrote
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Giggalo_Joe t1_iwhs43e wrote
It is called the Theory of Relativity for a reason. It's unproven and unprovable. The downvoting only serves to prove my point. Blind devotion to anything is bad. What sound more logical, that physics is a vast and complex thing, many pieces of which we don't know and can't know yet, or that one guy figured out most of it's inner workings only a few hundred years after we decided that the Earth was not the center of the universe? Challenging our theories is one of the most important things we can do. If you want to devote all your time and energy to attempting to make the facts fit Einstein's theories, go right ahead. There are lots of things in physics that don't add up and we have created special rules to deal with them. Until you have one theory that can unify all physics, on all levels, from subatomic, to celestial, you will have a flawed theory that is at least a little bit incorrect, no matter what name you give or how much it helps us understand the universe around us.
vrkas t1_iwhwk0i wrote
> It is called the Theory of Relativity for a reason. It's unproven and unprovable.
General relativity has made predictions which have held up under a century of scrutiny. It breaks down as you get to very small distances but people are working on it.
>Until you have one theory that can unify all physics, on all levels, from subatomic, to celestial, you will have a flawed theory that is at least a little bit incorrect, no matter what name you give or how much it helps us understand the universe around us.
You've set a high bar, probably impossible. I think every physicist knows that we can't explain all phenomena at all energy scales and distances in a unified way, and I hope that no one is claiming that Lambda CDM is the theory of cosmology. But there is a lot of value in effective theories which are useful in some range. Like Newtonian gravity is sufficient to do space exploration, the Standard Model of particle physics is sufficient for running large scale experiments.
Giggalo_Joe t1_iwi9mob wrote
That's the point. Even a thousand years from now or ten thousand, we likely won't have all the answers. And an answer is not right if it is even 1% wrong. That's why it's important to never try to prove the theory, but create a proper theory to fit the facts. We should never be saying 'time does this near the speed of light', we should be saying 'we believe time does this near the speed of light based upon the current available theory and information'. Going back to the original post topic, dark matter may not exist...eventually you have to start looking at the theory as the problem.
vrkas t1_iwiasis wrote
OK great. I'm not sure what your actual point was then? Do we just abandon physics because we can't develop GUTs which explain everything?
Giggalo_Joe t1_iwihe3e wrote
No. We stop trying to make the data fit the theory and instead start asking why the data doesn't fit the theory. And what always has to be an option is, change the theory.
Nickesponja t1_iwj087t wrote
> We stop trying to make the data fit the theory
> change the theory
These two are the same thing. When scientists try to "make the data fit the theory", they are changing the theory, not the data. Obviously. Because the data is what it is.
Merfstick t1_iwjahd9 wrote
FWIW, you're probably not being downvoted because you're challenging Einstein and there are blind devotees in this sub. You're probably being downvoted because of the pretension and lack of self-awareness. The inclusion of "logic" in your reasoning is a dead giveaway, and you've constructed quite the strawman narrative about how Einstein is being perceived. I don't think even he, nor most serious cosmologists, would say he had it all figured out. He died refusing to accept that "hidden variables" weren't at work with QM, which is largely accepted, and few still hold on with them, so he's quite clearly NOT perfect, and NOT understood as such... by anybody but your hypotheticals (and perhaps people largely ignorant). That right there shows you're reasoning with some constructed Einstein that isn't quite true to how the rest of us understand him, so from there the "logic" is flawed.
Beyond that, what is the rule saying he couldn't, within a few hundred years, get it right? I'm sorry, I didn't realize there was a speed limit to these things. No, the proof is in the pudding, and the reality is he was pretty damn good at figuring it out, regardless of how far in time he was from heliocentrism. Those theories just so happen to have predicted objects and processes that have since been observed all on their own, so they're good enough for that, and that is what makes these so hard to discard, particularly when those other theories cannot do the same.
I honestly don't know what point you're trying to make. It's not as if something else has come along and done it better, and this is just some political or egotistical resistance. Literally anybody can wax poetic about dogmas, but the more work you actually put into proving said dogma is wrong (and/or seeing all the reasons why that dogma is powerful in the first place), the more humbled you'll be.
I know enough to know when someone actually has a grasp on physics greater than mine... and I can tell you're firmly in my league when it comes to this stuff - and I know next to fuckall about it. This is why you're being downvoted. It's not a pro-Einstein conspiracy or knowledge industrial complex which somehow implicates us all... It's you out of your element. Logically, which is more likely???
Giggalo_Joe t1_iwlo7m4 wrote
Logically, I say have a great day. #cheers
InTheEndEntropyWins t1_iwh5sxl wrote
>We would very likely have made much more progress with physics by now if instead of trying to get the data to fit our scientific theory, instead working to create new theories to fit the observations.
The greatest criticism in physics is around the focus on String theory, which is is some kind of new theory trying to fit the observations.
We already have the core model which works for pretty much every experiment ever done to remarkable degrees of precision.
Surely science should be evidence based. Theories that are accepted are ones that match experiments and observations, rather than ones that are simply nice mathematically/philosophically?
Giggalo_Joe t1_iwhur4g wrote
In simplest terms, String Theory is wrong and a fools errand. Folks will give up on it eventually. Einstein was just a guy, a normal guy, with a decent theory. But he had an inkling he was on to something. It was decades before he really had any significant evidence to support it. For all the credit we give Einstein, he was trying to solve the math associated with gravitation for a decade and he couldn't. Hilbert and Schwarzschild both solved pieces of it with little effort before Einstein published his own answers after years of trying, and one of those guys did it while fighting WWI. Anyone who tries to claim Einstein is anything less than a god immediately gets shouted down in physics. He did some great things, but its time to build some new theories (that are not string theory). Remember, even Phlogiston theory was accepted science until it wasn't. I feel the critical flaw in Einsteinian physics is the idea that time is relative. Yes, critical to Einstein's theories, but the distinction that should be made a some point is between the 'perception of time' and 'actual time'. Some would say, what is time beyond what we can observe? Ultimately, that question makes as much sense as what is the world beyond what I can see? Time is real and absolute. Provable? Observable? Hard to say.
[deleted] t1_iwh0atf wrote
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[deleted] t1_iwh0di0 wrote
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InTheEndEntropyWins t1_iwh1l2i wrote
It's just that this sub practises philosophy which is closely linked to reality. It's an evidenced based approach to understanding things.
koloquial t1_iwh2aac wrote
There are many things we cannot know, that’s part of the fun and challenge of philosophy. Not everything is material and examinable.
InTheEndEntropyWins t1_iwh6b26 wrote
I don't understand? Say we are talking about apples falling from a tree, we have the observations and theories around that. Why would I ever care about some philosophical idea about apples actually falling upwards because that theory is fun and challenging of philosophy?
When it comes to physics I only really care about reality, proper philosophy should help us understand that reality.
[deleted] t1_iwh94bi wrote
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InTheEndEntropyWins t1_iwhbhc5 wrote
I still don't understand. Doesn't this example then show that sure do your meta physics but don't every try and say that ideas apply to the real world of physics.
Aren't you saying, philosophers should keep their noses out of anything to do with the real world.
I'm happy either way, but when someone does some lsd and some metaphysics, they need to remember they are doing metaphysics which doesn't apply to reality.
The issue is when a philosopher does some metaphysics that doesn't' apply to reality and then for no reason thinks they have some deep insights into physics and reality.
edit: going back to the article it's like, I got this nice theory MOND from a philosophy point of view, it doesn't at all match up with reality and observations, maybe the whole idea of physics and reality is wrong.
koloquial t1_iwhgvtu wrote
I keep getting downvoted in this cancerous sub . Just google basic or advanced thought experiments. Also read the definition of metaphysics — there are some things that physically cannot be tested and we must use logic and thought experiments to make headway.
InTheEndEntropyWins t1_iwhhxqv wrote
I still don't understand how thought experiments which contradict with reality can be more useful that thought experiments which line up with reality.
koloquial t1_iwhj2yk wrote
If you can physically test something, there’s no need for the thought experiment. Google it, or I guess I can google it for you
InTheEndEntropyWins t1_iwhjsi1 wrote
Isn't that the whole point. We should concentrate on ideas that line up with physical experiments. We don't need thought experiments on ideas that contradict results from physical experiments.
InTheEndEntropyWins t1_iwh4y48 wrote
I'm soo confused why they keep talking about the standard model in relation to gravity.
From wiki the standard model covers forces "excluding gravity in the universe".
Carroll uses the term core model to combine the standard model and GR.
In terms of detecting dark matter, isn't that in line with our predictions. If we predict there is very little dark matter in the solar system and that it would be extremely hard to detect, it seems like not detecting it is perfectly in line with predictions.
I don't know why they are framing this as a science vs philosophy thing. Dark Matter and MOND are both scientific theories.
I think the main issues is that MOND by itself simply doesn't explain everything we see. So last I herd was that the only feasible MOND theories left were "MOND + dark matter" theories. I wasn't even aware that there were any major theories that didn't include dark matter of some kind.
So since the article is based on science vs philosophy. The scientists are taking their view and position around the "core theory" simply because it does a good job at explaining observations, MOND by itself just doesn't mesh up with all the observations we have.