Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Geezer on 27/01/2010 00:53:40
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Is it acceptable to sweep aside experimental evidence that is described in terms of Classical Mechanics with statements like "According to General Relativity, that's clearly wrong!" without providing sufficient explanation (or any explanation) for the observation in terms of General Relativity?
Would it be reasonable for Old Newtonians to conclude that New Relativists who are unable, or unwilling, to explain the observed phenomena, either in terms of Classical Mechanics, or General Relativity, are simply talking through their hats?
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What phenomena have been observed experimentally that can't be explained by GR? The math involved in GR can be incredibly messy, and so using it to solve for plain old Newtonian mechanics is kind of silly, but it could be done. Also, GR closely agrees with Newtonian mechanics in the Newtonian limit, which is for relatively weak gravitational fields with objects that are moving slowly compared to the speed of light, so in those regions, any experiment that gives a Newtonian result is also in agreement with GR.
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I don't believe any phenomena can't be explained by GR. There is nothing wrong with GR, but GR is complex, and if it is misapplied, it can lead to conclusions that might appear to totally contradict CM.
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Some things in the world don't act like they should in classical mechanics. In general, evidence for GR proceeds by showing the relativistic effects that go beyond what one expects in Newtonian mechanics. According to GR, Newtonian mechanics is mostly right.
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Some things in the world don't act like they should in classical mechanics. In general, evidence for GR proceeds by showing the relativistic effects that go beyond what one expects in Newtonian mechanics. According to GR, Newtonian mechanics is mostly right.
I agree with you Physbang. There are situations that have to be explained by GR, but there are also a many situations that can be described, either in terms of GR, or CM, and the results will be very similar if not identical.
My only point is that, while there may be some arguments against some of the underlying assumptions in CM, it can still be a useful method, and, if we are going to discount the results that CM produces, we ought to be able to fully describe the situation in terms of GR.
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It's not a matter of discounting classical mechanics, Geezer. It's more like seeing the subtle differences. Classical mechanics works, that's what people tend to use very successfully in normal operations. The grey area comes in when people talk about why it works, and what's really going on with say gravity. Then you get into general relativity and then move from equations to interpretations, and then people sometimes start arguing because things aren't black and white any more. In answer to your OP questions:
Is it acceptable to sweep aside experimental evidence that is described in terms of Classical Mechanics with statements like "According to General Relativity, that's clearly wrong!" without providing sufficient explanation (or any explanation) for the observation in terms of General Relativity?
No, it's not acceptable. This is a discussion forum, if there's no explanation you should ask for some and expect to get it. Whether the explanation is insufficient can be a grey area again, but this is why we discuss things, hopefully to everybody's satisfaction.
Would it be reasonable for Old Newtonians to conclude that New Relativists who are unable, or unwilling, to explain the observed phenomena, either in terms of Classical Mechanics, or General Relativity, are simply talking through their hats?
No, that's going too far. The differences aren't huge, and there's material out there you can look at that supports relativity. See for example The Confrontation between General Relativity and Experiment by Clifford M. Will at http://relativity.livingreviews.org/Articles/lrr-2006-3/.
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No.
It doesn't. Science is about the experimental evidence.
On the other hand, I'd want to know the details of how the experiment was carried out*, whether it's reproducible, and whether the results actually show what's being claimed for them. As, in principle, I would for any experimental result.. although this being the real world, of course results which go against current theory elicit more surprise and therefore more scrutiny both by the original experimentalists (if they're any good) and anyone else looking at the data.
*OK, I'm making a general point here.. I don't personally know enough about GR to be able to make an sort of judgement about it for myself.
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CM is an approximation that works well within certain limits. GR and QM work well outside these limits but have there own limitations (until some new unified theory is proposed). To misquote Clint Eastwood (Dirty Harry), "A theory has to know its limitations".
An analogy: Using cartesian coordinates on a map is fine until the map starts to try to cover a large area where the earth's curvature is significant. It doesn't mean that flat maps are a waste of time. It is just that we have to know their limitations.