The period of time between the First Galactic War and The Collapse.
After a few centuries of demilitarization, science and technology advanced rapidly. Transit mathematics were pushed to their limits within human understanding and some attempts were made to reach other galaxies. These attempts were ultimately unsuccessful, but the mathematics developed are still used today.
Unfortunately, the second golden age was to be short lived. The slow infiltration and sabotage by Morocaschics and later, a plague, nearly led to the end of humanity.