This movie even begins with decent physics in mind with the arrival of Dr. Floyd to a space shuttle where the idea is that there is zero gravity. It shows the people struggling to walk and how everything floats away when is not strapped down with velcro. The landing of the space shuttle and the path of the moon were the biggest indicators of good physics though. The shuttle makes a very plausible landing and the moon takes a very realistic path due to earths gravitational pull.