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Einstein's Theory Improved?
Posted by
ScuttleMonkey
on Tue Feb 14, 2006 06:34 AM
from the lots-of-rumblings-in-the-physics-world-lately dept.
from the lots-of-rumblings-in-the-physics-world-lately dept.
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.
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Scientists Expand Knowledge of Dark Matter 211 comments
nife00 writes "BBC News is reporting that British scientists at Cambridge have expanded the current understanding of the mysterious particles known as dark matter." According to the article: "[The Cambridge Team] has at last been able to place limits on how it is packed in space and measure its "temperature". "It's the first clue of what this stuff might be," said Professor Gerry Gilmore. "For the first time ever, we're actually dealing with its physics," he told the BBC News website."
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Physicist Claims Time Has a Geometry 447 comments
sciencenews writes to tell us that a physicist at Stanford has just recently published a peer review website for several physics lectures focusing on a single underlying idea that "time is not a single dimension of spacetime but rather a local geometric distinction in spacetime." The science is presented quite clearly and originally uses GPS systems as a point of focus. From the article: "Not too long ago, people thought the Earth was flat, which meant they thought that gravity pointed in the same direction everywhere. Today, we think of that as a silly idea, but at the same time, most people today (including most scientists) still think of spacetime as if it were a big box with 3 space dimensions and 1 time dimension. So, like gravity for a flat Earth, the single time dimension for the 'big box universe' points in one direction, from the Big-Bang into the future. A lot of lip service is given to the idea of "curved spacetime", but the simplistic 3+1 'box' remains the dominant concept of what cosmic spacetime is like."
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New Gravity Theory Dispenses with Dark Matter 442 comments
Darkness Matters writes "According to New Scientist, a theory of modified gravity, which has no need of dark matter, has just explained why the Pioneer 10 probe is 400,000 miles off its expected course as it leaves the solar system. It sounds pretty convincing, although in dispensing with dark matter, they've had to utilize the theoretical particle, called a graviton, which appears from the vacuum of space wherever stars are densely packed, making gravity stronger."
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Very interesting... (Score:5, Funny)
Law is for lawyers, not scientists (Score:4, Funny)
Re:Law is for lawyers, not scientists (Score:5, Funny)
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Re:Law is for lawyers, not scientists (Score:5, Funny)
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Murder vs. kill (Score:4, Interesting)
I've heared once that the original hebrew text reads "Thou shalt not murder." If that's true, the contradiction is easy to resolve: Just define that killing ordered by god is no murder.
My understanding was similar but different. I had heard that the original ancient language of the bible did not have a rich engouh vocabulary to distingiuish between kill (e.g. an enemy) and murder (e.g. one in your own society), but the next most recent translation of the bible used the word "murder", not "kill".
The point is, when Moses was taking his tribe around the desert with their new commandments, they were to preserve their own society (which is what the 10 commandments promote), but if they had to kill competing tribes to survive, they could do so because it would be *killing*, not *murder*. Any society that condones unbridled murder within itself will quickly commit suicide.
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Re:Murder vs. kill (Score:5, Informative)
As a side note, the "ancient language" remained very consistant for a very long time. There is very little difference between the hebrew spoken then versus now. Only when you get far enough in the past to aramaic (spelling??), you get an actual different language.
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Re:Murder vs. kill (Score:5, Interesting)
Indeed, most verbs in Hebrew have a three consonant "root" (some have two). Depending on the tense, person, number, and gender of a verb (Hebrew verbs, unlike say, French verbs, agree with the subject's gender as well as number), the vowels in a Hebrew verb will change (and a prefix or suffix may be added as well).
All of this is just a roundabout way of saying that any word with say, a k-t-v root will have to do with, in this case, writing, whether it's katav or kotev or what have you.
This is why all semetic languages evolved writing systems where the vowels are generally not written: vowels simply don't have much semantic value in semetic languages. It may seem weird at first, but it's actually rather logical if you're exposed to it for a while.
Now, I'm not Jewish, so I don't know exactly, but I remember reading that the religious texts in fact were marked with the vowel diacritics -- that in fact, the vowel diacritics were invented for the sole purpose of reminding Rabbis how the texts should be read, as Hebrew was a dead language for a millenium or more.
Native speakers have little need for them, as it is clear from context what the vowels should be. Thnk abt t, vn n nglsh y cn ndrstnd lrght, and in English the presence or absence of vowels can actually change the root meaning of a word!
Anyone who is actually Hebrew-speaking and/or Jewish feel free to correct me. My Hebrew is very bad.
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Re:Confusing creationists (Score:4, Funny)
Not necessarily, but God's orders to the Israelites when they invaded the Promised Land went far, far beyond the killing of enemy soldiers. God wanted everyone killed - although ISTR that on one occasion he relented a little and allowed the Israeli troops to take some of the young women of the cities they were destroying for themselves. For the Lord is a merciful god.
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and the "law" of gravity? (Score:5, Insightful)
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.
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Dark matter eh. (Score:5, Insightful)
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?
Is dark matter conveniently transparent? (Score:5, Funny)
I have to disagree with that, I have no problem believing in the existance of dark matter. In fact I don't have to 'believe' in the existence of dark matter at all, I found some between my toes this morning and it was most certainly not transparent.
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Re:Dark matter eh. (Score:5, Informative)
For the reasons why dark matter must exist; some reasons are straight forward, some are more round-about-observations. The easiest one is from galaxies rotating too fast. The fact that they stay together means something is holding them together. Since we don't observe anything like a giant rope or hand of God holding our sun in place, the only logical explanation is gravity. Since we can't see enough matter to make this much gravity, it must be dark.
The dark matter that's hypothesized because of the large scale curvature of the universe is not as straight forward, especially since it was recently found that the universe seems to be accelerating in it's expansion.
I'd also like to point out that gravity, electrons and other particles or forces are no less valid than photons as observational tools. We really don't have to 'see' something to know it's there.
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Re:Dark matter eh. (Score:4, Insightful)
I certainly don't have a problem with the idea that we don't know everything. Perhaps my problem with dark matter is that it is reported in the press almost as if it is almost fact and yet in reality we haven't got any direct evidence. All we really have to go on is the fact that if dark matter didn't exist things, such as galaxies, wouldn't look like they do. If I had gone to my supervisor with an argument like that when I was doing chemistry he would probably have laughed himself stupid right before he sacked me. As for it not interacting with radiation thinking about it even if it did it could still be very hard to see. After all the universe is very big - you could easily hide something in it.
In the spirit of good science hence forth I am going believe that the FSM holds galaxies together with his noodly appendages. The reason the speed with which the universe is expanding is increasing is easly solved by saving that the universe is created by the FSM using lazy initialization. We gain the ability to see further faster so the FSM has to push on the edge of the universe harder hence making the universe expand faster. Simple really.
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Re:Dark matter eh. (Score:4)
We must keep in mind that all the mathematical constructs we have at the moment are approximations. Newton's and Einstein's Laws are approximations that function well locally (in astronomical terms).
It pays to keep an open mind on this subject (and all others) until it can be proved conclusively either way. Otherwise one is as bad as the church when it tried to suppress Galileo.
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Restorative (Score:5, Insightful)
"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.
Re:Restorative (Score:4, Interesting)
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Completely irrelevant - St Andrews (Score:5, Informative)
Unfortunately, like Cambridge, St. Andrews has suffered from negative publicity as a result of its taking occasional pupils from failing schools and admitting them with A level scores which would not normally allow a student to be admitted. But at least it meant that some of the Windsors got access to higher education, so perhaps the policy is defensible.
Anyway, I'm very pleased that the astrophysics tradition is continuing. But I'm still left with a question: Why are the nicest British Universities (Cambridge, Durham, St Andrews) in such bloody cold places?
Re:Completely irrelevant - St Andrews (Score:5, Interesting)
I did go there --- it's a great place (and the bright red gowns are no longer compulsory, although you get free entry to the castle if you wear your gown). I did first year astronomy before realising that my maths weren't up to it and switching to comp sci; St. Andrews has some genuinely decent telescopes [st-and.ac.uk] despite being at sea-level in a built up area. The Greg is deeply impressive to go and see. It's amazing just how big it is.
For those who don't know, St.Andrews is the third oldest university in the UK, after Oxford and Cambridge; it was founded in 1413, and totally dominates the town. (The university owns most of the town centre.) Going there is an experience totally unlike any other university in Britain... I had a room in a hall of residence five minutes walk from the town centre, perched high on a cliff top overlooking the North Sea. Great view.
Unfortunately, like Cambridge, St. Andrews has suffered from negative publicity as a result of its taking occasional pupils from failing schools and admitting them with A level scores which would not normally allow a student to be admitted. But at least it meant that some of the Windsors got access to higher education, so perhaps the policy is defensible.
Actually, things have changed. Until very recently, British students got their tuition fees paid by the state. Not long ago, however, the British parliament voted to make them pay a proportion --- but the Scottish parliament didn't. So students who go to a Scottish university get their tuition fees paid for them. As a result, all the Scottish universities have been inundated with students, and as the highest-prestige university in the country, St.Andrews can now basically name their price.
That doesn't explain Prince William, however, who is by all accounts not very bright.
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I want his job! (Score:4, Funny)
(1) Jobs where if you goof up, some money goes down the drain, or you're embarrassed or, somebody gets hurt or dies. You know, like being a doctor or lawyer or engineer.
(2) Jobs where it doesnt matter one whit if you're wrong. Jobs like theoretical physicist in a field where there isnt the slightest possibility of carrying out an experiment. Such as dabbling in the theory of gravity.
Like an idiot, I'm in category #1. What a dope.
Here is the arxiv preprint (Score:4, Informative)
My opinion as a physicist (Score:5, Informative)
As it stands, dark matter models can pass many experimental tests, and they're still the way to bet. That being said, MOND is not a bad idea either. It's not as well supported by dark matter, and it has serious problems with galaxy clusters, but it can still account for a surprising amount of data [uchicago.edu] (for a nonrelativistic theory!). The flaw of non-relativistic has been "corrected" by Bekenstein's TeVeS theory [arxiv.org] (the one that Zhao and Famaey's work [arxiv.org] is based on).
Unfortunately, TeVeS appears to be rather ad hoc [google.com] (even compared to dark matter). Z&F's work does not appear to be much better in this regard. In addition, solar system observations appear to place serious constraints [arxiv.org] on such MOND-like theories, leading to anomalous non-inverse square forces in the outer solar system (and no, it doesn't seem to be of a form that can be attributed to the Pioneer anomaly [arxiv.org], though the jury is still out).
The TeVeS/dark matter debate should be definitively resolved by the Planck mission [esa.int], which will be capable of resolving the third acoustic peak in the the cosmic microwave background radiation power spectrum. TeVeS and dark matter make very different predictions [uchicago.edu] for the structure of this peak. Of course, if TeVeS fails this test, maybe some other MOND-like theory could be put forward (if the entire class of theories hasn't already been ruled out by other means, such as solar system dynamics, by then).
Seductive elegance (Score:5, Interesting)
The problem is that as a result physicists really, really like very elegant theories when there's no particular reason to believe that the Universe itself has the same bias. Similarly, we like to take theories that work on scales and locations that we know and can easily interact with, and assume that they smoothly apply in the places that we can't get to know quite so easily. It's reasonable even if it isn't logical - we have to go with what we already have. It's a decision born of practicality.
In Cosmology, there's even a phrase for this: we assume homogeneity and isotropy. That is, that there's nothing special about where and when we are, and that the universe is pretty much the same (in physical laws) everywhere. The first time I heard about "dark matter," it was in the context of closure of the Universe. Physicsts really really wanted the universe to have enough mass/energy in order to be "closed," but we simply weren't finding enough matter. There was no reason to believe that the universe is closed (curvature 1.0), but it just seemed more elegant. So, they started to look for the "missing mass."
These are not logical assumptions, they're just assumptions that we have to make in order to get anywhere. Again, there's no reason that the universe will cooperate on this matter.
My own bias is to reject dark matter in favor of a revised theory of gravity, but that's just my own love of elegance - a different gravity feels more elegant than dark matter and dark energy, and in fact would hint at much more interesting cosmologies. But that's just how I am seduced by elegance...
Re:It's Light (Score:5, Informative)
Where on Earth you found that light has so much gravitational field? And why would be constant: shouldn't it vary with the luminosity of the star (which goes like mass^4, so it's highly nonlinear)??
Galaxy spanning in fact.
Ah, I see. You are off by four orders of magnitude. Come back when your astronomy is a little better.
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Your history isn't quite right (Score:4, Insightful)
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.
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Neutrinos (Score:4, Insightful)
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