This quick diagram gives you an idea of how I visualize the bending of space-time. Note that, if the bending were to curve the other direction (into the future), the equations would become irrational. The idea is that, within the confines of the metal room, that particular space-time (yes, it will, itself, be moving into the future along the time axis, but it’s a pretty short amount of time the two moving spots need to meet up) has been isolated and bent back on itself until it meets with the prior space-time.