Purported Relativity Paradox Resolved 128
sciencehabit writes "A purported conflict between the century-old theory of classical electrodynamics and Einstein's theory of special relativity doesn't exist, a chorus of physicists says. Last April, an electrical engineer claimed that the equation that determines the force exerted on an electrically charged particle by electric and magnetic fields — the Lorentz force law — clashes with relativity, the theory that centers on how observers moving at a constant speed relative to one another will view the same events. To prove it, he concocted a simple 'thought experiment' in which the Lorentz force law seemed to lead to a paradox. Now, four physicists independently say that they have resolved the paradox."
Summary of Resolution Ceremony (Score:5, Funny)
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Re:Summary of Resolution Ceremony (Score:4, Funny)
So they refrained from using their hands?
They refrained from using thoughts.
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Only to open Schrödinger's fridge [angryflower.com] for a beer.
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"omine, omine, omine"? How is that pronounced? What language is it from? What does it mean?
Sounds like the poof of smoke the physicist-magicians are using to distract you from seeing the trick.
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However, it's also possible you misheard "omine": There's the word "domine", which is vocative singular, which could be translated as "Hey God, Hear Me!" (dominus = master of the house, but due to historical misuse by the catholic church it also means the christian god).
It's good to see that ..... (Score:5, Insightful)
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This is in the range of a practise problem in special relativity, not something for a scientific paper.
Re:It's good to see that ..... (Score:5, Insightful)
Science is alive and well in at least the Physics community. Whilst I won't even pretend to understand General Relativity, the questioning of it and discussion about those questions is the true essence of science.
Sigh. General Relativity was not even at question here. Perhaps commenting on Slashdot should require a minimum amount of knowing what one is talking about. AAAHAHAHAHAHAHAHAHHAHAHAHA. Sigh.
At any rate, electrical engineers tend to view parts of Special Relativity in isolation. That makes them easier to handle and "visualize" in some respects, but much harder to deal with interactions. Minkovsky vectors and tensors are what theoretical physicists use instead, grouping several codependent field parts into one entity that can then be transformed as a whole.
So the physicists will most likely just have employed a better mathematical toolbox for resolving the "paradox". I've not actually read the original Einstein papers, but I would not be much surprised if his equations were closer to what Electrical Engineers get to deal with than what Theoretical Physicists do. Shaking out all that tensor stuff is more or less elegant wrapup work.
That sort of approach was, however, at the core of General Relativity, and mastering it took quite a bit more time for Einstein. I seem to remember that he discussed the underpinnings with Hilbert, and Hilbert came up with the general equations independently within something like a week, but retracted his papers out of respect for Einstein doing all the visionary groundwork as well as shouldering the math (though being quite slower at it than well-versed mathematicians).
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Indeed. When Minkowski reformulated it with 4D tensors, Einstein complained that he didn't recognize his own theory any more.
However, for General Relativity, Einstein had to go that path as well, and learned to love the power of it.
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Science is alive and well in at least the Physics community. Whilst I won't even pretend to understand General Relativity, the questioning of it and discussion about those questions is the true essence of science.
Sigh. General Relativity was not even at question here. Perhaps commenting on Slashdot should require a minimum amount of knowing what one is talking about. AAAHAHAHAHAHAHAHAHHAHAHAHA. Sigh.
Wow, somebody took their grumpy pill this morning. Can't a person simply point out that it's great to see issues like this being discussed without someone tearing them apart for confusing the special and general theories of relativity? By the way, I have a Ph.D. in physics. Does that make me qualified to post a reply to your comment?
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By the way, I have a Ph.D. in physics.
No. Having a Ph.D. in physics means nothing more than you have a Ph.D. in physics. It does not, contrary to what you assume, mean you know what you're talking about. Having a Ph.D. just means you did the same shit grunt work those before you did so now you've got a certificate from the Good Ole' Boys club saying you did the same shit they did. That is not science, thats Academia and while most associate Academia with knowledge, that is also silly and more often than not, wrong.
A Ph.D. means you paid you
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Bullshit. If you have a Ph.D., you've published original research papers, so you know your field as well as anyone. Sounds like someone never got theirs, but still thinks they should be considered to be in the same league as someone who did?
And yet he could have published in completely unrelated areas of physics to the discussion at hand, thus making him no more qualified for the discussion and a high school student.
Re:It's good to see that ..... (Score:5, Insightful)
You worry too much about silly shit. Some of the best and most insightful posts here are from "Anonymous Cowards".
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Why not? Moderation is done for the sake of the readers, so they can more easily spot posts which may be worth reading. This primary function of moderation is independent of someone posting as AC or not.
Moderation also has secondary effects on the posters, to encourage writing good posts. For logged-in users, it changes their Karma. For ACs, it affects the number of allowed posts that day (and probably also the time until the next post is possible) from t
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OK, this IS off topic, but it's something I feel strongly about.
When I have mod points, I follow some simple rules. I rarely, if ever, mod someone down. I'd rather mod a good post up.
I always reserve some points just to bump up an AC who does a good job. Some people post AC because they're at work or need/want to remain anonymous, not because they're trolls. (And you didn't need to lose your mod points in this discussion; you could have posted AC yourself, then said, "posting AC 'cause I have points" and th
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Not everybody here is a depressed curmudgeon.
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Perhaps the previous AC meant that science being great is a given and doesn't need to be stated here.
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Science is alive and well in at least the Physics community. Whilst I won't even pretend to understand General Relativity, the questioning of it and discussion about those questions is the true essence of science. facts ->theory->more facts->questions->revised theory. Beautiful!
Did you mean trueFacts, or goodFacts? Anything can be politicized, even physics. Humans, as a rule, don't care about "facts" when they conflict with personal beliefs. If the algorithm starts with "facts", you are setting up a conflict between trueFacts and goodFacts, which allows personal beliefs to corrupt the entire process. Let me propose a slightly different algorithm that takes personal belief out of the way of the pursuit for knowledge:
model -> hypothesis -> measurement -> failure of h
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You have to start with facts because without facts you don't even know that you have something you need a model for. You don't just invent models and then look if you can find something in nature which fits that model. You start with facts you find, and try to make a model which reproduces those facts. You generally try to be compatible with existing models in regimes where those didn't fail, so that would be the first test of your model (well, you might at the very first also do some consistency check). Th
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Starting with "facts" really adds nothing to the process, except perhaps expediency. If a model accurately predicts new measurements it's a good model. If a model accurately fits the set of known measurements ("facts") - that actually means very little! Necessary, but not even close to sufficient. That's the "data mining fallacy", and why people tend to do such a poor job at modelling the stock market.
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Without having facts, you don't even know what to model. If someone told me to model the solar system and I had no facts about the solar system, my model might look like "a=b+c" where a is the a-ness of the solar system, b is the b-ness and c is the c-ness. Of course that has nothing to do at all with the solar system. But I can't know that without any facts about the solar system.
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Perhps, in that most general sense, sure. But Newton wasn't really trying to explain a set of measurements with his reasoning about gravity - he was trying to deduce what it must be, what the most attractive model was. Unlike most of his writings, which were comically bad, he happened to be right about gravity. We don't teach the rest of his ideas because he really wasn't very concerned with facts
But mostly I was just warning of the natural inclination to prefer theories for their explanatory power (of fa
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Newton certainly wanted to reproduce Kepler's laws which at the time were the best description of the solar syst
Rationalism vs Empiricism (Score:2)
No, it's not about facts.
It's about epistemologies: How you arrive at those facts. Most scientists follow an empirical empistemology. The rest of the world usually follows a more rational one, or historical (i.e. something is true because a book says so).
A rational epistemology holds that anything that can be proved logically is true. An empiricist holds that anything that can be demonstrated experimentally is true. Some statements can be true in either paradigm, but it can make a big difference as to how y
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Actually in the context of epistemology [wikipedia.org], it means exactly what I said it means. The wikipedia article you refer to conflates rationalism and empiricism, I refer you to my previous post for an explanation of the differences.
You're also ignoring centuries of christian apologists and philosophers, scores of whom were better logicians than either of us: I may single out Descartes and Kant. Faith is an axiom, not necessarily an irrationality. The axioms of Christianity and those of mathematics may differ, but th
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Re:It's good to see that ..... (Score:5, Insightful)
And it's a healthy sign that some random guy can say, "look Special Relativity seems to be broken," and nobody starts screaming about golden idols or anything, but rather four smart guys kindly consider what he has to say and show him where he went wrong. Everybody learns something, egos remain intact, and nobody starts swinging guns. Science FTW.
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Einstein's theory of special relativity
how strange (Score:1)
How strange that even I understand the "hidden momentum" concept (I think!). Time for a car analogy:
Imagine a car driving past you. At first you're looking at its front, then side, then it rear. So the car actually rotated from your frame of reference, and at the time it was passing right next to you it had an angular momentum.
Since the car was not actually rotating, those physicists call it a "hidden angular momentum".
This electrical engineer claims that such angular momentum is just a kludge concept added
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Whenever there are any really tough questions about relativity, the world waits for an electrical engineer to comment. Unfortunately their comments are not correct.
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Well, "hunt the paradox" is a standard exercise in Theoretical Physics 101, special relativity. There are quite a number of them, and not too few involve understandings of "orthogonal" and "simultaneous" and other conceptual geometric invariants that are not actually invariant.
Electrical engineers don't go through that enfuriating and embarrassing spectacle of "ok, what did I take for granted now again" of relativity initiation.
Read original paper (Score:4, Informative)
Scroll down to "Trouble with the Lorentz Law of Force: Incompatibility with Special Relativity and Momentum Conservation", there you can get the pdf, if you have university access. Whew, it took me more than 20 minutes to find it. Why those journalists do not include the cited source?!
This paper is actually quite interesting, and I remember my ED teacher complaining about the Lorentz Law incompatibility during his lectures too. Whether "hidden moment" exists or not - maybe is a matter of performing the right experiments
And what about the proton radius problem?
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level 1 is Pir8 bouy (Score:2)
What ever means are necessary, in the quest for knowledge, the artificial imaginary made up, invisible laws made by man are just that, big fairy tales that dont exist.
Re:Back to middle ages (Score:5, Funny)
You could, you know, pay to play. Like all other aspects of life.
I hate being the one to break this to you, but... If your girlfriend is billing you for services rendered, she's not really your girlfriend.
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Really? Mine makes more than I do (she's an engineer and I'm a writer, go figure), and usually volunteers to pay for "extras" like trips to the cinema and dinners out.
I must be doing it wrong, I suppose.
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Meet an old debater's judo throw known as reductio ad absurdem. It's very effective at dispelling ridiculous blanket assertions such as that put forward by the OP.
BTW, given your keen powers of observation, you no doubt noticed that elsewhere in this discussion, I took someone else to task for equating a pay-walled article to some sort of life-and-death matter, and you were able to conclude (correctly) that I don't give a shit whether they charge to read their article or not.
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All you have to do to access it is to give them the right amount of money (or to be at an institution which does so, as for example an university).
However, these days many physics articles are also found on arXiv [arxiv.org] so it makes sense to search for the article there. And indeed, this article can be found there. [arxiv.org] The journal reference given there also makes it clear that it is really the same article.
Note that everything on arXiv is Open Access.
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Ah. Sometimes denial of service attacks are a good thing then. Locking away pure information in such a way that only rich people from rich countries can view them is so not the way for science to move forward.
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Has nothing to do with physics (Score:2, Interesting)
Since a paradox is not a feature of the Universe; it is a feature of a limited mind trying to understand the Universe.
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Since a paradox is not a feature of the Universe; it is a feature of a limited mind trying to understand the Universe.
Physics is all about understanding the universe with our limited mind.
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Heh. I was actually thinking of your sig when I posted that. :)
Open access links to actual papers (Score:4, Informative)
It's not a paradox (Score:5, Insightful)
if you forget part of the energy-momentum tensor when you transform your coordinates from a stationary into a moving frame of reference.
Special relativity really cannot "clash" with the Lorentz force law, because it is based on the Lorentz invariance of Maxwell's equations. I think a "paradox" like this keeps coming up ever so often in discussions of special relativity, form people who don't understand it. I just don't see how PRL can accept such a paper.
I admit it would make a nice problem for a physics test, but not much more.
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Simple: The referees they sent it to for peer review didn't understand it either.
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I think your position is too radical. Understanding is more than knowing what the result will be. Understanding is about - to put it in James Maxwell's words - knowing the particular go of it. And that is valid science. The twins paradox in special relativity can easily be dismissed on general principles but that isn't the same as understanding how it goes.
When someone proposes a perpetuum mobile it can instantly be dismissed by slapping a physics law on it, but that is a limited form of understanding. It's
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Read his paper and his rebuttal. He is basically saying that if the Lorentz law of force is replaced with a more elegant equation (Einstein-Laub), then you naturally obtain the "hidden momentum" terms that are inserted under a covariant transformation. Furthermore, there is another candidate equation, Helmholtz force, which is different but takes care of the "hidden momentum" in a similar way. Predictions in differences in experiments can be made and Mansuripur is attempting to realize these experiments.
What is it with physics? (Score:3, Insightful)
First of all, this post is aimed not at the engineer from the article, but at some of the posters to this story and others like it. What is it about physics in particular that attracts so many uneducated crackpots? It seems to be the sweet spot for cranks on the XKCD spectrum--they don't go all the way over to math, and try to promote their pet tensor analysis theory ("this is how we really should compute the induced map on the cotangent bundle!"), and even less often are we treated to their "revolutionary" theories of hydrocarbon structure or ribosomal protein synthesis.
Nope, they gravitate straight to physics. Is it that concepts are (relatively) familiar, like light, gravity, time, particles, etc? Is it Star Trek? Must drive physicists nuts.
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I suspect it's because classical physics is something we're all reasonably familiar with from our everyday experience but modern physics departs from our expectations in many ways. We know our intuition doesn't work very well with tensor analysis or hydrocarbon structure or protein synthesis, but we expect it to work well with bits of matter flying around. Cranks are just people who mistake their intuition, or deeply held beliefs, for "truth."
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I'd say it is the philosophical side of physics. Physics, sometimes more than the other sciences focuses on the big picture and hence, meaning of equations and less of plain facts, or at least that's what I gather from the pre-meds I tutor. It's not that meaning isn't important in biology or chemistry, it is just is that with so much information, going too deep into one topic can be a waste of time that misses the point. For physics, depending where you are on the experimental to theoretical spectrum, depth
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Any expert field suffer fools.
Take philosophy, which I study. People get frustrated just by my saying that I study philosophy. Why ?Because everyone's opinion is supposed to be equal. So I usually stick to empirical evidence and pick apart the arguments.
After a while they calm down. It is the "so you think you are smart" kind of prejudice. If not that, then it's the "you can't tell me what the meaning of my life is". Yes, I can, several meanings from several philosophers which can help us frame the question
Cognition (Score:2)
Executive Summary
If you have a paradox in a thought experiment, you can think your way out of it.
Re:Cognition (Score:5, Informative)
Not by any means. For probably the best example, look at the Einstein-Rosen-Podalsky paradox , a simple thought experiment used an attempt to disprove the so-called Copenhagen interpretation of quantum mechanics because it would require the instantaneous transmission of quantum states in such a way that would violate special relativity. People did try to think their way out of it, until Bell's theorem "thought" everyone back into the paradoxical corner - leading to the modern sciences of quantum entanglement.
In fact if you look back, many of the advances in modern physics have come about specifically because of paradoxes arising from thought experiments. See also the ultraviolet catastrophe, or even Schrodinger's cat for that matter.
Decision, by default, goes to ... (Score:2)
Mansuripur's papers are readable on Archive.org, while the replies of his critics are on paywalled journals. I do not have 30 or 40 dollars to observe their handwaving. Since he's out in the open, while their supposed 'replies' are hiding behind the bulwarks of protectionist convention, I'm awarding the decision to Mansuripur. All hail Swartz.
In Your Face (Score:2)
"In your face, engineers !"
-- Physicists
The Simple Version (Score:2)
For those not interested in the fine detail, there's a very simple explanation as to why there isn't any real paradox involved.
Let's start with a quote from the article (looks like the paper is a bit more subtle, but the upshot is the same): "Now imagine how things look from a "moving frame of reference" in which the charge and magnet both glide by at a steady speed. Thanks to the weird effects of relativity, the magnet appears to have more positive charge on one side and more negative charge on the other."
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RTFA. Unlike dark matter, hidden angular momentum isn't "invented", it follows from the assumptions of special relativity, which are dead simple and already proven beyond doubt.
Re:Dark matter (Score:5, Informative)
So, hidden momentum and dark matter... What other concept will we invent to explain we dont know anything?
Dark matter is not an invented concept, it is a name for something we observe. Galaxies just rotate faster than from what is there in normal matter. So something is going on, and this something is called "dark matter", just because it does not produce/interact with light but behaves like a mass.
Now in what way you explain this (new physical laws, new elementary particles) is still an open question. But it's there and needs to be addressed. Dark matter is just the name of the problem.
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Re:Dark matter (Score:4, Informative)
Observations of the gravitational lensing caused by far away galaxies in the process of merging have distinctly shown concentrations of something that's lensing the light that's not in either of the two galaxies. There are also other observations that kill any possible 'alternate law of gravity' explanations.
I thought these explanations were interesting myself and I've been paying attention to the topic. And there's been a lot of study of these ideas, because you're right, positing a brand new form of matter is a big step. And study leads to experiments. And the experiments have lead to the general consensus is that dark matter has to be something that has mass and doesn't otherwise interact with light (or normal matter) at all.
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As an interesting aside, I remember hearing that someone recently analyzed galactic rotation in terms of General Relativity rather than Newtonian gravity and found that the "anomalous" speed curve is actually predicted by the theory (the math is apparently *much* more complicated, which is why it hadn't been attempted before). It's true that there have been other observations of phenomena that also support the Dark Matter hypothesis, but the reality may well be considerably more subtle than the universe co
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Indeed - however in this case we're not applying exotic theories, we're simply applying our best accepted model of gravity (GR) instead of our known oversimplified model (Newtonian) and finding the problem disappears, at least mostly. Given that, the rotation curves can likely no longer be used as an argument for dark matter, and in fact may be an argument against it since the presence of such matter is probably inconsistent with the observed rotation curves under GR.
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It interacts gravitationally. What it apparently does not do is emit or absorb light.
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You're about 5 years behind the facts on dark matter. The cosmic microwave background radiation studies comfirmed the dark matter hypothesis for galaxy/cluster rotation rates several years ago now.
Dark matter was proposed in the 1930s. At the time it was one of several hypotheses for why rotation rates weren't as expected. But a few years ago the CMBR studies also "observed" dark matter, and the matter/dark matter ratio matched the predictions to a couple of significant digits (which for cosmology is ama
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Now in what way you explain this (new physical laws, new elementary particles) is still an open question. But it's there and needs to be addressed. Dark matter is just the name of the problem.
Hm. Doesn't calling it Dark Matter strongly imply that it is NOT a new physical law but rather some sort of... substance or particle? Surely you can see how the non-physicist who is curious could be mislead into a narrower interpretation?
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It's just called matter because it ACTS like matter, except for neither blocking or reflecting light, which is why it's called dark.
It's important to name something, even before you know what it is, because it's very difficult to discuss something that has no designation. They could call it "Effect 32" for all it really matters, it's just that "dark matter" gives the listener a little memory advantage over some arbetrary non-discriptive designation.
In reality dark matter could be nearly anything, and could
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Dark matter is not an invented concept, it is a name for something we observe.
It is as observed as Aether or the cosmological constant...
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Neither of those concepts are part of modern science.
You fuss because he was not specific enough. He meant that "Dark Matter is an effect we observe."
I will not engague you in a debate on whether or not an effect is a "thing" in that context, but I suspect you knew what he meant.
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Dark matter is not an invented concept, it is a name for something we observe.
Precisely the opposite - it's a name for something we haven't observed. And instead of appropriately referring to it as a paradox, inconsistency, etc. a concept of an entirely new "matter" was conjured up. I might agree with you that it's more likely that something is missing in the estimates of galaxy masses as opposed to physical laws breaking down, but gp is perfectly correct in saying that at this point it's a theoretical (i.
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but gp is perfectly correct in saying that at this point it's a theoretical (i.e. invented) concept.
So are quarks. They were invented to try to explain patterns seen in the formation of hadrons, and later used to explain some aspects nuclear structure. We don't observe the quarks directly, but only their interactions and decays. It is still possible we've missed another explanation that doesn't require inventing a whole family of particles.
The only thing that matters in the end is how well the theory agrees with observation. Dark matter is kicking butt here compared to all proposed alternatives. Al
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Sorry, you're just wrong on this one. In the 1930s, then the hypothesis was new, you would have been correct, but in the past decade measurements of the early universe (via the CMBR) have directly confirmed predictions made by the dark matter hypothesis.
Dark matter is as confirmed as anything else in science that there's not actual engineering built around. Everything in science is a theoretical concept: that's not a useful statement.
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Of course, the increase in speed from other galaxies is caused by aliens who are trying to fool us so that we don't develop superior knowledge.
In physics, if you have two explanations for a problem, choose the simplest one. If you have only one, well, that must be it.
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Aliens!?
No, no. It's Gnomes following their 3 step plan!
Step 1: Speed up the rotation of the galixies. .... umn.
Step 2:
Step 3: Profit!
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The thing is, there are many teams of physicists working on modified theories of gravities or trying to find new modifications of gravity. So far, none of them work as well as the dark matter theory, and they contradict observations in some way or at some place (or possibly require both dark matter and a modified just gravity). Some of them are even more contrived than creating a new particle, because they have arbitrary distances where things just suddenly change and they have to get that distance by jus
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what are you babbling about? of course a unformly accelerating (one case of which is going in a circle at constant angular velocity) electron radiates, turn on a motor or start a generator to prove.
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no, you only make the mistake of using a "simplified" version of Lorentz "contraction", actually there is a rotation in 3D toward the observer, no contraction as in the 1D-only consideration. problem solved, totally provable with either Maxwell's Equations or Special Relativity (the two are equivalent and one provable from the other)