Comment by Cupertino95014
4 years ago
One thing that's always irritated me about popular explanations of string theory, like Brian Greene's, is that they'll use phrases like "It turns out that..."
I think, "Wait a second! Nothing has 'turned out', because there are no experiments."
So now there will be. I applaud this effort. If something is untestable, then ignorant people who equate "faith in religion" with "faith in science" are right. Let's get some data that can only be explained by Theory X, and then see if Theory X predicts more things that also turn out to be true. If Theory X turns out to be one of the many variations of string theory, then you've got something there.
'it turns out that' usually means that it follows from a bunch of math that's not worth talking about. Not that it's supported by experiment.
Rather a subtle distinction, when a noted scientist is writing for a lay audience.
Yeah, I agree, I don't think it's a good construction even in the field. It's always more clear and less annoying as a reader if it says "it follows from some math that" or something like that.
In the same vein it bugs me when physicists “explain” the interior of black holes. Until we have a quantum theory of gravity we really don’t know what’s inside a black hole.
Question in this regard: current theory seems to predict a singularity with “infinite” space-time curvature (IIUC) in the center of a black hole. This seems utterly improbable to me. Is it common sense to treat this as a given or is it considered a weird quirk of general relativity that is sought to be overcome?
In this universe of ours, there isn't anything profoundly improbable about a point particle with a mass of a million suns. We commonly treat electron's as point particles with tiny mass - and there isn't yet any hint in theory or experiment that this model is incorrect (when the particles dynamics are calculated through QM).
That being said, physicists dislike discontinuities. A theoretical point particle with high mass means that there must be a mechanism to merge large quantities of mass into black hole matter. If it is a point particle with extremely large gravitational fields, these final interactions would also require some version of quantum gravity to predict. In fact, it's entirely plausible that what we observe as black holes are actually not GR singularities at all https://en.wikipedia.org/wiki/Black_hole#Alternatives
There is hope for improving observational data on black hole interiors by measuring the gravitational waves of merging black holes. Different types of black hole singularities will have different event horizon shapes, and the merger of these black holes should produce different gravitational waves, amongst other observable effects. https://en.wikipedia.org/wiki/Kerr_metric
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It’s generally regarded as major flaw with general relativity - and that general relativity is only an approximation for a better theory.
You don’t need anything as exotic as a black hole, general relativity can’t say anything about how gravity works at small scales at all.