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Einstein's Theory Improved?
skaet writes to tell us that A Chinese astronomer from the University of St Andrews claims to have fine-tuned Einstein's theory of gravity. Dr Hong Sheng Zhao has created a 'simple' theory which could "solve a dark mystery that has baffled astrophysicists for three-quarters of a century." This new law seeks to discover whether Einstein's theory was correct and if dark matter actually exists.
I'm sure that there are lots of people that are far more clued up on this than I am that can find holes in what I am about to say but I always felt like dark matter was a bit of a fudge because we don't understand what is happening.
My problem with dark matter is that it's almost as difficult to believe in as God. The only real proof we have is that the universe doesn't appear to move correctly without it. If that's as good as we can do then we might as well say God (or the FSM) is holding the universe together. To my mind it is a big leap from "the universe isn't moving as we expect" to "90% of the universe is made of something we can't see". Surely if the universe was full of this stuff we would be able to detect it because it would block radiation from distant galaxies - or is dark matter conveniently transparent?
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Won't it be ready until April? Stranger things have happened.
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What a clear and well-written article. And what a pleasant, unassuming statement from Dr Zhao:
"A non-Newtonian gravity theory is now fully specified on all scales by a smooth continuous function. It is ready for fellow scientists to falsify. It is time to keep an open mind for new fields predicted in our formula while we continue our search for Dark Matter particles."
Even if the theory turns out not to stand up, words like this take us back to what makes science interesting and important. That "falsify" is worlds away from the publicity hounds and egomaniacs who so often represent science to the lay reader.
Las qué passoun
tournoun pas maï
Although it is not the theory that has been improved, it is the model. It takes a simple function to interpolate between the dark matter area (which is non Newtonian - Modified Newtonian Dynamics or MOND) and the Newtonian area, where baryonic matter seems to reign. Despite a simple continuation function for the two areas, the authors find a nice agreement with rotation curves of galaxies including our own, and some external ones. The theory which has been used is the TeVeS (Tensor Vector Scalar) theory by Bekenstein. The scalar part of the theory could explain the dark matter behaviour.
It was Kepler who realised that ellipses could be the correct model for orbits, and even there, to try and keep the Church happy, he tried to fit the major and minor axes into the shapes of the "Platonic solids".
History suggests that the example you are quoting is the opposite of what you want to show. It is better to let scientists come up with initially ad hoc explanations because they lead to the truth. Making initial unscientific assumptions and treating them as dogma suppresses and delays progress. Scientists are ambitious and a good way to become important is to replace someone else's theory - so scientists can be relied on to do that. For every established Dark Matter theorist there are probably several PhD students who would love to annihilate Dark Matter.
The line of argument in the parent annoys me because it tries to suggest that scientists left to themselves will produce ridiculous non-explanatory theories and then cling to them forever. It's the anti-scientific agenda of the Creationists who want to discredit science. Creationists and their like want to confuse the public as to the explanatory status of different scientific theories so they can claim their snake oil is on an explanatory par with plate tectonics, quantum electrodynamics or evolutionary biology.
Pining for the fjords
The statement that "science is/isn't better than religion" is not scientific, it's rather religious.
Yesterday was the time to do it right. Are we having a REVOLUTION yet?
Although I share your skepticism about dark matter, I couldn't help thinking about the neutrino, a "hidden" particle that filled another gap in physics. It took 25 years for physicists to finally detect the neutrino.
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Simply??? What is simpler?
1) The laws of general relativity are valid universally, but we're having a hard time detecting part of the matter in the universe. What is it? Well, we have a dozen theories from supersymmetry to axions predicting particles that we might have trouble detecting. In fact, we only recently discovered large dark matter components of the universe such as the massive neutrinos and intergalactic neutral hydrogen streamers. This hypothesis matches impressively with a wide variety of measurements, such as galactic rotation curves, Big Bang nucleosynthesis, cluster formation and fluctuations of the cosmic microwave background.
2) Chuck out relativity and make up your own theory that is the same as GR everywhere (because GR is verified in all experiments to date) except in galactic rotation curves. This hypothesis matches impressively with... galactic rotation curves, because that's what you invented it to fit in the first place!
Having successfully improved on Einstein, I suggest we next work on improving the Mona Lisa. It's too painty.
Xerxes
No, that's not what happens. Laws say what happens, theories say why and/or how it happens. Laws don't try to explain behaviour, they just state it. Hence the laws of thermodynamics are laws, while the theory of relativity is a theory and always will be.
:-)
And the law of gravity? Observations say what happens. Theories say why and/or how it happense. Laws are what we call theories we think will never be falsified, and it's probably a word that should be dropped from any kind of scientific discussion, since we all should have learned by now that even the most basic assumptions and most obvious conclusions drawn from the most irrefutable of observations have a way of requiring revision from time to time, as better observations are made (Newton couldn't look at gravitational motion, and we cannot yet see into the higher folded dimensions of string theory, assuming such in fact exist).
The "laws" of thermodynamics are as theoretical as relativity. Both have been observed, both are mathematically modelled to great precision, both make useful predictions, both are falsifiable, and no one outside of a few religious wackos expects either to be falsified. That doesn't mean they won't be.
Someday we might find conditions in which entropy in a closed system decreases (candidates for something like this include the time leading up to the big bang--if such is found to have existed--and certain theories of the internal workings of black holes, etc.). Not that I or anyone else realistically expects this (but then, who expected the anomalies that would lead to the dark matter/energy vs. non-newtonian gravity debate, either), but the "laws" of thermodynamics are as falsifiable as the theory of relativity and, as it turns out, the "law" of gravity.
Theories do have a habit of becoming "laws" when they are basically considered irrefutable. They shouldn't--we should probably refer to gravity as the theory of gravity, and the laws of thermodynamics as the theories of thermodynamics. It might stop the "big bang theory" and "theory of evolution" rhetorical nonsense we've all been subjected to by communications majors coasting through college with a "C" average only to become network anchors...and help all of us to think clearer. That having been said, I imagine my calls to refer to the laws of thermodynamics as the "theories of thermodynamics" would fall on my old physics professor's deaf ears. Most of us like keeping our language the way it is, no matter how cumbersome or confusing it becomes--but that's a rant for another day.
The Future of Human Evolution: Autonomy
You yourself seem to think that killing an enemy soldier is murder, but also agree that murder is "The unlawful killing of one human by another, especially with premeditated malice". The whole idea of a soldier being an enemy soldier is that you are at war, and therefore are legally allowed to kill the enemy (unless they surrender)
Nonsense. Murder is wrong, unless we call it a "war", and makes it okay? No. It is *always* wrong to initiate the use of force against another person. The only time that the use of force is justified is to defend oneself or another against a person who has initiated the use of force.
Downmodding is the refuge of the weak. Don't downmod, make a better argument!
'Dark Matter' really describes the problem more than anything. I don't think that when the solution is found anyone will refer to it as 'Dark Matter' any more.
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This would be God's Law:
Thou shalt not kill...
That would be God's instruction to man as reported through the ages, by man, in the Bible and its ancestor documents.
It couldn't have been reported that way "through the ages", because before roughly 1000 years ago, the English language didn't exist, and nobody would have understood the words "Thou shalt not kill".
This is germane to the discussion, because it hinges on the exact meaning of the word that the KJV translated to English as "kill". The original text was in classical Hebrew, not English, and as with any translation, word meanings don't always line up exactly. This always leads to questions about the accuracy of a translation, since there are often alternate words possible that don't quite mean the same thing in the target language. And for a long-dead language, you really can't know all the possible meanings a word may have had to the original speakers.
There is consensus among biblical scholars that the passage was closer to "Don't murder". But that's also ambiguous in English, with many court cases depending on how the jury members interpret the word "murder" (and how they interpret the judge's instructions).
In any case, a claim that the English phrasing of a biblical passage was "as reported through the ages" is absurd. It can't even be close to true. Only a small minority of followers of the Jewish/Christian bible(s) have ever understood English.
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Most laws of physics start out as "curve fitting". After all, what is a physical theory other than a set of equations designed to describe some experimental data? The real test is when they predict phenomena other than the ones they were designed to fit, and those phenomena are observed. This theory has not yet reached that stage. Most new theories fail the second stage, but most of them start out with this first stage too, so you can't conclude that this isn't "physics".
I agree with the grandparent, and disagree with you.
There's no governing body of scientific terms, but I've seen many proposed laws with no prior history of being called a theory. In my physics experience, laws are almost always a mathematical model of observed behavior with no attempt to explain the underlying reasons or mechanics of said behavior.
Laws are theories as they fit all the definitions of a theory, but they don't become laws by extra proof, rather by their initial limited nature. For example, there is a law of gravity ( F = G Ma Mb / r^2 ) and there are separately various theories of gravity such as general relativity.
-Ryan C.
Dark Matter exists, and in my opinion it is here for good. The attempts to come up with alternative theories of gravity are quite noble, but they only work on certain scales, and the proponents of these theories sometimes neglect examples that invalidate their theory. It would be quite elegant to be able to account for dark matter via a modification of gravity alone, but I am afraid that it will not be possible.
One of the most compelling pieces of evidence for the existence of dark matter is the "bullet cluster of galaxies" discovered by Maxim Markevitch and collaborators. Their 2004 peer reviewed article shows a small cluster of galaxies passing through much more massive one. As the cluster passes through, its gas is stripped, but the dark matter stays behind, detected via weak gravitational lensing. This effect is impossible to reproduce using alternative theories of gravity, because there is a visible separation between the total mass peak and the observable mass peak.
There are dozens of other peer-reviewed articles that argue against these alternative theories of gravity. What about the cosmic microwave background? The CMB is one of the underpinnings of modern cosmology and basically made the big bang the widely accepted theory that it is today. This recent analysis of the CMB show that the kind of alternative gravity proposed here is strongly disfavored by the CMB spectrum, and that it would imply too high a neutrino mass.
I challenge you to look through the literature for yourself. Here is a list of papers discussing modified newtonian gravity and its derivatives... You will find that yes, these alternative theories do work quite well at describing the rotation curves of galaxies, as TFA suggest. But on larger scales, such as in cluster of galaxies and the cosmic microwave background, they seem to fail convincingly.
We may not have any reason to believe that the Universe is elegant, but we also have no reason to believe that it isn't. So when we find that two very simple and elegant theories (QM and GR) describe so many of our observations, who are we to say the Universe can't be simple and elegant?
Personally, I'm offended that so many lay people "don't believe" in dark matter. Just because we humans can only experience EM interactions (i.e. see, feel, smell, hear) why must everything in the Universe interact with photons?
Our current theory (QM+GR) has certain deficiencies in explaining our observations. Adding "dark matter" fixes many of them, no other theory (including modified exponents rather than good-ol' inverse-square for gravity) does as well. Therefore, until something better -- something that can do a better job of explaining so many things (galactic rotation, cosmic background radiation, galactic collisions) as well -- comes along, dark matter is it. Dark matter isn't around just because it would be kewl to have a closed Universe.
Ditto homogeneity and isotropism. If we don't assume the Universe is homogeneous and isotropic, there's not much we can say about cosmology. And if we do assume it, we can match so much of what we see. So why shouldn't we assume it? Until something better comes along....
Unlimited growth == Cancer.