Natural Levitation

  1. I have heard that non-cohesive surface contact is such that any given "object1" is floating on "object2" in the sense that there is a separation, however small, due to electron repulsion.
    When I pick up my coffee cup, under this theory, my fingers never actually touch the cup, rather interact with the electron field, keeping a small but actualized separation between the electrons in my fingers and the electrons of the cup.
    Is this true?
     
  2. jcsd
  3. What is touch, but this sort of "levitation"?
     
  4. So, given this, would it be proper to suggest than non-extreme physical "contact" is a field-to-field encounter? That is, in "sliding friction" are the surfaces having direct electron-electron movement resistance, or, is the resistance a "bumpy field"?
     
    Last edited: Jan 23, 2004
  5. The reason you can hold a coffee cup is Pauli's Exclusion Principle, according to which no two electrons in an atom may be in the same quantum state.

    In one word that's impossible.

    I agree with you that Physics can be surprising, but you had better don't use something like "levitation". This isn't magic, this is as real as we are.
     
  6. LURCH

    LURCH 2,514
    Science Advisor

    Truth is, the exact sause of friction is not well understood. About a year ago I read an artical in SciAm commenting on how odd this is, both that the principles remain somewhat vague and that greater effort is not being expended to unlock these secrets. after all, nearly every industry in the world would benefit to some degree by a better understanding of how to reduce friction.

    However, you are correct in saying that nearly all forms fo physical contact are field-to-field. When you stand and your feet do not pass through the floor, you are practicing magnetic levitation. When you place your hand against the wall and the wall stops your hand from going any further, it is the negative charge of the electrons in your hand repelling the negative charge of the electrons in the wall. Both the wall and your hand are something like 99.9999% empty space and without the electromagnetic rpulsion, you'd pass right through each other like neutrinos passing in the night.
     
  7. I agree with everyone. In particular, thanks, LURCH, for expanding on it. As bizzare as it may seem to an ordinary person, direct physical contact with another object is not possible(excepting nuclear interactions, of course) and is rather a field-to-field "contact".
     
  8. This is in no way close to correct. The question you are asking is why some materials have a bulk modulus and others do not. It's due to electrostatic forces. NOT PAULI'S PRINCIPLE. Pauli's principle is another way of describing the sysmtry of the wavefunction of electrons in an amotic system.


    JMD
     
  9. Sko

    Sko 0

    So if I understand Lurch right, when I hit something with my hand I'm really just electromagnetically repelling it or is it actual contact between particles?
     
  10. russ_watters

    Staff: Mentor

    You're just electromagnetically repelling it.

    It may be tough to accept, but chew on this: what "particles" would touch? Electrons? Protons? Neutrons? Quarks?
     
  11. I'm not an expert, you may be right. But Leon Lederman says that (in The God Particle):
    "The dramatic result of Pauli's principle is that if a shell is full, it is impossible to add more electrons there. The main reason for matter to cannot be gone through is this. There is a serious problem in passing through a wall although atoms are %99.999 empty space. Maybe you will share this obstruction. Why? In solids where atoms are clamped together, our bodies' electrons' being pushed into the "wall" atoms meets with Pauli's prohibition for electrons to be very near each other. A bullet can pierce the wall because it cuts the atom-atom bonds and makes way for its electrons as the same as a rugby player does."

    [translation]

    He is (was) an experimental physicist, but I dont think that he made such a mistake.

    Maybe the subject has more dimensions.
     

  12. If you have 2 atoms, there are 2 sets of quantum numbers that can be filled. NOw, two free atoms maybe different from two atoms that are bonded.

    JMD
     
  13. This is all somewhat confusing...I understand that nothing ever really touches anything else.

    Which is odd, because about the age of twelve I started thinking about that exact concept, but my physics teachers always said "yes, things touch".
     
  14. Friction is such a common concept that one would think it's understood very well. I found this on the hyperphysics website:

    http://hyperphysics.phy-astr.gsu.edu/hbase/frict.html


    Why did you use magnetism in your description of standing on the floor and electric forces when pressing against a wall? Are both forces involved in both instances?
     
    Last edited: Jan 25, 2004
  15. Yeah, friction and gravity are two things that are somewhat understood in what their effect is, but not really what causes them.
     
  16. I think gravity must be seperated. What really causes the Physical law to be as it is is Philosophy, not Physics. Laws of gravity are understood completely.* But is a planet calculating the distance to the sun and behaving as it calculated? No. We don't know why it is 1/r^2.

    *General Relativity dislikes Quantum.
     
  17. selfAdjoint

    selfAdjoint 8,147
    Staff Emeritus
    Gold Member

    If I understand you, this is the old conundrum "How does a planet know to keep in its orbit? How does it know to obey the [tex]1/r^2[/tex] law? It doesn't. In General Relativity the path it takes is a geodesic, meaning if it were to stray from that path it would have to "slide uphill", and it can't do that. This then automatically gives the [tex]1/r^2[/tex] law in the Newtonian approximation.
     
  18. Can you give more info? I don't know GR deeply.
     
  19. LURCH

    LURCH 2,514
    Science Advisor

    Yes, it is the magnetic repulsion between two "like charges" that is at work in both instances. I merely used the phrase "magnetic levitation" because that is a widely used term (maglev). But then I realised I couldn't very well use that term for the interaction between your hand and the wall, because it's not "levitation" unless it's working against gravity.
     
  20. Basically what I said...nothing contradicting between us here..
     
  21. Well the simplest explanation is often the best. Remember 7th grade science? Remember "no matter can occupy the same space at the same time..That sums it up .( There are all kinds of theoretical exclusions when it comes to QM , but this pretty well describes the issue at atomic scale matter and up)
    The nearest Newtonian example that would approach Your quires is a covalent bond in chemistry , where electrons are shared between atoms.
     
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