I think the answer is the reason for his absence is quite simple to understand.
The definition of a meter: Distance traversed in vacuum by light in 1/299,792,458 of a second.
According to this light travels 299,792,458 meters in a second. A nanosecond is 1 billionth of a second so light travels 299792458 / 1,000,000,000 meters in a nanosecond or 0.299792458m. (In a vacuum).
The meaning of the phrase "thou art wedded to calamity" is that you often have disaster around you.
Calamity means disaster.