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Any good Physics forums for laymen?
Posted: 03 October 2013 11:18 AM   [ Ignore ]
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Lots of smart folks right here, but I was wondering if there are any good Physics forums where informed laymen like myself can ask questions but not be dismissed because I’m not an actual physicist?

Short of that, does anybody here know why everything in fundamental physics seems to be particle based? For example, I’m watching a show on the Higgs-Boson particle. Evidently the LHC can create energies that will result in being able to observe the H-B.  But why do they think it’s a particle in the first place?  Or is “particle” just a handy term they use and not really an actual particle in the more common sense.

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Posted: 03 October 2013 11:53 AM   [ Ignore ]   [ # 1 ]
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This one seems to be decent, the Bad Astronomy forum:

http://cosmoquest.org/forum/forum.php

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Posted: 03 October 2013 12:05 PM   [ Ignore ]   [ # 2 ]
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The physics forum at http://www.scienceforums.net is good too.

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Posted: 03 October 2013 03:27 PM   [ Ignore ]   [ # 3 ]
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Thanks, these both look great.

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Posted: 03 October 2013 05:08 PM   [ Ignore ]   [ # 4 ]
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CuthbertJ - 03 October 2013 11:18 AM

Short of that, does anybody here know why everything in fundamental physics seems to be particle based? For example, I’m watching a show on the Higgs-Boson particle. Evidently the LHC can create energies that will result in being able to observe the H-B.  But why do they think it’s a particle in the first place?  Or is “particle” just a handy term they use and not really an actual particle in the more common sense.

Intriguing question. Apparently, quantum “particle” is a misnomer from classical physics.

http://en.wikipedia.org/wiki/Particle_physics

To be specific, the term particle is a misnomer from classical physics because the dynamics of particle physics are governed by quantum mechanics. As such, they exhibit wave-particle duality, displaying particle-like behavior under certain experimental conditions and wave-like behavior in others.

There are no defined particles per se (as there are in the macro realm) in the micro quantum realm.

Apparently, there are only fields (whatever they are).

http://arxiv.org/ftp/arxiv/papers/1204/1204.4616.pdf

Particles are epiphenomena arising from fields. Thus the Schroedinger field is a space-filling physical field whose value at any spatial point is the probability amplitude for an interaction to occur at that point. The field for an electron is the electron…

bold added by me.

So, is it fields and/or particles?

From the introduction of the above cited paper:

But fields-versus-particles is still alive and kicking, as you can see by noting that “quantum field theory” (QFT) and “particle physics” are interchangeable names for the same discipline!

Also:

Physicists are schizophrenic about fields and particles

And what are fields? Don’t ask. Fields are supposed to extend to infinity…. Ignorance is bliss.

cheese

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Posted: 03 October 2013 11:05 PM   [ Ignore ]   [ # 5 ]
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CuthbertJ - 03 October 2013 11:18 AM

Short of that, does anybody here know why everything in fundamental physics seems to be particle based? For example, I’m watching a show on the Higgs-Boson particle. Evidently the LHC can create energies that will result in being able to observe the H-B.  But why do they think it’s a particle in the first place?  Or is “particle” just a handy term they use and not really an actual particle in the more common sense.

It just seems so, because it is the easiest way of speaking. Matter of fact is that the Higgs field was needed to explain why particles have mass. As a consequence of the existence of the Higgs field, there also should exist a Higgs particle, i.e. an local interaction of the Higgs field with other fields. Because that is what a particle is: the interaction between quantum fields. Quantum fields develop deterministically in time when left on their own, but when they interact this interaction is local. This local interaction gives the ‘particle-impression’. Where and when exactly the interaction takes place is a statistical process, it cannot be predicted exactly. Measurements are interactions per definition, so we measure ‘particles’, even that they were no particles until they interacted.

Maybe they should have found a new word for quantum objects, to stop all confusions, something like ‘potactons’ (the ‘potential to act’)...

For the best lay explanation about the Higgs ‘particle’ I know until now, see MinutePhysics on Youtube.

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Posted: 04 October 2013 10:26 AM   [ Ignore ]   [ # 6 ]
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Quantum fields are not real unlike the electromagnetic (EM) field which is a physical field produced by electrically charged objects which can be detected, observed and measured.

What is a quantum field?

http://www.huffingtonpost.com/victor-stenger/particles-are-for-real_b_2177361.html

No one has ever observed a quantum field. Quantum fields are purely mathematical constructs within quantum field theory.

OTOH, quantum “particles” are real. They can be detected, observed and measured:

Every quantum field has associated with it a particle that is called the “quantum of the field.” The photon is the quantum of the electromagnetic field. The electron is the quantum of the Dirac field. The Higgs boson is the quantum of the Higgs field. In other words, like love and marriage, you can’t have one without the other. The building blocks of our theories are fields and particles

The rationale of describing particles instead of fields:

And, the workers at the LHC do not talk about colliding the quantum fields of two protons together to measure the wavelengths of some abstract wave oscillating in some imaginary aether. They speak of banging particles together and measuring the particles they see coming out.

The point is, while our mathematical theories are expressed in terms of abstract fields, what we always measure is best described as particles.

So, quantum fields are abstract mathematical constructs whereas quantum “particles” are real entities.

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Posted: 05 October 2013 06:37 AM   [ Ignore ]   [ # 7 ]
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This is becoming a ‘how many angels fit on the point of a needle’ discussion.

Is light a particle? No, because in the two slit experiment on photon passes both slits, which a particle can’t. Is it a field? No, because the photon is measured locally.

The Higgs field was introduced to explain the mass of particles. However when there is a quantum field, then its excitation, the Higgs particle, must also exist. As you know it was found. As a result of ‘just a mathematical abstraction’?

The quantum mathematical formalism is consistent in itself and with experiment. So there is no scientific problem. The problem arises when we try to understand what happens based on concepts of our everyday life. They just do not fit. And so we can discuss endlessly about which concepts fit best.

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Posted: 05 October 2013 09:37 AM   [ Ignore ]   [ # 8 ]
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What is a field in physics?

http://en.wikipedia.org/wiki/Field_(physics)

A field is a physical quantity that has a value for each point in space and time.

This is so for the classical electromagnetic (EM) or the Newtonian gravitational fields.

However:

....a field can be either a classical field or a quantum field, depending on whether it is characterized by numbers or quantum operators respectively.

The consequence of defining a field as “numbers in space”

Defining the field as “numbers in space” shouldn’t detract from the idea that it has physical reality. “It occupies space. It contains energy. Its presence eliminates a true vacuum.” The field creates a “condition in space” such that when we put a particle in it, the particle “feels” a force.

Bold added by me.

This is true for the classical EM or gravitational fields. However, wrt the quantum field, where is the “particle”? Is it that the field is the “particle” or is it the epiphenomenon arising from the field? Whatever it is, the quantum field has no physical reality, unlike classical fields. For instance, has anyone observed a quantum field?

From http://en.wikipedia.org/wiki/Quantum_field_theory

In theoretical physics, quantum field theory (QFT) is a theoretical framework for constructing quantum mechanical models of subatomic particles in particle physics and quasiparticles in condensed matter physics, by treating a particle as an excited state of an underlying physical field.

Bold added by me.

So, if “QFT is a theoretical framework for constructing quantum mechanicals models of subatomic particles” and as it is expressed in mathematical terms, it is a mathematical construct. A model is only “the map, but it is not the territory”.

OTOH, quantum “particles” exist and they can be observed i.e. they are real. That is the territory.

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Posted: 05 October 2013 03:57 PM   [ Ignore ]   [ # 9 ]
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CuthbertJ - 03 October 2013 11:18 AM

Lots of smart folks right here, but I was wondering if there are any good Physics forums where informed laymen like myself can ask questions but not be dismissed because I’m not an actual physicist?


Depends on what what kind of physics your asking and what your question is.

My physics professor actually warned me once to be very skeptical of physics websites and forums which try to help students get through undergrad physics.
Many of them are often wrong.

But of course, that isn’t to deny that there are some good physics on the web somewhere

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Posted: 07 October 2013 03:40 AM   [ Ignore ]   [ # 10 ]
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kkwan - 05 October 2013 09:37 AM

What is a field in physics?

http://en.wikipedia.org/wiki/Field_(physics)

In the late 1920s, the new rules of quantum mechanics were first applied to the electromagnetic fields. In 1927, Paul Dirac used quantum fields to successfully explain how the decay of an atom to lower quantum state lead to the spontaneous emission of a photon, the quantum of the electromagnetic field. This was soon followed by the realization (following the work of Pascual Jordan, Eugene Wigner, Werner Heisenberg, and Wolfgang Pauli) that all particles, including electrons and protons could be understood as the quanta of some quantum field, elevating fields to the most fundamental objects in nature.

Bold added by me.

kkwan - 05 October 2013 09:37 AM

From http://en.wikipedia.org/wiki/Quantum_field_theory

In theoretical physics, quantum field theory (QFT) is a theoretical framework for constructing quantum mechanical models of subatomic particles in particle physics and quasiparticles in condensed matter physics, by treating a particle as an excited state of an underlying physical field.

Italics added by me. Your bold phrases just say what is true for every theory in physics: that it is a model and theoretical framework.

How many angels?

Stop citing. Start thinking. When you know what you cite, you show you are thinking.

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Posted: 07 October 2013 08:14 AM   [ Ignore ]   [ # 11 ]
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GdB - 07 October 2013 03:40 AM

In the late 1920s, the new rules of quantum mechanics were first applied to the electromagnetic fields. In 1927, Paul Dirac used quantum fields to successfully explain how the decay of an atom to lower quantum state lead to the spontaneous emission of a photon, the quantum of the electromagnetic field. This was soon followed by the realization (following the work of Pascual Jordan, Eugene Wigner, Werner Heisenberg, and Wolfgang Pauli) that all particles, including electrons and protons could be understood as the quanta of some quantum field, elevating fields to the most fundamental objects in nature.

Specifically, if quantum fields are “the most fundamental objects in nature” has anybody observed, detected and measured these ubiquitous quantum fields as can be done for EM fields?

From the same wiki:

Quantum fields

It is now believed that quantum mechanics should underlie all physical phenomena, so that a classical field theory should, at least in principle, permit a recasting in quantum mechanical terms; success yields the corresponding quantum field theory.

Bold added by me.

Belief….at least in principle…seems like faith and religious dogma!  smile

kkwan - 05 October 2013 09:37 AM

From http://en.wikipedia.org/wiki/Quantum_field_theory

In theoretical physics, quantum field theory (QFT) is a theoretical framework for constructing quantum mechanical models of subatomic particles in particle physics and quasiparticles in condensed matter physics, by treating a particle as an excited state of an underlying physical field.

Italics added by me. Your bold phrases just say what is true for every theory in physics: that it is a model and theoretical framework.

A model and theoretical framework is precisely that: it is a map and not the territory.

Maps can be useful, but we must not conflate the map with the territory.

What is that “underlying physical field” i.e. the quantum field? Can we observe, detect and measure it as we can, with an EM field? If not, is it real, is it just a mathematical construct or what (whatever it is).

How many angels?

Not how many angels, more like how many epicycles.

Stop citing. Start thinking. When you know what you cite, you show you are thinking.

Stop prejudicing, start thinking critically and remove the shackles of received wisdom.

LOL

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Posted: 08 October 2013 03:11 PM   [ Ignore ]   [ # 12 ]
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GdB - 05 October 2013 06:37 AM

This is becoming a ‘how many angels fit on the point of a needle’ discussion.

Is light a particle? No, because in the two slit experiment on photon passes both slits, which a particle can’t. Is it a field? No, because the photon is measured locally.

The Higgs field was introduced to explain the mass of particles. However when there is a quantum field, then its excitation, the Higgs particle, must also exist. As you know it was found. As a result of ‘just a mathematical abstraction’?

The quantum mathematical formalism is consistent in itself and with experiment. So there is no scientific problem. The problem arises when we try to understand what happens based on concepts of our everyday life. They just do not fit. And so we can discuss endlessly about which concepts fit best.

All arguments fall into how many angels can fit on the point of a needle, sooner or later. There is no avoiding it except by removing oneself from the discussion when it seems to be leaning in that direction. Once that happens there is no saving it in most cases.


Lois

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Posted: 11 October 2013 02:25 PM   [ Ignore ]   [ # 13 ]
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Why is wikipedia being quoted so much?

Wikipedia itself says:

Wikis, including Wikipedia and other wikis sponsored by the Wikimedia Foundation, are not regarded as reliable sources.
http://en.wikipedia.org/wiki/Wikipedia:Reliable_source_examples

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Posted: 11 October 2013 07:09 PM   [ Ignore ]   [ # 14 ]
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I.J. Abdul Hakeem - 11 October 2013 02:25 PM

Why is wikipedia being quoted so much?

Wikipedia itself says:

Wikis, including Wikipedia and other wikis sponsored by the Wikimedia Foundation, are not regarded as reliable sources.
http://en.wikipedia.org/wiki/Wikipedia:Reliable_source_examples

Intriguing question. Fundamentally, what is a source?

http://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sources

Definition of a source

The word “source” when citing sources on Wikipedia has three related meanings:

        * the piece of work itself (the article, book);
        * the creator of the work (the writer, journalist),
        * and the publisher of the work (for example, Random House or Cambridge University Press).

Any of the three can affect reliability. Reliable sources may be published materials with a reliable publication process, authors who are regarded as authoritative in relation to the subject, or both. These qualifications should be demonstrable to other people.

As such, wikipedia and wikis are not reliable sources per se.

However, from the same wiki:

Many Wikipedia articles rely on scholarly material. When available, academic and peer-reviewed publications, scholarly monographs, and textbooks are usually the most reliable sources. However, some scholarly material may be outdated, in competition with alternative theories, or controversial within the relevant field. Try to cite present scholarly consensus when available, recognizing that this is often absent. Reliable non-academic sources may also be used in articles about scholarly issues, particularly material from high-quality mainstream publications. Deciding which sources are appropriate depends on context. Material should be attributed in-text where sources disagree.

Bold added by me.

There are lists of sources below the end of most wiki articles which are referred to by [numbers] in the wiki article, as sources.

Wrt wikis on the natural sciences:

http://en.wikipedia.org/wiki/Wikipedia:Identifying_reliable_sources_(natural_sciences)

Wikipedia’s science articles are not intended to provide formal instruction, but they are nonetheless an important and widely-used resource. Scientific information should be based on reliable published sources and should accurately reflect the current state of knowledge. Ideal sources for these articles include comprehensive reviews in independent, reliable published sources, such as reputable scientific journals, statements and reports from reputable expert bodies, widely recognized standard textbooks written by experts in a field, or standard handbooks and reference guides, and high-quality non-specialist publications. Although news reports are sometimes inappropriate as reliable sources for the technical aspects of scientific results or theories, they may be useful when discussing the non-technical context or impact of science topics, particularly controversial ones.

The scope of this page is limited to the natural sciences, including astronomy, biology, chemistry, geoscience, physics, and interdiscliplinary fields.

Bold added by me.

What is a resource?

http://www.merriam-webster.com/dictionary/resource

e :  a source of information or expertise

Of course, there are other resources online but wikipedia has established itself as an accessible open and free resource (which is subject to constant discriminate revisions and updates). This is the strength of wikipedia, notwithstanding criticisms of it’s perceived weakness in being open.

Wikipedia depend on the the “wisdom of the crowd” for the reliability and accuracy of it’s articles.

http://en.wikipedia.org/wiki/Wisdom_of_the_crowd

The wisdom of the crowd is the process of taking into account the collective opinion of a group of individuals rather than a single expert to answer a question. A large group’s aggregated answers to questions involving quantity estimation, general world knowledge, and spatial reasoning has generally been found to be as good as, and often better than, the answer given by any of the individuals within the group. An intuitive and often-cited explanation for this phenomenon is that there is idiosyncratic noise associated with each individual judgment, and taking the average over a large number of responses will go some way toward canceling the effect of this noise.[1] This process, while not new to the information age, has been pushed into the mainstream spotlight by social information sites such as Wikipedia and Yahoo! Answers, and other web resources that rely on human opinion.[2]

In other words, there exist a “system of checks and balances” (negative and positive feedbacks) for these open systems which is the source of their strength and robustness, analogous to nature.

Also, there is the issue of copyleft instead of copyright wrt wikis.

http://en.wikipedia.org/wiki/Copyleft

In other words, copyleft is a general method for marking a creative work as freely available to be modified, and requiring all modified and extended versions of the program to be free as well.[1]

This is the rationale behind why wikipedia is so often quoted.

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Posted: 12 October 2013 10:51 AM   [ Ignore ]   [ # 15 ]
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Understandable.
But one must still go to the sources Wikipedia uses and then use them as sources.

Wikipedia itself is questionable

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