Quote:
Originally Posted by Nereid
I'm sure that some of this can be applied to the combined work being done on SMBH+accretion disks+jets+feeding mechanisms+..., but I feel your description simply does not fit most work here.
Is this an area you are sufficiently familiar with that you could comment on it?
|
Probably not. Each subdiscipline has its own culture, and the areas I know best are stellar physics. Still, I'd be surprised if the culture in accretion-disk simulations is so much different. The equation I often see is "observation + theoretical simulation that agrees with observation = completed observational/theoretical synergy, next problem." We can leave the "what happened" issues up to the textbooks for students, and a cartoon level explanation should suffice in many cases.
Now, one can certainly file this under the heading of "pet peeves" and note that this description is not always applicable. Whether it is
mostly applicable or
mostly unfair is also not so obvious, and that question is likely where our disagreement centers. The more conservative way to sum it all up would be to say "let's be on guard against this phenomenon, in case it should rear its head", and paint me as someone akin to the child in the story "the Emperor's New Clothes". It is not my intention to take to task the whole astrophysical community, but rather to point out that sometimes the most fertile possible soil for discovery is found
after one gets simulations that agree with observations, not necessarily while the observations remain mysterious-- even though the latter is where much of the attention gets focused while the former often gets relegated to a kind of "niche" market.
Quote:
|
On the M-L example, though, here's one superficial comment: to what extent are you saying that the theoretical models (kitchen sink and all) are weak because a bunch of 'sanity checks' or 'existence proofs' are missing (or wrong)?
|
I'm not saying the kitchen sink models are weak, indeed I think they must be very strong that they make so many correct predictions. The problem lies in what was done with them once they succeeded in making those predictions. The two main issues that then cropped up were:
1) Since people did not really analyze why they got the results they did, it was not clear how much flexibility existed to fit systematic changes in the observations. There is a tendency to think a theory should fit "the observations", but there really isn't any such animal. The observers don't realize all the optional tweaks the theorists had at their disposal to try and get that agreement, and the theorists don't realize the potential for systematic errors in the observations. (There's an old joke that the observer is the only one who doesn't believe her observations, and the theorist is the only one who does. But I think the first part is actually the one that applies in
both cases.)
So what you find is, some new observational effect is interpreted differently and all the datapoints shift, and sometimes this makes it "in better agreement" with the theory, as if that meant anything, and everyone is happy, or sometimes it makes it in worse agreement, and people get all bothered. But how can this be a source of either contentment or concern until we know what the observational systematics that are still out there might do, or how many free twiddles are still available for the theory? It's kind of a shell game as long as we are dealing with black boxes instead of unifying principles.
2) The answers people arrived at to explain "why" the kitchen sink simulations found that massive stars were more luminous varied from being quite incomplete to being demonstrably false (look for any mention of high pressure or strong gravity in hot stars, or any mention that the elevated temperature causes the luminosity to be higher because of the temperature sensitivity of nuclear burning rates). Yet they are propagated in authoritative places willy nilly, particularly on the web and in the minds of professionals who work with these stars. How can this be? These people are no fools, so it can only be that they never really tried that hard-- they never really cared to know the real explanation that actually happened in the simulation, as long as the cartoon explanation seemed to work.
That's just like people who think the phases of the Moon are caused by the shadow of the Earth-- when a cartoon works because it's never subjected to careful scrutiny, it can flourish and propagate despite being anathema to the goals of science. I'm saying we remain closer to that pitfall than we may realize, whenever we fail to subject simulations to that level of scrutiny, settling instead for cartoon descriptions that "seem to work" on the grounds that what "really matters" is that the
simulation got it right.