Fads and Fallacies in the name of Theory

[oldman]

Long ago Martin Gardner, a columnist for Scientific American, wrote Fads and Fallacies in the name of Science, which some readers of this forum may have come across. He wrote of the astonishing gullibility of the public at large, and described many ways in which such folk had been conned by mumbo-jumbo parading as science.

I sometimes wonder if we physics folk should trust theorists as much as we do, and mention two cautionary examples here. They have to do with the configuration of the solar system, which I assume readers are quite familiar with.

The first example is Kepler's astonishingly convincing numerology. Most of us know him as the inventor of the three laws of planetary dynamics, which which we know, admire and accept -- apart from some tiny general relativistic quibbles. But Kepler had first, in 1595, dabbled in numerology. As most folk know, he modeled the arrangement of the first six planets by packing between their circular orbits the five Platonic solids, for example a Cube into the gap between spheres on which lay the orbits of Jupiter and Saturn and so on. All mysteriously geometrical stuff, like pyramidology.

But what few appreciate is how convincing this numerology was. Apart from a systematic error of about 24% (to be forgiven because all this was long ago!) the fit between modern data and his modelling is 99.9% correct (as shown in the attached graph). Would modern theorists not be impressed by the fit and quickly find a mechanism to explain such a systematic discrepancy? I fear so.

The second example is how naturally theoreticians ignore prominent things that are difficult or tedious to explain. For example the orbits of these same planets are all very nearly circular; not prominently elliptical. Only in Mercury's case does its distance from the sun vary by as much as 2% as it orbits. The reason for this circularity is is surely physical and historical and has nothing to do with numerology. But nowhere have I come across an discussion, however qualitative, of this important aspect of our local environment!

Before venturing into string theory or accepting such theoretical prejudices as the anthropic principle, I recommend a dose of martin Gardner.

 

[CompuChip]

The second example is how naturally theoreticians ignore prominent things that are difficult or tedious to explain. For example the orbits of these same planets are all very nearly circular; not prominently elliptical. Only in Mercury's case does its distance from the sun vary by as much as 2% as it orbits. The reason for this circularity is is surely physical and historical and has nothing to do with numerology. But nowhere have I come across an discussion, however qualitative, of this important aspect of our local environment!

Before venturing into string theory or accepting such theoretical prejudices as the anthropic principle, I recommend a dose of martin Gardner.

I would like to point out that your example is not an example. At least, it's not valid for me until you can explain how "nearly circular" contradicts being elliptical and why you think that even slightly elliptical can be better described by circular than elliptical. The theory provides us with a parameter (eccentricity) which allows us precisely to describe how much non-circular the orbits are and allows us to calculate it on physical grounds, thereby explaining precisely why it should have the value it has for certain planets.
Also, I never heard anyone claim that they are "prominently elliptical".

Before venturing into "philosophy" (if you wish to call it that) and Martin Garner, I recommend a dose of good physics books.

 

[oldman]

I...would like to point out that your example is not an example. At least, it's not valid for me until you can explain how "nearly circular" contradicts being elliptical and why you think that even slightly elliptical can be better described by circular than elliptical. The theory provides us with a parameter (eccentricity) which allows us precisely to describe how much non-circular the orbits are and allows us to calculate it on physical grounds, thereby explaining precisely why it should have the value it has for certain planets.
Also, I never heard anyone claim that they are "prominently elliptical".

Before venturing into "philosophy" (if you wish to call it that) and Martin Garner, I recommend a dose of good physics books.

I'm being badly misunderstood here. Let me take your destruction of my second example here, Compuchip. I do know all about eccentricity (remember this is a so-called crackpot talking!) Eccentricity is a slightly obscure parameter to write about in this context, though. Not everyone grasps what the Earth's orbital eccentricity of 0.0167 means for the shape of its orbit. Despite your quibble about its actually being an ellipse (of course it is), the orbit is indeed "nearly circular" --- just that. If it weren't we'd have some serious weather to contend with.

As to a "prominently elliptical' orbit --- try the orbit of Halley's comet. The word also means "particularly noticeable". This orbit is an ellipse that is noticably non-circular. It's not only politicians who are "prominent"!

Rather crush me by pointing out why planetary orbits are nearly circular and not prominently elliptical. Can you do this? Say by referring me to a good physics book?

 

[ThomasT]

... why planetary orbits are nearly circular and not prominently elliptical. Can you do this? Say by referring me to a good physics book?

My first thought was that the orbits are nearly round for the same reason that planets and stars are nearly round (not to mention the 'circulation' of tornadoes and and hurricanes and whirlpools, etc.).

A tentative answer is hydrostatic equilibrium. But I don't know much about this, so you're on your own unless one of the Mentors or Science Advisors jumps in.

Here's a link that might help:

Extension of the Kepler problem towards minimization of energy and gravity softening


I don't understand what all the fuss is about. Although you might have posted your main question in the astrophysics forum -- minus the editorializing.

Personally, I've always thought that theorists were full of it.

However, they are necessary -- and besides, they give us lots of stuff to argue about.

 

[CompuChip]

However, they are necessary -- and besides, they give us lots of stuff to argue about.

Even more, they can give you stuff to experiment on. Without theory, experiments are like kindergarten: just playing around for the sake of playing around. The opposite is also true, of course, only then people tend to call it mathematics

Eccentricity is a slightly obscure parameter to write about in this context, though. Not everyone grasps what the Earth's orbital eccentricity of 0.0167 means for the shape of its orbit. Despite your quibble about its actually being an ellipse (of course it is), the orbit is indeed "nearly circular" --- just that. If it weren't we'd have some serious weather to contend with.

Either I can't read or we seem to agree.
Yet I think your example is not valid, and you think it is...

As to a "prominently elliptical' orbit --- try the orbit of Halley's comet. The word also means "particularly noticeable". This orbit is an ellipse that is noticably non-circular. It's not only politicians who are "prominent"!

I know what prominent is. But I don't see why the orbits of our planets being nearly circular instead of prominently elliptical is special. As you point out, there are also objects whose orbits have a very large eccentricity. I suppose sustaining life on them is much harder though

Rather crush me by pointing out why planetary orbits are nearly circular and not prominently elliptical. Can you do this? Say by referring me to a good physics book?

Well if I look at the formula at http://en.wikipedia.org/wiki/Eccentricity_vector, it involves angular momentum. So probably the stuff that made up our planets had less angular momentum because it was created from a slowly moving cloud of junk close to the sun, rather than moving very rapidly and being flung around the solar system by gravity.
However, I'm not an astrophysicists (and I don't intend to be one) so this is just speculation. No doubt there are qualified people around here who can give you the details.

 

[Math Is Hard]

I've just spent considerable time pruning some hostile and inane responses in this thread.

If you can't compose yourself enough to offer a mature and thoughtful response, please refrain from posting here. Thanks!

***********************

Now aside from that, if I recall correctly, back in Kepler's day, astrology and numerology were not only acceptable studies, but good ways to make for astronomers to make a living on the side. Also, Kepler assisted Tycho Brahe who did recordings of many painstaking hours of observation of the positions of heavenly bodies.

What I recall about numerology (from reading many books about it during a high school fixation) is that it is very malleable in interpretation, the way that astrology is.

So here's my speculation: could it be that Kepler was just doing old school Brahe-style observation and massaging numerology interpretations to fit these records? Could there have been any benefit to "cooking the numerology books" to meet with a numerology-loving benefactor's expectations?

I guess what I am asking is: did he really believe in this stuff?

 

[Cyrus]

Aww, I'm sorry MIH and Oldman. I'm cranky. :(

 

[CompuChip]

I guess what I am asking is: did he really believe in this stuff?

I guess an equally good question is: even if he did, can we blame him?

If in 100 years from now we have a theory that explains quantum gravity and quantum field theory, which doesn't look like string theory at all, will people laugh at all of us for having spent so much time on that nonsense?

 

[ZapperZ]

I'm being badly misunderstood here. Let me take your destruction of my second example here, Compuchip. I do know all about eccentricity (remember this is a so-called crackpot talking!) Eccentricity is a slightly obscure parameter to write about in this context, though. Not everyone grasps what the Earth's orbital eccentricity of 0.0167 means for the shape of its orbit. Despite your quibble about its actually being an ellipse (of course it is), the orbit is indeed "nearly circular" --- just that. If it weren't we'd have some serious weather to contend with.

As to a "prominently elliptical' orbit --- try the orbit of Halley's comet. The word also means "particularly noticeable". This orbit is an ellipse that is noticably non-circular. It's not only politicians who are "prominent"!

Rather crush me by pointing out why planetary orbits are nearly circular and not prominently elliptical. Can you do this? Say by referring me to a good physics book?

If this is what you intended to discuss, then shouldn't this be done in one of the physics forums and NOT, of all places, in the Philosophy forum?

The fact that the discussion has now gone into this avenue instead of the criticism of "theorists" probably revealed that the example given either isn't valid, or is not representative of what you are trying to illustrate.

If we wish to come back to the original issue, then you might want to consider a major omission of your premise - experimental evidence. Even theorists such as Harry Lipkin had brought up the issue of experimental evidence being the major force in guiding our advancement in knowledge (see his "Who Ordered Theorists?" essay in Physics Today). In addition, practically all of condensed matter theorists are "slaves" to experimental evidence.

So I do not see how such sweeping generalization of theorists can be made. And anyone who has been on this forum long enough will tell you that I've butted heads with theorists all the time.

Zz.

 

[oldman]

If this is what you intended to discuss, then shouldn't this be done in one of the physics forums and NOT, of all places, in the Philosophy forum?

The fact that the discussion has now gone into this avenue instead of the criticism of "theorists" probably revealed that the example given either isn't valid, or is not representative of what you are trying to illustrate...

So I do not see how such sweeping generalization of theorists can be made.

Zz.

First, thanks for the moderating, Zz-- and Maths Is Hard : thanks for time spent pruning. It's appreciated.

Second, what I thought was a comment on the philosophy of physics: that is to say on attitudes that "guide one's behavior towards a subject" (OED meaning of philosophy #3), turned out to be inappropriate. I apologise to those who took it as such. Physics is a subject that I've spent a lot of time with, value highly and wish well. The comment I made was: "I sometimes wonder if we physics folk should trust theorists as much as we do..." It was meant to be milder than a sweeping generalisation.

Third, the two cautionary examples I gave don't rank as questions to be answered by philosophy forum readers. They were chosen rather to illustrate the (in my view) sometimes untrustworthy behaviour of theoreticians.. They're human too, after all.

About Kepler: he's to be admired for abandoning the numerology he first concocted. All the more because the fit it gave to observational data was at first sight pretty good. I have been surprised at just how good (hence the graph I attached). Lots of people (myself included) might easily have seduced by such a fit; Kepler wasn't. In the end he found a better answer, via Tyco Brahe's observations. Shows how vigilant one has to judging good fits of theoretical models to data -- a cautionary example, I think..

About circular orbits (and more). The orderliness and stability of the solar system over billions of years must have been crucial for our evolution. But, as far as I'm aware, theoreticians have not yet attempted to model the details of how this order emerged from the chaotic dust cloud that formed with the sun. Possibly because computer simulations of the ways in which larger-scale condensations arose from the collapse of dark and baryonic matter are easier to get grants for? Or more fascinating? I don't really know -- but this looks to me like another cautionary example of how theoreticians can sometimes ignore striking aspects of the world we find ourselves in.

I hope this clarifies what I was getting at in my OP, for anyone who is still reading this stuff.

 

[oldman]

I suppose sustaining life on them is much harder though

Or even evolving life. To me, that's why this seems a problem worth solving, but it's strange that computer modelling of it isn't more evident. You may be right when you say:

...probably the stuff that made up our planets had less angular momentum because it was created from a slowly moving cloud of junk close to the sun, rather than moving very rapidly and being flung around the solar system by gravity.
No doubt there are qualified people around here who can give you the details.

I'm just not sure about the "no doubt" bit.

 

[oldman]

...I'm cranky

Join the club! Thanks, Cyrus.

 

[George Jones]

About circular orbits (and more). The orderliness and stability of the solar system over billions of years must have been crucial for our evolution. But, as far as I'm aware, theoreticians have not yet attempted to model the details of how this order emerged from the chaotic dust cloud that formed with the sun.

Although I know of no specific technical references (a hole on my shelf that I should fill), I would be shocked to find out that theorists have not attempted to model this, and The Cosmic Perspective (a good astronomy book for non-science majors) states:

"The formation of the spinning disk explains the orderly motion of our solar system today. The planets all orbit the Sun in nearly the same plane because they formed in the flat disk. The direction in which the disk was spinning became the direction of the Sun's rotation and the orbits of the planets. Computer models show that the planets would also rotate in the same direction as they formed ... though the small sizes of the planets compared to the entire disk allowed some exceptions to arise. The fact that collisions in the disk tended to make orbits more circular explains why most planets in our solar system have nearly circular orbits."

I doubt that the authors pulled the last sentence out of thin air.

 

[ZapperZ]

First, thanks for the moderating, Zz-- and Maths Is Hard : thanks for time spent pruning. It's appreciated.

Second, what I thought was a comment on the philosophy of physics: that is to say on attitudes that "guide one's behavior towards a subject" (OED meaning of philosophy #3), turned out to be inappropriate. I apologise to those who took it as such. Physics is a subject that I've spent a lot of time with, value highly and wish well. The comment I made was: "I sometimes wonder if we physics folk should trust theorists as much as we do..." It was meant to be milder than a sweeping generalisation.

Third, the two cautionary examples I gave don't rank as questions to be answered by philosophy forum readers. They were chosen rather to illustrate the (in my view) sometimes untrustworthy behaviour of theoreticians.. They're human too, after all.

About Kepler: he's to be admired for abandoning the numerology he first concocted. All the more because the fit it gave to observational data was at first sight pretty good. I have been surprised at just how good (hence the graph I attached). Lots of people (myself included) might easily have seduced by such a fit; Kepler wasn't. In the end he found a better answer, via Tyco Brahe's observations. Shows how vigilant one has to judging good fits of theoretical models to data -- a cautionary example, I think..

About circular orbits (and more). The orderliness and stability of the solar system over billions of years must have been crucial for our evolution. But, as far as I'm aware, theoreticians have not yet attempted to model the details of how this order emerged from the chaotic dust cloud that formed with the sun. Possibly because computer simulations of the ways in which larger-scale condensations arose from the collapse of dark and baryonic matter are easier to get grants for? Or more fascinating? I don't really know -- but this looks to me like another cautionary example of how theoreticians can sometimes ignore striking aspects of the world we find ourselves in.

I hope this clarifies what I was getting at in my OP, for anyone who is still reading this stuff.

I still don't understand the issue here. Theorists chased a lot of dead ends. And so do experimentalists for that matter, except that we (experimentalists) don't chase as many dead ends because most of what we do require a lot of money, and we have to be very careful of what we pursue and be able to justify them. Theorists, by their nature (and any theorists are welcome to jump in - don't expect an experimentalist to defend you for very long!), can pursue a lot of things simply to explore how far they can go and how "wrong" they can get. There's nothing wrong with that because knowing what is wrong is some time as important and knowing what is right. There are many theories and ideas that remained unverified for a long time. So just because it can't be shown to be valid right there and then doesn't mean such an exercise is futile.

I still don't see why such a thing is prevalent that this is an issue. The largest field of study in physics is condensed matter, and there's A LOT of theorists there. Do you see them doing what you just described? If not, then you are picking some small section of the theorists population and painting all theorists as behaving like these minorities. Is this fair?

Zz.

 

[turbo]

I still don't understand the issue here. Theorists chased a lot of dead ends. And so do experimentalists for that matter, except that we (experimentalists) don't chase as many dead ends because most of what we do require a lot of money, and we have to be very careful of what we pursue and be able to justify them.

ZZ, the experimentalists in high-energy physics have been chasing the Higgs Boson for a long time, and once the existence of that particle has been ruled out at higher and higher energies, new experiments are proposed, new projects are designed and funded, and more money, time, and intellectual capital is spent chasing the Higgs. What if it is not a viable concept? I think that this is a valid example of what the OP asked.

Do we need a particle to convey mass to other particles (mechanism unknown at this time) so that the particles know how to interact with each other? And do we need gravitons to mediate those interactions once the particles have been granted mass by their interactions with Higgs bosons? Things are getting messy.

 

[ZapperZ]

ZZ, the experimentalists in high-energy physics have been chasing the Higgs Boson for a long time, and once the existence of that particle has been ruled out at higher and higher energies, new experiments are proposed, new projects are designed and funded, and more money, time, and intellectual capital is spent chasing the Higgs. What if it is not a viable concept? I think that this is a valid example of what the OP asked.

No, it isn't. We have only recently gotten into the energy domain that the Higgs might be detected. Even so, the Tevatron can only look at the Higgs if the lower energy limit is correct. We still don't know if it is there.

If the LHC doesn't find the Higgs, I can easily see that physicists will have to rethink about what went wrong. In fact, many theorists have said that while finding the Higgs would be exciting, NOT finding it would be even more fascinating, because it tells us that we are missing some new physics that we haven't thought of.

So if it is not viable, we will do something else! But until we try looking for it, no one, not even you, will know whether it is there.

Do we need a particle to convey mass to other particles (mechanism unknown at this time) so that the particles know how to interact with each other? And do we need gravitons to mediate those interactions once the particles have been granted mass by their interactions with Higgs bosons? Things are getting messy.

Who ever told you that things must be in simple, easy terms?

I can show you how the mass of an electron in a semiconductor is endowed by other particles around it. How come you never complain about that while you use it in your modern electronics? You didn't appear to have an issue accepting that concept.

Zz.

 

[oldman]

...Theorists chased a lot of dead ends. And so do experimentalists for that matter, except that we (experimentalists) don't chase as many dead ends because most of what we do require a lot of money, and we have to be very careful of what we pursue and be able to justify them. Theorists, by their nature (and any theorists are welcome to jump in - don't expect an experimentalist to defend you for very long!), can pursue a lot of things simply to explore how far they can go and how "wrong" they can get. There's nothing wrong with that because knowing what is wrong is some time as important and knowing what is right. There are many theories and ideas that remained unverified for a long time. So just because it can't be shown to be valid right there and then doesn't mean such an exercise is futile.

Yes, I agree with what you say --- up to a point --but what about string theory?

I still don't see why such a thing is (so?) prevalent that this is an issue. The largest field of study in physics is condensed matter, and there's A LOT of theorists there. Do you see them doing what you just described? If not, then you are picking some small section of the theorists population and painting all theorists as behaving like these minorities. Is this fair?

Zz.

No, I guess not. So I'll have to think of cautionary examples of where theory has proved to be untrustworthy, or perhaps too contentious to be trusted, in condensed matter physics. I can think of a few possible candidates --- but I don't want to enrage this community , too --- so please take these comments lightly. Here goes: would the time spent and heat generated in arguments (think P.W.Anderson) about the theory of high temperature superconductors fit? And would the extended but contentious and futile efforts to explain the simple and technically important phenomenon of strain hardening in metals (still quite unresolved) qualify as a cautionary example?

I believe that theory and observation should progress together --- it's like building a bridge --- cantilevers of theory should not be projected too far over gulfs of ignorance -- they must supported by piers of experiment and obsrvation placed at intervals. I just think that these intervals are smaller than than some theorists accept.

 

[oldman]

Although I know of no specific technical references (a hole on my shelf that I should fill)..."The fact that collisions in the disk tended to make orbits more circular explains why most planets in our solar system have nearly circular orbits."

I doubt that the authors pulled the last sentence out of thin air.

I guess you're right. Since the last sentence takes as fact that collisions promote circularity there must be good reasons for saying so. It also sounds very plausible. If you ever fill that hole on your shelf, I'd like to hear how this conclusion was reached. Circularisation from chaos sounds as if it is one of those auto-catalytic processes that always seem to underlie evolution towards order. Thanks, George.

 

[turbo]

No, it isn't. We have only recently gotten into the energy domain that the Higgs might be detected. Even so, the Tevatron can only look at the Higgs if the lower energy limit is correct. We still don't know if it is there.

I'm 56, and I have been around long enough to watch the energy-level goal-posts get moved over and over again so that failures to statistically detect the Higgs in collider interactions have been pushed so that now accelerator-energies available in the Tevatron are considered marginal and the group is in a race to pull together some sort of positive results before the LHC comes on line. The detection of Higgs bosons was expected far below Tevatron energies for years and the energies were pushed higher and higher in response to non-detection.

Is it even remotely possible that we do not need yet another particle to convey a fundamental property (mass) to all other particles? I hope you will venture a "yes" here.

If the LHC does not detect a reliable Higgs-mass signature during its life-time, do we demand lots more research money and build an accelerator that encompasses all of Australia, or do we re-group and modify theory? I hope for the latter. I fear the former.

 

[ZapperZ]

I'm 56, and I have been around long enough to watch the energy-level goal-posts get moved over and over again so that failures to statistically detect the Higgs in collider interactions have been pushed so that now accelerator-energies available in the Tevatron are considered marginal and the group is in a race to pull together some sort of positive results before the LHC comes on line. The detection of Higgs bosons was expected far below Tevatron energies for years and the energies were pushed higher and higher in response to non-detection.

Is it even remotely possible that we do not need yet another particle to convey a fundamental property (mass) to all other particles? I hope you will venture a "yes" here.

If the LHC does not detect a reliable Higgs-mass signature during its life-time, do we demand lots more research money and build an accelerator that encompasses all of Australia, or do we re-group and modify theory? I hope for the latter. I fear the former.

No. If the LHC does not detect the Higgs, then the ILC will NOT be built until some one comes up with some compelling physics that there's something ELSE that we need to look at. The ILC, in case you didn't know, is in a holding pattern waiting for results from the LHC.

But there is ANOTHER issue here that you have ignored. The LHC isn't just a single-purpose machine. Do you think there is support, both from within the HEP community AND those funding agencies all over the world, to build a $8 billion machine, to just look for ONE particle? Honestly now, in your 56 years of existence, when was the last time you see physics funding getting away with doing THAT?

The Tevatron had tons of physics coming out of it, not just the value of the top quark mass. Even now, while it is hunting for the Higgs, there are other physics being done. Browse through PRL this past year and see how many non-Higgs related results that have been published.

When your phase space to find something is LARGE due to large uncertainties, not finding something within a certain region of the phase space is HIGHLY USEFUL. The Tevatron, in its failure to find the Higgs as of now, eliminated a large portion of the phase space. This isn't the moving-of-the-goal-post! No one has moved it out of the realm of where the Higgs is realistically expected to be, at least for the weak symmetry breaking. Furthermore, this is what we do when we learn more about what it is and gain new insight into the various parameters involved in the theory. This isn't unusual in physics. Look at our knowledge of high-Tc superconductors - I don't see you complain about the moving-of-the-goal-posts with that either, yet, I can tell you how radically we had to revise our understanding of it for over 20 years already!

Zz.

 

[ZapperZ]

Yes, I agree with what you say --- up to a point --but what about string theory?

What about it? Brian Greene has publicly said that if String Theory can't come up with testable predictions, it is not physics, but philosophy.

Furthermore, and this goes back to what I had said previously, just what percentage of theorists in the world actually actively work in String Theory? Do you think this is the majority, or do you think they are simply a "vocal" minority? How does what they do become an accurate representation of theorists as a whole?

No, I guess not. So I'll have to think of cautionary examples of where theory has proved to be untrustworthy, or perhaps too contentious to be trusted, in condensed matter physics. I can think of a few possible candidates --- but I don't want to enrage this community , too --- so please take these comments lightly. Here goes: would the time spent and heat generated in arguments (think P.W.Anderson) about the theory of high temperature superconductors fit? And would the extended but contentious and futile efforts to explain the simple and technically important phenomenon of strain hardening in metals (still quite unresolved) qualify as a cautionary example?

WHICH Phil Anderson's theory? I used to work in high Tc superconductor, and I had even chatted with Phil Anderson a few times at various conferences. He has a strong idea of the mechanism of high-Tc superconductors, and like everyone else, they will have to be tested. Besides, if you look at many of his work, he always starts with a series of experimental observations that are the basis for his theory (see his broken symmetry principle). And if you look at his "More Is Different" essay, you'll see that he starts off with stuff we observe from chemistry, i.e. NH3! Condensed matter physicists, as I've said, are slaves to the experiments! More often than not, they start their theory using various experimental observations as the foundation. Look at any condensed matter theorists that have won the Nobel prize, and you'll see that they got it by formulating the theory of an observed phenomenon.

Zz.

 

[Vanadium 50]

The detection of Higgs bosons was expected far below Tevatron energies for years and the energies were pushed higher and higher in response to non-detection.

I'm sorry, but this is just not true.

The Higgs must weigh less than about 1 TeV. Heavier than that, and the theory doesn't make sense. The Higgs should weigh in the neighborhood of 246 GeV give or take an order of magnitude. This has been known for decades. With recent precision measurements, the Higgs is predicted to be quite light: the best electroweak fits have the Higgs mass slightly below the experimental lower bound on its mass.

People did search for very light Higgs bosons in the past. They did so because they were looking for a surprise. Had the Higgs been discovered in, for example, upsilon decays, this would have been big news for two reasons: the discovery itself, and a mass far lighter than expected.

So it's simply not true that the goalposts were moved in response to non-discovery.

 

[Vanadium 50]

The fact that collisions in the disk tended to make orbits more circular explains why most planets in our solar system have nearly circular orbits."

I doubt that the authors pulled the last sentence out of thin air.

They didn't. You can see for yourself why this might be true. Consider a coalescing cloud. As you near the center, the density goes up, so the collision probability goes up. You can think of this as an increased drag on the object as it gets close to the center. This causes it to lose kinetic energy at the point where kinetic energy is largest, which circularizes the orbit.

 

[oldman]

...Consider a coalescing cloud. As you near the center, the density goes up, so the collision probability goes up. You can think of this as an increased drag on the object as it gets close to the center. This causes it to lose kinetic energy at the point where kinetic energy is largest, which circularizes the orbit.

I'm now a bit wiser. Thanks, Vanadium 50. Pretty much the same answer has been given in reply to this question when I resorted yesterday to the Astronomy forum, by D.H., namely "In a word, drag..." , with some further explanation. My faith in these forums is now quite restored!

 

[oldman]

What about it? Brian Greene has publicly said that if String Theory can't come up with testable predictions, it is not physics, but philosophy

Good for him.

...just what percentage of theorists in the world actually actively work in String Theory? Do you think this is the majority, or do you think they are simply a "vocal" minority? How does what they do become an accurate representation of theorists as a whole?

It doesn't. Nor are the speculations of cosmologists about the anthropic principle representative. But, I think, neither should such antics be brushed under a carpet of tolerance, and so dismissed.

...Condensed matter physicists, as I've said, are slaves to the experiments! More often than not, they start their theory using various experimental observations as the foundation. Look at any condensed matter theorists that have won the Nobel prize, and you'll see that they got it by formulating the theory of an observed phenomenon. Zz.

More often than not -- yes, that's so. But even such physicists (I was once one) have met their share of annoyingly over-enthusiastic theorists. The Nobel prize committee, I agree, are pretty hard-headed about awarding their prize. Just as well, I think!

 

[ZapperZ]

Good for him.

It doesn't. Nor are the speculations of cosmologists about the anthropic principle representative. But, I think, neither should such antics be brushed under a carpet of tolerance, and so dismissed.


More often than not -- yes, that's so. But even such physicists (I was once one) have met their share of annoyingly over-enthusiastic theorists. The Nobel prize committee, I agree, are pretty hard-headed about awarding their prize. Just as well, I think!

I'm not a fan of String theory, and other exotica that have lost sight of reality either. However, and this is highly unsual of me to defend them, they should be allowed to venture into such speculations. Unlike speculations made by amateurs and crackpots, these exercises are part of doing physics - to explore just how much we can extend our knowledge. That's what Dirac did when he extended QM by incorporating relativity. Those "negative energy" solutions could easily pass as one of your "antics". The same could be said with all those quarks that were part of the Standard Model, or even theories of the neutrinos mixing angles at the time when neutrinos were thought to be massless.

Zz.