Thought-experiments are fun. Let's go down to the beach. Let's pick up a small grain of sand (1mm) and pretend it's the size of 'our' whole solar system. How f

Thought-experiments are fun. Let's go down to the beach. Let's pick up a small grain of sand (1mm) and pretend it's the size of 'our' whole solar system. How far would we have to walk up the beach to get to the center of 'our' Milky Way?