Meaning of "time" related to existence of the universe

Question

A question, that bugs me since a long time already, are sentences like "in the first second after the big bang".
The problem that I have, is that time measurements would need an observer, which in turn perceives time in relative way; in order to make the measurements meaningful, an inertial system containing the universe and the observer would be required and my question is, what that reference system is, resp. whether I misunderstood something.

Answer 1

You need an observer for the measurement of time, but time passes also without the observer.

According to special and general relativity, each particle is following its own time. We may take an electron as a simple example. An electron is characterized by its spin. You can follow an electron from its creation and count the number of spin rotations in order to determine its age. But no observer is required for the spin of the electron, the electron is aging without any observer and without ever being measured. It is the proper time of the electron.

This does not apply to lightlike phenomena such as photons in vacuum, their proper time is zero, and for their aging, an observer is required.

As a conclusion we may strongly presume that some proper-time-generating phenomena existed since the very beginning of the big bang, because we cannot imagine any existence of time in a world of lightlike phenomena without observer.