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Arthur T Knackerbracket has found the following story:
Testing general relativity is a fraught business. The theory has proven to be so robust that anyone who thinks it's wrong gets slapped around by reality in a pretty serious way. The tests that we apply are also limited by our environment, in that we can only look at gravity with precision where it's rather weak: in the lab, or by tracking the motion of planets. That's a whole range of scales and forces, but it doesn't cover where it might truly matter, which is right next to a black hole.
Observing orbits around a black hole would take a career's worth of measurements and, frankly, who has the time? It is also a rare benefactor who will fund a couple of decades worth of telescope time. Luckily, telescopes have been collecting data for a while, and some of that happens to include the vicinity of some black holes. Recently, some scientists decided to dig up the data and test general relativity in the vicinity of a supermassive black hole.
At the center of our galaxy, there lies a black hole, which like the Rabbit of Caerbannog, fiercely devours unwary wanderers. Nevertheless, there are a few foolhardy stars that orbit close to the rabbit black hole. These stars have orbits of just a couple of decades, and they experience rather large gravitational forces. So, astronomers expect that accurate observations of these stars might pick out deviations from general relativity.
Luckily, the Keck telescopes have been gathering data from the heavens for about 25 years, and over that time, they have turned their unblinking eyes towards the galactic center on numerous occasions. Each time, the observations were performed a bit differently. For instance, the telescopes were upgraded with adaptive optics in 2005, and some of the observations focused on obtaining spectral data rather than imaging. These latter data contain orbital velocity data, because the motion of the star causes a doppler shift in the observed colors of light.
All of this data was combined in a consistent way to map out the orbital positions and velocities of two stars. This is quite an achievement, because for each observation, the telescope is pointing in a slightly different direction, using different exposure times, and accounting for other slight differences. Although other telescopes also have data available, the public records were not detailed enough to allow the scientists to process the data in a consistent way. This is a pity, because, the data set consists of about 100 observations from just these two telescopes. Imagine what might have been obtained if more telescopes had accessible data?
After all of this, what have we learned? General relativity is still right, and it predicted the stellar motion accurately. These measurements tested general relativity in a way that was distinct from all previous ones—in high gravitational fields over long periods of time. In particular, the new measurements helped to put boundaries on extensions to general relativity that follow a kind of modified Newtonian dynamics model. In these models, there is a distance at which a new force becomes apparent, and that force has some unknown characteristic strength. So, astronomers are looking for a consistent distance at which there is a noticeable deviation from predictions. However, the measurements tell us that for any distance that is relevant to the orbit of these stars, a new force would have zero strength.
Or, more precisely, a new force would have a strength that is so small that we cannot yet measure it. Conclusion: general relativity wins again.
-- submitted from IRC
(Score: 2) by richtopia on Monday June 05 2017, @07:49PM (1 child)
I am not an astronomer but I thought that black holes were named. What black hole is being referred to in the article?
(Score: 3, Informative) by wonkey_monkey on Monday June 05 2017, @10:04PM
It's the one at the centre of the galaxy, so Sagittarius A*. They don't tend to get named with anything other than a designation, or sometimes after their host galaxy.
systemd is Roko's Basilisk
(Score: 2, Informative) by Anonymous Coward on Monday June 05 2017, @07:50PM (8 children)
The media and science-popularizers treat Einstein like he popped into existence from some other dimension, delivering unto us The Word. The truth of the matter is that the man was a product of exactly his times, and his work would not have been perfected—let alone even made possible—without the direct and indirect contributions of a huge number of people.
For instance, there's a reason that an Einstein could come to be only after a Riemann, or a Michelson or a Morley, etc.
(Score: 3, Insightful) by pvanhoof on Monday June 05 2017, @08:00PM (2 children)
I believe at the time of writing his most important papers, he was together with Mileva Marić. As I understood history, she often double checked his work.
(Score: 0) by Anonymous Coward on Tuesday June 06 2017, @04:46AM (1 child)
There is literally 0 evidence of this. Arguably there is less than 0 since there is substantial evidence to the contrary. In particular Maric failed out of university after being unable to achieve the necessary 4/6 on her final examinations - scoring a 2.5 in, you guessed it, mathematics. She then took it again and failed again without improving. She then gave up. And now she's supposed to be double checking Einstein's work which were, almost entirely, based around advanced theoretic applications in the field Maric failed out of? This is called revisionist history to try to support a political agenda.
(Score: 0) by Anonymous Coward on Tuesday June 06 2017, @12:50PM
Depends on which paper you are talking about. General Relativity, yes, that's very heavy mathematics. Special Relativity, there's mathematically nothing more advanced that basic vector algebra (there exist more advanced formulations, but those came later). The breakthrough in Special Relativity was in the concepts, not in the mathematics (indeed, most of the formulas themselves were already known from Lorentz aether theory; there's a reason the transformations are known as "Lorentz transformations", not "Einstein transformations"). If she knew enough mathematics to be admitted to university, I guess it should have been sufficient for cross-checking that paper.
And of course, Maric (or anyone else) having cross-checked Einstein's work would in no way devalue Einstein's contribution. Just because you can comprehend something doesn't mean you could have come up with it to begin with. And yes, I'm a physicist, I know what I talk about.
Note that I have no idea whether or not she did cross-check Einstein's work. All I say is that if she did, that doesn't detract the slightest bit from Einstein's achievements.
(Score: 0) by Anonymous Coward on Monday June 05 2017, @08:04PM (1 child)
I am sure without Einstein, another would have stepped up.
(Score: 2) by Arik on Monday June 05 2017, @08:16PM
Well, turned up at least. Steins do not, in my experience, step.
If laughter is the best medicine, who are the best doctors?
(Score: 2, Interesting) by Anonymous Coward on Tuesday June 06 2017, @04:56AM (1 child)
Nobody is saying he didn't build off the shoulders of giants. Relativity is, in effect, a direct result of the Michelson-Morley experiment. [wikipedia.org]
However, at the same time - he was not just a product of his times. Michelson-Morley was 1887 when Einstein was 8 years old. Einstein's first paper on relativity would not be published for about 2 decades. His 'big picture' paper coming 3 decades after Michelson-Morley. There was an entire generation of scientists that had the opportunity to discover relativity. They failed. Though the math is complex, it's workable for more or less any mathematician. In my opinion what really made Einstein unique was his creativity. The whole concept of relativity is absurd, and I think it's this absurdity that kept it from being considered for so long. There's a physics joke that all the scientists of the time were trying to explain why light could be seen as moving at identical rates from differing perspectives - and Einstein simply assumed it! For an educated and intelligent man to even imagine that the universe twists itself around into multiple asynchronous 'perspectives' with time as just yet another dimension of movement is phenomenal and something that requires the mind of a mathematician and the creativity of a child - a rare mix indeed!
(Score: 2) by aristarchus on Tuesday June 06 2017, @08:39PM
Nice trick, if you can pull it off. Is the even more specialler Relativity? In my own experience, being 1887 is no piece of cake. Of course, it gets better after that.
(Score: 2) by FatPhil on Tuesday June 06 2017, @07:54AM
However, it's a tightly interwoven nest of mathematical and scientific progress, noone succeeds alone.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2, Insightful) by Anonymous Coward on Monday June 05 2017, @08:06PM (6 children)
This is such a stupid thing to say when the current GR-based models require 95% invisible stuff that has only been detected as deviations from GR predictions. I mean it really makes me doubt the whole cosmology effort is an honest one.
(Score: 3, Interesting) by bob_super on Monday June 05 2017, @08:58PM (5 children)
The fact that it doesn't explain everything is a known limitation (like most of science).
But everyone who's tried to prove it wrong has hit a wall...
(Score: 1, Interesting) by Anonymous Coward on Monday June 05 2017, @09:03PM (4 children)
Thank you for your inbox but it predicted a very specific thing about rotation curves, and this was false.
Then a new model GR + DM was created. So far after much time and energy spent there is no evidence for DM except that GR predicts the wrong thing. Further, if anyone actually relied on the rotation curve estimates for anything they would use other models like MOND since GR + DM predicts nothing while MOND is perfect at predicting this (since the amount of "DM" can be 100% predicted from the amount of visible matter).
(Score: 2) by stormwyrm on Tuesday June 06 2017, @01:10AM (3 children)
Yeah, MOND fits galaxy rotation curves. It was designed to do so. But what happens when you try to apply it to stuff bigger than a single galaxy? Galaxy clusters, large scale structure formation, CMB anisotropies, for all of these, MOND theorists have been forced to resort to some fudge factors that essentially amount to the postulation of some form of dark matter! Galactic cluster collisions show gravitational lensing where there is no visible matter [wikipedia.org]. Large scale structure formation theory informed by dark matter also predicted that galaxy clusters ought to start appearing at redshifts z=2.5, about 11 billion light years away, and that has been borne out by observations [forbes.com]. Dark matter also fits the peaks in the CMB power spectrum [discovermagazine.com]. There is plenty of indirect evidence for dark matter, and with so many mutually supporting lines of evidence pointing to its reality and the continuing failure of any alternative theories to explain all the available data we have today any better or even equally well is why Lambda-Cold Dark Matter is at present considered the standard cosmological model.
Numquam ponenda est pluralitas sine necessitate.
(Score: 2, Interesting) by FatPhil on Tuesday June 06 2017, @01:27PM (2 children)
DM makes the model fit measured rotation curves by letting you chose where you drop dollops of invisible stuff in order to make the curves seem to fit the model. That's an infinitude of fudge-factors.
Dark Matter is at present considered the standard cosmological model because there is a scientific cartel which is rejecting (quite literally) studies into alternative theories. How many quantised inertia papers have you encountered in the last year, for example? How many DM proponents could even finish this sentence: "DM can be disproved by ______"? How many of them who can finish that sentence are actually attempting to disprove their theory, and how many are simply riding the confirmation-bias train? The parameter space for what DM can be is ever-shrinking, rejecting possible candidates with every new result. And Nima Arkani-Hamed still hasn't eaten his hat, like he promised, when the experiment which he was sure would confirm his N-th model of Dark Matter (which had to be right, as it was so beautiful), actually refuted it - instead, he came up with model N+1. For "science"!
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 2) by stormwyrm on Wednesday June 07 2017, @02:03AM (1 child)
DM can be disproved in any number of ways. There was a chance with Lambda-CDM structure formation theory, which predicted the formation of galaxy clusters at around z=2.5. If someone found galaxy clusters coming together at a much greater or smaller distance, that would have been a big blow to dark matter theory. But they saw [soylentnews.org] exactly what the theory predicted. Stacy McGaugh had a chance when he discovered the SPARC acceleration law [soylentnews.org], but then it was seen [soylentnews.org] that simulated galaxies assuming Lambda-CDM cosmology were already exhibiting the same acceleration law too. There was also a big prediction from dark matter theory that McGaugh’s SPARC acceleration law would fail to hold at great distances. If someone managed to measure the rotation curves for very distant galaxies and showed that they still obeyed the acceleration law, that would have gone a very long way towards falsifying dark matter and making MOND look a lot more plausible. However, when someone managed to do that, they found that yes, indeed, these young, distant galaxies do not seem to fit the acceleration law. [soylentnews.org] It’s only a three-sigma effect so far so the jury’s still out and we’ll probably need better telescopes like the JWST or Magellan to get really robust results to settle this one way or the other.
If someone does manage to make an observation or experiment that contradicts current theory, they’ll try to revise the old theory, but it may get to the point that a better explanation can be made, and a new and better theory comes forward and becomes dominant. That’s generally how science progresses. That’s how we got from Ptolemaic astronomy to modern celestial mechanics. That doesn’t yet seem to be what is happening with dark matter and current theories of modified gravity though.
But I suppose there’s no convincing you if you actually believe that there’s a huge conspiracy of scientists out to suppress these alternative theories. The only thing that’s suppressing these alternative theories is their lack of agreement with observation and experiment. I don’t think Stacy McGaugh, Mordehai Milgrom, or Erik Verlinde have had any problems getting their papers on alternatives to dark matter published. I think it’s a good thing that people are looking at alternatives, and just maybe they might be able to explain things better than the current theory, and then they’ll become the dominant theory. But that day hasn’t come, and so for now dark matter remains part of the standard cosmological model.
Numquam ponenda est pluralitas sine necessitate.
(Score: 2) by FatPhil on Wednesday June 07 2017, @08:13AM
http://physicsfromtheedge.blogspot.com.ee/2017/01/a-taste-of-kafka.html
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 3, Insightful) by GreatAuntAnesthesia on Monday June 05 2017, @09:43PM (1 child)
+1 gratuitous and unnecessary mythical bunny reference.
(Score: 2) by nethead on Tuesday June 06 2017, @12:57AM
And I'll match you with a Great A'Tuin.
How did my SN UID end up over 3 times my /. UID?