“Oh leave the Wise our measures to collate. One thing at least is certain, light has weight. One thing is certain and the rest debate. Light rays, when near the Sun, do not go straight.” -Arthur Eddington
While we know full well today that Newtonian gravity is just an approximation to a more correct theory of gravity, you've got to remember that for over 200 years, it was unchallenged as the science that explained the entire Universe. When a simple puzzle -- the orbital mechanics of just one of the planets -- failed to line up with its predictions, it was assumed there was a problem with the Solar System, not with the law of gravity.
Image credit: Wikimedia Commons user WillowW, using Blender.
But when Einstein put forth General Relativity, he not only explained Newton's laws as a special case, and not only explained this orbital curiosity that Newton couldn't, he made a new prediction that differed from Newton's: that light, when it passed near the Sun, would see its path bend!
Image credit: NASA / Cosmic Times / Goddard Space Flight Center, Jim Lochner and Barbara Mattson, via http://cosmictimes.gsfc.nasa.gov/online_edition/1919Cosmic/theory_pred….
On the 96th anniversary of Relativity's confirmation, come get the story of how we learned this amazing fact about the Universe.
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I have a strange word association with this particular piece of history. That word is 'elegant'. Strange I know, but let me explain.
E=mc^2 is the epitome of elegant. So few characters with so much meaning for the universe. It is perfect in its simplicity, and has been tested countess ways with a perfect record of success.
This situation is a reminder to me that elegant doesn't mean correct. Not all elegant formulas are E=mc^2. Newton's formula here is cleaner than Einstein's, but Newton's isn't right.
Flash forward several decades to when Stephen Hawking introduced the Bekenstein–Hawking entropy formula. Again, an elegant formula. Many used its elegance in support of its correctness. Is it right? I don't know. That stuff is way over my head, but some very smart people have looked at it and said it was right.
It is just that this Newton vs Einstein episode is a little voice saying "elegant doesn't always mean correct".
As much as E=mc^2 looks elegant, it also strikes me as "too simple to be useful".
Because in mathematics, if two things are equivalent, you don't give them two names, you use just one name for it. So taking the above equation, why talk about "mass" at all if it is just energy times a constant?
Well it isn't. Particle physicists have long re-coined the word "mass" as having the meaning of "rest mass". And then E=mc^2 is obviously wrong in all but the rest frame of a particle. This can be easily seen because the lhs is a component of a four-vector while the rhs is a scalar. Correct is E^2=mc^2+p^2c^4.
This may look less elegant but if you like beautiful notations, you order the vector components to one side and the scalar to the other, take natural units where c=1 and use the four-vector p^mu=(E,p), introduce the metric tensor and write g_(mu nu) p^mu p^nu = m^2. And it is elegant again, and this time meaningful.
typo correction: Correct is E^2=m^2c^4+p^2c^2.
"As much as E=mc^2 looks elegant, it also strikes me as “too simple to be useful”. "
Well, given it showed us atomic power and how the sun manages to burn 4 billion years later, it was quite useful.
If you're a particle physicist, it's not that useful, agreed, but that isn't everyone.
If you believed that were true, you wouldn't have posted this:
Fake humility is annoying.
Fake humility hiding ignorance is toxic.
I prefer the simplicity of 0 &1 myself.
Wow, your comments on here are toxic. Not a day or article goes by that you don't belittle someone for their comments on here, and lately it's usually been Denier.
Do you have such a terrible life at home that you must come bully people around on Ethan's blog? You're smarter than most of us, I get it, but you don't have to be an ass about it.
I'll take Michael Kelsey's comments any day over your pompous, arrogant, and condescending comments.
And your comment is absolutely justified, right,AC? No mean spirit in that, nosiree!
In short, piss off you mealy mouthed whiner.
@Wow #5
If my claim of ignorance being a fake cover for my ignorance is toxic, what would that make a claim of ignorance as a cover for a fake claim of ignorance that was in itself a fake cover for my ignorance?
Would that be anti-toxic? , (2 * toxic)?, or toxic^2?
"If my claim of ignorance being a fake cover for my ignorance is toxic"
It is.
When you put your mind to it, you can work things out.
Maybe WOW has grown tired of the sophists trying to refute hundreds of years of known science with their own inane theories, spiritualists trying to shill the latest new age nonsense off as science, and out right deniers of easily confirmed scientific fact polluting this blog with their bullshit day in and day out?
I know I am. If your ideas have no basis in reality, or you outright deny reality than you do not get to pass off those ideas as equally valid as ideas that are backed up by the data that has been combed through in thousands of hours of drudgery by hard working men and women that chose to work in a field that rarely says thank you for their efforts.
So yes there are some that post around here that should piss off. Ethan could do the blog a favor by realizing that not all debates start on equal footing and wield the ban hammer a little more vociferously.
"and wield the ban hammer a little more vociferously."
Well, he prefers to use this thread as the dump for that sort of crap or someone who refuses to listen:
http://scienceblogs.com/startswithabang/2012/09/23/weekend-diversion-yo…
Which generally works.
But Chelle refused to remain in that thread and refused to moderate their insistence so got banned.
riomar9 has been even more batshit crazy than Chelle, and refusing to fuck off, but AFAIK, he hasn't been banned yet, which is disappointing.
I didn't think that thread would work, but it does better than I expected.
Could we make an analogy with dark matter?
Some prediction of contemporary physics fail. This could be explained awat by:
(1) unobserved objects (dark matter)
(2) a modification of the laws of gravity (MOND)
(3) a whole new physics
Just as back then, physicists opt for option (1) but couldn't option (3) be the good solution? The only difference is that this new physics is not yet available to us...
Quentin, #3 is a big ask. It has to answer the questions of the standard model PLUS answer the effects covered by dark matter in a better way.
If it doesn't answer it any better, then there needs to be a differentiator to say which one applies.
We know it won't work with #2 as the only answer, since we see some clumping in the effect (gravitational lensing) which MOND entirely fails to answer.
So at the very least SOMETHING dark matter is there.
The search tends to follow only a single "event" merely because of Occam. And, at the moment, dark matter sufficiently answers with appropriate fitting.
The others don't manage even WITH fitting to work as a sole solution.
@Wow it's not such a big ask. We *know* that if there is an accurate physical theory of the world, it must account for the standard model and for the effects of dark matter, and we *know* that our current theories are not the final word on this (because we don't have quantum gravity). All that (3) is asking is that our future theory of quantum gravity will actually do away with dark matter instead of confirming it, and that retrospectively, dark matter will be considered a failure of our current models of gravity. Due to the similarity of the current situation with that of the 19th century I find it very plausible indeed. You'd say that Mercure was an isolated anomaly, not dark matter, but we'd have found more if we had the technology to observe more phenomena in the universe, and without general relativity on the market, we could have well speculated "dark planets" to solve all the anomalies.
I understand perfectly that in the current situation, without a new theory of quantum gravity, dark matter is the best way to go (I am not pretending to give advice to the physicists). Just speculating on the future of science, and saying we shouldn't take current theories too seriously when it comes to patching anomalies with ad-hoc hypothesis, especially when we know that our current theories are not the final world on the question.
Yes it is.
It's a HUGE, MASSIVE, ENORMOUS requirement. The standard model fits so many things that weren't predicted or seen before the model showed their features.
You are pretending that "a big ask" means "no evidence we need it".
It doesn't.
You're pretending "I know it needs to explain current reality as well or better" is somehow making it not a problem to do that.
Well, just SAYING it is pretty damn easy.
Do it.
Tell us how easy it was after, OK?
@Wow you don't get my point. I am not talking about the difficulties of knowing that (3) is the case but about the a priori plausibility that (3) is the case. You're saying it's a big ask to prove that (3) is the case (to find such a new theory) and I fully agree, but what I'm saying is that it's not a big ask to envisage seriously that (3) is actually the case, as a matter of fact (i.e. that a more complete theory of gravity, whayever it is, would do away with dark matter) and that dark matter is kind of the new Vulcan, and I mean not merely envisaging (of course it's not a big ask to envisage anything): I mean that (3) is not less plausible a priori than (1) or (2) and that's the one we should bet on. I don't need to develop a theory of quantum gravity to bet on (3) on a priori grounds. That could be a lesson from history, especially the part of history told in this article, that we should not take hypothesis aimed at saving the compatibility of our theories with observation too seriously.
"@Wow you don’t get my point. "
Unfortunately for you, I do. 100%. And it won't work.
"Oh, the science is wrong, maybe something else will work" won't cut it, dear.
Actually specify and work out yourself what that something else IS, and then come back with how low an "ask" it was.
Until then, you're entirely negative screed is being consigned to the anti-science bullcrap bin.
(3) is very much a very difficult proposition, far more than either (1) or (2). If you don't believe me, try it yourself.
Hell, (2) is so far failing as the answer. And at least people are actually TRYING to work it out.
Your (3) is not even at the "pulled out of ass" stage.
And before you bullshit passve-aggressive about "keep an open mind",
You've *presumed* "it" would work, without even attempting to specify what "it" is.
@Wow sorry but I think your comments are confused. I'm not saying "science don't work" am I? It's not anti-science to say that hypothesis are not all here to stay and might be replaced by better ones- to the contrary I would say. You seem to be on the dogmatic side on this.
You failed to provide any good argument against (3) so far. I don't understand why the difficulty of the task is any more relevant than a place being under public light so as to make research easier is relevant to the hypothesis that it's where I lost my keys, so your argument seems irrelevant to me.
Just to clarify: my initial question concerns the a priori plausibility of the following conjecture: "our future theory of quantum gravity will do away with dark matter". No less, no more. I find the conjecture plausible, on the basis of the history of science. That's it!
Perhaps there are good arguments against this conjecture and I'd be happy to hear them, but yours are not. ( It seems that you're not trying to refute the plausibility of the conjecture but to prevent me from simply formulating the conjecture from the start. Why? The sentence is not meaningless as far as I know?)
Concerning (3) not being working on: do you think Einstein was trying to solve the Mercury trajectory problem? (Answer: no he was not, he was attempting to make electromagnetism and mechanics compatible). Lots of people are working on quantum gravity these days (they're trying to make quantum theory and general relativity compatible).
So again, since obviously you misinterpret my position, I am not saying that scientists *should* work out a solution to dark matter along the lines of (3). It's probably not the good way to proceed and dark matter is fine for the moment. I am only speculating that in the end of the day, that will be the correct solution. But I also think we'll reach the solution by other means (by developing a theory of quantum gravity). I don't understand why such speculation informed by the history of science would be anti-science or whatever.
I specified what *it* is more than once: *it* is our future theory of quantum gravity. You don't expect me to develop the theory in this comment thread do you? That doesn't make the conjecture meaningless. I can talk of general relativity and formulate a conjecture about it without having to specify the detail of the theory, without even knowing them. So much for our future theory of quantum gravity.
I won't continue the discussion very long if you keep on with that tone. If you don't find my question interesting, don't try to answer it.
You're not saying what "it" is.
Read the Jefferson quote.
And check up on urban dictionary "JAQing off".
I'm not confused. I'm not buying your bullshit.
"You failed to provide any good argument against (3) so far."
You haven't provided a (3).
I clarified (3) in my last comment in the form of a conjecture. Do you understand the conjecture?
I'm not "jaQing off". You might spend too much time on internet forums to take my question seriously. I'm not coming with an anti-science agenda.
I thought someone on this forum could inform me for example by giving arguments to the effect that dark matter is still very plausible even from the prospect of a unified theory of quantum gravity and that therefore my (3) is implausible.
To be clear my question is philosophical: should we believe there is really dark matter in nature? I think the answer is no.
This is independent of the scientific question: should we use dark matter in our models and attempt to figure out what it is under the current theoretical framework (the standard model)? Should we make experiments to figure it out? To which I would answer yes, definitely. If we succeed my conjecture will be refuted, I'm fine with this.
So no I'm not " jaQing off" and I'm not being anti-science. Don't confuse the philosophical question and the scientific question.
Still no "it".
Come back with an it. Or be ridiculed. Your choice.
I think I know who is being ridicule.
Quentin: I clarified (3) in my last comment in the form of a conjecture.
Conjecture (defn) : form an opinion or supposition about (something) on the basis of incomplete information.
But your claim was, and I quote:
Aaaand now it proves not even you can be arsed working out what you're saying.
So why the hell should anyone else give a flying fuck what the hell you're blathering on about here, when not even you bother with it?
You are JAQing off. And being really shite at it.
Why? Who the hell cares.
Accusations of what? Tell me.
Poincaré, Riemann or Hilbert would have been happy to hear that emitting a conjecture is "not being arsed working out what one is saying". You're brilliant.
Sorry I have to leave but thank you for the discussion. Really enriching. Now I know much more on the prospects of the dark matter hypothesis in future quantum gravity theories.
If you don't have anything to say on a subject, just don't.
@ Quentin
concerning Dark Matter.... Quantum Gravity in whatever form or theory it may arrive in, needn't disprove dark matter. It might, in some specific scenario, but just as likely it might give further proof that it's there.
The reason why Wow get's pissed of most of the times is a sentimental statements like.. "i don't like how XY is.. there are missing things in our understanding, and once YZ theory arrives, it will show that XY doesn't exist"... This statement isn't scientific.. and forcing it further as a valid scientific argument leads nowhere.
Instead try a different approach.. spend some time on wiki.. then on arxiv.. and then post here and say.. ok, I've read this, and this.. and it seems to me that this could work to negate the need of dark matter.. is this view valid or did I miss some things.. and everyone with relevant knowledge in the field will try to point you in the right direction.
There is nothing wrong in doubting if dark matter is actually an undiscovered particle. But it needs to be based on valid theories and it mustn't conflict with existing things we know are correct.
@Sinisa
Thank you for your comment. Don't find excuses for Wow, this kind of behaviour is the plea of internet forums and I wish a moderator intervened.
I am not forcing anything, I am not being sentimental, and I think your advices are a bit underevaluated: although I was trained in physics as an undergraduate, if I were to make substantive advance to the field, reading arxiv wouldn't be enough: I'd probably have to do a PhD and a couple of post-doc before (then maybe if I'm lucky at the end of my career...) ;-)
What I mean is that I'm not pretending to make a scientific statement. I only want to draw attention to an analogy between the situation of 19th physics and contemporary physics, and make a layman conjecture, and I'd be interested in the opinion of working physicists (or others) on the subject: do they think the situation is analogous or are there important differences? I am interesting in the history of science and the implications for the layman's commitment to contemporary scientific theories and hypothesis. That is all.
Now saying that I need to work out a theory of quantum gravity in this comment thread to formulate my question meaningfully and get some feedback (that is, answer my own question before I'm allowed to ask it!) is all but productive. I need not have a PhD in physics to discuss the status of physical hypothesis from a history of science perspective. My opinions are certainly not as valuable as that of a working physicist on the subject, that's precisely why I'm asking and hope some informed feedback. Wow could have simply said (as you did): I think we can't really answer the question before we have this new theory, only the future will tell us (which I think would be his opinion if he were to express it depassionately) or dark matter will probably still be there in future theories because x and y. That's perfectly acceptable to me. Instead he decided to try all his best to ridicule me at any price (as if it was the goal of any discussion on the internet to "win"), and accused me of being anti science for no particular reason. You might share his opinion, but I find the attitude despicable.
"I am not forcing anything"
Yeah, but you're not JAQing either! LOL!
@Wow please come back when you're able to discuss.
http://existentialcomics.com/comic/9
" Instead he decided to try all his best to ridicule me at any price"
Yep, usually happens when he forgets to take his Thorazine.
"discuss."? Discuss what? You said fuck all, kid.
Come back when you've *said something*.
Moving your noise hole isn't discussion, not even for kids like you.
@Quentin #33
ROTFLMFAO!!!! That is Classic and OH So Fitting for Tweddle Dope Puppy Loveless
haha
Thanks That had me rolling.
Ah, so you're the sort of idiot that clicks on links no matter what.
Run Windows and IE too, hmm?
Did you open it?
"Is it plausible that scientific hypothesis X will turn out to be false in light of future theory Y, just as hypothesis Z did in the past?"
"Working out Y is hard."
"Yes, but is it plausible that X will turn out to be false when Y is worked out?"
"Arr heretic! JAQing off! JAQing off! see? I ridiculed you. Discuss what?"
Oh boy...
Yeah, that's what I said.
So, got us any "it" yet?
Yes: Quantum gravity
Back in my second comment FYI
@ Quentin
I'm sorry if you misunderstood me. I was not saying you should build your own theory or working model in the comments section, nor that you need a PhD in theoretical physics in order to have a discussion here. I don't have any degree in physics.
What I was saying is that you need to put some evidence or cite some sources (relevant, peer reviewed sources) if you want to have an honest debate about serious problems in theoretical physics or astrophysics, because 99% of the people who do have a PhD in astrophysics or similar and who have spent their lives trying to find an alternative to DM, have so far failed, and the major concensus is that it's real.
instead you say :"my initial question concerns the a priori plausibility of the following conjecture: “our future theory of quantum gravity will do away with dark matter”. No less, no more. I find the conjecture plausible, on the basis of the history of science. That’s it! "
Others, and myself included, have stated that just because you find something plausible based on NO scientific evidence, doesn't make it real. Historia est testis temporum, lux veritatis, vita memoriae,... is true.. but it's not science.. physics deals with observables and calculating predictions... not on historical plausability.
That doesn't mean that in 2 or 200 years the view will stay the same about DM. But there is also no evidence that it will have to change.. i.e. electricity is just as real today as it was 200 years ago.. sure, we know much more about it today then we did back then... but no new theory made electrons disappear...
And as you tried to tell him before (and me too), there's bugger all reason why any changed theory would remove dark matter.
MY major gripe with the timewasting moron is his "'it' could mean that ...blah blah blah". What "it"? It could be "invisible pixies". They're an "it". And no, they wouldn't be real either.
So just coming back with "No, it couldn't" is 100% as useful as the dipstick's claims. All *I* mean is "it" being "invisible pixies".
If the yardbroom can't be bothered to limit what "it" could be, why the hell should I pick a useful "it" for him?
What about quantum gravity?
How does it remove the need for some conglomeration of matter being required to cause the lensing effects as if there were intervening condensed matter between us and the object being lensed?
It doesn't.
@Wow
#44 Are you seriously considering that invisible pixies could be part of our future theory of quantum gravity? If so well yes, it could do the job but I am a little skeptic. So no my "it" cannot be anything of course: it is (I repeat) a unified theory of quantum gravity.
#45 Was it an.... argument??? OMG! You can do it!
Now shall we discuss? Could the lensing effect be the result of an unknown gravitational effect (under a new theory, by analogy with no planet being responsible for Mercury's trajectory)?
Or is there a particular scientific reason why it's implausible in this case and an intervening matter is a better candidate, even in a new theoretical framework?
@Sinisa
I disagree with you on the role of history of science.
You're right that most people in astrophysics failed to find an alternative to dark matter, and that's good reason to believe that dark matter is real. However I would add "in the current theoretical framework" to all clauses of the sentence. As far as I know, string theory or loop quantum gravity are not yet developed enough to make predictions concerning the phenomena addressed by dark matter (although I might be wrong on this? I'd be interested if someone has information on this question).
I would say that this "no alternative were found" argument should only convince us that dark matter is the best option *in the current theoretical framework*, but not that it's here to stay after the current framework is replaced by a new one.
Now of course some theoretical entities get carried over in theory change (such as electricity as you observe), and other disappear (such as newtonian forces).
Are there reason to believe that dark matter will be carried over? Perhaps but another argument that "no alternative has been found" is needed to convince us I think.
That's where things can get more philosophical, and that's where the history of science can become informative. Back in the 70's, some anti-realist philosophers of science thought that we should not believe that the content of our theories is real, because all theories are doomed to be superseded by better and completely different ones. It seems counterintuitive, because science seem to progress and as you observe, some aspects such as electricity get carried over in theory change. It seems very doubtful that there will be no electron in future theories.
However other realist philosophers argued, convincingly in my opinion, that (at least) we have good reasons to be realist about the aspects of theories which make new, unexpected predictions (just as general relativity and the lensing effect).
The argument is that when an hypothesis is added just to fit a particular phenomenon, then one can remain skeptic, because the hypothesis is kind of ad-hoc. It works because it was designed to do so. But when an hypothesis makes new unexpected predictions it was not designed for and that these predictions are later confirmed, then it would be a miracle if the hypothesis had not captured an important aspect of reality.
Generally, well accepted theories make a lot of such new predictions, and that convince the scientists themselves to accept them (again, the lensing effect is an example).
Going back to dark matter: I was thinking that perhaps this criteria of novel predictions could be used to speculate on whether a particular hypothesis will be carried over or not. For example, vulcan never did novel predictions (the case of newtonian forces is a bit trickier though...). If an hypothesis makes novel predictions it was not designed for, then one could think that it's very plausible that it will be retained in future theories, or at least some important aspects of it.
So I am wondering: does dark matter make new predictions it was not designed for? If so could you give examples? I'd be very interested.
"However I would add “in the current theoretical framework” "
How the hell would you know it's only in the current theoretical framework, or that under ANY other system it wouldn't be there at all?
You make claims out of your own ignorance as if somehow they must be accepted merely because the chance isn't precisely 100.00000% against it.
This is bollocks.
Come up with a different framework and find out if it removes dark matter.
Don't piss about and pretend that there must be one out there.
"#44 Are you seriously considering that invisible pixies could be part of our future theory of quantum gravity?"
Of course. That's exactly what I said,I said "Seriously, pixies exist!!!!".
You didn't read a fucking thing, did you, you cretin.
"Now shall we discuss? Could the lensing effect be the result of an unknown gravitational effect "
No.
Just decided to check this page out, and even though I’m not really interested in this particular topic, it’s still very interesting, but one thing I was really surprised about was, how some of you are saying an alternative to dark matter should be looked for, or found. Well, you can all stop looking for an alternative to dark matter; instead start focusing on the medium to medium dark-brown matter. It has been appearing everywhere, as I, and many others have already discovered, and it all has to do with the inability for the universe to create or dissipate any of the regular dark matter that’s very much talked about. Even though the medium dark matter is not necessary, it nevertheless, and regretfully, appears everywhere. And, since it can be more visible than the dark matter, that’s why this other new, still unknown, and utterly misunderstood force/energy, took it upon itself, to begin the dispersion, or the activation of that brown matter, and for it to actually be seen, and, so now, it’s all around us. That’s why, fortunately for us, (and I know you’ve all noticed it also) don’t really have to be very keen at trying to perceive it, and one also doesn’t even have to worry about measuring it at all, for it can be easily seen, detected, and even smelled, just as one can detect and smell the ozone, after a good rain. Unfortunately, the odor of this matter is deleterious, just as the fumes from hydrochloric acid are, but only if one is not at a safe distance from it, and properly protected from it with proper anti-matter attire, as has already been found. Many have suffered tremendously from it, that, they have had to run out from wherever it is they detect it, to never return, and even Ethan and Ragtag, and others have known this for a while, but they don’t really think too much about it. It has also been found that, all that’s needed to be done is, to shield oneself from it, and we can even defend oneself from it by simply ignoring that dark matter, cause, if you pay too much attention to it, you might get cacaytioned by it. I’m talking about the Atomic Shit Bomb papi Lovless, who goes: “Cacaboom!,…and spreads all his brown matter all around, on most everyone who comes or goes to whichever page they wish to go to, to express their views or opinion and such. He’s a very intelligent, but also a very, very angry puppy who really sounds like a freaking 7th grade punk bully, who just tries to intimidate everyone with his rants, by exploding on everyone, everywhere he shows up. He did that even after my very first post. So, again, stop looking for an alternative to dark matter…it’s here already…WOW!!!! Cool it already man. You sound like a real lunatic, and you should know better. Debate all you want, but be cool about it, because it looks like you’re the only one who goes off on everyone else. Chill out so we can love you. If you read this Ragtag, and if you don’t mind, go to the Rock Remember and so do we, page. There’s a couple of vids I would like you to check out when you have time, and again, if you don't mind?. Have a great day/night everyone!
"How the hell would you know it’s only in the current theoretical framework, or that under ANY other system it wouldn’t be there at all?"
I know that no alternatives were found *under the current framework* because it's the only framework we have today.
Read carefully.
Nope, you only know it's in the current framework retard. You don't know it's ONLY in the current framework.
And there were two queries there you quoted. If you're going to quote both, why only (fail to) answer one?
I know it's *only* in the current framework that we did not find any alternative to dark matter. Read.
No, you don't know it's *only* in the current framework. Another framework can include dark matter. It's in quantum gravity: it cannot explain lensing without it.
@ Quentin #47
"I would say that this “no alternative were found” argument should only convince us that dark matter is the best option *in the current theoretical framework*, but not that it’s here to stay after the current framework is replaced by a new one."
- again, there is no evidence that it will go away.. it's only your own bias that gravitates to it going away. Yes, dark matter is just a placeholder name for now.. it might turn out to be some neutrino flavor, or combination of different matter forms or it might be some undiscovered particle etc... In fact, based on current evidence, I would argue there is a much greater chance that it is actual matter and not modification of gravity.
"Now of course some theoretical entities get carried over in theory change (such as electricity as you observe), and other disappear (such as newtonian forces)."
- there is nothing theoretical about electricity, it's physical, it's real. As for Newtonian forces.. they are very much alive and well even in 21st century. All of classical mechanics.. which is more or less 90% of your everyday life is based on newtonian forces. Even for space... satelites, probes, etc etc.. all are calculated by newtonian physics. Relativity only comes to play as you approach "c". Or in cases of very large masses. Further.. relativity in classical domain, gives same result, and in fact gives the same formula as newtonian graivity... it has to.. otherwise it wouldn't be a valid framework. You see, it's not so much a revolution.. it's evolution.
"So I am wondering: does dark matter make new predictions it was not designed for? If so could you give examples? I’d be very interested."
- I'm not sure I understand what you mean, or even that it means something. Dark Matter is not a theory, in other words, it's not a mathematical model, just like electron is not a theory and electron doesn't make any predictions. Standard model does, or maxwell's equations do.
Dark matter is just a placeholder for a type of matter that only interacts gravitationaly.. so far as we know... Will quantum gravity be setup in a such a way that it eliminates the need for it... I personally don't think so, since the evidence for DM is not only in galactic rotation but other sources as well (search this blog for articles on why we think DM is real, Ethan has written several good articles on the subject.). I can see modifying gravity so it mimics galactic rotation curves (as MOND does).. or getting bullet cluster like effects.. but there are 4-5 different sets of phenomena that need to be covered, as well as not changing any of current results for testable predictions.
Quantum gravity is being developed for modes where relativity breaks (singularities). I wouldn't bet my horse on it changing anything in more moderate regimes where we see effects of DM.
@Wow what you say is unintelligible.
Compare :
- I searched only this room and did not find my keys
- so it's *only* in this room that you did not find them, you might find them in another room
- How do you know it's not only in this room that I didn't find them? My keys might not be in other rooms either.
-.... ?
"@Wow what you say is unintelligible."
No, you're a fuckwit.
Just because your ass remains unfound even with a team of Sherpas and both hands doesn't mean everyone else is unintelligible. Just that you're thicker than a light year of pigfat.
Why should I consider your statements?
You're not talking about keys.
Compare:
I haven't got my keyes, therefore there is nobody with my keys!
But you're a fucking moron, so you won't understand this either. Because you're just trolling like a twat.
@Sinisa
" again, there is no evidence that it will go away.."
The problem is that scientific evidence is relative to a theoretical framework (I can give you resources on the subject if you wish, but you could read Kuhn for example)... You cannot find evidence of newtonian gravitation forces (nor evidence of their absence) in relativity, because there is no such thing in the framework.
That's why I am looking at other kinds of inter-theoretical "evidence" or indicators in history of science, such as the fact that some entities are retained in theory change while others are not.
"there is nothing theoretical about electricity, it’s physical"
Do you mean Maxwell's equations are not a theory?
Or what do you call "electricity" if not what is described by Maxwell's equations?
We say electricity is "real" only because we think it will be retained in theory change.
You should be careful before using the term "real": it's a term of art in philosophy, not science.
"all are calculated by newtonian physics"
That doesn't mean newtonian physics correctly describes reality. It does good predictions only because it approximate relativity. Strictly speaking, there are no real gravitation forces in reality, it's an approximation of space-time curvatures.
"Dark Matter is not a theory"
I take dark matter to be the hypothesis that some unobservable matter interact gravitationally and is responsible for some range of phenomena (galactic rotations, ...). It's a scientific hypothesis. Does it make new predictions it was not designed for?
"I wouldn’t bet my horse on it changing anything in more moderate regimes "
Relativity makes small differences for the trajectory of Mercure... But Mercure is far from going at the speed of light!
It seems to me that dark matter is often involved in high distance interactions (galactic, ...). Is it the case or are there also small distance effects covered? If this is the case it could be crucial: If tiny differences in laws add up, that could make a huge difference but only at large scales.
The fact that it's a mere possibility at least refutes the idea that there couldn't be any difference in moderate regimes.
" there are 4-5 different sets of phenomena that need to be covered"
Ok that could be convincing indeed. I'd have to think about that.
"search this blog for articles on why we think DM is real, Ethan has written several good articles on the subject"
Thank you for the suggestion, I'll have a look.
@Wow
"I haven’t got my keyes, therefore there is nobody with my keys!"
That rebutts your own point right? (replace "got my keys" by "got an alternative to dark matter" and "nobody" by "no theory")
"Scientific evidence is relative to a theoretical framework (I can give you resources on the subject if you wish"
No you can't.
How do I know this? Because you have no theoretical framework in mind.
You claim there's one by virtue of the fact that you believe there is one.
Sic ergo propter hoc is a logical fallacy.
And you're 100% trolling.
Fuck off to this thread with the tired screed:
http://scienceblogs.com/startswithabang/2012/09/23/weekend-diversion-yo…
“I haven’t got my keyes, therefore there is nobody with my keys!”
That rebutts your own point right?
No, it doesn't.
"F*#@ off to this thread with the tired screed:”
The thread is for you, not me.
No, it's for you.
@ Quentin
https://medium.com/starts-with-a-bang/five-reasons-we-think-dark-matter…
"Do you mean Maxwell’s equations are not a theory?"
- you chose (deliberatly or not) to omit crutial parts of my answer.. Electron is not a theory, maxwell's equations are.. electron doesn't care if we have a model that describes it or not.. phenomena caused by it were known years before any model of how it works was presented.
"That doesn’t mean newtonian physics correctly describes reality. It does good predictions only because it approximate relativity. "
-this is just wrong. The fact that we can send a probe to mars and hit the landing zone we want proves that it correctly describes reality. It's not an approximation of relativity.. it's an approximation of reality! Same is with relativity.. it's an approximation of reality, just finer then newton. Every theory is approximation because nature is infinitely complex and you need to approximate in order to calculate the result.
"Relativity makes small differences for the trajectory of Mercure… But Mercure is far from going at the speed of light!"
-this is again because you removed the rest of my sentence.. very large masses.
Read the article I linked above and then we can continue :)
I know the the moderation policy is very liberal here. Nevertheless I would like to draw the attention of the moderator to Wow's comments #49 and #58 which are clearly insulting (see also #37, #44 and the general tone of all others).
Wow's attitude is time wasting, detrimental to the quality of the discussion on this forum and the moderator should do something about it.
Quentin, Wow can't help it, he has Coprolalia disorder.
@Sinisa
I would draw a distinction between "correctly describing" and "approximating" (in terms of prediction).
Electrons are theoretical entities, we postulate them to predict a various range of phenomena. I also think they're real entities because I think our theories (mostly) correctly describe reality, but I wouldn't say they're not theoretical.
Another example is the ether which was postulated by scientists but did not survive the change from newtonian physics to relativity. There are many examples of entities which disapear from theories (caloric fluids, phlogiston, ...) even though the theories were making good predictions.
The link is interesting. All effects are at galactic distances it seems? Is it because dark matter would be light weight or diffuse that its gravitational effects are not seen at smaller distances?
(3) (CMB) looks a bit like a novel prediction, but not completely (still the same type of phenomena).
(4) (cluster collision) is interesting because dark matter's location is apparently disconnected from normal matter's location, which probably challenges a purely gravitational explanation.
I also take note the gravitation modification is still an active area of research, so my questions are not completely off topic ;-)
The conclusion of the article is very interesting (to me) because it implies that going from "think it's 99.99% probable" to "know", we'd need a detection of a corresponding particle. A detection of new particles would be a blatant "novel prediction" of the hypothesis (because it is completely unrelated the the phenomena it was designed for, i.e. large scale gravitational effects) so somehow that confirms the relevance of the criteria of novel predictions for our commitment to theoretical entities.
@ Quentin
"Electrons are theoretical entities,..."
no.. they are real things. You can detect them, you can count them with instruments, you can use them. That's a difference between theoretical thing and real thing. There is nothing theoretical in i.e. scanning electron microscope. It's not shooting little theories.. it's shooting electrons, and it's not postulates that are scattering from the surface of the object but actual physical things. That's the difference.
It's seems to me that you are confusing what a theory means in physics. It doesn't mean the same thing as in i.e. philosophy.
Theory tries to model real things, and it does so by assuming perfect, most of the time approximate, things. There is no such thing as a black body in real world. It's an idealized thing, yet all of thermodynamics rests on it. Electron is a real thing, out theories and mathematical models we use to describe it are approximations.
"Another example is the ether which was postulated by scientists but did not survive the change from newtonian physics to relativity. "
You are making 2 big errors here. First, it was not relativity that killed aether, it was absolute lack of experimental evidence, or in other words, every experiment ever built to detect aether showed light to move at constant speed in all reference frames. That, and further work from physicists that showed light can propagate without the need of a medium. Second error is something I mentioned earlier. Relativity is used in only a very very small area of physics. In fact, outside of cosmology and particle physics.. it's not used at all... ok. GPS systems and couple of others that I missed.. Engineering, construction, electrical systems... none of them care about einstein or relativity. Classical physics is your everyday physics.. not relativity.
If you want an example of theoretical entities.. then strings are theoretical entities.. because they are used as purely mathematical models to describe something. Ask a string theorists what are strings made of, and they start turning green... Gravitons are theoretical entities because they are postulated but not detected. Supersymmetry is a theoretical postulate... and so on.
Yes, at the moment, dark matter is a theoretical form of matter until such time as it's detected.
What you're defending is known as entity realism in the philosophy of science (what is real is what you can manipulate). It's interesting but not the only position. Note that electron manipulation is very indirect, and that in quantum field theory, different observers might count a different number of electron in the same system (Unruh effect). Some think that there are no electrons but only excitation states of a fermionic field. I find the view interesting, in particular because the indiscernability of particles (permutation invariance) threatens the view that electrons are real objects.
There are also examples in the history of science where theoretical entities were "manipulated" (e.g. phlogiston).
Concerning the ether: a majority of physicists still believed in its existence after contradictory experiments, until the beginning of 20th century. There were attempts to modify the laws of electrmagntism to accomodate the problematic experimental evidence. Not very succesful, but research was going on. It's only when relativity arrived on the market that it was abandoned.
Concerning newtonian physics: one should not confuse the application of a theory and the fact that it describes reality. Newtonian physics is widely used for practical reasons, that doesn't mean it's a true description of reality (that there are really entities in nature like forces and newtonian particles).
@Quentin #68
I did recently learn of an alternate theory that correctly models at least some of the effects attributed to Dark Mater. It doesn't rely on undiscovered particles and is testable.
The theory is that antimatter falls up.
The idea is that CP-symmetry was not broken at the big bang and the universe just expanded fast enough to allow some antimatter to repel away from matter before being annihilated leaving some of both intact.
The intergalactic medium is now made up of a diffuse fog of antimatter particles that pushes out on everything. The mass of the galaxies, etc, can't fully account for observed phenomena, but it isn't because there is some extra undetectable "Dark Matter" adding to the gravitational pull but rather the intergalactic medium of antimatter adding antigravitational push.
There have been tests done at CERN to determine if antihydrogen falls up or down, but the results were really inconclusive. The researchers did observe a slight bias towards downward falling but the error bars are so large that absolutely nothing was ruled out. Here is the annihilation map from the experiment. You can see for yourself the red circles are everywhere.
This is not some crazy idea I came up with. The credit for it goes to CERN physist Dragan Hajdukovic. It has been peer review and published.
I'm not sure I buy into it but It is a fun idea to think about.
@Denier
Interesting!
@ Quentin
I didn't know about the term "entity realism".. looked on wiki and is a pretty short article, but yes.. experimental realism as a synonym works.. will have to read the whole article on scientific realism before I can continue and say what I think is or isn't. The field of philosophy of science is interesting but I admit I don't have much knowledge about it.
As for aether... sadly it wasn't abandoned.. it was by majority of people.. but even today just by searching arXiv.. you can see papers still being posted.. of course, none will be peer reviewed... and unless an experiment comes that can show otherwise, it's dead.
As for newtonian physics.. my argument was that you seemed to have drawn a line with Einstein and 20th century... saying classical physics went into retirement once relativity arrived. My comment was that that statement is only true for gravity (and EM) and nothing else. And even for gravity only in certain regimes. The rest of physics is not relativity, and you simply can't use relativity for rest of physical processes (as I'm sure you know).. i.e. if you wanted to calculate the stresses on a wall in the building.. there is no relativity formula, and spacetime curvature or speed of light are simply irrelevant. That's all I was saying.
@ Denier
I think I know what you are referencing.. I think he was even featured in Throught the Wormhole in a recent episode.
But I think it was about dark energy and not dark matter. He postulates that if antimatter had an opposite gravitational effect, that it can explain the expansion of universe. I'm not 100% certain as I've seen it couple of months ago... but 95% certain it was concerning DE and not DM :)
Here SL:
http://www.sciencechannel.com/tv-shows/through-the-wormhole/videos/does…
@Sinasi
I think we derived slightly from the initial subject so I'll stop here but it's still interesting, thank you for the discussion.
@Quentin, @Sinisa Lazarek, @Ragtag Media
When I Google Dragan Hajdukovic's name, references to both DE and DM come up. If antimatter were to fall up, it would be a game changer.
PS - Remind me not to eat any blue apples.
Yup, because the little toerag isn't here to actually engage.
Aaah fuck. Is Chelle back???
BWAHahahaHAHAHAHAHAHHAHAHAHAHAHAA!
"Aaah fuck. Is Chelle back???"
Thus Wow starts the Leg humpin, any thought of Chelle and he goes into full heat leg humping mode.
Miss her?
Aaaand Rag goes Full Retard (tm).
"Yup, because the little toerag isn’t here to actually engage."
BWAHahahaHAHAHAHAHAHHAHAHAHAHAHAA