OK, so I admit I occasionally wander around and fill random tests on the web as well. It seems a lot of people do, so what is the harm in admitting it?

This is not a rhetorical question. One might do a bit of social calculus: does filling this test say something about me? What will my colleagues think of me for admitting it? Will I go up or down on their esteem? By how many points? Will they forget quickly or will they remember this and tease me forever?

You get the drift. I’ve already made a major *blunder* and started a blog, so admitting stuff like that will not hurt me more. That is my reasoning. Of course, if you read in between the lines you are probably tabulating my anxiety and updating all the information that you thought you knew about me. This is what people do. All the time. Our brains do that. It is part of the game we play to survive, and since we benefit from social activities, these types of calculations and their outcome determine how we actually behave. In the end, they also determine how successful of an individual we become.

But each of us has a different calculator. So how much does it say about me, and how much does it say about you when you judge me (either way) based on this information?

In some sense this is a post about neurology and brain function. But not a single neuron has been dissected, nor a single brain function has been explained. This is just a teaser to make you think something different for a few seconds. Maybe you can make a whole afternoon worth of chatting based on this input.

As far as I can tell our brains are a reservoir of statistics and we perform a Bayesian inference calculation each time we think. We have a model, and we update it based on the new information. I will postpone a dissection of Bayesian probability for some other day, seeing as I didn’t bring my scalpels today. I inserted that stupid joke there on purpose to irritate some of you, so for those who are irritated go ahead and groan loudly (I’m sure you are reacting right now). I’d say about half of the people who read that line will groan internally and only one in a gazillion will groan out loud, except that I skewed the statistics by telling you, so I can’t believe it anymore either. That’s my guess.

The whole point of Bayesian inference is that we have a previous model (our bias) before we conclude something, and many questions about the a-priori chances of seeing something in a laboratory or concluding something depend on the models that one is using to describe them. So when people say there is a 60 percent chance of seeing supersymmetry at the LHC you are seeing their bias. The truth is we don’t know and the only true statement one can make is this: either we will see it or not, but we can not assign an objective probability to it. Fortunately subjective probabilities can be assigned, and this is what we do when we make those statements. When we give those probabilities, we are indicating how we would bet money on the outcomes of whatever question you might be posing. If you have a lot of information, you can place bets very cleverly. For example, I would bet all the money in the world to assert that the sun will rise tomorrow. I don’t think I could find anyone with any sense that would take that bet and if they did, I would not trust them. So in the end I wouldn’t end up making the bet. Not for that much money anyhow.

I bumped into a music personality test and I got these scores. So what does it really say about me?

DISCLAIMER: For this post to be effective, it needs a fall guy. Seeing as it is impolite to do that to anyone else, I have to choose myself for the job. So you got it right: It’s all about me.

on September 27, 2008 at 8:01 amBeeit says you’re the kind of guy who has time at hand and spends it on a personality test 😉

on September 27, 2008 at 12:11 pmnodrylightErm, about the sunrise thing, here’s an anecdote about the famous British mathematician G. H. Hardy:

“… ‘The subwarden bets Professor Hardy his fortune till death to one halfpenny that the sun will rise tomorrow (7th Feb 1923)’. A couple of days later Hardy took the same bet again, but the odds had shortened significantly – for reasons at which we can only guess. This time it was only half his fortune till death, against on whole penny.”

So it may actually be more lucrative than we might otherwise think.

on September 27, 2008 at 1:53 pmRafaelFun with statistics:

http://abstrusegoose.com/54

http://abstrusegoose.com/55

and I like this one 😉

http://abstrusegoose.com/47

R

on September 28, 2008 at 1:24 amUncle AlThere are 10 kinds of people- whose who speak binary and those who do not.

on September 30, 2008 at 5:26 amMark RYeah, I’ve been noticing this is a pretty big issue. In all the writing, sometimes it’s hard to tell marketing from fact. Almost as hard as telling mathematics from physics.

The writers don’t often provide a good or detailed context for what they’re saying, i.e., what are the epistemological conditions and dependencies? How far “up” on other theories are we standing, and are those more foundational theories equally or more tenuous than our own? This could also be a measure of bias. I think that’s what you were saying when mentioning an a priori result — that is, a result that is independent of a given theory.

It seems to me that talking about anything as a priori where theory is concerned is dangerous unless you’ve very, very detailed about the context of both the theory and the a priori thang. Particularly, the a priori thang.

The big question to me is that a priori bit. Has it been chosen? Or has it been empirically discovered? In other words, again, the epistemology.

As a non-physicist reading lots of physics stuff, I have a very hard time telling what is epistemologically sound — regardless of any math, which itself may or may not be standing on a solid epistemological basis.

I have a hard time telling where the math is connected to physical. I have a hard time telling just how high up math can be stacked, without being able to tell how it’s really connected to the physical.

I mean, I’ve heard lots of physicists berate spiritualists talking all this quantum mumbo jumbo, but I’m not exactly certain that many physicists aren’t much better, except that they’re using wild mathematics and strategic gyrations of it, similarly disconnected from physicality.

I don’t mean this to be another, oh there’s no proof for string theory. I’m kinda asking, in physics, or the physical, how high can we stack up mathematics claiming to talk about the physical without being clear how it’s connected to the physical? It must be fun at least, and engaging.

When considering the most simple and most reasonably achievable things: What would it take to shut string theory down? What would it take to prove it?

I’m also curious, how is it that something unproven like string theory can be the loudest in the public ear? Is it the passion of the people studying it? Is it a purposeful funding tactic? Is it that the public finds it the most fascinating thing, for some reason?

on September 30, 2008 at 1:16 pmdberensteinMark:

Unfortunately there are no clear cut answers to your questions. In most experimental situations there are choices:

1.Either you fit to a pre-existing model, in which case there are usually parameters that describe the model plus a bias based on previous observations that one might want to take into account and then one tries some likelihood fit to improve the measurements of the parameters.

2. You fit to a theoretical curve from somewhere else where everything is given and you can say whether the model fits the data or not.

3. You don’t fit anything and report raw numbers. This is less common, but it is done also, especially in situations where there is a lot of controversy over the details of the underlying theory. We hope to see a lot of papers like this from the LHC if there is new stuff showing up in the accelerator.

As regards to proving or disproving string theory, you have to be in a regime where strings are visible to be able to say aye or nay. The conservative models predict that fundamental strings should be seen (with all their characteristics) at energies close to the 4-d Planck scale. That can not be achieved experimentally in years to come (probably millennia). The LHC is about ten orders of magnitude in energy below where strings could become important, so one can not disprove it by going where you need to go experimentally. However, you can get lucky and see them sooner, so you could prove that strings are there. There are many other less fundamental situations where describing the physics in terms of strings is useful, so one can use ideas from strings to study those situations and make progress. This is not a black and white subject where one can clearly divide theories into string theory and not string theory, because dualities show that many ordinary gauge theories can also be described as string theories in some regimes and we already have a huge amount of experimental evidence for gauge theories. The big question is then if you can do better by using strings and people are working on that.

I think the reason strings stand out in the public eye is because it gives a somewhat complete story of unification and it involves trying to think in higher dimensions. It seems this attracts the public to it. It also has quite a few successes at the technical level that have been distilled for public consumption, especially due to the efforts of Brian Greene, who has done a phenomenal job in communicating the excitement that the string community has for the subject.

on October 1, 2008 at 3:58 amMark RAh, David, thank you. Very much.

It is rare finding an epistemological-ish discussion of strings that is not radically zealous in some way, from some perspective. I really appreciate it.

Before anything else, I do recognize that it is nice to be able to describe things with mathematics and make predictions. No matter which mathematical constructions you would like to use. It can be useful even in “poetic” ways, that can sometimes lead you into new ways of thinking, that might even turn out to be valid for physics.

Let me see if I’m getting this right. It’s very hard to come up with a sensible perspective on string theory, as a theory, from the outside.

In string theory, if the verdict relies upon actually seeing strings, and this possibility is perhaps thousands of years away from happening, it seems we should rule out any possibility, for now, that it is definitively true.

But that doesn’t mean we won’t find strong evidence for string theory before then, particularly through correlations to observation.

By the way, this wouldn’t even be a curious issue for me, except that so much of theoretical physics is currently looking through the lens of string theory — and I’d like to know why. When asked the harder questions (that are actually quite simple and reasonable), physicists tend to spew forth a barrage of mathematics, in a gesture of “you just don’t understand”. I could accept something like that coming from a mathematician. But physicists are supposed to be tied, at least in some way, to the physical universe where I live. And so, I want to thank you again.

Here is my mathematical understanding of string theory. Yes, I know it’s very sad. String theory is an elaborate, purely mathematical construction, that is not at all likely to be true without the further mathematical construction called supersymmetry. It is suspected that this mathematical construction somehow reflects our physical universe, just as many other mathematical constructions have been show to reflect it to varying degrees.

But in order for us to consider this mathematical menagerie valid, we have to look at its correlation to observation. In other words, the aesthetic inherent within its “beauty” is not enough to render it true, as a physical representation of our universe.

One of the criticisms of string theory is that, when confronted with difficulties, more mathematics are simply piled on to smooth away the problem. This can result in some stunning, yet apparently acceptable, alterations to our understanding of fundamental nature of our universe. Such as, tacking on however many extra dimensions to reality we need, to make the math work. A question arises, is it more likely that lots of extra dimensions actually exist, or are we trying to protect an aesthetic we hold dear? And if we say that extra dimensions exist, how many other similar difficulties have we encountered within string theory, and how many other stunning physical implications have we patently accepted in order to preserve string theory? Or, how many extra towers of mathematics have we had to add to string theory to smooth out even further the stunning implications we were left with, such as getting rid of these extra dimensions somehow.

Which comes back to my original question – how high can we stack the mathematics in physics without it being tied to physicality? At what point should we question this?

The ties to gauge theories, which have some observational corroboration are wonderful. It sounds like string theories are tied to gauge theories by “dualities” and these ties are valid for certain “regimes”. Was it a lot of math to work them into being connected? I would imagine that you could use math to work yourself into a connection with just about anything, eventually. I’m not being bitchy…

My sense is, string theory is trying to be the “one stop shop” for physics, with its fingers being written down into every pie, in an attempt at unification. In a way, to become the physics of physics. Except that it’s mathematics, so it’s a little freer. I’m curious, do string theorists choose one and then another of the “older” physics, trying to incorporate that sense into string theory, or does string theory work, in and of itself, and just modifies itself when required, through some confrontation with an “older” physics?

I’m also curious, as a physicist, how do you balance the aesthetic within a functional mathematical complexity against the aesthetic of simplicity? Do physicists suspect that, once all physics is accounted for within string theory, that some greater aesthetic abstraction might be found that turns out to be elegantly simple?

I am also left wondering if physicists might be obsolete, replaced by mathematicians. I know there is a synergy between the disciplines, but mathematicians can do wonders with a few defined constraints.

And finally, in all honesty, in the heart of hearts of a string theorist — does one ever wonder if string theory might actually be the seduction of an aesthetic? And if one does, how does one justify leading so many other people toward string theory?