There was little research done for many years. The trouble once anything is declared a controlled substance research become very hard due the need to secure the substance at the lab, getting it to the lab and anywhere you need to take the substance. All this is after convincing the government that you have a case that the substance will do what you think it will and that medical use will not cause the substance to be abused. If you jump through all the hoops and complete all the mountains of paperwork, you finally have to source and import the substance. This will require more paperwork and so on in the source country.

Are we talking about converting from pagan to catholic? The conversions were mostly top down with the king and court converting and putting a catholic layer over lingering paganism that lasted underground for generations afterwards. The biggest reason is the King went from being in charge because blood and force to anointed agent of God, making fighting the King the same as fighting god. Then you had the ease of dealing with few bishops rather than dozens of local priests in religious matters. The priests brought in bureaucracy as they were literate and many became clerks for the King allowing greater control and communications. laws were written down and taxes became more formalised and legal agreements such as treaties and land holdings stopped being based memory.

It could be a after effect of a being gassed some time in the past.

The Soviet Union stretched from East Germany to the Pacific ocean with many aligned states or at least using Soviet military equipment in the middle east. The Soviet had close trade and political links leading the to some Western commentators to use the "Eurasia" for a shorthand for this area. This usage of the term lacks nuance but is not broadly inaccurate if talking about modern history.

Grenades were never 3-4lbs, what you are talking about is mortar/cannon shells. Most grenades were ceramic and weighted much less that. They were about the size of a modern cricket ball according to most books I've seen about early modern grenades in the UK. The small blast radius and poor fuses compared to modern grenades made them only used in sieges and storming of fortified works. They were terror weapons like fire lances and other fireworks.
There are accounts of musketeers in the English Civil War carrying a half dozen in their knapsack when storming fortified town. The is one account I remember of grenades being used to force the surrender of church where troops were holding out.

Swords held a social place outside the practical weapon, when a English Civil War general proposed giving the infantry axes rather than sword "as all they use them for is to chop wood". This kept them as a badge of rank and why the cavalry who needed swords styled themselves gentlemen.

One of the big factors was reorganising the logistics train such as lighter equipment to advancing on wider front to improve forage. This dependence on forage, made a smaller supply train and allowed swift movement that allowed him to choose where and when to fight. This fell apart with the guerrilla war in Spain and the retreat from Moscow where he was forced to fall back or the same path as his advance and the Russians using scorched earth tactics.

Issac Newton was the master of the royal mint (1696-1727) and invented the edging you see on coins to prevent clipping.

Medieval currency was based on the value of the metal and as inflation, metal supply and the purity of the metal, so new coins was minted. Then they also made coins to fit common transactions.

The answers below are all factors but he was and average general vs the best in Lee, after all both sides asked him to run their armies. He got bluffed into thinking Lee had twice as many troops than he had, still less the McClellan. McClellan thought it was between 1.5 to 1 and 2 to 1, he wanted the 3 to 1, which the military thinking of time would mean he would win, with the wrong odds he might it would be bloody and he was facing a more experienced and "better" general.
So he waited pulling in more troops which gave away the initiative when (in hindsight) he could have smashed the south and knocked a few years off the war.

There were poorer generals in the war on both sides but he allowed Lee to build a army and then failed to win when he did fight.

A account from the 1400's I read long ago of two noble families of five brothers were in a feud and decided to settle it by each side bringing 100 men and fighting until it was settled. Three days fighting later only the five brothers on each were standing and they called the matter settled. It was noted they were the only ones in full armour.

Part of the answer is that the Vikings took longer to reach America, most sailed from Greenland. So a disease would have to start in the big towns in Europe, then be taken to Iceland, with a smaller population with no big towns which would limit spread. Then to Greenland with a smaller population before reaching the New World.

There ae some real stinkers on the list

Why, apart from their job was fighting in wars and jousts was good training but it was also a way to make a lot of money! many jousts with big melees or massed fights in teams allowed opponents to be captured and ransomed. Even if that was not allowed there were often valuable prizes and for unknown knights and those without a holding it was a good way to show good you were making it possible to gain a position in great lords household. So knights went from poor landless knights to in one case the Marshall of England, based mainly on his fame and wealth from jousting.