We instinctively recognize that the creation of disorder is the
natural course of spontaneous events in the real world. In the animations
on the right, the motorcyclist, initially moving with a high kinetic
energy, hits a brick wall. His kinetic energy of motion is changed
into energy needed to break the bricks apart, into a large increase
in disorder, and into random molecular motion of the metal parts
of the wreckage, which will be warm to the touch. This is the normal,
or expected, chain of events. In the drawings below, kinetic energy
is changed into work to break down the wall, disorder, and heat
to warm the wreckage.
In the third panel this work, disorder, and heat have been recombined
and reconverted back into the kinetic energy of the now-unharmed
motorcyclist, who goes on his way. We instinctively recognize this
as ridiculous. Disorder comes spontaneously from order in our universe,
but order cannot come spontaneously from disorder. Random motion
(heat) tends to stay random unless we make an effort to "unrandomize"
it. For this we must pay a price in energy. We can rebuild the brick
wall if we make the effort, but the bricks will not fall into place
by themselves, as the bottom scenario would have it.
We now have a second factor to consider in spontaneous processes:
disorder. Spontaneous reactions tend to occur in the direction of
lower energy, but they also tend to occur in the direction of greater
disorder. In some cases both trends may reinforce; in others the
result may be a trade-off between two opposing tendencies.
scenarios shown involve a spontaneous creation of disorder, and
is intuitively recognised as possible occurence. In contrast the
scene involving spontaneous re-creation of order after a catastrophe,is
rejected by common sense and past experience.