What is the atomic swerve in Lucretius’s philosophy?

In the philosophy of Lucretius, the atomic swerve is a crucial concept used to explain the formation of the physical world and the existence of free will.

According to Lucretius’s atomism, all atoms would have moved downward through infinite space in a parallel, eternal fall, never colliding to form complex systems, had they not occasionally swerved by a minimal degree. These indeterminate, spontaneous motions serve two primary functions:1

• Cosmological: By causing atoms to collide, the swerve allows for the creation of an infinite plurality of worlds and the development of all material systems.1
• Ethical: The swerve interrupts the rigid, mechanical causality of the universe, thereby creating the necessary space for human free will.12

This concept distinguishes the Epicurean view from a strictly deterministic mechanical model, as it introduces an element of spontaneity into the movement of matter.2