If we would like to calculate roughly how many collisions there
have been so far in the life of a particle since
beginning of the world, we could start from the fact
that the collisions for a gas molecule at normal
temperature and pressure are in the range of 1010
In the liquid state they are in the same order of magnitude.
There are many more inside a star.
There are over 2 × 1017 collisions per second.
In the initial
fireball of the Big Bang
there must have been even more.
In interstellar space, where the particle was at some time, there are far fewer.
If we accept
an average of 2 × 1015
we would not be far wrong.
With so many collisions per second,
for the 5
× 1017 seconds of the history of the World
we can say that
each particle must have suffered from the
of the world till today some 1033 collisions.