If at speed of light, why can the eye see beginning/end of alpha-particle in a cloud chamber?

Question

In cloud chambers one can clearly see the beginning and direction/end of a path of an entering alpha particle. Why would this not appear simultaneous to the eye ? Is the particle being slowed by the collision with the vapor within a meter ? If the cloud chamber woud be much larger, would it come to halt ?
(Thanks, from a physics neophyte)

Answer 1

It should appear simultaneous. These particles are so light they decelerate quickly and don't travel at visible rates for any appreciable length of path. Perhaps you're seeing secondary indicators of direction, signs of decreasing speed/energy, like increasing curvature of charged particles (e.g., beta) in a magnetic field as they slow. The sense of uncharged alpha particle direction is a mystery, but possibly higher energy equates to more particles ionized along a given length of path so it appears better defined.

Answer 2

Alpha particles do not travel at the speed of light. Their speed depends on their energy which decrease with the number of collisions but it is always less than c.