Dance is the nature and Physics, from the greek Physis = "Nature", is the Science of Nature.
Gravity, friction, centre of gravity, angular momentum are physical concepts that dancers should know to don't fall from an 'aplomb' or a 'pirouette'.
Studying what happens when every small movement is executed discovers his "secrets" improving your body performance.
Why if you hold arms around your chest during a pirouette the speed increases?
To answer this question you need Physics knowledge.
When you know the 'why' of phenomena, which is the basis of the knowledge, you have perfect mastery of them.
The dancer must have mastered his/her performance and the phenomena that concern it so that he/she can govern own body to transmit the best sense of harmony.