Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Quantum Tunelling

  1. Jul 24, 2006 #1
    Ok, I understand that it is about those negligable probabilities that end up happening, but b/c we don't live long enough to see these probability happen in our real life(big objects take longer time), we have seen that quantum tunelling exist on nanoscopic level. Now, what I don't understand is that how is it possible? I know it has been proven, and makes sense by probability but still. I guess it just bothers me to see something happening that is not supported by our physical laws. I believe everything happens for a reason(causuality) but this counters it.
     
  2. jcsd
  3. Jul 24, 2006 #2
    Who said tunneling was not supported by physical laws? If it isn't, semiconductors and scanning tunneling microscopes would be something out of science fiction.
     
  4. Jul 24, 2006 #3
    then could you explain to me how is it possible for me to jump here and vanish and go inside a black hole?
     
  5. Jul 24, 2006 #4

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

  6. Jul 24, 2006 #5
    are you sure you wanna do that? , actually quantum tunneling is a phenomena in which a quantum particle can enter a classically forbidden region , and this isnt as wierd as it seems to you , infact it has been already put to use in tunneling microscopes with high results.
    You can read about it here:
    http://en.wikipedia.org/wiki/Quantum_tunneling
     
  7. Jul 24, 2006 #6
    That was a good read, Zap.
     
  8. Jul 25, 2006 #7
    Yeah, that zap post got me, thx a lot guys
     
  9. Aug 1, 2006 #8
    That's not quantum tunneling, that's quantum teleportation! :smile:
     
  10. Aug 1, 2006 #9
    It would be possible for you to jump over classical barriers if you were a quantum particle. I.e., a particle that obeys rule of quantum mechanics and doesn't care about classical mechanics.
    Quantum mechanics, in contra to classical mechanics says that any waveform of any particle may go through barriers that classical particle with same properties can't go through.
    So, yes, this effect is described by laws of QM.
     
    Last edited: Aug 1, 2006
  11. Aug 2, 2006 #10
    I am not sure this is really necessary. I suspect theoretically you can jump over a classical barrier having lesser kinetic energy than the potential energy your mass would have at the top of the barrier. In fact, in the course of a high jump you can bend over the barrier in such a way that your center of gravity will be outside of your body and pass under the barrier.
     
  12. Aug 2, 2006 #11
    That's a nice way of putting it, akhmeteli.

    I thought this "Quantum Tunneling on your Kitchen table" looked interesting. I don't know if it's genuine though.

    http://www.altair.org/Qtunnel.html

    But anyhow, IMHO quantum tunneling is only weird if you think of things like electrons as billiard-ball particles.
     
  13. Aug 2, 2006 #12
    Wow, that's an interesting site you listed, Farsight. You mentioned that you are not sure of its genuiness, so I hope that others can jump in and clarify that aspect.
     
  14. Aug 3, 2006 #13
    I'm not too sure about that site. Someone with more knowledge will have to look at it. For one thing, it even says that quantum physics "superceded" the physics of einstein; never mind that Einstein was one of the most important contributors to quantum theory in the beginning of the 20th century.
     
  15. Aug 3, 2006 #14
    The weak force

    Superwierdo, you are asking about the weak force. That is the force that causes atoms to decay. You see, certain atoms know as isotopes, are radioactive because they contain one or two less neutrons or one or two more protons then there stable counterparts. If you look at the periodic table, you will find that each element has a mass number. This is the total number of protons and neutrons in each atom. Carbon, for example, has a mass number of twelve, while there is an isotope known as carbon-14 which is used in carbon dating.
    Now the nuclei of non-radioactive atoms are held together by the strong force. But when the atom is missing neutrons or in excess of protons then the strong force breaks down and the protons, due to their like charges, repel. It is not the protons repelling which causes the nuclei to dissolve slowly, it is the replacing of the strong force with the weak force.
     
  16. Aug 4, 2006 #15
    But where is the weak force? All I see is repulsion.
     
  17. Aug 4, 2006 #16
    Quantum tunneling and the weak force

    I don't know exactly where the weak force comes from. I've never read anything that has the answer. I don't think modern science has found a way to accurately describe it.
     
  18. Aug 4, 2006 #17

    ZapperZ

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    No, I thnk it was rather strange that you introduced the "weak force" in this thread. I'm not sure what you were trying to explain, even after re-reading your earlier post.

    There there have been description of alpha decay via the tunneling through the electrostatic potential barrier. However, this doesn't mean that all radioactive decay is a governed by such a process. The weak interaction is much more complex and "powerful" than this. And yes, "modern science" does know a lot about this process. We may not know all of it yet, but the same can be said about almost anything. Still, we know that the weak interaction can have a CP-violating component, and other characteristics, enough that we have a consistent electroweak description.

    Zz.
     
  19. Aug 5, 2006 #18
    So sorry. won't do it again. You're right, it's not pertinent.
     
  20. Aug 5, 2006 #19

    Just remembered why I thought about it though
     
  21. Aug 5, 2006 #20
    I know this is kind of offtopic but since we are already there and my purpose is solved in this thread, could someone explain to me what is weak force?(more than that it causes alpha decay)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?