Wednesday, 8 July 2009

Quantum Fluctuations

Quantum Fluctuations :
The fact that the Universe exists should not be a surprise in the context of what we know about quantum
physics. The uncertainty and unpredictability of the quantum world is manifested in the fact that whatever
can happen, does happen (this is often called the principle of totalitarianism, that if a quantum
mechanical process is not strictly forbidden, then it must occur).
For example, radioactive decay occurs when two protons and two neutrons (an alpha particle) leap
out of an atomic nuclei. Since the positions of the protons and neutrons is governed by the wave
function, there is a small, but finite, probability that all four will quantum tunnel outside the
nucleus, and therefore escape. The probability of this happening is small, but given enough time
(tens of years) it will happen.
The same principles were probably in effect at the time of the Big Bang (although we can not test
this hypothesis within our current framework of physics). But as such, the fluctuations in the
quantum vacuum effectively guarantee that the Universe would come into existence.
Planck Era :
The earliest moments of Creation are where our modern physics breakdown, where `breakdown'
means that our theories and laws have no ability to describe or predict the behavior of the early
Universe. Our everyday notions of space and time cease to be valid.
Although we have little knowledge of the Universe before the Planck time, only speculation, we can
calculate when this era ends and when our physics begins. The hot Big Bang model, together with
the ideas of modern particle physics, provides a sound framework for sensible speculation back to
the Planck era. This occurs when the Universe is at the Planck scale in its expansion.

Remember, there is no `outside' to the Universe. So one can only measure the size of the Universe
much like you measure the radius of the Earth. You don't dig a hole in the Earth and lower a tape
measure, you measure the circumference (take an airplane ride) of the Earth and divide by 2 pi (i.e.
C = 2 x pi x radius).
The Universe expands from the moment of the Big Bang, but until the Universe reaches the size of
the Planck scale, there is no time or space. Time remains undefined, space is compactified. String
theory maintains that the Universe had 10 dimensions during the Planck era, which collapses into 4
at the end of the Planck era (think of those extra 6 dimensions as being very, very small
hyperspheres inbetween the space between elementary particles, 4 big dimensions and 6 little tiny
During the Planck era, the Universe can be best described as a quantum foam of 10 dimensions
containing Planck length sized black holes continuously being created and annihilated with no
cause or effect. In other words, try not to think about this era in normal terms.

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