No, I really understand curved spacetime. And to be brutally frank, you don't.I think your arguments really do tend to suggest otherwise.
No, let's not.Heaviside's interesting (at the time) speculations have of course been superceded by the approximation scheme in GR which I described above. Let's not muddy the waters with his outdated model, and just stick to gravitoelectromagnetism (henceforth "GEM", and I'll abbreviate plain electromagnetism to "EM").
I have. And as I've said previously, space is not falling inwards in a gravitational field. We do not live on a Chicken-Little Earth. The sky is not falling in. The waterfall analogy is specious pseudoscience peddled by quacks.That aside, I find it very interesting that you cleave so tightly to the analogy which is only ever an approximation, but reject with such vehemence the one which is actually exact in the few situations where it applies. I have to wonder whether you have properly grasped either.
It isn't. We are all familiar with the concepts of mass and charge. And we are all aware that a concentration of energy causes gravity.Hmm, I think that calls your claim to understand the GEM-EM analogy into serious doubt. Did you realise that your sentence above is exactly synonymous with "I'm not fond of the concept of mass"?
Because it's an abbreviated way of saying I take issue with gravitational charge for a number of reasons.ETA: And I have to ask this general question: why would your fondness for an idea have any relevance at all in a rational argument about its value?)
No.Ah, you think the differences I mentioned are irrelevant to the GEM-EM analogy.
I know it. And I know exactly why test masses fall and why test charges accelerate.ctamblyn said:Let's start with the second difference. The fact that test masses all fall at the same rate in gravitational fields while test charges accelerate at different rates in electromagnetic fields is just as valid in GEM as it is in full GR. My apologies - I assumed you would already know this.
We know the mathematical approaches are different. What we are examining is the similarity between and electromagnetic field and a gravitomagnetic field.Now for the first difference (the non-linearity of GR vs. the linearity of EM). This should serve to remind us that what underlies GEM is radically different from what underlies EM, and that the equations of GEM (unlike those of EM) are applicable only to small perturbations of a background field.
I said the principle of equivalence was an "enabling principle". It applies to an infinitesimal region. Which means it doesn't apply at all. A real gravitational field is not equivalent to accelerating through space, you cannot transform it away.An amusing aside: to be consistent with your comments on local flatness earlier in this thread (e.g. see the last paragraph of this post), perhaps you should now be proclaiming that "this means they don't apply at all!"
You've said nothing. Apart from a load of wishy-washy guff urging me to ignore Heaviside. As well as Maxwell and Minkowski and Einstein? Strewth.ctamblyn said:Both differences (and there are also many others) demonstrate that the GEM analogy is, like all analogies, limited. It would be unwise to take it too seriously, just as it would be unwise to take the waterfall analogy too seriously (a statement with which I'm sure you agree).
As you are to Anders Lindman, so am I to you.