Every so often I read a sneer about the Middle Ages. Many people believe that if the Middle Ages didn't happen we would be much better off, we would live in a Star Trek like world by now.
The Middle Ages were bad, that's what we learn in school. They are often referred to as the dark ages, a time of chaos, war, oppression, crusades, diseases, poverty, slavery and other bad things that were going on throughout in that Europe for many hundreds of years.
Rather than attempting to describe this really long and complicated period I'll just say that it roughly lasted from the year 500 until 1500, even though it started earlier in some areas and in some rural areas Eastern Europe didn't change much the twentieth(!) century.
About what caused the Middle Ages not much is known. People didn't bother to document much in a time of chaos, and if they did much of the work was lost.
I don't think that there is a single factor to blame. The Middle Ages didn't come in one night, it's a combination of many things coming together in a period of centuries that "caused" the Middle Ages.
The collapse of the Roman empire has often been blamed. The romans were quite advanced for their time, had their empire survived we would be more advanced now. I can't say that we wouldn't, but I wouldn't bet on it. Romans didn't really picture themselves as inventors, artists or explorers. They raised their sons to become conquerers and warriors, they did not consider showing compassion for others to be an admirable quality.
After the peak years of the empire the economy started to shrink, Christianity was eventually made the state religion, but by then there was not much left of the once so great empire.
The empire continued to shrink and grow weaker until it eventually disappeared, just like all other great civilizations that came before. Order slipped into chaos. It became unsafe to travel outside of town, traders stopped traveling and people left the cities to find food in the country. Many of these people found protection by land owners, but had to give up their many of their civil rights and became serfs, farmers in service of a land owner.
Now the Middle Ages had begun. There were a few kingdoms which changed frequently, but most of the time the land owners were in charge of their own tiny state, competing with other nearby land owners for wealth and power.
During this time the Christian church was the only stable institution that had influence throughout the continent and had an important role in preserving literacy, but it's actual power was fairly limited.
The Middle Ages were hard times, with many people competing with each other. This allowed human ingenuity to thrive. Many inventions were done, I haven't been able to find a complete list yet, probably because it would get really long. Here is one incomplete list and many more here.
It weren't just technological inventions, but also in every other field great progress was made. Engineering, medicine, geometry, mathematics were all practiced and improved. Alchemists were trying to find ways to turn lead into gold, laying the foundations for modern chemistry. Explorers from Europe were traveling around the world bringing back even more technology and inventions from the Middle and Far East and eventually discovered another continent now called America in the West.
During the Middle Ages Japan and China were quite advanced, maybe even more than Europe. Why didn't they develop much further? Nobody knows for sure. The most common assumption is that they were both stable empires where people were working efficiently together, and that there was simply no need for them to develop any further.
By the year 1500 book printing allowed knowledge to be shared faster and cheaper than ever before, a huge step forward for mankind. How could we ever survive without it? The name,"Middle Ages" and the idea that it was a bad time.
But for the first time ever a civilization could travel around the world and had technologies unlike anything that existed on Earth before. How was this possible? It's because of those "damn" Middle Ages!
The Middle Ages weren't easy times, and many bad things happened and still continue happen. What is important is that the Middle Ages eventually allowed mankind to become what we are today, and we could have done far worse.
Realizing that the Middle Ages was a time of development and progress proves to me that accelerated technological progress (The Law of Acceleration Returns) is really happening right now, and has been going on for many hundreds of years.