Momentum

Momentum

Tonight, a swarm of crows
hurtling overhead, with the velocity
of sand flung from a beach towel.

As if in response, the train
arrived just then, and pulled open
its doors to reveal a people

dedicated to holding closed
their coats, their scarves. This train
is conductorless, carries itself

North or South, and stops
at the same speed in every station.
How to classify this momentum:

the elevated train, cables
and currents embracing passengers,
the eruption of crows in multiple?