Kailashnath Mahadev

Shivratri is the time when Shiva takes a rest.
Shiva rests for one 'prahar' (three hours) of the night..
This 'prahar' is referred to as the Shivratri.
When Lord Shiva takes rest, the function of
'Shivtatva' (Shiva Principle) ceases,
i.e. Lord Shiva goes into a meditative state.



Shiva's meditative state is the time when
He is engrossed in His own spiritual practice.
During that time,
the 'Shivtatva' does not accept any tamogun
(most base of the 3 elements in us - sattva, raja & tama)
or
any halahal (venom churned from the ocean)
coming from the Universe.
As a result,
the ratio of halahal or the pressure
of the negative energies increases.
For protection from this pressure, things like
'bilva patra', white flowers, 'rudraksha' beads etc
are offered to Lord Shiva.

These things attract the 'Shivtatva' from the atmosphere,
thus providing protection from the increasing
effect of the negative energies.
The Earth is a gross object.
Gross objects have very low velocities
i.e. they require more time to cover a specific distance in space.
Gods on the other hand, are subtle hence they
are capable of traversing space within a few seconds.
That is why one year on the earth
is equivalent to just one day of heaven.