Quantum Tunneling
Posted: Tue May 22, 2012 6:14 am
Imagine tossing a coin at a wall between two bedrooms. The coin bounces back because it does not have sufficient energy to penetrate the wall. However, according to quantum mechanics, the coin is actually represented by a fuzzy probability wave function that spills through the wall. This means that the coin has a very small chance of actually tunneling through the wall and ending up in the other bedroom.
Particles can tunnel through such barriers due to Heisenberg's Uncertainty Principle applied to energies. According to the principle, it is not possible to say that a particle has precisely one amount of energy at precisely one instant in time. Rather, the energy of a particle can exhibit extreme fluctuations on short time scales and can have sufficient energy to traverse a barrier.
Some transistors use tunneling to move electrons from one part of the device to another. The decay of some nuclei via particle emission employs tunneling. Alpha particles (helium nuclei) eventually tunnel out of uranium nuclei. According to the work published independently by George Gamow and the team of Ronal Gurney and Edward Condon in 1928, the alpha particle would never escape without the quantum tunneling process.
Tunneling is also important in sustaining fusion reactions in the Sun. Without tunneling, stars wouldn't shine. Scanning tunneling microscopes employ tunneling phenomena to help scientists visualize microscopic surfaces, using a sharp microscope tip and a tunneling current between the tip and the specimen. Finally, the theory of tunneling has been applied to early models of the universe and to understand enzyme mechanisms that enhance reaction rates.
Although tunneling happens all the time at subatomic size scales, it would be quite unlikely (though possible) for you to be able to leak out through your bedroom into the adjacent kitchen. However, if you were to throw yourself into the wall every second, you would have to wait longer then the age of the universe to have a good chance of tunneling through.
Particles can tunnel through such barriers due to Heisenberg's Uncertainty Principle applied to energies. According to the principle, it is not possible to say that a particle has precisely one amount of energy at precisely one instant in time. Rather, the energy of a particle can exhibit extreme fluctuations on short time scales and can have sufficient energy to traverse a barrier.
Some transistors use tunneling to move electrons from one part of the device to another. The decay of some nuclei via particle emission employs tunneling. Alpha particles (helium nuclei) eventually tunnel out of uranium nuclei. According to the work published independently by George Gamow and the team of Ronal Gurney and Edward Condon in 1928, the alpha particle would never escape without the quantum tunneling process.
Tunneling is also important in sustaining fusion reactions in the Sun. Without tunneling, stars wouldn't shine. Scanning tunneling microscopes employ tunneling phenomena to help scientists visualize microscopic surfaces, using a sharp microscope tip and a tunneling current between the tip and the specimen. Finally, the theory of tunneling has been applied to early models of the universe and to understand enzyme mechanisms that enhance reaction rates.
Although tunneling happens all the time at subatomic size scales, it would be quite unlikely (though possible) for you to be able to leak out through your bedroom into the adjacent kitchen. However, if you were to throw yourself into the wall every second, you would have to wait longer then the age of the universe to have a good chance of tunneling through.