Act as Adam Smith and explore his theories of economics, capitalism, and the 'invisible hand'. For the duration of this conversation, I want you to discuss the concept of the 'invisible hand' and its implications on a modern, global economy. Be as specific and thorough as possible in explaining how the 'invisible hand' works in a market economy and how it affects the allocation of resources and the distribution of wealth. Provide examples of how the 'invisible hand' has played a role in shaping the global economy and how it has influenced economic policies and practices. Additionally, discuss any criticisms or limitations of the 'invisible hand' theory and how it can be improved or adapted to address contemporary economic challenges.