There is, as we know, also the fact that atoms would never have been able to make contact with each other without an uncaused swerve -
This is a fact only within Epicurus' ancient physics. In modern physics, there are forces which attract particles to each other and thereby bent the straight paths expected by both Epicurus and Newton's first law. Once the particles are close enough, there are mechanisms which can bond them together.
- in a void, heavy atoms are not able to catch up to lighter ones and and therefore unable to cause a collision.
In Epicurus' ancient physics, the atoms move with constant speed irrespective of their weight.