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> That's practically the definition of what a good scientific theory should do. Put in a single parameter and explain a hundred observed results. [edit] bellow

by tomxor 7y ago

> That's practically the definition of what a good scientific theory should do. Put in a single parameter and explain a hundred observed results. [edit] bellow is wrong (dark matter uses free params), misread from wikipedia see child comment... Conversely entropic gravity uses free parameters, which according to the crushing wikipedia definition is likely to be a product of wishful thinking. A stark difference, although i'm definitely not suggesting this to be some absolute measure of truth - perhaps it is useful to consider the historical context this good scientific quality (which is generally good) emerged from, it's possible it may not be a good fit for theories grounded in emergence and chaos of the very small? disclaimer - not a physicist, obvs.

__MatrixMan__ 7y ago
I could be misunderstanding this sentence, but from the linked page: > Importantly, [entropic gravity] also explains (without invoking the existence of dark matter and its accompanying math featuring new free parameters that are tweaked to obtain the desired outcome) why galactic rotation curves differ from the profile expected with visible matter. I get that entropic gravity doesn't use free parameters. Also, I don't think that free parameters are necessarily so damning. I happen to have more hammocks than usual in my house. Any theory about how hammocks are distributed will either fail to explain the concentration, or will predict that hammocks are more likely to be found near people who like them, and then will subsequently fail to provide a way to derive the location or distribution of those people. That failure would be a free parameter. It's not necessarily an indicator of wishful thinking. It could just be that the theory knows its limits.
- tomxor 7y ago
  > I get that entropic gravity doesn't use free parameters. You are correct, my error in skim reading too fast. > It could just be that the theory knows its limits. Yes that's essentially what I meant by chaos, if you could know enough information you could predict where all your hammocks end up, but that requires vast and subtle knowledge about how you think and minutiae of your environment and how you interact with it that caused you to make arbitrary decisions... the interesting thing about chaos is that it _can_ be deterministic, in other-words, given initial conditions it can be computed - but even then in the context of such large systems that computation is infeasibly and irreducibly costly, in which case (i guess) you use free parameters in combination with what conceptually similar to statistical mechanics?
- rcxdude 7y ago
  > I don't think that free parameters are necessarily so damning Free parameters which significantly outpower the power of the observations are damning because there is no way to falsify the theory: if the theory can explain an extremely wide range of observations by tweaking the free parameters then it has much less predictive power and should be viewed extremely suspicously.
  - __MatrixMan__ 7y ago
    Oh yeah, depending on how they show up, they're a problem. I'm just saying that there are certain non-problematic cases where only a free parameter will do. I think the trouble with dark-matter-as-WIMPs is that the free parameter (the location of those WIMPs) is overpowered: You can say that the extra gravitation is caused by the presence of these particles and leave the details of how those particles got where they are out of your theory. But then when you add "oh, and they can't be detected by any other means" it becomes a problematic free parameter because wait a second, that's the very problem we were trying to solve in the first place. If you can't connect the causal agent to anything besides the problem that necessitated it, then it might as well be a ghost.

by tomxor 7y ago

__MatrixMan__ 7y ago

I could be misunderstanding this sentence, but from the linked page: > Importantly, [entropic gravity] also explains (without invoking the existence of dark matter and its accompanying math featuring new free parameters that are tweaked to obtain the desired outcome) why galactic rotation curves differ from the profile expected with visible matter. I get that entropic gravity doesn't use free parameters. Also, I don't think that free parameters are necessarily so damning. I happen to have more hammocks than usual in my house. Any theory about how hammocks are distributed will either fail to explain the concentration, or will predict that hammocks are more likely to be found near people who like them, and then will subsequently fail to provide a way to derive the location or distribution of those people. That failure would be a free parameter. It's not necessarily an indicator of wishful thinking. It could just be that the theory knows its limits.

tomxor 7y ago
> I get that entropic gravity doesn't use free parameters. You are correct, my error in skim reading too fast. > It could just be that the theory knows its limits. Yes that's essentially what I meant by chaos, if you could know enough information you could predict where all your hammocks end up, but that requires vast and subtle knowledge about how you think and minutiae of your environment and how you interact with it that caused you to make arbitrary decisions... the interesting thing about chaos is that it _can_ be deterministic, in other-words, given initial conditions it can be computed - but even then in the context of such large systems that computation is infeasibly and irreducibly costly, in which case (i guess) you use free parameters in combination with what conceptually similar to statistical mechanics?
rcxdude 7y ago
> I don't think that free parameters are necessarily so damning Free parameters which significantly outpower the power of the observations are damning because there is no way to falsify the theory: if the theory can explain an extremely wide range of observations by tweaking the free parameters then it has much less predictive power and should be viewed extremely suspicously.
- __MatrixMan__ 7y ago
  Oh yeah, depending on how they show up, they're a problem. I'm just saying that there are certain non-problematic cases where only a free parameter will do. I think the trouble with dark-matter-as-WIMPs is that the free parameter (the location of those WIMPs) is overpowered: You can say that the extra gravitation is caused by the presence of these particles and leave the details of how those particles got where they are out of your theory. But then when you add "oh, and they can't be detected by any other means" it becomes a problematic free parameter because wait a second, that's the very problem we were trying to solve in the first place. If you can't connect the causal agent to anything besides the problem that necessitated it, then it might as well be a ghost.