### quantum tunneling

**(tunneling, barrier penetration)**
(quantum mechanical effect of particles passing through a barrier)

**Quantum tunneling** (or just **tunneling**, or **barrier penetration**)
is a quantum-mechanical effect demonstrating some strangeness of the
**Heisenberg uncertainty principle**, which states that there is a minimum
possible product of the certainty of a particle's momentum
and the certainty of that particle's position. If a particle
is sufficiently close to a sufficiently thin wall (barrier),
this uncertainty says there's a chance the
particle could be on the other side.
A particle approaching one side of the wall
could ultimately be found to be on the other side,
a phenomenon termed *tunneling* or *barrier penetration*.
Since there is a finite chance that this happens,
with sufficient repeated attempts,
the odds of a particle getting through rises to virtual inevitability.

This shows the Heisenberg uncertainty principle is
not merely "not knowing where the particle is",
but that particles are such that an "exact location"
is a useless concept.
As weird as the effect seems, it is ubiquitous,
being an integral part of **fusion** (thus the shining of the Sun),
of radioactivity,
and of electronic components including the **tunnel diode**,
which clearly do their function in common consumer devices.

In astronomy, models of stellar structure
depend upon a calculation of the fusion rate in a
specific plasma according to its temperature and pressure,
calculations that include the effect of this tunneling,
and stars basically wouldn't shine very much without it.

(*physics,quantum mechanics,radioactivity*)
http://en.wikipedia.org/wiki/Quantum_tunnelling

**Referenced by:**

Gamow peak

quantum mechanics (QM)

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