B Questions about dark matter/energy

[Ken G]

It seems like you are agreeing with me; you just don't like calling this process "picking a model with the simplest parameterization".

No I do like calling it that; that's exactly what I did call it.

I can't understand why you object to that phrasing, but in any case, what Planck did is an example of what I was describing.

Perhaps we are saying the same thing then, it sounded like you were contracting what I said. But that's what I said, it was an example of what Planck did. I'm merely wondering if MOND is in a similar boat at the moment-- picking a simple parametrization, and waiting for the Schroedinger equation to come along later.

My point about "models" is that different models (what I'm calling models) have different parametrizations. There might be more than one model that just has one adjustable real parameter, for example--more than one model in the sense of more than one mathematical engine that makes predictions, and the predictions can be different for different models even if they both have just one adjustable real parameter. Even if you just view what is being done as a "mathematical trick", as Planck did, there can still be multiple different "mathematical tricks" you can play with one adjustable real parameter. So you can't just describe what is being done as "pick the simplest possible parametrization, just one adjustable real parameter". You still have to describe what is being done, mathematically, with that parameter: what equation or equations does it get plugged into? What are the resulting predictions? All that is part of what I was calling a "model". If you don't like the word "model" to describe that, well, suggest some other word. But you can't just ignore it.

I'm not disputing any particular meaning for the word "model," that is of no consequence to me. At issue is simply the paths progress can take, which sometimes flow from looking for the simplest parametrization first, and then later trying to understand why it worked-- if it did. In other words, it is often not necessary to decide what model one prefers, on any kind of physical grounds or any philosophical basis at all, one can simply follow the parametrization that seems to be getting more bang from its buck than would be expected if it was a dead end. Some MOND followers are seeing reasons to think the simple a_o type parametrization is getting such bang, at least to a surprising degree. So that could be that phase of the process.

Again, you are agreeing with me here, since this is what I said might happen with MOND. Or it might not. We'll see.

I certainly agree that none of us have the necessary crystal ball to know where it will go, the issue is not to predict the future but rather to frame the status of the present. I think the main error to avoid is to try to decide if one prefers a solution involving a new parametrization of gravity, versus a solution that involves invisible particles. There is no reason to prefer anything, we just look under all the streetlights first, preferences are simple biases. An individual has to decide where to put their energy, that's true, but people mistake preferences for evidence sometimes. It's like some people pointing at the Bullet Cluster and other people pointing at other clusters that behave differently, when does evidence get confused with preference?