For thousands of years humanity's evolution progressed slowly and never steady. History would erase many traces of previously found knowledge, only to have it rediscovered much later.
The Expansion of knowledge happens through peace and war:
In times of war, all participating nations would progress at astonishing speed, out of necessity to be the final victor. But participating in a war could mean losing everything a country stood for and technology and knowledge can be lost, when critical facilities are destroyed or important people die.
In times of peace, progress is a lot slower, but although many become more stagnant, it can not be undone easily, as nobody will be there to get rid of it.
It is therefore no wonder, that the most progress can be made, while being under constant tension, but staying out of a direct conflict , as seen in the Cold War, when even landing men on the moon was not impossible for humanity's superpowers.
But progress is not linear. It is exponential. Through progress more progress can be achieved and when a certain point, called the Singularity is reached, progress will become uncontrollably quick and irreversible.
Under these circumstances the people of earth thrived after the 21st century. Through 900 years of constant progress, mankind worked their way towards this point knowingly or, which was far more common, unknowingly.
Those that believed in the Singularity thought it to be imminent, as artificial intelligence had nearly been developed to be as advanced as the human brain. It was theorised, that, when one could create an AI, that could improve itself, it would begin an infinite cycle of self improvements, leading said AI to become infinitely intelligent and knowledgeable.
But even in the year 2900 it was still not AI that could feed the people, build their houses or transport them through space.
Significant resources had been used, for centuries at this point, to improve the living conditions of the citizens of wealthy countries and even those, which were once considered to be third world countries were now unbelievably more advanced.
But the difference between them was still large. While some countries had to greatly compete on nearby cosmic entities for few and scarce resources or had to plan trips lasting months or even years, others could travel to the outermost parts of their solar system in a few days, finding extremely rich deposits of valuable goods and creating reliable infrastructure to guarantee constant flow of them back to their home country.
Richer countries could also afford better protection for their vessels and personal.
This would result in lesser casualties on expeditions and mining missions.
They often did not even have to work themselves, as a lot of physical labour could be outsourced to people from countries, that were not as technologically advanced.
Although the difference between rich and poor didn't decrease but may have even increased, because of the sheer amount of prosperity at least some parts of the world could generate, people began calling this period of time
"The Golden Age Of Technology".