The Postulation of New Particles and the Pessimistic Meta-Induction
from Josef Honerkamp, 01. October 2011, 18:41
By the end of this year we will know whether Higgs bosons exist, as the director of CERN claimed in the Süddeutsche Zeitung on 28/07/2011. Since my youth, when I graduated in the field of particle physics, I have been aware of the hypothesis that such a particle should exist. It was at the time when the importance of so-called gauge theories was realized. These play a crucial role in the famous standard model of the quantum field theory of electromagnetic and weak interactions. The only catch was that in such theories the particles associated with the quantum fields cannot possess a mass, which they should however have for physical reasons.
Those who are not well acquainted with the history of physics and who swear by the wording of Popper's principle that a single false prediction of a theory would already imply its failure, would immediately conclude that we should therefore dispense with gauge theories. But never in the history of physics has a theory been so quickly discarded; further circumstances could always exist by which seemingly contradictory goals could be achieved.
One such possibility would be that a particle exists and thus a corresponding quantum field by which, when introduced appropriately into the equations for the standard model, the quanta of gauge theories could be assigned a mass without abandoning the essential features of gauge theories. The British physicist Peter Higgs was the first to postulate such a particle, leading it to be christened the Higgs boson. From theoretical considerations we also know that the mass of this Higgs boson has to lie within a certain region and that, now at CERN with the LHC accelerator and its available energies, it should be possible to detect such a particle if it does indeed exist.
The Higgs boson is not the only hypothetical particle. It is believed that the universe contains a considerable amount of so-called dark matter, which would explain the high orbital velocity of the stars in the rotation of galaxies in their marginal areas. Finally there is the hypothesis that the universe is mostly filled with so-called dark energy, but no one has been able to give any idea about the form of this energy.
A list of previous hypotheses
Postulating the existence of a new particle in order to explain an observed phenomenon does not seem to be a sign of great creativity. However, this has happened many times throughout the history of physics, and not without success. Of course, the "ether" and the "caloric" in this context are often mentioned first because these hypotheses were not successful. However, the best known, which was adopted from natural philosophy and pursued over many centuries, was the hypothesis of the existence of atoms. However, there were many other hypotheses: In the 19th century, when the electrical effects were more examined closely, certain fluids, somehow made up of particles, were identified as being responsible for the phenomenon of charging and discharging. In 1905, Albert Einstein proposed the hypothesis that light consists of a flow of so-called light quanta. He cautiously called them "packets of energy that can be absorbed and emitted only as a whole"; today they are called photons. In 1930 Wolfgang Pauli postulated an electrically neutral particle, later called the neutrino, which preserved the energy conservation law in the so-called beta decay of atomic nuclei, and I can still remember the time when the idea emerged that the then so-called elementary particles turned out to be constructed from some identifiable components, called quarks. Thus, the present hypotheses of the Higgs boson and dark matter fit well into this list of hypotheses of new forms of matter, which is by no means complete, and it is instructive to take a closer look at the fate of these earlier hypotheses.
A rough inspection of the list already shows that there are success stories, but obviously also failures, and if a closer look is taken at the fate of the hypotheses, a certain development can be recognized for each. This begins with a pure assertion that the existence of this particle or substance is needed for a specific explanation of a phenomenon. Then, other phenomena may become plausible by its existence. In further stages, some properties of the substance or the particle are postulated due to experimental findings – and if all goes well, they all contribute to forming a coherent picture. Finally, one can speak of an experimental confirmation if one has measured signals in a detector which may be considered proof of existence of the particle by all the rules of experimental techniques and theoretical calculations.
A brief history of the hypotheses
In the case of the idea of a substance "caloric", which was postulated in order to explain the heat in a body, the first stage has never been gotten past. Although some phenomena could be explained by this hypothetical substance for a while, substantial properties for it have never been derived.
For the "ether" various models were derived up to the 19th century, but all had some difficulties. Furthermore, the various proposed properties of the ether contradicted each other to some extent, and in particular in the discussion of phenomena which should be observed during a movement against the ether, no clarification could be achieved. When Albert Einstein developed a unified theory of motion for fields as well as particles without the concept of ether but only on the basis of two simple principles, it was something akin to a liberation.
Also with the perception of a certain fluid for the explanation of the electrical current, there have been great difficulties, but this story proceeded quite differently: The idea arose in the days of Benjamin Franklin, when electrostatic phenomena such as the spark discharge were studied. The hypothetical fluid had to consist of particles which repel each other but are attracted to other sorts of matter. By friction of two materials such particles can be deposited or stripped. A resulting excess means a positive charge, a lack of such a substance a negative charge, and an attraction or a repulsion, respectively, of the materials was the consequence. There was also a competing theory with two kinds of fluids, which were slightly different and called "vitreous electricity" and "resinous electricity". Some effects could be better explained by the one-fluid theory, some by the two-fluid theory. By the end of the 19th century, when Maxwell's theory for electromagnetic phenomena was already generally accepted, how the electrical current in a wire arises was still not really understood. Only in 1897, when Joseph John Thomson through his experiments with the so-called cathode rays discovered that they consist of a beam of objects that not only carry an electrical charge but must also be a part of some, not-yet-known fundamental constituents of matter, was the puzzle solved. The electrical current turned out to be a current of objects called electrons. Today very refined experiments can be performed with electrons and their properties can be measured very accurately.
Also with the idea of atoms something real could finally be connected. They were already considered as basic building blocks of matter in early India, and also by Democritus and Epicurus in ancient Greece. With the beginnings of scientific chemistry more and more regularities in chemical reactions were discovered, which could be explained by the assumption that there are different "elements", i.e. types of atoms, which can combine in various ways. Albert Einstein was able to pull quantitative conclusions from Brownian motion experiments, such as useful statements about the size and number of atoms in a given volume. But it was still not clear whether atoms really exist, or whether there is something else behind all the rules and calculations, which corresponds well with the existence of atoms.
Much has been written about how the structure of the atom was gradually revealed, i.e. about Rutherford's experiments, the development of Bohr’s atom model and finally about the formation of quantum mechanics. Today, with scanning tunneling microscope one can create images of atoms on the surface of materials of all types and move and manipulate atoms on surfaces.
Today, also individual light quanta, so-called photons, can be manipulated. The development of this concept has something of a complex history. For Newton, light particles were still small corpuscles; for Young, Fresnel and Maxwell in the 19th century they were not light particles at all – light was interpreted as waves, distortions in the ether. After Einstein, light again consists of particles, but now with a whole new meaning, called quanta.
Meanwhile, the existence of many other quanta, which are still loosely called "particles", has been discovered in laboratories and accelerators, and with the concept of the aforementioned quarks some order and structure can be brought to this "zoo" of high-energy physicists. The last word on the existence of quarks has still not been uttered; there is evidence in many experiments, but individual quarks have not yet been detected. Thus, the development of this idea is in mid-stage, and gradually we come in our list to the area in which there is still uncertainty about the existence of the postulated particles.
Not being but the being-as-it-is is the problem
In the literature on a particular epistemological position, the so-called structural realism [1], the so-called pessimistic meta-induction is often mentioned [2]. This refers to the fact that apparently explanatory success can also be attained with particles that do not exist, as has indeed been experienced with the "caloric" and the "ether", and this can be taken as motivation for the conclusion that we might be in the same situation with all the particles established so far – namely, that future insights could show that these particles do not actually exist.
However, given the situation that we can manipulate atoms, photons, and electrons in our experiments in such a reliable and detailed manner, such considerations seem for me to be absurd. Though possible for logical reasons it deserves no more than an occasional mention as a bizarre position. It is not surprising that with the postulation of a new particle a blank is sometimes drawn.
The question is not so much whether an object exists in reality but how it exits. That there is "something" in our experiments which we manipulate cannot be denied, because we can directly influence this "something" and the same consistent and reliable network of properties and regularities shows up during every manipulation. But what idea should we connect with this "something" – this is the question. Thus, is not so much about "being", but more about the "essence" of a being, the being-as-it-is.
In many ontological discussions people still often have in mind the classical idea of matter and they think that this concept will capture the entire inventory of the universe. Our theories about atoms and even smaller systems have led us, however, to entirely new concepts. They are not comparable with anything that we know from the living environment which during biological evolution has shaped our ability of imagination. But we can deal consistently with the symbols for these new concepts in the context of our theories and explain and predict successfully and reliably natural phenomena with such mathematical ideas. But with what sort of "understanding" should we be satisfied for that to which these symbols refer? What can we expect there at all?
Let me return to the search for the Higgs boson. Some people would be glad if the conclusion had to be that it does not exist. Then the question is re-opened as to how a theory should look in which the quanta of gauge theories can have those masses, which have been measured experimentally. In particular, the question of what it means for an object to have a mass becomes an even hotter topic. The question of the nature of a quantum will remain an exciting one in any case.
Printview
Those who are not well acquainted with the history of physics and who swear by the wording of Popper's principle that a single false prediction of a theory would already imply its failure, would immediately conclude that we should therefore dispense with gauge theories. But never in the history of physics has a theory been so quickly discarded; further circumstances could always exist by which seemingly contradictory goals could be achieved.
One such possibility would be that a particle exists and thus a corresponding quantum field by which, when introduced appropriately into the equations for the standard model, the quanta of gauge theories could be assigned a mass without abandoning the essential features of gauge theories. The British physicist Peter Higgs was the first to postulate such a particle, leading it to be christened the Higgs boson. From theoretical considerations we also know that the mass of this Higgs boson has to lie within a certain region and that, now at CERN with the LHC accelerator and its available energies, it should be possible to detect such a particle if it does indeed exist.
The Higgs boson is not the only hypothetical particle. It is believed that the universe contains a considerable amount of so-called dark matter, which would explain the high orbital velocity of the stars in the rotation of galaxies in their marginal areas. Finally there is the hypothesis that the universe is mostly filled with so-called dark energy, but no one has been able to give any idea about the form of this energy.
A list of previous hypotheses
Postulating the existence of a new particle in order to explain an observed phenomenon does not seem to be a sign of great creativity. However, this has happened many times throughout the history of physics, and not without success. Of course, the "ether" and the "caloric" in this context are often mentioned first because these hypotheses were not successful. However, the best known, which was adopted from natural philosophy and pursued over many centuries, was the hypothesis of the existence of atoms. However, there were many other hypotheses: In the 19th century, when the electrical effects were more examined closely, certain fluids, somehow made up of particles, were identified as being responsible for the phenomenon of charging and discharging. In 1905, Albert Einstein proposed the hypothesis that light consists of a flow of so-called light quanta. He cautiously called them "packets of energy that can be absorbed and emitted only as a whole"; today they are called photons. In 1930 Wolfgang Pauli postulated an electrically neutral particle, later called the neutrino, which preserved the energy conservation law in the so-called beta decay of atomic nuclei, and I can still remember the time when the idea emerged that the then so-called elementary particles turned out to be constructed from some identifiable components, called quarks. Thus, the present hypotheses of the Higgs boson and dark matter fit well into this list of hypotheses of new forms of matter, which is by no means complete, and it is instructive to take a closer look at the fate of these earlier hypotheses.
A rough inspection of the list already shows that there are success stories, but obviously also failures, and if a closer look is taken at the fate of the hypotheses, a certain development can be recognized for each. This begins with a pure assertion that the existence of this particle or substance is needed for a specific explanation of a phenomenon. Then, other phenomena may become plausible by its existence. In further stages, some properties of the substance or the particle are postulated due to experimental findings – and if all goes well, they all contribute to forming a coherent picture. Finally, one can speak of an experimental confirmation if one has measured signals in a detector which may be considered proof of existence of the particle by all the rules of experimental techniques and theoretical calculations.
A brief history of the hypotheses
In the case of the idea of a substance "caloric", which was postulated in order to explain the heat in a body, the first stage has never been gotten past. Although some phenomena could be explained by this hypothetical substance for a while, substantial properties for it have never been derived.
For the "ether" various models were derived up to the 19th century, but all had some difficulties. Furthermore, the various proposed properties of the ether contradicted each other to some extent, and in particular in the discussion of phenomena which should be observed during a movement against the ether, no clarification could be achieved. When Albert Einstein developed a unified theory of motion for fields as well as particles without the concept of ether but only on the basis of two simple principles, it was something akin to a liberation.
Also with the perception of a certain fluid for the explanation of the electrical current, there have been great difficulties, but this story proceeded quite differently: The idea arose in the days of Benjamin Franklin, when electrostatic phenomena such as the spark discharge were studied. The hypothetical fluid had to consist of particles which repel each other but are attracted to other sorts of matter. By friction of two materials such particles can be deposited or stripped. A resulting excess means a positive charge, a lack of such a substance a negative charge, and an attraction or a repulsion, respectively, of the materials was the consequence. There was also a competing theory with two kinds of fluids, which were slightly different and called "vitreous electricity" and "resinous electricity". Some effects could be better explained by the one-fluid theory, some by the two-fluid theory. By the end of the 19th century, when Maxwell's theory for electromagnetic phenomena was already generally accepted, how the electrical current in a wire arises was still not really understood. Only in 1897, when Joseph John Thomson through his experiments with the so-called cathode rays discovered that they consist of a beam of objects that not only carry an electrical charge but must also be a part of some, not-yet-known fundamental constituents of matter, was the puzzle solved. The electrical current turned out to be a current of objects called electrons. Today very refined experiments can be performed with electrons and their properties can be measured very accurately.
Also with the idea of atoms something real could finally be connected. They were already considered as basic building blocks of matter in early India, and also by Democritus and Epicurus in ancient Greece. With the beginnings of scientific chemistry more and more regularities in chemical reactions were discovered, which could be explained by the assumption that there are different "elements", i.e. types of atoms, which can combine in various ways. Albert Einstein was able to pull quantitative conclusions from Brownian motion experiments, such as useful statements about the size and number of atoms in a given volume. But it was still not clear whether atoms really exist, or whether there is something else behind all the rules and calculations, which corresponds well with the existence of atoms.
Much has been written about how the structure of the atom was gradually revealed, i.e. about Rutherford's experiments, the development of Bohr’s atom model and finally about the formation of quantum mechanics. Today, with scanning tunneling microscope one can create images of atoms on the surface of materials of all types and move and manipulate atoms on surfaces.
Today, also individual light quanta, so-called photons, can be manipulated. The development of this concept has something of a complex history. For Newton, light particles were still small corpuscles; for Young, Fresnel and Maxwell in the 19th century they were not light particles at all – light was interpreted as waves, distortions in the ether. After Einstein, light again consists of particles, but now with a whole new meaning, called quanta.
Meanwhile, the existence of many other quanta, which are still loosely called "particles", has been discovered in laboratories and accelerators, and with the concept of the aforementioned quarks some order and structure can be brought to this "zoo" of high-energy physicists. The last word on the existence of quarks has still not been uttered; there is evidence in many experiments, but individual quarks have not yet been detected. Thus, the development of this idea is in mid-stage, and gradually we come in our list to the area in which there is still uncertainty about the existence of the postulated particles.
Not being but the being-as-it-is is the problem
In the literature on a particular epistemological position, the so-called structural realism [1], the so-called pessimistic meta-induction is often mentioned [2]. This refers to the fact that apparently explanatory success can also be attained with particles that do not exist, as has indeed been experienced with the "caloric" and the "ether", and this can be taken as motivation for the conclusion that we might be in the same situation with all the particles established so far – namely, that future insights could show that these particles do not actually exist.
However, given the situation that we can manipulate atoms, photons, and electrons in our experiments in such a reliable and detailed manner, such considerations seem for me to be absurd. Though possible for logical reasons it deserves no more than an occasional mention as a bizarre position. It is not surprising that with the postulation of a new particle a blank is sometimes drawn.
The question is not so much whether an object exists in reality but how it exits. That there is "something" in our experiments which we manipulate cannot be denied, because we can directly influence this "something" and the same consistent and reliable network of properties and regularities shows up during every manipulation. But what idea should we connect with this "something" – this is the question. Thus, is not so much about "being", but more about the "essence" of a being, the being-as-it-is.
In many ontological discussions people still often have in mind the classical idea of matter and they think that this concept will capture the entire inventory of the universe. Our theories about atoms and even smaller systems have led us, however, to entirely new concepts. They are not comparable with anything that we know from the living environment which during biological evolution has shaped our ability of imagination. But we can deal consistently with the symbols for these new concepts in the context of our theories and explain and predict successfully and reliably natural phenomena with such mathematical ideas. But with what sort of "understanding" should we be satisfied for that to which these symbols refer? What can we expect there at all?
Let me return to the search for the Higgs boson. Some people would be glad if the conclusion had to be that it does not exist. Then the question is re-opened as to how a theory should look in which the quanta of gauge theories can have those masses, which have been measured experimentally. In particular, the question of what it means for an object to have a mass becomes an even hotter topic. The question of the nature of a quantum will remain an exciting one in any case.
Printview
...for the insightful post! I gladly tweeted it, hoping that it may find many readers.
"Today, also individual light quanta, so-called photons, can be manipulated."
How? If there is any interaction between observer and observed photon whatsoever it disappears completely.
This is the nature of what we call "time".
You cannot observe the same photon (a single quantum) twice.
I have had in mind the Mach-Zehnder interferometer (see Wikipedia and further hints there). Do you think that this is not a "manipulation" of a single photon?
Complete destructive interference in a Mach-Zehnder interferometer is indeed looking like a miracle.
There is no real proof of photons on the second detector possible. Unless we accept a physical thermodynamically meaning to the concept of a "photon".
Photons measured are physically "in existance" when measured, but photons not measured are unreal and will stay unreal.
I had a recent conversation on scienceblogs "Starts with a Bang" from Ethan Siegel:
http://scienceblogs.com/...he_wmap_image_means.php
and http://www.nwtonline.nl/...45/undefined/index.html
it's old but about destructive interference.
But photons are usefull in the Second Law and the nature of "Time" in my view.
Great article, btw. But covering a lot of issues all at once.
The problem is difficult in my opinion.
If there is a path-choice problem (QM) then why are all the photons making the same choice at the last mirror?
In a classical way a phase-change-only solution is also problematic. In case of a dielectric reflection of light there should be (regardless if 50% or 100% reflection) always a phase shift of pi.
See also my remarks at:
http://www.science20.com/...tal_nature_light-75861
- I do not see any problems by explaining the outcomes of the Mach-Zehnder experiment in quantum mechanics. What is a "thermodynamically meaning" of a photon?
- On the other hand, I agree to your statement: "Photons measured are physically "in existence" when measured, but photons not measured are unreal and will stay unreal." Existence and reality are different concepts, quantums are not real unless e.g. they are measured, but they always exist. Our notion of reality is a classical one, and this property of matter is only an emergent quantity in many-body-systems. For photons such many-body-systems are classical light waves, they obviously exist and(!) are real.
The problem is that QM can't explain the last choice at the last mirror. Why would the photons choose for a particular direction? The half-silvered mirrors are the same. Only there is a quarter pi phase shift difference.
The term "destructive" interference is misleading. Nothing thermodynamically has changed. All the energy goes to a single detector. If there would be any REAL interference the energy content measured would be at 50% of the input. It would invalidate Newton's Second Law of energy conservation.
One would really have discovered "Dark Energy".
A very useful post.I tweeted it too.