How do we know that the universe doesn’t rotate? Why would it matter if it did? What does all this have to do with time travel?

How do we know that the universe doesn’t rotate? Why would it matter if it did? What does all this have to do with time travel?
What are blue straggler stars? How were they first discovered? What do they tell us about star clusters and the evolution of stars? I discuss these questions and more in today’s Ask a Spaceman!
Is it possible for anything to travel faster than light? What about tachyons? How would faster-than-light travel break causality?
What is the role of consciousness in quantum mechanics, if there even is one? Is there any way at all to develop a coherent view of nature based on quantum mechanics? What are the ultimate lessons that we can learn from quantum mechanics?
What is real in quantum mechanics, and what are mere mathematical tricks? Can the probability waves be real, and what would that mean? What is Pilot-Wave theory?
What is the many-worlds interpretation of quantum mechanics? How does decoherence play a critical role? What are the strengths and weaknesses of this idea? Find the answer with @PaulMattSutter at #365DaysOfAstro
What were Einstein’s objections to quantum mechanics? Why was he so bothered by non-locality? What is the EPR paradox?
What is the Copenhagen interpretation? How did the debates between Heisenberg and Schrodinger influence later physicists? What are the strengths and weaknesses of the “shut up and calculate” approach to quantum mechanics?
What are the basic lessons of quantum mechanics? What does quantum mechanics teach us about the nature of reality? How does a quantum worldview differ from a classical one?
Who developed quantum theory and why? What experiments motivated the creation of quantum mechanics? How was quantum mechanics a total break from classical physics?