juanrga

The force is |F| = G (m1*m2)/d2 Apart from giving the correct units for the force, the constant G is also a measure of the strength of the gravitational interaction (G appears in other equations of physics). In a hypothetical universe where G takes twice its value here, the gravitational force would be more important than in our universe.

In order: 1) Yes. I already emphasized how "classical particle" is a limiting case of a "quantum particle", which can be derived by taking the classical limit of the quantum theory. 2) Yes, if you mean that a collection of quantum particles can have (collectively) wave properties. I already emphasized how an electromagnetic wave is a collection of photons and how the interference pattern in a double slit-experiment with electrons is generated by thousands of electrons as the experiment shows: However, if you mean that an individual quantum particle has wave properties or is a wave (some posters here said that an electron is sometimes a wave). No. 3) Yes.

Yes are similar although quantum chromodynamics is more complex. In quantum electrodynamics you study electrons and photons and in quantum chromodynamics you study other particles as quarks and gluons. Surely you heard about quarks before.

When you a pass a quantum object in an interference experiment, how can you say that it has passed through one slit or the other and as behaved as a particle when we have not measured or observed it? Science doesn't give an objective account of reality. That quote is saying you that "particle", in quantum mechanics, does not mean "little-hard-sphere-following-Newtonian-laws" but you insist on your misconception. In that discussion the word was unneeded. Also that part is a standard discussion of ordinary quantum mechanics, contrary to your beliefs. You are who evade the questions. Those six links explain to you, in layman terms, how everything around us is made of particles. You continue rejecting this well-known fact and posting stuff as "Science doesn't give an objective account of reality." In the first place, the term "Copenhagen rules" does not appear in any part of the link that you are giving, but you added the term before the list, which you copied from the link and has a different meaning. When Weinberg writes about the Copenhagen rules in Physics Today, he is referring to "the probabilistic rules of the Copenhagen interpretation", Weinberg is not referring to a set of ambiguous philosophical points by Bohr. Also as Weinberg writes in Physics Today: "Bohr's version of quantum mechanics was deeply flawed". But this is another point that you refuse to accept. The Copenhagen Interpretation of quantum mechanics is not a postulate but one of several interpretations of quantum mechanics. http://en.wikipedia....antum_mechanics The Copenhagen Interpretation has been superseded by more modern interpretations which work in situations beyond the scope of the old Copenhagen Interpretation. Recall also Weinberg writing in Physics Today:

You did not asked one thing but two. And I offered a detailed answer before, but the short version is "yes" and "yes". I did not restrict you with a simple yes/no. Yes, it is rather standard. You can google "quantum particle". I added the disclaimer (which was also added by another poster), because some people confounds "particle" with "classical particle". The OP asked me "But is electron present as a standing wave or as a particle in the atom?" My response was that the electron in an atom is a particle. Another poster wrote that the electron in an atom is a particle. Both answers are correct. I also give a link to IUPAC, where they define the electron as a particle. Of course, the chemists definition also applies to quantum chemistry. I also explained to the OP how a collection of particles can show wave-like behaviour. I remarked this about 100 posts ago. The usual interference pattern observed in double-slit experiment with electrons is generated by thousands of particles (electrons). Electromagnetic waves are a collection of particles named photons... Some people here misinterprets any bit of modern physics and has posted wrong claims: one poster said that nobody really believes that the electron is a particle (wrong), other said that the wavefunction is real and physical (wrong), other said that an electron is sometimes a wave (wrong)...

I will try to explain this again. Lecher lines are macroscopic conductors and are described by electromagnetic wave theory. Electromagnetic wave theory can be derived as approximation to a quantum theory of particles (photons and electrons). The derivation of classical electrodynamics from the underlying quantum theory is made in textbooks. Those waves that you can observe are the result of collective phenomena involving a large amount of elementary particles.

I completely agree with you. As said, the editor was deliciously polite and sincere and I liked that.

And all them would be right then when available data supported them. At the time of writing this, elementary particles are indivisible and fundamental. No known experiment contradicts this. Maybe tomorrow new observations/experiments will suggest otherwise, but not today.

I think that there are not popular textbooks regarding chemistry. Maybe Chemistry for Everyone: A Helpful Primer for High School or College Chemistry by Suzanne Lahl and Cris Qualiana is what you are searching but I do not know for sure. Regarding physics, try Feynman's popular book Six Easy Pieces: Essentials of Physics. If you want to obtain a picture of some modern advances in physics and chemistry not covered in any of the above titles. I recommend you The End of Certainty by Ilya Prigogine.

We still regard elementary particles as "indivisible" because all experiments made up to now confirm that elementary particles are not composite. Predictions made by some speculative models (as some models of preons) were experimentally ruled out.

Quantum mechanics is the part of quantum physics devoted to the mechanics. Quantum field theory is the part of quantum theory devoted to fields. Quantum electrodynamics and quantum chromodynamics are subareas of quantum field theory. E.g. quantum electrodynamics studies electromagnetic and fermion fields.

It means that particle and the antiparticle are indistinguishable. E.g. an electron has negative charge, but an antielectron has positive charge and you can differentiate both. As ajb pointed, the photon is the typical example of particle which is indistinguishable from its antiparticle. The photon has zero charge and the anti-photon has zero charge (0 = -0). As a consequence, photon and antiphoton are not distinguishable.

Agree with this, but what has it to do with the original quote to which ajb replied?

What do you mean?

And, contrary to your claims, that quote from Physics Today states that Bohr's version of quantum mechanics was deeply flawed and states that The Copenhagen interpretation is wrong. Now you confound "The Copenhagen interpretation" with "the probabilistic rules of the Copenhagen interpretation". You are confound the Copenhagen rules and the Copenhagen interpretation. What will be the next? Repeating doesn't answer the question, because that wasn't the question that was asked. Do quantum particles ever exhibit what one would classically call wave-like behavior? Do they ever exhibit classical particle behavior? Repeating questions that were answered before, will not change the response. I have a new question for you. Do you believe that a "quantum particle" (your own words) is a particle? Or do you believe that this is a radical claim?

That is not true. As I said to you several times, the EM wave theory used to describe lecher lines is an approximation derived from the underlying quantum theory of particles (photons). Your ideas about that universe is not made of particles confronts with overwhelm standard consensus among scientists. I repeat everything in the universe is made of particles: http://www.particlephysics.ac.uk/explore/atoms-and-particles.html http://public.web.cern.ch/public/en/science/StandardModel-en.html http://www.fnal.gov/pub/inquiring/matter/madeof/index.html http://www.particleadventure.org/quarks_leptons.html http://physics.about.com/od/atomsparticles/a/particles.htm http://www.pbs.org/wgbh/nova/teachers/activities/3012_elegant_09.html ... Steven Weinberg remarks are not "subjective opinions" but scientific remarks that reflect our more modern and advanced understanding of quantum theory. I already stated why all your arguments are invalid. I have explained in this thread what is an elementary particle, what are its properties, how we experimentally describe them, why particles are never waves, under what limits we can associate a wavefunction to the state of a particle and when we cannot, I have emphasized that in advanced and modern textbooks duality is not even mentioned because it plays no role in QM (I have cited some of those advanced textbooks)... You have not addressed any of that. You and everyone else who has studied a bit of quantum mechanics.

You are who introduced here Bohr and the Copenhagen Interpretation as justification for your ideas, without being aware that (as SW remarks) "Bohr's version of quantum mechanics was deeply flawed" and that the Copenhagen interpretation "is surely wrong". I repeat again, in advanced and modern treatments of quantum physics we do not use wave-particle duality, because it plays absolutely no role in a fundamental description of our physical world. Quotes from introductory and outdated textbooks do not count as valid argument against advanced and modern sources. Your quotation from "A beginner's guide to quantum physics" is not an argument about what Steven Weinberg (a Nobel Prize for Physics who is currently considered one of the most important living physicists) wrote in Physics Today. Your appeals to Dirac and Bohr ancient quotes will not change the definitions and statements made by CERN and IUPAC (two leading academic bodies).

When you asked me to explain lecher lines in terms of particles.

Before, you quoted Dirac on a topic where he was shown to be plain wrong. Now you cite Bohr in another topic where he was wrong. As Steven Weinberg remarks in Physics Today, November 2005, page 31: Our understanding of the world has advanced a lot of since Bohr. In last 100 years, we have developed advanced formulations which are very far from the original work by Bohr. We know today that particles always behave as particles with independence of the existence or absence of an observer. Incorrect, the wavefunction is symbolic and it doesn't represent anything physical. I what wrote is standard quantum physics, whereas what you write is unrelated. This is wrong, you're claiming too much. QM doesn't allow that, if the property of position and momentum cannot be attributed to a particle before a measurement is being made then even to think of it as a particle is meaningless. Got it? Our modern picture of the physical world as made of particles is based in QM. This is the standard vision of the physical world and you are who do not still get it (http://public.web.ce...rdModel-en.html):

This question is similar to a previous question by studiot. The answer is the same: using the standard quantum mechanics of particles. Your own link starts with the next definition of quantum tunnelling (bold face from mine) and in the technical discussion of tunnelling uses (bold face from mine): The rest of the discussion on that page is rather incorrect. For instance who wrote that page interpreted time-independent wave functions as "travelling waves". Did you read the several quotes and links given before?

A particle does not act as a wave. So bizarre as you must find this idea, a particle acts as a particle. The quote from Dirac continues being ironic, because he was wrong precisely regarding wavefunctions, with his wave formulation being an inconsistent formulation. The quote from Serway et al is misleading. The first part of the quote simply remarks that classical physics does not work at the atomic level. This is correct but was emphasized here before. Next Serway et al agree on that an electron is a particle and then write: "Such a particle exhibits wave properties when it interacts with a metal crystal and particle properties a short while later when it registers on a Geiger counter." This phrase is illogical because, by definition, a particle always exhibit particle properties! Their phrase would be more acceptable and rigorous if they did the substitutions "wave properties" --> "classical wave properties" and "particle properties" --> "classical particle properties"; although it would be still open to some fundamental objections. Moreover, if you check their chapter 15, concretely their table 15.2 you would find that the first entry under the row "Particle name" is "electron". Effectively, as any other physicists or chemist, Serway et al define the electron as a particle as well. And so bizarre or crackpot as this idea can seem to some here, a particle acts and behaves as a particle. There is no real and physical wave in a double slit interference pattern. Only a distribution of particles (plural) that resembles formally the interference pattern of a classical optical wave, but that has a completely different physical interpretation. One time more, (i) the wavefunction is a mathematical function not a real wave and (ii) the state of a particle is given by a wavefunction only as approximation. Your anonymous repetitive attacks (including to people who is not here for defending himself) will not change the facts: In the same wikipedia page you can read from another editor: And if you follow this user (http://www.phys.tue.nl/ktn/Wim/muynck.htm), you find that he has 'some' knowledge in foundations of quantum mechanics. One time again. Our modern picture of the physical world is as follows: Light is made of particles. Atoms are made of particles. Everything in the observable universe is made of particles. Electrons, photons, quarks... are particles. Particles behave as particles. Sometimes a collection of particles behaves collectively as a wave. E.g. a collection of photons under certain restrictions behave as a EM wave, but each individual photon behaves as a particle. A collection of electrons in a double-slit experiment generate a interference pattern that resembles a classical wave, but each individual electron behaves as a particle, following the laws of the quantum mechanics of particles.

A classical particle is a limiting case of a quantum particle. That is the reason which we write "particle". It is worth to mention that some author prefer a different terminology. For instance a quantum chemist writes: Others, including myself, prefer a more standard and logic terminology: classical mechanics <--> quantum mechanics classical particle <--> quantum particle Then you must be objecting to using the term "mechanics" in any discussion of quantum theory with a non-physicist, because in one sense we have redefined "mechanics" and it is no more is a synonym for "classical mechanics". What new terminology do you propose? classical particle <--> wavicle? classical mechanics <--> ? In my first post in this thread I outlined how a classical electromagnetic wave is an approximation to an underlying theory of particles (photons).

It is ironic that a poster uses an old quote from Dirac about wavefunctions for posting attacks to posters who do not buy the duality myth. This poster calls "crackpot science" to what others call modern quantum physics. It is ironic because any modern textbook on quantum physics emphasizes how wrong Dirac was regarding wavefunctions! Yes, textbooks explain how the solutions to the Dirac equation cannot be wavefunctions, in despite that Dirac initially interpreted them as wavefunctions. Dirac was wrong about such wavefunctions, because he missed some advanced aspects of quantum physics. Today we know that the Dirac equation is not a valid wave equation for an electron. I am also perplexed why some posters insist on confounding a wavefunction (i.e. a function without physical meaning) with a wave (i.e. a physical system with physical properties). Since that the wikipedia has been cited. Let us take a look to the talk page: A theoretical physicist writes about the wave-particle duality myth: In fact, as everyone can check the IUPAC definition of electron do not mention duality and the CERN glossary about modern physics do not mention duality.

(i) It is not "Juan's definitions" but the standard physicists and chemists definition. And (ii) the quantum definition of particle is not a classical definition. I even stated how one of the properties of a quantum particle (spin) has not classical counterpart.

The electromagnetic field is not a vector field, but is given by a tensor [math]F^{\mu\nu}[/math]. The Higgs field is not on "top of" another field. As explained above fields are defined over spacetime. The Higgs field is another field. A point in spacetime cannot have a field nor many fields. A field is a physical system extended over the whole spacetime. At any given spacetime point the field takes a value. By virtue of the superposition principle several fields can be existing over the same spacetime.