Einstein's Theory Passes Strict New Test 243
FiReaNGeL writes with an excerpt from a story at e! Science News: "Taking advantage of a unique cosmic configuration, astronomers have measured an effect predicted by Albert Einstein's theory of General Relativity in the extremely strong gravity of a pair of superdense neutron stars. Essentially, the famed physicist's 93-year-old theory passed yet another test. Scientists at McGill University used the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) to do a four-year study of a double-star system unlike any other known in the Universe. The system is a pair of neutron stars, both of which are seen as pulsars that emit lighthouse-like beams of radio waves."
Re:For us plebs... (Score:5, Informative)
1. GE says two objects can cause a wobble in each other's axes due to gravity
2. Measurement of this wobble wasn't possible earlier
3. With this star system, since they are massive and pulsate, and that they are aligned in a manner that makes a measurement possible, astronomers took the plunge
4. Prof...proved.
Re:It's a shame really (Score:2, Informative)
That's exactly how "theory" is used in science. It doesn't carry that connotation of "this is just some stuff I'm guessing at" that it does in colloquial use. This is why creationists always talk about how "evolution is just a theory" when in fact, that indicates it's well-accepted among scientists.
Laws and Theories (Score:5, Informative)
Consider, as examples, Newton's laws of motion, or the laws of thermodynamics. Newton's theory of motion is deduced from his laws; the conventional theory of thermodynamics, likewise.
I say this because there are plenty of non-scientists who deliberately attempt to exploit confusion induced by popular use of the terms "law" and "theory" so as to imply that scientific theories, notably the theory of evolution, are held tentatively.
Re:For us plebs... (Score:1, Informative)
what is the mechanics that cause gravity to produce wobble?
its called Hyper Redundancy
Re:It's a shame really (Score:5, Informative)
Some time ago, I took a "History of Science" course. My memory is fuzzy around the dates, but originally, anything in science was granted the term "law". IIRC, "Caloric Theory" which was superseded by the theory of heat and thermodynamics was originally called a "law".
Around the 1700's, it was decided to call all new science a "Theory". In deference to previous conventions, the things still held over previously known as laws retained the name. Hence the apparent difference between the two terms.
Re:And that, boys and girls, (Score:5, Informative)
You do realize that is what they're doing, right? They're looking out into the Universe for ways to test the theory against real live data.
Re:It's a shame really (Score:3, Informative)
Makes things like this sit in the same bucket as one of my drunken musings. "I have a theory that.... in..... etc".
Not really the same. Theories have been tested and are supported by facts. A drunken musing, valid scientific starting point though that may be, is merely a hypothesis which then must be tested. If it survives the test, it then becomes a theory. And if it survives the test of time, it may become a "Law". There are very few scientific "laws", however. The gas laws are pretty much the only ones I can think of off the top of my head. Everything else is stuck at "theory".
Re:Can't be right (Score:1, Informative)
Yeah, I think you are correct. I thought I remembered hearing a Feynman lecture (perhaps the New Zealand lecture) we he was discussing which of the many formulations of QM was correct and where he described that nature acts as it wants to and that our physical theories only describe it to the best degree that we can reason and that they are all equivalent in the sense that they correctly describe how nature appears to act. But since I can't find a quote online, this argument probably came from another physicist.
Re:Einstein: Really Smart (Score:4, Informative)
Heres a couple of others:
Electrochemistry: http://alford.bios.uic.edu/teaching/Nernst.html [uic.edu]
Fluid Dynamics: http://mse-092697c.princeton.edu/lecture1001/page3.htm [princeton.edu]
hypothesis - 1 of 4 scientific terms (Score:5, Informative)
The word you are searching for is hypothesis.
There are 4 terms that need to be understood in the realm of science - hypothesis, theory, law & fact. They are all separate & distinct, except for the only progression that occurs - hypothesis => theory.
A fact is what has been carefully observed.
A law describes that observation.
A hypothesis is a proposal intended to explain that observation.
A theory seeks to explain that observation & has been confirmed by considerable evidence and has endured all attempts to disprove it.
example:
Fact
Objects fall at the same rate regardless of mass.
Law
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/circles/u6l3c1.gif [k12.il.us]
Hypothesis => Theory
Mass causes a curvature of spacetime which creates the effect of gravity.
Re:For us plebs... (Score:5, Informative)
Now THAT is a summary
Actually I recommend reading the article. It's short, understandable, and contains other cool facts about these neutron stars.
Also, as for that last "proved" bit, the article ends with:
"It's not quite right to say that we have now 'proven' General Relativity," Breton said. "However, so far, Einstein's theory has passed all the tests that have been conducted, including ours."
Re:hypothesis - 1 of 4 scientific terms (Score:5, Informative)
An observation is some type of measurement. We could call this a fact if we like, but observation is better because is acknowledges the role of the observer in a way that "fact" does not.
A law is some invariance across multiple observations. See, for instance, Kepler's laws. (They do not, as the parent says, "describe" observations, but rather they postulate invariant aspects of planetary motion)
A hypothesis is a testable prediction based on naturalistic explanation of lawful behavior, typically of smaller scope than a theory and untested or weakly tested. Theories can also lead to hypotheses, through logical implication (ie, "my theory predicts that X, therefore I hypothesize X will occur in this experiment")
A theory is a unified, parsimonious, testable, naturalistic explanation for entire sets of laws. For instance, Newton's theory of mechanics explained all of Kepler's laws of planetary motion, and lawful behavior on earth as well.
Observation: These objects that I have dropped all appear to fall at the same rate regardless of mass, within measurement error
Law: All objects fall at the same rate regardless of mass
Hypothesis and theory Newton's theory of mechanics, or Einstein's theory of relativity
Re:Can't be right (Score:4, Informative)
Re:Can't be right (Score:4, Informative)
Not sure if you're talking about superluminal travel or subluminal travel.
Theory already allows slower than light travel. You're spaceship would have to be big. VERY big. But if we really wanted to we could probably send mankind to the nearest stars with current technology.
But superluminal travel is a different kettle of fish. There are only two possible universes, one where there's an upper limit in the speed of information and another where there is no upper limit. The two universes have very different characteristics and our universe appears to be the smaller. It's hard to think of a way where you can transmit matter without also allowing information transfer.
Of course, even today faster than light travel is possible by current theory - but only by points A and B separating faster than light, not by allowing points A and B to communicate faster than light. Effectively this means that the speed of light is only constant locally. Maybe it would be possible to reverse the expansion and shrink the universe so that although the speed of light would still be an upper limit, communication between A and B could occur in less time than light could make the journey in a flat universe.
But I'd wager that faster than light travel in the special relativity sense is, and always will be, impossible.
Tim.
Re:Can't be right (Score:4, Informative)
Ok, but to clarify for some readers, "particle" does not mean corpuscular like a tennis ball, which is why the term "particle" tends to be a little misleading. In fact, it is why any "it's like a " phrase tends to fail, and why it was such a shock to discover indeterminable states to begin with. Quantum theory rests on the (unsurprising) revelation that at small scales, things are not as we have always visualized in the large, solid man-world. I don't think anyone other than Bohr was comfortable at the time with *any* explanation of some of these phenomena, even with models that were so fucking accurate.
And light does travel in wave form. Pics from a slashdot story very short while ago:
http://technology.newscientist.com/article/dn14172-fastestever-flashgun-captures-image-of-light-wave.html?DCMP=ILC-hmts&nsref=news1_head_dn14172 [newscientist.com]
But it is easier to think of the quantized light in terms of... quanta! New particles, now with many new features and a money back guarantee!
Happy Independence Day!
Re:Relativity vs. Quantum (Score:3, Informative)
This has always bugged me; how in the heck do you quantize geometry like |x>?
|x> isn't geometry, it's a position variable. Geometry is described by a metric (or a connection), i.e., a tensor field. Simple perturbative quantization of a rank-2 tensor (the graviton field) doesn't work, but one can hope to try more subtle approaches. In the quantum geometry of loop quantum gravity, for instance, you represent a spatial eigenstate as a spin network, whose edges carry quanta of area and whose vertices carry quanta of volume.
I was under the impression there wasn't a good way to do that without losing isotropy.
That's the problem that many straightforward discrete approaches run into (e.g., lattice quantum gravity). If you break up space into a regular grid, then doesn't it have preferred directions? That's one reason why people look at things like random triangulations, random networks, etc.; you can hope that their small-scale structure is smeared out isotropically in the classical limit.
Moreover, wouldn't that screw up the coordinate transforms that we use to talk about some of the only analytically solvable systems in quantum, like the two-body central force problem?
Why?
Moreover, given that momentum and position are Fourier conjugates, does that quantize momentum as well?
Momentum is already quantized in ordinary quantum mechanics, at least for bound systems.
I guess if I can accept a continuous basis for position states I should have no problem with a countably infinite one, but it still confuses me. :-)
Quantum gravity is more subtle than merely making space into a countable lattice. And note that even in that case, if geometry really is quantum mechanical, a classical spatial state would probably look like an infinite superposition of different discrete lattices, not any single one.
Finally, (and this shows I haven't gotten very far in quantum), I'm troubled by the asymmetry between position and time in the formalism I learned, that is, position is a state, but time is merely a parameter. To be consistent with relativity, do you need to make time a state as well? How does that change \hat{U}(t)?
There isn't a "time operator" in string theory or loop quantum gravity, either. Even in quantum field theory (quantum mechanics coupled to special relativity), you don't have one. The theory still works.
Re:And that, boys and girls, (Score:3, Informative)
Having studied all of these fields, I can safely say that the average undergraduate curriculum or textbox in any of these areas contains only the barest minimum of geometry, despite the vast amount of geometry inherant in these subjects. This is down to two reasons.
First and foremost, is laziness. It is easier to thrown down a rote definition by dictate than it is to motivate, explain and build a framework in which those definitions make sense. The former is the preferred method, and essentially leads to mathematics by rote learning, which is not really mathematics at all. The latter is the correct method, and leads to real understanding. Geometry is a key part of this method of explaination, which is why you see so little of it around.
The second method is related to the first. It has to do with the fact that after so many decades of poor textbooks devoid of geometrical meaning, very few people are actually aware of the geometry aspect of their fields, and write their textbooks accordingly. I'm sure not a few slashdotters went through a linear algebra course in which the only picture, if any, was to do with the solution of two, two variable simultaneous equations somewhere in the first lecture. In reality, linear algebra was developed from its outset, by this man [wikipedia.org], to be a method for solving problems in geometry via algebraic techniques. Most if not all standard techniques in linear algebra can not only be interpreted as a geometric method, but are essentially incomprehensible otherwise.
Classic example of the dearth of geometry in mathematics textbooks, and something relevant to this discussion, is the almost universal definition of "contravariant" and "covariant" tensors in general relativity/differential geometry textbooks. The usual "....whose coordinates transform according to the rule...." definition is essentially useless and betrays the authors incompetence and robs the reader of any real understanding of the topic. Contravariance and Covariance in fact have nothing to do with coordinate transformations of any kind and have far more fundamental origins, best revealed through basic geometric pictures. Try this book [amazon.com] for an example of how things should be done.