tag:blogger.com,1999:blog-6837159629100463303.post609124390302746985..comments2023-06-18T01:25:08.748-07:00Comments on Information Transfer Economics: Why do macroeconomists think they know what it's like to be a physicist?Jason Smithhttp://www.blogger.com/profile/12680061127040420047noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-6837159629100463303.post-11149902248481502002015-03-19T11:54:11.356-07:002015-03-19T11:54:11.356-07:00Cheers, thanks. I agree that turfs for turfs' ...Cheers, thanks. I agree that turfs for turfs' sake aren't very constructive. It's ok to have e.g. jargon to organize thought, but jargon also builds walls.Jason Smithhttps://www.blogger.com/profile/12680061127040420047noreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-29005909762991221512015-03-19T07:23:57.848-07:002015-03-19T07:23:57.848-07:00Great post. Just to jump in a month later, can I a...Great post. Just to jump in a month later, can I add that macro suffers from one huge problem that afflicts all the social sciences: the discipline are structured horizontally, not vertically, in terms of levels of social organization. The problem becomes that you get turf wars (or tribal wars) rather than learning. Economists, political scientists, and sociologists argue about political economy or organizations, coming at the same thing from different directions, but they cannot learn form each other without getting into trouble over status and legitimacy. If, on the other hand, the social sciences were organized vertically--so you get psychology (cognition), then social psych (small groups), then community studies, then organizational studies, then "macro" (institutions)--then you'd have real research on levels of organization with their own emergent properties, and one level could learn from the other while still doing its own work. I could study small groups on their own terms, and come up with empirical findings and frameworks that explain what I've found in terms of that level of organization--but I would love to know what cognitive psychologists have found out, so that I can make better sense of my level of analysis and maybe discover new directions of study. (I'm thinking of organic chemistry vis-a-vis physics. I can do orgo without knowing thing 1 about QM--but when I know QM, I have an expanded field of vision for making sense of chemical reactions, and I discover a few reaction mechanisms I might not have thought about, so I can do more experiments.)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-51945453753802765902015-02-19T17:33:11.976-08:002015-02-19T17:33:11.976-08:00I would pretty much agree with your assessment.
I...I would pretty much agree with your assessment.<br /><br />I think politics may be the most important driving factor. For example, obfuscation is useful if you're trying to push a policy (sort of the converse of your fifth point), and "useful" in macroeconomics is observer-dependent (per your first point). <br /><br />Additionally, "relevant to everyday life" is pretty much the decisive criterion as to whether expert opinion is trusted on an issue. Living on the west coast of the US, I've had several occasions to assure acquaintances that there is little danger in the US from radioactive material seeping into the Pacific ocean from the Fukushima plant. The response to my 'expert opinion' was generally predictive of the person's political attitude toward nuclear power. I was even accused of being pro-radiation because of my job -- especially funny because my job doesn't actually have anything to do with radiation.Jason Smithhttps://www.blogger.com/profile/12680061127040420047noreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-90256195244529044572015-02-18T11:10:04.537-08:002015-02-18T11:10:04.537-08:00Likely since you wrote the second linked post on f...Likely since you wrote the second linked post on fermions, the hive mind that is wikipedia has added some great visualizations of the topology of spinors:<br /><br /><a href="http://en.wikipedia.org/wiki/Spinor" rel="nofollow">http://en.wikipedia.org/wiki/Spinor</a><br /><br />Indeed you can rotate a spinor by 360 degrees and end up with a minus sign, requiring 720 degrees to return to the original wavefunction.<br /><br />One of the confusing things about half-integer spin is that its fundamental represensation SU(2), the half integer spin rotation group, is a covering group of SO(3), the whole integer spin rotation group, so you can do the rotation by 360 degrees -- thinking about it as SO(3) -- but come out with the weird phase of -1.<br /><br />The Pauli exclusion principle comes from the commutation relations, and is actually a relativistic quantum effect (the spin-statistic theorem). The rotations above are non-relativistic. Although not fully accurate, a kind of thought experiment to use is that you are 'boosting' (changing reference frame) past a spinning particle. Looking at the Earth from above the north pole it spins counter clockwise, but looking at it from above the south pole, it spins clockwise. These 'boosts' are 'rotations' the SO(3,1) group that makes up Lorentz symmetry (special relativity).<br /><br />Later on in physics one uses <a href="http://en.wikipedia.org/wiki/Grassmann_number" rel="nofollow">Grassman number-valued fields</a> (speaking of another non-expert who made contributions to physics) to do relativistic quantum mechanics (i.e. quantum field theory). This helps to clear up the subtleties.<br /><br />The overall problem is that the Pauli exclusion principle tends to be taught as non-relativistic quantum mechanics, so it has aquired some incorrect explanations. It should be taken as an empirical fact (as you mention in your blog post) in non-relativistic quantum mechanics.Jason Smithhttps://www.blogger.com/profile/12680061127040420047noreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-27734006852283348982015-02-18T09:39:29.121-08:002015-02-18T09:39:29.121-08:00I still owe you a reply to an earlier post. I hav...I still owe you a reply to an earlier post. I haven’t got round to it yet but I haven’t forgotten.<br /><br />This post is about what it means to be an expert. An expert is not someone who says they are an expert. Some people say they are experts at forecasting by reading crystal balls. They are not experts. They are crazy.<br /><br />An expert is someone acknowledged BY OTHER PEOPLE as an expert. Physicists are acknowledged as experts by other people. Why?<br /><br />First, they have a track record of doing useful things like harnessing electricity or nuclear power.<br /><br />Second they appear to be ethical. The guys at Cern declared victory only when they had observed a Higgs Boson (or whatever).<br /><br />Third, although I’m sure that physicists disagree with each other, they don’t suggest that we try experiments on broader society to help them in their research.<br /><br />Fourth, current research is mostly irrelevant to everyday life so the rest of us don’t care if physicists are wrong in these areas. Also, we have no independent way of knowing whether, say, the Big Bang is true, as we have no way of observing it ourselves except via the experts.<br /><br />Fifth, physicists seem to like to explain their ideas in everyday language. Einstein said “if you can’t explain an idea to a six year old then you don’t understand it yourself”. The rest of us think that Einstein was smart.<br /><br />The most likely issue that the public will have with physics is that research seems to be becoming more expensive but achieving fewer results. Maybe one day the rest of us will pull the plug on funding physics research. However, physicists have built up such trust and goodwill over a few hundred years that this will probably take a long time.<br /><br />Contrast this with macro-economics. There are so many issues that it’s hard to know where to start. Think of the economist who said that economists had solved the problems of macro-economics a few years before the current crisis – and he was a Nobel prize winner! What about the guys who issued warnings about government debt over 90% of GDP without checking their own spreadsheet calculations! Anyone can make a mistake in a spreadsheet. That’s why professionals add check totals to their spreadsheets to ensure internal consistency and, when it’s important, get two people to develop the same spreadsheet and then compare results to check for errors. <br /><br />Take another example of people who are acknowledged as experts – seismologists. They know what happens during earthquakes and why earthquakes occur in some places but not others. They can measure earthquakes and provide warnings when they occur. They can give advice on the risks associated with building in earthquake zones. However, they can’t forecast earthquakes and they can’t prevent them. This comes back to ethics. They don’t pretend they can do things that they can’t do. This is essential in order to maintain public trust.<br /><br />Earthquakes are rare events. Seismologists could establish a good forecasting track record by predicting ‘no major earthquake in San Francisco tomorrow’. I think I am correct that there have been no major earthquakes in San Francisco for about 25 years, so a seismologist who made this prediction daily would have been correct thousands of times in a row. However, predicting the absence of a rare event is what the rest of us would assume anyway. Only forecasting the occurrence of the rare event is useful. Seismologists can’t do that and they tell us so.<br /><br />Compare that with economists. In practice, their forecasts often say little more than ‘tomorrow’s economy will be the same as today’s economy give or take a little’. That’s not useful as it’s what the rest of us would assume. As with seismology, forecasting the rare event would be useful but they can’t do it. Nevertheless, economists try to pretend that their mathematical models are useful in a way that seismologists do not.Jamienoreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-22136850830548365732015-02-17T21:44:24.889-08:002015-02-17T21:44:24.889-08:00I too was thinking about Krugman (almost) always b...I too was thinking about Krugman (almost) always being right. It is a fact that there are a few economists who make accurate important predictions about what will go wrong. The predictions are implications of standard DSGE models. I think my distress was caused by your use of the words "Keynes" and "Samuelson". The problem is that the points where there is a lot of evidence that Krugman understands the economy better than policy makers are exactly the points where Krugman says exactly the same things Keynes and Samuelson said. <br /><br />Something which is new is that the arguments are contensted by extremely prominent economists (Lucas, Prescott and Fama just to stick with people who won the Sveriges Riksbank Nobel memorial prize). I think this wasn't true in the 1960s. So macroeconomists have contributed more than nothing but, I think, clearly worsened in my lifetime.<br /><br />I came here to confess to some amateur physics (and very much on the usual topics for amateurs).<br /><br />http://rjwaldmann.blogspot.it/2003/12/another-locally-realistic-violation-of.html<br /><br />http://fistfulofeuros.net/afoe/fermions/<br /><br />Roberthttps://www.blogger.com/profile/14455788499385673507noreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-24674065470265736982015-02-17T20:47:33.812-08:002015-02-17T20:47:33.812-08:00I was thinking maybe Noah does not want to spoil t...I was thinking maybe Noah does not want to spoil the gravy train of the centrally managed econ job market.<br /><br />http://noahpinionblog.blogspot.com/2012/02/how-i-survived-economics-job-market.htmlTodd Zorickhttps://www.blogger.com/profile/10976192775890569092noreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-34874464104375999182015-02-17T20:38:08.131-08:002015-02-17T20:38:08.131-08:00I was thinking maybe Noah does not want to spoil t...I was thinking maybe Noah does not want to spoil the gravy train of the centrally managed econ job market.<br /><br />http://noahpinionblog.blogspot.com/2012/02/how-i-survived-economics-job-market.htmlTodd Zorickhttps://www.blogger.com/profile/10976192775890569092noreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-45275102374263438322015-02-17T18:27:02.682-08:002015-02-17T18:27:02.682-08:00Cheers, Robert. I think I had this piece by Noah S...Cheers, Robert. I think I had this piece by Noah Smith in mind:<br /><br /><a href="http://noahpinionblog.blogspot.com/2012/03/scientific-failures-particle-physics-vs.html" rel="nofollow">http://noahpinionblog.blogspot.com/2012/03/scientific-failures-particle-physics-vs.html</a><br /><br />It's not that Noah gets things badly wrong or anything in his (interesting) post, it just seems like the pros and cons of string theory are given from the point of view of someone who hasn't had a class in string theory. The converse is <a href="http://informationtransfereconomics.blogspot.com/2013/04/the-philosophical-motivations.html" rel="nofollow">here</a> where a physicist doesn't quite grasp the allure of DSGE models :)<br /><br />Otherwise, I think the only reason I understand any economics at all is because Noah was once a young physicist and so writes about things in a way that makes sense to my own enforced order on the world ...<br /><br />I don't think macro is as broken as you seem to think it is, but maybe that is just me being new to the field. Even though I'm coming at it from a <a href="http://informationtransfereconomics.blogspot.com/2015/01/i-strongly-disagree-with-what-you-are.html" rel="nofollow">weird angle</a>, there is much that seems fine on the face of it (e.g. Paul Krugman is always right).Jason Smithhttps://www.blogger.com/profile/12680061127040420047noreply@blogger.comtag:blogger.com,1999:blog-6837159629100463303.post-83689909693518385982015-02-17T17:23:36.359-08:002015-02-17T17:23:36.359-08:00Thanks for the link. I think that Noah Smith know...Thanks for the link. I think that Noah Smith knows a lot about physics (an undergraduate education in physics implies learning a lot). having an undergraduate education in biology, I really wouldn't know.<br /><br />I stress again, as you did, the word "diplomatic". Noah Smith hasn't always been diplomatic. He was planning to be a macroeconomist then decided it was garbage. In other posts he is very frank, even rude.<br /><br />I think you are a bit kind to us macroconomists. Yes it is a new field, but it has managed to worsen over time. It is barbarous and decadent, undeveloped and schlerotic (but it pays my mortgage).Roberthttps://www.blogger.com/profile/14455788499385673507noreply@blogger.com