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Quantum Tunneling - some silly thoughts

  1. Jul 14, 2009 #1
    From what I read, there is an extremely small probability of one going through a solid wall, according to QM. The chance is so small you might have wait a few lifetimes, or more of the universe to observe it.

    But how about going very shallowly into the wall?
    Let's say a few angstroms (Å).
    Would the possibility be much higher?

    Hmm...also what if my fingers indeed successfully tunneled into a wall (very shallowly)?
    Would my atoms somehow mingle with those of the wall's?

  2. jcsd
  3. Jul 15, 2009 #2


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    First: The probability of your finger, body, or anything tunneling anywhere through anything is so astronomically small, for all intents and purposes it is equal to zero. Even if the individual probabilities of each particle tunneling is within the penetration distance, the probability of all your particles doing so at the same time is, like I said, zero. Even if the distance is only a few angstroms.

    I'm not sure how to model a wall, the only thing that comes to mind is a potential barrier of some height, which your finger (or body) is below. Not sure how to model the internal structure of a wall (solid) though, so it's difficult for me to say what would happen if matter did tunnel into (not through) it.
  4. Jul 15, 2009 #3
    Well, it would be "is it possible for a few atoms of my finger tips to quantum tunnel out of the potential wells holding them into atoms, and travel in between the atoms of the wall"

    First, possible, highly unlikely, because if it was likely, molecules would routinely quantum tunnel apart. Also, atoms in general do not tunnel, they're too massive to have a reasonable chance.
  5. Jul 16, 2009 #4
    If you want to talk about very small probabilities, there is a very small probability of absolutely anything occurring. There's a small probability that I will meet you on the street tomorrow and punch you in the stomach, for example. Of course, we both know that this won't happen (or hope it won't, in your case.) Very small probabilities are meaningless.

    Is it possible that some atoms of your finger could "tunnel" into the wall? This is a much more interesting question. Actually, however, the question you are asking is not really quantum mechanically relevant. Consider the elements comprising your skin, for example. It is well known that humans shed a huge amount of skin, constantly, although this is difficult to witness (except for extremely bad dandruff, which you can spot easily.) When you touch the wall, probably bits of your skin are touching the surface and staying behind. This is already examining the situation at an extremely microscopic level. If you want to consider the quantum level, you would be talking about a negligible interaction between your finger and the wall. For example, at the interface between your finger and the wall, if you keep zooming in closer and closer, you will find mostly empty space. Once you are looking close enough at the interface to see particles, the picture will be extremely disjoint from anything else around it. Nothing especially interesting would be going on, because the atoms are too far apart, and they are not very energetic. Quantum effects like tunneling are basically irrelevant in this situation, and I would suspect that you do not see any of the phenomenon occurring.
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