When I was observing the Moon yesterday, I asked myself:
What would happen if a meteoroid impacted the Moon on the more clear part of the Moon which we can see, leaving a crater of the size like the region of the upper left part of the moon when observing it?
a) How would the impact look? Would you be able to spot the aproaching object seconds before impact with the naked eye? Could you observe with the naked eye debris of the Moon pushed into the space?
b) Would a impact on that scale directly have some impact on Earth? I.e. would the Moon lose by this event enough mass to cause a notable change to our tides?
And first of all: would this impact cause any possible danger for us, humans, like debris from the Moon colliding with earth?